ToF-SIMS Depth Profiling of PS-b-PMMA Block Copolymers Using Arn+, C60++, and Cs+ Sputtering Ions.

Time-of-flight secondary ion mass spectrometry (ToF-SIMS) is a high performance tool for molecular depth profiling of polymer films, in particular when they are structured in microphases. However, a major issue is the degradation of polymer materials under ion irradiation in reactions such as cross-linking, chain breaking, or reorganization processes of polymers which have been demonstrated for materials such as polystyrene (PS) and poly(methyl methacrylate) (PMMA). This work aims at comparing ToF-SIMS molecular depth profiling of structured polymers (polystyrene (PS)-b-polymethyl methacrylate (PMMA) block copolymers (BCP)) using either ultralow energy cesium or the more recently introduced C60++ (under NO dosing and with sample cooling) and argon cluster ion beams (using Ar1500+ ions at 5 keV). The latter improved the quality of the depth profiles, especially the argon cluster ion beam, as it is characterized by a greater homogeneity for the sputter yields of PS and PMMA. No significant artifacts were observed, and this was confirmed by the comparison of depth profiles obtained from films with variable thickness, annealing time, and morphology (cylindrical blocks vs spherical blocks). Comparison to a theoretical model (hexagonal centered pattern) ensured that the ToF-SIMS depth profiles described the real morphology and may thus be a relevant characterization tool to verify the morphology of the films as a function of the deposition parameters.

Nitric oxide assisted C60 secondary ion mass spectrometry for molecular depth profiling of polyelectrolyte multilayers.

RATIONALE: Secondary ion mass spectrometry (SIMS) with polyatomic primary ions provides a successful tool for molecular depth profiling of polymer systems, relevant in many technological applications. Widespread C60 sources, however, cause in some polymers extensive damage with loss of molecular information along depth. We study a method, based on the use of a radical scavenger, for inhibiting ion-beam-induced reactions causing sample damage. METHODS: Layered polystyrene sulfonate and polyacrylic acid based polyelectrolyte films, behaving differently towards C60 beam-induced damage, were selected and prepared as model systems. They were depth profiled by means of time-of-flight (TOF)-SIMS in dual beam mode, using fullerene ions for sputtering. Nitric oxide was introduced into the analysis chamber as a radical scavenger. The effect of sample cooling combined with NO-dosing on the quality of depth profiles was explored. RESULTS: NO-dosing during C60-SIMS depth profiling of >1 micrometer-thick multilayered polyelectrolytes allows detection, along depth, of characteristic fragments from systems otherwise damaged by C60 bombardment, and increases sputtering yield by more than one order of magnitude. By contrast, NO has little influence on those layers that are well profiled with C60 alone. Such leveling effect, more pronounced at low temperature, leads to a dramatic improvement of profile quality, with a clear definition of interfaces. CONCLUSIONS: NO-dosing provides a tool for extending the applicability, in SIMS depth profiling, of the widely spread fullerene ion sources. In view of the acceptable erosion rates on inorganics, obtainable with C60, the method could be of relevance also in connection with the 3D-imaging of hybrid polymer/inorganic systems.

Laparoscopic cholecystectomy in the treatment of acute cholecystitis: comparison of outcomes and costs between early and delayed cholecystectomy.

BACKGROUND: Several trials showed that early laparoscopic cholecystectomy is superior to delayed laparoscopic cholecystectomy for the treatment of acute cholecystitis. However actual practice does not conform to current evidence. The aim of this study is to compare outcomes and total hospital costs between early and delayed laparoscopic cholecystectomy for acute cholecystitis. PATIENTS AND METHODS: A retrospective analysis of patients with acute cholecystitis that underwent a laparoscopic cholecystectomy at our institutions was performed. Patients were divided into 2 groups on the basis of the treatment received and statistical analysis was performed. RESULTS: The study included 91 patients, 52 female and 39 male, with a mean age of 55. Early surgery was performed in 32 cases and delayed surgery in 59 cases. The two groups were comparable for demographics data and severity of disease on admission. There was a no significant difference (p = 0.174) in the mean operative time between early (54.8 min) and delayed group (47.8 min). Conversion rate was higher in the early group (34.3% vs. 20.3%), but difference was not statistically significant (p = 0.223). The overall complications rate was comparable (18.7% early vs. 16.9% delayed, p = 0.941). Length of postoperative stay (4.3 vs. 3.8 days) was similar (p = 0.437), but total hospital stay was significantly 4 days shorter in the early group (p < 0.0001). The mean total cost was higher for the delayed group (4171 vs. 6041), with a significant difference of 1870 Euro (p < 0.0001). CONCLUSIONS: Early laparoscopic cholecystectomy has an outcome comparable to the delayed procedure, with a shorter total hospital stay and lower total costs, and it should be considered as the preferred approach in treatment of acute cholecystitis.

Preoperative risk factors for conversion from laparoscopic to open cholecystectomy.

BACKGROUND: Laparoscopic cholecystectomy has become the standard treatment for symptomatic gallstones. However, a conversion to open surgery is sometimes still required to complete the procedure safely. The aim of this study is to identify the predictive factors of conversion from laparoscopic to open cholecystectomy in both elective and emergency cases. PATIENTS AND METHODS: A retrospective review of all patients underwent laparoscopic cholecystectomy for symptomatic gallstones from January 2011 to October 2013 was performed. Data considered for analysis were: demographic data, comorbidities, preoperative laboratory values, preoperative ERCP, indication for surgery, and the timing of the intervention in acute cholecystitis. Conversion to open cholecystectomy was chosen as the dependent variable for both, univariate and multivariate analysis. RESULTS: 414 patients underwent laparoscopic cholecystectomy. 245 were female (59.1%) and 169 (40.8%) male, with a mean age of 51.7±16.4 years. The indication for surgery was acute cholecystitis in 91 cases (21.9%). Lithiasis of the bile duct was found in 40 patients (9.6%), and it was identified preoperatively in 37 patients, all treated with a preoperative ERCP. Conversion to open occurred in 33 cases (7.9%). Univariate analysis revealed as risk factor for conversion: increased age, acute cholecystitis, comorbidities, elevated white blood cell count, increased level of aspartate aminotransferase, alanine aminotransferase, alkaline phosphatase, gamma glutamyl transpeptidase, C-reactive protein, and fibrinogen. Multivariate logistic regression analysis showed that acute cholecystitis (OR 5.63) and age > 65 years (OR 3.025) were independent predictive factors for conversion. CONCLUSIONS: These patients should be properly informed of their increased risk of conversion and should be operated by surgeons skilled in laparoscopic procedures to reduce this risk.

Improving secondary ion mass spectrometry C60(n+) sputter depth profiling of challenging polymers with nitric oxide gas dosing.

Organic depth profiling using secondary ion mass spectrometry (SIMS) provides valuable information about the three-dimensional distribution of organic molecules. However, for a range of materials, commonly used cluster ion beams such as C60(n+) do not yield useful depth profiles. A promising solution to this problem is offered by the use of nitric oxide (NO) gas dosing during sputtering to reduce molecular cross-linking. In this study a C60(2+) ion beam is used to depth profile a polystyrene film. By systematically varying NO pressure and sample temperature, we evaluate their combined effect on organic depth profiling. Profiles are also acquired from a multilayered polystyrene and polyvinylpyrrolidone film and from a polystyrene/polymethylmethacrylate bilayer, in the former case by using an optimized set of conditions for C60(2+) and, for comparison, an Ar2000(+) ion beam. Our results show a dramatic improvement for depth profiling with C60(2+) using NO at pressures above 10(-6) mbar and sample temperatures below -75 °C. For the multilayered polymer film, the depth profile acquired using C60(2+) exhibits high signal stability with the exception of an initial signal loss transient and thus allows for successful chemical identification of each of the six layers. The results demonstrate that NO dosing can significantly improve SIMS depth profiling analysis for certain organic materials that are difficult to analyze with C60(n+) sputtering using conventional approaches/conditions. While the analytical capability is not as good as large gas cluster ion beams, NO dosing comprises a useful low-cost alternative for instruments equipped with C60(n+) sputtering.

Pulsed rf-GD-TOFMS for depth profile analysis of ultrathin layers using the analyte prepeak region.

Direct solid analysis of ultrathin layers is investigated using pulsed radiofrequency (rf) glow discharge (GD) time-of-flight mass spectrometry (TOFMS). In particular, previous studies have always integrated the detected ion signals in the afterglow region of the rf-GD pulse, which is known to be the most sensitive one. Nevertheless, the analytical capabilities of other pulse time regions have not been evaluated in detail. Therefore, in this work, we investigate the analyte prepeak region, which is the pulse region where the analyte ions peak after the initial sputtering process of each GD pulse, aiming at obtaining improved depth profile analysis with high depth resolution and with minimum polyatomic spectral interferences. To perform these studies, challenging ultrathin Si-Co bilayers deposited on a Si substrate were investigated. The thickness of the external Si layer was 30 nm for all the samples, whilst the internal Co layer thicknesses were 30, 10, 5, 2 and 1 nm, respectively. It should be remarked that the top layer and the substrate have the same matrix composition (Si > 99.99%). Therefore, the selected samples are suitable to evaluate the response of the Si ion signal in the presence of an ultrathin Co layer as well as the possible oxygen contaminations or its reactions. Additionally, these samples have been evaluated using time-of-flight secondary ion mass spectrometry, and the results compare well to those obtained by our pulsed rf-GD time-of-flight mass spectrometry results.

Polymer screening by radiofrequency glow discharge time-of-flight mass spectrometry.

The aim of this work is to optimise and evaluate radiofrequency glow discharge (RF GD) time-of-flight mass spectrometry (TOFMS) for identification of organic polymers. For this purpose, different polymers including poly[methylmethacrylate], poly[styrene], polyethylene terephthalate-co-isophthalate and poly[alpha-methylstyrene] have been deposited on silicon wafers and the RF GD-TOFMS capabilities for qualitative identification of these polymeric layers by molecular depth profiling have been investigated. Although some molecular information using the RF continuous mode is available, the pulsed mode offers a greater analytical potential to characterise such organic coatings. Some formed polyatomic ions have proved to be useful to identify the different polymer layers, confirming that layers having similar elemental composition but different polymer structure could be also differentiated and identified.

Supramolecular self-assembled multilayers of terpyridine-functionalized perylene bisimide metal complexes.

A terpyridine-functionalized perylene bisimide chromophore (TPBI) has been used as a building block in the stepwise, layer-by-layer fabrication of self-assembled Fe-TPBI multilayers on gold, with the assembled supramolecular chains oriented approximately perpendicular to the gold surface. Time-resolved spectroscopy measurements seem to indicate that the energy absorbed by the multilayer is promptly dissipated to the gold surface by ultrafast processes.

Environmental radioactivity at Stromboli (Aeolian Islands).

HPGe gamma spectrometry, thermoluminescence dosimetry, X-ray diffractometry and fluorescence techniques have been used to analyze the natural radionuclides content of soil and rock samples, air kerma and geochemical features on the island of Stromboli, belonging to the Aeolian Islands, in the Mediterranean Sea. The 214Bi, 238Ac, and 40K contents obtained are in agreement with the magmatic evolution of the rock formation, as shown by the correlations between radionuclide and chemical elements abundacies, depending on the various magmatic differentiation mechanisms. Correlations between radiometric, lithological and geochemical data have been assessed in order to obtain some hints on the geochronology of the magmatic products.

A new polytopic bis-diazacrown-ether-polypyridine ligand and its complexes with Zn(II) salts and mononuclear and dendritic Ru(II) precursors. Synthesis, absorption spectra, redox behavior, and luminescence properties.

The new polytopic receptor 1 containing two terpyridine, one phenanthroline, and two diazacrown-ether sites has been prepared using a modular approach. Such a new species contains several pieces of information in its structure which can be processed by different metal ions to give different supramolecular inorganic architectures. Actually, reaction of 1 with Zn(CH(3)COO)(2) in methanol, and subsequent anion exchange, afforded the intramolecular ring-type [Zn(1)](2+) complex, which appears to be formed by a self-assembling reaction. A different synthetic approach, stepwise synthesis, allowed us to synthesize the two multicomponent compounds [(bpy)(2)Ru(mu-1)Ru(bpy)(2)](4+) (Ru2; bpy = 2,2'-bipyridine) and [[(bpy)(2)Ru(mu-2,3-dpp)](2)Ru(mu-1)Ru[(mu-2,3-dpp)Ru(bpy)(2)](2)](12+) (Ru6; 2,3-dpp = 2,3-bis(2-pyridyl)pyrazine). The absorption spectra and luminescence properties of 1 and [Zn(1)](2+) are dominated by pi --> pi transitions and excited states. The absorption spectra of the ruthenium compounds are dominated by ligand-centered (LC) bands in the UV region and metal-to-ligand charge-transfer (MLCT) bands in the visible. The latter compounds undergo several reversible metal-centered oxidations and ligand-centered reductions in the potential window investigated (-2.0/+2.0 V versus SCE) and exhibit MLCT luminescence in both acetonitrile fluid solution at room temperature and in butyronitrile rigid matrix at 77 K. Both the redox and photophysical properties of Ru2 and Ru6 can be assigned to specific subunits of the multicomponent structures. The data indicate that the [Ru(bpy)(2)](2+) and the dendritic [Ru[(mu-2,3-dpp)Ru(bpy)(2)](2)](6+) fragments appended to the polytopic 1ligands behave as independent components of the multicomponent arrays.