Establishment and characterization of a fish-cell line from the brain of Japanese flounder Paralichthys olivaceus.

A new brain-cell line derived from Japanese flounder Paralichthys olivaceus (POBC) was established. POBC was subcultured for 67 passages over the course of 420 days. The cultured cells were primarily epithelioid-like. Chromosome analysis revealed the cell line to possess the normal P. olivaceus diploid karyotype of 2n = 48t (telocentric chromosomes). The cells exhibited the astrocyte marker glial fibrillary acidic protein by immunocytochemistry, and significant fluorescent signals were observed when the cells were transfected with green fluorescent protein reporter plasmid. The established POBC would be ideal material for the study of function of fish ependyma, the central neuroendocrine system and endocrine disruptors in the marine environment.

Quantitative fitting of nonlinear current-voltage curves and parameter retrieval of semiconducting nanowire, nanotube and nanoribbon devices.

A quantitative metal-semiconductor-metal (MSM) model and a Matlab based program have been developed and used to obtain parameters that are important for characterizing semiconductor nanowires (NWs), nanotubes (NTs) or nanoribbons (NRs). The use of the MSM model for quantitative analysis of nonlinear current-voltage curves of one-dimensional semiconducting nanostructures is illustrated by working through two examples, i.e., an amorphous carbon NT and a ZnO NW, and the obtained parameters include the carrier density, mobility, resistance of the NT(NW), and the heights of the two Schottky barriers formed at the interfaces between metal electrodes and semiconducting NT(NW).

Quantitative analysis of defects and domain boundaries in mesoporous SBA-16 films.

Some quantitative structural analyses on defects and domain boundaries observed in SBA-16 films were performed using the lattice concept and geometric phase method. These analyses show that there exist low angle, high angle and translational anti-phase domain boundaries in SBA-16 films. While some of the domain boundaries bear analogue to those found in normal solid crystals, others are similar to that found in the liquid crystals. In particular near Sigma11 and Sigma13b high angle boundaries were observed. On the one hand the Sigma11 boundaries were found to exist with or without steps (ledge) associated with them depending on whether or not the boundary plane is parallel to the densely packed lattice plane. On the other hand segments of the boundary plane in the Sigma13b boundary were found being always associated with densely packed lattice plane, with the {011} type of lattice plane in one domain being parallel to the {112} type of plane in the other domain. The translational domain boundary was observed to have a translation vector having a projected component of (1/2) <110> on the (111) plane. The bending deformation similar to that found in the nematics liquid crystal was also observed and quantitatively analyzed using the geometric phase method, and rotational field associated with the deformation was identified.

A comparative study on SWCNT and DWCNT field-effect transistors.

Field-effect transistors have been fabricated using single-walled carbon nanotubes (SWCNTs) and double-walled carbon nanotubes (DWCNTs), and their electrical transport properties have been studied comparatively. While a semiconducting SWCNT exhibits better field-effect characteristics than a DWCNT counterpart, the DWCNT shows more complicated response to external gate modulation. Depending on the nature of the two shells of a DWCNT, i.e., whether the shell is semiconducting (S) or metallic (M), a DWCNT device can be described as either S-S, or S-M, or M-S, or M-M. It was found that the S-S and M-M or M-S devices show similar field-effect characteristics to those found in SWCNT devices. But for S-M DWCNT devices, distinct field-effect characteristic was found and attributed to the combined effects of intershell interactions and screening by free carriers of the inner metallic shell. The S-M DWCNT devices thus provide a perfect system for studying the important intershell interaction, and information on the effect of this interaction on the electrical properties of a multi-walled carbon nanotube can be obtained by a comparative study of S-M DWCNT and S-SWCNT devices.

High-quality ultralong Sb2Se3 and Sb2S3 nanoribbons on a large scale via a simple chemical route.

Large-scale ultralong single-crystalline Sb2Se3 and Sb2S3 nanoribbons were prepared respectively by reacting SbCl3 with selenium and sulfur powders in glycol solution. Both Sb2Se3 and Sb2S3 nanoribbons are usually hundreds of microns in length, and the structures of the nanoribbons are determined to be of the orthorhombic phases. The Sb2Se3 nanoribbons are typically 100-300 nm in width and 20-60 nm in thickness and grow along the [12] direction. Sb2S3 nanoribbons are wider than Sb2Se3 nanoribbons; Sb2S3 nanoribbons are about 200-500 nm in width and grow along the [001] direction. The growth mechanism of the nanoribbons is investigated based on high-resolution transmission electron microscopy (HRTEM) observations. Optical absorption experiment reveals that Sb2Se3 and Sb2S3 nanoribbons are two semiconductors with bandwidth Eg approximately 1.15 eV and Eg approximately 1.56 eV, respectively.

In situ fabrication and graphitization of amorphous carbon nanowires and their electrical properties.

Individual amorphous carbon nanowires (a-CNWs) were fabricated inside a transmission electron microscope (TEM) by the electron beam induced deposition (EBID) method, and the a-CNWs were graphitized in situ by introducing Fe particles into these a-CNWs and controlled movement of the Fe particles in these CNWs. Detailed structural characterizations and electrical measurements were carried out, and it was found that the current-induced movement of Fe particles has significant effects in purifying the as-fabricated a-CNW, transforming the a-CNW into a graphitized-CNW (g-CNW). Two-terminal current voltage characteristics measurements showed that the g-CNW has a very good electrical conductivity with a resistivity of about 5.3 x 10(-4) Omega cm, a current carrying capacity of at least 4.35 mA, and a current density of 4.6 x 10(8) A/cm(2), and these values are comparable to those of multiwalled carbon nanotubes. Field emission characteristics of both a-CNWs and g-CNWs were also measured, and their respective Fowler-Nordheim plots were found to have basically a linear form.

Synthesis and characterizations of amorphous carbon nanotubes by pyrolysis of ferrocene confined within AAM templates.

Amorphous carbon nanotubes (a-CNTs) are synthesized by pyrolysis of ferrocene confined in the nanopores of the anodic alumina membrane (AAM) and characterized by field emission scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), transmission electron microscopy (TEM), electron energy-loss spectroscopy (EELS), and Raman spectroscopy. It is shown that the a-CNT has an ultrathin amorphous wall (approximately 3 nm) and a relatively large diameter (approximately 50 nm), and is capsulated with iron oxide nanoparticles. It is found that the growth of the a-CNTs is governed mainly by the template limitation effect. Electrical transport measurements on individual a-CNTs demonstrate that the a-CNT may be connected with electrodes via either ohmic or Schottky contacts, and the resisitivity of the a-CNTs was measured to be 4.5 x 10(-3) Omega cm.

Quantitative analysis of electron field-emission characteristics of individual carbon nanotubes: the importance of the tip structure.

Electron field-emission measurements on individual carbon nanotubes (CNTs) were performed inside the transmission electron microscope (TEM). The field-emission characteristics of CNTs with different tip structures were compared, and their field conversion factor and emission area were studied systematically. It was found that the field-emission characteristics of a CNT depend sensitively on its tip structure, and in particular an opened CNT was shown to be superior to a capped CNT. High-resolution TEM observations revealed that the tip of an opened CNT may, in general, be regarded as being composed of irregular shaped graphitic sheets, and these graphitic sheets have been found to improve dramatically the field-emission characteristics, but the sharp edge may result in larger error in the calculated emission area. The influence of uncertainty in the work function of the CNTs on the field conversion factor and emission area calculation was also investigated.

Effect of H2 on the electrical transport properties of single Bi2S3 nanowires.

Field effect transistors have been fabricated using Bi2S3 nanowires. Whether the contact is ohmic or non-ohmic, the current of Bi2S3 nanowires was found to increase remarkably in H2 compared to that in a vacuum. Carrier density and mobility within the nanowires and the contact barriers between the nanowires and the electrodes have been extracted using field effect and two-probe current-voltage curves. It was found that H2 enhances electronic mobility and carrier density within the nanowires dramatically. The effect of H2 on the contact barriers was observed to be negligible compared to the other two effects.

Interface failure modes explain non-monotonic size-dependent mechanical properties in bioinspired nanolaminates.

Bioinspired discontinuous nanolaminate design becomes an efficient way to mitigate the strength-ductility tradeoff in brittle materials via arresting the crack at the interface followed by controllable interface failure. The analytical solution and numerical simulation based on the nonlinear shear-lag model indicates that propagation of the interface failure can be unstable or stable when the interfacial shear stress between laminae is uniform or highly localized, respectively. A dimensionless key parameter defined by the ratio of two characteristic lengths governs the transition between the two interface-failure modes, which can explain the non-monotonic size-dependent mechanical properties observed in various laminate composites.

High-quality ultralong Sb2S3 nanoribbons on large scale.

Large-scale, ultralong, single-crystalline Sb2S3 nanoribbons were prepared by directly reacting SbCl3 and Na2S2O3 solutions, without any organics used in the experiment. The nanoribbons were analyzed by a range of methods. The nanoribbons are usually several millimeters in length, typically 200-500 nm in width and 30-80 nm in thickness. The structure of the nanoribbons is determined to be of the orthorhombic phase. The growth mechanism of the nanoribbons was investigated based on high-resolution transmission electron microscopy observations. Optical absorption experiment shows that the nanoribbon is a semiconductor with a bandwidth Eg approximately 1.5 eV, near to the optimum for photovoltaic conversion, suggesting that Sb2S3 nanoribbons could be used in solar energy and photoelectronic applications.

Electron field emission characteristics and field evaporation of a single carbon nanotube.

Direct transmission electron microscope (TEM) observations of the field emission and evaporation process of emitting carbon nanotubes (CNTs) shown that the tip structure of the CNT is in general composed of irregular shaped graphitic sheets which extend typically more than 10 nm from the end of the CNT. It is found that the irregular shaped graphitic sheets at the tip of the CNT may greatly enhance the field emission characteristics of the CNT when compared with that having an ideal circular edge. The field evaporation of the CNT proceeds typically via the removal of the irregular shaped graphitic sheets from the tip of the CNT, and field emission characteristics of a CNT depend far more sensitively on the tip structure than on the geometric length of the CNT.

High-quality ultralong Bi2S3 nanowires: structure, growth, and properties.

A simple one-step hydrothermal method for large-scale synthesis of ultralong single-crystalline Bi2S3 nanowires was reported, and the nanowires were comprehensively characterized. The diameters of the nanowires are about 60 nm, and their lengths range from tens of microns to several millimeters. The structure of the nanowires was determined to be of the orthorhombic phase, the growth direction was along [001], and the growth mechanism was investigated based on extensive high-resolution transmission electron microscopy observations. Optical absorption experiments revealed that the Bi2S3 nanowires are narrow-band semiconductors with a band gap E(g) approximately 1.33 eV. Electrical transport measurements on individual nanowires gave a resistivity of about 1.2 ohms cm and an emission current of 3.5 microA at a bias field of 35 V/microm. This current corresponds to a current density of about 10(5) A/cm2, which makes the Bi2S3 nanowire a potential candidate for applications in field-emission electronic devices.

Field-effect characteristics and screening in double-walled carbon nanotube field-effect transistors.

Field-effect transistors (FETs) have been fabricated using double-walled carbon nanotubes (DWCNTs), and electrical transport measurements have been carried out on 125 DWCNT FETs. Among these devices, 52 were found to show basically semiconducting field-effect characteristics, 44 show metallic characteristics, and 29 show neither pure semiconducting nor metallic characteristics. These 3 distinct types of field-effect characteristics were identified as resulting from the semiconducting (S)-S, metallic (M)-M or M-S, and S-M combinations of the two shells of the DWCNT. While the S-S and M-M or M-S DWCNT devices exhibit similar field-effect characteristics to those by single-walled carbon nanotube (SWCNT) devices, the S-M device responds uniquely to the external gate voltage. In particular, it was found that free charges in the inner metallic shell may screen the outer semiconducting shell from the gate effect and that the screening is directly related to the intershell interaction, which increases with increasing temperature and tube diameter. The screening is disadvantageous to the performance of DWCNT FETs, and a similar effect is expected to occur in MWCNTs.

The use of monoclonal gene rearrangement for detection of minimal residual disease in acute lymphoblastic leukemia of childhood.

Sensitive quantification of minimal residual disease (MRD) using the polymerase chain reaction (PCR) is strongly predictive of outcome in childhood acute lymphoblastic leukemia (ALL), with MRD levels at the end of induction therapy of >10(-3) predicting a poor outcome. Methods for sensitive quantification are, however, complicated and time-consuming. Detection by PCR of monoclonal immunoglobulin heavy chain (IgH) and T cell receptor (TCR) gene rearrangements is simple and can be used in routine laboratories but is non-quantitative and of lower but uncertain sensitivity. The aim of this study was to determine the value of detection of monoclonality in identification of different levels of MRD. We looked for monoclonality in 64 bone marrow aspirates which had been obtained from 31 patients with B lineage ALL at various times during induction therapy and for which levels of MRD had been determined by limiting dilution analysis using patient-specific PCR primers. Detection of monoclonality identified levels of MRD of > or =10(-3) during induction with a sensitivity of 78% and a specificity of 93%. The positive and negative predictive values were 0.86 and 0.88, respectively. The sensitivity of detection of a monoclonal IgH rearrangement was greater than that for the TCRgamma locus during induction as an IgH rearrangement was detected more often than a TCRgamma rearrangement in patients who had both IgH and TCRgamma rearrangement at diagnosis. Detection of monoclonality is therefore a simple and quick test applicable to the majority of patients with ALL and it may be useful in identifying high-risk patients at the end of induction and in identifying relapsing patients later during therapy.

Comparison of methods for assessment of minimal residual disease in childhood B-lineage acute lymphoblastic leukemia.

The level of minimal residual disease (MRD) early in treatment of acute lymphoblastic leukemia (ALL) strongly predicts the risk of marrow relapse. As a variety of methods of varying complexity have been separately used for detecting and quantifying MRD, we compared the prognostic utility of three methods measurement of blast percentage on day 14 of treatment, detection of monoclonality on day 14 or day 35, and measurement of MRD by PCR-based limiting dilution analysis on day 14 or day 35. The study group comprised 38 children aged 1-15 with Philadelphia-negative B-lineage ALL who were uniformly treated and followed until relapse or for a minimum of 5 years. We also studied some of the technical factors which influence the ability to detect MRD. Measurement of blast percentage on day 14 by an expert morphologist, detection of monoclonality on day 35, and PCR-based measurement of MRD levels on days 14 and 35 all showed significant ability to divide patients into prognostic groups. Measurement of blast percentage on day 14 by routine morphology or detection of monoclonality on day 14 were not useful. The quality of DNA samples varied greatly, as determined by amplifiability in the PCR. However, virtually all amplifiable leukemic targets in a sample were detectable which suggests that the level of detection achieved by limiting dilution analysis is essentially determined by the amount of DNA which it is practicable to study. We conclude that quantification of MRD at the end of induction provides the full range of prognostic information for marrow relapse but is complex; detection of monoclonality on day 35 is simple and has good positive predictive value; and quantification of MRD on day 14 merits further study. PCR-based methods for measurement of MRD levels should incorporate a correction for variation in DNA amplifiability.

Effect of the Philadelphia chromosome on minimal residual disease in acute lymphoblastic leukemia.

The Philadelphia translocation is associated with a poor prognosis in adults and children with acute lymphoblastic leukemia, even though the majority of patients achieve remission. To test the hypothesis that the translocation leads to drug resistance in vivo, we studied 61 children and 20 adults with acute lymphoblastic leukemia and used the level of minimal residual disease at the end of induction as the measure of drug resistance in vivo. In children the presence of the translocation was associated with a significant increase in residual disease, indicating higher drug resistance in vivo; five of seven Philadelphia-positive children but only five of 54 Philadelphia-negative children had a minimal residual disease level >10(-3), a level which is associated with a high risk of relapse in childhood acute lymphoblastic leukemia of standard risk. By contrast, in adults, residual disease and hence drug resistance was already higher than in children, and the presence of the Philadelphia translocation in seven patients had no obvious additional effect. We conclude that the Philadelphia chromosome may increase resistance to drugs in vivo in children, but not detectably in adults.

Bloch wave treatment of symmetry and multiple beam cases in reflection high energy electron diffraction and reflection electron microscopy.

Bloch wave equations for the multiple beam cases in reflection high energy electron diffraction (RHEED) are derived from the integral equation by forward- and back-scattering Green function operators. A linearization is achieved through separation in a forward- and a back-scattering component for each beam. This leads to a set of fundamental equations similar to the transmission case, but with a non-Hermitian matrix, and the beams may be entered as either forward-, back-scattered, or both. The number of beams needed to be included in RHEED calculations is thus reduced, and so are the computing time and computer space required. The systematic row case, corresponding to reflections from planes parallel to the crystal surface, is treated in detail and illustrated by calculations of dispersion surfaces and rocking curves for Au(001). Symmetry relations for the systematic row and between reciprocal rows are discussed and illustrated.

Growth of compound single- and multi-walled carbon nanotubes.

Single-walled carbon nanotubes (SWCNTs) and multi-walled carbon nanotubes (MWCNTs) are complement to each other in many of their physical properties. We report the synthesis of carbon nanotube cables-a form of compound single- and multi-walled carbon nanotubes which could have the superior properties of both the SWCNTs and MWCNTs. This compound form of carbon nanotubes consists of a bundle of SWCNTs formed into a MWCNT, and the diameter of the inner most shell of the MWCNT ranges from a few to tens nanometers. The growth of these compound carbon nanotubes cannot be explained readily via existing modes of carbon nanotube growth, but promises a new way for improving and controlling the physical properties of either single- or multi-walled carbon nanotubes.

Performing probe experiments in the SEM.

A four nanoprobe system has been installed inside a FEI XL30 F scanning electron microscope (SEM), and shown to be fully compatible with the normal functions of the SEM and also a Gatan cold stage (model C1003, -185-400 degrees C). With some selected examples of applications, we have shown that this nanoprobe system may be used effectively for gripping, moving and manipulating nanoobjects, e.g. carbon nanotubes, setting up electric contacts for electronic measurements, tailoring the structure of the nanoobject by cutting, etc. and even for making unexpected nanostructures, e.g. a nanohook. Applications in other areas have also been speculated, limitations or disadvantages of the current design of the probe system were discussed, and methods for possible improvement were suggested.