Differential Setup Research Articles

Assessment of Three-dimensional Set-up Errors using Megavoltage Computed Tomography (MVCT) during Image-guided Intensity-modulated Radiation Therapy (IMRT) for Craniospinal Irradiation (CSI) on Helical Tomotherapy (HT)

The purpose of this study was to assess three-dimensional (3D) set-up errors using megavoltage computed tomography (MVCT) during image-guided intensity-modulated radiation therapy (IMRT) for supine craniospinal irradiation (CSI) on helical tomotherapy (HT). Patients were immobilized in a customized 4-clamp thermoplastic head mask with or without whole-body vacuum cradle. Set-up was based primarily on a set of cranial fiducial markers. MVCT scans were acquired and co-registered with planning scan separately at three different levels (brain, upper, and lower spine) at every fraction. Only translational displacements were analysed, wherein positive sign denotes deviation in anterior, left, and superior direction; while negative sign denotes deviation in posterior, right, and inferior direction. Mean displacements, systematic, and random errors of the study population were calculated at all three levels separately. Local residual uncertainty of the upper and lower spine was also derived assuming perfect co-registration of the skull. Set-up margins for clinical target volume (CTV) to planning target volume (PTV) were derived at these three levels separately using published margin recipes. Data from 1868 co-registrations in 674 fractions on 33 patients was included. The mean displacements in the lateral, longitudinal, and vertical directions were -1.21, -1.36, and 1.38 mm; -1.25, -0.34, and 0.65 mm; and -1.47, -2.78, and 0.22 mm for the brain; upper spine; and lumbar spine respectively. The corresponding 3D vector of displacement was 2.28; 1.45; and 3.15 mm respectively. There was a distinct systematic trend towards increasing inaccuracy from the brain towards the lower spine. Using Stroom's formula, the minimum recommended CTV to PTV margins in absence of daily image-guidance were 6.5; 7.0; and 9.5 mm for the brain; upper spine; and lower spine respectively. This increased to 7.5; 8.5; and 11.5 mm using van Herk's formula. Subset and sensitivity analyses could not identify any factor predictive of increased inaccuracy. Residual uncertainty of the spinal column was lesser after daily co-registration referenced to the skull, suggesting that smaller set-up margins maybe appropriate while using daily image-guidance with an online correction protocol. Daily MVCT imaging during supine CSI on HT provides volumetric verification of the set-up process. There is substantial site-dependent variability in translational displacements that increases systematically from brain towards the lower spine with implications for differential set-up -margins for the brain, upper, and lower spine.

Structural and functional insights into CARDs of zebrafish (Danio rerio) NOD1 and NOD2, and their interaction with adaptor protein RIP2.

Nucleotide-binding and oligomerization domain-containing protein 1 (NOD1) and NOD2 are cytosolic pattern-recognition receptors (PRRs) composed of an N-terminal caspase activation and recruitment domain (CARD), a central NACHT domain and C-terminal leucine-rich repeats (LRRs). They play a vital role in innate immune signaling by activating the NF-κB pathway via recognition of peptidoglycans by LRRs, and ATP-dependent self-oligomerization of NACHT followed by downstream signaling. After oligomerization, CARD/s play a crucial role in activating downstream signaling via the adaptor molecule, RIP2. Due to the inadequacy of experimental 3D structures of CARD/s of NOD2 and RIP2, and results from differential experimental setups, the RIP2-mediated CARD-CARD interaction has remained as a contradictory statement. We employed a combinatorial approach involving protein modeling, docking, molecular dynamics simulation, and binding free energy calculation to illuminate the molecular mechanism that shows the possible involvement of either the acidic or basic patch of zebrafish NOD1/2-CARD/a and RIP2-CARD in CARD-CARD interaction. Herein, we have hypothesized 'type-I' mode of CARD-CARD interaction in NOD1 and NOD2, where NOD1/2-CARD/a involve their acidic surfaces to interact with RIP2. Asp37 and Glu51 (of NOD1) and Arg477, Arg521 and Arg529 (of RIP2) were identified to be crucial for NOD1-RIP2 interaction. However, in NOD2-RIP2, Asp32 (of NOD2) and Arg477 and Arg521 (of RIP2) were anticipated to be significant for downstream signaling. Furthermore, we found that strong electrostatic contacts and salt bridges are crucial for protein-protein interactions. Altogether, our study has provided novel insights into the RIP2-mediated CARD-CARD interaction in zebrafish NOD1 and NOD2, which will be helpful to understand the molecular basis of the NOD1/2 signaling mechanism.

A differential dielectric spectroscopy setup to measure the electric dipole moment and net charge of colloidal quantum dots

A sensitive dielectric spectroscopy setup is built to measure the response of nanoparticles dispersed in a liquid to an alternating electric field over a frequency range from 10(-2) to 10(7) Hz. The measured complex permittivity spectrum records both the rotational dynamics due to a permanent electric dipole moment and the translational dynamics due to net charges. The setup consists of a half-transparent capacitor connected in a bridge circuit, which is balanced on pure solvent only, using a software-controlled compensating voltage. In this way, the measured signal is dominated by the contributions of the nanoparticles rather than by the solvent. We demonstrate the performance of the setup with measurements on a dispersion of colloidal CdSe quantum dots in the apolar liquid decalin.

Volatility of Organic Aerosol: Evaporation of Ammonium Sulfate/Succinic Acid Aqueous Solution Droplets

Condensation and evaporation modify the properties and effects of atmospheric aerosol particles. We studied the evaporation of aqueous succinic acid and succinic acid/ammonium sulfate droplets to obtain insights on the effect of ammonium sulfate on the gas/particle partitioning of atmospheric organic acids. Droplet evaporation in a laminar flow tube was measured in a Tandem Differential Mobility Analyzer setup. A wide range of droplet compositions was investigated, and for some of the experiments the composition was tracked using an Aerosol Mass Spectrometer. The measured evaporation was compared to model predictions where the ammonium sulfate was assumed not to directly affect succinic acid evaporation. The model captured the evaporation rates for droplets with large organic content but overestimated the droplet size change when the molar concentration of succinic acid was similar to or lower than that of ammonium sulfate, suggesting that ammonium sulfate enhances the partitioning of dicarboxylic acids to aqueous particles more than currently expected from simple mixture thermodynamics. If extrapolated to the real atmosphere, these results imply enhanced partitioning of secondary organic compounds to particulate phase in environments dominated by inorganic aerosol.

Selective Sodium Sensing with Gold-Coated Silicon Nanowire Field-Effect Transistors in a Differential Setup

Ion-sensitive field-effect transistors based on silicon nanowires with high dielectric constant gate oxide layers (e.g., Al2O3 or HfO2) display hydroxyl groups which are known to be sensitive to pH variations but also to other ions present in the electrolyte at high concentration. This intrinsically nonselective sensitivity of the oxide surface greatly complicates the selective sensing of ionic species other than protons. Here, we modify individual nanowires with thin gold films as a novel approach to surface functionalization for the detection of specific analytes. We demonstrate sodium ion (Na(+)) sensing by a self-assembled monolayer (SAM) of thiol-modified crown ethers in a differential measurement setup. A selective Na(+) response of ≈-44 mV per decade in a NaCl solution is achieved and tested in the presence of protons (H(+)), potassium (K(+)), and chloride (Cl(-)) ions, by measuring the difference between a nanowire with a gold surface functionalized by the SAM (active) and a nanowire with a bare gold surface (control). We find that the functional SAM does not affect the unspecific response of gold to pH and background ionic species. This represents a clear advantage of gold compared to oxide surfaces and makes it an ideal candidate for differential measurements.

Dual beam differential photopyroelectric setup for broadband thermal effusivity investigation of glass transitions in polymers

The behaviour of the thermal effusivity squared over the glass transition in polystyrene is measured over a considerable frequency range using a novel dual beam front detection photopyroelectric configuration, which ensures a very effective processing of the obtained signal. This has enabled the detection of the very small changes taking place in such a parameter, despite the non-favourable sensitivity conditions due to the large mismatch between the thermal effusivities of the pyroelectric transducer and of the sample. The effect of the thermal contact resistance between the sample and the pyroelectric detector is also considered and discussed.

Description of a differential setup for relaxation microcalorimetry

A specific heat measuring instrument, with the capacity for the application of magnetic fields up to 9 T, resorting to microcalorimetry chips from the company Xensor Integration, has been successfully assembled and its functioning specifications are reported in the current paper.With this instrument is it possible to perform specific heat measurements with applied magnetic fields up to 9 T in milligram samples. This offers our group the possibility to calculate the actual adiabatic temperature change of a material, as well as providing reliable and precise information on any phase transition that may be influenced by the application of a magnetic field.

Precision displacement interferometry with stabilization of wavelength on air

We present an interferometric technique based on differential interferometry setup for measurement in the subnanometer scale in atmospheric conditions. The motivation for development of this ultraprecise technique is coming from the field of nanometrology. The key limiting factor in any optical measurement are fluctuations of the refractive index of air representing a source of uncertainty on the 10 -6 level when evaluated indirectly from the physical parameters of the atmosphere. Our proposal is based on the concept of overdetermined interferometric setup where a reference length is derived from a mechanical frame made from a material with very low thermal coefficient on the 10 -8 level. The technique allows to track the variations of the refractive index of air on-line directly in the line of the measuring beam and to compensate for the fluctuations. The optical setup consists of three interferometers sharing the same beam path where two measure differentially the displacement while the third represents a reference for stabilization of the wavelength of the laser source. The principle is demonstrated on an experimental setup and a set of measurements describing the performance is presented.

Refractive Index Compensation in Over-Determined Interferometric Systems

We present an interferometric technique based on a differential interferometry setup for measurement under atmospheric conditions. The key limiting factor in any interferometric dimensional measurement are fluctuations of the refractive index of air representing a dominating source of uncertainty when evaluated indirectly from the physical parameters of the atmosphere. Our proposal is based on the concept of an over-determined interferometric setup where a reference length is derived from a mechanical frame made from a material with a very low thermal coefficient. The technique allows one to track the variations of the refractive index of air on-line directly in the line of the measuring beam and to compensate for the fluctuations. The optical setup consists of three interferometers sharing the same beam path where two measure differentially the displacement while the third evaluates the changes in the measuring range, acting as a tracking refractometer. The principle is demonstrated in an experimental setup.

A Portable Setup for Molecular Detection by Transmission LSPR

ABSTRACTIn the framework of bioanalytics and multiple array detection, we developed a fully portable and low-cost detection system based on Localized Surface Plasmon Resonance (LSPR) in a transmission configuration (T-LSPR). The transmission approach is suitable to be scaled to small dimension systems and to enable high-density array measurements on the same platform. Our setup is made out of off-the-shelf components and consists of a set of discrete light sources and a couple of light-detectors which enable a differential measurement setup. An algorithm fits the measured data and extracts the information of the plasmon peak position in the spectrum.The performance of our T-LSPR measurement system has been characterized on a set of Fluorinated Tin Oxide-coated glass slides covered with gold Nanoislands (NIs). The samples have been modified with a single-stranded DNA layer and a real-time DNA hybridization experiment has been performed. Here we demonstrate that the proposed T-LSPR device, based on the characterization of the plasmon peak with a differential approach, is able to monitor real-time DNA hybridization on surface, and to precisely measure the position of the peak with a standard deviation in wavelength of 0.2 nm.

Selective in situ functionalization of biosensors on LOC devices using laminar co-flow

Many applications involving lab-on-a-chip (LOC) devices are prevented from entering the market because of difficulties to achieve mass production and impart suitable properties allowing long-term storage. To integrate biosensors on these microfluidic chips, one of the main restrictions is the fabrication and stability of the molecular modifications that must be performed on the surfaces of the sensors for a given application. The complexity of the problem increases exponentially when the LOC integrates several of these sensors. Here we present a system based on laminar co-flow to perform an on-chip selective surface bio-functionalization of LOC-integrated sensors. This method has the advantage that the surface modification protocols are performed in situ before analyte detection. This approach reduces the burdens during LOC fabrication, keeping the required reagents stored outside of the detection structure in suitable wet conditions. The proof of concept is demonstrated through an optical characterization followed by electronic detection based on a novel differential impedance measurement setup. The system can be easily scaled to incorporate several sensors with distinct biosensing targets in a single chip.

A new differential thermal analysis setup for measuring high pressure phase transitions

A new setup has been recently developed in the toroidal opposed-anvil device ‘Conac 40’ to perform differential thermal analysis in a high pressure range (0–6 GPa). To evaluate the precision and the reliability of the setup, the high pressure melting curve of germanium and the transition points of α-iron have been investigated up to 5.3 GPa and compared with previous results.

Heat of reaction measurements for hydrothermal carbonization of biomass

This paper presents a set of calorimetric measurements with the aim of better understanding the calorific nature of hydrothermal carbonization. Presented values so far show an inadequately high scatter to do so, preventing a well funded assessment of the energetic feasibility of this process. The heat released during hydrothermal carbonization at 240 °C measured with the applied differential calorimetry setup is −1.06 MJ/kg glucose,daf with a standard deviation of 14%, −1.07 MJ/kg cellulose,daf with a standard deviation of 9%, and −0.76 MJ/kg wood,daf with a standard deviation of 32%. These results are in good agreement with the theoretically derived maximum heat release. Despite the comparably high experimental standard deviation of these results, their accuracy is considerably higher than previously published results.

Differential Setup of Light-Addressable Potentiometric Sensor with an Enzyme Reactor in a Flow Channel

Differential Setup of Light-Addressable Potentiometric Sensor with an Enzyme Reactor in a Flow Channel

Differential Setup of Light-Addressable Potentiometric Sensor with an Enzyme Reactor in a Flow Channel

The light-addressable potentiometric sensor (LAPS) was combined with an enzyme reactor in a fluidic channel. The fluidic channel was mounted on the sensor plate and the enzyme reactor was connected to the fluidic channel. The enzyme reactor was filled with glass beads as enzyme carrier modified by urease which catalyzed production of ammonia depending on the concentration of urea. Double-channel LAPS measurement was performed at the both side of upper and lower stream of the enzyme reactor which realized a differential measurement and eliminated the drift component of the measurement.

Experimental research of wave resistance resonance for rough-wall plane channels

We experimentally confirmed the effect when the wave resistance of rough-wall plane channels, generated while the walls are streamlined by a supersonic gas flow, reaches the extreme values. The experiments were conducted on a differential setup by comparing the tests of flat and round sonic nozzles. The results of the experiment justified the developed method of calculating the wave resistance of the plane channel with sawtooth wall relief.

EVALUATION OF A PROPOSED CHANNEL ON CIRCULATION AND MORPHOLOGY CHANGE AT KAWAIHAE HARBOR AND PELEKANE BAY, HAWAII, USA

In an effort to improve the water quality and restore marine habitats in Pelekane Bay (PB), installation of a circulation channel was proposed with the intent of enhancing water circulation in PB through Kawaihae Deep Draft Harbor (KDDH) and flushing accumulated sediment out of PB. This study was conducted to investigate the hydraulics and sediment transport consequences of dredging such a channel. The coupled wave, flow, and sediment transport Coastal Modeling System (CMS) was applied during a non-storm and a typical winter (storms) time interval. CMS results were analyzed and compared between existing condition and channel alternatives. It was found that upon reaching PB, incident waves breaking induces higher water level from wave setup, whereas the breakwater at KDDH inhibits depth-limited breaking and setup, creating a differential in water surface elevation (WSE). The water level rise along the channel was calculated to be 0.01-0.03 m, with WSE in PB being higher. The differential wave setup, found for almost all wave conditions, produces water flow from PB to KDDH in the proposed channel. The temporally averaged along-channel current speed is calculated from 0.07 to 0.2 m/sec for the non-storm and storm conditions, respectively. Bay-to-harbor flows will move sediment into the channel, most of which is deposited within 120 m from PB. For the winter storm conditions, the maximum deposition in the channel was calculated to be approximately between 0.7 and 2.0 m among the different alternatives. More sand is deposited under the deeper channel alternatives. The channel or bay blockage appears under all channel alternatives before reaching the end of the simulation.

Surface deformation of an intraplate area from GPS time series

The aim of this study is to identify the processes that lead to the ground surface deformation above the fractured crystalline aquifer of Ploemeur (French Brittany). We conducted a four-year continuous GPS data survey in order to extract the hydrogeological contribution due to the variations of the hydraulic head of the confined aquifer. The GPS configuration used in this study, with a differential setup, short baselines and adapted processing parameters, may have removed tide effects, ocean tide loading and tectonics trends. We checked in particular the case of ocean tide loading because of its important contribution in Brittany. Time series calculated with GAMIT software indicate a seasonal deformation on both vertical direction (up to 16 mm of displacement) and horizontal plane (from 3 to 12 mm of displacement) that provide a 3D motion. This sub-annual deformation is induced by variations of the hydraulic head of the aquifer and depends on its 3D hydromechanical properties. However, an offset between ground uplift and piezometric rise could not be explained by pressure variations into the deep aquifer and was linked to the variations of the hydrous state of the ground. This GPS study highlights that the hydrogeological and hydrological processes act significantly on ground motion and should be integrated in any Earth deformation survey.

Development of a Motor-Based Differential Settlement Simulator Setup for a Geotechnical Centrifuge

Abstract This paper presents the design details of a motor-based differential settlement simulator (MDSS) setup for inducing differential settlement in a high gravity environment. The MDSS setup comprises of a motor, controller, screw jack, central platform, gear trains, connecting shaft, and bearings. Various features of the MDSS setup along with its design procedure are described. Calibration and performance tests were performed in a large beam geotechnical centrifuge facility available at Indian Institute of Technology Bombay for inducing differential settlement using the MDSS setup. A design chart was developed for obtaining prototype settlement rates from the speed of the motor and gravity level. The usage of this setup in assessing the deformation behavior of the clay barrier of landfill cover system under various settlement rates is briefly illustrated. The versatility of the developed setup for the applications involving ground loss or boundary displacement problems is highlighted.

Validation of a differential in situ perfusion method with mesenteric blood sampling in rats for intestinal drug interaction profiling

The present study explored the feasibility of a differential setup for the in situ perfusion technique with mesenteric cannulation in rats to assess drug interactions at the level of intestinal absorption. In contrast to the classic, parallel in situ perfusion setup, the differential approach aims to identify intestinal drug interactions in individual animals by exposing the perfused segment to a sequence of multiple conditions. First, the setup was validated by assessing the interaction between the P-glycoprotein (P-gp) inhibitor verapamil and the transport probes atenolol (paracellular transport), propranolol (transcellular) and talinolol (P-gp mediated efflux). While transport of atenolol and propranolol remained constant for the total perfusion time (2 h), a verapamil-induced increase in talinolol transport was observed within individual rats (between 3.2- and 5.2-fold). In comparison with the parallel setup, the differential in situ perfusion approach enhances the power to detect drug interactions with compounds that exhibit strong subject-dependent permeability. This was demonstrated by identifying an interaction between amprenavir and ketoconazole (P-gp and CYP3A inhibitor) in five out of seven rats (permeability increase between 1.9- and 4.2-fold), despite high inter-individual differences in intrinsic permeability for amprenavir. In combination with an increased throughput (up to 300%) and a reduced animal use (up to 50%), the enhanced power of the differential approach improves the utility of the biorelevant in situ perfusion technique with mesenteric blood sampling to elucidate the intestinal interaction profile of drugs and drug candidates.