Sliding friction on ice.

We study the friction when rectangular blocks made from rubber, polyethylene, and silica glass are sliding on ice surfaces at different temperatures ranging from -40 to 0 °C, and sliding speeds ranging from 3 µm/s to 1 cm s-1. We consider a winter tire rubber compound both in the form of a compact block and as a foam with ∼10% void volume. We find that both rubber compounds exhibit a similar friction on ice for all studied temperatures. As in a previous study at low temperatures and low sliding speeds, we propose that an important contribution to the friction force is due to slip between the ice surface and ice fragments attached to the rubber surface. At temperatures around 0 °C (or for high enough sliding speeds), a thin pre-melted water film will occur at the rubber-ice interface, and the contribution to the friction from shearing the area of real contact is small. In this case, the dominant contribution to the friction force is due to viscoelastic deformations of the rubber by the ice asperities. The sliding friction for polyethylene (PE) and silica glass (SG) blocks on ice differs strongly from that of rubber. The friction coefficient for PE is ∼0.04-0.15 and is relatively weakly velocity dependent except close to the ice melting temperature where the friction coefficient increases toward low sliding speeds. Silica glass exhibits a similarly low friction as PE for T > -10 °C but very large friction coefficients (of order unity) at low temperatures. For both PE and SG, unless the ice track is very smooth, the friction force depends on the position x along the sliding track. This is due to bumps on the ice surface, which are sheared off by the elastically stiff PE and SG blocks, resulting in a plowing-type of contribution to the friction force. This results in friction coefficients, which locally can be very large ∼1, and visual inspection of the ice surface after the sliding acts show ice wear particles (white powder) in regions where ice bumps occur. Similar effects can be expected for rubber blocks below the rubber glass transition temperature, and the rubber is in the (elastically stiff) glassy state.

Rolling friction of elastomers: role of strain softening.

We study the temperature and velocity dependency of rolling friction. Steel and PMMA cylinders are rolled on sheets of nitrile butadiene rubber (NBR), with and without filler, and fluoroelastomer (FKM) with filler. Measurements of the rolling friction are performed for temperatures between -40 °C and 20 °C, and for velocities between 5 µm s-1 and 0.5 cm s-1. For the unfilled NBR, a smooth rolling friction master curve is obtained using the bulk viscoelastic frequency-temperature shift factor aT. For the filled rubber compounds, a small deviation from the bulk viscoelastic shift factor is observed at low temperatures. The experimental data are analyzed using an analytical theory of rolling friction. For the filled compounds, good agreement with theory is obtained when strain softening is included, which increases the rolling friction by a factor ∼2 for the filled FKM and ∼3 for the filled NBR compounds. For the unfilled NBR, the maximum of the rolling friction occurs at higher sliding speeds than predicted by the theory. We discuss the role of the adhesive (crack-opening) contribution to the rolling friction, and the role of frozen-in elastic deformations as the rubber is cooled down below the rubber glass transition temperature.

Rubber friction: The contribution from the area of real contact.

There are two contributions to the friction force when a rubber block is sliding on a hard and rough substrate surface, namely, a contribution Fad = τf A from the area of real contact A and a viscoelastic contribution Fvisc from the pulsating forces exerted by the substrate asperities on the rubber block. Here we present experimental results obtained at different sliding speeds and temperatures, and we show that the temperature dependency of the shear stress τf, for temperatures above the rubber glass transition temperature Tg, is weaker than that of the bulk viscoelastic modulus. The physical origin of τf for T > Tg is discussed, and we propose that its temperature dependency is determined by the rubber molecule segment mobility at the sliding interface, which is higher than in the bulk because of increased free-volume effect due to the short-wavelength surface roughness. This is consistent with the often observed reduction in the glass transition temperature in nanometer-thick surface layers of glassy polymers. For temperatures T < Tg, the shear stress τf is nearly velocity independent and of similar magnitude as observed for glassy polymers such as PMMA or polyethylene. In this case, the rubber undergoes plastic deformations in the asperity contact regions and the contact area is determined by the rubber penetration hardness. For this case, we propose that the frictional shear stress is due to slip at the interface between the rubber and a transfer film adsorbed on the concrete surface.

Visualization and automatic detection of defect distribution in GaN atomic structure from sampling Moiré phase.

Quantitative detection of defects in atomic structures is of great significance to evaluating product quality and exploring quality improvement process. In this study, a Fourier transform filtered sampling Moiré technique was proposed to visualize and detect defects in atomic arrays in a large field of view. Defect distributions, defect numbers and defect densities could be visually and quantitatively determined from a single atomic structure image at low cost. The effectiveness of the proposed technique was verified from numerical simulations. As an application, the dislocation distributions in a GaN/AlGaN atomic structure in two directions were magnified and displayed in Moiré phase maps, and defect locations and densities were detected automatically. The proposed technique is able to provide valuable references to material scientists and engineers by checking the effect of various treatments for defect reduction.

Clinical potential of diagnostic methods for the rapid diagnosis of Mycoplasma pneumoniae pneumonia in adults.

The purpose of the present study was to evaluate the accuracy and usefulness of three rapid diagnostic methods, ImmunoCard Mycoplasma kit, chest high-resolution computed tomography (HRCT) findings, and the Japanese Respiratory Society (JRS) scoring system (including six parameters), for the early presumptive diagnosis of Mycoplasma pneumoniae pneumonia in adults. We performed three rapid diagnostic methods at the same time in four pneumonia groups: 68 cases with M. pneumoniae pneumonia, 133 cases with Streptococcus pneumoniae pneumonia, 30 cases with Haemophilus influenzae pneumonia, and 20 cases with Legionella pneumonia. The sensitivity and specificity were 35% and 68% for ImmunoCard, 73% and 85% with HRCT, and 83% and 90% with the JRS scoring system, respectively. Among the three rapid diagnostic methods, the JRS scoring system was the most useful tool for initiating the administration of adequate antibiotic therapy for probable M. pneumoniae pneumonia. We suggest that M. pneumoniae pneumonia should be suspected when there is a correlation of more than five parameters in the JRS scoring system (99% specificity). If there is a correlation of three or four parameters in the JRS scoring system, chest computed tomography (CT) findings are helpful for the presumptive diagnosis of M. pneumoniae pneumonia.

Clinical evaluation of the QuantiFERON-TB Gold test in patients with non-tuberculous mycobacterial disease.

OBJECTIVE: To evaluate the clinical usefulness of the QuantiFERON TB-2G (QFT-2G) test in patients with non-tuberculous mycobacterial (NTM) disease without a previous history of tuberculosis (TB). METHODS: The study consisted of 214 patients with NTM disease who satisfied the diagnostic guidelines of the American Thoracic Society. RESULTS: The causative microorganism was Mycobacterium avium in 83 patients, M. intracellulare in 80, M. kansasii in 33, M. marinum in 12, M. szulgai in 3, M. abscessus in 2 and M. chelonei in 1. The positive response rate of QFT-2G test result was 2% in 163 patients with M. avium-intracellulare complex (MAIC) disease, 52% in 33 with M. kansasii disease, 58% in 12 with M. marinum disease, 33% in 3 with M. szulgai disease, 0% in two with M. abscessus disease and 0% in one with M. chelonei disease. The positivity of the QFT-2G test was 52% in patients with NTM disease, thought to be because NTM possesses common M. tuberculosis-specific antigens. CONCLUSIONS: Although QFT-2G may be a useful diagnostic method to differentiate TB from MAIC disease, there are several problems to be resolved before it can be used as a diagnostic method for NTM disease (M. kansasii disease), including the determination of the positive cut-off level for QFT-2G test.

Development and evaluation of a loop-mediated isothermal amplification method for the rapid detection of Chlamydophila pneumoniae.

We developed a loop-mediated isothermal amplification (LAMP) method to detect Chlamydophila pneumoniae infection. This assay exclusively amplified C. pneumoniae sequences and no cross-reactivity was observed for other Chlamydia species. The detection limit for this assay was found to be ten elementary bodies in 25 min, as observed in a real-time turbidimeter and electrophoretic analysis. The specificity of the LAMP reaction was confirmed by restriction endonuclease analysis, as well as direct sequencing of the amplified product. Among nasopharyngeal swab specimens from 120 patients with acute respiratory tract infections and 40 healthy individuals, the LAMP results showed 100% agreement with the results of real-time polymerase chain reaction (PCR) assays.

Indeterminate results of QuantiFERON TB-2G test performed in routine clinical practice.

The present authors assessed risk factors that can promote indeterminate results of QuantiFERON TB-2G (QFT-2G; Cellestis Ltd, Carnegie, Australia) tests. The subjects were 704 patients with suspected tuberculosis (TB) and latent TB infection between January 2005 and December 2007. The QFT-2G test and the tuberculin skin test (TST) were performed for all subjects. If the results of the QFT-2G test were indeterminate, the test was repeated within 1 month. In total, 72 (10.2%) patients showed indeterminate results on the QFT-2G test. Indeterminate results were due to positive control failure in 68 (88.9%) patients and negative control failure in four patients. The results of the TST were negative for 64 patients showing indeterminate results, the remaining eight patients showed a positive response to the TST. Indeterminate results were significantly associated with elderly and immunocompromised patients. Lymphocytopaenia and hypoalbuminaemia were significantly associated with indeterminate laboratory findings. When the QFT-2G test was repeated for all patients showing indeterminate results, 12 (16.7%) patients demonstrated determinate results on the subsequent test. Indeterminate results of the QuantiFERON TB-2G test under routine clinical practice are not infrequent. When scoring QuantiFERON TB-2G test results for elderly and immunocompromised patients, one must be careful because the possibility of obtaining determinate results may be low even if the test is repeated.

Clinical evaluation of QuantiFERON TB-2G test for immunocompromised patients.

The usefulness of the tuberculin skin test (TST) and the QuantiFERON TB-2G (QFT-TB) test were compared in immunocompromised patients. The subjects consisted of 252 immunocompromised patients who were clinically suspected of tuberculosis (TB) infection between April 2005 and December 2006. Regarding the underlying diseases, 74 subjects had malignant diseases, 72 were undergoing immunosuppressive treatment, 52 had diabetes mellitus, 50 had chronic renal failure and four had HIV infection. While the positive rate of the QFT-TB test for the diagnosis of TB infection (TB disease or latent TB infection) was 78.1%, that of TST for TB infection was 50.0%. The QFT-TB test was significantly better than TST. However, 32 (13%) patients had an indeterminate QFT-TB result. Indeterminate findings were significantly more frequent in patients receiving immunosuppressive treatment (28%), especially with lymphocytopaenia in the peripheral blood, than in those who had other underlying diseases. While TST-positive and QFT-TB test-negative results were recognised in immunocompromised patients with bacille Calmette-Guérin vaccination or nontuberculous mycobacterial disease, TST-negative and QFT-TB test-positive results were recognised in immunocompromised patients with a past history of TB infection. It was concluded that the QuantiFERON TB-2G test is a more useful diagnostic method for tuberculosis infection than tuberculin skin test for immunocompromised patients suspected of tuberculosis disease. However, because the results of the QuantiFERON TB-2G test show an indeterminate response for patients receiving immunosuppressive treatment, especially for those with lymphocytopaenia due to severe underlying diseases, care must be taken in the interpretation of the QuantiFERON TB-2G test for these patients.

Growth, reproduction, and lactation in somatic cell cloned cows with short telomeres.

We previously showed that telomere lengths of 10 somatic cell cloned cows were significantly shorter than normal. In this study, we investigated growth, reproduction, and lactation in these animals to determine if shortened telomeres have any effect on these characteristics. Six Holstein and 4 Jersey cloned cows, derived from oviduct cells, were reared under general group feeding. Body weights were recorded from birth to 48 mo of age. A number of reproductive characteristics were screened during the prepubertal, postpubertal, and postpartum periods. After parturition, milk yields were recorded daily and percentages of milk fat, proteins, and solids-not-fat were measured at monthly intervals. These data were used to estimate production of milk components over a 305-d period. Overall, the cloned heifers exceeded standard growth rates for each breed. The cows were inseminated at the first estrus after they reached 450 d of age, and delivered normal calves except for one stillbirth in the Holstein group. They were inseminated at postpartum estrus to provide second and third parturitions and, again, these pregnancies were normal. Gestational periods and birth weights of the calves were both within the normal range. The average total milk yield per cow in Holstein group clones was less than that of the original cow, whereas Jersey group clones showed a higher average milk yield than the original cow. In both groups of cloned cows, inter-individual variation in milk production was relatively large; however, the coefficient of variation was less than 10%. Our results suggest that the cloned cows have normal growth, reproductive, and lactation characteristics, and thus normal productivity, despite having reduced telomere lengths.

Nucleotide polymorphism in the Adh1 locus region of the wild rice Oryza rufipogon.

Nucleotide variation in the alcohol dehydrogenase (Adh1) locus region of the wild rice Oryza rufipogon and its related species was analysed to clarify the maintenance mechanism of DNA variation in Oryza species. The estimated nucleotide diversity in the Adh1 locus region of O. rufipogon was 0.002, which was one of the lowest values detected in nuclear loci of plant species investigated so far. Tests of neutrality detected significantly negative deviation from the neutral mutation model for the coding region, especially for replacement sites. When each of the ADH1 domains was considered, significance was detected only for the catalytic domain 1. These results suggest purifying selection in the Adh1 coding region. In the phylogenetic tree of Oryza species based on Adh1 variation, cultivated rice O. sativa subspp. japonica and indica were included in the cluster of O. rufipogon. The genetic distance of the Adh1 region between O. rufipogon and O. sativa was as low as the nucleotide diversity of O. rufipogon. These results imply that O. rufipogon and O. sativa cannot be classified based on the nucleotide variation of Adh1. No replacement divergence between O. rufipogon and the other three A-genome species (O. glumaepatula, O. barthii and O. meridionalis) were detected, indicating that ADH1 is conserved in the A-genome species. On the other hand, between O. rufipogon and the E-genome species O. australiensis, replacement changes were detected only in the catalytic domain 1. The difference in replacement substitutions between the A- and E-genome species may be related to adaptive changes in the ADH1 domains, reflecting environmental differences where the species encounter anaerobic stress.

Chlamydia pneumoniae infection associated with enhanced MRI spinal lesions in multiple sclerosis.

Cerebrospinal fluid (CSF) from 66 patients with multiple sclerosis (MS) and 25 patients with other neurological diseases (OND) were examined for the infection of Chlamydia pneumoniae by culture, polymerase chain reaction (PCR) assay, and determination of antibodies to C. pneumoniae. PCR was positive not only in 9 of 28 (32%) patients with MS but also in 2 patents with inflammatory disorders in 15 (13%) OND controls (p = 0.18). Viable C. pneumoniae was isolated from one patient with MS and one with paraneoplastic encephalomyelitis. C. pneumoniae could be detected only in cell-containing CSF. In MS, enhanced spinal magnetic resonance imaging (MRI) lesions were detected in all of four PCR-positive patents but none of five PCR-negative patients, and the difference was significant (p = 0.0079). However, no correlation was found between enhanced brain MRI lesions and CSF C. pneumoniae DNA. Elevated titers of anti-C. pneumoniae IgG were detected in CSF in 13 of 66 (20%) patients with MS and 1 of 25 (4%) OND controls (p = 0.064). CNS C. pneumoniae infection is not uncommon in MS as well as in other inflammatory disorders of the nervous system. The association of active spinal lesions with Chlamydia in CSF collected by lumber puncture suggests the detection of a recent infection. On the other hand, the lack of association of active MS brain lesions with CSF Chlamydia and the presence of PCR-positive patents who are clinically stable and have no enhancing MRI lesions imply the existence of a chronic infectious process.

Seroepidemiology of Chlamydia pneumoniae in Japan between 1991 and 2000.

AIM: To clarify the endemic and epidemic status of Chlamydia pneumoniae in Japan, the incidence of anti-C pneumoniae antibody was evaluated over a period of 10 years. METHOD: Serum samples were collected from 4756 healthy individuals aged 6 months to 88 years (2488 male and 2268 female individuals) between 1991 and 2000. The antibody titre was determined by a microimmunofluorescence test. RESULTS: After stratification by age and sex in each year, distinct peaks with prevalences of 73.3% and 73.0% were noted in 1993 and 1999, respectively. The lowest prevalence rate was seen in 1996 (59.0%). The epidemic cycle has been estimated to be almost six years in this geographical area. CONCLUSIONS: Chlamydia pneumoniae infection is highly endemic in Japan, as it is in Western countries, and there is a year to year variability. Long term studies in Japan are needed to clarify the epidemic occurrence of C pneumoniae infection.

In vitro and in vivo activities of sitafloxacin against Chlamydia spp.

The in vitro and in vivo antichlamydial activity of sitafloxacin was investigated. The MICs and minimal chlamydiacidal concentrations of sitafloxacin for various species of chlamydia ranged from 0.031 to 0.125 microg/ml. Sitafloxacin had an excellent therapeutic effect on experimental Chlamydia psittaci pneumonia and was more potent than tosufloxacin, ofloxacin, and ciproflxacin, although slightly less potent than sparfloxacin.

[A case of Coxiella burnetii pneumonia in an adult].

A 49-year-old man visited our hospital complaining of a continuous high-grade fever and cough which had appeared during his stay in Indonesia. He was admitted on the same day because his laboratory data showed marked inflammatory changes and his chest radiograph revealed an infiltrative shadow in the right upper lung field. Initial treatment with beta-lactams was not effective and both his symptoms and his chest radiograph worsened. However, treatment with erythromycin clearly had an effect. Then, we carried out several tests for detection of atypical pathogens including Mycoplasma and Chlamydia. Finally, the case was diagnosed as one of Coxiella burnetii pneumonia because the DNA of C. burnetii was detected from his sera and seroconversion of C. burnetii--specific antibody was observed among paired serum samples. C. burnetii is one of the most commonly recognized pathogens among community-acquired pneumonias in Western countries, but in Japan, reports of community-acquired C. burnetii pneumonia have been rare. This difference may be due to the features of Q fever, in which there are large differences in frequency and form from country to country and among areas of the same country. Surveillance of C. burnetii pneumonia in Japan and different area will be required.

In vitro activity of telithromycin, a new ketolide, against Chlamydia pneumoniae.

The in vitro activity of telithromycin, a new ketolide, was compared with those of roxithromycin, azithromycin, clarithromycin and erythromycin A against 20 strains of Chlamydia pneumoniae. The MICs and minimal chlamydiacidal concentrations of telithromycin for the 20 C. pneumoniae strains both ranged between 0.031 and 0.25 mg/L. Telithromycin was twice as active as roxithromycin, azithromycin and erythromycin A, but less active than clarithromycin. These results appear to indicate that telithromycin is an effective antibiotic that should play some role in the treatment of respiratory tract infections caused by C. pneumoniae.

The 7.5-kb common plasmid is unrelated to the drug susceptibility of Chlamydia trachomatis.

Using a new plaque cloning technique, we obtained unique Chlamydia trachomatis strains, which were confirmed to be free of the 7.5-kb common plasmid and glycogen in inclusions. The inclusions in plasmid-free and glycogen-negative strains were characterized by a target-like bull's eye morphology that appeared with the formation of a central translucent area that began to be seen clearly at 30 h postinoculation. The clear zone was composed of gel materials originating from reticulate bodies (RBs) that were abnormally large in size and irregular in shape, although one could not differentiate the aberrant RBs from normal RBs at early stages of development. The in-vitro susceptibility of these strains to various chemotherapeutic antibiotics was tested by comparison with their parent strains possessing the common plasmid. No difference was detected for any of the antibiotics tested, indicating that the 7.5-kb common plasmid is unrelated to the drug susceptibility of C. trachomatis.

Prevalence of asymptomatic infection with Chlamydia pneumoniae in subjectively healthy adults.

STUDY OBJECTIVE: To investigate the prevalence of asymptomatic infection with Chlamydia pneumoniae in subjectively healthy adults. DESIGN: Prospective study. SETTING: Kawasaki Medical School Hospital in Kurashiki, Japan. PARTICIPANTS: Total of 1,018 asymptomatic healthy adults (age range, 22 to 50 years; mean age, 32.4 years; 482 men and 536 women). MEASUREMENTS AND RESULTS: Nasopharyngeal swab specimens were obtained from all subjects and analyzed by isolation in cell cultures and polymerase chain reaction (PCR) test for C pneumoniae. Serum samples were also obtained and tested for C pneumoniae-specific antibodies by the microimmunofluorescence test. Of 1,018 specimens tested, 14 specimens (1.4%) were judged positive by culture and/or the PCR. Thirteen specimens were PCR positive, and 4 specimens were culture positive. There were three specimens positive by both tests and 11 specimens positive with discrepancies in culture and PCR results. None of the individuals met the serologic criteria for acute infection. Of 1,018 sera tested, 64.1% of men and 58.0% of women had antibody to C pneumoniae. The overall prevalence of antibody was 60.9%. Forty individuals (3.9%) had an IgG titer of > or = 1:512 or IgM titer of > or = 1:16. CONCLUSIONS: Our data suggest that asymptomatic infection with C pneumoniae may occur in subjectively healthy adults.