Real-time Temporal Resolution Research Articles

An adaptive route choice model for integrated fixed and flexible transit systems

Over the past decade, there has been a surge of interest in the application of agent-based simulation models to evaluate flexible transit solutions characterized by different degrees of short-term flexibility in routing and scheduling. A central modelling decision in the development is how one chooses to represent the mode- and route-choices of travellers. The real-time adaptive behaviour of travellers is important to model in the presence of a flexible transit service, where the routing and scheduling of vehicles is highly dependent on supply-demand dynamics at a near real-time temporal resolution. We propose a utility-based transit route-choice model with representation of within-day adaptive travel behaviour and between-day learning where station-based fixed-transit, flexible-transit, and active-mode alternatives may be dynamically combined in a single path. To enable experimentation, this route-choice model is implemented within an agent-based dynamic public transit simulation framework. We first explore model properties in a choice between fixed- and flexible-transit modes for a toy network. The adaptive route choice framework is then applied to a case study based on a real-life branched transit service in Stockholm, Sweden. This case study illustrates level-of-service trade-offs, in terms of waiting times and in-vehicle times, between passenger groups and analyzes traveller mode choices within a mixed fixed- and flexible transit system. Results show that the proposed framework is capable of capturing dynamic route choices in mixed flexible and fixed transit systems and that the day-to-day learning model leads to stable fixed-flexible mode choices.

Towards Biomarkers for Autism Spectrum Disorder: Contributions of Magnetoencephalography (MEG).

There is no simple blood test for autism. Consequently, much attention has been paid to identifying noninvasive biomarkers using imaging (e.g., Magnetic resonance imaging, MRI) and electrophysiological (e.g., electroencephalography, EEG and magnetoencephalography, MEG) methods. While, in general, these lack direct biological specificity, they can (in principle) provide a useful tool, or suite of tools, for diagnostic, prognostic, stratification, and response monitoring purposes.This chapter focuses on the pursuit of biomarkers using magnetoencephalography (MEG). While closely related to the more common electroencephalography (EEG), MEG offers some unique characteristics (such as improved spatial resolution, in combination with real-time temporal resolution and spectral discrimination), that might be considered impactful in the pursuit of biomarkers.Given the widely-acknowledged heterogeneity of ASD ("if you've seen one child with autism, then you've seen one child with autism"), the tide of research is perhaps shifting away from diagnostic biomarkers toward biomarkers that can help stratify patients according to some similarity in biological basis, etiology, or pathway. This approach, somewhat pragmatic, may be of benefit when designing and conducting clinical trials of putative therapeutics, or when optimally designing behavioral supports (when "therapy" may not be indicated).Ultimately, MEG-derived biomarkers, however advantageous in themselves, may likely find a place as reference in the prioritization and roll-out of candidate biomarkers established using other modalities, more accessible and available to the global community.

Audomni: Super-Scale Sensory Supplementation to Increase the Mobility of Blind and Low-Vision Individuals-A Pilot Study.

Blindness and low vision have severe effects on individuals' quality of life and socioeconomic cost; a main contributor of which is a prevalent and acutely decreased mobility level. To alleviate this, numerous technological solutions have been proposed in the last 70 years; however, none has become widespread. In this paper, we introduce the vision-to-audio, super-scale sensory substitution/supplementation device Audomni; we address the field-encompassing issues of ill-motivated and overabundant test methodologies and metrics; and we utilize our proposed Desire of Use model to evaluate proposed pilot user tests, their results, and Audomni itself. Audomni holds a spatial resolution of 80 x 60 pixels at ~1.2° angular resolution and close to real-time temporal resolution, outdoor-viable technology, and several novel differentiation methods. The tests indicated that Audomni has a low learning curve, and several key mobility subtasks were accomplished; however, the tests would benefit from higher real-life motivation and data collection affordability. Audomni shows promise to be a viable mobility device - with some addressable issues. Employing Desire of Use to design future tests should provide both high real-life motivation and relevance to them. As far as we know, Audomni features the greatest information conveyance rate in the field, yet seems to offer comprehensible and fairly intuitive sonification; this work is also the first to utilize Desire of Use as a tool to evaluate user tests, a device, and to lay out an overarching project aim.

Direct Visualization of Lipoprotein Mediated Cholesterol Transport at the Phospholipid Bilayer Interface

It is still unclear how lipids are removed from the circulation and transferred from lipoproteins– the main carriers of cholesterol in the blood stream – to cells. Low density Lipoprotein (LDL)-uptake is facilitated mainly via receptor-mediated endocytosis in clathrin-coated pits but can also deliver its lipid cargo by selective transfer without degradation of the LDL particle. Whereas, High Density Lipoprotein (HDL) particles are captured from the blood stream by the corresponding receptor - the subsequent lipid-transfer process, however, is highly speculative. Here we used high-end techniques, namely combined atomic force (AFM) and single molecule fluorescence microscopy together with high speed AFM (HS-AFM) and fluorescence cross correlation spectroscopy (FCCS), to address the different transfer behaviour of lipids out of an LDL or HDL particle into a supported lipid membrane and their interaction kinetics. Combined force and single molecule fluorescence microscopy allowed us to directly monitor the transfer process of amphiphilic fluorescent probe lipids from lipoprotein particles to the lipid bilayer upon contact and their integration into the lipid bilayer was seen. FCCS experiments indicate that Cholesterol was freely mobile in the GUV membrane, additionally two color FCS revealed the absence of co-diffusion of the two species, indicating that cargo was transferred and separated from the particle. With the aid of HS-AFM we are able to achieve nanoscale spatial resolution together with real-time temporal resolution. Interestingly, on mica-supported DOPC membrane LDL in contrast to HDL was strongly interacting with the surface beneath by repetitive fusion and release. Taken together, in synthetic membranes, particle contact and incorporation into the lipid bilayer are sufficient requirements for cargo delivery. Whereby, the interaction kinetics and the integration of hydrophobic lipoprotein moieties in the core of the lipid bilayer strongly depends on the lipoprotein species.

Electron-beam induced synthesis of nanostructures: a review.

As the success of nanostructures grows in modern society so does the importance of our ability to control their synthesis in precise manners, often with atomic precision as this can directly affect the final properties of the nanostructures. Hence it is crucial to have both deep insight, ideally with real-time temporal resolution, and precise control during the fabrication of nanomaterials. Transmission electron microscopy offers these attributes potentially providing atomic resolution with near real time temporal resolution. In addition, one can fabricate nanostructures in situ in a TEM. This can be achieved with the use of environmental electron microscopes and/or specialized specimen holders. A rather simpler and rapidly growing approach is to take advantage of the imaging electron beam as a tool for in situ reactions. This is possible because there is a wealth of electron specimen interactions, which, when implemented under controlled conditions, enable different approaches to fabricate nanostructures. Moreover, when using the electron beam to drive reactions no specialized specimen holders or peripheral equipment is required. This review is dedicated to explore the body of work available on electron-beam induced synthesis techniques with in situ capabilities. Particular emphasis is placed on the electron beam-induced synthesis of nanostructures conducted inside a TEM, viz. the e-beam is the sole (or primary) agent triggering and driving the synthesis process.

Chemically-selective imaging of brain structures with CARS microscopy

We demonstrate the use of coherent anti-Stokes Raman scattering (CARS) microscopy to image brain structure and pathology ex vivo. Although non-invasive clinical brain imaging with CT, MRI and PET has transformed the diagnosis of neurologic disease, definitive pre-operative distinction of neoplastic and benign pathologies remains elusive. Definitive diagnosis still requires brain biopsy in a significant number of cases. CARS microscopy, a nonlinear, vibrationally-sensitive technique, is capable of high-sensitivity chemically-selective three-dimensional imaging without exogenous labeling agents. Like MRI, CARS can be tuned to provide a wide variety of possible tissue contrasts, but with sub-cellular spatial resolution and near real time temporal resolution. These attributes make CARS an ideal technique for fast, minimally invasive, non-destructive, molecularly specific intraoperative optical diagnosis of brain lesions. This promises significant clinical benefit to neurosurgical patients by providing definitive diagnosis of neoplasia prior to tissue biopsy or resection. CARS imaging can augment the diagnostic accuracy of traditional frozen section histopathology in needle biopsy and dynamically define the margins of tumor resection during brain surgery. This report illustrates the feasibility of in vivo CARS vibrational histology as a clinical tool for neuropathological diagnosis by demonstrating the use of CARS microscopy in identifying normal brain structures and primary glioma in fresh unfixed and unstained ex vivo brain tissue.

Dynamic magnetic resonance imaging of vocal cord closure during deglutition

Background & Aims : Vocal cord closure is instrumental in airway protection during deglutition. Conventional imaging of vocal cord closure and reopening during deglutition requires invasive and nonphysiological methods. The aim of this study was to characterize the biomechanical properties of normal vocal cord adduction/abduction during deglutition using echoplanar magnetic resonance imaging, a technique that has the capability of imaging soft-tissue motion with real-time temporal resolution. Methods : The movements of laryngeal and vocal cord structures during swallowing were determined in 11 normal volunteers by single slice and axially reformatted multislice coronal echoplanar images. Results : During swallowing, the larynx ascended to peak elevation, maintained peak elevation for a discrete interval, and descended to its resting position. Vocal cord adduction occurred with a symmetric tent-like configuration at the midpoint of maximal laryngeal elevation, whereas vocal cord abduction occurred at the midpoint of laryngeal descent. Spatial analysis of vocal cord configuration during adduction determined that the vocal cords attained an initial parallel configuration during ascent, followed by closure at peak laryngeal elevation. Conclusions : These results show that the vocal cords adduct and abduct synchronously with laryngeal ascent and descent, respectively, during deglutition. Echoplanar magnetic resonance imaging constitutes a novel tool used to assess clinical abnormalities of deglutitive laryngeal function.

Advances in brain tumor imaging

Scientists have taken advantage of the powerful imaging capability of computed tomographic and magnetic resonance (MR) scanners to analyze brain tumor morphology in vivo. Recently, the development of functional MR imaging techniques have added the ability to noninvasively examine brain tumor function and physiology with near real-time temporal resolution, and spatial resolution approaching that of anatomic images. This advance allows the study of cerebral blood volume, cerebral blood flow, and stimulated cortical activity, which have traditionally been within the domain of positron emission tomography (PET) research. PET research on brain tumors continues mainly with research into glycolytic rates and comparison with proton MR spectroscopic lactate data. These comparisons are facilitated by the refinement of two-dimensional MR spectroscopic techniques, which provide comparable spatial resolution to that of PET. On a more clinical note, several prospective studies involving the MR contrast agent gadolinium have been carried out, specifically those optimizing the timing of contrast-enhanced postoperative MR scans after resection of glioblastomas, using triple-dose contrast to increase sensitivity to brain metastases, and using contrast-enhanced MR imaging to study the efficacy of embolization in meningiomas.