Markerless navigation system for orthopaedic knee surgery: a proof of concept study

Current computer-assisted surgical navigation systems mainly rely on optical markers screwed into the bone for anatomy tracking. The insertion of these percutaneous markers increases operating complexity and causes additional harm to the patient. A markerless tracking and registration algorithm has recently been proposed to avoid anatomical markers for knee surgery. The femur points were directly segmented from the recorded RGBD scene by a neural network and then registered to a pre-scanned femur model for the real-time pose. However, in a practical setup such a method can produce unreliable registration results, especially in rotation. Furthermore, its potential application in surgical navigation has not been demonstrated. In this paper, we first improved markerless registration accuracy by adopting a bounded-ICP (BICP) technique, where an estimate of the remote hip centre, acquired also in a markerless way, was employed to constrain distal femur alignment. Then, a proof-of-concept markerless navigation system was proposed to assist in typical knee drilling tasks. Two example setups for global anchoring were proposed and tested on a phantom leg. Our BICP-based markerless tracking and registration method has better angular accuracy and stability than the original method, bringing our straightforward, less invasive markerless navigation approach one step closer to clinical application. According to user tests, our proposed optically anchored navigation system achieves comparable accuracy with the state-of-the-art (3.64± 1.49 mm in position and 2.13±0.81° in orientation). Conversely, our visually anchored, optical tracker-free setup has a lower accuracy (5.86± 1.63 mm in position and 4.18±1.44° in orientation), but is more cost-effective and flexible in the operating room

The usability canary in the security coal mine: A cognitive framework for evaluation and design of usable authentication solutions

Over the past 15 years, researchers have identified an increasing number of security mechanisms that are so unus- able that the intended users either circumvent them or give up on a service rather than suffer the security. With hindsight, the reasons can be identified easily enough: either the security task itself is too cumbersome and/or time-consuming, or it creates high friction with the users’ primary task. The aim of the research presented here is to equip designers who select and implement security mechanisms with a method for identifying the “best fit” security mechanism at the design stage. Since many usability problems have been identified with authentication, we focus on “best fit” authentication, and present a framework that allows security designers not only to model the workload associated with a particular authentication method, but more importantly to model it in the context of the user’s primary task. We draw on results from cognitive psychology to create a method that allows a designer to understand the impact of a particular authentication method on user productivity and satisfaction. In a validation study using a physical mockup of an airline check-in kiosk, we demonstrate that the model can predict user performance and satisfaction. Furthermore, design experts suggested personalized order recommendations which were similar to our model’s predictions. Our model is the first that supports identification of a holistic fit between the task of user authentication and the context in which it is performed. When applied to new systems, we believe it will help designers understand the usability impact of their security choices and thus develop solutions that maximize both.The Cambridge authors are grateful to the European Research Council for funding this research through grant StG 307224 (Pico). The UCL authors are grateful to the Engineering and Physical Sciences Research Council for funding this research through grant #EP/K033476/1

Whole Atmosphere Climate Change: Dependence on Solar Activity

We conducted global simulations of temperature change due to anthropogenic trace gas emissions, which extended from the surface, through the thermosphere and ionosphere, to the exobase. These simulations were done under solar maximum conditions, in order to compare the effect of the solar cycle on global change to previous work using solar minimum conditions. The Whole Atmosphere Community Climate Model‐eXtended was employed in this study. As in previous work, lower atmosphere warming, due to increasing anthropogenic gases, is accompanied by upper atmosphere cooling, starting in the lower stratosphere, and becoming dramatic, almost 2 K per decade for the global mean annual mean, in the thermosphere. This thermospheric cooling, and consequent reduction in density, is less than the almost 3 K per decade for solar minimum conditions calculated in previous simulations. This dependence of global change on solar activity conditions is due to solar‐driven increases in radiationally active gases other than carbon dioxide, such as nitric oxide. An ancillary result of these and previous simulations is an estimate of the solar cycle effect on temperatures as a function of altitude. These simulations used modest, five‐member, ensembles, and measured sea surface temperatures rather than a fully coupled ocean model, so any solar cycle effects were not statistically significant in the lower troposphere. Temperature change from solar minimum to maximum increased from near zero at the tropopause to about 1 K at the stratopause, to approximately 500 K in the upper thermosphere, commensurate with the empirical evidence, and previous numerical models

Pilot-aided Pump Dithering Removal in Degenerate FWM-based Optical Phase Conjugation Systems with Higher-order QAM

A pump dithering removal algorithm, based on pilot sequence-aided DSP, is proposed and experimentally validated in dual polarization 64 QAM optical phase conjugation system. A 4.2 dB SNR improvement was observed due to the SBS suppression

Superderivations for Modular Graded Lie Superalgebras of Cartan-type

Superderivations for the eight families of finite or infinite dimensional graded Lie superalgebras of Cartan-type over a field of characteristic $p>3$ are completely determined by a uniform approach: The infinite dimensional case is reduced to the finite dimensional case and the latter is further reduced to the restrictedness case, which proves to be far more manageable. In particular, the outer superderivation algebras of those Lie superalgebras are completely determined

Identification of furfural resistant strains of Saccharomyces cerevisiae and Saccharomyces paradoxus from a collection of environmental and industrial isolates

Background Fermentation of bioethanol using lignocellulosic biomass as a raw material provides a sustainable alternative to current biofuel production methods by utilising waste food streams as raw material. Before lignocellulose can be fermented it requires physical, chemical and enzymatic treatment in order to release monosaccharides, a process that causes the chemical transformation of glucose and xylose into the cyclic aldehydes furfural and hydroxyfurfural. These furan compounds are potent inhibitors of Saccharomyces fermentation, and consequently furfural tolerant strains of Saccharomyces are required for lignocellulosic fermentation. Results This study investigated yeast tolerance to furfural and hydroxyfurfural using a collection of 71 environmental and industrial isolates of the baker’s yeast Saccharomyces cerevisiae and its closest relative Saccharomyces paradoxus. The Saccharomyces strains were initially screened for growth on media containing 100 mM glucose and 1.5 mg ml-1 furfural. Five strains were identified that showed a significant tolerance to growth in the presence of furfural and these were then screened for growth and ethanol production in the presence of increasing amounts (0.1-4 mg ml-1) of furfural. Conclusions Of the five furfural tolerant strains S. cerevisiae NCYC 3451 displayed the greatest furfural resistance, and was able to grow in the presence of up to 3.0 mg ml-1 furfural. Furthermore, ethanol production in this strain did not appear to be inhibited by furfural, with the highest ethanol yield observed at 3.0 mg ml-1 furfural. Although furfural resistance was not found to be a trait specific to any one particular lineage or population, three of the strains were isolated from environments where they might be continually exposed to low levels of furfural through the on-going natural degradation of lignocelluloses, and would therefore develop elevated levels of resistance to these furan compounds. Thus these strains represent good candidates for future studies of genetic variation relevant to understanding and manipulating furfural resistance and in the development of tolerant ethanologenic yeast strains for use in bioethanol production from lignocellulose processing

Impact of neoadjuvant treatment on total mesorectal excision for ultra-low rectal cancers

<p>Abstract</p> <p>Background</p> <p>This study reviewed the impact of pre-operative chemoradiotherapy or post-operative chemotherapy and/or radiotherapy on total mesorectal excision (TME) for ultralow rectal cancers that required either low anterior resection with peranal coloanal anastomosis or abdomino-perineal resection (APR). We examined surgical complications, local recurrence and survival.</p> <p>Methods</p> <p>Of the 1270 patients who underwent radical resection for rectal cancer from 1994 till 2007, 180 with tumors within 4 cm with either peranal coloanal anastomosis or APR were analyzed. Patients were compared in groups that had surgery only (Group A), pre-operative chemoradiotherapy (Group B), and post-operative therapy (Group C).</p> <p>Results</p> <p>There were 115 males and the mean age was 65.43 years (range 30-89). APR was performed in 134 patients while 46 had a sphincter-preserving resection with peranal coloanal anastomosis. The mean follow-up period was 52.98 months (range: 0.57 to 178.9). There were 69, 58 and 53 patients in Groups A, B, and C, respectively. Nine patients in Group B could go on to have sphincter-saving rectal resection. The overall peri-operative complication rate was 43.4% in Group A vs. 29.3% in Group B vs. 39.6% in Group C, respectively. The local recurrence rate was significantly lower in Group B (8.6.9% vs. 21.7% in Group A vs. 33.9% in Group C) <it>p < 0.05</it>. The 5-year cancer-specific survival rates for Group A was 49.3%, Group B was 69.9% and Group C was 38.8% (<it>p </it>= 0.14).</p> <p>Conclusion</p> <p>Pre-operative chemoradiation in low rectal cancer is not associated with a higher incidence of peri-operative complications and its benefits may include reduction local recurrence.</p

Thermodynamical Consistent Modeling and Analysis of Nematic Liquid Crystal Flows

The general Ericksen-Leslie system for the flow of nematic liquid crystals is reconsidered in the non-isothermal case aiming for thermodynamically consistent models. The non-isothermal model is then investigated analytically. A fairly complete dynamic theory is developed by analyzing these systems as quasilinear parabolic evolution equations in an $L^p-L^q$-setting. First, the existence of a unique, local strong solution is proved. It is then shown that this solution extends to a global strong solution provided the initial data are close to an equilibrium or the solution is eventually bounded in the natural norm of the underlying state space. In these cases, the solution converges exponentially to an equilibrium in the natural state manifold