Chemically active substitutional nitrogen impurity in carbon nanotubes

We investigate the nitrogen substitutional impurity in semiconducting zigzag and metallic armchair single-wall carbon nanotubes using ab initio density functional theory. At low concentrations (less than 1 atomic %), the defect state in a semiconducting tube becomes spatially localized and develops a flat energy level in the band gap. Such a localized state makes the impurity site chemically and electronically active. We find that if two neighboring tubes have their impurities facing one another, an intertube covalent bond forms. This finding opens an intriguing possibility for tunnel junctions, as well as the functionalization of suitably doped carbon nanotubes by selectively forming chemical bonds with ligands at the impurity site. If the intertube bond density is high enough, a highly packed bundle of interlinked single-wall nanotubes can form.Comment: 4 pages, 4 figures; major changes to the tex

Atomic Configuration of Nitrogen Doped Single-Walled Carbon Nanotubes

Having access to the chemical environment at the atomic level of a dopant in a nanostructure is crucial for the understanding of its properties. We have performed atomically-resolved electron energy-loss spectroscopy to detect individual nitrogen dopants in single-walled carbon nanotubes and compared with first principles calculations. We demonstrate that nitrogen doping occurs as single atoms in different bonding configurations: graphitic-like and pyrrolic-like substitutional nitrogen neighbouring local lattice distortion such as Stone-Thrower-Wales defects. The stability under the electron beam of these nanotubes has been studied in two extreme cases of nitrogen incorporation content and configuration. These findings provide key information for the applications of these nanostructures.Comment: 25 pages, 13 figure

Thermochemistry of Alane Complexes for Hydrogen Storage: A Theoretical and Experimental Comparison

Knowledge of the relative stabilities of alane (AlH3) complexes with electron donors is essential for identifying hydrogen storage materials for vehicular applications that can be regenerated by off-board methods; however, almost no thermodynamic data are available to make this assessment. To fill this gap, we employed the G4(MP2) method to determine heats of formation, entropies, and Gibbs free energies of formation for thirty-eight alane complexes with NH3-nRn (R = Me, Et; n = 0-3), pyridine, pyrazine, triethylenediamine (TEDA), quinuclidine, OH2-nRn (R = Me, Et; n = 0-2), dioxane, and tetrahydrofuran (THF). Monomer, bis, and selected dimer complex geometries were considered. Using these data, we computed the thermodynamics of the key formation and dehydrogenation reactions that would occur during hydrogen delivery and alane regeneration, from which trends in complex stability were identified. These predictions were tested by synthesizing six amine-alane complexes involving trimethylamine, triethylamine, dimethylethylamine, TEDA, quinuclidine, and hexamine, and obtaining upper limits of delta G for their formation from metallic aluminum. Combining these computational and experimental results, we establish a criterion for complex stability relevant to hydrogen storage that can be used to assess potential ligands prior to attempting synthesis of the alane complex. Based on this, we conclude that only a subset of the tertiary amine complexes considered and none of the ether complexes can be successfully formed by direct reaction with aluminum and regenerated in an alane-based hydrogen storage system.Comment: Accepted by the Journal of Physical Chemistry

Effect of Growth Temperature on Bamboo-shaped Carbon–Nitrogen (C–N) Nanotubes Synthesized Using Ferrocene Acetonitrile Precursor

This investigation deals with the effect of growth temperature on the microstructure, nitrogen content, and crystallinity of C–N nanotubes. The X-ray photoelectron spectroscopic (XPS) study reveals that the atomic percentage of nitrogen content in nanotubes decreases with an increase in growth temperature. Transmission electron microscopic investigations indicate that the bamboo compartment distance increases with an increase in growth temperature. The diameter of the nanotubes also increases with increasing growth temperature. Raman modes sharpen while the normalized intensity of the defect mode decreases almost linearly with increasing growth temperature. These changes are attributed to the reduction of defect concentration due to an increase in crystal planar domain sizes in graphite sheets with increasing temperature. Both XPS and Raman spectral observations indicate that the C–N nanotubes grown at lower temperatures possess higher degree of disorder and higher N incorporation

DNA fragmentation factors 40 and 45 (DFF40/DFF45) and B-cell lymphoma 2 (Bcl-2) protein are underexpressed in uterine leiomyosarcomas and may predict survival

Tomasz Banas,1 Kazimierz Pitynski,1 Krzysztof Okon,2 Aleksandra Czerw3,4 1Department of Gynecology and Oncology, 2Department of Pathomorphology, Jagiellonian University Medical College, Krakow, 3Department of Public Health, Faculty of Health Science, Medical University of Warsaw, 4Department of Health Promotion and Postgraduate Education, National Institute of Public Health – National Institute of Hygiene, Warsaw, Poland Objectives: DNA fragmentation factors 40 and 45 (DFF40 and DFF45) are responsible for final DNA-laddering during apoptosis, whereas Bcl-2 (B-cell lymphoma 2) is an apoptosis inhibitor. Our aim was to investigate the expression of DFF40, DFF45, and Bcl-2 in uterine leiomyosarcomas (uLMS), leiomyomas (uLM), and the normal myometrium. Furthermore, the correlation between DFF40, DFF45, and Bcl-2 expression and clinicopathological parameters in leiomyosarcomas was assessed. Their prognostic value in disease-free survival (DFS) and overall survival (OS) was also calculated.Materials and methods: This study included 53 cases of uLMS from patients matched for age and menopausal status with 53 cases of uLM and 53 controls of normal myometrium (uM). Case samples of uterine myometrium from leiomyosarcomas (uLMS-M) and leiomyomas (uLM-M) were also studied. Immunohistochemical scoring was undertaken for DFF40, DFF45, and Bcl-2.Results: DFF40, DFF45, and Bcl-2 were significantly underexpressed in uLMS compared with uLMS-M and uM. In uLMS samples, no correlation between the analyzed proteins was observed. Negative DFF40 and Bcl-2, but not DFF45, staining was a predictor of poorer DFS and OS in women with uLMS. uLM showed DFF40 and Bcl-2 overexpression compared with uM and uLM-M, with a significant positive correlation between DFF40 and DFF45. No differences in DFF40, DFF45, and Bcl-2 expression were observed between the uLMS-M, uLM-M, and uM samples, with a significant positive correlation between DFF40 and DFF45 expression.Conclusion: DFF40, DFF45, and Bcl-2 are significantly underexpressed in uLMS, but only a lack of DFF40 and Bcl-2 negatively influences DFS and OS. Disruption of DFF40 and DFF45 expression was observed in uLMS, but not in uLM or control and case myometrium; this may play a role in tumor pathogenesis. Keywords: B-cell lymphoma 2, disease-free survival, DNA fragmentation factor 40, DNA fragmentation factor 45, uterine, immunohistochemistry, leiomyosarcoma, uterine leiomyoma, overall surviva

Evaluation of volumetric parameters of the ventricular assist device using bioimpedance method

Volumetric parameters of operation of the pulsatile ventricular assist device (VAD) are the key clinical indicators for the evaluation of adequacy of the process of mechanical heart assistance and ensuring the patient's safety. The bioimpedance method has been proposed to evaluate blood volume changes of the VAD. The method is based on volume electric conductivity of the blood. A change in VAD volume involves changes in impedance. Periodic changes in VAD volume during its operation result in a pulsatile impedance wave; its amplitude in the subperiod of filling and ejection correlates with the volume of blood in the VAD. The paper presents the way of acquisition of the bioimpedance signal. It also presents the results of experimental studies, that were carried out with the use of the flow test stand, and an approach to analysing the bioimpedance signal to evaluate the stroke volume

Determination of stroke volume of the ventricular assist device using bioimpedance method

The stroke volume of pulsatile ventricular assist device (VAD) is one of the key clinical indicators to evaluate the adequacy of the process of mechanical heart assistance and ensuring the patient’s safety. In order to evaluate the volume changes in VAD blood chamber, a bioimpedance method was applied, based on volumetric electric conductivity of the blood. Periodic changes in VAD volume during its operation result in a pulsatile impedance waveform; its amplitude in the subperiods of filling and ejection correlates with blood volume in the chamber. The paper presents the method of analysis of the bioimpedance signal recorded in VAD blood chamber with a reference to the classical method of analysing the cardioimpedance signal from the patient’s thorax. The paper also presents the results of determining stroke volume of blood chamber based on an empirical formula that has been developed

Incidence and mortality rates in breast, corpus uteri, and ovarian cancers in Poland (1980–2013): an analysis of population-based data in relation to socio-economic changes

Tomasz Banas,1 Grzegorz Juszczyk,2 Kazimierz Pitynski,1 Dorota Nieweglowska,1 Artur Ludwin,1 Aleksandra Czerw2 1Department of Gynecology and Oncology, Jagiellonian University Medical College, Krakow, 2Faculty of Health Science, Medical University of Warsaw, Warsaw, Poland Objectives: This study aimed to analyze incidence and mortality trends in breast cancer (BC), corpus uteri cancer (CUC), and ovarian cancer (OC) in Poland in the context of sociodemographic changes.Materials and methods: Incidence and mortality data (1980–2013) were retrieved from the Polish National Cancer Registry, while socioeconomic data (1960–2013) were obtained from the World Bank. Age-standardized incidence and mortality rates were calculated by direct standardization, and join-point regression was performed to describe trends using the average annual percentage change (AAPC).Results: A significant decrease in birth and fertility rates and a large increase in gross domestic product were observed together with a decrease in the total mortality rate among women, as well as an increase in life expectancy for women. A large, significant increase in BC incidence was observed (AAPC1980–1990 2.14, AAPC1990–1996 4.71, AAPC1996–2013 2.21), with a small but significant decrease in mortality after a slight increase (AAPC1980–1994 0.52, AAPC1994–2013 −0.66). During the period 1980–2013, a significant increase in CUC incidence (AAPC1980–1994 3.7, AAPC1994–2013 1.93) was observed, with an initial mortality-rate reduction followed by a significant increase (AAPC1980–2006 −1.12, AAPC2006–2013 3.74). After the initial increase of both OC incidence and mortality from 1994, the incidence rate decreased significantly (AAPC1980–1994 2.98, AAPC1994–2013 −0.49), as did the mortality rate (AAPC1980–1994 0.52, AAPC1994–2013 −0.66).Conclusion: After 1994, a decrease in OC incidence was found, while the incidence of BC and CUC continued to increase. A reduction in mortality rate was observed for BC and OC predominantly at the end of the study period, while for CUC, after a long decreasing mortality trend, a significant increase was observed. Keywords: average annual percentage change, breast cancer, corpus uteri cancer, epidemiology, incidence, mortality, ovarian cance

Cost-utility of extracorporeal membrane oxygenation rewarming in accidentally hypothermic patients-A single-centre retrospective study.

Extracorporeal membrane oxygenation (ECMO) has become the treatment of choice for severely hypothermic patients in cardiac arrest or acute cardiac failure. Highly specialized ECMO centres have been established, however, no centre has ever reported the costs of extracorporeal rewarming. The aim of this study was to assess the costs of the treatment of patients in Swiss Stage III and IV rewarmed with veno-arterial ECMO. A retrospective exploratory cohort study analysed twenty-nine consecutive patients treated for hypothermia in the Severe Accidental Hypothermia Centre in Cracow, Poland. The main outcome parameters were the overall and specific costs of the ICU treatment of patients rewarmed with veno-arterial ECMO. The secondary outcome parameter was cost utility, determined by the costs involved for every year of life gained. Costs were processed using the bottom-up method and classified into six categories. Survivors were followed up after 1 year. The mean cost of VA-ECMO was $5133 USD, which equalled 35$14 668 USD). One year after discharge, 13 of 29 patients were still alive (45%). The overall gain of life of the thirteen 1-year survivors was 28 years, while the mean cost related to treatment with VA-ECMO for each year of life gained was 1138 USD. In this study, the costs of VA-ECMO rewarming and intensive care treatment per patient were substantially lower than in other studies reporting ECMO and intensive care treatment of other causes

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