Molecular imaging of in vivo calcium ion expression in area postrema of total sleep deprived rats: Implications for cardiovascular regulation by TOF-SIMS analysis

Excessive calcium influx in chemosensitive neurons of area postrema (AP) is detrimental for sympathetic activation and participates in the disruption of cardiovascular activities. Since total sleep deprivation (TSD) is a stressful condition known to harm the cardiovascular function, the present study is aimed to determine whether the in vivo calcium expression in AP would significantly alter following TSD by the use of time-of-flight secondary ion mass spectrometry (TOF-SIMS) and calretinin (a specific calcium sensor protein in AP neurons) immunohistochemistry. The results indicated that in normal rats, the calcium intensity was estimated to be 0.5 × 10⁵ at m/z 40.08. However, following TSD, the intensity for calcium ions was greatly increased to 1.2 × 10⁵. Molecular imaging revealed that after TSD, various strongly expressed calcium signals were distributed throughout AP with clear identified profiles instead of randomly scattered within this region in normal rats. Immunohistochemical staining corresponded well with ionic image in which a majority of calcium-enriched gathering co-localized with calretinin positive neurons. The functional significance of TSD-induced calcium augmentation was demonstrated by increased heart rate and mean arterial pressure, clinical markers for cardiovascular dysfunction. Considering AP-mediated sympathetic activation is important for cardiovascular regulation, exaggerated calcium influx in AP would render this neurocircuitry more vulnerable to over-excitation, which might serve as the underlying mechanism for the development of TSD-relevant cardiovascular deficiency.     

An upgraded TOF-SIMS VG Ionex IX23LS: Study on the negative secondary ion emission of III-V compound semiconductors with prior neutral cesium deposition

A TOF-SIMS VG Ionex IX23LS with upgraded data acquisition and control system was used to study the secondary emission of negative atomic and cluster ions of non-metallic elements (P, As and Sb) upon a 19 keV Ga⁺ bombardment of non-degenerated III-V semiconductors (GaP, GaAs, GaSb, InP, InAs and InSb) with prior neutral Cs deposition from a getter dispenser. It was found that surface cesiation enhances the peak intensity of all negative ion species; in the case of atomic ions, the greatest increase (360) was observed for P⁻ emitted from InP. Such an enhancement was larger for In-based than for Ga-based compounds. We explained that in terms of an electronegativity difference between the composing atoms of III-V semiconductors. The greater electronegativity difference (bond ionicity) of In-based compounds resulted in the greater Cs-induced work function decrease leading to a higher increase in the ionization probability of secondary ions.     

Novel monodisperse PEG-grafted polystyrene resins: synthesis and application in gel-phase C NMR spectroscopy

A series of novel polystyrene-oligo(oxyethylene) graft copolymers containing monodisperse PEG units (n = 2-12) have been synthesized and examined concerning their applicability for gel-phase ¹³C NMR spectroscopy. A strong correlation between the graft length and the line widths in the gel-phase spectra was observed. By grafting a PEG chain with only eight units, it was possible to obtain results similar to TentaGel resin. Additionally, TOF-SIMS images were recorded in order to evaluate the homogeneity of the resin.     

Effect of acrylic acid vapour on lubricated recording hard-disk media surfaces

Magnetic recording hard-disk drive may be attacked by many kinds of contaminations including vapours/gases. Vapour/gas contaminants are detrimental to magnetic heads, media and head-disk interfaces in hard-disk drive. Acrylic acid is a kind of gases released from drive components. In this study, the effects of acrylic acid vapour on the surface adsorption and corrosion of magnetic hard-disk media are investigated by TOF-SIMS. The related drive durability and failure property are discussed.     

Selective detection of organic compounds on modified polymer surfaces using TOF-SIMS in combination with derivatization

This investigation encompasses work in the development of TOF-SIMS methodology for the characterization of compounds formed during polymer surface modification. TOF-SIMS was used in this study in combination with selective derivatization reactions with hydroxyl group specific reagents. Derivatization techniques with group specific reagents provide a means of identifying functional groups in a complex matrix, along with significant enhancement of detection limits. The study proceeded in three steps. First, derivatives of organic compounds as a model compound were monitored to determine the suitability for detecting oxygenated species. Second, useful derivatization reactions were tested on functional groups in the synthetic polymer chains. Third, the methods thus developed were applied to polymer surfaces treated by plasma source ion implantation (PSII). 2-Fluoro-1-methylpyridinium derivatives were useful for characterization of organic alcohols and phenolic compounds. Analysis of organic compounds derivatized by these methods on polymeric materials demonstrated clearly that analysis in the presence of a carbonaceous matrix is possible. The results yielded evidence for the formation of hydroxyl species as the polymer is modified by PSII technique.     

TOF-SIMS depth profiling and element mapping on oxidized AlCrVN hard coatings

V-alloyed AlCrN hard coatings were deposited on silicon wafers (Si (100)) by reactive arc evaporation in a commercial coating system at 500 °C for 10 min, resulting in a coating thickness of ∼500 nm. The chemical composition of the stoichiometric coatings is constant at approximately Al_0.70Cr_0.05V_0.25N regardless of the applied bias voltage during deposition. Coatings synthesized at a low bias of −40 V show a dual-phase structure (hexagonal close-packed and face-centered cubic (fcc)), whereas coatings deposited at a high bias of −150 V have a metastable single-phase structure (face-centered cubic). All samples were oxidized for 15 min under 20 mbar O₂ atmosphere and at four different temperatures (550, 600, 650, and 700 °C). The oxidized coatings were subject to depth profiling and element mapping by a time of flight secondary ion mass spectrometry instrument, equipped with a Bi-cluster analysis gun and Cs⁺-sputter gun. The evaluation of the in-depth distribution of several elements and species points out distinctive differences in the oxidation behavior of the two different coatings, whereas element mapping shows the formation of islands made of oxidized vanadium and aluminum species as the top-most layer of the single-phase (fcc) coating at temperatures above 650 °C.     

Localization of Na and K in rat cerebellum with imaging TOF-SIMS

High pressure-frozen (HPF), freeze-fractured and freeze-dried rat cerebellum was analyzed with imaging TOF-SIMS equipped with a Bi-cluster ion source. Data were collected separately as spectra of high mass resolution m/Δm > 8000 and images of high lateral resolution <700 nm. Images were made showing the localization of the peaks m/z = 22.99, and m/z = 39.1.Topographical effects were noted due to the freeze fracture method. This effect was compensated by normalizing images of specific secondary ions to the intensity of total secondary ions and by making PCA analysis of the image. The results showed that potassium ions were localized in blood vessels and cortex cells and sodium ions were localized in blood vessels and cerebellar interstitial tissue and in the nuclei of some cells. The sodium ion concentration was found to be higher in blood vessels than in the interstitium.     

表面残留有机沾污物的TOF－SIMS及XPS研究

飞行时间次级离子质谱（ＴＯＦ－ＳＩＭＳ）结合Ｘ射线光电子能谱（ＸＰＳ）分析了用化学方法清洗后、银片上残留的未知的有机物。结果显示，有机沾污物主要是一些含１８～３０碳原子、碳链饱和度很高的酮类和酯类化合物；个别有机物可能是硬脂酰胺。这种结构特点使有机物中的Ｃ＝Ｏ基团易于采取氧原子指向基体表面的取向，通过带部分负电荷的氧原子与金属基体镜像力的作用而增强粘附。ＴＯＦ－ＳＩＭＳ二维离子像显示有机沾污物在银片表面上呈极稀薄的均匀分布。     

Behcet brain tissue identified with increased levels of Si and Al

Behcet disease is a multi-system disorder with still uncertain chemical causality. Chemical composition of molecules and elements in a human brain tissue of Behcet diseased patient is of interest. Time-of-flight secondary ion mass spectrometry is used to provide complex composition in Behcet disease and control tissues. Determined organic compounds are represented by fragments of carbohydrates, phospholipids, amino acids, and peptides in both samples without any qualitative differences. Trace heavy elements as Fe, Zn, and Cu are identified in Behcet disease tissue with increased intensities by only an averaged factor of 2.2 in comparison to the control. The significant differences between the control and Behcet disease tissues are in the presence of Si and Al. These two elements have significantly higher intensities by an averaged factor of 10.0 in Behcet disease tissue. The origin of Al and Si occurrence and the chronology of their accumulation are not clear, moreover this observation supports a significance of chemical characterization in an early stage of disease.     

Extremely low-energy projectiles for SIMS using size-selected gas cluster ions

A new cluster time-of-flight secondary ion mass spectrometry (TOF-SIMS) was developed using a size-selected gas cluster ion as a projectile. Since a large gas cluster ion can generate many low-energy constituent atoms in a collision with the surface, it causes multiple and ultra low-energy sputtering. The mean kinetic energy of constituent atoms is provided by dividing the acceleration energy of the gas cluster ion by the number of constituent atoms. Therefore, the sputtering can be controlled to minimize the decomposition of sample molecules and substrate material by precisely adjusting the number of constituent atoms (the cluster size) and/or acceleration energy of the gas cluster ion. The cluster size was selected on the basis of the time-of-flight method using two ion deflectors attached along the ion-beam line. A high resolution of 11.7 was achieved for the cluster size/size width (M/ΔM) of Ar-cluster ions.