High-Resolution Chemical Depth Profiling of Solid Material Using a Miniature Laser Ablation/Ionization Mass Spectrometer

High-resolution chemical depth profiling measurements of copper films are presented. The 10 μm thick copper test samples were electrodeposited on a Si-supported Cu seed under galvanostatic conditions in the presence of particular plating additives (SPS, Imep, PEI, and PAG) used in the semiconductor industry for the on-chip metallization of interconnects. To probe the trend of these plating additives toward inclusion into the deposit upon growth, quantitative elemental mass spectrometric measurements at trace level concentration were conducted by using a sensitive miniature laser ablation ionization mass spectrometer (LIMS), originally designed and developed for in situ space exploration. An ultrashort pulsed laser system (τ ∼ 190 fs, λ = 775 nm) was used for ablation and ionization of sample material. We show that with our LIMS system, quantitative chemical mass spectrometric analysis with an ablation rate at the subnanometer level per single laser shot can be conducted. The measurement capabilities of our instrument, including the high vertical depth resolution coupled with high detection sensitivity of ∼10 ppb, high dynamic range ≥10(8), measurement accuracy and precision, is of considerable interest in various fields of application, where investigations with high lateral and vertical resolution of the chemical composition of solid materials are required, these include, e.g., wafers from semiconductor industry or studies on space weathered samples in space research.

A method to suppress dielectric breakdowns in liquid argon ionization detectors for cathode to ground distances of several millimeters

We present a method to reach electric field intensity as high as 400 kV/cm in liquid argon for cathode-ground distances of several millimeters. This can be achieved by suppressing field emission from the cathode, overcoming limitations that we reported earlier.

Irrigation development in Eritrea: potentials and constraints: Proceedings of the workshop of AEAS and SLM Programme Eritrea

Development of irrigation, which is of crucial importance in Eritrea, is perceived by many as the main technique for improving the precarious food security situation in this Sahelian country in the Horn of Africa. The present publication presents the outcome of a nationwide workshop held in 2003, which brought together administrators, scientists, and members of public development agencies and NGOs. These workshop participants presented experiences, lessons learnt, and ideas about how to move forward in relation to development of irrigation in Eritrea. Specifically, the publication deals with the following broad themes, lessons learnt, and experiences in Eritrea: · spate irrigation systems and measurement of performance, as well as experience with modernisation of spate irrigation systems in Eritrea · small-scale irrigation systems and their potentials and pitfalls, including development of low-cost micro irrigation · climate and irrigation, including rainfall forecasts · socio-economic aspects of irrigation, including gender questions, institutional requirements, and irrigation and livelihoods The publication contains an extensive summary in the Tigrinya language, in order to facilitate access to the key findings by local non-English-speaking stakeholders in irrigation development.

Contrast agents and ionization with respect to safety for patients and doctors

In hemodialysis patients, radiographic imaging with iodinated contrast medium (ICM) application plays a central role in the diagnosis and/or follow-up of disease-related conditions. Therefore, safety aspects concerning ICM administration and radiation exposure have a great impact on this group of patients. Current hardware and software improvements including the design and synthesis of modern contrast compounds allow the use of very small amounts of ICM in concert with low radiation exposure. Undesirable ICM side effects are divided into type A (predictable reactions such as heat feeling, headache, and contrast-induced acute kidney injury, for example) and type B (nonpredictable or hypersensitivity) reactions; this chapter deals with the latter. The first onset cannot be prevented. To prevent hypersensitivity upon reexposure of ICM, an allergological workup is recommended. If this is not possible and ICM is necessary, the patient should receive a premedication (H1 antihistamine with or without corticosteroids). Current imaging hardware and software improvements (e.g. such as additional filtration of the X-ray beam) allow the use of very small amount of ICM and small X-ray doses. Proper communication among the team involved in the treatment of a patient may allow to apply imaging protocols and efficient imaging strategies limiting radiation exposure to a minimum. Practical recommendations will guide the reader how to use radiation and ICM efficiently to improve both patient and staff safety.

Object-Based Customization of Learning Content: Potentials and Pitfalls

Specification consortia and standardization bodies concentrate on e-Learning objects to en-sure reusability of content. Learning objects may be collected in a library and used for deriv-ing course offerings that are customized to the needs of different learning communities. How-ever, customization of courses is possible only if the logical dependencies between the learn-ing objects are known. Metadata for describing object relationships have been proposed in several e-Learning specifications. This paper discusses the customization potential of e-Learning objects but also the pitfalls that exist if content is customized inappropriately.

Differential effect of elevated intralabyrinthine pressure on ocular vestibular evoked myogenic potentials elicited by air conducted sound and bone conducted vibration

Recently, ocular vestibular evoked myogenic potentials (oVEMP) have emerged as a tool for assessment of utricular function. They are short-latency myogenic potentials which can be elicited in response to vestibular stimulation, e.g. by air-conducted sound (ACS) or bone-conducted vibration (BCV) (reviewed in (Kantner and Gurkov, 2012)). Otolithic afferent neurons trigger reflexive electromyographic activity of the extraocular muscles which can be recorded beneath the eye contralateral to the stimulated ear by use of surface electrodes.

Chemical Composition of Micrometer-Sized Filaments in an Aragonite Host by a Miniature Laser Ablation/Ionization Mass Spectrometer

Detection of extraterrestrial life is an ongoing goal in space exploration, and there is a need for advanced instruments and methods for the detection of signatures of life based on chemical and isotopic composition. Here, we present the first investigation of chemical composition of putative microfossils in natural samples using a miniature laser ablation/ionization time-of-flight mass spectrometer (LMS). The studies were conducted with high lateral (similar to 15 mu m) and vertical (similar to 20-200 nm) resolution. The primary aim of the study was to investigate the instrument performance on micrometer-sized samples both in terms of isotope abundance and element composition. The following objectives had to be achieved: (1) Consider the detection and calculation of single stable isotope ratios in natural rock samples with techniques compatible with their employment of space instrumentation for biomarker detection in future planetary missions. (2) Achieve a highly accurate chemical compositional map of rock samples with embedded structures at the micrometer scale in which the rock matrix is easily distinguished from the micrometer structures. Our results indicate that chemical mapping of strongly heterogeneous rock samples can be obtained with a high accuracy, whereas the requirements for isotope ratios need to be improved to reach sufficiently large signal-to-noise ratio (SNR). Key Words: Biogenicity-Biomarkers-Biosignatures-Filaments-Fossilization. Astrobiology 15, 669-682.

Segmented ionization chambers for beam monitoring in hadrontherapy.

Segmented ionization chambers represent a good solution to monitor the position, the intensity and the shape of ion beams in hadrontherapy. Pixel and strip chambers have been developed for both passive scattering and active scanning dose delivery systems. In particular, strip chambers are optimal for pencil beam scanning, allowing for spatial and time resolutions below 0.1 mm and 1 ms, respectively. The MATRIX pixel and the Strip Accurate Monitor for Beam Applications (SAMBA) detectors are described in this paper together with the results of several beam tests and industrial developments based on these prototypes.

Electrogram analysis and pacing are complimentary for recognition of abnormal conduction and far-field potentials during substrate mapping of infarct-related ventricular tachycardia.

BACKGROUND Mapping to identify scar-related ventricular tachycardia re-entry circuits during sinus rhythm focuses on sites with abnormal electrograms or pace-mapping findings of QRS morphology and long stimulus to QRS intervals. We hypothesized that (1) these methods do not necessarily identify the same sites and (2) some electrograms are far-field potentials that can be recognized by pacing. METHODS AND RESULTS From 12 patients with coronary disease and recurrent ventricular tachycardia undergoing catheter ablation, we retrospectively analyzed electrograms and pacing at 546 separate low bipolar voltage (<1.5 mV) sites. Electrograms were characterized as showing evidence of slow conduction if late potentials (56%) or fractionated potentials (76%) were present. Neither was present at (13%) sites. Pacing from the ablation catheter captured 70% of all electrograms. Higher bipolar voltage and fractionation were independent predictors for pace capture. There was a linear correlation between the stimulus to QRS duration during pacing and the lateness of a capturing electrogram (P<0.001), but electrogram and pacing markers of slow conduction were discordant at 40% of sites. Sites with far-field potentials, defined as those that remained visible and not captured by pacing stimuli, were identified at 48% of all pacing sites, especially in areas of low bipolar voltage and late potentials. Initial radiofrequency energy application rendered 74% of targeted sites electrically unexcitable. CONCLUSIONS Far-field potentials are common in scar areas. Combining analysis of electrogram characteristics and assessment of pace capture may refine identification of substrate targets for radiofrequency ablation.