High Degree Of Modulation Research Articles

Investigation into the Modulation Characteristics of Motor Current Signals in a Belt Transmission System for Machining Monitoring

Belt transmission is one of the most common forms of transmission on CNC lathes. To assess the impact of belt performance on monitoring machining conditions using motor current signal analysis, we developed a dynamic model for belt-driven electromechanical spindle systems. This model enables the coupling of multi-physics variables including mechanical dynamics, particularly the dynamic axil and belt bending motions of belt transmissions and electromagnetic effects. Thus, various changes in belt transmission, including different degrees of belt tension and defects with inherent motor and spindle errors, can be investigated. The modulation characteristics of the current and speed signals revealed that belt transmission can cause a high degree of modulation, reflected by the rich harmonic sidebands at the belt-passing frequency in the motor current spectrum. The rate and extent of belt wear worsened with excessive wear and inadequate tension. It was confirmed that the sideband at the spindle rotating frequency was slightly impacted by changes in the belt conditions. This model was verified based on a CNC lathe induced with different degrees of belt looseness. These conclusions drawn from the numerical analyses can be used for motor current signal analysis, providing reliable and accurate results for machining monitoring.

Direct Charge Trapping Multilevel Memory with Graphdiyne/MoS2 Van der Waals Heterostructure.

Direct charge trapping memory, a new concept memory without any dielectric, has begun to attract attention. However, such memory is still at the incipient stage, of which the charge‐trapping capability depends on localized electronic states that originated from the limited surface functional groups. To further advance such memory, a material with rich hybrid states is highly desired. Here, a van der Waals heterostructure design is proposed utilizing the 2D graphdiyne (GDY) which possesses abundant hybrid states with different chemical groups. In order to form the desirable van der Waals coupling, the plasma etching method is used to rapidly achieve the ultrathin 2D GDY with smooth surface for the first time. With the plasma‐treated 2D GDY as charge‐trapping layer, a direct charge‐trapping memory based on GDY/MoS2 is constructed. This bilayer memory is featured with large memory window (90 V) and high degree of modulation (on/off ratio around 8 × 107). Two operating mode can be achieved and data storage capability of 9 and 10 current levels can be obtained, respectively, in electronic and opto‐electronic mode. This GDY/MoS2 memory introduces a novel application of GDY as rich states charge‐trapping center and offers a new strategy of realizing high performance dielectric‐free electronics, such as optical memories and artificial synaptic.

Dosimetric comparison of dynamic conformal arc integrated with segment shape optimization and variable dose rate versus volumetric modulated arc therapy for liver SBRT.

The aim is a dosimetric comparison of dynamic conformal arc integrated with the segment shape optimization and variable dose rate (DCA_SSO_VDR) versus VMAT for liver SBRT and interaction of various treatment plan quality indices with PTV and degree of modulation (DoM) for both techniques. Twenty-five patients of liver SBRT treated using the VMAT technique were selected. DCA_SSO_VDR treatment plans were also generated for all patients in Monaco TPS using the same objective constraint template and treatment planning parameters as used for the VMAT technique. For comparison purpose, organs at risk (OARs) doses and treatment plans quality indices, such as maximum dose of PTV (Dmax%), mean dose of PTV (Dmean%), maximum dose at 2 cm in any direction from the PTV (D2cm%), total monitor units (MU's), gradient index R50%, degree of modulation (DoM), conformity index (CI), homogeneity index (HI), and healthy tissue mean dose (HTMD), were compared. Significant dosimetric differences were observed in several OARs doses and lowered in VMAT plans. The D2cm%, R50%, CI, HI and HTMD are dosimetrically inferior in DCA_SSO_VDR plans. The higher DoM results in poor dose gradient and better dose gradient for DCA_SSO_VDR and VMAT treatment plans, respectively. For liver SBRT, DCA_SSO_VDR treatment plans are neither dosimetrically superior nor better alternative to the VMAT delivery technique. A reduction of 69.75% MU was observed in DCA_SSO_VDR treatment plans. For the large size of PTV and high DoM, DCA_SSO_VDR treatment plans result in poorer quality.

Optically switchable organic light-emitting transistors.

Organic light-emitting transistors are pivotal components for emerging opto- and nanoelectronics applications, such as logic circuitries and smart displays. Within this technology sector, the integration of multiple functionalities in a single electronic device remains the key challenge. Here we show optically switchable organic light-emitting transistors fabricated through a judicious combination of light-emitting semiconductors and photochromic molecules. Irradiation of the solution-processed films at selected wavelengths enables the efficient and reversible tuning of charge transport and electroluminescence simultaneously, with a high degree of modulation (on/off ratios up to 500) in the three primary colours. Different emitting patterns can be written and erased through a non-invasive and mask-free process, on a length scale of a few micrometres in a single device, thereby rendering this technology potentially promising for optically gated highly integrated full-colour displays and active optical memory.

33. Comparative study of modulation for VMAT treatments planned on Eclipse and Raystation: Complexity index and experimental correlation

Introduction Volumetric modulated arc therapy technique allows to shape the isodose distribution around irregular or complex target and spare organ at risks. Those various dose distribution complexity will directly be translated in the level of modulation to be applied to the fluence and thus to the delivery system in terms of mechanical variations such as gantry speed, leaf movements, number of segments or dose rate variation. These last years, several studies have been carried out for the definition of fitted indexes that could be correlated to a plan complexity with regards to patient QA results [1] , [2] . In this context, two points have motivated this study: – Using existing indexes and defining new ones to compare VMAT plan issued from two different TPS. – Correlate these indexes to the experimental patient specific QA results. Methods In this study, two types of indexes have been used: the classical one described in the literature and simple derived indexes. The first derived index is based on the distance between two opposite leaves for each beam (not under a jaw) calculated for every control point of every arc of the plan. The first classical index is the MCSV [3] which the value is decreasing when the complexity is increasing. Among all VMAT plans for various indications, 450 VMAT plans have been analyzed (nearly 2/3 from Eclipse and 1/3 from Raystation) all of them treated on the same accelerator (Novalis TX). Patient specific QA have been performed with 2D diodes measurements using the ArcCheck phantom and a Pinpoint ionization chamber measurement located in the center of the ArcCheck. The analysis have been performed with local and global gamma indexes of 3%/3 mm with threshold set at 10% of the maximal dose. Results As a first step, we focused on the derived indexes and applied them to the Eclipse/Raystation plans. The median of the tip to tip distance of opposite leaves for all plans is about 10 mm and 18 mm, respectively, for Eclipse and Raystation. The mean proportion of opposite leaves having a tip to tip distance less than 10 mm is about 32% and 20%, respectively, for Eclipse and Raystation. As a second step we analyzed the exact same plans with the MCSv index. Results show a mean MCSV value of 0.25 and 0.39 and standard deviation of 0.08 (32%) and 0.13 (33%), respectively, for Eclipse and Raystation. These results show that the derived index we developed is in a good agreement with the standard index MCSV. Secondly, the results tend to show that plans, issued from Eclipse show or higher degree of modulation than those from Raystation. These tendency need to be correlated with the patient specific QA results. Conclusions The work already achieved in the framework of this study using plans performed according to our clinical standards, has showed clear differences in the complexity with regards to the TPS used. These results are confirmed by standard literature metric, such as the so called MCSv, but will be deeply investigated using other metrics. These results seems to corroborate a higher modulated solution on the Eclipse side that may lead to a more difficult plan to deliver, this has to be correlated with experimental QA.

Electron track reconstruction and improved modulation for photoelectric X-ray polarimetry

The key to photoelectric X-ray polarimetry is the determination of the emission direction of photoelectrons. Because of the low mass of an electron, the ionisation trajectory is not straight and the useful information needed for polarimetry is stored mostly in the initial part of the track where less energy is deposited. We present a new algorithm, based on the shortest path problem in graph theory, to reconstruct the 2D electron track from the measured image that is blurred due to transversal diffusion along drift and multiplication in the gas chamber. Compared with previous methods based on moment analysis, this algorithm allows us to identify the photoelectric interaction point more accurately and precisely for complicated tracks resulting from high energy photons or low pressure chambers. This leads to a better position resolution and a higher degree of modulation toward high energy X-rays. The new algorithm is justified using simulations and measurements with the gas pixel detector (GPD), and it should also work for other polarimetric techniques such as a time projection chamber (TPC). As the improvement is restricted in the high energy band, this new algorithm shows limited improvement for the sensitivity of GPD polarimeters, but it may have a larger potential for low-pressure TPC polarimeters.

Validation of the performance of 3-D detector arrays for radiotherapy verifications

Introduction Intensity modulated radiotherapy (IMRT/VMAT) is a complex procedure requiring proper dosimetric verification. IMRT dose distributions are characterized by high degree of modulation and by steep dose gradients. The fluence measurements for individual beams or at individual angle are not sufficient for evaluation of total dose distribution and for assuring patient safety. Purpose A number of electronic systems which allow for a pre-treatment plan verification based on reconstruction of the total dose distributions have been developed recently (Delta4, ArcCHECK, Octavius, etc.). A method of validation of such systems tested on the above listed devices is presented here. Materials and methods The method requires anthropomorphic phantoms and dosimetric films. In order to measure dose distributions in various cross-sections of the phantom the film dosimeters were used (Gafchromic EBT-3). The phantoms of the material and shape equivalent to the Delta4, ArcCkeck and Octavious detector arrays were developed. This film dosimetry methodology was used as a benchmark to test and validate the performance of commercially available 3-D verification systems. The gamma formalism was used for evaluation and comparison of the measured and calculated dose distributions. Results The results of comparisons of film measurements performed in test phantoms with dose distribution reconstructed with: Delta4, ArcCHECK and Octavious for a group of patient plans are presented as the percentage of passing points (PPP) for Γ ⩽ 1 criterion. Conclusion The 3-D verification systems and their reconstruction algorithms have to be validated with independent measurements or calculations before use in clinical practice.

Poster ‐ 45: The effect of plan modulation on VMAT liver SBRT treatments: A motion interplay study

Purpose:To investigate whether increasing the degree of MLC leaf modulation in VMAT liver SBRT treatment plans increases the dose differences due to the interplay effect.Methods:Two VMAT plans, delivering 54Gy in three fractions, with differing degrees of MLC aperture modulation were created for each of 10 patients. To simulate respiratory motion, an in‐house program was used to shift the positions of each active MLC leaf at every 0.6° of gantry rotation, according to the amplitude of a respiratory trace. To isolate the interplay effect from dose blurring, motion was simulated using four different starting points in the respiratory cycle. The same starting point was used for each of the three fractions, representing a worst case scenario. The four resultant dose distributions from each plan were subtracted from each other, and dose differences in the GTV were quantified using the standard deviation of the differential DVH.Results:Dose differences up to 1Gy were found in the GTV of the dose subtractions, indicating the presence of interplay effects. A Wilcoxon Signed Rank test indicates a significant (p<0.05) increase in the standard deviations of the low‐modulation plans to those with a higher degree of modulation. No planning constraints were exceeded with the introduction of respiratory motion.Conclusions:VMAT liver SBRT plans with a high degree of modulation exhibit an increased susceptibility to interplay effects. The dose differences due to interplay are not large enough to markedly decrease the plan quality.

SU‐F‐T‐533: Study of Dosimetric Properties of Cadmium Free Alloy Used in Compensator Based IMRT

Purpose:To study the dosimetric properties of cadmium free alloy which is used in compensator based IMRT.Methods:A mixture of 30% of lead,52% of bismuth and 18% of tin was used to prepare alloy. We prepared slabs of different thicknesses ranging from 0.71 cm to 6.14 cm. Density of alloy was measured by Archimedes’ principle using SI‐234 Denver instrument and water as buoyant liquid. Transmission, linear attenuation coefficient (µ), tissue phantom ration (TPR), beam hardening, surface dose (Ds), percentage depth dose (PDD) and effect of scatter were measured and analyze for different field size and different thickness of compensator for 6 MV photon beam. Measurements were carried out at 100 cm SSD and 160 cm SSD.Results:Density of alloy was found to be 9.5456 gm/cm3. Melting point of alloy is 90–95 °C. For a field size of 10×10 cm2 µ was 0.4253 cm‐1 at 100 cm SSD. Calculated TPR was found to be within 3 % of measured TPR. Ds was found to be decreasing with increasing thickness of compensator. 1cm, 1.98 cm and 4.16 cm thick compensator slab decreased surface dose by 4.2%, 6.1% and 9.5% respectively for a field size of 10×10cm2 at 100 cm SSD. As field size increases Ds increases for a given compensator thickness. This is due to increase in amount of scattered dose from wider collimator opening. For smaller field size, PDDs are increased from 3.0% to 5.5% of open beam PDDs as compensator thickness increases from 1 cm to 6.14 cm at a depth of 10 cm in water. For larger field size variation in PDDs is not significant.Conclusion:High degree of modulation can be achieved from this compensator material, which is essential in compensator based IMRT. Dosimetric properties analyzed in this study establish this alloy as a reliable, cost effective, reusable compensator material.

Anatomy- vs. fluence-based planning for prostate cancer treatments using VMAT

The purpose of this study was to compare the planning approaches used in two treatment planning systems (TPS) provided by Elekta for VMAT treatments. Ten prostate patients were studied retrospectively. Plan comparison was performed in terms of delivery efficiency and accuracy, as well as in terms of target coverage and critical organ protection by utilizing physical and radiobiological indices. These include: DVH (dose volume histogram) values, CI (conformity index), HI(%) (homogeneity index) and TCP (tumor control probability) for target coverage; mean doses, DVH values, dose to the normal non-target tissue, NTCP (normal tissue complication probability) and GI (gradient index) for critical organ sparing; MU/fraction and treatment time for delivery efficiency. The comparisons were performed using the two-sided Wilcoxon matched-pair signed rank test. Plans generated using the anatomy-based approach in ERGO++ and fluence-based approach in Monaco were found similar in terms of target coverage and TCP values, as well as in terms of rectum protection and corresponding NTCP values. The former exhibited increased delivery efficiency (comparable to that of 3D conformal radiotherapy) due to the relatively larger segments used. On the other hand advantages of the fluence-based approach in Monaco include increased conformity, better target dose homogeneity and higher dose gradient (lower dose to normal non-target-tissue) mainly due to the higher degree of modulation offered by the fluence-based approach, while the Monte Carlo algorithm used for dose calculation provides plans with increased accuracy despite the relatively small segments used.

TU‐E‐T‐6C‐02: Clinical Implementation of IMRT for Lung Cancers

IMRT has not been widely accepted as a standard‐of‐practice for treating lung cancers because of concerns of organ motion and that IMRT may spread large volume of low dose to radiosensitive lung tissue. At our institution, IMRT has been used mainly in the management of superior sulcus tumors, mesotheliomas, challenging non‐small‐cell and small‐cell lung cancers, and retreatment situations. To be able to use IMRT effectively for lung cancers, we need to pay attention to the following specific issues unique to this site. Patient Selection: IMRT may benefit patients who have critical organs adjacent to target volumes, e.g. spinal cord, esophagus, and previously irradiated tissues. IMRT can also be a superior tool compared to 3DCRT in providing dose coverage of complex shaped tumors such as multiple primary lesions and lymph nodes, and sculpturing dose away from normal lung. Target and motion: GTV for lung cancers should ideally be defined using multimodality imaging combining CT, PET, and MRI (if involving spinal cord and other soft tissues). CTV margin should consider probability of tumor seeding outside GTV and histology of different diseases. ITV margin should ideally be defined using dynamic 4D imaging to account for patient and tumor specific internal motion mainly from respiration. For highly mobile tumors, breath‐hold or other motion mitigation techniques may need to be implemented for IMRT delivered with dMLC. PTV margin needs to be examined and defined based on specific patient setup techniques with the help of portal or on‐line imaging. Accurate and reliable patient setup and immobilization are critical to IMRT as any other sites. Inverse planning: The most radiosensitive thoracic structure is lung, which may be affected by even low doses and often competes with target volume in terms of planning objectives. Shaping low doses away from lung is an important priority for lung and unique to IMRT of lung cancers. Providing adequate coverage with sufficient homogeneity to target volume is another important goal in planning. Sparing critical organs, i.e., cord, esophagus, heart, and reducing hot spots in non‐specific normal tissues should also be included as planning goals. The number of beams and their angles should be optimized carefully with the goals of sparing lung and critical organs, meanwhile considering delivery efficiency and patient compliance. Use of many equally spaced beams (>7) should be rarely used. Dose delivery and QA: IMRT delivery with dMLC should consider optimizing leaf sequence and improving MU efficiency. MLC transmission and leakage can contribute significant dose to lung and normal tissues for IMRT plans with many segments and high degree of modulation. Dosimetry verification should be performed for each treatment planning system, which is often limited in the degree of dose accuracy and is likely to underestimate low‐doses for lung IMRT. Monte Carlo based systems can be used complementary to measurements for commissioning and dosimetry QA purposes.Educational Objectives:1. To understand physics processes involved in using IMRT for lung cancers;2. To understand specific requirements and unique aspects of implementing IMRT for lung cancers.

Electrostatic charging and deflection of nonconventional droplet streams formed from capillary stream breakup

Droplet streams generated from capillary stream breakup and forced with amplitude-modulated (a-m) disturbances will undergo a systematic interdroplet merging process due to their relative velocities that result from the a-m disturbance. This paper concerns the electrostatic charging of droplets generated with a-m disturbances, and seeks an understanding between the competitive effects of the electrostatic repulsive force and the momentum associated with relative velocities that are due to the a-m disturbance. To this end, experimental results and numerical simulations that are in excellent agreement and predict the configuration of the charged droplet stream are presented. In this work, droplets are generated with the aforementioned technique and are electrostatically charged. It has been found that for droplets generated with a disturbance with a high degree of modulation, m, the momentum of the droplets dominates over the electrostatic force causing the droplet merging process to be similar to the uncharged case as attested by both experimental results and numerical simulations. Here, m is the ratio of modulation to original carrier amplitudes. For droplets with lower values of m, the electrostatic forces dominate and it is found that the relative positions of the droplets will oscillate along the direction of their flight path with maximum excursions not exceeding one wavelength of the carrier disturbance (i.e., the separation of the unmerged droplets).

Influence of modulated complex tones on power window regulator noise quality

The influence of amplitude and frequency-modulated complex tones on the perceived quality of power window regulator noise is examined in this paper. Modulation characteristics of sounds generated by electro-mechanical actuators in automotive components, such as power window regulators, play a major role in affecting the perceived overall quality of a vehicle system. Annoying noise with a high degree of modulation tends to create the impression of an inferior product with inherent design flaws and manufacturing problems. Current subjective quality rating methods based on simple jury evaluation schemes and idealized metrics cannot be used to quantify modulation effects accurately. This is because modulated tones are temporal phenomena that are closely related to the rotational velocities of motors that are not typically accounted for in existing time-averaged sound quality metrics. A new time-varying based index is developed that incorporates operational velocity, noise spectrum, and binaural effects to quantify sound quality from acoustic signals measured using a binaural head system and rotational velocity data of the window regulator mechanism. Numerical simulations based on the proposed algorithm are subsequently used to predict the noise quality of various systems. [See NOISE-CON Proceedings for full paper.]

The electroencephalogram (EEG) as a research tool in human behavior genetics: Psychological examinations in healthy males with various inherited EEG variants

Interpretation of the results from psychological examinations of 298 probands with inherited EEG variants requires (1) critical evaluation of previous literature on psychological EEG correlates, (2) knowledge of the main concepts and experimental approaches for elucidating the basic mechanisms of EEG rhythms, (3) discussion of previous attempts to link psychological variation in human populations with corresponding variation in brain function, and (4) interpretation of results from considerations at these three levels with the data from our own study. At the first level (previous psychological studies), comparison with Schmettau's study proved to be especially revealing: Her conclusions about personality correlates with high alpha-index and with "flat" EEGs were very similar to ours with the monotonous alpha- (R) and low-voltage (N) EEGs, respectively. Her EEG type with high beta-index overlaps with our beta-diffuse (BD) type; a tendency to psychasthenia and low resistance to stress is less obvious in our group, but is expressed indirectly by reduced speed and accuracy in tests requiring attentiveness and persistence. The correlation between alpha-frequency and intelligence found in other studies was confirmed by the especially high intelligence scores of our group with occipital fast alpha-variants (BO). At the second and third levels of the discussion (EEG mechanisms; neurophysiological theories), the cooperation of cerebral cortex (EEG battery), thalamus (pacemaker), and ARAS (tonic arousal) is discussed, and the personality typologies of Eysenck and Claridge are mentioned. From this and other evidence, the following hypotheses are discussed: 1) The personality profiles of the R group are influenced by high activity and efficiency of the thalamic alpha-pacemaker(s), which leads to a high degree of modulation, selection, and amplification of afferent stimuli. 2) In the countertype of this EEG variant, the N EEG, a low modulation and amplification by the thalamic alpha-pacemaker is assumed. This leads to relatively low intensity of feeling and to low spontaneous activity, but to faster information processing. Combined with an increased level of tonic arousal in the ARAS, it may cause certain 'neurotic' complaints (our low-voltage borderline (NG) group). 3) The EEG with diffuse beta-waves (BD) is caused by a high level of tonic arousal in the ARAS, which tends to distrub the thalamocortical circuit. This leads to reduced stress resistance and to impairment of intellectual functions, especially space perception. Due to limited evidence, the next two hypotheses are advanced only tentatively: 4) alpha-rhythm with very high frequency 16--19 c/s) leads to improvement of information processing and, hence, to high intellectual performance and motor dexterity. 5) Probands with frontoprecentral beta-groups (BG) show no psychological signs of increased tonic arousal; therefore, these beta-groups are caused not by increased tonic arousal of the ARAS, but by a genetic variant of a thalamic subsystem.

Abnormale Energieunschärfe intensiver Elektronenstrahlen aus Plasmakathoden

Intense electron beams extracted from DUOPLASMATRON-plasma cathodes show a high degree of modulation in intensity and an abnormally large energy spread; these facts cannot be explained simply by the temperature of the plasma electrons and the discharge structure. However, an analysis of the discharge stability behaviour and the interaction of source- and extracted beam-plasma leads to an explanation for the observed effects.

Dynamic properties of excitation and inhibition in the cochlear nucleus.

The dynamic properties of inhibition and excitation of single units in the cochlear nucleus were studied using tones that were amplitude modulated either sinusoidally or with pseudorandom noise. The cross-correlation analysis of the unit discharge rate and the pseudorandom noise modulation of the stimuli showed that the dynamic properties determined from the responses to a single modulated excitatory tone (at CF), to a modulated excitatory tone together with an unmodulated inhibitory tone (above CF), and to a modulated inhibitory tone together with an an unmodulated excitatory tone were almost identical with regard to latency as well as to delay of the peak of the cross-covariance function. On the basis hereof it is inferred that the inhibition is either a cochlear phenomenon or that it is transmitted over pathways with identical temporal properties as those of the excitation. When 2 tones were presented simultaneously the modulation of the excitatory tone usually gave a higher degree of modulation of the discharge rate than did modulation of an inhibitory tone. Addition of an unmodulated inhibitory tone to a modulated tone at CF resulted in an extension of the range of intensities over which the maximal gain was relatively constant. In many units this range extended from about 10dB above the unit's threshold to 60 dB or more above.

High Performance Phase Fluorometer Constructed from Commercial Subunits

Using new commercial equipment including a Pockels-effect light modulating device, a phase fluorometer with the following characteristics has been constructed: high intensity light with a high degree of modulation (typically m=43% at 1 kV modulating voltage and 462 mμ); pure sine modulation of variable frequency (14.0110, 21.0170, 27.0040 Mc); narrow wavelength regions for excitation and emission; very small contamination of detected light with exciting light (<1%); spectral range of the modulated light from 200 to 1000 mμ. The phase difference between fluorescent light and scattered light is measured with a high precision wide band phasemeter employing fixed and variable coaxial delay lines. The output of the phase detector is recorded and precise phasenull found graphically. Maximum time resolution is 0.02 nsec. The average over-all precision in general use is Δτ/τ=2% in the range from 2 to 63 nsec; a wider range can be measured with slightly reduced precision. Systematic errors caused particularly by electron transit time in the photomultipliers depending on voltage, exposed area of photocathode, wavelength, and photocurrent are investigated for two photomultipliers (EMI 9558B and RCA 6217), and procedures to control these errors are described. Measurements of fluorescence liftetimes of five organic compounds at very low concentrations show a lack of dependence of the results on type of photomultiplier tube, photocurrent, multiplier voltage, type of scatterer, modulating frequency, and emission wavelength. This suggests that the accuracy of the measurements is very nearly equal to precision and is limited by the experimental error in sample preparation rather than the accuracy of the measurements themselves. Some lifetime results reported are 10−6 M fluorescein in 0.01 M KOH, τ=(3.83±0.01) nsec; 10−5 M 9,10-diphenylanthracene in 95% ethanol, τ=(7.91±0.02) nsec; acridone in water (0.01×saturated solubility), τ=(15.54±0.05) nsec; 1.3×10−6 M safranin T in pyridine containing 5% water, τ=(2.29±0.01) nsec; 3×10−7 M chlorophyll-a in 95% ethanol, τ=(5.55±0.03) nsec. Some effects of oxygen quenching and concentration are also reported. The instrument allows analysis of complex decay kinetics by varying the excitation modulation frequency and selecting narrow wavelength intervals in the emission. A wide range of excitation and emission intensities can be employed for studies of intensity dependence of liftetimes as is necessary in studies of natural photosynthesis.

L3 coaxial system - Television terminals

Television terminals are required at circuit ends of the L3 coaxial system, at the transmitting end to condition video signals for carrier transmission, and at the receiving end to detect the transmitted signals. Special signal characteristics, that is, a degree of modulation which exceeds the value commonly referred to as 100 per cent modulation, require departures from standard modulating and detecting processes. The high degree of modulation requires both careful control of transmitted wave form and, at the receiver product, demodulation with phase-synchronous carrier (homodyne detection).

The L3 Coaxial System

Television terminals are required at circuit ends of the L3 coaxial system; at the transmitting end to condition video signals for carrier transmission and at the receiving end to detect the transmitted signals. Special signal characteristics, e.g., a degree of modulation which exceeds the value commonly referred to as 100 per cent modulation, require departures from standard modulating and detecting processes. The high degree of modulation requires both careful control of transmitted wave form and at the receiver product demodulation with phase synchronous carrier (homodyne detection). Carrier regeneration requirements result in the choice of one step frequency translation from the video frequency spectrum to the allocated vestigial sideband carrier spectrum. The one step process using a single modulator results in unusual balance requirements for the modulator itself and an unusual circuit configuration. Transmission quality objectives for the terminals are such as to permit six pairs of television terminals to operate in tandem in a transcontinental circuit. This permits a degree of interconnecting flexibility in operation with other systems, e.g., L1 coaxial or microwave systems. These objectives place severe requirements upon the transmission stability of various filters and other circuits within the terminals. New network techniques both in design and fabrication are brought to bear in the effort to achieve required performance. The transmitting and receiving terminals are described, illustrating the functional operation and mechanical and electrical arrangements of the equipment.

Polarimetry

The key to photoelectric X-ray polarimetry is the determination of the emission direction of photoelectrons. Because of the low mass of an electron, the ionisation trajectory is not straight and the useful information needed for polarimetry is stored mostly in the initial part of the track where less energy is deposited. We present a new algorithm, based on the shortest path problem in graph theory, to reconstruct the 2D electron track from the measured image that is blurred due to transversal diffusion along drift and multiplication in the gas chamber. Compared with previous methods based on moment analysis, this algorithm allows us to identify the photoelectric interaction point more accurately and precisely for complicated tracks resulting from high energy photons or low pressure chambers. This leads to a better position resolution and a higher degree of modulation toward high energy X-rays. The new algorithm is justified using simulations and measurements with the gas pixel detector (GPD), and it should also work for other polarimetric techniques such as a time projection chamber (TPC). As the improvement is restricted in the high energy band, this new algorithm shows limited improvement for the sensitivity of GPD polarimeters, but it may have a larger potential for low-pressure TPC polarimeters.