Small Setup Research Articles

Inference about the Regression Parameters Using Median-Ranked Set Sampling

The ranked set samples and median ranked set samples in particular have been used extensively in the literature due to many reasons. In some situations, the experimenter may not be able to quantify or measure the response variable due to the high cost of data collection, however it may be easier to rank the subject of interest. The purpose of this article is to study the asymptotic distribution of the parameter estimators of the simple linear regression model. We show that these estimators using median ranked set sampling scheme converge in distribution to the normal distribution under weak conditions. Moreover, we derive large sample confidence intervals for the regression parameters as well as a large sample prediction interval for new observation. Also, we study the properties of these estimators for small sample setup and conduct a simulation study to investigate the behavior of the distributions of the proposed estimators.

X-ray phase contrast microscopy at 300 nm resolution with laboratory sources

We report the performance of an X-ray phase contrast microscope for laboratory sources with 300 nm spatial resolution. The microscope is based on a commercial X-ray microfocus source equipped with a planar X-ray waveguide able to produce a sub-micrometer x-ray beam in one dimension. Phase contrast images of representative samples are reported. The achieved contrast and resolution is discussed for different configurations. The proposed approach could represent a simple, inexpensive, solution for sub-micrometer resolution imaging with small laboratory setups.

Clinical Results of Image-Guided Deep Inspiration Breath Hold Breast Irradiation

To evaluate the feasibility, cardiac dose reduction, and the influence of the setup error on the delivered dose for fluoroscopy-guided deep inspiration breath hold (DIBH) irradiation using a cone-beam CT for irradiation of left-sided breast cancer patients. Nineteen patients treated according to the DIBH protocol were evaluated regarding dose to the ipsilateral breast (or thoracic wall), heart, (left ventricle [LV] and left anterior descending artery [LAD]), and lung. The DIBH treatment plan was compared to the free-breathing (FB) treatment planning and to the dose data in which setup error was taken into account (i.e., actual delivered dose). The largest setup variability was observed in the direction perpendicular to the RT field (μ = -0.8 mm, Σ = 2.9 mm, σ = 2.0 mm). The mean (D(mean)) and maximum (D(max)) doses of the DIBH treatment plan was significantly lower compared with the FB treatment plan for the heart (34% and 25%, p < 0.001), LV (71% and 28%, p < 0.001), and LAD (52% and 39.8%, p < 0.001). For some patients, large differences were observed between the heart D(max) according to the DIBH treatment plan and the actual delivered dose (up to 71%), although D(max) was always smaller than the planned FB dose (mean group reduction = 29%, p < 0.001). The image-guided DIBH treatment protocol is a feasible irradiation method with small setup variability that significantly reduces the dose to the heart, LV, and LAD.

COMPARISON OF INTERFRACTIONAL VARIATION IN CANINE HEAD POSITION USING PALPATION AND A HEAD-REPOSITIONING DEVICE

Radiation treatment planning is performed on images that do not take variation in patient position into account. To compensate for expected variations in position of the patient, a three-dimensional expansion of the clinical target volume, or set-up margin, is added. Variations in patient position can be decreased through use of an immobilization device, allowing selection of a smaller set-up margin. The objective of this prospective study was comparison of interfractional variation in patient position between set-ups of the canine head region using palpation of bony landmarks and set-ups using a head-repositioning device. Fiducial markers were attached to the skull bones of three research dogs, and the dogs were positioned as for a typical radiation treatment of the head region using both set-up methods. A kilovoltage on-board imager was used to acquire orthogonal images and the difference between the x-, y-, and z-axis coordinates of each fiducial marker relative to the initial reference isocenter was measured. The difference in patient position for each axis coordinate was significantly lower for set-ups using the head-repositioning device than for set-ups using bony landmarks (P < 0.05). Ninety-five percent of the absolute values of the displacement vector differences were < 4.62 mm for set-up using bony landmarks, and < 1.93 mm for set-up using the head-repositioning device. A minimum set-up margin of 5-6 mm is recommended when patient set-up is based on bony landmarks and of 2-3 mm when the head-repositioning device is used.

Hybrid Fourier-real space method for diffuse optical tomography

Optical tomography has recently witnessed a substantial increase in the size of the data sets used, mainly owing to the use of CCD cameras. Larger data sets render 3D reconstructions more robust, quantitative, and reproducible, but also significantly increase the computing time needed to generate the reconstructed data. Approaches working with spatial-frequencies instead of real space variables seem to be the method of choice in this case, and a direct inversion method that can produce three-dimensional images from very large detector numbers (>10(5)) using either very large source numbers (>10(3)) [Phys. Rev. E 64, 035601 (2001)] or structured illumination [Opt. Lett. 34, 983 (2009)] has been presented. However, most small animal imaging setups typically incur a practical upper limit of only approximately 10(2) sources mainly due to imaging time constraints, and currently all relying on point source illumination. In this Letter, what we believe to be a new approach, which combines Fourier and real space functions, is shown, which fills the gap between traditional fiber-based small data sets that are solved in real space and the very large data sets solved entirely in spatial-frequency domain.

6D image guidance for spinal non-invasive stereotactic body radiation therapy: Comparison between ExacTrac X-ray 6D with kilo-voltage cone-beam CT

Purpose To investigate setup discrepancies measured with ExacTrac X-ray 6 degree-of-freedom (6D) and cone-beam computed tomography (CBCT) for patients under treatments of stereotactic body radiation therapy (SBRT). Materials and methods In this work, phantom and patient studies were performed. In the phantom studies, an anthropomorphic phantom was placed with pre-defined positions, and imaged with ExacTrac X-ray 6D and CBCT to test the accuracy of the imaging systems. In the patient studies, 16 spinal SBRT patient cases were retrospectively analyzed. The patients were initially positioned in customized immobilization cradles and then aligned with ExacTrac X-ray 6D and CBCT. The setup discrepancies were computed and quantitatively analyzed. Results This study indicates modest discrepancies between ExacTrac X-ray 6D and CBCT with spinal SBRT. The phantom experiments showed that translational and rotational discrepancies in root-mean-square (RMS) between ExacTrac X-ray 6D and CBCT were, respectively, <1.0 mm and <1°. In the retrospective patient studies, translational and rotational discrepancies in RMS between ExacTrac X-ray 6D and CBCT were <2.0 mm and <1.5°. Conclusions ExacTrac X-ray 6D represents a potential alternative to CBCT; however, pre-caution should be taken when only ExacTrac X-ray 6D is used to guide SBRT with small setup margins.

A new directed graph approach for automated setup planning in CAPP

The task of setup planning is to determine the number and sequence of setups and the machining features or operations in each setup. Now there are three main methods for setup planning, i.e., the knowledge-based approach, the graph-based approach and the intelligence algorithm-based approach. In the knowledge-based and graph-based approaches reported in the literature, the main problem is that there is no guarantee that all precedence cycles between setups can be avoided during setup formation. The methods to break precedence cycles between setups are to split one setup into smaller setups. However, the implementation of this method is difficult and complex. In the intelligence algorithm-based approach, the method to handle the precedence constraints is a penalty strategy, which does not reflect the influence of precedence constraints on setup plans explicitly. To deal with the above deficiencies, a new directed graph approach is proposed to describe precedence constraints explicitly, which consists of three parts: (1) a setup precedence graph (SPG) to describe precedence constraints between setups. During the generation of the SPG, the minimal number of tolerance violations is guaranteed preferentially by the vertex clusters algorithm for serial vertices and the minimal number of setups is achieved by using variants of the breadth-first search. Precedence cycles between setups are avoided by checking whether two serial vertex clusters can generate a cycle; (2) operation sequencing to minimise tool changes in a setup; and (3) setup sequencing to generate optimal setup plans, which could be implemented by a topological sort. The new directed graph approach will generate many optimal or near-optimal setup plans and provide more flexibility required by different job shops. An example is illustrated to demonstrate the effect of the proposed approach.

Robust Inference for Testing Order-Restricted Inference

Classification of subjects with unknown distribution in small sample size setup may involve order-restricted constraints in multivariate parameter setups. Those problems makes optimality of conventional likelihood ratio based statistical inferences not feasible. Fortunately, Roy (1953) introduced union-intersection principle(UIP) which provides an alternative avenue. Redescending M-estimator along with that principle yields a considerably appropriate robust testing procedure. Furthermore, conditionally distribution-free test based upon exact permutation theory is used to generate p-values, even in small sample. Applications of this method are illustrated in simulated data and read data example (Lobenhofer et al., 2002)

Land use change suppresses precipitation

Abstract. A feedback loop between regional scale deforestation and climate change was investigated in an experiment using novel, small size airborne platforms and instrument setups. Experiments were performed in a worldwide unique natural laboratory in Western Australia, characterized by two adjacent homogeneous observation areas with distinctly different land use characteristics. Conversion of several ten thousand square km of forests into agricultural land began more than a century ago. Changes in albedo, surface roughness, the soil water budget and the planetary boundary layer evolved over decades. Besides different meteorology, we found a significant up to now overlooked source of aerosol over the agriculture area. The enhanced number of cloud condensation nuclei is coupled through the hydrological groundwater cycle with deforestation. Modification of surface properties and aerosol number concentrations are key factors for the observed reduction of precipitation. The results document the importance of aerosol indirect effects on climate due to nanometer size biogenic aerosol and human impact on aerosol sources.

Coherent X-ray diffraction from collagenous soft tissues

Coherent X-ray diffraction has been applied in the imaging of inorganic materials with great success. However, its application to biological specimens has been limited to some notable exceptions, due to the induced radiation damage and the extended nature of biological samples, the last limiting the application of most part of the phasing algorithms. X-ray ptychography, still under development, is a good candidate to overcome such difficulties and become a powerful imaging method for biology. We describe herein the feasibility of applying ptychography to the imaging of biological specimens, in particular collagen rich samples. We report here speckles in diffraction patterns from soft animal tissue, obtained with an optimized small angle X-ray setup that exploits the natural coherence of the beam. By phasing these patterns, dark field images of collagen within tendon, skin, bone, or cornea will eventually be obtained with a resolution of 60-70 nm. We present simulations of the contrast mechanism in collagen based on atomic force microscope images of the samples. Simulations confirmed the 'speckled' nature of the obtained diffraction patterns. Once inverted, the patterns will show the disposition and orientation of the fibers within the tissue, by enhancing the phase contrast between protein and no protein regions of the sample. Our work affords the application of the most innovative coherent X-ray diffraction tools to the study of biological specimens, and this approach will have a significant impact in biology and medicine because it overcomes many of the limits of current microscopy techniques.

Study of the metastable region in the growth of GaN using the Na flux method

It was revealed that the metastable region, in which liquid phase epitaxy (LPE) of GaN single crystals proceeds without the generation of polycrystals, expands with growth temperature in the Na flux method. The metastable region appears when LPE growth proceeds at temperatures above 1073 K, although generation of polycrystals inevitably occurs on a crucible at temperatures less than 1073 K. The highest growth rate of 14 μm/h in a small experimental setup was achieved at a temperature of 1163 K with a nitrogen pressure of 5.5 MPa due to complete suppression of the growth of polycrystals on a crucible, even though the supersaturation at this condition reached a fairly high level. Also, an LPE crystal with a flat surface could easily be obtained under high-temperature conditions.

Recent progresses on atomic physics with highly charged ions in Lanzhou

Storage rings, dedicated small accelerators and experimental setups have been established during past few years in Lanzhou China. The commissioning of the heavy ion Cooler Storage Rings gained great success. These advances give good opportunities for atomic physics researches using highly charged ions. The current status of the accelerators, some experimental setups will be introduced. Examples of some research results will be selected and reported. The future aspects of atomic physics related to ion-matter interactions will be outlined.

Experimental investigation on a turbulence generation system with high-blockage plates

An experimental study was conducted to develop and characterize systematically a new turbulence generator system to yield large turbulent Reynolds numbers in a compact configuration. The effect of the geometric parameters of two families of high-blockage plates on the resulting turbulent flow field was systematically studied: one series of plates was characterized by the number and distribution of circular openings; a second series had non-circular opening(s) with different shapes, distribution and position of the opening(s). The plates were placed upstream of a contoured contraction and the near field at the centerline of the resulting turbulent free jet was characterized by hot-wire anemometry in terms of mean axial velocity, turbulence intensity, turbulence length scales and corresponding Reynolds numbers. The plate with a central, non-circular opening produced the best compromise of highest turbulence levels along with excellent uniformity in average velocity and turbulence intensity, as evidenced by scan in the transverse direction. It appears to be the most promising one. By comparison with more traditional approaches to turbulence generation, we increased the turbulent Reynolds numbers based on the integral length scale to values on the order of 1000, which was one of the design objectives. Other plate geometries also yielded intense turbulence, but, in some cases, exhibited spurious frequency peaks in their power spectrum. The turbulent generation approach is to be adapted to combustion studies to reproduce conditions typical of practical system in relatively small experimental set-ups that are well-suited for bench-top experiments.

Development of wavelength shifter coated reflectors for the ArDM argon dark matter detector

To optimise the design of the light readout in the ArDM 1-ton liquid argon dark matter detector, a rangeof reflector and WLS coating combinations were investigated in several small setups, where argon scintillation light was generated by radioactive sources in gas at normal temperature and pressure and shifted into the blue region by tetraphenyl butadiene (TPB). Various thicknesses of TPB were deposited by spraying and vacuum evaporation onto specular3MTM-foil and diffuse Tetratex® (TTX) substrates. Light yields of each reflector and TPB coating combination were compared. Reflection coefficients of TPB coated reflectors were independentlymeasured using a spectroradiometer in a wavelength range between200 and 650 nm.WLS coating on the PMT window was also studied. These measurements were used to define the parameters of the light reflectorsof the ArDM experiment. Fifteen large 120 × 25 cm2 TTX sheetswere coated and assembled in the detector. Measurements in argon gas are reported providing good evidence of fulfilling the light collectionrequirements of the experiment.

SU-FF-J-82: Evaluation of Inter-Fractional Setup Errors and Dosimetric Implication in Partial Breast Irradiation (PBI) Using Cone-Beam CT

Purpose: The objective is to evaluate inter-fractional patient setup errors in partial breast irradiation (PBI) using cone beam CT and to investigate the dosimetric impact of uncorrected setup errors. Method and Materials: Images from patients receiving PBI were acquired by on-board CBCT following initial treatment setup. Manual registration was performed daily to match fiducial markers on acquired CBCT to the planning CT. Setup errors over 10 fractions for several patients were evaluated. The resultant couch offsets were analyzed to estimate setup errors when image guidance is not available. To assess the dosimetric impact of uncorrected setup error, patient setup offsets were simulated by shifting plan isocenter with increasing magnitude in treatment planning system. Dose distribution of tumor and critical organs were compared between re-calculated plans to the original plans. The same procedure was performed using the daily setup offsets of several patients to evaluate the dosimetric impact in actual cases. Results: Although initial setup errors were found to be relatively small (<5mm), large systematic and random setup errors were observed in one patient (lateral: 9±6mm, longitudinal: 4±3mm, vertical: 2±10mm). The treatment simulation indicated that CTV volume covered by prescribed dose was within 95% when offsets were less than 3mm in all directions and decreased rapidly with larger shifts (79% for 10 mm shifts). In clinical cases, CTV coverage was found to decrease from 98.2% to 86.8% and the percentage of lung volume irradiated by 20Gy (V20) increased by nearly two folds for the case with large errors. When setup errors are within 5mm, no significant changes in dose coverage were noticed. Conclusion: Daily patient setup errors can cause significant dosimetric changes in targets and critical organs in PBI if they are not corrected. CBCT could be used to reduce the uncertainties in setup errors and hence reducing dosimetric error.

SU‐FF‐T‐86: The Effect of Set‐Up Errors On the Final Target Dose Distribution in Step‐And‐Shoot IMRT Plans Compared to Helical Tomotherapy Plans

Purpose: To compare the effect of small setup errors on the final target dose distribution when using step and shoot IMRT and helical tomotherapy. Method and Materials: For three head and neck patients, two plans were created: one for delivery on a Tomotherapy system and the second one, using the Pinnacle treatment planning system, for delivery as step‐and‐shoot IMRT. After the patient was set up on the Tomotherapy couch, a megavoltage CT was acquired. This CT was imported to the adaptive planning module of Tomotherapy and the dose was recalculated assuming the patient was not repositioned prior to treatment. The shifts that would have been required to correctly position the patient were used to alter the treatment isocenter in the pinnacle plan and the dose was recalculated. This process was repeated for seven fractions in each patient and the doses from all fractions were summed up to create a PTV DVH for each case. Results: For all three cases, the final delivered DVH showed deviations from the planned DVH. It was apparent that the discrepancy between the planned and delivered DVHs was much larger for the tomotherapy plans than the step‐and‐shoot plans. Conclusion: The results show that extra care should be exhibited in properly positioning the patient when treating with tomotherapy.

A new approach to passive protection against high energy and high current breakdowns in the ITER NBI accelerator

The energy stored in the 1 MV ITER Neutral Beam Injector power supply system will exceed by far the energy stored in the existing largest NB Injectors; as a consequence, the limitation of the grid breakdown effects–grids damage and Electro Magnetic Interference emission–are critical issues. In the present ITER NBI reference design the mitigation system is based on the concept of the concentrated core snubber which, due to the large amount of stored energy, is a huge component. Furthermore, in the NBI a relatively large part of HV capacitance to ground remains downstream the core snubber, so neither the arc peak current nor the high-frequency oscillations can be effectively limited. Moreover, the concentrated core snubber is ineffective in limiting the voltage reversal caused by internal insulation fault, increasing the risk of cascade failures in components like HV bushing and transmission line. The paper proposes an alternative approach to limit the grid breakdown effects, based on the concepts of Damper Resistor- substituting the direct connection to ground of the zero-potential accelerating grid – and of Distributed Core Snubber (DCS) – installed along the whole length of the transmission lines. The DCS concept has been subjected also to experimental validation by a small scale setup supported by electrical modelling.

Steam jet ejector cooling powered by waste or solar heat

A small scale steam jet ejector experimental setup was designed and manufactured. This ejector setup consists of an open loop configuration and the boiler operate in the temperature range of T b = 85–140 °C. The typical evaporator liquid temperatures range from T e = 5 °C to 10 °C while the typical water-cooled condenser pressure ranges from P c = 1.70 kPa to 5.63 kPa ( T c = 15–35 °C). The boiler is powered by two 4 kW electric elements while a 3 kW electric element simulates the cooling load in the evaporator. The electric elements are controlled by means of variacs. Primary nozzles with throat diameters of 2.5 mm, 3.0 mm and 3.5 mm are tested while the secondary ejector throat diameter remains unchanged at 18 mm. These primary nozzles allow the boiler to operate in the temperature range of T b = 85–110 °C. When the nozzle throat diameter is increased, the minimum boiler temperature decreases. A primary nozzle with a 3.5 mm throat diameter was tested at a boiler temperature of T b = 95 °C, an evaporator temperature of T e = 10 °C and a critical condenser pressure of P crit = 2.67 kPa (22.6 °C). The system's COP is 0.253. In a case study the experimental data of a solar powered steam jet ejector air conditioner is investigated. Solar powered steam ejector air conditioning systems are technical and economical viable when compared to conventional vapour compression air conditioners. Such a system can either utilise flat plate or evacuated tube solar thermal collectors depending on the type of solar energy available.

SU‐GG‐T‐162: Correlations Between Potential Setup Errors and Dose Gradients When Verifying Patient Specific DQA Plans of IMRT

Purpose: Fourteen cases out of 150 IMRT DQA (dose quality assurance) plans showed measured dose differences of particular fields &gt; ±10%. We investigated the relationship between potential setup errors, and dose gradients and dose differences. Method and Materials: A 0.125 cc ion‐chamber and a home‐made cylindrical phantom were used for verifying patient specific DQA plans of IMRT. We investigated dose gradients within ±3 mm from a verification point along x, y, z axes of 5 DQA plans where dose differences of any fields were within ±5% and of 14 DQA plans where at least one of fields had dose differences of &gt; ±10% at planed delivery dose larger than 10 cGy. Reflecting potential setup errors, we moved the verification point along the axis of the steepest dose gradient and searched the point that dose differences of any fields were within ±10%. Results: For the DQA plans of dose differences &lt; ±5%, the average dose variation along x, y, z axis was 0.6%, 0.6%, 0.3%, respectively. The same variation for the DQA plans of dose differences &gt; ±10% was 1.6% (3.5 cGy), 1.2% (2.5 cGy), 0.8% (1.8 cGy), respectively. The correlation between those variations of the two groups was statistically significant (p‐value: 0.034). Except six cases of 14 DQA plans, all fields showed dose differences smaller than ±8% by shifting the ion‐chamber less than 3 mm from the original location. The average of all field dose differences was reduced from 4.7% to 3.6% after shifting. Conclusion: Due to steep dose gradients, small setup errors less than 3 mm significantly affect the measured doses of individual fields, of which dose differences could be larger than ±10%. Such a large difference at a particular field can occur, even the total dose difference is less than ±3%.

Continuous reaction performances of benzene alkylation with long chain olefins catalyzed by ionic liquid

Based on a compulsive mixing-reacting-separating-recycling small experimental setup,the continuous reaction performances of benzene alkylation with long chain olefins catalyzed by [BMIM]Cl-AlCl3 ionic liquid were investigated. Three different situations including normal continuous operation mode (reagent materials), sidetrack feeding from different axial positions along the static mixing reactor (reagent materials) and normal continuous alkylation using industrial paraffin and olefins materials were examined. Even under the relatively hypecritical reaction conditions, the single pass conversion of pure 1-dodecene could reach to nearly 100.0%, and the selectivity of 2-phenyl isomer was higher than 37.7%. Although the positions along the reactor for sidetrack feeding were different, the 100.0% single pass conversion of 1-dodecene was also attained before the outlet of the reactor. The refined industrial olefins as raw material could meet with the requirements of continuous alkylation. The influences of impurities such as di-olefins and non-benzene aromatics on the catalytic activity and stability should be studied further.