Current path in light emitting diodes based on nanowire ensembles.

Light emitting diodes (LEDs) have been fabricated using ensembles of free-standing (In, Ga)N/GaN nanowires (NWs) grown on Si substrates in the self-induced growth mode by molecular beam epitaxy. Electron-beam-induced current analysis, cathodoluminescence as well as biased µ-photoluminescence spectroscopy, transmission electron microscopy, and electrical measurements indicate that the electroluminescence of such LEDs is governed by the differences in the individual current densities of the single-NW LEDs operated in parallel, i.e. by the inhomogeneity of the current path in the ensemble LED. In addition, the optoelectronic characterization leads to the conclusion that these NWs exhibit N-polarity and that the (In, Ga)N quantum well states in the NWs are subject to a non-vanishing quantum confined Stark effect.

Properties of uniform diameter InN nanowires obtained under Si doping.

High quality, well-separated, homogeneous sizes and high aspect ratio Si-doped InN nanowires (NWs) were grown by catalyst-free molecular beam epitaxy (MBE) after optimization of the growth conditions. To this end, statistical analysis of NW density and size distribution was performed. The high crystal quality and smooth NW surfaces were observed by high resolution transmission electron microscopy. Spectral photoluminescence has shown the increase of the band filling effect with Si flux, indicating successful n-type doping. A Raman LO scattering mode appears with a pronounced low energy tail, also reported for highly doped InN films.

Selective-area catalyst-free MBE growth of GaN nanowires using a patterned oxide layer.

GaN nanowires (NWs) were grown selectively in holes of a patterned silicon oxide mask, by rf-plasma-assisted molecular beam epitaxy (PAMBE), without any metal catalyst. The oxide was deposited on a thin AlN buffer layer previously grown on a Si(111) substrate. Regular arrays of holes in the oxide layer were obtained using standard e-beam lithography. The selectivity of growth has been studied varying the substrate temperature, gallium beam equivalent pressure and patterning layout. Adjusting the growth parameters, GaN NWs can be selectively grown in the holes of the patterned oxide with complete suppression of the parasitic growth in between the holes. The occupation probability of a hole with a single or multiple NWs depends strongly on its diameter. The selectively grown GaN NWs have one common crystallographic orientation with respect to the Si(111) substrate via the AlN buffer layer, as proven by x-ray diffraction (XRD) measurements. Based on the experimental data, we present a schematic model of the GaN NW formation in which a GaN pedestal is initially grown in the hole.

Enhanced light scattering of the forbidden longitudinal optical phonon mode studied by micro-Raman spectroscopy on single InN nanowires.

In the literature, there are controversies on the interpretation of the appearance in InN Raman spectra of a strong scattering peak in the energy region of the unscreened longitudinal optical (LO) phonons, although a shift caused by the phonon-plasmon interaction is expected for the high conductance observed in this material. Most measurements on light scattering are performed on ensembles of InN nanowires (NWs). However, it is important to investigate the behavior of individual nanowires and here we report on micro-Raman measurements on single nanowires. When changing the polarization direction of the incident light from parallel to perpendicular to the wire, the expected reduction of the Raman scattering was observed for transversal optical (TO) and E(2) phonon scattering modes, while a strong symmetry-forbidden LO mode was observed independently on the laser polarization direction. Single Mg- and Si-doped crystalline InN nanowires were also investigated. Magnesium doping results in a sharpening of the Raman peaks, while silicon doping leads to an asymmetric broadening of the LO peak. The results can be explained based on the influence of the high electron concentration with a strong contribution of the surface accumulation layer and the associated internal electric field.

Reactive arthritis or chronic infectious arthritis?

Microbes reach the synovial cavity either directly during bacteraemia or by transport within lymphoid cells or monocytes. This may stimulate the immune system excessively, triggering arthritis. Some forms of ReA correspond to slow infectious arthritis due to the persistence of microbes and some to an infection triggered arthritis linked to an extra-articular site of infection.

[Rheumatologic manifestations of Lyme borreliosis]. / Les manifestations rhumatologiques de la borréliose de Lyme.

PURPOSE: Lyme borreliosis is a multisystemic infection caused by the spirochaete Borrelia burgdorferi. In European endemic areas like northeast France, articular manifestations are, after neuroborreliosis, the most frequent extra-cutaneous features observed. Among the pathogenic species of Borrelia, Borrelia burgdorferi sensu stricto is the most frequently identified during Lyme arthritis, but others species also seem to be involved. CURRENT KNOWLEDGE AND KEY POINTS: The diagnosis of Lyme arthritis is usually based on combined clinical data and serological laboratory tests. In atypical forms, detection of bacterial DNA could be useful. While mechanisms involved in acute Lyme arthritis are beginning to be better understood, the pathogenesis of chronic arthritis, which concerns about 10% of the patients, remains unknown. Two hypotheses are proposed to explain the prolonged evolution of the articular disease: a chronic persistence of Borrelia burgdorferi, which evades the host immune system within the joint and/or an autoimmune mechanism by molecular mimicry. The antibiotic therapy is codified in acute arthritis, but is not really adapted in chronic Lyme arthritis or post-Lyme syndrome. FUTURE PROSPECTS AND PROJECTS: To prevent the disease, the vaccine available in the United States does not offer complete protection and is not useful in Europe since the species heterogeneity is important for the outer surface protein A. A better understanding of Lyme disease pathogenesis can subsequently lead to new therapeutic or preventive approaches.

[Borrelia strains that cause erythema migrans in Alsace, France]. / Espèces de Borrelia responsables d'érythème migrant en Alsace.

INTRODUCTION: In Europe, Borrelia burgdorferi sensu stricto, Borrelia afzelii and Borrelia garinii are known as pathogens among the Borrelia burgdorferi sensu lato group. Since it is not yet known which Borrelia are responsible for Lyme borreliosis in France, the objective of this study was to identify the species of Borrelia responsible for erythema migrans in the region of Alsace, France. PATIENTS AND METHODS: Eighteen patients with erythema migrans (EM) of more than 5 cm of diameter were included in this prospective study. All patients were investigated at the Strasbourg University Hospital. Patients were biopsied on the active border of their lesion. Cutaneous biopsies of the active border of the lesion were cultivated in BSK-H medium (Sigma) and analysed in vitro by PCR after 8 weeks of culture, using flagellin consensus sequences which are present in all species of Borrelia burgdorferi sensu lato group as primers. Species-specific oligotyping was used for species identification. RESULTS: Among the 18 patients biopsied, 7 had evidence of borrelia infection revealed by culture and/or PCR. Borrelia afzelii was detected in 4 patients and Borrelia garinii in three. CONCLUSION: These preliminary results appear to confirm that Borrelia afzelii and Borrelia garinii are the predominant borrelial species in EM lesions in our geographic area, as in other European countries.

Disease expression of Lyme borreliosis in northeastern France.

Since very little is known about the clinical expression of Lyme borreliosis in Western Europe, a 3-year prospective study was conducted that included all patients seen for suspected Lyme borreliosis at the Strasbourg University Hospital in northeastern France. The diagnosis of Lyme borreliosis was made on the basis of the presence of erythema migrans or on the basis of another suggestive clinical manifestation and laboratory confirmation. A total of 132 patients, 70 women and 62 men, mean age 54 years, had Lyme borreliosis according to these criteria. Within this study group, 77% of the patients were regularly exposed to tick bites and 64% could remember one. Erythema migrans, the most frequent clinical manifestation, occurred in 60% of the patients and was the only sign of Lyme borreliosis in 40%. Lymphocytoma and acrodermatitis chronica atrophicans were rare (1 and 3 patients, respectively). Nervous system involvement (mainly radiculoneuropathy), the second most common clinical manifestation, was found in 40% of the patients and was the only sign of Lyme borreliosis in 22%. Musculoskeletal involvement was present in 26% of the patients and was an isolated finding in 14%. During the study period, no patient was diagnosed with Lyme carditis. There was serological evidence of Lyme borreliosis in 75% of the cases and direct evidence of borrelial infection in 10 (7.5%). The results show that the clinical expression of Lyme borreliosis in northeastern France is similar to that in other European countries but different from that in North America.

Treatment resistant Lyme arthritis caused by Borrelia garinii.

Lyme arthritis is caused in Europe by three main pathogenic species of Borrelia burgdorferi sensu lato: Borrelia burgdorferi sensu stricto, Borrelia garinii, and Borrelia afzelii. Because few synovial samples have yet been analysed by species-specific DNA amplification methods, further studies are needed to define the spectra of clinical manifestations associated with these different species. Two cases of treatment resistant Lyme arthritis are reported here, in which DNA amplification of the flagellin gene followed by dot-blot hybridisation in the synovial fluid identified B garinii as the causative agent. Clinical and biological data did not differ from the usual descriptions of Lyme arthritis, but as the recently reported molecular mimicry between OspA and hLFA1 is not applicable to B garinii, the pathogenesis of the present cases remains unclear. Future studies should aim at assessing the role of B garinii in European Lyme arthritis and its possible pathogenic and therapeutic consequences.

Rapid chondrolysis after an intra-articular leak of bone cement in treatment of a benign acetabular subchondral cyst: an unusual complication of percutaneous injection of acrylic cement.

Percutaneous injection of methylmethacrylate is now increasingly employed to treat bone lesions, both malignant and benign. However, the risks of this procedure are still to be fully established. In this report, we describe a case of rapid chondrolysis appearing after the intra-articular leakage of cement during injection of an acetabular subchondral cyst, resulting in hip replacement. Although the mechanism of such chondrolysis is unknown, this event suggests a chondrolytic effect of the acrylic cement. Thus, it is essential to systematically search for the presence of an intra-articular passage before injecting bone cement into a peri-articular cyst. This unusual complication highlights the need for rigorous evaluation of the benefits and risks of percutaneous injection of acrylic cement in the treatment of benign lesions, especially close to an articulation.

Direct molecular typing of Borrelia burgdorferi sensu lato species in synovial samples from patients with lyme arthritis.

Since Lyme arthritis was first described in the United States, it has now been reported in many countries of Europe. However, very few strains of the causative bacterium, Borrelia burgdorferi, have been isolated from synovial samples. For this reason, different molecular direct typing methods were developed recently to assess which species could be involved in Lyme arthritis in Europe. We developed a simple oligonucleotide typing method with PCR fragments from the flagellin gene of B. burgdorferi sensu lato, which is able to differentiate seven different Borrelia species. Among 10 consecutive PCR-positive patients with Lyme arthritis from the northeastern France, two species were identified in synovial samples: B. burgdorferi sensu stricto in 9 cases and B. garinii in 1 case. Conversely, all B. burgdorferi sensu lato species detected in 10 consecutive PCR-positive biopsies from a second set of patients with erythema migrans from the same geographical area were identified as either B. afzelii or B. garinii (P < 0.001). These results indicate that B. burgdorferi sensu stricto is the principal but not the only Borrelia species involved in Lyme arthritis in northeastern France.

One-step reverse transcriptase PCR method for detection of Borrelia burgdorferi mRNA in mouse Lyme arthritis tissue samples.

A one-step reverse transcriptase PCR (RT-PCR) method for detection of Borrelia burgdorferi mRNA in infected C3H mice is described. This simple procedure, less prone to nucleic acid cross-contamination than the standard method, was found to be 10-fold more sensitive than a classical two-step RT-PCR assay. By using one-step RT-PCR, flagellin mRNAs were detected in synovial and heart tissues from all seven infected mice tested.