Miniature Arcs for Synthesis of Carbon Nanotubes in Microgravity

Although many methods are available for producing single-walled carbon nanotubes (SWNTs), the conventional carbon arc process remains the most popular due to its simplicity and large production rate. In the carbon arc, SWNTs are catalytically synthesized by rapidly evaporating a graphite anode impregnated with NiN metal catalyst from which the nanotubes grow in an inert atmosphere. However, high temperatures inside the carbon arc generate strong buoyancy driven convection, and it is hypothesized that the non-uniform environment created by this flow has a large effect on the growth and morphology of the SWNTs. To study the effect of buoyancy on the arc process, a miniature carbon arc apparatus was developed to synthesize SWNTs in a microgravity environment substantially free from these strong convective flows. The reactor was operated for either 2.2 or 5 seconds during free-fall in the drop towers at the NASA Glenn Research Center. Two apparatus designs differing mainly in their production rate and power capacity were investigated. The first consisted of a miniaturized carbon arc employing a 1 mm diameter graphite anode and powered by a 0.54 F capacitor bank charged to 65 V. The second, larger apparatus employed a 4 mm diameter anode and was powered by a portable battery pack capable of providing in excess of 300 amps at 30 volts to the arc for the duration of a 5 second drop. Initial results indicated that transient heating is a very large effect in the short-duration drop tower carbon arcs, and thermal equilibrium of the arc plasma, buffer gas, and apparatus was not attained during the short microgravity periods. In addition, removal of the buoyant convection by the microgravity now allowed clear observation of large jets of evaporated carbon vapor streaming from the anode and mixing with the inert buffer gas. The initial mixing of these jets with the cold buffer gas combined with the thermal transient made it difficult to establish a uniform high temperature environment around the arc in the 2.1 to 5 second microgravity time interval, and even with a very high-powered arc, the arc region was cooler than in continuously operated arcs. Despite these difficulties, the miniature arc produced SWNTs in microgravity. However, given the large thermal transient to overcome, no dramatic difference in sample yield or composition was noted between normal gravity and q2-,andL%econd long microgravity runs

САХАРНЫЙ ДИАБЕТ И ТРОМБОЭМБОЛИЯ ЛЕГОЧНОЙ АРТЕРИИ

Purpose. The aim of the study is to analyze characteristics and the clinical course of pulmonary embolism in patients with diabetes on the basis of the Pulmonary Embolism Register (PE) of deaths inTomskhospitals between 2003 and 2011.Materials and methods. We studied the autopsy reports and medical records of all patients (712 cases) diagnosed with pulmonary embolism anteand/or postmortem, died between 2003 and 2010. Diabetes mellitus was diagnosed in 141 patients and all of them had moderately severe course of the disease or were sub-or decompensated. 28.57% had a high body mass as well: 31,59 + 8,36 kg/m2 . The ratio of medical to surgical patients was 2.1 : 1.Results. All patients with diabetes were hospitalized on an emergency basis. 31 patients (21,6 %) stayed in hospital less than a day, so blood clots – the sources of thromboembolism, were formed at home, outside of hospital. The major source of thromboembolism was inferior vena cava branches. At the same time, 31,4 % diabetic patients had thrombi in the right chambers of the heart. Anticoagulants were used in 16,4 % of cases to prevent thromboembolism.Conclusion. The importance of type 2 diabetes mellitus as a risk factor for thromboembolic complications has been until now underestimated both at the outpatient and hospital stages. Цель. По данным госпитального Регистра тромбоэмболии легочной артерии (ТЭЛА) проанализировать варианты ее течения у пациентов с сахарным диабетом.Материалы и методы. Изучены протоколы вскрытий и историй болезни пациентов (712 случаев) с диагностированной прижизненно и/или посмертно ТЭЛА среди умерших в стационарах Томска. Сахарный диабет выявлен у 141 больного и у всех имел среднетяжелое или тяжелое течение, находился в стадии субили декомпенсации, у 28,57 % сопровождался повышенной массой тела. Соотношение «терапевтических» и «хирургических» пациентов составило 2,2 : 1.Результаты. Все пациенты с диабетом госпитализировались в экстренном порядке; 31 пациент (21,6 %) находился в стационаре менее суток, т. е. тромбообразование в местах – источниках тромбоэмболии у них происходило в домашних условиях вне стационара. Ведущим источником тромбоэмболии были ветви нижней полой вены, в том числе вены культи нижней конечности. В 31,4 % местом первичного тромбообразования у пациентов с сахарным диабетом были правые камеры сердца. Профилактические мероприятия в отношении ТЭЛА в виде применения антикоагулянтов использовались в 16,4 % случаев.Заключение. Значимость сахарного диабета 2-го типа как фактора риска развития тромбоэмболических осложнений до настоящего времени недооценивается как на амбулаторном, так и госпитальном этапе.

Electronic structure of hydrogenated carbon nanotubes studied bycore level spectroscopy

The high resolution near edge X ray absorption fine structure spectroscopy and X ray photoelectron spectroscopy were used to elucidate the nature of chemical bonding between carbon and hydrogen atoms on the surface and inside hydrogenated single walled carbon nanotubes H SWNTs . The measured spectra showed formation of chemical bonding between the hydrogen and carbon atoms in H SWNTs.In order to obtain a detailed understanding origin of the chemical bond between C and H atoms, density functional calculations and theoretical analysis of experimental NEXAFS spectra were carried ou

Hydrogenated carbon nanotubes x ray absorption spectroscopy and ab initio simulation analysis

The paper presents the results of investigation of the chemical bond formation in hydrogenated single walled carbon nanotubes using X ray absorption spectroscopy. All measurements were performed with the use of synchrotron radiation at BESSY II. The C1s absorption spectra point to formation of covalent chemical bonding between the hydrogen and carbon atoms in H SWNTs. The investigation of the H SWNT local structure has been carried out on the basis of the semi empirical PM6 method MOPAC 2009 and Finite Difference method. The possibility of H SWNTs dehydrogenation was also investigate

Risk factors of incident in-hospital pulmonary embolism and its outcomes: autopsy study data

Aim. Based on the autopsy data, to investigate the role of various risk factors (RFs) in the development of the incident cases of pulmonary thromboembolism (PTE) and their outcomes among the patients who died in Tomsk City hospitals (2003-2010). Material and methods. The analysed data came from autopsy protocols and medical histories of all patients (n=651) who had PTE diagnosed prior to or after death and who died in Tomsk hospitals between March 1st 2003 and December 31st 2010. The pathologoanatomical examination used the total evisceration technique by Shor. Data analysis was performed with the Pentium-V software package “Statistica for Windows”. The impact of RFs and treatment on the PTE outcome was assessed in a statistical model. Results. The presence of two or three RFs was associated with a higher risk of fatal in-hospital PTE. Overall, the risk of fatal PTE was explained by RF patterns (56,0%), inadequate treatment (43,9%), and other factors (0,1%). Conclusion. The identified features of the impact of RFs and medical treatment on the PTE outcome in Tomsk hospitals (2003-2010) should be taken into consideration when planning the strategy of improving the effectiveness of diagnostics, prevention, and treatment programmes