Cell growth on 3D microstructured surfaces.

Chinese Hamster Ovary (CHO) cell cultures were grown on surfaces lithographed with periodic 3D hexagonal microcavity array morphology. The range of microcavity size (inscribed circle diameter) was from 12 µm to 560 µm. CHO cells were grown also on flat surfaces. The characterization was performed with respect to cell growth density (number of nuclei per unit area) by fluorescence optical microscopy and evaluated by correlation function analysis. We found that optimum microcavity radius was 80 µm, concerning to the maximum cell growth density, being even greater than the growth density on a flat (unstructured) substrate of the same material. This finding can be important for optimization of biotechnological processes and devices.

Gold ion implantation into alumina using an "inverted ion source" configuration.

We describe an approach to ion implantation in which the plasma and its electronics are held at ground potential and the ion beam is injected into a space held at high negative potential, allowing considerable savings both economically and technologically. We used an "inverted ion implanter" of this kind to carry out implantation of gold into alumina, with Au ion energy 40 keV and dose (3-9) × 10(16) cm(-2). Resistivity was measured in situ as a function of dose and compared with predictions of a model based on percolation theory, in which electron transport in the composite is explained by conduction through a random resistor network formed by Au nanoparticles. Excellent agreement is found between the experimental results and the theory.

Performance of an inverted ion source.

Whereas energetic ion beams are conventionally produced by extracting ions (say, positive ions) from a plasma that is held at high (positive) potential, with ion energy determined by the potential drop through which the ions fall in the beam formation electrode system, in the device described here the plasma and its electronics are held at ground potential and the ion beam is formed and injected energetically into a space maintained at high (negative) potential. We refer to this configuration as an "inverted ion source." This approach allows considerable savings both technologically and economically, rendering feasible some ion beam applications, in particular small-scale ion implantation, that might otherwise not be possible for many researchers and laboratories. We have developed a device of this kind utilizing a metal vapor vacuum arc plasma source, and explored its operation and beam characteristics over a range of parameter variation. The downstream beam current has been measured as a function of extraction voltage (5-35 kV), arc current (50-230 A), metal ion species (Ti, Nb, Au), and extractor grid spacing and beamlet aperture size (3, 4, and 5 mm). The downstream ion beam current as measured by a magnetically-suppressed Faraday cup was up to as high as 600 mA, and with parametric variation quite similar to that found for the more conventional metal vapor vacuum arc ion source.

Environmental effects in Kelvin force microscopy of modified diamond surfaces.

We have explored the effects of atmospheric environment on Kelvin force microscopy (KFM) measurements of potential difference between different regions of test polycrystalline diamond surfaces. The diamond films were deposited by microwave plasma-assisted chemical vapor deposition, which naturally produces hydrogen terminations on the surface of the films formed. Selected regions were patterned by electron-beam lithography and chemical terminations of oxygen or fluorine were created by exposure to an oxygen or fluorine plasma source. For KFM imaging, the samples were mounted in a hood with a constant flow of helium gas. Successive images were taken over a 5-h period showing the effect of the environment on KFM imaging. We conclude that the helium flow removes water molecules adsorbed on the surface of the samples, resulting in differences in surface potential between adjacent regions. The degree of water removal is different for surfaces with different terminations. The results highlight the importance of taking into account the atmospheric environment when carrying out KFM analysis.

Upgraded vacuum arc ion source for metal ion implantation.

Vacuum arc ion sources have been made and used by a large number of research groups around the world over the past twenty years. The first generation of vacuum arc ion sources (dubbed "Mevva," for metal vapor vacuum arc) was developed at Lawrence Berkeley National Laboratory in the 1980s. This paper considers the design, performance parameters, and some applications of a new modified version of this kind of source which we have called Mevva-V.Ru. The source produces broad beams of metal ions at an extraction voltage of up to 60 kV and a time-averaged ion beam current in the milliampere range. Here, we describe the Mevva-V.Ru vacuum arc ion source that we have developed at Tomsk and summarize its beam characteristics along with some of the applications to which we have put it. We also describe the source performance using compound cathodes.

High-energy metal ion implantation for reduction of surface resistivity of alumina ceramic.

In this work, the possibility to increase the surface conductivity of ceramic insulators through their treatment with accelerated metal ion beams produced by a MevvaV.Ru vacuum arc source is demonstrated. The increase in surface conductivity is made possible due to experimental conditions in which an insulated collector is charged by beam ions to a potential many times lower than the accelerating voltage, and hence, than the average beam ion energy. The observed effect of charge neutralization of the accelerated ion beam is presumably associated with electrons knocked out of the electrodes of the accelerating system of the source and of the walls of the vacuum chamber by the accelerated ions.

Prospective randomised trial of endobronchial ultrasound-guide sheath versus computed tomography-guided percutaneous core biopsies for peripheral lung lesions.

AIM: To determine diagnostic rate, complications and patient tolerability of endobronchial ultrasound-guide sheath (EBUS-GS) and computed tomography (CT)-guided percutaneous core biopsy for peripheral lung lesions. METHODS: Lesions >1 cm diameter on CT were randomised to either EBUS-GS or CT-guided biopsy. Excluded were patients with severe chronic obstructive airway disease, lesions touching visceral pleura or hilum, and patients with symptoms needing bronchoscopic evaluation. Patients completed preprocedure and postprocedure questionnaires on tolerability. RESULTS: Of 64 participants (mean lesion size 29 ± 16 mm), 57 completed the study. Diagnostic sensitivity was 67% for EBUS-GS and 78% for CT-guided biopsy (P = not significant). In those with negative results, in the EBUS group, nine had a CT-guided biopsy as a cross-over, seven of which were positive. In the CT group, four had cross-over EBUS-GS of which three were diagnostic. Sensitivity for malignancy was 17/23 for EBUS-GS (74%) and 23/26 (88%, P = not significant). For lesions <2 cm, CT-guided biopsy had a significantly better diagnostic yield (80% vs 50%, P = 0.05). In EBUS-GS cases, for lesions with an air bronchogram, sensitivity was 89%. Pneumothorax and intercostal catheter insertion occurred in three and two cases, respectively, for EBUS, and 10 and 3 cases for CT-guided biopsy (P = 0.02 for pneumothorax). Nine unexpected admissions occurred after CT-guided biopsy compared with three after EBUS-GS. Overall, tolerability was high for both groups; however three patients had moderate-to-severe pain after CT-guided biopsy. CONCLUSIONS: In lesions <2 cm, CT-guided biopsy had higher yields; however, EBUS-GS had better tolerability and fewer complications.

A high voltage pulse power supply for metal plasma immersion ion implantation and deposition.

We describe the design and implementation of a high voltage pulse power supply (pulser) that supports the operation of a repetitively pulsed filtered vacuum arc plasma deposition facility in plasma immersion ion implantation and deposition (Mepiiid) mode. Negative pulses (micropulses) of up to 20 kV in magnitude and 20 A peak current are provided in gated pulse packets (macropulses) over a broad range of possible pulse width and duty cycle. Application of the system consisting of filtered vacuum arc and high voltage pulser is demonstrated by forming diamond-like carbon (DLC) thin films with and without substrate bias provided by the pulser. Significantly enhanced film∕substrate adhesion is observed when the pulser is used to induce interface mixing between the DLC film and the underlying Si substrate.

The low-energy ion range in DNA.

In fundamental studies of low-energy ion irradiation effects on DNA, calculation of the low-energy ion range, an important basic physical parameter, is often necessary. However, up to now a unified model and approach for range calculation is still lacking, and reported data are quite divergent and thus unreliable. Here we describe an approach for calculation of the ion range, using a simplified mean-pseudoatom model of the DNA target. Based on ion stopping theory, for the case of low-energy (< or = a few keV) ion implantation into DNA, the stopping falls in the low reduced energy regime, which gives a cube-root energy dependence of the stopping (E(1/3)). Calculation formulas of the ion range in DNA are obtained and presented to unify the relevant calculations. The upper limits of the ion energy as a function of the atomic number of the bombarding ion species are proposed for the low-energy case to hold. Comparison of the results of this approach with the results of some widely used computer simulation codes and with results reported by other groups indicates that the approach described here provides convincing and dependable results.

Apneusis responding to buspirone in multiple sclerosis.

Apneusis is a disturbance of respiratory rhythm characterized by severely prolonged inspiratory effort, and is caused by bilateral lesions in the dorsal pons. In humans it is most commonly caused by pontine infarction and has rarely been reported in multiple sclerosis (MS). Here we report on a patient with MS who developed episodic apneusis which responded to treatment with buspirone, a serotonin type 1A receptor agonist.

Experimental comparison of time-of-flight mass analysis with magnetic mass analysis.

A series of experiments was carried out in which both a magnetic analyzer (mass separator) and a time-of-flight (TOF) spectrometer were used for ion charge/mass spectral analysis of the ion beam formed by a dc Bernas ion source made for semiconductor implantation. The TOF analyzer was a detachable device that provides rapid analysis of charge-to-mass composition of moderate energy ion beams. The magnetic analyzer was a massive device using a 90 degrees -sector bending magnet with radius of the central orbit of 35 cm. Comparison of these two methods for measuring ion beam composition shows good agreement.

Small plasma source for materials application.

We describe a small hollow-cathode plasma source suitable for small-scale materials synthesis and modification application. The supporting electrical system is minimal. The gaseous plasma source delivers a plasma ion current of up to about 1 mA. Here we outline the source construction and operation, and present some of its basic performance characteristics.

Atomic force microscope nanolithography of polymethylmethacrylate polymer.

We describe a nanolithography process for a polymethylmethacrylate (PMMA) surface using scanning contact atomic force microscopy. Parallel furrows were scribed with a pyramidal silicon tip using the same scan mechanism as used to image samples. The PMMA was first electron beam irradiated using a scanning electron microscope and developed. The topography formed is reproducible and predictable. Material from the region where the tip scribes is moved to nearby regions, and aligned, elongated PMMA fragments are seen to decorate the valleys between furrows.

Bioactive surface coatings for nanoscale instruments: effects on CNS neurons.

A method is described for depositing onto medical instruments highly biocompatible and bioactive surface coatings that can promote and stabilize cell attachment. The coatings were made by first depositing thin films of materials, such as diamond-like carbon, or metals, including tantalum, tungsten, platinum, gold, iridium, palladium, and brass. These surfaces were further altered to either promote or inhibit cell growth and spreading by an additional overcoat of biological materials, including the extracellular matrix proteins, laminin, fibronectin, and collagen IV. The deposition technique used a metal or carbon plasma, and the important properties of film adhesion, hardness, density, and smoothness are tailored by control of the ion bombardment energy. The films are translucent enough to permit high resolution light microscopy for rapid and detailed examination of tissue response. These bioactive substrates have been tested on primary central nervous system neurons, and the growth response is excellent. Equally successful have been our attempts to anchor neurons, without associated proliferation of non-neuronal cells, using coatings of poly-d-lysine. The method and the materials could have important ramifications in a number of areas of research and biotechnology, for example for chronic implantation of microelectrode arrays in the cerebral cortex for neuroprosthetic and neural monitoring application and for research on the human central nervous system. Possible application in nonneuronal fields, such as for coronary artery stents and pacemaker electrodes, also are discussed.

Pleurectomy for persistent pain in benign asbestos-related pleural disease.

BACKGROUND: Persistent severe pain is a rare complication of benign asbestos-related pleural disease. METHODS: Four patients are described in whom pain persisted for more than one year (range 18 months to five years) which was incompletely relieved by opioid medication and nerve blocking procedures. All underwent pleurectomy in an attempt to relieve it. RESULTS: At operation the pleura was considerably thickened in all cases. Two of the four patients had successful relief of pain. The other two had a neuralgic component to their pain before surgery which persisted afterwards. One of these patients underwent successful cervical cordotomy. CONCLUSIONS: Pleurectomy may provide relief in patients with constant pleuritic pain due to benign asbestos-related pleural thickening. It seems, however, that patients in whom the pain has a neuralgic component are unlikely to benefit.

Successful treatment of disseminated strongyloidiasis.

OBJECTIVE: To report the successful treatment of Strongyloides stercoralis hyperinfection, which is usually lethal but in this case was diagnosed in its early stages. CLINICAL FEATURES: A 44-year-old woman, who had spent much of her life in Fiji and India, was treated with a high dose of prednisolone for rheumatoid arthritis complicated by gold lung. The onset of abdominal symptoms, an exacerbation of respiratory symptoms, and a persistent high eosinophil count and serum IgE level, led to the detection of numerous Strongyloides larvae in her faeces and sputum. INTERVENTION AND OUTCOME: She was treated with thiabendazole for five days, then mebendazole for one month, and the dose of prednisolone was reduced. Clinical symptoms and signs improved within days and after one week parasites could not be found in her faeces. After six months, enzyme-linked immunosorbent assay for Strongyloides infection gave a reading which was 40% of the initial level but still in the positive range. CONCLUSION: Steroid therapy in individuals with chronic, subclinical strongyloidiasis predisposes to the insidious development of hyperinfection syndrome, which has a high mortality rate. If detected early, this complication can be treated effectively. It can be prevented by actively seeking Strongyloides infection, by faecal microscopy and culture techniques and by serological tests, in high-risk individuals, such as immigrants from endemic areas.

Improvement in upper airway function after weight loss in patients with obstructive sleep apnea.

Overweight patients with obstructive sleep apnea (OSA) are improved by weight reduction, although the underlying mechanisms are not clear. We tested the hypothesis that improvement in OSA after weight loss is associated with improvement in pharyngeal function. Consequently, we measured pharyngeal area at functional residual capacity (AFRC) and at residual volume (ARV), the percent change in pharyngeal area between FRC and RV (delta Aph%) defined as (AFRC - ARV)/AFRC x 100, and lung volume dependence of pharyngeal area (LVD) defined as the difference between AFRC and ARV normalized for the expiratory reserve volume (ERV)--in 12 overweight apneic patients before and after weight loss. We found that after a 26 +/- 18 kg weight loss, there was a significant reduction in the apnea/hypopnea index from 57 +/- 29 to 14 +/- 10 (p less than 0.0005) and increase in the lowest nocturnal oxygen saturation from 54 +/- 20% to 80 +/- 8% (p less than 0.001). This improvement was associated with a significant reduction in delta Aph% from 25 +/- 15% to 9 +/- 18% (p less than 0.05) and a significant decrease in LVD from 1.98 +/- 1.52 cm2/L to 0.16 +/- 0.88 cm2/L (p less than 0.005). There were four patients in whom baseline LVD was low and relatively unchanged after weight loss. Three of these patients exhibited paradoxical inspiratory narrowing of the glottis, which reversed after weight loss; these glottic abnormalities were not present in the rest of the patients with OSA. We conclude that improvement in obstructive sleep apnea after weight loss may be related to improvement in pharyngeal and glottic function.

Differences in pharyngeal properties between snorers with predominantly central sleep apnea and those without sleep apnea.

The underlying cause of idiopathic central sleep apnea syndrome is not well understood. We therefore examined the possibility that patients with idiopathic central sleep apnea may have abnormalities of upper airway mechanics that might contribute to the pathogenesis of central apneas. The acoustic reflection technique was used to assess pharyngeal size, lung volume dependence, and pharyngeal "compliance" in 8 patients with idiopathic central sleep apnea, all of whom were snorers, and in 8 weight-matched, snoring control subjects with normal sleep studies. Patients with central sleep apnea when compared with control subjects exhibited markedly increased specific pharyngeal "compliance" (0.12 +/- 0.05 versus 0.03 +/- 0.01 cm H2O-1; p less than 0.001), increased change in pharyngeal area from FRC to RV (0.8 +/- 0.5 versus 0.03 +/- 0.3 cm2; p less than 0.05), and a larger pharyngeal area at FRC (4.7 +/- 0.9 versus 3.8 +/- 0.8 cm2; p less than 0.03). We conclude that increased pharyngeal "compliance" and lung volume dependence may play a role in the etiology of central apneas in this syndrome.

Pharyngeal size in snorers, nonsnorers, and patients with obstructive sleep apnea.

We measured pharyngeal cross-sectional area and its change with alterations in lung volume in 10 subjects who snored and had obstructive sleep apnea, 6 subjects who snored and did not have obstructive sleep apnea, and 9 subjects who did not snore. Pharyngeal area was measured with use of an acoustic-reflection technique. We found that snorers with and without sleep apnea had a significantly smaller mean (+/- SE) pharyngeal cross-sectional area (4.1 +/- 0.2 and 3.7 +/- 0.9 cm2, respectively) at functional residual capacity than nonsnorers (5.4 +/- 0.5 cm2, P less than 0.025). When lung volume decreased from functional residual capacity to residual volume, both nonsnorers and snorers with sleep apnea had a decrease in pharyngeal area (from 5.4 +/- 0.5 to 4.5 +/- 0.4 cm2 and 4.1 +/- 0.2 to 3.4 +/- 0.2 cm2, respectively), whereas snorers without sleep apnea had no such decrease, suggesting that their pharynxes were less collapsible at low lung volumes. We conclude that snorers with and without sleep apnea have smaller pharyngeal cross-sectional areas than nonsnorers and that snorers with sleep apnea have a further decrease as lung volume falls.