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Bismuth-based layered compounds have been considered during the last years as interesting materials for high temperature piezoelectric applications, due to their stability and wide thermal range of the ferroelectric activity. The high electrical conductivity present at high temperatures has been a disadvantage for the potential applications of these compounds. On Bi4Ti3O12 (BIT), different doping, such as Nb5+ and W6+ were used to increase resistivity. It has been shown that Nb5+ doping modifies piezoelectric response, passing from relatively high hysteretic to linear and almost completely non-hysteretic. In the present work, the effect of Nb5+ doping related to the conduction response is investigated. Studies of the I-V curves as a function of the temperature allows us, for the first time, to measure the conductivity of these compounds at room temperature (RT) and to discuss which are the microstructural elements that control the conductivity of the material using a serial electrical model. It is shown that at temperatures between RT and 125ºC the grain boundary conductivity limits the total conductivity. At higher temperatures, the material conducts mainly through the bulk of grains. Conduction type, conductivity thermal regimes and chemical composition may explain the change in the piezoelectric behaviour.Compuestos laminares de bismuto han sido considerados en los últimos años materiales interesantes como piezoeléctricos en aplicaciones de alta temperatura, debido a su estabilidad y amplio rango térmico de existencia de actividad ferroeléctrica. Sin embargo, la elevada conductividad presente a altas temperaturas ha sido una desventaja para las potenciales aplicaciones de estos compuestos. En el caso de Bi4Ti3O12 (BIT), diferentes dopantes como Nb5+ o W6+ han sido empleados para aumentar la resistencia eléctrica del material. Es conocido que el dopado con Nb5+ modifica la respuesta piezoeléctrica del material pasando de presentar una elevada histéresis a prácticamente lineal y no histerética. En este trabajo se estudia el efecto de este tipo de dopado sobre la respuesta de la conductividad. Estudios eléctricos mediante la medida de curvas I-V en función de la temperatura nos permiten, por primera vez en la literatura, medir la conductividad de estos compuestos a temperaturas entorno a la ambiente (TA) y discutir que elemento mesoestructural controla la conductividad total del material, usando un model eléctrico en serie. Como resultado, se ha visto que a temperaturas entre TA y 125ºC es la conductividad del borde de grano la que limita la conductividad de todo el compuesto. A temperaturas superiores, el material conduce principalmente a través del interior de grano. Combinaremos los resultados de los estudios sobre tipo de conducción, regímenes térmicos y la composición química para interpretar los cambios en la respuesta general introducidos por el dopado.

By using a bilayer serial model, the study has shown that heterogeneous piezoelectric structures may exhibit Maxwell-Wagner type piezoelectric relaxation if the constitutent materials possess different dielectric and piezoelectric properties. The model is relevant for a wide range of heterogeneous structures.

A Pseudomonas fluorescens strain (CHAo) involved in suppression of black root rot caused by Thielaviopsis basicola in the field, inhibited T. basicola when colonizing roots grown under sterile conditions or when grown on culture media. Under these conditions it produced siderophores (iron chelating compounds), cyanic acid, and several antibiotics. Iron-free siderophores inhibited neither the germination of endoconidia or chlamydospores nor the mycelial growth of T. basicola, but reduced the production of endoconidia. On the contrary, siderophores complexed with Fe3+ strongly inhibited mycelium growth and spore germination; free iron was less toxic than iron-bound siderophores. Therefore, contrary to what was believed to date, siderophores seem to be toxic not because they deplete iron but because they increase its concentration to the point where it becomes highly toxic. Cyanic acid and the antibiotics also inhibited the growth of T. basicola. Whether all these compounds are involved in disease control in the soil remains, however, to be determined. [ABSTRACT FROM AUTHOR]

Introduction: This study evaluates the gait analysis obtained by Inetial Measurement Units (IMU) before and after surgical management of Spastic Equino Varus Foot (SEVF) in hemiplegic post-stroke patients and to compare it with the functional results obtained in a monocentric prospective cohort., Methods: Patients with post-stroke SEVF, who underwent surgery in a single hospital between November 2019 and December 2021 were included. The follow-up duration was 6 months and included a functional analysis using Goal Attainment Scaling (GAS) and a Gait analysis using an innovative Multidimensional Gait Evaluation using IMU: the semiogram., Results: 20 patients had a gait analysis preoperatively and at 6 months postoperatively. 90% (18/20) patients had a functional improvement (GAS T score ≥ 50) and 50% (10/20) had an improvement in walking technique as evidenced by the cessation of the use of a walking aid (WA). In patients with functional improvement and modification of WA the change in the semiogram area was + 9.5%, sd = 27.5%, and it was + 15.4%, sd = 28%. In the group with functional improvement without change of WA. For the 3 experiences (two patients) with unfavorable results, the area under the curve changed by + 2.3%, -10.2% and - 9.5%. The measurement of the semiogram area weighted by average speed demonstrated very good reproducibility (ICC(1, 3) = 0.80)., Discussion: IMUs appear to be a promising solution for the assessment of post-stroke hemiplegic patients who have undergone SEVF surgery. They can provide a quantified, objective, reliable in individual longitudinal follow up automated gait analysis solution for routine clinical use. Combined with a functional scale such as the GAS, they can provide a global analysis of the effect of surgery., (© 2024. The Author(s).)

Background: Recently, the use of inertial measurement units (IMUs) in quantitative gait analysis has been widely developed in clinical practice. Numerous methods have been developed for the automatic detection of gait events (GEs). While many of them have achieved high levels of efficiency in healthy subjects, detecting GEs in highly degraded gait from moderate to severely impaired patients remains a challenge. In this paper, we aim to present a method for improving GE detection from IMU recordings in such cases., Methods: We recorded 10-meter gait IMU signals from 13 healthy subjects, 29 patients with multiple sclerosis, and 21 patients with post-stroke equino varus foot. An instrumented mat was used as the gold standard. Our method detects GEs from filtered acceleration free from gravity and gyration signals. Firstly, we use autocorrelation and pattern detection techniques to identify a reference stride pattern. Next, we apply multiparametric Dynamic Time Warping to annotate this pattern from a model stride, in order to detect all GEs in the signal., Results: We analyzed 16,819 GEs recorded from healthy subjects and achieved an F1-score of 100%, with a median absolute error of 8 ms (IQR [3-13] ms). In multiple sclerosis and equino varus foot cohorts, we analyzed 6067 and 8951 GEs, respectively, with F1-scores of 99.4% and 96.3%, and median absolute errors of 18 ms (IQR [8-39] ms) and 26 ms (IQR [12-50] ms)., Conclusions: Our results are consistent with the state of the art for healthy subjects and demonstrate a good accuracy in GEs detection for pathological patients. Therefore, our proposed method provides an efficient way to detect GEs from IMU signals, even in degraded gaits. However, it should be evaluated in each cohort before being used to ensure its reliability., (© 2024. The Author(s).)

Background: Quantifying gait using inertial measurement units has gained increasing interest in recent years. Highly degraded gaits, especially in neurological impaired patients, challenge gait detection algorithms and require specific segmentation and analysis tools. Thus, the outcomes of these devices must be rigorously tested for both robustness and relevancy in order to recommend their routine use. In this study, we propose a multidimensional score to quantify and visualize gait, which can be used in neurological routine follow-up. We assessed the reliability and clinical coherence of this method in a group of severely disabled patients with progressive multiple sclerosis (pMS), who display highly degraded gait patterns, as well as in an age-matched healthy subjects (HS) group., Methods: Twenty-two participants with pMS and nineteen HS were included in this 18-month longitudinal follow-up study. During the follow-up period, all participants completed a 10-meter walk test with a U-turn and back, twice at M0, M6, M12, and M18. Average speed and seven clinical criteria (sturdiness, springiness, steadiness, stability, smoothness, synchronization, and symmetry) were evaluated using 17 gait parameters selected from the literature. The variation of these parameters from HS values was combined to generate a multidimensional visual tool, referred to as a semiogram., Results: For both cohorts, all criteria showed moderate to very high test-retest reliability for intra-session measurements. Inter-session quantification was also moderate to highly reliable for all criteria except smoothness, which was not reliable for HS participants. All partial scores, except for the stability score, differed between the two populations. All partial scores were correlated with an objective but not subjective quantification of gait severity in the pMS population. A deficit in the pyramidal tract was associated with altered scores in all criteria, whereas deficits in cerebellar, sensitive, bulbar, and cognitive deficits were associated with decreased scores in only a subset of gait criteria., Conclusions: The proposed multidimensional gait quantification represents an innovative approach to monitoring gait disorders. It provides a reliable and informative biomarker for assessing the severity of gait impairments in individuals with pMS. Additionally, it holds the potential for discriminating between various underlying causes of gait alterations in pMS., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2023 Voisard, de l'Escalopier, Vienne-Jumeau, Moreau, Quijoux, Bompaire, Sallansonnet, Brechemier, Taifas, Tafani, Drouard, Vayatis, Ricard and Oudre.)

Biological integration of an implant to surrounding bone is an important event for its clinical success and is driven by numerous factors, including the attraction of bone forming cells. The implant's surface properties influence the initial cell response at the cell/material interface, ultimately affecting the rate and quality of new tissue formation and the stability of the implant. As a consequence, various surface treatments have been developed to increase the clinical performance of titanium-based implants. Among them, the Anodic Plasma-Chemical (APC) technique allows for the combined chemical and morphological modification of titanium surfaces in a single process step. In the present study, we compared the potential of APC surface treatment of high-strength titanium alloys with vacuum plasma spray treatment and yellow gold anodization in supporting osteogenic differentiation of two different osteoprogenitor cell types. Both human fetal osteoblast cell line (hFOB1.19) and human mesenchymal stromal cells showed extensive cell spreading, faster cell growth and differentiation on APC surfaces compared to vacuum plasma spray treated and yellow gold anodized surfaces. Our findings showed that APC titanium-based surfaces provided an effective substrate for osteoprogenitor cells adhesion, proliferation and differentiation., (Copyright © 2010 Elsevier Ltd. All rights reserved.)

A quantitative method using Rockwell C indentation was developed to study the adhesion of diamond-like carbon (DLC) protective coatings to the CoCrMo biomedical implant alloy when immersed in phosphate-buffered saline (PBS) solution at 37 degrees C. Two kinds of coatings with thicknesses ranging from 0.5 up to 16 microns were investigated, namely DLC and DLC/Si-DLC, where Si-DLC denotes a 90 nm thick DLC interlayer containing Si. The time-dependent delamination of the coating around the indentation was quantified by means of optical investigations of the advancing crack front and calculations of the induced stress using the finite element method (FEM). The cause of delamination for both types of coatings was revealed to be stress-corrosion cracking (SCC) of the interface material. For the DLC coating a typical SCC behavior was observed, including a threshold region (60J m(-2)) and a "stage 1" crack propagation with a crack-growth exponent of 3.0, comparable to that found for ductile metals. The DLC/Si-DLC coating exhibits an SCC process with a crack-growth exponent of 3.3 and a threshold region at 470 Jm(-2), indicating an adhesion in PBS at 37 degrees C that is about eight times better than that of the DLC coating. The SCC curves were fitted to the reaction controlled model typically used to explain the crack propagation in bulk soda lime glass. As this model falls short of accurately describing all the SCC curves, limitations of its application to the interface between a brittle coating and a ductile substrate are discussed.

In Pseudomonasfluorescens strain CHAO, the response regulator gene gacA controls expression of extracellular enzymes and antifungal secondary metabolites, which are important for this strain's biocontrol activity in the plant rhizosphere. Two Tn5 insertion mutants of strain CHA0 that had the same pleiotropic phenotype as gacA mutants were complemented by the gacS sensor kinase gene of P. syringae pv. syringae as well as that of P. fluorescens strain Pf-5, indicating that both transposon insertions had occurred in the gacS gene of strain CHA0. This conclusion was supported by Southern hybridisation using a gacS probe from strain Pf-5. Overexpression of the wild-type gacA gene partially compensated for the gacS mutation, however, the overexpressed gacA gene was not stably maintained, suggesting that this is deleterious to the bacterium. Strain CHA0 grown to stationary phase in nutrient-rich liquid media for several days accumulated spontaneous pleiotropic mutants to levels representing 1.25% of the population; all mutants lacked key antifungal metabolites and extracellular protease. Half of 44 spontaneous mutants tested were complemented by gacS, the other half were restored by gacA. Independent point and deletion mutations arose at different sites in the gacA gene. In competition experiments with mixtures of the wild type and a gacA mutant incubated in nutrient-rich broth, the mutant population temporarily increased as the wild type decreased. In conclusion, loss of gacA function can confer a selective advantage on strain CHA0 under laboratory conditions.

Pseudomonas fluorescens CHA0 produces several secondary metabolites, e.g., the antibiotics pyoluteorin (Plt) and 2,4-diacetylphloroglucinol (Phl), which are important for the suppression of root diseases caused by soil-borne fungal pathogens. A Tn5 insertion mutant of strain CHA0, CHA625, does not produce Phl, shows enhanced Plt production on malt agar, and has lost part of the ability to suppress black root rot in tobacco plants and take-all in wheat. We used a rapid, two-step cloning-out procedure for isolating the wild-type genes corresponding to those inactivated by the Tn5 insertion in strain CHA625. This cloning method should be widely applicable to bacterial genes tagged with Tn5. The region cloned from P. fluorescens contained three complete open reading frames. The deduced gene products, designated PqqFAB, showed extensive similarities to proteins involved in the biosynthesis of pyrroloquinoline quinone (PQQ) in Klebsiella pneumoniae, Acinetobacter calcoaceticus, and Methylobacterium extorquens. PQQ-negative mutants of strain CHA0 were constructed by gene replacement. They lacked glucose dehydrogenase activity, could not utilize ethanol as a carbon source, and showed a strongly enhanced production of Plt on malt agar. These effects were all reversed by complementation with pqq+ recombinant plasmids. The growth of a pqqF mutant on ethanol and normal Plt production were restored by the addition of 16 nM PQQ. However, the Phl- phenotype of strain CHA625 was due not to the pqq defect but presumably to a secondary mutation. In conclusion, a lack of PQQ markedly stimulates the production of Plt in P. fluorescens.

Ustilago maydis secretes ferrichrome-type siderophores, ferric-ion-binding compounds, in response to iron starvation. TA2701, a non-enterobactin-producing, non-ferrichrome-utilizing mutant of Salmonella typhimurium LT-2, was employed as a biological indicator in a novel screening method to isolate three N-methyl-N'-nitro-N-nitrosoguanidine-induced U. maydis mutants defective in the regulation of ferrichrome-type siderophore biosynthesis. These mutants displayed a constitutive phenotype; they produced siderophores in the presence of iron concentrations that would typically repress siderophore synthesis in wild-type strains. A 4.8-kb fragment of U. maydis genomic DNA capable of restoring normal regulation of siderophore biosynthesis in the constitutive mutants was identified. This segment of DNA contains an intronless open reading frame that specifies a protein of 950 amino acids containing two finger motifs similar to those found in the erythroid transcription factor GATA-1. Disruption of this open reading frame in a wild-type strain gave rise to cells that produced siderophores constitutively. Genetic studies indicated that the disruption mutation was allelic to the chemically induced mutations, confirming that the structural gene for a regulator rather than a suppressor gene had been cloned. Northern (RNA) analysis of the gene revealed a 4.2-kb transcript that is expressed constitutively at low levels in wild-type cells. The data support the hypothesis that this gene, which we designate urbs1 (Ustilago regulator of biosynthesis of siderophores), acts directly or indirectly to repress biosynthesis of siderophores in U. maydis.

Pseudomonas fluorescens CHA0 colonizes plant roots, produces several secondary metabolites in stationary growth phase, and suppresses a number of plant diseases, including Thielaviopsis basicola-induced black root rot of tobacco. We discovered that mutations in a P. fluorescens gene named gacA (for global antibiotic and cyanide control) pleiotropically block the production of the secondary metabolites 2,4-diacetylphloroglucinol (Phl), HCN, and pyoluteorin. The gacA mutants of strain CHA0 have a drastically reduced ability to suppress black root rot under gnotobiotic conditions, supporting the previous observations that the antibiotic Phl and HCN individually contribute to the suppression of black root rot. The gacA gene is directly followed by a uvrC gene. Double gacA-uvrC mutations render P. fluorescens sensitive to UV irradiation. The gacA-uvrC cluster is homologous to the orf-2 (= uvrY)-uvrC operon of Escherichia coli. The gacA gene specifies a trans-active 24-kDa protein. Sequence data indicate that the GacA protein is a response regulator in the FixJ/DegU family of two-component regulatory systems. Expression of the gacA gene itself was increased in stationary phase. We propose that GacA, perhaps activated by conditions of restricted growth, functions as a global regulator of secondary metabolism in P. fluorescens.

Pseudomonas fluorescens CHA0 suppresses black root rot of tobacco, a disease caused by the fungus Thielaviopsis basicola. Strain CHA0 excretes several metabolites with antifungal properties. The importance of one such metabolite, hydrogen cyanide, was tested in a gnotobiotic system containing an artificial, iron-rich soil. A cyanidenegative (hcn) mutant, CHA5, constructed by a gene replacement technique, protected the tobacco plant less effectively than did the wild-type CHA0. Complementation of strain CHA5 by the cloned wild-type hcn genes restored the strain's ability to suppress disease. An artificial transposon carrying the hcn genes of strain CHA0 (Tnhcn) was constructed and inserted into the genome of another P.fluorescens strain, P3, which naturally does not produce cyanide and gives poor plant protection. The P3::Tnhcn derivative synthesized cyanide and exhibited an improved ability to suppress disease. All bacterial strains colonized the roots similarly and did not influence significantly the survival of T.basicola in soil. We conclude that bacterial cyanide is an important but not the only factor involved in suppression of black root rot.