Primary Cs Research Articles

One-pot synthesis of functionalized 4-oxo-2-thioxo-1,3-thiazinanes from primary amines, CS2, and itaconic anhydride

An efficient synthesis of 2-(3-alkyl-4-oxo-2- thioxo-1,3-thiazinan-5-yl)acetic acids is described via a three-component reaction between primary amines, CS(2), and itaconic anhydride.

Adhesion development and morbidity after repeat cesarean delivery

The purpose of this study was to evaluate the development and implications of intraabdominal adhesions after repeat cesarean section delivery (CS). We reviewed the charts of 1283 women who underwent repeat CS and 203 other women who underwent primary CS. Primary outcome measures were incidence and extent of adhesions, incision-to-delivery interval, and operating time. No adhesions were found in primary CS. Compared with those women with a second CS (24.4%), significantly more women had adhesions after 3 CSs (42.8%; 95% confidence interval [CI], 0.84-0.99). Compared with a first CS (7.7 +/- 0.3 minutes), the delivery time was significantly longer at subsequent CSs (second CS, 9.4 +/- 0.1 minutes; 95% CI, 1-2; third CS, 10.6 +/- 0.3 minutes; 95% CI, 2-4; >or= 4 CSs, 10.4 +/- 0.1 minutes; 95% CI, 1-2). However, complication rates in those women with >or= 2 CSs were comparable with primary CS. Increased adhesion development and a longer time to delivery were found with each subsequent CS.

Absolute frequency measurement of the magnesium intercombination transitionS01→P13

We report on a frequency measurement of the $(3{s}^{2})^{1}S_{0}\ensuremath{\rightarrow}(3s3p)^{3}P_{1}$ clock transition of $^{24}\mathrm{Mg}$ on a thermal atomic beam. The intercombination transition has been referenced to a portable primary Cs frequency standard with the help of a femtosecond fiber laser frequency comb. The achieved uncertainty is $2.5\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}12}$, which corresponds to an increase in accuracy of six orders of magnitude compared to previous results. The measured frequency value permits the calculation of several other optical transitions from $^{1}S_{0}$ to the $^{3}P_{J}$-level system for $^{24}\mathrm{Mg}$, $^{25}\mathrm{Mg}$, and $^{26}\mathrm{Mg}$. We describe in detail the components of our optical frequency standard such as the stabilized spectroscopy laser, the atomic beam apparatus used for Ramsey-Bord\'e interferometry, and the frequency comb generator and discuss the uncertainty contributions to our measurement including the first- and second-order Doppler effect. An upper limit of $3\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}13}$ in $1\phantom{\rule{0.3em}{0ex}}\mathrm{s}$ for the short-term instability of our optical frequency standard was determined by comparison with a quartz oscillator disciplined to the signal received from the global positioning system (GPS).

Computer simulation of MC-SNICS for performance improvements

Increasing ion source current output while keeping the beam emittance small is a key for improving measurement throughput and quality of an accelerator mass spectrometry (AMS) system. The NEC MC-SNICS ion sources have widely been used for AMS around the world. In this work, a computer simulation study on MC-SNICS ion source was carried out using the code PBGUNS. The primary Cs+ beam is simulated as space-charge limited emission from the ionizer surface. The secondary negative ion beam is simulated in the presence of the space-charge induced by both the primary and the secondary beam. Two different configurations of the MC-SNICS have been studied: the original factory version and the UC Irvine modified version. The latter has a 0.668in. radius spherical ionizer and an immersion lens at cathode potential with the original Cs focus lens removed. Simulation showed that the modified version provides more intense and better focused Cs+ beam at the cathode target, hence higher negative ion production from the sample by sputtering. The new arrangement of Einzel-preacceleration section of the MC-SNICS at UC Irvine was also simulated and discussed. Simulation results are in good agreement with the experimental observations made at UC Irvine. Hints for selection of an immersion lens geometry have been obtained.

Trends in mode of delivery of twin gestations in the united states

LISA RICE, ROBERT BONEBRAKE, MICHAEL BARSOOM, Creighton University, Obstetrics and Gynecology, Omaha, Nebraska OBJECTIVE: To evaluate the trends in delivery mode of twin gestations in the United States from 1990 and 2000 and neonatal outcomes. STUDY DESIGN: This is a population-based retrospective cohort study evaluating all twin deliveries in the US, occurring in 1990 and 2000, identified using the CDC/NCHS natality database. Exclusion criteria were EGA ! 24 weeks, !500 g, placenta previa and major fetal anomalies. Variables evaluated were maternal demographics, obstetric history, intrapartum and neonatal outcomes. Primary outcome was mode of delivery. Secondary outcomes included 5 minute Apgar !5, respiratory distress(RDS), need for ventilatory support, and birth injury. Descriptive statistics using two-tailed Chi-squared and Fisher’s exact tests were used with significance at p !0.05. RESULTS: 44,400 and 56,788 twin gestations from 1990 and 2000, respectively, were included. There were significantly more primary CS in 2000 regardless of fetal presentation. In 1990, there were significantly more infants with 5 minute Apgars ! 5. In 2000, there were significantly more cases of RDS, need for ventilatory support, and birth injury. Analyzing the data from 2000 by mode of delivery, CS was associated with a significant reduction in birth injuries and 5 minute Apgars !5 compared to vaginal delivery. This persisted when controlled for EGA. There was significantly more RDS and need for ventilatory support in the CS group, which persisted when controlled for presentation. CONCLUSION: This demonstrates the dramatic shift in the mode of delivery for twin gestations from 1990 to 2000, specifically in VTX/VTX twins. More twin gestations were delivered by CS in 2000, regardless of presentation. There was a significant rise in the number of CS performed for VTX/VTX presentation. CS was associated with a significant decrease in birth injuries and 5 minute Apgars ! than 5 compared to vaginal twins. There was noted to be an increase in RDS and ventilatory support in the CS group. Based on this data, CS in VTX/VTX twin gestations appear to be associated with fewer birth injuries and 5 minute Apgars !5.

Hydrogen Detection in Individual Diamond Grains on Si(100) Substrate Grown by Microwave-Assisted Chemical Vapor Deposition

Secondary ion mass spectrometry is applied to the detection of hydrogen in individual diamond grains 1–4 µm in diameter. In the analysis, the primary Cs ion beam was fine-tuned at diameters of 50–200 nm on the surface, and then a combination of presputtering and spot analysis was carried out along a line defined in the scanned 12C image with a high lateral resolution. The intensity ratios of (H/12C) in the (111) and (100) planes were determined as having values of 1.36×10-2 and 3.2×10-3, respectively. The value obtained in the (100) plane is background in the analysis. The results demonstrate the potential of the analytical technique for the detection of impurities in materials science.

Implementing a SIMS ion source on the NRL trace element accelerator mass spectrometer

The NRL trace element accelerator mass spectrometer facility has recently added a modified Cameca IMS 6F SIMS instrument as a high-performance ion source, providing the advantages of accelerator mass spectrometry to SIMS analysis. These advantages include removal of molecular interferences, a greatly reduced background, and composition analysis using molecular ions (after breaking them into atomic constituents before detection). This last feature compensates for a requirement to use only negative secondary ions, as it enables measurement of electropositive elements. In addition, the NRL facility provides for parallel mass analysis, thus improving isotope ratio precision and practical sensitivity. Spatial analysis of the sample is still provided by raster of the primary Cs beam. The modified Cameca includes the Cs primary column, sample chamber, and the secondary ion column up to the standard electrostatic analyzer. The NRL accelerator facility supplants the normal mass spectrometer portion of the IMS 6F instrument. Additional recent facility upgrades provide improved mass spectrometry performance, both for a prior radiocarbon ion source and the now installed SIMS. An example measurement, using silver ions, demonstrates the system's capabilities.

Progress in analytical imaging of the cell by dynamic secondary ion mass spectrometry (SIMS microscopy)

This paper reviews the most recent methodological advances in the field of biological imaging using dynamic secondary ion mass spectrometry (SIMS). After a short reminder of the basic principle of SIMS imaging, the latest high-resolution dynamic SIMS equipment is briefly described. This new ion nanoprobe (CAMECA NanoSIMS 50) has a lateral resolution of less than 50 nm with primary Cs+ ion, the ability to detect simultaneously 5 different ions from the same micro-volume and a very good transmission even at high mass resolution (60% at M/DeltaM=5000). Basic considerations related to sample preparation, mass resolution and primary ion implantation are given. The decisive capability of this new instrument, and more generally of high-resolution dynamic SIMS imaging in biology, are illustrated with the most recent examples of utilization.

Accuracy of Secondary Ion Mass Spectrometry Depth Profiling for Sub-keV As+ Implantation

The depth profiling of sub-keV As+ implantation for sub-10 nm junction formation was investigated. The tail slope of profiles measured by secondary ion mass spectrometry (SIMS) using 300 eV Cs+ was much gentler than that of simulated profiles. Model calculation considering the mixing effect due to Cs+ bombardment during SIMS measurement explained the SIMS tail well. This implies that accurate As depth profiling by simply lowering primary Cs+ energy is difficult because of ion gun limitations. At the surface region, a 1.4-nm-thick surface layer was found. This layer is considerably thick for the sub-10 nm junction and is thicker than 0.4 nm for 5 keV implantation.

Transport of 13C-oleate in adipocytes measured using multi imaging mass spectrometry

The mechanism of long chain free fatty acid (FFA) transport across cell membranes is under active investigation. Here we describe the use of multi imaging mass spectrometry (MIMS) to monitor intracellular concentrations of FFA and provide new insight into FFA transport in cultured adipocytes. Cells were incubated with 13C-oleate:BSA and either dried directly or dried after washing with a medium deprived of 13C-oleate:BSA. Cells were analyzed with MIMS using a scanning primary Cs+ ion beam and 12C-, 13C-, 12C14N-, 13C14N-) (or 12C 15N-) were imaged simultaneously. From these quantitative images the values of the 13C/ 12C ratios were determined in the intracellular lipid droplets, in the cytoplasm and outside the 3T3F442A adipocytes. The results indicate that after incubation with 13C-oleate:BSA the droplet 13C/ 12C ratio was 15 +/- 6%. This value is about 14-fold higher than the 13C/ 12C terrestrial ratio (1.12%). After washing the 13C-oleate:BSA, the droplet 13C/ 12C ratios decreased to 1.6 +/- 0.1%, about 40% greater than the natural abundance. Results for washed cells indicate that relatively little FFA was esterified. The unwashed cell results, together with the value of the lipid water partition coefficient, reveal that intracellular unbound FFA (FFAu) concentrations were on average about 4.5-fold greater than the extracellular FFAu concentrations. These results are consistent with the possibility that FFA may be pumped into adipocytes against their electro-chemical potential. This work demonstrates that MIMS can be used to image and quantitate stable isotope labeled fatty acid in intracellular lipid droplets.

Carbon-sulfur bond cleavage in Bis(N-alkyldithiocarbamato)cadmium(II) complexes: heterolytic desulfurization coupled to topochemical proton transfer.

Three bis(N-alkyldithiocarbamato)cadmium(II) complexes [Cd(S(2)CNHR)(2)] (1, R = n-C(3)H(7); 2, R = n-C(5)H(11); 3, n-C(12)H(25)) were prepared by metathesis of the corresponding lithium salt, Li[S(2)CNHR], with cadmium chloride. The crystal structures of 2 and 3 consist of planar molecular units of [Cd(S(2)CNHR)(2)] connected by intermolecular Cd.S interactions to give a one-dimensional chain. The chains are connected by a network of intermolecular N-H.S hydrogen bonds between the dithiocarbamato nitrogen atom and bridging sulfur atoms in neighboring chains. In solution, the (113)Cd NMR spectrum of 2 is dependent on concentration and temperature, indicative of a dimerization equilibrium mediated by similar Cd.S intermolecular bridging interactions. In the solid state, thermal gravimetric analyses show that all three complexes decompose smoothly via a heterolytic C-S bond cleavage reaction to give the corresponding alkyl isothiocyanate and cadmium sulfide as the primary products, with the formation of primary amine and CS(2) as coproducts. These products can result only from the net transfer of protons between N-alkyldithiocarbamato ligands in the solid state. Thus, the C-S bond cleavage reaction is interpreted in terms of the topochemical arrangement of molecular units in the crystalline state, which provides a pathway for proton transfer between ligands via N-H.S hydrogen bonds. Decomposition was also initiated by addition of a tertiary amine to a solution of [Cd(S(2)CNHR)(2)]. This confirms that C-S bond cleavage must be coupled to deprotonation of the -NH group, and explains why dialkylated derivatives [Cd(S(2)CNR(2))(2)] are inert to this particular mode of C-S bond cleavage. This system thus constitutes an unusual example of heterolytic, nonoxidative C-S bond cleavage that appears to proceed by a topochemical transfer of protons, which has implications for C-S bond cleavage processes in single-source precursors for II-VI semiconductor materials.

Desorption kinetics of radiocesium from subsurface sediments at Hanford Site, USA

The desorption of 137Cs + was investigated on sediments from the United States Hanford site. Pristine sediments and ones that were contaminated by the accidental release of alkaline 137Cs +-containing high level nuclear wastes (HLW, 2 × 10 6 to 6 × 10 7 pCi 137Cs +/g) were studied. The desorption of 137Cs + was measured in Na +, K +, Rb +, and NH 4 +electrolytes of variable concentration and pH, and in presence of a strong Cs +-specific sorbent (self-assembled monolayer on a mesoporous support, SAMMS). 137Cs + desorption from the HLW-contaminated Hanford sediments exhibited two distinct phases: an initial instantaneous release followed by a slow kinetic process. The extent of 137Cs + desorption increased with increasing electrolyte concentration and followed a trend of Rb + ≥ K + > Na + at circumneutral pH. This trend followed the respective selectivities of these cations for the sediment. The extent and rate of 137Cs + desorption was influenced by surface armoring, intraparticle diffusion, and the collapse of edge-interlayer sites in solutions containing K +, Rb +, or NH 4 +. Scanning electron microscopic analysis revealed HLW-induced precipitation of secondary aluminosilicates on the edges and basal planes of micaceous minerals that were primary Cs + sorbents. The removal of these precipitates by acidified ammonium oxalate extraction significantly increased the long-term desorption rate and extent. X-ray microprobe analyses of Cs +-sorbed micas showed that the 137Cs + distributed not only on mica edges, but also within internal channels parallel to the basal plane, implying intraparticle diffusive migration of 137Cs +. Controlled desorption experiments using Cs +-spiked pristine sediment indicated that the 137Cs + diffusion rate was fast in Na +-electrolyte, but much slower in the presence of K + or Rb +, suggesting an effect of edge-interlayer collapse. An intraparticle diffusion model coupled with a two-site cation exchange model was used to interpret the experimental results. Model simulations suggested that about 40% of total sorbed 137Cs + was exchangeable, including equilibrium and kinetic desorbable pools. At pH 3, this ratio increased to 60–80%. The remainder of the sorbed 137Cs + was fixed or desorbed at much slower rate than our experiments could detect.

A modified ion sputter source with increased lifetime

The Cs sputter ion source HVEE 860-C has shown significant erosion of inner parts after an operation time of some thousand hours. This is caused by Cs ions generated at hot surfaces outside the spherical ioniser surface. The calculated trajectories of these ions and the erosion patterns show an excellent correspondence. The suppression of the disturbing ions has resulted in increased lifetimes of the ion source and an improved focus of the primary Cs ions on the sputter target.

Useful yields of MCs x+ clusters: a cesium concentration-dependent study on the Cation Mass Spectrometer (CMS)

To optimize the advantageous quantification technique consisting in analyzing MCs x + clusters, the Laboratoire d’Analyse des Matériaux (LAM) has developed a new instrument specially dedicated to performing this kind of analysis. The Cation Mass Spectrometer (CMS) instrument leads to high MCs x + useful yields by allowing to reach an optimum value of the stationary Cs surface concentration, which is known to be a very critical parameter in MCs x + analysis due to its strong influence on the probability of secondary Cs + ionization. The present work focuses on the potential of the CMS instrument to vary the stationary Cs concentration over a large range and the benefits concerning the MCs x + useful yields resulting from this possibility. Analyses were performed on three different samples (Al, Si, Ni) while modifying the impact angle of the primary Cs + beam and in the Cs +–Ga + cobombardment mode. These techniques are shown to be complementary with respect to the covered ranges of cesium concentrations resulting in a complete range going from quasi 0 to some 30%. The observed variations of the useful yields are discussed in terms of the stationary Cs concentration produced during the analysis and the consequent variations of the Cs + ionization probability provoked by work function shifts which were determined by in-situ measurements. A comparison between the performances of the CMS and those of classic Cameca instruments shows, depending on the element, useful yield enhancements up to a factor 90 mainly due to work function conditions resulting in high Cs + ionization probabilities.

Cation Mass Spectrometer: towards an optimisation of MCs x+ cluster analysis

The Cation Mass Spectrometer (CMS) should lead to high MCs x + useful yields by allowing to reach an optimum value of the stationary Cs surface concentration, which is known to be a very critical parameter in MCs x + analysis due to its strong influence on the probability of secondary Cs + ionisation. For the present work, variations of the Cs concentration were obtained by modifying the impact angle of the primary Cs + beam and by bombarding the sample simultaneously with Cs + and Ga + beams. Results show that these techniques allow to cover a large and continuous range of Cs surface concentrations and to reach an optimisation of the MCs x + useful yields (enhancements up to a factor 100 compared to Cameca 4f and 6f instruments) mainly due to work function conditions resulting in high Cs + ionisation probabilities.

Work function change caused by alkali ion sputtering

In the presented work we performed an experimental study of the work function decrease for a silicon sample caused by Cs + ion bombardment. We varied the energy of primary Cs + ions as well as the angle of incidence in order to reach a different concentration of implanted cesium ions and to find a dependence of the work function change on the cesium surface concentration. A “surface dipoles” model was developed. The model based on the electronegativity concept considers formation of Si–Cs dipoles with corresponding dipole moment. An electric field of these dipoles results in a decrease of the work function, whereas a partly ionic character of Si–Cs bond increases the surface binding energy of cesium and, as a consequence, its surface concentration. A good correlation between the model and the experimental data was found.

A Synthesis of Aziridines from α‐Iodoenones.

AbstractFor Abstract see ChemInform Abstract in Full Text.

SIMS depth profiling of ultrashallow P, Ge and As implants in Si using MCs2+ ions

AbstractQuantitative determination of dose and junction depth in the source/drain region of future CMOS devices (typically 50 nm for the contact and 25 nm for the extension) requires SIMS instruments capable of measuring dopant profiles with high depth resolution and low detection limits. In this work we investigate the analytical usefulness of monitoring MCs2+ ions for semiconductor profiling of n‐type dopants such as P, Ge or As with a primary (Cs+ beam) impact energy of 1 keV on a SIMS Cameca IMS‐5f instrument. The results obtained on ultrashallow implants in Si and SiO2 indicate an improvement in the characterization by using the MCs2+ technique; this technique has the advantage over the MCs+ technique of providing higher useful yields for electronegative elements by up to 102 and can therefore be applied to perform more precise junction measurements in terms of concentration, dose, decay length and detection limit. Copyright © 2002 John Wiley & Sons, Ltd.

Characteristics of a direct metal ion beam deposition source

In this study, we examine the performance of a direct metal ion beam deposition (DMIBD) system which uses a Cs–mordenite pellet as the ion source. We describe design aspects of DMIBD and process parameters such as secondary ion yields, secondary ion energy distributions, secondary ion to atom arrival ratios and deposition rates for C, Al, Si, Ni, Cu, Ta, and W targets. During deposition, the secondary negative metal ion yield strongly depends on the primary Cs+ ion does and bombarding energy. Also, the deposition rate and ion to atom arrival ratios for various targets can be controlled by adjusting the primary Cs+ ion dose, Cs+ ion bombarding energy, and ion beam energy to fit the desired application.

A synthesis of aziridines from α-iodoenones

Aziridines were prepared from α-iodocycloenones in very good yield, by a Michael addition/cyclisation (Gabriel–Cromwell) process employing a slight excess of primary amine and Cs 2CO 3 as base at 95°C. Using chiral amines it was possible to prepare optically pure aziridines. The same method was also efficient for the synthesis of aziridines from acyclic α-halounsaturated compounds. 2-Oxoazabicycles reacted with several nucleophiles to afford α-heteroatom substituted cyclic enones in excellent yield.