Initial Performance Characteristics Research Articles

Long-Term Outdoor Testing of Perovskite Mini-Modules: Effects of FACl Additives

The outdoor performance monitoring of perovskite modules over 16 weeks is reported. Two different types of active perovskite layers were studied: one type contained formamidinium chloride (FACl) halide additives and the other contained no additives with the main purpose to investigate performance trends during the outdoor exposure of those type of devices. Long-term side-by-side outdoor testing of devices with and without halide additives was not implemented in the past and merits investigation in order to determine the impact of additives on perovskite performance and stability. Although the two types of modules displayed similar initial outdoor performance characteristics, their outdoor performance evolution differed. Different degradation rates between the modules with and without additives were obtained just after field installation. In particular, the modules with additives exhibited higher performance degradation under open-circuit loading conditions between current-voltage (IV) scans. Long-term monitoring of both modules recorded a reduction of the efficiency over the course of the day with subsequent recovery overnight and in many cases during the day. The relative values of performance degradation and overnight recovery were calculated over the timespan of outdoor testing and indicated dominant normalized diurnal performance degradation in one type of modules (without FACl additives) in the range between 15–20% and in the other type of modules (with additives) 5–10%. The dominant normalized performance recovery values found were 25–30% and 5–10%, respectively. Finally, dark lock-in thermography (DLIT) and Raman studies were performed on the exposed devices and revealed differences in hotspot evolution and vibrational modes between the different types of module.

NGAKES THE OPERATION OF THE LINK OF THE POWER TAKE-OFF SHAFT OF THE TRACTOR HTZ-150K-09

One of the effective directions on the problem of assessing the technical reliability of tractors supplied to agriculture is the study of the initial performance characteristics and wear of individual elements and components of the tractor. (Research purpose) The research purpose is considering the operation of the intermediate support as part of the cardan drive of the power take-off shaft of the tractor HTZ-150K-09; determining the loads on its bearings and the operation mode of the support and its resource. (Materials and methods) When transmitting torque in the power take-off mechanism, axial and radial forces arise, causing reactions in the intermediate support bearings. The equilibrium equations of the system of forces in space were used to determine their values. (Results and discussion) The dynamics of the driveshaft is such that when the tractor moves over an uneven field or when it turns, the rotation speed of the driven shaft does not coincide with the speed of the drive. This is due to the constant change in the angle between the shafts. The variable rotation speed of the driven shaft causes angular accelerations and inertial loads of elements in the cardan transmission itself and in other parts of the drive and the working bodies of agricultural machines. The loads on the bearings of the intermediate support from the side of the cardan transmission will have a dynamic character, since they reach the maximum and minimum twice in one revolution of the support shaft. (Conclusions) To increase the resource of the power take-off cardan drive link, it is necessary to carry out maintenance in a timely manner, while using additional damping elements.

Approximation of hydraulic turbine performance characteristics using optimal splines and neural networks

The performance characteristic of hydrounits is used very often in various control systems on hydro power plant for velocity control, power distribution, for displaying at different levels of automation pyramid: technicians, technologists, management and so on. Different systems do not have single unified description of the hydrounit’s performance characteristic. It leads to growth of unnecessary calculations, errors and collisions. The study of the turbine efficiency can be automated by creating an appropriate mathematical model that approximates the initial performance characteristics of the turbine. This paper describes a method of approximation of the turbine performance characteristics using optimal two-dimensional cubic Hermit splines with free boundary conditions. The proposed method of hydrounit efficiency description allows to create single mathematical model and to use it in any control systems. The calculation load tests show high efficiency of the methods and confirm the possibility of their application in PLCs and servers.

Benchmarking automated flow cytometry data analysis software using synthetic datasets

Background & Aim Recent years have seen the development of many computational tools for automated Flow Cytometry (FC) data analysis. These software tools enable automatic cell population identification, classification and novel data visualisations. Because different software will use different mathematical approaches to identify and quantify cells, outputs can potentially vary when analysing the same dataset. Often, researchers simply accept the results without understanding the underlying black box algorithms and the potential for variation of output. Comparability studies between automated FC software requires high-quality benchmarking datasets that assess the performance and robustness of the algorithms. However, currently available datasets from FC experiments lack “gold standards” due to the nature of live cell biological materials. Furthermore, the datasets that meet data complexity requirements are costly to produce and only come from a narrow range of cell or disease models. Computer simulated FC datasets offer many advantages over their real-world counterparts. Synthetic standards can potentially be created, with data properties being highly controlled to objectively and systematically compare between software. Methods, Results & Conclusion In this research a range of synthetic FC cluster data have been systematically designed and generated containing controlled separation between clusters, rare cell populations, normal and non-normal probability distributions. These reference datasets have been used to evaluate the initial performance characteristics of a number of popular flow cytometry data analysis software, with the accuracy and repeatability of software being measured as the difference between the output and a reference absolute cell number. The initial results reveal similar trends in performance between software when analysing clusters with specific degrees of separation. Certain software platforms were more suited to analysis of rare cell populations. When using non-normally distributed clusters, the presence of skewed cell populations did not affect clustering performance, but the orientation of cluster skewness did. This demonstrates that benchmarking of FC automated software platforms will be possible with a high level of testing integrity using synthetic cluster dataset design leading to enhanced confidence in the data quality of cell characterisations.

Quantification of Micrornas by Absolute Dpcr for the Diagnostic Screening of Colon Cancer

There is currently no validated micro(mi)RNA diagnostic stool test to screen for colon cancer (CC) on the market because of the complexity of fecal density, vulnerability of stool to daily changes, and the presence of three sources of miRNAs in stool (cell-free from fecal homogenates, exsosomal miRNAs from fecal exosomes, and fecal colonocytes). To address these complexities, we have first carried out a microarray miRNA experiment, using Affymetrix GeneChip miRNA 2.0 Arrays, on immunocaptured and enriched stool colonocytes of 15 subjects (three healthy controls and twelve colon cancer patients [three TNM stage 0-1 (e.g., polyps ³ 1 cm, villous or tubvillous, or with high grade dysplasia), three stage 2, three stage 3, and three stage 4 in triplicates to select a smaller panel of 14 preferentially expressed mature miRNAs associated with colon cancer (12 Up-Regulated, miR-19a, miR-20a, miR-21, miR-31, miR-34a, miR-96, miR-106a, miR-133a, miR-135b, miR-206, miR-224 and miR-302; and 2 Down-Regulated, miR-143 and miR-145). In a subsequent validation study carried out on total small RNA extracted by immunocapture, followed by RT that employed TaqMan® miRNA Reverse Transcription (RT) Kit and a Custom TaqMan RT Primer Pool, absolute quantification of miRNAs, in copies/µl, was measured using a chip-based Absolute QuantStudio 3D Digital PCR analysis. To ensure that we have chosen human and not bacterial small total RNA, we have carried out coextraction protocols with E. coli K1 strain RS18, compare Agilent electrophoretic patterns, and also sequenced random samples throughout this research using mRNA/miRNA sequencing. Our initial quantitative dPCR miRNA data presented herein showe that the quantitative changes in the expression of a few mature miRNA genes in stool, which are associated with right and left colon cancer, would provide for a more convenient, sensitive and specific diagnostic screening markers thatare more useful than those test markers currently available on the market, such as the low-sensitivity (<15%) fecal occult blood test (FOBT); result in better compliance; and is more economical than the invasive and expensive colonoscopy exam in colon cancer, which can be cured if that cancer is detected at the early TNM stages, and that becomes incurable and deadly if not diagnosed before metastasis. Initial test performance characteristics of the miRNA approach showed that the test has a high numerical predictive value in colon cancer. Moreover, underpinning of the miRNA markers as a function of total RNA showed that the test can numerically differentiate between control subjects and colon cancer patients, particularly at the early stages of that curable cancer. We propose to extend our initial research results to a larger prospective and randomized five-years nested case-control study, to validate the expression of the above 14 miRNAs, in stool of 180 individuals in an epidemiologically designed study, using (30 controls and 150 colon cancer patients (thirty precancerous polyps (stage 0-1), forty five stage 2, and seventy-five colon cancer stages 3 or 4). chosen randomly by an epidemiological method from 900 control and CC subjects to allow for an adequate time to collect the required 900 stool samples, as well as allowing for statistically valid analysis, standardized test conditions, and to provide a mean for determining the true sensitivity and specificity of a miRNA-screening approach in noninvasive human stool. Power-analysis has indicated that a total of 180 individuals, which will take us 5 years to enroll in testing, is an appropriate number of subjects to standardize and validate our proposed miRNA screening test. We may find out at the end of the proposed validation study in stool that fewer miRNAs, or even one miRNA, may suffice to serve as an efficient and a quantitative marker for the non-invasive diagnostic screening of colon cancer in human stool. The above approach when combined with bioinformatics analysis, to correlate miRNA seed data with our previously published messenger (m)RNA target data in stool, allows for a thorough mechanistic understanding of how miRNA genes regulate mRNA expression, and would offer a better comprehensive diagnostic screening test for the non-invasive early detection stage (0-1) of colon cancer. In order to show the clinical sensitivity and specificity of the proposed miRNA test, the absolute miRNA PCR values, in copies/µl, will be correlated with FOBT, colonoscopy, and pathology data. Standardization will establish test’s performance characteristics (sample selection, optimal sample running conditions, preservation and storage) to ensure that the assay will perform the same way in any laboratory, by any trained personnel, anywhere in the World. Ultimately, a smaller number of selected validated miRNAs (<10) showing increased and reduced expression could suffice to give quantitative miRNAs colon cancer expression values, useful for the early diagnostic screening of that curable cancer.

Effects of Initial Performance, Gross Efficiency and O 2peak Characteristics on Subsequent Adaptations to Endurance Training in Competitive Cyclists.

The present study investigated the effects of initial levels of cycling performance, peak oxygen uptake (O2peak) and gross efficiency (GE) on the subsequent adaptations of these variables and their relationship following high-intensity training (HIT) designed to increase O2peak in competitive cyclists. Sixty cyclists (O2peak = 61 ± 6 mL kg-1 min-1) were assigned a 12-week training program consisting of twenty-four supervised high-intensity interval training sessions and ad libitum low intensity training. GE was calculated at 125, 175, and 225 W and performance was determined by mean power during a 40-min time-trial (Power40 min). In addition to correlation analyses between initial level and pre- to post-intervention changes of the different variables, we compared these changes between four groups where participants were categorized with either low and/or high initial levels of O2peak and GE. Average volume of high- and low-intensity training during the 12-week intervention was 1.5 ± 0.3 and 8.3 ± 2.7 h·week-1, respectively. Following the 12-week training period, there was a significant increase in absolute and body mass normalized O2peak and Power40 min (p < 0.05) and a significant decrease in GE (p < 0.05) for all athletes pooled. There was no change in body mass following the 12-week training period. We found a moderate negative correlation between initial level of O2peak and the change in O2peak following the training period (r = -0.32; p < 0.05). A small negative correlation was also found between initial Power40 min and its change following training both when expressed in absolute power and power normalized for body mass (r = -0.27 and -0.28; both p < 0.05). A moderate negative correlation was also found between initial levels for GE and its change following training (r = -0.44; p < 0.01). There were no differences between the four groups based on initial levels of O2peak and GE in the response to training on O2peak, GE, or Power40 min (all p > 0.12). In conclusion, the present findings suggest that there are statistically significant effects of initial levels of cycling performance and O2peak and on the subsequent adaptations following a 12-week HIT program, but the small and moderate effects indicate limited influence on training practice.

Rambutan-like CNT-Al2O3 scaffolds for high-performance cathode catalyst layers of polymer electrolyte fuel cells

Rambutan-like CNT-Al2O3 scaffolds are introduced as a potential candidate for CNT-based catalyst supports to overcome the CNT issues, such as the easy bundling in catalyst ink and the poor pore structure of the CNT-based catalyst layers, and to achieve high MEA performance in PEFCs. Non-porous α-phase Al2O3 balls are introduced to enable the growth of multiwalled CNTs, and Pt nanoparticles are loaded onto the CNT surfaces. In a half-cell, the Pt/CNT-Al2O3 catalyst shows much higher durability than those of a commercial Pt/C catalyst even though it shows lower oxygen reduction reaction (ORR) activity than Pt/C. After using the decal process for MEA formation, the Pt/CNT-Al2O3 shows comparable initial performance characteristics to Pt/C, overcoming the lower ORR activity, mainly due to the facile oxygen transport in the cathode catalyst layers fabricated with the CNT-Al2O3 scaffolds. The Pt/CNT-Al2O3 also exhibits much higher durability against carbon corrosion than Pt/C owing to the durable characteristics of CNTs. Systematic analysis of single cell performance for both initial and after degradation is provided to understand the origin of the high initial performance and durable behavior of Pt/CNT-Al2O3-based catalyst layers. This will provide insights into the design of electrocatalysts for high-performance MEAs in PEFCs.

The Paediatric Observation Priority Score: A System to Aid Detection of Serious Illness and Assist in Safe Discharge

The Paediatric Observation Priority Score (POPS) is a bespoke assessment tool for use in Paediatric Emergency Departments incorporating traditional physiological parameters alongside more subjective observational criteria. Initial performance characteristics of POPS were analysed in a convenience sample of 936 presentations to ED. Triage on the basis of gut instinct parameters identified an additional 261 patients deemed of lowest acuity compared to analysis by physiology scores. Resource consumption increased with increasing acuity on presentation. POPS shows promise in assisting in the assessment process of children presenting to Emergency Departments. Inclusion of subjective triage criteria helps contextualise the physiological parameter scoring by using the experience of staff conducting triage. Initial interpretation of presenting physiology gives a more informed assessment of initial acuity, and thus is better able to identify a child who can be safely managed in the community. The system also allows for rapid detection of those most unwell.

NOvA: Current Status and Future Reach

NOνA, the NuMI Off-Axis νe Appearance experiment will study νμ→νe oscillations, characterized by the mixing angle θ13. A complementary pair of detectors will be constructed ∼14 mrad off beam axis to optimize the energy profile of the neutrinos. This system consists of a surface based 14 kTon liquid scintillatior tracking volume located 810 km from the main injector source (NuMI) in Ash River, Minnesota and a smaller underground 222 Ton near detector at the Fermi National Accelerator Laboratory (FNAL). The first neutrino signals at the Ash River site are expected soon after the completion of 2012 Fermilab accelerator upgrades. In the meantime, a near detector surface prototype has been completed and neutrinos from two sources at FNAL have been observed using the same highly segmented PVC and liquid scintillator detector system that will be deployed in the full scale experiment. With the recent measurements of θ13 as input, updated sensitivities of NOνAʼs capability to ultimately determine the ordering of the neutrino masses and measure CP violation in neutrino oscillations will be provided. Additionally, design and initial performance characteristics of the surface prototype system along with implications for the full NOνAprogram will be presented.

NOνA detector technology with initial performance from the surface prototype

NOνA, the NuMI Off-Axis νe Appearance experiment, will study νμ → νe oscillations characterized by the mixing angle θ13. Provided θ13 is large enough, NOνA may ultimately determine the ordering of the neutrino masses and measure CP violation in neutrino oscillations. A complementary pair of detectors will be constructed ~14 mrad off beam axis to optimize the energy profile of the neutrinos. This system consists of a surface based 14 kTon liquid scintillatior tracking volume located 810 km from the main injector source (NuMI) in Ash River, Minnesota and a smaller underground 222 Ton near detector at the Fermilab. The first neutrino signals at the Ash River Site are expected prior to the 2012 accelerator shutdown. In the meantime, a near detector surface prototype has been completed and neutrinos from two Fermilab sources have been observed using the same highly segmented PVC and liquid scintillator detector system that will be deployed in the full scale experiment. Design and initial performance characteristics of this prototype system are being fed back into the design for the full NOνA program.

Brief Report: Is Cognitive Rehabilitation Needed in Verbal Adults with Autism? Insights from Initial Enrollment in a Trial of Cognitive Enhancement Therapy

Cognitive rehabilitation is an emerging set of potentially effective interventions for the treatment of autism spectrum disorder, yet the applicability of these approaches for "high functioning" adults who have normative levels of intelligence remains unexplored. This study examined the initial cognitive performance characteristics of 40 verbal adults with autism enrolled in a pilot trial of Cognitive Enhancement Therapy to investigate the need for cognitive rehabilitation in this population. Results revealed marked and broad deficits across neurocognitive and social-cognitive domains, despite above-average IQ. Areas of greatest impairment included processing speed, cognitive flexibility, and emotion perception and management. These findings indicate the need for comprehensive interventions designed to enhance cognition among verbal adults with autism who have intact intellectual functioning.

Validation of Fluorescence In Situ Hybridization Using an Analyte-Specific Reagent for Detection of Abnormalities Involving the Mixed Lineage Leukemia Gene

Fluorescence in situ hybridization (FISH) is a molecular cytogenetic assay that is commonly used in laboratory medicine. Most FISH assays are not approved by the US Food and Drug Administration but instead are laboratory-developed tests that use analyte-specific reagents. Although several guidelines exist for validation of FISH assays, few specific examples of FISH test validations are available in the literature. To provide an example of how a FISH assay, using an analyte-specific reagent probe, may be validated in a clinical laboratory. We describe the approach used by an individual laboratory for validation of a FISH assay for mixed lineage leukemia (MLL) gene. Specific validation data are provided illustrating how initial assay performance characteristics in a FISH assay for MLL may be established. Protocols for initial validation of FISH assays may vary between laboratories. However, all laboratories must establish several defined performance specifications prior to implementation of FISH assays for clinical use. We describe an approach used for assessing performance specifications and validation of an analyte-specific reagent FISH assay using probes for MLL rearrangement in interphase nuclei.

Initial Performance from the NOνA Surface Prototype Detector

Abstract NOνA, the NuMI Off-Axis νe Appearance experiment, will study νμ → νe oscillations characterized by the mixing angle θ13. Provided θ13 is large enough, NOνA may ultimately determine the ordering of the neutrino masses and measure CP violation in neutrino oscillations. A complementary pair of detectors will be constructed ∼14 mrad off beam axis to optimize the energy profile of the neutrinos. This system consists of a surface based 14 kTon liquid scintillatior tracking volume located 810 km from the main injector source (NuMI) in Ash River, Minnesota and a smaller underground 222 Ton near detector at the Fermilab. The first neutrino signals at the Ash River Site are expected prior to the 2012 accelerator shutdown. In the meantime, a near detector surface prototype has been completed and neutrinos from two Fermilab sources have been observed using the same highly segmented PVC and liquid scintillator detector system that will be deployed in the full scale experiment. Design and initial performance characteristics of this prototype system are being fed back into the design for the full NOνA program.

Effect of catalytic ink on sub-freezing endurance of PEMFCs

Effect of catalytic ink on sub-freezing endurance of proton exchange membrane fuel cells (PEMFCs) was investigated in this paper. By direct spraying method, a catalyst-coated membrane (CCM) was fabricated with isopropyl alcohol as organic solvent (CCM-A), and CCM-B was fabricated with isopropyl alcohol and butyl acetate. The hydrophobicity of the two CCMs was similar proved by contact angle tests, and CCM-B showed larger pore volume demonstrated by mercury intrusion tests. Initial cell performance and relevant electrochemical characteristics of the two CCMs were measured and compared. CCM-B showed better performance and larger electrochemical active surface area (ECA). By analyzing the electrochemical impedance spectra (EIS) at low current densities, the ionic resistances of the catalyst layers were calculated. Results indicated that adding butyl acetate to the catalytic ink benefited the ionic resistance. Then, the fuel cells with the two CCMs were subzero stored at −20 °C with saturated residual water. After 20 freeze–thaw cycles, the CCM prepared with isopropyl alcohol and butyl acetate showed less degradation in terms of polarization curves and EIS. And the ionic resistances of the both CCMs decreased to a certain extent.

A Novel High-Sensitivity Rapid-Acquisition Single-Photon Cardiac Imaging Camera

This study described and validated a new solid-state single-photon gamma-camera and compared it with a conventional-SPECT Anger camera. The compact new camera uses a unique method for localizing gamma-photon information with a bank of 9 solid-state detector columns with tungsten collimators that rotate independently. Several phantom studies were performed comparing the new technology with conventional-SPECT technology. These included measurements of line sources and single- and dual-radionuclide studies of a torso phantom. Simulations were also performed using a cardiothoracic phantom. Furthermore, 18 patients were scanned with both the new camera and a conventional-SPECT camera. The new camera had a count sensitivity that was 10 times higher than that of the conventional camera and a compensated spatial resolution that was moderately better. Dual-radionuclide studies using a phantom show the further potential of the new camera for a 2-tracer simultaneous acquisition. Two-minute clinical studies with the new camera and 11-min studies with the conventional camera qualitatively showed good-to-excellent image quality and improved myocardial edge definition for the new camera. These initial performance characteristics of a new solid-state single-photon gamma-camera offer great promise for clinical dynamic SPECT protocols, with important implications for applications in nuclear cardiology and molecular imaging.

Electrical Properties of Atomic Layer Deposited HfO2 Gate Dielectric Film Using D2O as Oxidant for Improved Reliability

The initial performance and reliability characteristics of metal–oxide–semiconductor (MOS) capacitors with HfO2 films deposited with H2O or D2O as an oxidant and Hf[N(C2H5)(CH3)]4 as a metal precursor using atomic layer deposition (ALD) were investigated. From secondary ion mass spectroscopy (SIMS) analysis, we observed that deuterium was homogeneously incorporated into the HfO2 film using D2O during ALD. Compared with H2O-processed devices, D2O-processed devices exhibit less charge trapping, less interface trap density generation, and longer time-dependent dielectric breakdown (TDDB) under electrical stress. This improvement of reliability characteristics can be explained by the deuterium isotope effect, which leads to a larger bonding strength of deuterium in the HfO2 film and at the HfO2/Si interface.

In-service deterioration of compressed earth blocks

With the increasing backlog of shelter in most of the third world, attempts are being made to evolve low-cost but durable walling units. The introduction of compressed earth blocks (CEBs) some 50 years ago was seen as a major milestone. These blocks are made by compressing a damp mix of soil (90–95%), and cement (5–10%) to form strong and dense blocks used for walling. While considerable knowledge is available regarding their initial performance characteristics, little research has so far been conducted on their long-term durability and deterioration due to prolonged exposure to environmental factors. It is now widely recognised that rapid and premature deterioration does take place when the material is used in unrendered walling in most humid tropical environments. Premature defects such as roughening, pitting, erosion, volume reduction, cracking as well as crazing, etc., have all been witnessed within periods ranging from 1 month to 5 years after completion of construction. This paper reports on recent research conducted in Uganda where in-service defects such as pitting and cracking where measured directly from existing exposed walling to quantify their nature and extent. It can be concluded that the greatest deterioration was found to occur on east–west facing facades, and on the lower wall sections. The deterioration was also found to correspond to the age of the structure.

CT colonography (virtual colonoscopy) for primary colorectal screening: challenges facing clinical implementation

Computed tomographic colonography (CTC), also referred to as virtual colonoscopy, is a minimally invasive test for the detection of colorectal polyps. Although its initial performance characteristics for evaluating lowprevalence populations were rather disappointing [1, 2], a larger multicenter trial in asymptomatic adults subsequently showed that CTC has the potential to be an effective primary screening tool [3]. Key features in the latter study that help explain this improved performance include the use of the three-dimensional endoluminal display for primary polyp detection, oral contrast for tagging of residual fluid and stool, segmental unblinding of CTC results at optical colonoscopy (OC), and use of only multidetector CT scanners [3]. As we await further validation of this rapidly evolving technique, actual clinical implementation of primary CTC screening should proceed without delay by those who are currently able to achieve an acceptable accuracy. The need for immediate action is self-evident, as far too many people are dying from a disease that could have been prevented by effective routine screening in more than 95% of cases [4]. There are many important challenges that are likely to be encountered as CTC screening transitions from the realm of research to daily clinical practice (Table 1). This update focuses primarily on three specific issues: (a) development of a logical diagnostic algorithm for CTC screening, (b) identifying the most appropriate group of patients to be screened by CTC, and (c) establishing a mutually beneficial working relationship with gastroenterology. Additional challenges and issues that are also important but are not covered in report include demonstrating the relative cost effectiveness of CTC screening, reimbursement by third-party payers, dedicated training of radiologists, and establishment of standard practice guidelines and accreditation. In the end, I believe that none of these challenges will prove to be insurmountable.

Functional design features and initial performance characteristics of a magnetic-implant guidance system for stereotactic neurosurgery.

A helmet with a roughly cubic array of six super-conducting coils is used to apply force on a small permanent magnet pellet in brain or in brain phantom material. This apparatus, called the Magnetic Stereotaxis System, will be used to deliver drugs and other therapies directly into deep brain tissues, under control of a computer and fluoroscopic imaging system. This paper considers only the force application aspects of the instrument. The primary design features of the helmet and power supply controls are presented, along with field plot data and single-axis motion results. The field plot data show that agreement with the finite-element iron-free field calculations is sufficiently high (> 1%) for the instrument. These preliminary motion data indicate accuracy better than 2 mm for the impulsive pellet motion, even though the visual position observations had significantly greater error than the completed imaging system will have. The companion paper will take up analysis of the control aspects of the motion, and our recent solutions to difficulties found in the experimental work described here.

Reflectron time-of-flight mass spectrometer for laser photodissociation

We describe a new reflectron time-of-flight mass spectrometer configuration for laser photodissociation of mass-selected ions and the initial performance characteristics observed for this instrument. Ions are produced by laser photoionization within the acceleration region of the instrument or by laser vaporization in an external pulsed-nozzle cluster ion source. Mass selection is accomplished with pulsed deflection plates at the end of an initial drift section. Laser photodissociation of selected ions takes place at the turning point in the ion trajectory in the reflectron. The transit time through a second drift section defines the fragment ion masses. Optimized operating conditions and the role of mass discrimination in this instrument are discussed.