Longitudinal Shift Research Articles

Sources of variation in reflectance spectrophotometric data: a quantitative analysis using avian eggshell colours

Summary1. The evolution of coloration has generated some of the most diverse and variable phenotypes, both within and between species, in animals and plants. The objective quantitative assessment of the physical, chemical and perceptual basis of coloration has been greatly improved by the application of portable full‐spectrum spectrophotometers to measure reflectance data. Yet, the analysis and interpretation of physical measures of colour spectra must be conducted within the constraints of the uncertainty regarding the relative impacts of methodological vs. biological sources of variation.2. Here, we characterise the components of variation in data on reflectance spectra, related to sample storage and measurement equipment, to characterise colourful pigmentation of eggshells (Class: Aves) of two Turdus species. We quantified longitudinal shifts in reflectance occurring over repeated measurements of the same sets of avian eggshells. Shells were sampled at the time of collection and again after 5 years of dark storage using the same equipment. These data were then compared with spectra obtained from the same eggs after the storage with a different model of spectrophotometer for three colour metrics [blue‐green chroma (BGC), UV chroma and brightness].3. Blue‐green chroma and brightness of the same eggs varied systematically between years at a similar magnitude to the biological variation among different eggs. This suggests the need for future research into the extent of chemical and physical deterioration of eggshell appearance even during relatively short‐term storage. The variation introduced by using two different spectrophotometers also was significant but relatively small compared with biological levels of variation for UV and brightness.4. Our results confirm quantitatively that museum eggshell specimens are suitable for interspecific comparative analyses, but also highlight the requirement to account explicitly for variation in storage duration and measurement equipment, when ‘objectively’ comparing biological variation in coloration across individuals in space and also in time.

Optical Property of a Colloidal Solution of Platinum and Palladium Nanorods: Localized Surface Plasmon Resonance

The optical properties of Pt and Pd nanorods as a function of aspect ratio were investigated and systematically compared with Au nanorods of similar physical dimensions. The overall optical properties of Pt and Pd nanorods were tailored by controlling aspect ratio and could be tuned from 400 nm up to near-IR spectral window. Their longitudinal mode red shifts as the length increases, whereas the transverse mode blue shifts very slightly. The comparison of observed LSPR modes in Pt and Pd NRs with Au NRs as a function of aspect ratio exhibited that Pd NRs are most sensitive to variations in rod length. The magnitude of longitudinal mode shift per unit change of NR length could be obtained from the slope of a linear fit of each plot. Pd NRs show the largest dependence with a value ca. 6.72 (Δλ/ΔL). For Pt and Au NRs, the slope is ca. 4.23 and 3.11, respectively.

A Method to Determine Main Direction of a Curved Bridge’s Mode Shape

AbstractDue to the special construction feature, the mode shape of a curved bridge has “flexure—torsion” coupling situation. In order to determine whether the main direction of the mode shape is flexure or torsion, each mode shape was divided into four sub directions which are vertical bending, pure torsion, transverse bending and longitudinal shift respectively. Accordingly, the energy of each mode was also subdivided into four directions. The ratios between the energy of sub direction and the total energy of a mode were denoted by four direction parameters. Theoretical derivation for the direction parameters was given based on the energy conversation principle of each mode of undamped system. The derivation result reveals that four formulas of the direction parameters are only related to structural mass, sectional geometric characteristics and mode vectors. Finally, the method of determining the main sub direction of mode shape of a curve bridge was given according to the values of the four parameters, ...

Clinical accuracy of ExacTrac intracranial frameless stereotactic system

In this paper, the authors assess the accuracy of the Brainlab ExacTrac system for frameless intracranial stereotactic treatments in clinical practice. They recorded couch angle and image fusion results (comprising lateral, longitudinal, and vertical shifts, and rotation corrections about these axes) for 109 stereotactic radiosurgery and 166 stereotactic radiotherapy patient treatments. Frameless stereotactic treatments involve iterative 6D image fusion corrections applied until the results conform to customizable pass criteria, theirs being 0.7 mm and 0.5° for each axis. The planning CT slice thickness was 1.25 mm. It has been reported in the literature that the CT slices' thickness impacts the accuracy of localization to bony anatomy. The principle of invariance with respect to patient orientation was used to determine spatial accuracy. The data for radiosurgery comprised 927 image pairs, of which 532 passed (pass ratio of 57.4%). The data for radiotherapy comprised 15983 image pairs, of which 10 050 passed (pass ratio of 62.9%). For stereotactic radiotherapy, the combined uncertainty of ExacTrac calibration, image fusion, and intrafraction motion was (95% confidence interval) 0.290-0.302 and 0.306-0.319 mm in the longitudinal and lateral axes, respectively. The combined uncertainty of image fusion and intrafraction motion in the anterior-posterior coordinates was 0.174-0.182 mm. For stereotactic radiosurgery, the equivalent ranges are 0.323-0.393, 0.337-0.409, and 0.231-0.281 mm. The overall spatial accuracy was 1.24 mm for stereotactic radiotherapy (SRT) and 1.35 mm for stereotactic radiosurgery (SRS). The ExacTrac intracranial frameless stereotactic system spatial accuracy is adequate for clinical practice, and with the same pass criteria, SRT is more accurate than SRS. They now use frameless stereotaxy exclusively at their center.

SU-E-J-31: Site Specific Setup Errors Analysis of MVCT Daily Imaging with TomoTherapy

Purpose: To analyze the variation in patient setup and anatomical changes for five different anatomical sites observed in Helical TomoTherapy (HT). Methods: 52 patients treated for five anatomical sites [brain (10), head‐neck (13), Lung (10), abdomen (9) and pelvis (10)] using a HT system were analyzed.Brain, head and neck patients were immobilized with thermoplastic orfit while Lung, abdomen and pelvis patients were immobilized with body fix. Prior to the treatment, three external fiducials per patient were used for setup, which consisted of skin tattoos for prostate and lung patients. There was a marking on mask for head‐neck and brain patients. Daily megavoltage computed tomography (MVCT) images were acquired prior to each treatment and were fused with the planning Kilovoltage Computed Tomography (KVCT) reference image to determine the daily setup errors and deformation. The setup errors were corrected before treatment and were used, along with the organ motions, to determine the planning target volume (PTV) margins. Results: Mean lateral, longitudinal and vertical shift was found more for Pelvis (1 mm), Abdomen (3.34 mm) and brain (6 mm) respectively. Results of setup error analysis are largely influenced by restricting specific degrees of freedom during image registration. If a yaw and pitch rotations exist during fusion, this will increase the lateral shift correction. If a pitch offset exist, the restriction will increase the vertical and longitudinal shift correction. The results are analyzed by restricting pitch and yaw and corrections are made for roll only. Conclusions: The setup errors are site specific and statistically significant. The data presented in this work might be useful in developing advanced radiotherapy technique. These interfractional variations if not adequately accounted for, can result in the delivery of suboptimal dose distribution. HT system used in this study, have capability of quantifying and addressing these variations.

SU‐E‐J‐101: Towards MR‐Only Simulation: A QA Phantom for Coalescing Consecutive MR Scans of the Head and Neck

Purpose: One strategy for reducing the amount of time required to MR scan the volume required for radiation treatment planning of the head and neck region (top of head to apex of lung) is to divide this volume into three consecutive scans using different scan volumes, fields of views, and resolutions. Unlike CT, MR image positions are reconstructed relative to the isocenter of magnetic field. Thus for different scan volumes, the MR couch moves the volume of interest to the isocenter. Couch movement error must be quantified if several consecutive MR datasets are to be coalesced accurately along the cranial‐caudal axis. A QA phantom was constructed to quantify MR couch movement error. Methods and Materials: The phantom consists of three pieces of 2mm acrylic material arranged in a figure “N” within a hollow, acrylic box filled with distilled water. The angles within the N were designed to detect longitudinal shift errors of 1mm. Geometric accuracy of the QA phantom was evaluated using CT. Using a Philips 3T Archieva MR scanner, the phantom was imaged in sections using different resolutions, field of views, couch positions and varying couch loads. Results: A couch shift error of 0.3±0.4mm and 0.8±0.3 mm was measured for 5cm and 10 cm movements, respectively with 95kg load. For no load, the corresponding values were 0.1±0.2mm and 0.3±0.4mm. Three consecutive scans of the QA phantom acquired with different sequences and FOVs (240∼360mm) and resolution (0.95×0.95×1mm3 and 1×1×2mm3) were accurately ‘stitched’ into one data set using the quantified couch shift correction. Conclusions: The QA phantom developed for this work could be used to quantify absolute MR couch shift and geometrically correct for any couch error in the coalescing of consecutive MR scans. It may be useful as a daily QA tool for MR simulation.

SU‐E‐T‐357: Development of An Anthropomorphic Head Phantom for the Assessment of Proton Therapy Treatment Procedures

Purpose: Develop an anthropomorphic head phantom for the evaluation of proton therapy treatment procedures from simulation to treatment planning and treatment delivery. Methods: A head phantom was designed and constructed from materials tested specifically with proton beams to match stopping powers and Hounsfield Units of corresponding human anatomy. Separate MR (water‐filled)‐ and CT (polyethylene)‐compatible inserts were designed for imaging (including target delineation) and dosimetry verification. The dosimetry insert contained radiochromic film and TLD dosimeters. The phantom was imaged with MR to outline the target and fused with a CT image for the dose distribution calculation. Passive scattering and spot scanning treatment plans were designed using the Eclipse proton planning system per M.D. Anderson Proton Centerˈs standard brain protocol. The phantom was irradiated according to each treatment plan three separate times. The dose distributions and absolute point doses determined with film and TLD were compared to calculated points, dose profiles and dose distributions, using a gamma analysis with pass criteria of 5%/3mm and 5%/5mm, to determine agreement and reproducibility. Results: The average passive scatter plan pixel pass rates were 91.9% and 97.4% for 5%/3mm and 5%/5mm criteria, respectively. The average lateral shift ‐ mean(standard deviation) ‐ was 2.5mm(1.8mm); the average longitudinal shift was −2mm(1.9mm); the average transverse shift was 1.7mm(2.8mm). The average spot scan plan pass rates were 90.4% and 98.4% for 5%/3mm and 5%/5mm criteria, respectively. The average lateral shift was 2.2mm (1.4mm); the average longitudinal shift was −1.6mm(1.1mm) on the inferior side and 3.1mm(4.3mm) on the superior side; the average transverse shift was −0.9mm(0.4mm). Conclusions: A proton head phantom made of proton suitable plastics was developed that can verify the agreement between treatment plans and measurement that can be used to credential proton therapy facilities for participation in NCI‐funded clinical trials.Work supported by PHS CA010953 and CA081647, awarded by NCI, DHHS and Massachusetts General Hospital Federal Share Funds.

Structural, electronic, and optical properties of nanocrystalline As-doped ZnO films on quartz substrates determined by Raman scattering and infrared to ultraviolet spectra

Nanocrystalline As-doped ZnO films with different laser power energy (40 mJ and 55 mJ) and As doping concentrations (C As from 1% to 3%) have been grown on quartz substrates by pulsed laser deposition. The average grain size of the films was calculated from the (002) peak of x-ray diffraction patterns and is estimated to vary from 9 to 13 nm. Electronic transitions and optical properties of the films have been investigated by Raman scattering, far-infrared reflectance, and infrared-ultraviolet spectral transmittance technique. With increasing doping concentration, the A 1 longitudinal optical phonon mode shifts towards the lower energy side and can be described by (564-75C As) cm -1 owing to the increment of free carrier concentration. The E 1 transverse optical phonon frequency is located at about 415 cm -1 and does not show an obvious decreasing trend with the C As. The optical constants in the photon energy range of 0.5–6.5 eV have been extracted by fitting the experimental data with the Adachi's model. The refractive index dispersion in the transparent region can be well expressed by a Sellmeier's single oscillator function. Due to different doping concentration and hexagonal crystalline structure, the optical band gap of the films grown at 40 mJ linearly decreases with increasing As concentration. The phenomena agree well with the results from the theoretical calculations.

A STUDY OF THE PHOTOMETRIC VARIABILITY OF THE PECULIAR MAGNETIC WHITE DWARF WD 1953–011

We present and interpret simultaneous new photometric and spectroscopic observations of the peculiar magnetic white dwarf WD1953-011. The flux in the V-band filter and intensity of the Balmer spectral lines demonstrate variability with the rotation period of about 1.45 days. According to previous studies, this variability can be explained by the presence of a dark spot having a magnetic nature, analogous to a sunspot. Motivated by this idea, we examine possible physical relationships between the suggested dark spot and the strong-field magnetic structure (magnetic "spot", or "tube") recently identified on the surface of this star. Comparing the rotationally-modulated flux with the variable spectral observables related to the magnetic "spot" we establish their correlation, and therefore their physical relationship. Modeling the variable photometric flux assuming that it is associated with temperature variations in the stellar photosphere, we argue that the strong-field area and dark, low-temperature spot are comparable in size and located at the same latitudes, essentially overlapping each other with a possible slight longitudinal shift. In this paper we also present a new, improved value of the star's rotational period and constrain the characteristics of the thermal inhomogeneity over the degenerate's surface.

Ultrasensitive phase estimation with white light

An improvement of the scheme by Brunner and Simon [Phys. Rev. Lett. 105, 010405 (2010)] is proposed in order to show that quantum weak measurements can provide a method to detect ultrasmall longitudinal phase shifts, even with white light. By performing an analysis in the frequency domain, we find that the amplification effect will work as long as the spectrum is large enough, irrespective of the behavior in the time domain. As such, the previous scheme can be notably simplified for experimental implementations.

Control of light transmission in laser-written phase-shifted Bragg grating couplers

We demonstrate the fabrication by direct laser writing and the operation of a directional coupler containing Bragg gratings in each waveguide. We achieve high-precision control over the longitudinal shift between the gratings, which feature first-order Bragg resonance at telecommunication wavelengths. We observe fundamental differences between light transmission characteristics in couplers with unshifted and shifted gratings in agreement with theoretical predictions.

Measurement of longitudinal displacement using lateral shearing cyclic path optical configuration setup and phase shifting interferometry

We present a technique for the measurement of longitudinal displacement using a lateral shearing cyclic path optical configuration (CPOC) setup and phase shifting interferometry. In the technique, a plane mirror mounted on a linear translation stage, placed slightly away from the focal plane of a lens, introduces a longitudinal focal shift to the incident focusing beam. The resulting spherical wavefront emerging from the lens is sheared into two orthogonally polarized beams using the CPOC setup. By applying polarization phase shifting interferometry (PPSI), the longitudinal focal shift of the beam focus is calculated by determining the slope of the optical path difference variation between the sheared beams. Similarly, the additional focal shift introduced due to longitudinal translation of the mirror, by an unknown amount, is determined using PPSI. Half of the difference between the two longitudinal focal shifts measured gives the longitudinal displacement of the mirror. The technique can be used for an extended range of distance measurement. The novelty of the technique is the introduction of CPOC for the distance measurement. The advantages of the technique compared to other related methods are discussed.

Influence of stirring in the synthesis of gold nanorods

Gold nanorods have been prepared by the seed-mediated growth method, in order to find the effect of stirring during the synthesis to the final shape and optical properties. The presence or absence of stirring during each step of the preparation procedure was considered a parameter to control in order to adjust the optical absorption associated with the surface plasmon resonance of the nanorods. Results show that the longitudinal surface plasmon resonance band shifts to larger wavelengths in the absence of stirring of the growth solution. Width and intensity of the absorption band associated with the longitudinal surface plasmon is reduced upon stirring during the synthesis. On the contrary, the position of the transversal surface plasmon resonance band scarcely depends upon stirring. Theoretical calculations performed using the Gans model are coherent with experimental obtained results, showing that as the aspect ratio increases, longitudinal plasmons absorption shifts toward larger wavelengths and increases both intensity and bandwidth.

A comparative study to evaluate the efficacy of on board imaging with cone beam CT using target registration in patients with lung tumors undergoing stereotactic body radiation therapy and comparison with ExacTrac using skeletal registration on Novalis Tx

Stereotactic body radiation therapy is an advanced technique, which delivers ablative doses to lung lesions. Target verification is done either by orthogonal x-rays or cone beam CT. This study was undertaken to compare these two verification methods. To evaluate the efficacy of ExacTrac and Cone Beam Computed Tomography (CBCT) for target repositioning while delivering Stereotactic Body Radiation Therapy (SBRT) for lung lesions and derive the population-based margin. All patients who had undergone SBRT for lung lesions from February to September 2009 were involved. Patients were immobilized using the BodyFix double vacuum immobilization system, indexed to the computed tomography (CT) simulator and treatment machine. Four-dimensional (3-D) scan was done to generate internal target volume (ITV) and a free breathing CT scan for planning was done on the BrainLab iPlan 4.1 software. During treatment, patient's position was verified using ExacTrac and CBCT. The resulting vertical, lateral, and longitudinal shifts were noted. The random and systematic error were calculated and the margin recipe derived using the Van Herk formula. Sixteen patients had undergone SBRT for lung tumors from February to September 2009. Data from eight patients who had undergone 34 sessions of SBRT was analyzed. The systematic error for lateral, longitudinal, and vertical shifts for ExacTrac and CBCT were 3.68, 4.27, 3.5 mm and 0.53, 0.38, 0.70 mm, respectively. The random error were 1.10, 1.51, 1.96 mm and 0.32, 0.81, 0.59 mm. The lateral, longitudinal and vertical Van Herk margin recipe for ExacTrac were 9.98, 11.72, 10.18 mm, respectively, and for CBCT was 2.17, 1.53,1.55 mm. The systematic and random errors for CBCT were significantly lesser as compared to the errors with Exactrac.

Shifts of beam centroid of Laguerre-Gaussian beams reflected and refracted at a dielectric interface

We study shifts of the beam centroid of linearly polarized paraxial Laguerre-Gaussian beams reflected and refracted at an interface of isotropic dielectric in the cylindrical coordinate system. According to the Fresnel approximation and the Taylor series expansion, we derive analytical expressions for transverse and longitudinal shifts and their general relationship with topological charge in the cases of partial and total reflection, respectively. It is shown that in the partial reflection regime, transverse shifts of both reflected and refracted beams are in proportion to the topological charge of beams and their directions are determined by the sign of the topological charge, while only the value of longitudinal shift is related to the topological charge. In the regime of total reflection, the shift of reflected beam centroid is independent of topological charge. To verify our analytical results, we perform numerical simulations of the shifts of reflected and refracted beams directly and indicate the applicable condition of the analytical expressions. The shifts of the beam centroid can be applied to the measurement of the topological charge and radial node number of Laguerre-Gaussian beams, which is of significance for information encoding and communication.

Gradual declination of IGF-1 over a year after transsphenoidal adenomectomy of GH producing pituitary adenomas

To know the longitudinal shift of blood IGF-1 of cured acromegaly, we conducted retrospective survey of changes in blood IGF-1 over two years, which has not been previously investigated. Blood IGF-1 levels were measured for longer than 2 years after TSS in 37 patients whose nadir GH during postoperative oral glucose tolerance test (OGTt) was under 1 ng/mL. Blood IGF-1 very gradually declined after three months; 230.6 (mean) ng/mL at 3-12 months, 202.3 ng/mL at 12-24 months, and 198.6 ng/mL at 24-36 months. Their SD values, calculated based on standard IGF-1 values of age- and sex-matched Japanese population, also slowly decreased after three months; 1.69 (mean) at 3-12 months, 1.23 at 12-24 months, and 1.12 at 24-36 months. Very slow decrease of the IGF-1 levels continued beyond the first several months and even the first year after TSS. The declination of values is greater than that associated with aging. This declination may be at least partially a reflection of the slow decrease and late normalization of GH secretion.

Role of the HAMP Domain Region of Sensory Rhodopsin Transducers in Signal Transduction

Archaea are able to sense light via the complexes of sensory rhodopsins I and II and their corresponding chemoreceptor-like transducers HtrI and HtrII. Though generation of the signal has been studied in detail, the mechanism of its propagation to the cytoplasm remains obscured. The cytoplasmic part of the transducer consists of adaptation and kinase activity modulating regions, connected to transmembrane helices via two HAMP (histidine kinases, adenylyl cyclases, methyl-accepting chemotaxis proteins, phosphatases) domains. The inter-HAMP region of Natronomonas pharaonis HtrII (NpHtrII) was found to be α-helical [Hayashi, K., et al. (2007) Biochemistry 46, 14380-14390]. We studied the inter-HAMP regions of NpHtrII and other phototactic signal transducers by means of molecular dynamics. Their structure is found to be a bistable asymmetric coiled coil, in which the protomers are longitudinally shifted by ~1.3 Å. The free energy penalty for the symmetric structure is estimated to be 1.2-1.5 kcal/mol depending on the molarity of the solvent. Both flanking HAMP domains are mechanistically coupled to the inter-HAMP region and are asymmetric. The longitudinal shift in the inter-HAMP region is coupled with the in-plane displacement of the cytoplasmic part by 8.6 Å relative to the transmembrane part. The established properties suggest that (1) the signal may be transduced through the inter-HAMP domain switching and (2) the inter-HAMP region may allow cytoplasmic parts of the transducers to come sufficiently close to each other to form oligomers.

Thickness measurement of transparent glass plates using a lateral shearing cyclic path optical configuration setup and polarization phase shifting interferometry

We present a measurement technique to determine the thickness of a transparent glass plate (GP) by using a lateral shearing cyclic path optical configuration (CPOC) setup and polarization phase shifting interferometry (PPSI). In the technique, the GP introduces a longitudinal shift in the focus of the beam and, as a result, a spherical wavefront emerges from the lens, which is otherwise set for producing a collimated beam. Using CPOC, two laterally sheared orthogonally polarized beams are generated from the incident spherical wavefront. By applying PPSI, the slope of the optical path difference variation between the laterally sheared interfering beams is evaluated, and the radius of the spherical wavefront and the longitudinal shift of the beam focus are calculated. The thickness of the GP is determined from the standard relation between the longitudinal shift of the focus introduced by the GP and the thickness of the GP. Results obtained for a GP of 9.810mm thickness are presented.

Niche separation between Encarsia dispersa and Encarsia guadeloupae, two biological control agents of the spiraling whitefly Aleurodicus dispersus, in Benin, West Africa

The spiraling whitefly Aleurodicusdispersus (Russell) is an insect pest that causes substantial damage to ornamental plants, shade trees and food crops. It was first observed in Benin in 1993. Two host specific parasitoids, Encarsia dispersa and E. guadeloupae, fortuitously introduced with its host, were recovered in the second half of 1993 in Southern Benin. Survey results from 1993 to 1995 (already published) showed the decline in the population of A. dispersus due to the parasitoids, and the spread from Cotonou (6°10′N) in a northern directions of both parasitoids and their host. Results from similar field surveys from 1996 to 2003 document that the spiraling whitefly and both its parasitoids spread to Natitingou (10°20′N, 540 km) in 1995 and Bembereke (10°14′N) in 1996, whereby E. dispersa arrived within less than a year of its host and quickly became dominant in the two localities on the northern front. In subsequent years, the parasitoids established their geographical niches, with E. dispersa being more abundant (up to 89%) in the coastal south bellow latitude 7°30′N and E. guadeloupae (up to 84%) in the north between latitudes 7°30′ and 10°30′N. We conclude that the gradual replacement observed over ten years and over 500 km has to do with longitudinal shifts in the length and severity of the dry season and the higher susceptibility to these conditions by E. dispersa.

Biological applications of gold nanorods

Gold nanoparticles have been used as an additive for aesthetic purposes for centuries. However, only in the last decade scientists have begun to understand the fundamental concepts that explain the fascinating optical properties nanoscale particles possess. Gold nanoparticles may be tuned to absorb and scatter light in the visible to near-infrared region of the electromagnetic spectrum. These properties result from the collective oscillations of electrons along the metal surface and can be altered by changing the particles' shape, size, or environment. Gold nanoparticles having a rod-like morphology are of particular interest because of their anisotropic shape. The absorption profile of gold nanorods includes two absorption bands: one due to light absorbed along the short axis (transverse) and the other due to absorption along the long axis (longitudinal). As the rod length increases, so does the longitudinal band red shift together with an increase in the extinction coefficient. As a result of this optical control and sensitivity to changes in local environment, gold nanorods are useful materials for sensing, photothermal therapy, and imaging. This article highlights established and emerging applications of gold nanorods as a platform for viable biological tools.