Diagonal Profile Research Articles

Ribbon-like Nickel Cobaltite with Layer-by-Layer-Assembled Ordered Nanocrystallites for Next-Generation All-Solid-State Hybrid Supercapatteries.

In the context to develop ultra-efficient electrode materials with good physicoelectrochemical and electrostructural properties, for their application in high-performance supercapatteries, herein, a facile tartrate-mediated inhibited crystal growth method is reported to engineer thoroughly uniform ribbon-like nickel cobaltite (NiCo2O4) microstructure with unique layer-by-layer-assembled nanocrystallites. This material demonstrates significant kinetic reversibility, good rate efficiency and bulk diffusibility of the electroactive ions, and a predominant semi-infinite diffusion mechanism during the redox-based charge storage process. This material also shows bias-potential-independent equivalent series resistance, very low charge-transfer resistance, and diagonal Warburg profile, corresponding to the ion diffusion occurring during the electrochemical processes in supercapacitors and batteries. Further, the fabricated NiCo2O4-based all-solid-state supercapattery (NiCo2O4||N-rGO) delivers excellent rate-specific capacity, very low internal resistance, good electrochemical and electrostructural stability (∼94% capacity retention after 10,000 charge-discharge cycles), energy density (31 W h kg-1) of a typical rechargeable battery, and power density (13,003 W kg-1) of an ultra-supercapacitor. The ultimate performance of the supercapattery is ascribed to low-dimensional crystallites, ordered inter-crystallite and channel-type bulk and boundary porosity, multiple reactive equivalents, enhanced electronic conductivity, and "ion buffering pool" like behavior of ribbon-like NiCo2O4, supplemented with enhanced electronic and ionic conductivities of N-doped rGO (negative electrode) and PVA/KOH gel (electrolyte separator), respectively.

An Effective Correction Method for AFM Image Distortion due to Hysteresis and Thermal Drift

Hysteresis and thermal drift cause image distortion of atomic force microscopy (AFM). To address this issue, a hysteresis compensation algorithm based on B-spline curve fitting is first designed to correct the image distortion due to hysteresis, so as to provide a basis for further thermal drift correction. Afterward, a novel off-line drift correction algorithm based on cross diagonals' scanning is proposed to reconstruct high-quality AFM images. More precisely, according to the distorted image and the leading diagonal profile obtained by initial scanning, the drift is first calculated by template matching with an increasing sliding window. Furthermore, since the calculated drift contains a part of incorrect data, an adaptive filter is designed to generate more accurate horizontal thermal drift, based on which an undistorted image is constructed by bilinear interpolation. Finally, the performance of the proposed method is verified by convincing experimental and application results. Compared with online correction methods, the proposed approach is easier to implement since it does not require hardware improvement. Besides, compared with other off-line methods, the proposed method is simpler with less time consumption since it only needs two additional scanning lines to correct image distortion.

RAPID RADIOMETRIC CALIBRATION OF MULTIPLE CAMERA ARRAY USING IN-SITU DATA FOR UAV MULTISPECTRAL PHOTOGRAMMETRY

Abstract. This study compares two possible radiometric calibration approaches of Tetracam μMCA Snap multispectral camera using the Dark offset subtraction and Look-Up Table (LUT) methods. A laboratory-based calibration using correction images taken under the controlled conditions was compared with a rapid in-situ based calibration featuring correction images taken during the field campaign. The hypothesis was that the accuracy of in-situ calibration could be comparable with the laboratory calibration, and thus could replace it and simplify the radiometric calibration process. The accuracy of calibration approaches was assessed by comparison of three validation targets reflectance values extracted from corrected UAV images based on laboratory and in-situ calibration with a reference spectroscopy measurement. The results of the field experiment showed that both calibration approaches led to significant accuracy improvement compared to raw data. The vignetting correction using resulted in a significant reduction of the Coefficient of variation by half in all bands and overall equalizing the DNs on the selected diagonal profile. The NRMSEs after processing all corrections ranged from 0.24 to 3.40%. Although the statistical testing revealed slightly better agreement of laboratory calibrated reflectance with reference data, the accuracy of in-situ calibration is sufficient, because the accuracy improvement quantified by the NRMSE is 2–10 times better using both calibration approaches compared to raw data than the NRMSE differences between them. These findings make the proposed in-situ approach usable for various environmental studies featuring UAV multispectral photogrammetry.

Multidimensional Cross-Recurrence Quantification Analysis (MdCRQA) – A Method for Quantifying Correlation between Multivariate Time-Series

In this paper, Multidimensional Cross-Recurrence Quantification Analysis (MdCRQA) is introduced. It is an extension of Multidimensional Recurrence Quantification Analysis (MdRQA), which allows to quantify the (auto-)recurrence properties of a single multidimensional time-series. MdCRQA extends MdRQA to bi-variate cases to allow for the quantification of the co-evolution of two multidimensional time-series. Moreover, it is shown how a Diagonal Cross-Recurrence Profile (DCRP) can be computed from the MdCRQA output that allows to capture time-lagged coupling between two multidimensional time-series. The core concepts of these analyses are described, as well as practical aspects of their application. In the supplementary materials to this paper, implementations of MdCRQA and the DCRP as MatLab- and R-functions are provided.

Rapid acceptance testing of modern linac using on-board MV and kV imaging systems.

The purpose of this study was to develop a novel process for using on-board MV and kV Electronic Portal Imaging Devices (EPIDs) to perform linac acceptance testing (AT) for two reasons: (a) to standardize the assessment of new equipment performance, and (b) to reduce the time to clinical use while reducing physicist workload. In this study, Varian TrueBeam linacs equipped with amorphous silicon-based EPID (aS1000) were used. The conventional set of AT tests and tolerances were used as a baseline guide. A novel methodology was developed or adopted from published literature to perform as many tests as possible using the MV and kV EPIDs. The developer mode on Varian TrueBeam linacs was used to automate the process. In the EPID-based approach, most of mechanical tests were conducted by acquiring images through a custom phantom and software tools were developed for quantitative analysis to extract different performance parameters. The embedded steel-spheres in a custom phantom provided both visual and radiographic guidance for beam geometry testing. For photon beams, open field EPID images were used to extract inline/crossline profiles to verify the beam energy, flatness and symmetry. EPID images through a double wedge phantom were used for evaluating electron beam properties via diagonal profile. Testing was augmented with a commercial automated application (Machine Performance Check) which was used to perform several geometric accuracy tests such as gantry, collimator rotations, and couch rotations/translations. The developed process demonstrated that the tests, which required customer demonstration, were efficiently performed using EPIDs. The AT tests that were performed using EPIDs were fully automated using the developer mode on the Varian TrueBeam system, while some tests, such as the light field versus radiation field congruence, and collision interlock checks required user interaction. On-board imagers are quite suitable for both geometric and dosimetric testing of linac system involved in AT. Electronic format of the acquired data lends itself to benchmarking, transparency, as well as longitudinal use of AT data. While the tests were performed on a specific model of a linear accelerator, the proposed approach can be extended to other linacs.

SU‐F‐T‐276: Source Modeling and VMAT Quality Assurance Referring to the TrueBeam Representative Beam Data for Eclipse

Purpose:To study quality assurance (QA) of volumetric modulated arc therapy (VMAT) after the 6MV and 10MV photon beam source modeling, referring to the Varian TrueBeam representative beam data for Eclipse.Methods:The source model needs specific measured beam data, such as PDDs and profiles, diagonal profile, output factors (OFs), and MLC transmission factor (TF) and dosimetric leaf gap (DLG), et al. We downloaded the representative data from myVarian website, which includes TrueBeam 4MV‐15MV photon beam data and 6MeV‐22MeV electron beam data in w2CAD file format for use with Eclipse and in Excel spreadsheet format for use in data comparison. The beam data in W2CAD format can be imported into the Eclipse system and calibrated for use, as appropriate. We used PTW MP3 water tank to measure the beam data in some typical field sizes, and compared the measured data with the representative data. We found that the PDDs, profiles and OFs are similar. However according to some papers and our measurements, we decided that our MLC TF and DLG are 1.58 and 1.33 (6MV), 1.79 and 1.57 (10MV), respectively. After we had configured the anisotropic analytical algorithm (AAA) with the representative data in Eclipse, we also have done dosimetric verification for 88 VMAT plans.Results:The end‐to‐end test procedures of VMAT were performed for 6MV and 10MV energy modes. The NE Farmer ion chamber mean measurements showed 1.2% (6MV, 38 cases) and 1.2% (10MV, 50 cases) between measurement and calculation; the Sun Nuclear ArcCheck mean measurements demonstrated gamma pass rates are as followings: 98.9%, 93.2%, 61.0% for 6MV, and 98.9%, 91.9%, 59.5% for 10MV, using 3%/3mm, 2%/2mm, 1%/1mm, 10% threshold criteria, respectively.Conclusion:The representative data is applicable to our TrueBeam for the VMAT plan, though our MLC factors are a little different, and its patientspecific QA is good.

SU-E-T-190: First Integration of Steriotactic Radiotherapy Planning System Iplan with Elekta Linear Accelerator

Purpose: : For the first time in the world, BrainLAB has integrated its iPlan treatment planning system for clinical use with Elekta linear accelerator (Axesse with a Beam Modulator). The purpose of this study was to compare the calculated and measured doses with different chambers to establish the calculation accuracy of iPlan system. Methods: The iPlan has both Pencil beam (PB) and Monte Carlo (MC) calculation algorithms. Beam data include depth doses, profiles and output measurements for different field sizes. Collected data was verified by vendor and beam modelling was done. Further QA tests were carried out in our clinic. Dose calculation accuracy verified point, volumetric dose measurement using ion chambers of different volumes (0.01cc and 0.125cc). Planner dose verification was done using diode array. Plans were generated in iPlan and irradiated in Elekta Axesse linear accelerator. Results: Dose calculation accuracies verified using ion chamber for 6 and 10 MV beam were 3.5+/-0.33(PB), 1.7%+/-0.7(MC) and 3.9%+/-0.6(PB), 3.4%+/-0.6(MC) respectively. Using a pin point chamber, dose calculation accuracy for 6MV and 10MV was 3.8%+/-0.06(PB), 1.21%+/-0.2(MC) and 4.2%+/-0.6(PB), 3.1%+/-0.7(MC) respectively. The calculated planar dose distribution for 10.4×10.4 cm2 was verified using a diode array and the gamma analysis for 2%-2mm criteria yielded pass rates of 88 %(PB) and 98.8%(MC) respectively. 3mm-3% yields 100% passing for both MC and PB algorithm. Conclusion: Dose calculation accuracy was found to be within acceptable limits for MC for 6MV beam. PB for both beams and MC for 10 MV beam were found to be outside acceptable limits. The output measurements were done twice for conformation. The lower gamma matching was attributed to meager number of measured profiles (only two profiles for PB) and coarse measurement resolution for diagonal profile measurement (5mm). Based on these measurements we concluded that 6 MV MC algorithm is suitable for patient treatment.

SU-E-T-156: Robust Algorithms for Correction of Predicted Electronic Portal Imager Response.

Predicted electronic portal imaging device (EPID) response, as calculated by a commercial treatment planning system (TPS), is up to 15% lower than measured EPID response for off-axis IMRT fields. Two original algorithms are presented to correct for EPID prediction errors. The EPID prediction algorithm and a recent image-to-dose conversion algorithm are each tested for ability to identify TPS dose calculation errors. By comparing test images to respective predictions, correction factors were calculated to modify the EPID diagonal calibration profile (applied via radial symmetry). Secondly, image/prediction comparisons were used to compute a 2D correction matrix for EPID predictions, to account for radially-asymmetric errors. Over 50 IMRT fields of varying complexity were tested with each correction technique, and with a diode array. Absolute dose and beam-profile errors were separately induced into the TPS and a number of IMRT plans were recalculated and measured with three systems - an EPID prediction system, an EPID image-to-dose conversion system, and a diode array - for comparison to verification plans. With the profile correction, TPS predictions agree much better with EPID measurements, yielding improvement in gamma pass rates (3%,3mm) of over 30% on average for off-axis IMRT fields. Since off-axis prediction errors are not radially-symmetric, the matrix correction further improves pass rates by 5% on average (up to 30%) for fields where the profile correction is limited. The EPID prediction system was unable to catch either induced TPS error, while both the image-to-dose conversion system and the diode array indicated both errors. Profile correction is effective and efficient though approximate, due to radial symmetry. The matrix correction is comprehensive but requires computational manipulation of DICOM images. Users must be aware that EPID prediction systems may be unable to catch delivered IMRT inaccuracies due to calculation errors downstream from the actual fluence calculation.

SU-E-T-164: Clinical Implementation of ASi EPID Panels for QA of IMRT/VMAT Plans.

To investigate various issues for clinical implementation of aSi EPID panels for IMRT/VMAT QA. Six linacs are used in our clinic for EPID-based plan QA; two Varian Truebeams, two Varian 2100 series, two Elekta Infiniti series. Multiple corrections must be accounted for in the calibration of each panel for dosimetric use. Varian aSi panels are calibrated with standard dark field, flood field, and 40×40 diagonal profile for beam profile correction. Additional corrections to account for off-axis and support arm backscatter are needed for larger field sizes. Since Elekta iViewGT system does not export gantry angle with images, a third-party inclinometer must be physically mounted to back of linac gantry and synchronized with data acquisition via iViewGT PC clock. A T/2 offset correctly correlates image and gantry angle for arc plans due to iView image time stamp at the end of data acquisition for each image. For both Varian and Elekta panels, a 5 MU 10×10 calibration field is used to account for the nonlinear MU to dose response at higher energies. Acquired EPID images are deconvolved via a high pass filter in Fourier space and resultant fluence maps are used to reconstruct a 3D dose 'delivered' to patient using DosimetryCheck. Results are compared to patient 3D dose computed by TPS using a 3D-gamma analysis. 120 IMRT and 100 VMAT cases are reported. Two 3D gamma quantities (Gamma(V10) and Gamma(PTV)) are proposed for evaluating QA results. The Gamma(PTV) is sensitive to MLC offsets while Gamma(V10) is sensitive to gantry rotations. When a 3mm/3% criteria and 90% or higher 3D gamma pass rate is used, all IMRT and 90% of VMAT QA pass QA. After appropriate calibration of aSi panels and setup of image acquisition systems, EPID based 3D dose reconstruction method is found clinically feasible.

A Scheme of Concealment and Transmission of Secret Information in Text Files

Abstract A common method to transfer a secret information is encrypting the secret information before transmission. However, most cipher texts are incomprehensible which attracts more attackers. A better scheme is to hide the secret information in a common document and to transfer it in common channel. The sender encrypts the secret information before the cipher text is embedded into a text file based on the characteristics of line and diagonal profile of the text documents. Then, the sender embeds the factors to encrypt the cipher text as a double-watermark into the seal image based on DCT and LSB algorithms. The receiver extracts and recovers the secret information from the text file and the seal image. The system of the Identity based on Encryption is the basis of the communication between the sender and the receiver.

Determination of concrete fracture parameters based on peak-load method with diagonal split-tension cubes

Using the boundary element method, unnotched and notched split tension-cubes were analyzed by applying compressive forces in the diagonal planes. The maximum tensile stress of the unnotched diagonal cubes and the linear elastic fracture mechanics formulas of the notched diagonal cubes, KI, CMOD and COD profile, were determined for different load-distributed widths. Subsequently, to investigate the extent to which the diagonal split-cube tests could simulate the fracture behavior of concrete, four series of tests were performed. Finally, the advantages of diagonal splitting cubes are discussed in comparison to other splitting specimens.

SU-FF-T-207: An Effective Correction Algorithm For Off-Axis Portal Dosimetry Errors

Purpose: Portal dosimetric images acquired for IMRT pretreatment verification show dose over‐response of up to 15% with increasing off‐axis position, compared to TPS portal dose predictions. Quality assurance measurements with other standards (e.g. diode arrays, ion chambers) verify these IMRT fluences are delivered accurately. This work explores an effective, highly useable correction algorithm accounting for TPS/EPID disagreements. Method and Materials: By creating test fields of various sizes and positions, then comparing acquired vs. predicted dose, correction factors were determined to precisely modify the diagonal calibration profile utilized in calibrating the EPID for absolute dosimetry. Because the diagonal profile modifications need be calculated only once, then applied during each dosimetrycalibration, this correction algorithm is both straightforward and efficient. With the modified calibration, portal dose images were acquired for IMRT fluences varying in size, position, and complexity (70 fields total) to verify the accuracy of the correction, independent of these parameters. These methods were completed for both 6 MV and 23 MV beams. Results: Along the major diagonal, EPID over‐response increases linearly with off‐axis distance, from 1.7% at 10.0 cm to 7.1% at 17.5 cm for the 6 MV beam, and 2.1% at 4.5 cm to 11.7% at 16.5 cm for the 23 MV beam. Before correction, gamma evaluation (3mm, 3%) for asymmetric fields results in only 69.5% passing points on average. After applying the correction algorithm, pass rates for the same fields improve by up to 60%, to an average of 98.5% passing points. Conclusions: This correction algorithm is effective and convenient, producing excellent agreement between TPS predictions and EPID measurements in most regions of the detector. Because the diagonal calibration profile is applied by circular symmetry, this algorithm does not account for over‐response in those regions of the detector with high backscatter from non‐uniform components below the imager.

Seismic Damage Characteristics of RC Shear Wall with Diagonal Profile Steel Braces by Experiment

This paper focuses on an experimental investigation and theoretical analysis of different types of RC shear wall with the profile steel braces in two side columns and diagonal profile steel braces of walls subjected to applied repeated cyclic loads. Fifteen RC shear walls with different shear span ratio are tested and their aseismic charactertics are studied. The effect of profile steel bracings on failure property, bearing capacity, ductility and hysteretical characteristic of shear wall is investigated based on experimental results. It is shown that adding the profile steel braces on the boundary column and inner of walls can obviously enhance the ultimate strength of specimens and improve their aseismic characteristics. Finally, the mechanical model of the shear wall is presented and the formulae for calculating the load-carrying capacity are developed. Numerical analyses indicate that the theoretical results agree well with those from experiments.

SU‐FF‐T‐325: Modifying the BEAMnrc Phase‐Space to Match Monte Carlo and Measured Dose Distributions

Purpose: To present a method for improving agreement between clinically measured and Monte Carlo (MC) calculated dose distributions (profiles and PDDs) in water for the full range of field sizes. Method and Materials: Linac beam characteristics are modeled using BEAMnrc code that produces particle phase space above the secondary collimators as a new “source” in MC calculations. We assume that the photon energy spectra, represented in the phase space as achieved by the BEAMnrc model and electron beam characteristics, are reasonably accurate. The 3D dose distributions generated from MC and measured data are then used to modify the weights of each particle in the phase‐space. The weight modification occurs through a few (typically 3) iterations and new weights are proportional to the ratio of the measures to MC calculated dose at a point where primary photon crosses the dose matrix plane. One‐dimensional (assuming radial symmetry), 2D and 3D correction techniques were investigated. Denoising of the modified phase space has also been performed to reduce the “latent” dose uncertainty. Results: The method has been applied to our 6 MV and 18 MV beam models and allowed to reduce MC/measured beam profile differences from ∼3% to less than 1% for 6 MV beam, and from ∼5% to ∼1% for 18 MV in the central region of the beam. It also reduced the difference between measured and calculated dose from over 15% to less than 3% in the penumbra of the diagonal profile of the 40 × 40 cm2 field. Conclusion: The developed technique provides a relatively simple alternative to a very time‐consuming process of fine‐tuning BEAMnrc parameters. Initial BEAM model has to be “reasonably accurate” (producing results within ∼5% agreement to measured data) prior to correction. 2D correction technique showed optimal performance providing required dose agreement and performing fasted than 3D correction.

광산란 거친표면의 고정밀 삼차원 형상 측정을 위한 점회절 간섭계

최근 전자산업계에 새롭게 널리 생산되는 마이크로 전자부품들은 왜곡이 최소화된 정밀한 외관 형상을 갖도록 제조되고 관리되지만, 측정 대상의 표면이 가시광 영역에서 광산란되는 특징을 가짐으로 인해, 기존의 피죠나 마이켈슨 형태의 비교간섭법으로는 고정밀의 삼차원 형상측정이 용이하지 아니하였다. 본 논문에서는 광섬유를 이용한 새로운 개념의 점회절 간섭계를 제안하고, 이를 광산란 거친표면의 대표적인 제품인 칩패키지와 실리콘 웨이퍼의 삼차원 형상 측정에 적용하였다. 측정결과 66 mm 측정영역에서 측정 형상오차 PV(peak-to-valley value) 5.6 <TEX>$\mu\textrm{m}$</TEX>, 분산값(<TEX>$\sigma$</TEX>) 1.5 <TEX>$\mu\textrm{m}$</TEX>를 획득함으로써 기존의 비교 간섭 측정법에 비해 더욱 향상된 측정 정밀도를 획득하였다. We present a new point-diffraction interferometer, which has been devised for the three-dimensional profile measurement of light scattering rough surfaces. The interferometer system has multiple sources of two-point-diffraction and a CCD camera composed of an array of two-dimensional photodetectors. Each diffraction source is an independent two-point-diffraction interferometer made of a pair of single-mode optical fibers, which are housed in a ceramic ferrule to emit two spherical wave fronts by means of diffraction at their free ends. The two spherical wave fronts then interfere with each other and subsequently generate a unique fringe pattern on the test surface. A He-Ne source provides coherent light to the two fibers through a 2<TEX>${\times}$</TEX>l optical coupler, and one of the fibers is elongated by use of a piezoelectric tube to produce phase shifting. The xyz coordinates of the target surface are determined by fitting the measured phase data into a global model of multilateration. Measurement has been performed for the warpage inspection of chip scale packages (CSPs) that are tape-mounted on ball grid arrays (BGAs) and backside profile of a silicon wafer in the middle of integrated-circuit fabrication process. When a diagonal profile is measured across the wafer, the maximum discrepancy turns out to be 5.6 <TEX>${\mu}{\textrm}{m}$</TEX> with a standard deviation of 1.5 <TEX>${\mu}{\textrm}{m}$</TEX>.

Conformational preferences and vibrational frequency distributions of short peptides in relation to multidimensional infrared spectroscopy.

Molecular dynamics simulations of the structural distributions and the associated amide-I vibrational modes are carried out for dialanine peptide in water and carbon tetrachloride. The various manifestations in nonlinear-infrared spectroscopic experiments of the distributions of conformations of solvated dialanine are examined. The two-dimensional infrared (2D-IR) spectrum of dialanine exhibits the coupling between the amide oscillators and the correlations of the frequency fluctuations. An internally hydrogen-bonded conformation exists in CCl(4) but not in H(2)O where two externally hydrogen-bonded forms are preferred. Simulations of solvated dialanine show how the 2D-IR spectra expose the underlying structural distributions and dynamics that are not deducible from linear-infrared spectra. In H(2)O the 2D-IR shows cross-peaks from large coupling in the alpha-helical conformer and an elongated higher frequency diagonal peak, reflecting the broader distribution of structures for the more flexible acetyl end. In CCl(4), the computed cross-peak portion of the 2D-IR shows evidence of two amide-I transitions in the high-frequency region which are not apparent from the diagonal peak profile. The vibrational frequency inhomogeneity of the amide-I band arises from fluctuations of the instantaneous normal modes of these conformers rather than the shifts induced by hydrogen bonding. The simulation shows that there are correlations between fluctuations of the acetyl and amino end frequencies in H(2)O that arise from mechanical coupling and not from hydrogen bonding at the two ends of the molecule. The angular relationships between the two amide units which also show up in 2D-IR were computed, and spectral manifestations of them are discussed. The simulations also permit a calculation of the rate of energy transfer from one side of the molecule to the other. From these calculations, 2D-IR spectroscopy in conjunction with simulations is seen to be a promising tool for determining dynamics of structure changes in dipeptides.

Reconstruction of an approximately complete Quaternary Tibetan inland glaciation between the Mt. Everest- and Cho Oyu Massifs and the Aksai Chin. A new glaciogeomorphological SE–NW diagonal profile through Tibet and its consequences for the glacial isostasy and Ice Age cycle

Studies were done on new geomorphological and quaternary-geological profiles through representative reliefs of Tibet from the Central Himalaya as far as the Kuenlun. Thus, further detailed investigations on the prehistoric glaciation could be carried out. Youngest historical to neoglacial ice margin positions could be recorded. Their mapping took place in a downward direction from the modern glacier margins. They confirm snow line (ELA) depressions from decametres up to ca. 100–250 m. At distances of several kilometres to many decakilometres (depending on the relief) from the modern glaciers, neve shields and perennial snow fields, end moraines and later just remnants of lateral moraines and kame complexes of the Late Glacial (ca. Stadia IV-II) have been localized in an increasing disrupted succession and samples have been taken. The recorded, inter- and extrapolated lowest ice margin positions allowed the reconstruction of accompanying depressions of the snow line which, due to the altitude of the Tibetan plateau plains, attained a maximum of 400–700 m. Accordingly, the early Late Glacial (Stadia I to II) and High Glacial glacier traces (Riss or pre-LGM and Wurm or LGM = Stadia −I and/or 0) occurred over a horizontal distance of 1620 km across the plateau with an average height of 4700 m asl without showing the key forms of ice margin positions. From the profiles introduced here, running from Mt. Everest/Cho Oyu (Central Himalaya) in the SE via Gertse (Kaitse; Central Tibet) as far as the Lingzi Thang and Aksai Chin and from there into the Kuenlun, as well as from a parallel section of the Gurla Mandhata (central S Tibet) to the currently very arid Nako Tso, located centrally in the W, sediment samples have been analysed which provide evidence for a ground moraine genesis. Thus, the macroscopic field observations are confirmed. Only the relatively small basin of Shiquanha (Ali) – like the Indus valley chamber of Leh – may have been free of ice during the High Glacial (LGM). Forms of glacial horns, as well as roches moutonnees and large, several metres-high round-polished mountain ridges with slight debris covers, flank polishings, abraded mountain spurs at intermediate valley ridges and high-lying erratics document the widespread ice cover. Important ice thicknesses of at least 1300–1400 m have been recognized by means of transfluences. Especially by and in the Nako Tso (lake) the limnic undercutting of roches moutonnees provides evidence only of a postglacial filling into a primary glacial relief. The glacial ice cover (with the LGM at the end) testified here for a further area of Tibet, is the foundation of the relief-specific hypothesis on the development of the Ice Ages, based on the global radiation geometry: accordingly, the last great geological event, the early Pleistocene plate-tectonically induced uplift of Tibet above the snow line, has brought about a glaciation which, owing to its high albedo, reflected the subtropical radiation energy into space, so that it could not be exploited for the heating of the atmosphere. This may have triggered the Ice Ages. The repeated interglacial warming-up is to be reduced to the positive radiation anomalies by the variations of the parameters of the earth's orbit – which take place rhythmically – and the overlying glacio-isostatic lowering of Tibet and the other inland ice areas.

Asymmetries in electron Compton profiles of silicon — a coherence effect

Electron Compton scattering in crystals in the case of large Ewald spheres is treated both theoretically and experimentally. The incident and scattered probe electron is represented by a sum of Bloch waves in the crystal leading to interference terms in the scattering cross section. The interference terms show a shift towards lower energies with respect to the diagonal Compton profile which depends only on the reciprocal lattice vectors of the excited Bragg reflexions. For a symmetric two-beam case the expression for the cross section is evaluated and it is shown that in contrast to the case of a small Ewald sphere the interference terms cannot be extracted from an experiment. For silicon the cross section is evaluated numerically for a (220) two-beam case and compared to experimental data from a transmission electron microscope. The agreement between theory and experiment is excellent and the shift of the interference terms with respect to the diagonal Compton profile can be observed in the measured profile.

Flatness characteristics for diagonal scans from Varian and Siemens linear accelerators

The advent of 3D treatment planning systems whose algorithms utilize diagonal scan data to perform dose calculations has made the collection of diagonal profile data essential. Manufacturers' specifications (MS) on beam flatness and symmetry apply to both the radial and transverse axes of all square field sizes from 10 × 10 cm 2 to the largest field available. Beam profile measurements were obtained for both diagonal axes over a range of field sizes and depths for two units, a Varian 2100C and a Siemens KD. In this note the International Electrotechnical Commission (IEC) flatness definition was used to characterize the diagonal flatness of each beam.