Stability of the Tomonaga-Luttinger liquid state in gamma-irradiated carbon nanotube bundles.

We report experimental results for the changes in conductivity of single-wall carbon nanotube bundles when irradiated by (60)Co γ-rays in various environments. In the current study the samples investigated were irradiated in hermetic cells, either evacuated (0.1 Pa) or filled with hydrogen or deuterium at atmospheric pressure. In situ measurements of the resistance change as a function of irradiation dose at room temperature are presented. It was found that, for all irradiation conditions, the normalized resistance versus irradiation dose demonstrates a logarithmic behaviour. A phenomenological model for the observed dependence is derived. The current-voltage characteristics of the irradiated samples were measured in the temperature range from 4.5 to 300 K using short (10 ns) electric pulses, and the results demonstrate a scaling behaviour. This scaling occurs in the universal coordinates that correspond to the Tomonaga-Luttinger liquid concept. Our results confirm the existence of the Tomonaga-Luttinger liquid phase up to room temperature in carbon nanotubes after γ-irradiation to a dose of 5 × 10(7) rad in vacuum, 1.7 × 10(7) rad in hydrogen and 1.24 × 10(8) rad in deuterium.

Effect of rare-earth component of the RE/Ni catalyst on the formation and nanostructure of single-walled carbon nanotubes.

A systematic experimental study has been carried out on the efficiency of bimetallic catalysts based on Ni and the rare-earth elements Y, La, Ce, Nd, Gd, Tb, Dy, Ho, Er, and Lu (group A) and Eu, Sm, Yb, and Tm (group B) in the synthesis of single-walled carbon nanotubes (SWNTs). The two groups give quite different results when analyzed by a combination of SEM/TEM and Raman and UV-NIR spectroscopies. The elements in group A have an obvious catalytic effect and increase the yield of SWNTs dramatically, whereas those in group B are not efficient catalysts. The diameter distribution of the synthesized SWNTs was also affected by the rare-earth element used. For group A metals, there is a tendency that the fraction of small-diameter tubes decreases with decreasing ionic radius of the rare-earth element used. EDX and X-ray analyses indicate that group A metals deposit on the cathode deposits and form rare-earth carbides, whereas no group B metals are found in cathode deposits, except for a small amount of Tm present in the form of thulium carbide. Further analysis indicates that there is a very strong correlation between the ability to form rare-earth carbides and the catalytic efficiency for the formation of SWNTs.

Magnetic carbon.

The discovery of nanostructured forms of molecular carbon has led to renewed interest in the varied properties of this element. Both graphite and C60 can be electron-doped by alkali metals to become superconducting; transition temperatures of up to 52 K have been attained by field-induced hole-doping of C60 (ref. 2). Recent experiments and theoretical studies have suggested that electronic instabilities in pure graphite may give rise to superconducting and ferromagnetic properties, even at room temperature. Here we report the serendipitous discovery of strong magnetic signals in rhombohedral C60. Our intention was to search for superconductivity in polymerized C60; however, it appears that our high-pressure, high-temperature polymerization process results in a magnetically ordered state. The material exhibits features typical of ferromagnets: saturation magnetization, large hysteresis and attachment to a magnet at room temperature. The temperature dependences of the saturation and remanent magnetization indicate a Curie temperature near 500 K.

Topochemical polymerization of C70 controlled by monomer crystal packing.

Polymeric forms of C60 are now well known, but numerous attempts to obtain C70 in a polymeric state have yielded only dimers. Polymeric C70 has now been synthesized by treatment of hexagonally packed C70 single crystals under moderate hydrostatic pressure (2 gigapascals) at elevated temperature (300 degrees C), which confirms predictions from our modeling of polymeric structures of C70. Single-crystal x-ray diffraction shows that the molecules are bridged into polymeric zigzag chains that extend along the c axis of the parent structure. Solid-state nuclear magnetic resonance and Raman data provide evidence for covalent chemical bonding between the C70 cages.

Individual prediction of treatment outcome in patients with temporomandibular disorders.

Out of 3159 patients referred to a specialist clinic of stomatognathic physiology, 1297 patients started treatment because of temporomandibular disorders. All those patients were divided into subgroups of patients with mainly muscular or TMJ symptoms, respectively. A prediction of the treatment outcome as good or dubious was also made. This prediction was based on the patient's history and the clinical findings. A total of 989 patients (76%) completed the treatment. They all graded the degree of improvement of their initial symptoms using a Numeric Rating Scale. An improvement of initial complaints of 50% or more was judged to be a relevant change. In 85% of the patients with mainly muscular symptoms, the treatment was predicted to have a good outcome. The corresponding figures for those patients with mainly TMJ symptoms were 93%. Not less than 88% of all the patients reported an improvement of 50% or more of their initial complaints. The possibility to predict the treatment outcome as good in patients with mainly muscular symptoms was very good: 90% fulfilled the criteria of a positive treatment result. For those with a dubious prognosis, 56% had a positive outcome of treatment. The possibility to predict treatment outcome as good in those with mainly TMJ symptoms was also very good: 94% responded positively on the treatment. Almost the same figure, 88%, of those with a poor prognosis had a positive treatment outcome.

Clinical evaluation of ceramic veneered titanium restorations according to the Procera technique.

The aim of the present study was to present the design and one-year results of a study of crowns and fixed partial dentures (FPDs) made with the Procera system. All patients at one clinic needing fixed prosthodontic restorations during a two-year period were invited. All 260 patients accepted to participate and they received 333 ceramic veneered Procera restorations-242 single crowns and 91 FPDs. The loss of patients during the one-year follow-up was only 5%. The restorations were evaluated according to a modified version of the California Dental Association rating system. Practically all Procera restorations were judged as satisfactory both at base line and at the one-year follow-up examination. Two crowns and one FPD showed fractures of the ceramic veneering. Another FPD had a fracture of a welded joint. Three single crowns came loose but could be recemented. In conclusion, the ceramic veneered Procera titanium restorations were well accepted by the patients and the success rate was high during the one-year follow-up period.

Enhancement of the molecular ion yield in plasma desorption mass spectrometry using explosive matrices.

The working hypothesis of this study was that the chemical energy of matrix material may be released, although only on a microscale, under MeV ion bombardment and may assist ejection of large intact bioorganic molecules. To test the hypothesis, the performance of several common explosives, as matrices in plasma desorption mass spectrometry, was compared to the standard matrix, nitrocellulose (NC), which is also a high explosive. Two explosives, RDX and HMX, were found to be new, effective matrices for peptides and proteins. While the performance of RDX was comparable with that of nitrocellulose, HMX gave a superior molecular ion yield and a higher average charge state of desorbed molecular ions compared with NC. Noth RDX and HMX have a similar chemical composition and structure, although the latter is a more powerful explosive. The measured total ion yield allows the conclusion that the increase in the amount of ejected material, due to the chemical energy release in high explosives under MeV ion bombardment, is limited, perhaps to a factor of 2 to 3. The fact that not all tested explosives gave molecular ions from peptides and proteins suggests that other factors, such as gas-phase chemistry, may play a significant role in molecular ion formation.

Imaging of single antigens, antibodies, and specific immunocomplex formation by scanning force microscopy.

The most sensitive analytical techniques available today for detecting immuno assay complexes are radio or enzyme immuno analytical techniques, by which quantities of 10(7)-10(8) analyte molecules can be detected. With the introduction of scanning force microscopy, a new method for detecting biological processes became available. Here, we examine the feasibility of using scanning force microscopy as a biosensitive tool. We demonstrate that single or multiple rabbit anti-human serum albumin molecules form complexes with preadsorbed single human serum albumin molecules on mica. However, no interaction is observed between human immunoglobulin G molecules and preadsorbed single albumin molecules; only separate antigens and antibodies are observed at random positions on the mica. This shows the ability of scanning force microscopy to act as a biosensor for detection of immunocomplexes, and to act as a very powerful tool to study molecule-surface interactions in general.

Peptide sequencing by partial acid hydrolysis and high resolution plasma desorption mass spectrometry.

A method of deriving peptide sequence information using partial acid hydrolysis in combination with accurate mass measurements and immonium ion analysis provided by high-resolution plasma desorption mass spectrometry has been developed. The technique is very simple in terms of the chemistry and involves a short-time (3-30 min) incubation of the peptide in 1N-6N HCl at 100-110 degrees C with subsequent mass spectrometric analysis. Partial acid hydrolysis is found to produce sequence-specific segments, often ladder-like, although not always a complete set. Two application examples of the method are given: the linear peptide bradykinin and desmopressin, a peptide with an internal S-S bond and a non-amino-acid constituent. The technique has proved to be particularly useful in cases where some a priori information on the peptide structure was already known or where the automated Edman degradation technique might yield erratic results or not work at all.