Haptic collision handling for simulation of transnasal surgery

Simulation of endoscopic navigation in the narrow nasal cavity poses important challenges to the computation of adequate and near‐realistic collision response and haptic feedback because extensive multidirectional contact and massive tissue deformations are inevitable. We present a virtual coupling algorithm that provides stable collision response as well as intuitive and smooth haptic interaction in all phases of the simulation. In each iteration, continuous collision detection between the point shell representing the surface of the virtual patient anatomy and the endoscope, represented by a cylinder, is performed. This allows for rolling back the instrument movement to the point in time the first collision occurred. Subsequently, a relaxation process locally optimizes the position and orientation of the instrument. A novel method of applying contact forces to colliding tissues and thus triggering appropriate deformations improves the fluency of navigation. This paper describes the algorithm and presents experimental results. © Her Majesty the Queen in Right of Canada 2012. Reproduced with the permission of the Minister of Medical Devices, National Research Council Canada.     

Urban Responses to Climate Change in Latin America: Reasons,Challenges and Opportunities

Cities in Latin America have a crucial role to play in climate change. Urban areas are the main emitters of greenhouse gases, while being vulnerable to severe weather conditions such as floods, heat waves and tropical storms that environmental shifts are expected to trigger. Patricia Romero-Lankao outlines the background to greenhouse gas emissions and climate change, while highlighting how development in Latin America presents unique opportunities for mitigating potential damage to the environment. Copyright © 2011 John Wiley & Sons, Ltd.     

Printability of Methacrylated Gelatin upon Inclusion of a Chloride Salt and Hydroxyapatite Nano‐Particles

3D biomaterial printing requires an ink to have suitable printability characteristics, as well as creating a final construct of controllable swelling and stiffness. To tune such properties, the impact of adding different levels of chloride salts (NaCl and CaCl₂) and hydroxyapatite nano‐particles (nHA) to a highly concentrated and photo‐crosslinkable methacrylated gelatin (GelMA) is investigated. By adding up to 100 mm CaCl₂ or 1.11 m NaCl, the GelMA viscosity decreases from that of control GelMA (no salt). Interestingly, a 25G needle and strong photo‐polymerization kinetics are able to overcome the low viscosity of the 50CaG ink during printing. Adding further CaCl₂ increases GelMA viscosity, while decreasing both the swelling and dynamic modulus of the UV‐cured construct observed in water. As all UV‐cured constructs have a dynamic modulus greater than 1 MPa, this novel system is able to match the dynamic modulus of articular cartilage—a feat not previously reported for a GelMA‐based system. Lastly, nHA inclusion improves ink printability, as well as decreases swelling and increases dynamic modulus of the final construct. Overall, this study leads to the successful development of a new advanced functional ink which will be beneficial in the 3D printing of biomaterials toward tissue engineering applications.     

Attentional modulation of the P50 suppression deficit in recent-onset and chronic schizophrenia.

Schizophrenia is associated with deficits in P50 suppression to the second stimulus in a pair, a process often conceptualized as a preattentive index of sensory gating. This study assessed the malleability of the deficit by determining whether early attentional control can influence P50 gating across different phases of schizophrenia. Participants included 28 patients in the recent-onset (n = 16) or chronic (n = 12) phase of illness and 28 healthy comparison subjects. During the standard paradigm, chronic schizophrenia patients exhibited impaired P50 suppression relative to healthy subjects, whereas recent-onset schizophrenia patients were intermediate. Directing voluntary attention toward the initial stimulus yielded substantial improvements in the P50 ratio; recent-onset schizophrenia patients achieved ratio scores comparable to those of healthy participants, whereas chronic patients also improved and could no longer be distinguished clearly from the healthy comparison sample. Directing attention toward the second stimulus enhanced P50 amplitude to the second stimulus across groups, possibly because activation of the inhibitory mechanism was overridden or circumvented by task demands. Thus, P50 suppression may be primarily preattentive under standard conditions, but manipulation of early attention can exert a modulatory influence on P50, indicating that the suppression deficit is malleable in schizophrenia without pharmacological agents. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Efficacy of supplemental phonics-based instruction for low-skilled kindergarteners in the context of language minority status and classroom phonics instruction.

This study tested the efficacy of supplemental phonics instruction for 84 low-skilled language minority (LM) kindergarteners and 64 non-LM kindergarteners at 10 urban public schools. Paraeducators were trained to provide the 18-week (January–May) intervention. Students performing in the bottom half of their classroom language group (LM and non-LM) were randomly assigned either to individual supplemental instruction (treatment) or to classroom instruction only (control). Irrespective of their language status, treatment students (n = 67) significantly outperformed controls (n = 81) at posttest in alphabetics, word reading, spelling, passage reading fluency, and comprehension (average treatment d = 0.83); nevertheless, LM students tended to have lower posttest performance than non-LM students (average LM d = ?0.30) and were significantly less responsive to treatment on word reading. When we examined the contribution of classroom phonics time to student outcomes, we found that the treatment effect on spelling was greater for students in lower phonics classrooms, whereas the treatment effect on comprehension was greater for those in higher phonics classrooms. Finally, when we examined LM students alone, we found that pretest English receptive vocabulary positively predicted most posttests and interacted with treatment only on phonological awareness. In general, pretest vocabulary did not moderate kindergarten LM treatment response. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Fluid cognitive ability is associated with greater exposure and smaller reactions to daily stressors.

The authors of this study investigated whether fluid cognitive ability predicts exposure and emotional reactivity to daily stressors. A national sample of adults from the Midlife in the United States study and the National Study of Daily Experiences (N = 1,202) who had a mean age of 57 years (SD = 12; 56% women, 44% men) completed positive and negative mood reports as well as a stressor diary on 8 consecutive evenings via telephone. Participants also completed a telephone-based battery of tests measuring fluid cognitive ability. Higher levels of fluid cognitive ability were associated with greater exposure to work- and home-related overload stressors. Possessing higher levels of fluid cognitive ability was associated with smaller stressor-related increases in negative mood, primarily for interpersonal tensions and network stressors, and smaller stressor-related decreases in positive mood for interpersonal tensions. Furthermore, fluid cognitive ability was unrelated to subjective severity ratings of the stressors reported. Discussion focuses on the role of fluid cognitive ability in daily stress processes. (PsycINFO Database Record (c) 2010 APA, all rights reserved)