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Concept: Point

251

Background Continuous-flow left ventricular assist systems increase the rate of survival among patients with advanced heart failure but are associated with the development of pump thrombosis. We investigated the effects of a new magnetically levitated centrifugal continuous-flow pump that was engineered to avert thrombosis. Methods We randomly assigned patients with advanced heart failure to receive either the new centrifugal continuous-flow pump or a commercially available axial continuous-flow pump. Patients could be enrolled irrespective of the intended goal of pump support (bridge to transplantation or destination therapy). The primary end point was a composite of survival free of disabling stroke (with disabling stroke indicated by a modified Rankin score >3; scores range from 0 to 6, with higher scores indicating more severe disability) or survival free of reoperation to replace or remove the device at 6 months after implantation. The trial was powered for noninferiority testing of the primary end point (noninferiority margin, -10 percentage points). Results Of 294 patients, 152 were assigned to the centrifugal-flow pump group and 142 to the axial-flow pump group. In the intention-to-treat population, the primary end point occurred in 131 patients (86.2%) in the centrifugal-flow pump group and in 109 (76.8%) in the axial-flow pump group (absolute difference, 9.4 percentage points; 95% lower confidence boundary, -2.1 [P<0.001 for noninferiority]; hazard ratio, 0.55; 95% confidence interval [CI], 0.32 to 0.95 [two-tailed P=0.04 for superiority]). There were no significant between-group differences in the rates of death or disabling stroke, but reoperation for pump malfunction was less frequent in the centrifugal-flow pump group than in the axial-flow pump group (1 [0.7%] vs. 11 [7.7%]; hazard ratio, 0.08; 95% CI, 0.01 to 0.60; P=0.002). Suspected or confirmed pump thrombosis occurred in no patients in the centrifugal-flow pump group and in 14 patients (10.1%) in the axial-flow pump group. Conclusions Among patients with advanced heart failure, implantation of a fully magnetically levitated centrifugal-flow pump was associated with better outcomes at 6 months than was implantation of an axial-flow pump, primarily because of the lower rate of reoperation for pump malfunction. (Funded by St. Jude Medical; MOMENTUM 3 ClinicalTrials.gov number, NCT02224755 .).

Concepts: Blood, Hypertension, Cardiology, Heart, Confidence interval, Anticoagulant, Disability, Point

145

Scan matching, an approach to recover the relative position and orientation of two laser scans, is a very important technique for indoor positioning and indoor modeling. The iterative closest point (ICP) algorithm and its variants are the most well-known techniques for such a problem. However, ICP algorithms rely highly on the initial guess of the relative transformation, which will reduce its power for practical applications. In this paper, an initial-free 2D laser scan matching method based on point and line features is proposed. We carefully design a framework for the detection of point and line feature correspondences. First, distinct feature points are detected based on an extended 1D SIFT, and line features are extracted via a modified Split-and-Merge algorithm. In this stage, we also give an effective strategy for discarding unreliable features. The point and line features are then described by a distance histogram; the pairs achieving best matching scores are accepted as potential correct correspondences. The histogram cluster technique is adapted to filter outliers and provide an accurate initial value of the rigid transformation. We also proposed a new relative pose estimation method that is robust to outliers. We use the lq-norm (0 < q < 1) metric in this approach, in contrast to classic optimization methods whose cost function is based on the l₂-norm of residuals. Extensive experiments on real data demonstrate that the proposed method is almost as accurate as ICPs and is initial free. We also show that our scan matching method can be integrated into a simultaneous localization and mapping (SLAM) system for indoor mapping.

Concepts: Algorithm, Euclidean geometry, Features new to Windows Vista, Point, Positioning, The Point, Simultaneous localization and mapping, Iterative Closest Point

83

Background A leadless intracardiac transcatheter pacing system has been designed to avoid the need for a pacemaker pocket and transvenous lead. Methods In a prospective multicenter study without controls, a transcatheter pacemaker was implanted in patients who had guideline-based indications for ventricular pacing. The analysis of the primary end points began when 300 patients reached 6 months of follow-up. The primary safety end point was freedom from system-related or procedure-related major complications. The primary efficacy end point was the percentage of patients with low and stable pacing capture thresholds at 6 months (≤2.0 V at a pulse width of 0.24 msec and an increase of ≤1.5 V from the time of implantation). The safety and efficacy end points were evaluated against performance goals (based on historical data) of 83% and 80%, respectively. We also performed a post hoc analysis in which the rates of major complications were compared with those in a control cohort of 2667 patients with transvenous pacemakers from six previously published studies. Results The device was successfully implanted in 719 of 725 patients (99.2%). The Kaplan-Meier estimate of the rate of the primary safety end point was 96.0% (95% confidence interval [CI], 93.9 to 97.3; P<0.001 for the comparison with the safety performance goal of 83%); there were 28 major complications in 25 of 725 patients, and no dislodgements. The rate of the primary efficacy end point was 98.3% (95% CI, 96.1 to 99.5; P<0.001 for the comparison with the efficacy performance goal of 80%) among 292 of 297 patients with paired 6-month data. Although there were 28 major complications in 25 patients, patients with transcatheter pacemakers had significantly fewer major complications than did the control patients (hazard ratio, 0.49; 95% CI, 0.33 to 0.75; P=0.001). Conclusions In this historical comparison study, the transcatheter pacemaker met the prespecified safety and efficacy goals; it had a safety profile similar to that of a transvenous system while providing low and stable pacing thresholds. (Funded by Medtronic; Micra Transcatheter Pacing Study ClinicalTrials.gov number, NCT02004873 .).

Concepts: Implantable cardioverter-defibrillator, Point, Artificial pacemaker, Post-hoc analysis, Transcutaneous pacing, Goal, Medtronic, Earl Bakken

49

Background Mechanical circulatory support with a left ventricular assist device (LVAD) is an established treatment for patients with advanced heart failure. We compared a newer LVAD design (a small intrapericardial centrifugal-flow device) against existing technology (a commercially available axial-flow device) in patients with advanced heart failure who were ineligible for heart transplantation. Methods We conducted a multicenter randomized trial involving 446 patients who were assigned, in a 2:1 ratio, to the study (centrifugal-flow) device or the control (axial-flow) device. Adults who met contemporary criteria for LVAD implantation for permanent use were eligible to participate in the trial. The primary end point was survival at 2 years free from disabling stroke or device removal for malfunction or failure. The trial was powered to show noninferiority with a margin of 15 percentage points. Results The intention-to treat-population included 297 participants assigned to the study device and 148 participants assigned to the control device. The primary end point was achieved in 164 patients in the study group and 85 patients in the control group. The analysis of the primary end point showed noninferiority of the study device relative to the control device (estimated success rates, 55.4% and 59.1%, respectively, calculated by the Weibull model; absolute difference, 3.7 percentage points; 95% upper confidence limit, 12.56 percentage points; P=0.01 for noninferiority). More patients in the control group than in the study group had device malfunction or device failure requiring replacement (16.2% vs. 8.8%), and more patients in the study group had strokes (29.7% vs. 12.1%). Quality of life and functional capacity improved to a similar degree in the two groups. Conclusions In this trial involving patients with advanced heart failure who were ineligible for heart transplantation, a small, intrapericardial, centrifugal-flow LVAD was found to be noninferior to an axial-flow LVAD with respect to survival free from disabling stroke or device removal for malfunction or failure. (Funded by HeartWare; ENDURANCE ClinicalTrials.gov number, NCT01166347 .).

Concepts: Scientific control, Blood, Cardiology, Heart, The Trial, Ventricular assist device, Point, Weibull distribution

42

In contrast to most other sensory modalities, the basic perceptual dimensions of olfaction remain unclear. Here, we use non-negative matrix factorization (NMF) - a dimensionality reduction technique - to uncover structure in a panel of odor profiles, with each odor defined as a point in multi-dimensional descriptor space. The properties of NMF are favorable for the analysis of such lexical and perceptual data, and lead to a high-dimensional account of odor space. We further provide evidence that odor dimensions apply categorically. That is, odor space is not occupied homogenously, but rather in a discrete and intrinsically clustered manner. We discuss the potential implications of these results for the neural coding of odors, as well as for developing classifiers on larger datasets that may be useful for predicting perceptual qualities from chemical structures.

Concepts: Dimension, Euclidean space, Vector space, Space, Spacetime, Linear algebra, Real number, Point

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We report the direct measurement of the Dirac point, the Fermi level, and the work function of graphene by performing internal photoemission measurements on a graphene/SiO2/Si structure with a unique optical-cavity enhanced test structure. A complete electronic band alignment at the graphene/SiO2/Si interfaces is accurately established. The observation of enhanced photoemission from a one-atom thick graphene layer was possible by taking advantage of the constructive optical interference in the SiO2 cavity. The photoemission yield was found to follow the well-known linear density-of-states dispersion in the vicinity of the Dirac point. At the flat band condition, the Fermi level was extracted and found to reside 3.3 eV ± 0.05 eV below the bottom of the SiO2 conduction band. When combined with the shift of the Fermi level from the Dirac point we are able to ascertain the position of the Dirac point at 3.6 eV ± 0.05 eV with respect to the bottom of the SiO2 conduction band edge, yielding a work function of 4.5 eV ± 0.05 eV which is in an excellent agreement with theory. The accurate determination of the work function of graphene is of significant importance to the engineering of graphene-based devices and the measurement technique we have advanced in this letter will have significant impact on numerous applications for emerging graphene-like 2-Dimensional material systems.

Concepts: Condensed matter physics, Semiconductor, Enrico Fermi, Object-oriented programming, Point, Work function, Fermi energy, Fermi level

27

SUMMARY: For testing stationarity of a given spatial point pattern, Guan (2008) proposed a model-free statistic, based on the deviations between observed and expected counts of points in expanding regions within the sampling window. This article extends his method to a general class of statistics by incorporating also such information when points are projected to the axes and by allowing different ways to construct regions in which the deviations are considered. The limiting distributions of the new statistics can be expressed in terms of integrals of a Brownian sheet and hence asymptotic critical values can be approximated. A simulation study shows that the new tests are always more powerful than that of Guan. When applied to the longleaf pine data where Guan’s test gave an inconclusive answer, the new tests indicate a clear rejection of the stationarity hypothesis.

Concepts: Scientific method, Statistics, Mathematics, Sociology, Point

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We investigated puppies' responsiveness to hand points differing in salience. Experiment 1 compared performance of younger (8 weeks old) and older (12 weeks) shelter pups in following pointing gestures. We hypothesized that older puppies would show better performance. Both groups followed the easy and moderate but not the difficult pointing cues. Surprisingly, the younger pups outperformed the older ones in following the moderate and difficult points. Investigation of subjects' backgrounds revealed that significantly more younger pups had experience living in human homes than did the older pups. Thus, we conducted a second experiment to isolate the variable experience. We collected additional data from older pet pups living in human homes on the same three point types and compared their performance with the shelter pups from Experiment 1. The pups living in homes accurately followed all three pointing cues. When comparing both experienced groups, the older pet pups outperformed the younger shelter ones, as predicted. When comparing the two same-age groups differing in background experience, the pups living in homes outperformed the shelter pups. A significant correlation between experience with humans and success in following less salient cues was found. The importance of ontogenetic learning in puppies' responsiveness to certain human social cues is discussed.

Concepts: English-language films, Empiricism, Hypothesis, Dog, Point, Pointing, The Shelter, Puppy

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Pointing gestures are a vital aspect of human communication. Nevertheless, observers consistently fail to determine the exact location to which another person points when that location lies in the distance. Here we explore the reasons for this misunderstanding. Humans usually point by extending the arm and finger. We show that observer’s interpret these gestures by nonlinear extrapolation of the pointer’s arm-finger line. The nonlinearity can be adequately described as the Bayesian-optimal integration of a linear extrapolation of the arm-finger line and observers' prior assumptions about likely referent positions. Surprisingly, the spatial rule describing the interpretation of pointing gestures differed from the rules describing the production of these gestures. In the latter case, the eye, index finger, and referent were aligned. We show that the differences in the production and interpretation of pointing gestures accounts for the systematic spatial misunderstanding of pointing gestures to distant referents. No evidence was found for the hypotheses that action-related processes are involved in the perception of pointing gestures. How participants interpreted pointing gestures was independent of how they produce these gestures and whether they had practiced pointing movements before. By contrast, both the production and interpretation seem to be primarily determined by salient visual cues. (PsycINFO Database Record

Concepts: Interpretation, Finger, Hand, Index finger, Point, Pointing, Language interpretation, Nonlinear system

19

Prion-like misfolding of superoxide dismutase 1 (SOD1) is associated with the disease ALS, but the mechanism of misfolding remains unclear, partly because misfolding is difficult to observe directly. Here we study the most misfolding-prone form of SOD1, reduced un-metallated monomers, using optical tweezers to measure unfolding and refolding of single molecules. We find that the folding is more complex than suspected, resolving numerous previously undetected intermediate states consistent with the formation of individual β-strands in the native structure. We identify a stable core of the protein that unfolds last and refolds first, and directly observe several distinct misfolded states that branch off from the native folding pathways at specific points after the formation of the stable core. Partially folded intermediates thus play a crucial role mediating between native and non-native folding. These results suggest an explanation for SOD1’s propensity for prion-like misfolding and point to possible targets for therapeutic intervention.

Concepts: Superoxide dismutase, Protein folding, Amyotrophic lateral sclerosis, Intervention, Superoxide, Point, Single-molecule experiment, SOD1