Path Length Changes Research Articles

Micro-volume spectrophotometer with a slope spectroscopy technique

Ultraviolet–visible spectrophotometric analysis for nucleic acids and proteins is a widespread technique. For a quick and easy use and reduce the consumption of valuable samples, micro-volume spectrophotometer is developed. In the paper, the ultraviolet–visible spectrophotometer is newly presented based on the slope measurement technique, which allows the one sequence of detection to measure the concentration of micro-volume nucleic acids or proteins samples without blank measurement. Through the experiments, we proved that the concentration can be measured without reference measurement for micro-volume samples. Additionally, in order to determine the concentration of samples, only the optical path length change through the motor drive is required, therefore there is no need to know the absolute optical path length during measurement. Furthermore, we verified that our system can even measure higher concentration sample compared to commercialized tools.

Precise phase theory for accuracy improvement in a fiber probe interferometer for nanometric sensing, taking into account fiber coupling

In a single-mode-fiber probe type of interferometer, the effect of fiber coupling on the sensing performance is theoretically comprehensively investigated in order to analyze and improve the achievable sensing accuracy for nanometric sensing. In both direct and via-lens coupling schemes for the interferometer, the scale factors to deduce optical path length change from the measured phase are analytically and numerically examined in terms of deviation from the plane wave assumption of conventional use. It is manifested that the scale factor deviation is of considerable magnitude in the case of direct coupling, but, by the incorporation of suitable collimating optics for coupling, the degree of deviation can be drastically reduced to as small as typically 10 − 8 , supporting achievement of ultrahigh accuracy such as picometer in displacement sensing. The effect of reflector tilting is also addressed.

Impact of Extremity Manipulation on Postural Sway Characteristics: A Preliminary, Randomized Crossover Study

ObjectiveEvaluate multisegmental postural sway after upper- vs lower-extremity manipulation. MethodsParticipants were healthy volunteers (aged 21-40 years). Upper- or lower-extremity manipulations were delivered in a randomized crossover design. Postural assessments were made pre-post manipulation, in floor and rocker board conditions. Analysis included traditional balance measures of pathlength and range and sample entropy (SampEn) to examine the temporal structure of sway of the head, trunk, and surface. ResultsNo statistical changes in pathlength or sway range on the ground surface condition were observed. No increases in the amount of sway occurred in any condition. Chiropractic manipulation of either upper or lower extremities led to reductions in traditional measures of postural control on the rocker board. In the anteroposterior direction (sagittal plane), lower-extremity manipulation led to increased trunk SampEn while on the ground, and conversely a decreased SampEn while on the rocker board. In the mediolateral rocker board condition (frontal plane), manipulation elicited a change in SampEn that differed according to site of manipulation; upper-extremity manipulation increased SampEn, whereas lower-extremity manipulation reduced SampEn. ConclusionBoth upper- and lower-extremity manipulation influenced several measures of postural sway on both the ground and the rocker board. Lower-extremity manipulation improved the organization of sway at the trunk (anteroposterior direction) and the board (mediolateral direction). Given the reduction and reorganization of sway metrics seen in this study, we propose extending this line of research to the elderly who are at greatest risk of increased sway and falls.

Comparison of underwater gait training and overground gait training for improving the walking and balancing ability of patients with severe hemiplegic stroke: A randomized controlled pilot trial

BackgroundWalking training is an essential intervention to improve the function in stroke patients. However, only a limited number of gait training strategies are available for stroke patients with relatively severe disabilities. Research questionIs underwater gait training or overground gait training more effective in severe stroke patients? MethodsA total of 21 patients with severe hemiplegic stroke were randomly assigned to the experimental and control groups. All participants (n = 21) received 60-minute sessions of general physical therapy, 5 times a week for a period of 12 weeks. Additionally, the experimental and control groups underwent underwater and overground walking training, respectively, for 30 min twice times a week for 12 weeks. Postural assessment for stroke score, center of pressure path length and velocity, step time and step length difference, and walking velocity were measured before and after the 12-week training. ResultsBoth groups showed a significant decrease in the center of pressure path length and velocity after the intervention compared to the values before the intervention (p < .05). However, there was no significant difference in the center of pressure path length and velocity changes after training between the two groups (p > .05). In the walking variables, the step length difference changes after training between the two groups showed a significant difference (p < .05). In the experimental group, the step length difference increased after the intervention compared to that before the intervention (+4.55 cm), whereas that of the control group decreased (-1.25 cm). SignificanceIn severe stroke patients, underwater gait training can be effective for improving balancing ability, but it may be less effective on the improvement of gait function than overground walking.Clinical trial registration number: KCT0002587 (https://cris.nih.go.kr)

Real-Time Hybrid Navigation System-Based Path Planning and Obstacle Avoidance for Mobile Robots

In this work, we present a complete hybrid navigation system for a two-wheel differential drive mobile robot that includes static-environment- global-path planning and dynamic environment obstacle-avoidance tasks. By the given map, we propose a multi-agent A-heuristic algorithm for finding the optimal obstacle-free path. The result is less time-consuming and involves fewer changes in path length when dealing with multiple agents than the ordinary A-heuristic algorithm. The obtained path was smoothed based on curvature-continuous piecewise cubic Bézier curve (C2 PCBC) before being used as a trajectory by the robot. In the second task of the robot, we supposed any unforeseen obstacles were recognized and their moving frames were estimated by the sensors when the robot tracked on the trajectory. In order to adapt to the dynamic environment with the presence of constant velocity obstacles, a weighted-sum model (WSM) was employed. The 2D LiDAR data, the robot’s frame and the detected moving obstacle’s frame were collected and fed to the WSM during the movement of the robot. Through this information, the WSM chose a temporary target and a C2 PCBC-based subtrajectory was generated that led the robot to avoid the presented obstacle. Experimentally, the proposed model responded well in existing feasible solution cases with fine-tuned model parameters. We further provide the re-path algorithm that helped the robot track on the initial trajectory. The experimental results show the real-time performance of the system applied in our robot.

Sources of error in open-path FTIR measurements of N&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt;O and CO&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt; emitted from agricultural fields

Abstract. Open-path Fourier transform infrared spectroscopy (OP-FTIR) is susceptible to environmental variables which can become sources of errors for gas quantification. In this study, we assessed the effects of water vapour, temperature, path length, and wind speed on quantitative uncertainties of nitrous oxide (N2O) and carbon dioxide (CO2) derived from OP-FTIR spectra. The presence of water vapour in spectra underestimated N2O mole fractions by 3 % and 12 %, respectively, from both lab and field experiments using a classical least squares (CLS) model when the reference and sample spectra were collected at the same temperature (i.e. 30 ∘C). Differences in temperature between sample and reference spectra also underestimated N2O mole fractions due to temperature broadening and the increased interferences of water vapour in spectra of wet samples. Changes in path length resulted in a non-linear response of spectra and bias (e.g. N2O and CO2 mole fractions were underestimated by 30 % and 7.5 %, respectively, at the optical path of 100 m using CLS models). For N2O quantification, partial least squares (PLS) models were less sensitive to water vapour, temperature, and path length and provided more accurate estimations than CLS. Uncertainties in the path-averaged mole fractions increased in low-wind conditions (&lt;2 m s−1). This study identified the most common interferences that affect OP-FTIR measurements of N2O and CO2, which can serve as a quality assurance/control guide for current or future OP-FTIR users.

Head-Mounted Display-Based Microscopic Imaging System with Customizable Field Size and Viewpoint.

In recent years, the use of microinjections has increased in life science and biotechnology fields; specific examples include artificial insemination and gene manipulation. Microinjections are mainly performed based on visual information; thus, the operator needs high-level skill because of the narrowness of the visual field. Additionally, microinjections are performed as the operator views a microscopic image on a display; the position of the display requires the operator to maintain an awkward posture throughout the procedure. In this study, we developed a microscopic image display apparatus for microinjections based on a view-expansive microscope. The prototype of the view-expansive microscope has problems related to the variations in brightness and focal blur that accompany changes in the optical path length and amount of reflected light. Therefore, we propose the use of a variable-focus device to expand the visual field and thus circumvent the above-mentioned problems. We evaluated the observable area of the system using this variable-focus device. We confirmed that the observable area is 261.4 and 13.9 times larger than that of a normal microscope and conventional view-expansive microscopic system, respectively. Finally, observations of mouse embryos were carried out by using the developed system. We confirmed that the microscopic images can be displayed on a head-mounted display in real time with the desired point and field sizes.

Volumetric Arc Therapy Treatment Plan Dosimetry Correction Method to Account Patient Weight Loss during a Course of Radiation Therapy.

Aim:This study aims to validate volumetric arc therapy (VMAT) plan correction method for a patient's lost weight during the course of radiotherapy.Materials and Methods:VMAT plans of prostate and head and neck cancers were considered to evaluate dosimetric effects due to external surface changes caused by patient's weight loss during treatment. Accepted VMAT treatment plan was recalculated on the planning computed tomography (CT) with a newly created external contour from cone-beam CT and was compared with the original plan. Monitor unit (MU) correction was applied based on a simple formalism, and doses were recalculated. Dose statistics were compared with the original plan. Ten patients with significant weight loss were considered to validate proposed MU correction method by comparing the dose statistics before and after MU corrections.Results:We observed 3.7%–5.2% change in the plan maximum dose for one cm change in path length to isocenter with increased planning target volume dose, D95 by 4%. The organs at risk (OAR) doses increased as high as 6.8%. Using MU correction method, target volume and OARs dose changes were reduced to <1% when compared with the original plan. The correction method brought down the maximum plan dose and volume of 95% isodose (V95) cloud below an acceptable range of 1%–2% in 10 patients treatment plans.Conclusion:Image-guided radiation therapy process detects the weight loss, which affects the treatment plan's dose distribution and should be corrected. Applying the correction method described here keeps the patient dosimetry within 1% of the original plan, which is clinically acceptable. The process of plan dosimetry correction to address weight loss can be completed within 30 min without repeating imaging and planning process.

Communicability distance reveals hidden patterns of Alzheimer's disease.

The communicability distance between pairs of regions in human brain is used as a quantitative proxy for studying Alzheimer’s disease. Using this distance, we obtain the shortest communicability path lengths between different regions of brain networks from patients with Alzheimer’s disease (AD) and healthy cohorts (HC). We show that the shortest communicability path length is significantly better than the shortest topological path length in distinguishing AD patients from HC. Based on this approach, we identify 399 pairs of brain regions for which there are very significant changes in the shortest communicability path length after AD appears. We find that 42% of these regions interconnect both brain hemispheres, 28% connect regions inside the left hemisphere only, and 20% affect vermis connection with brain hemispheres. These findings clearly agree with the disconnection syndrome hypothesis of AD. Finally, we show that in 76.9% of damaged brain regions the shortest communicability path length drops in AD in relation to HC. This counterintuitive finding indicates that AD transforms the brain network into a more efficient system from the perspective of the transmission of the disease, because it drops the circulability of the disease factor around the brain regions in relation to its transmissibility to other regions.

Reduced Optical Path Length in the Vastus Lateralis During Ramp Cycling Exercise.

Near-infrared time-resolved spectroscopy (NIRTRS) can quantitatively evaluate mean optical path length (MPL). Since an increase in optical absorbers in the NIR region (e.g. an increase in deoxygenated hemoglobin during exercise) would shorten the MPL, the NIRS measurement area may vary depending on physical and physiological characteristics of the measurement region and/or the exercise intensity. The aim of this study was to examine the changes in MPL measured by NIRTRS during ramp cycling exercise between fat layer thickness-matched subjects with different aerobic capacities. Healthy control (CON, n=8) and endurance-trained males (TR, n=8) performed ramp cycling exercise until exhaustion. Deoxygenated hemoglobin concentration (Deoxy-Hb), total hemoglobin concentration (Total-Hb) and oxygenated hemoglobin concentration (Oxy-Hb) were evaluated by a three-wavelength NIRTRS system. MPL in each wavelength (MPL760, MPL800 and MPL830) was monitored continuously. With increasing exercise intensity, Total- and Deoxy-Hb significantly increased and Oxy-Hb decreased in both groups. Total- and Oxy-Hb during exercise were significantly higher in TR than CON (P<0.05, P<0.01, respectively). Furthermore, Deoxy-Hb also tended to be higher in TR than CON (P=0.07). In addition, MPL at all wavelengths significantly shortened with an increase in exercise intensity, with no differences between CON and TR. In particular, MPL760 at peak exercise shortened more than 10% compared to the start of exercise in both groups, even though MPL830 decreased only a few per cent. These findings suggest that the NIRS measurement area may be reduced during ramp cycling exercise due to shortened MPL. Additionally, the changes in MPL may be especially greater at 760 nm than at the other wavelengths due to greater changes in Deoxy-Hb during exercise. Furthermore, this study indicates that the measurements of muscle deoxygenation using continuous-wave NIRS can be less accurate since they are significantly affected by changes in the optical path length.

Improved Quantum Particle Swarm Optimization Algorithm for Offline Path Planning in AUVs

This paper proposes an offline path planning method based on the Improved Quantum Particle Swarm Optimization (IQPSO) algorithm for Autonomous Underwater Vehicles (AUVs) in the underwater environment. The spherical modelling method is adopted to represent irregular underwater obstacles as spheres with a specified radius. Then, the IQPSO algorithm is developed to solve the problem of the limitations of the convergence and optimization ability of the traditional Quantum Particle Swarm Optimization (QPSO) algorithm and to identify the best path for AUVs. In this algorithm, to satisfy the three factors of path safety, path length and angle change of the path point, the fitness function is constructed to achieve multi-objective optimization. A smooth path is designed using the cubic spline interpolation algorithm. Different scenes or the same scene with different obstacles are designed to verify the effectiveness of the algorithm. The simulation results show that compared with PSO algorithm, QPSO algorithm, EGA algorithm and DENPSO algorithm, the path generated by IQPSO algorithm in various scenes is shorter, smoother and more stable.

Network measures: A new paradigm towards reliable novel word sense detection

In this era of digitization, with the fast flow of information on the web, words are being used to denote newer meanings. Thus novel sense detection becomes a crucial and challenging task in order to build any natural language processing application which depends on the efficient semantic representation of words. With the recent availability of large amounts of digitized texts, automated analysis of language evolution has become possible. Given corpus from two different time periods, the main focus of our work is to detect the words evolved with a novel sense precisely. We pose this problem as a binary classification task to detect whether a new sense of a target word has emerged. This paper presents a unique proposal based on network features to improve the precision of this task of detecting emerged new sense of a target word. For a candidate word where a new sense has been detected by comparing the sense clusters induced at two different time periods, we further compare the network properties of the subgraphs induced from novel sense clusters across these two time periods. Using the mean fractional change in edge density, structural similarity and average path length as features in a Support Vector Machine (SVM) classifier, manual evaluation gives precision values of 0.86 and 0.74 for the task of new sense detection, when tested on 2 distinct time-point pairs, in comparison to the precision values in the range of 0.23-0.32, when the proposed scheme is not used. The outlined method can, therefore, be used as a new post-hoc step to improve the precision of novel word sense detection in a robust and reliable way where the underlying framework uses a graph structure. Another important observation is that even though our proposal is a post-hoc step, it can be used in isolation and that itself results in a very decent performance achieving a precision of 0.54-0.62. Finally, we also show that our method is able to detect well-known historical shifts in 80% cases.

Mechanical and optical response of polymethylpentene under dynamic compression

Polymethylpentene, commonly referred to by its trade name TPX (Mitsui Chemicals, Inc.), is a thermoplastic polymer that has the potential to be a useful window material for dynamic compression experiments. For such experiments, an optically transparent or a low x-ray absorptive window is often used to maintain stress within the sample during compression. TPX can be used as a low-impedance optical and x-ray window due to its good transmittance in most parts of the electromagnetic spectrum, very low density (0.83 g/cm3), and low x-ray absorption. In dynamic compression experiments, interferometry can be used to determine the particle velocity at the interface between the sample and window. However, velocimetry measures the rate of change of the optical path length, commonly referred to as the apparent particle velocity. An experimentally determined window correction factor is needed to ascertain the actual particle velocity from the measured apparent velocity. Here, we present the results of a series of dynamic compression experiments from 1 to 31 GPa designed to characterize the mechanical and optical response of TPX, determine the range of stresses over which TPX is transparent, and determine the window correction factor. The index of refraction was found to be essentially linear in density, resulting in a simple constant correction factor. TPX was found to remain largely transparent over the entire stress range examined.

Compensation of phase drifts caused by ambient humidity, temperature and pressure changes for continuously operating interferometers

Fusion experiments rely heavily on the measurement of the line-integrated electron density by interferometry for density feed-back control. In recent years the discharge length has increased dramatically and is continuing to rise, resulting in environmentally induced phase drifts to become an increasingly worrisome subject, since they falsify the interferometer's measurement of the density. Especially in larger Tokamaks the loss of density control due to uncontrolled changes in the optical path length can have a disastrous outcome. The control of environmental parameters in large diagnostic/experimental halls is costly and sometimes infeasible and in some cases cannot be retro-fitted to an existing machine. In this report we present a very cheap (ca. €100), easily retro-fitted, real-time capable phase compensation scheme for interferometers measuring dispersive media over long time scales. The method is not limited to fusion, but can be applied to any continuously measuring interferometer measuring a dispersive medium. It has been successfully applied to the Wendelstein 7-X density feed-back interferometer.

BalanCI: Head-Referenced Cochlear Implant Stimulation Improves Balance in Children with Bilateral Cochleovestibular Loss

Introduction: To determine the impact of a head-referenced cochlear implant (CI) stimulation system, BalanCI, on balance and postural control in children with bilateral cochleovestibular loss (BCVL) who use bilateral CI. Methods: Prospective, blinded case-control study. Balance and postural control testing occurred in two settings: (1) quiet clinical setting and (2) immersive realistic virtual environment (Challenging Environment Assessment Laboratory [CEAL], Toronto Rehabilitation Institute). Postural control was assessed in 16 and balance in 10 children with BCVL who use bilateral CI, along with 10 typically developing children. Children with neuromotor, cognitive, or visual deficits that would prevent them from performing the tests were excluded. Children wore the BalanCI, which is a head-mounted device that couples with their CIs through the audio port and provides head-referenced spatial information delivered via the intracochlear electrode array. Postural control was measured by center of pressure (COP) and time to fall using the Wii^TM (Nintendo, WA, USA) Balance Board for feet and the BalanCI for head, during the administration of the Modified Clinical Test of Sensory Interaction in Balance (CTSIB-M). The COP of the head and feet were assessed for change by deviation, measured as root mean square around the COP (COP-RMS), rate of deviation (COP-RMS/duration), and rate of path length change from center (COP-velocity). Balance was assessed by the Bruininks-Oseretsky Test of Motor Proficiency 2, balance subtest (BOT-2), specifically, BOT-2 score as well as time to fall/fault. Results: In the virtual environment, children demonstrated more stable balance when using BalanCI as measured by an improvement in BOT-2 scores. In a quiet clinical setting, the use of BalanCI led to improved postural control as demonstrated by significant reductions in COP-RMS and COP-velocity. With the use of BalanCI, the number of falls/faults was significantly reduced and time to fall increased. Conclusions: BalanCI is a simple and effective means of improving postural control and balance in children with BCVL who use bilateral CI. BalanCI could potentially improve the safety of these children, reduce the effort they expend maintaining balance and allow them to take part in more complex balance tasks where sensory information may be limited and/or noisy.

Optofluidic variable optical path modulator

The optofluidic devices including optofluidic lens, optical switch and liquid prism have found widespread applications in imaging, optical communication and lighting. Here, we report a novel optofluidic device called optofluidic variable optical path modulator. Our proposed modulator consists of two main chambers. The two chambers are connected by two tubes to form a closed-loop fluidic system. Two immiscible liquids are filled into the two chambers and form two L-L interfaces. A transparent sheet is placed between one L-L interface to get flat interface. When a voltage is applied on the device, the flat interface can move up and down. Thus, variable optical path can be obtained by applying a voltage. To prove the concept, we fabricate an optofluidic device whose largest movable distance of L-L interface is ~7.5 mm and the optical path length change is ~1.15 mm. The proposed optofluidic device has potential applications in imaging, adaptive optics, optical detection and so on.

Temporal high-resolution evaluation algorithm for sinusoidally phase modulated interference signals.

In this paper, we present a practical approach for phase analysis of sinusoidally phase shifted interference signals, which are generally used to detect optical path length changes in one arm of the interferometer based on an algorithm introduced by de Groot. We describe the original algorithm from our point of view and try to emphasize the limitations and some details that need to be known for practical implementation. We introduce methods for how to overcome these limitations, and in addition, we provide an extension of the algorithm to a temporal high-resolution mode, which provides a possibility to calculate a phase value for each sampled point of an interference signal and opens new applications for the existing measurement devices without any hardware changes. Simulated and experimental results verify our extensions.

Development of R-Group Fingerprints Based on the Local Landscape from an Attachment Point of a Molecular Structure.

Molecular fingerprints are indispensable in medicinal chemistry for quantifying chemical structures. Fingerprints can be calculated for substructures with attachment points, which are positions where a substructure and a corresponding core structure connect. Because structures with attachment points can be crucial for understanding structure-activity relationships, fingerprints specialized for representing this structural feature are required. R-group fingerprints and R-group descriptors were proposed previously for this purpose; however, these molecular representations have limitations. Current R-group fingerprints do not emphasize information about attachment points, and R-group descriptors are too sensitive to changes in the topological path length from an attachment point. In the present work, we developed novel R-group fingerprints, termed R-path fingerprints, which contain substituent information from an attachment point without being sensitive to small differences in topological distances. The concept of the R-path fingerprints is to describe a chemical substructure from the viewpoint of an attachment point, to distinguish atomistic information around the attachment point and other parts of the substructure. This was achieved by considering all the paths on the shortest path between the attachment point and each atom in a substituent. Benchmark testing was conducted, including comparisons of similarity distributions and potency prediction for R-group substituents. The results showed that R-path fingerprints should be useful for classifying and comparing substructures with attachment points.

Measurement of atmospheric neutral wind and temperature from Fabry–Perot interferometer data using piloted deconvolution

Nonlinear regression techniques, when applied to sky exposures obtained using a Fabry-Perot interferometer (FPI), are able to recover atmospheric neutral wind and temperature through inversion of the resulting fringe pattern. Current inversion methods often account for temporal fluctuation of the etalon's optical path length (caused by temperature variation in the instrument housing, for example) by characterizing the system function using isolated exposures of a frequency-stabilized laser. Because these path length changes correspond directly to shifts in the fringe pattern, they can significantly increase the total wind velocity uncertainty between laser exposures. We propose an extension to current regression techniques allowing for characterization of the optical path length and measurement of neutral wind and temperature simultaneously, thus reducing the need for frequent isolated laser exposures. This is achieved by using the laser as a pilot signal that enters the aperture of the instrument during sky exposures. We show that the extension can lead to a lower variance estimator for velocity when the optical path length has a significant time-varying component. Additionally, several pragmatic physical configurations that would allow for construction of a piloted signal in a real system are tested and compared using an FPI installation at the Urbana Atmospheric Observatory.

Refractive index of lithium fluoride to 900 gigapascal and implications for dynamic equation of state measurements

Lithium fluoride (LiF) is a unique crystal possessing the largest reported bandgap of any material and is predicted to remain transparent to visible light under stresses in excess of 1000 GPa. Dynamic compression experiments often utilize LiF as a window material to maintain stress on a sample while enabling direct measurements of interface velocity. However, typical velocimetry diagnostics measure changes in the optical path length; therefore, an accurate understanding of LiF’s equation of state and refractive index is needed. Here, we present a measurement of the LiF refractive index up to 900 GPa from a low-temperature ramp-compression experiment at the National Ignition Facility. To demonstrate propagation of optical uncertainty from this work to equation of state measurements, simulations in which a tin–LiF interface reaches a peak stress of 825 GPa show that the principal isentrope of tin can be determined up to 1450 GPa with a 1.2% uncertainty in density while considering uncertainties in the optical response of LiF.