Selective optical property modification of double-walled carbon nanotubes by fluorination

We found that by fluorination of double-walled carbon nanotubes (DWNTs), it is possible to suppress only the Raman radial breathing mode and absorption peaks from the outer (large diameter) tubes of DWNTs. In contrast, Raman signals from the inner shells showed no difference from the pristine DWNTs. The stability of the inner shells of fluorinated DWNTs was also confirmed from the photoluminescence (PL) map and the optical absorption spectra, which only showed the signals from the inner shells of DWNTs, with no distinct change in the optical properties of the inner tubes after fluorination. Our results indicate that once fluorinated, there exists only a weak, if not none, interaction between the inner tube and the outer fluorinated tube, proving that fluorination can be used to suppress the optical properties of carbon nanotubes without interfering the properties of inner tubes. The present finding can be important in electronic and sensor applications, keeping the inner tube from having unwanted contact with other substances that may distract from the inner tube's own characteristics.

Computational modeling of the thermal conductivity of single-walled carbon nanotube-polymer composites

A computational model was developed to study the thermal conductivity of single-walled carbon nanotube (SWNT)-polymer composites. A random walk simulation was used to model the effect of interfacial resistance on the heat flow in different orientations of SWNTs dispersed in the polymers. The simulation is a modification of a previous model taking into account the numerically determined thermal equilibrium factor between the SWNTs and the composite matrix material. The simulation results agreed well with reported experimental data for epoxy and polymethyl methacrylate (PMMA) composites. The effects of the SWNT orientation, weight fraction and thermal boundary resistance on the effective conductivity of composites were quantified. The present model is a useful tool for the prediction of the thermal conductivity within a wide range of volume fractions of the SWNTs, so long as the SWNTs are not in contact with each other. The developed model can be applied to other polymers and solid materials, possibly even metals.

Magnetic brightening of carbon nanotube photoluminescence through symmetry breaking

We report that symmetry breaking by a magnetic field can drastically increase the photoluminescence quantum yield of single-walled carbon nanotubes, by as much as a factor of 6, at low temperatures. To explain this we have developed a theoretical model based on field-dependent exciton band structure and the interplay of Coulomb interactions and the Aharonov-Bohm effect. This conclusively explains our data as the first experimental observation of dark excitons 5-10 meV below the bright excitons.

All-fiber pulsed lasers passively mode locked by transferable vertically aligned carbon nanotube film

An all-fiber passive laser mode locking is realized with a vertically aligned single-walled carbon nanotube film that can be transferred onto an arbitrary substrate using only hot water. A D-shaped fiber is employed as the substrate for the evanescent field interaction of propagating light with the nanotubes. The scheme highlights the efficient interaction achieved by the nanotube alignment as well as the dramatically simplified device preparation process. The demonstrated pulsed laser output has 2.9 nm of spectral full width at half-maximum and a 20.8 MHz repetition rate.

Serum immunoglobulins in patients with chronic hepatitis C: a surrogate marker of disease severity and treatment outcome

BACKGROUND/AIMS

Moderate polyclonal hypergammaglobulinemia is a common finding in chronic viral liver disease; however, its clinical significance has not been completely elucidated. We attempted to determine whether serum immunoglobulin levels were correlated with the disease severity and the treatment outcome in patients with chronic hepatitis C.

METHODOLOGY

In a total of 102 patients with chronic hepatitis C, we performed serum tests on immunoglobulins and determined the histology activity index (HAI) score by liver biopsy. In 97 patients, immunoglobulin levels were followed prior to and 6 months after interferon (IFN) therapy.

RESULTS

Serum gamma (y)-globulin and immunoglobulin (IgG) were well correlated with HAI score (both; p < 0.0001), grading score (both; p < 0.01), and staging score (both; p < 0.0001). Among the 97 patients who received 6 months of IFN monotherapy, 31, 29, and 37 patients were complete, transient and non-responders, respectively. In the three subgroups, a significant difference was found in histological HAI, grading, and staging scores (p < 0.01, p < 0.05 and p < 0.0001, respectively), and in serum levels of gamma-globulin and IgG (both; p < 0.0001). Following IFN treatment, serum gamma-globulin and IgG were significantly decreased in the complete responders (both; p < 0.0001). Furthermore, serum levels of gamma-globulin and IgG of 1.5 g/dL were useful for predicting the treatment outcome of IFN monotherapy.

CONCLUSIONS

The measurement of serum gamma-globulin and IgG is a valuable non-invasive tool for assessing the disease severity and treatment outcome in patients with chronic hepatitis C.

Third and fourth optical transitions in semiconducting carbon nanotubes

We have studied the optical transition energies of single-wall carbon nanotubes over broad diameter (0.7-2.3 nm) and energy (1.26-2.71 eV) ranges, using their radial breathing mode Raman spectra. We establish the diameter and chiral angle dependence of the poorly studied third and fourth optical transitions in semiconducting tubes. Comparative analysis between the higher lying transitions and the first and second transitions show two different diameter scalings. Quantum mechanical calculations explain the result showing strongly bound excitons in the first and second transitions and a delocalized electron wave function in the third transition.

Exciton localization of single-walled carbon nanotubes revealed by femtosecond excitation correlation spectroscopy

Photoluminescence (PL) dynamics in single-walled carbon nanotubes (SWNTs) has been studied by the femtosecond excitation correlation method with a 150 fs time resolution. The SWNT samples were synthesized by different methods and suspended in gelatin films or D2O solutions. The PL dynamics of SWNTs depends on the local environment surrounding the SWNTs rather than the synthesis methods. The very weak temperature dependence of tauPL and the environment-dependent tauPL reveal that the PL relaxation process is dominated by the interplay between free excitons and weakly localized excitons.

Etiology and prognostic significance of severe uremic pruritus in chronic hemodialysis patients

Although uremia is well known as the most common cause of pruritus, the mechanisms of pruritus in chronic hemodialysis patients remain unclear. The purpose was to characterize uremic pruritus in more detail and to investigate whether severe pruritus is a marker for poor prognosis. A total of 1773 adult hemodialysis patients were studied. A questionnaire was given to each patient to assess the intensity and frequency, as well as pruritus-related sleep disturbance. We analyzed the relationship between clinical and laboratory data and the severity of pruritus in hemodialysis patients and followed them for 24 months prospectively. In total, 453 patients had severe pruritus with a visual analogue scale (VAS) score more than or equal to 7.0. Among them, more than 70% complained of sleep disturbance, whereas the majority of patients with a VAS score of less than 7.0 had no sleep disturbance. Male gender, high levels of blood urea nitrogen, beta2-microglobulin (beta2MG), hypercalcemia, and hyperphosphatemia were identified as independent risk factors for the development of severe pruritus, whereas a low level of calcium and intact-parathyroid hormone were associated with reduced risk. During the follow-up, 171 (9.64%) patients died. The prognosis of patients with severe pruritus was significantly worse than the others. Moreover, severe pruritus was independently associated with death even after adjusting for other clinical factors including diabetes mellitus, age, beta2MG, and albumin. Severe uremic pruritus caused by multiple factors, not only affects the quality of life but may also be associated with poor outcome in chronic hemodialysis patients.

A rare case of recurrent alpha-fetoprotein-producing gastric cancer without re-elevation of serum AFP

We report an extremely rare case of recurrent alpha-fetoprotein (AFP)-producing gastric cancer without re-elevation of serum AFP. The patient was a 78-year-old woman with AFP-producing gastric cancer, a rare type of gastric adenocarcinoma. A Borrmann III gastric tumour was surgically resected and AFP-producing gastric cancer was diagnosed based on high levels of serum AFP (705.44 ng/ml) and immunohistochemical examination of the tumour. The serum AFP level decreased to the normal range after resection without any sign of recurrence by imaging, but the patient developed local recurrence of the cancer and died 13 months after surgery. No re-elevation of serum AFP levels was observed after recurrence. Although serum AFP levels are believed to be useful for follow-up in the post-operative period, the possibility that serum AFP levels do not always correlate with the extent of the cancer should be kept in mind.

Changes in the Fluorescence Spectrum of Individual Single-Wall Carbon Nanotubes Induced by Light-Assisted Oxidation with Hydroperoxide

Through fluorescence-spectrum measurements, we investigated the effects of light-assisted oxidation with H2O2 (LAOx) on single-wall carbon nanotubes (SWNTs) that were individually dispersed in an aqueous solution of surfactant. The intensities of the fluorescence spectra were decreased remarkably by the LAOx when the light's wavelength was 400-500 nm and a little when 600-700 nm. The spectrum intensity did not recover even when the pH was restored to an original value of 6.5. The spectra changed little when the LAOx wavelength was 500-600 nm or the light was not irradiated. In addition, the effect of LAOx on SWNTs was related to the diameters of SWNTs. We inferred that these phenomena reflected that H2O2 was dissociated by absorbing the fluorescence light emitted from optically excited SWNTs, which, in turn, accelerated the burning out of SWNTs.

Superconductivity in entirely end-bonded multiwalled carbon nanotubes

We report that entirely end-bonded multiwalled carbon nanotubes (MWNTs) can exhibit superconductivity with a transition temperature (T(c)) as high as 12 K, which is approximately 30 times greater than T(c) reported for ropes of single-walled nanotubes. We find that the emergence of this superconductivity is highly sensitive to the junction structures of the Au electrode/MWNTs. This reveals that only MWNTs with optimal numbers of electrically activated shells, which are realized by end bonding, can allow superconductivity due to intershell effects.

Optical anisotropy in single-walled carbon nanotubes

Optical anistropy at optical communication wavelength was observed in films of vertically aligned single-walled carbon nanotubes (SWNTs). We report the control of both the polarization state and transmission of incoming light at 1550 nm by azimuthal and axial tilting of SWNT film about its aligned axis. The experiments reveal that the polarization state of light is susceptible to the azimuthal angle of the aligned direction of a SWNT having semiconductor characteristics and the intensity of the output beam after SWNT film shows cosine function dependence on the axial tilting angle.

Polarization dependence of the optical absorption of single-walled carbon nanotubes

Anisotropic optical absorption properties of single-walled carbon nanotubes (SWNTs) are determined from a vertically aligned SWNT film for 0.5-6 eV. Absorption peaks at 4.5 and 5.25 eV are found to exhibit remarkable polarization dependence and have relevance to optical properties of graphite. A method for determining a nematic order parameter for an aligned SWNT film based on the collinear absorption peak at 4.5 eV is presented, followed by the determination of the optical absorption cross section.

Development of hypoxemia in alcoholic liver disease

The aim of this study was to investigate the arterial hypoxemia in Japanese patients with alcoholic liver disease (ALD) with regard to alcohol consumption and/or disease severity. Hypoxemia was observed in 78% patients with ALD and in all 46 patients with alcoholic liver cirrhosis (ALC) and 33 (56%) of 59 patients with noncirrhotic alcoholic liver disease (NCALD) (P < 0.0001). The partial pressure of oxygen (PaO2) was 71.1 +/- 5.2 mm Hg in ALC and 78.7 +/- 6.3 mm Hg in NCALD (P < 0.0001). The oxygen consumption in ALD was significantly higher than that in control subjects (P < 0.0001), and a high oxygen consumption was seen in 88% of the patients with ALD, in all 46 ALC patients, and in 46 (78%) of 59 NCALD patients (P < 0.01). Following abstinence from alcohol, the PaO2 and oxygen consumption significantly recovered after day 2 (P < 0.0001), whereas the prothrombin index did not change in either NCALD or ALC patients. Multivariate analysis showed that alcohol consumption and oxygen consumption were significant independent predictors of PaO2. In conclusion, the present findings suggest that increased oxygen consumption due to alcohol ingestion is principally responsible for the hypoxemia in ALD patients.