Giant magnon spin conductivity in ultrathin yttrium iron garnet films.

Conductivities are key material parameters that govern various types of transport (electronic charge, spin, heat and so on) driven by thermodynamic forces. Magnons, the elementary excitations of the magnetic order, flow under the gradient of a magnon chemical potential1-3 in proportion to a magnon (spin) conductivity. The magnetic insulator yttrium iron garnet is the material of choice for efficient magnon spin transport. Here we report a giant magnon conductivity in thin yttrium iron garnet films with thicknesses down to 3.7 nm when the number of occupied two-dimensional subbands is reduced from a large number to a few, which corresponds to a transition from three-dimensional to two-dimensional magnon transport. We extract a two-dimensional magnon spin conductivity around 1 S at room temperature, comparable to the (electronic) conductivity of the high-mobility two-dimensional electron gas in GaAs quantum wells at millikelvin temperatures4. Such high conductivities offer opportunities to develop low-dissipation magnon-based spintronic devices.

Developing a social prescribing local system in a European Mediterranean country: a feasibility study to promote active and healthy aging.

BACKGROUND: Social Prescribing (SP) is an innovative strategy to respond to the non-clinical health needs of the population. A Social Prescribing Local System (SPLS) can be defined as a set of joined community, health, and social organizations to foster SP-oriented activities. This study aimed to develop and assess the feasibility of an SPLS implemented in a Mediterranean country, to promote health and wellbeing and contribute to active and healthy aging. METHODS: A mixed-methods approach was followed, including three sequential components: 1) Cross-sectional online survey targeting health professionals (HP) working in a primary health care cluster, Portugal's southern region; 2) Pilot study implementing an on-the-job training program for HP, designed to meet identified training needs in the survey; 3) Focus group (FG) with the HP who participated in the pilot study, two individual interviews, with an elderly patient and a community provider for assessing the satisfaction with the pilot test. RESULTS: Sixty-five HP completed the survey; of these, 13 completed the theoretical part of the on-the-job training program; and six (out of these 13) completed the full program. Five HP participated in the FG, one patient and one community provider were interviewed. The surveyed HP perceived as facilitators to implement SP: an automatic system of notifications to prompt the use of SP, contribute to patient satisfaction, human and community resources' stability. The survey also highlighted barriers to SP implementation: length of appointments, shortage of human resources, data records confidentiality, low patient adherence rates, bureaucratic issues, time constraints, and financial costs. Participants were satisfied with the training. Identified SPLS implementation benefits were grouped into four dimensions (from the qualitative approach): gains for patients' health and wellbeing, support for the health services, sustainability of the community resources, and HP' professional satisfaction. CONCLUSIONS: Our study took the first steps towards the implementation of an SPLS. Findings reinforce that training HP in SP and on-the-job training seems feasible. This approach was well received and appears to represent a suitable and sustainable strategy. It can promote professional satisfaction, support health services, contribute to the stability of community resources, improve health and promote active and healthy aging.

Spin-to-charge conversion and interface-induced spin Hall magnetoresistance in yttrium iron garnet/metallic bilayers.

We report the investigation of spin-to-charge current interconversion process in hybrid structures of yttrium iron garnet (YIG)/metallic bilayers by means of two different experimental techniques: spin pumping effect (SPE) and spin Hall magnetoresistance (SMR). We demonstrate the evidence of a correlation between spin-to-charge conversion and SMR in bilayers of YIG/Pd, YIG/Pt, and YIG/IrMn. The correlation was verified directly in the spin Hall angles and the amplitudes of the voltage signals measured by the SPE and SMR techniques. The detection of SMR was carried out using the modulated magnetoresistance technique and lock-in amplifier detection. For these measurements, we present a simple model for the interpretation of the results. The results allow us to conclude that indeed the interface in the YIG/metallic bilayers has a dominant role in the spin-to-charge current conversion and SMR.

Cr (VI) reduction by photocatalyic process: Nb2O5 an alternative catalyst.

In this study, Nb2O5 catalyst was applied in the photocatalytic process for the Chromium reduction. Cr (VI) is a compound classified as highly toxic and often found in industrial tannery effluents. The techniques used for the photocatalytic material characterization were: X-ray diffraction, Specific surface area (B.E.T method), photo-acoustic spectroscopy, Scanning Electron Microscopy (SEM) and X-ray Dispersive Energy Spectrometry (EDS). A comparison between Nb2O5 and TiO2 (widely used in photocatalytic reactions) indicated that Nb2O5 has 20% more Cr (VI) reduction than TiO2. Tests carried out with Nb2O5 calcined at 500 °C and with non-calcined Nb2O5 showed that the heat treatment did not favor the reaction. Parameters such as pH, radiation intensity, initial concentration of Cr (VI) and amount of catalyst were studied. The results indicated that the acid (pH 2), emitted radiation intensity (250 W), initial concentration Cr (VI) at 10 mg L-1 and 1.5 g L-1 Nb2O5 non-calcined are the process optimal conditions. In addition, the reuse tests for Nb2O5 in consecutive cycles four, were realized. Photostability was maintained at approximately 90% for all cycles when Nb2O5 calcined was used. On the other hand, when using Nb2O5 non-calcined reduced by 21% during the four tests. This behavior is possibly due to the greater adsorption capacity of the non-calcined material. Making the Nb2O5 catalyst attractive for considering larger scale tests.

Traumatic total iridectomy with "pseudo-iris".

Blunt trauma may cause a wound in the site of the cataract incision in patients that have received this surgery, even decades after the procedure. The opening of the incision seems to avoid globe rupture, acting as a "liberating valve" We report a case of a 92-year-old woman with advanced dry macular degeneration who is referred to our department after suffering a blunt trauma in her left eye with a nightstand. She was diagnosed of a traumatic total iridectomy due to iris extrusion through a 2.75 mm cataract incision after injury and vitreous hemorrhage, sparing an intact intraocular lens and capsular bag, as well as peripheral remnants of cortical material in the capsular bag and anterior capsule opacity resembling "pseudoiris". After the vitreous hemorrhage was completely resolved she referred no photophobia. Consequently, although a bad visual acuity of the patient could mitigate patient's photophobia, we believed that her "pseudoiris" plays an important role in diminishing the possible symptoms of photophobia.

Impact of Physiological Signals Acquisition in the Emotional Support Provided in Learning Scenarios.

Physiological sensors can be used to detect changes in the emotional state of users with affective computing. This has lately been applied in the educational domain, aimed to better support learners during the learning process. For this purpose, we have developed the AICARP (Ambient Intelligence Context-aware Affective Recommender Platform) infrastructure, which detects changes in the emotional state of the user and provides personalized multisensorial support to help manage the emotional state by taking advantage of ambient intelligence features. We have developed a third version of this infrastructure, AICARP.V3, which addresses several problems detected in the data acquisition stage of the second version, (i.e., intrusion of the pulse sensor, poor resolution and low signal to noise ratio in the galvanic skin response sensor and slow response time of the temperature sensor) and extends the capabilities to integrate new actuators. This improved incorporates a new acquisition platform (shield) called PhyAS (Physiological Acquisition Shield), which reduces the number of control units to only one, and supports both gathering physiological signals with better precision and delivering multisensory feedback with more flexibility, by means of new actuators that can be added/discarded on top of just that single shield. The improvements in the quality of the acquired signals allow better recognition of the emotional states. Thereof, AICARP.V3 gives a more accurate personalized emotional support to the user, based on a rule-based approach that triggers multisensorial feedback, if necessary. This represents progress in solving an open problem: develop systems that perform as effectively as a human expert in a complex task such as the recognition of emotional states.

The impact of consumption of ultra-processed foods on the nutritional status of adolescents / Impacto del consumo de alimentos ultraprocesados en el estado nutricional de adolescentes

ABSTRACT Because of its composition, ultra-processed foods can contribute to excess weight. The objective of the study was to verify the association between the consumption of ultra-processed foods and overweight in adolescents. We conducted a cross-sectional study with 617 adolescents. Sociodemographic, anthropometric and food consumption data were evaluated. Linear regression analyses were used to verify the association. Ultra-processed foods presented higher proportions of carbohydrates, lipids and saturated fat in relation to the total diet consumed. However, this food group had a lower proportion of proteins and fibers. Intake of ultra-processed foods was more frequent in females and being overweight was positively associated with the ingestion of ultra-processed foods. The high consumption of ultra-processed foods can contribute to weight gain. Therefore, the reduction of consumption of ultra-processed foods should be encouraged to improve eating habits.

RESUMEN Debido a su composición, los alimentos ultraprocesados pueden contribuir al exceso de peso. El objetivo del estudio fue verificar la asociación entre el consumo de alimentos ultraprocesados y el sobrepeso en adolescentes. Estudio transversal con 617 adolescentes. Se evaluaron los datos sociodemográficos, antropométricos y de consumo de alimentos. Se usaron análisis de regresión lineal para verificar la asociación. Los alimentos ultraprocesados presentaron mayores proporciones de carbohidratos, lípidos y grasas saturadas en relación con la dieta total consumida. Sin embargo, este grupo de alimentos tenía una menor proporción de proteínas y fibras. La ingesta de ultraprocesados fue más frecuente en las mujeres y el sobrepeso se asoció positivamente con la ingestión de alimentos ultraprocesados. El alto consumo de alimentos ultraprocesados puede contribuir al aumento de peso. Por lo tanto, se debe fomentar la reducción del consumo de alimentos ultraprocesados para mejorar los hábitos alimenticios.

Understanding the Environmental Impact of a Mine Dam Rupture in Brazil: Prospects for Remediation.

The rupture of the Fundão mine dam in Mariana municipality, Minas Gerais State, Brazil, spilled the tailings across the Doce River basin. These tailings, composed of residues discarded from the beneficiation of iron ore, are rich in SiO and AlO, as well as some ether amine compounds and NaOH. The aim of this study was to assess the distribution of these sediments, as well as their effect on the riparian zones reached, as compared with preserved sites. Sediment deposition in the river resulted in a morphological change from a meandering profile to a braided aspect. The nutrient and mineral content (P, K, Ca, Mg, Cu, Fe, Mn, Zn, and NO) and soil organic matter of the sediments were depleted, whereas NH, Na, and pH increased. A random presence of ether amines in the sediments was confirmed by quantitative and chromatographic analyses, with concentrations ranging from 0 to 57.8 mg kg; Na reached values as high as 150 mg kg. The impact of the dam tailings on biota was assessed by estimating total microbial biomass (phospholipid fatty acids), which were depleted in sediments relative to soils from preserved sites. Overall plant mortality, as well as a low resilience capacity, were also observed. Ether amines and Na present in the sediments had a strong toxic effect in the environment. Identification of these substances as the main impact factors will help guide future remediation efforts.

Alexitimia en pacientes con asma bronquial atendidos en el servicio de alergia de previsora, Camagüey, Cuba / Alexitimia in patients with bronchial asthma treated in the allergy service of Previsora, Camagüey, Cuba

Antecedentes. Algunas conductas y enfermedades humanas están asociadas con alexitimia, que es la incapacidad de hacer corresponder las palabras con las emociones. Material y método. Del universo de 2490 individuos mayores de 15 años pertenecientes al área de salud Previsora, se obtuvo una muestra constituida por 351 asmáticos (casos) y 355 sanos (controles). Se aplicó la Escala de Alexitimia de Toronto (TAS-20); estadística descriptiva; razón de posibilidades (RP) e intervalo de confianza (IC) de 95% para asociación de alexitimia en los casos y en los controles. Chi-cuadrado (chi 2) y análisis de varianza para diferencias. Resultados. La prevalencia de alexitimia fue de 5,9% en los casos y de 4,2 % en los controles (p=0,18); RP de 1,44; IC95,0%: 0,73-2,84. No se detectaron diferencias entre sexo (p=0,322). Las puntuaciones más altas de alexitimia fueron para edades de 40 a 80 años (p=0,056). En comorbilidad, el predominio de alexitimia fue para asma/rinitis (p=0,034). Hubo asociación de alexitimia con asma moderada y grave (p=0,014). Discusión. En la muestra, la prevalencia de alexitimia fue inferior a estudios realizados en otros contextos, resultado éste que requiere nuevos investigaciones que incluyan también a otras disciplinas. Conclusiones. La prevalencia de alexitimia es baja en los pacientes con asma. Sin embargo, en asma/rinitis y en asmáticos moderados/ severos en nuestra muestra se observó incremento de alexitimia. (AU)

Background: Some human behaviors and diseases are associated with alexithymia, which is the inability to match words with emotions. Material and Method: A sample consisting of 351 asthmatics (cases) and 355 healthy (controls) was obtained from a population of 2490 individuals over 15 years of age belonging to the health area of Previsora. The Toronto Alexithymia Scale (TAS-20) was applied; Descriptive statistics; odds ratio (RR) and 95% confidence interval (CI) for association of alexithymia in cases and controls. Chi-square (chi 2) and, analysis of variance for differences.Results: The prevalence of alexithymia was 5.9% in the cases and 4.2% in the controls (p = 0, 18); RP of 1.44; CI (95.0%), 0.73-2.84. No differences were detected between sex (p = 0.322). The highest scores for alexithymia were for ages 40 to 80 years (p = 0.056). In co morbidity, the predominance of alexithymia was for asthma / rhinitis (p = 0.034). There was association of alexithymia with moderate and severe asthma (p = 0.014). Discussion: In the sample, the prevalence of alexithymia was lower than studies performed in other contexts; a result that requires new research that also includes other disciplines. Conclusions: The prevalence of alexithymia is low in patients with asthma. However, in asthma / rhinitis and in moderate / severe asthmatics in our sample, increased alexithymia was observed(AU)

Polyurethane foam impregnated with lignin as a filler for the removal of crude oil from contaminated water.

The present study describes the influence of the concentration of lignin when used as a filler in polyurethane foam for crude oil sorption. The foams (lignin 0-20wt%) were characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), thermogravimetric analysis, contact angle and density. The FTIR analysis confirmed urethane linkage formation, showing that the chemical structure of the polymer was preserved, despite the addition of different lignin concentrations. Thermogravimetric analysis showed that the presence of lignin has altered the onset temperature (Tonset) of the foams, decreasing as the concentration of lignin is increased. The contact angle analysis showed a decrease in the hydrophobicity of the foams with increasing lignin concentration. All modified foams showed an improvement in the oil sorption capacity in a PUF/oil/water system, and the PUF-10 showed an improvement of about 35.5% compared to the PUF-blank. The Langmuir isotherm showed a better fit to the data and predicted a maximum oil adsorption of 28.9gg-1 by the PUF-10. The ΔG° value of -4.4kJmol-1 indicated that crude oil adsorption process by PUF-10 was spontaneous. The results of reuse of the PUF-10 showed that oil removal efficiency remained greater than 95% after five consecutive cycles.

The antimicrobial peptide aureocin A53 as an alternative agent for biopreservation of dairy products.

AIMS: The aim of this study was to investigate the potential of aureocin A53, a staphylococcal antimicrobial peptide, for improving food safety. METHODS AND RESULTS: The antimicrobial activity of aureocin A53 against strains of Listeria monocytogenes isolated from food was tested and the bacteriocin proved to be bactericidal and bacteriolytic against the listerial strains. Aureocin A53 was neither toxic to eukaryotic cell lines nor haemolytic against sheep erythrocytes. It also exhibited a remarkable stability during storage at different temperatures and sensitivity to both simulated gastric juice and bile salts. When the antibacterial activity of aureocin A53 (256 AU ml(-1) ) was tested in skimmed milk artificially inoculated with a L. monocytogenes strain (1·0 × 10(4)  CFU ml(-1) ) isolated from food, during storage at 4°C, the bacteriocin reduced the viable counts by 7·7-log10 units up to 7 days of incubation, when compared with the controls not treated with the bacteriocin. CONCLUSIONS: Aureocin A53 exhibited several features considered important for biopreservation and remained fully active in a food matrix. SIGNIFICANCE AND IMPACT OF THE STUDY: Taken together, the results confirmed that aureocin A53 has potential to be used as a food preservative, representing an alternative to the use of nisin in biopreservation of dairy products.

Screening of inbred popcorn lines for tolerance to low phosphorus.

Increasing phosphorus use efficiency in agriculture is essential for sustainable food production. Thus, the aims of this study were: i) to identify phosphorus use efficiency (PUE) in popcorn lines during the early plant stages, ii) to study the relationship between traits correlated with PUE, and iii) to analyze genetic diversity among lines. To accomplish this, 35 popcorn lines from Universidade Estadual de Maringá breeding program were studied. The experiment was conducted in a growth chamber using a nutrient solution containing two concentrations of phosphorus (P): 2.5 µM or low P (LP) and 250 µM or high P (HP). After 13 days in the nutrient solution, root morphology traits, shoot and root dry weight, and P content of the maize seedlings were measured. A deviance analysis showed there was a high level of genetic variability. An unweighted pair group method with arithmetic mean (UPGMA) clustering analysis identified three groups for the LP treatment (efficient, intermediate, and inefficient) and three groups for the HP treatment (responsive, moderately responsive, and unresponsive). The results of a principal component analysis and selection index were consistent with the UPGMA analysis, and lines 1, 2, 13, 17, 26, and 31 were classified as PUE.

ALERGIA ALIMENTARIA EN LACTANTE ALIMENTADO CON SENO MATERNO EXCLUSIVO / Food allergy in an exclusively breastfed infant

El término alergia alimentaria se refiere a los eventos adversos a alimentos originados por mecanismo inmunológico. La alergia alimentaria puede aparecer en cualquier etapa de la vida. Es un padecimiento que, en general, se manifiesta en el lactante por llanto excesivo, cólicos, vómitos, diarreas, acompañadas de sangre y eccema en la piel. El objetivo de la investigación es demostrar la sensibilización del lactante a los alérgenos alimentarios que recibió en el útero de la madre y a través de la lactancia materna exclusiva. La metodología fue reporte de un caso al que se le suspendió la lactancia materna exclusiva y se introdujo leche en polvo hipoalergénica Puramino. La IgE total fue de 1.136 kU/l y los valores de IgE alérgeno específico para leche, el huevo y el maní mayores de 100 kU/l y para el trigo 24,4 kU/l. Se concluye así que la leche de vaca, el huevo, el maní y el trigo pueden sensibilizar al niño durante el embarazo y a través del seno materno. El uso de una dieta hipoalergénica durante el período de lactante puede revertir el proceso.(AU)

The term food allergy refers to adverse events caused by immunologic mechanism. Food allergy may appear at any stage of life, it is a condition that generally manifests itself in the baby's excessive crying, colic, vomiting, diarrhea accompanied by blood and skin eczema. The objective of the research is to demonstrate awareness infant to food allergens received in the mother's womb and through the exclusive breastfeeding. The methodology was a case report that was suspended exclusive breastfeeding and milk powder was introduced into hypoallergenic Puramino. The total IgE was 1.136 kU/L and allergen specific IgE values for milk, egg and peanut higher than 100 kU/L and wheat: 24. 4 kU/L. It is concluded that cow's milk, egg, peanuts and wheat can sensitize the child during pregnancy and through the womb. The use of a hypoallergenic diet during the infant can reverse the process.(AU)

EFICACIA Y SEGURIDAD DE LA INMUNOTERAPIA EN ALERGIA ALIMENTARIA / Efficacy and safety of immunotherapy in food allergy

El tratamiento de la alergia alimentaria consiste en educar al paciente para evitar la ingestión y, cuando ello no es posible, emplear, entre otros procedimientos, la inmunoterapia con el alimento causal. El objetivo de esta revisión es presentar evidencias sobre eficacia y seguridad de la inmunoterapia en alergia alimentaria y las vías recomendadas para su aplicación. Se accedió a las bases de datos con los descriptores inmunoterapia, alergia alimentaria, vías, desensibilización, eficacia y seguridad. La inmunoterapia oral (ITO) a partir de leche caliente por microondas fue eficaz con buen perfil de seguridad en niños con alergia a leche de vaca (ALV). La quimotripsina inhibe la formación de ßLg y es un nuevo candidato para la inmunoterapia oral en ALV. La ITO con leche y omalizumab ha demostrado mejoría significativa en las medidas de seguridad, pero no en los resultados de eficacia. ITO en niños con alergia al huevo desarrollan tolerancia disminuyendo el riesgo de reacciones alérgicas. También ha aumentado la tolerancia al huevo sin cocinar. En alergia al maní la ITO indujo desensibilización en niños y dio lugar a un aumento significativo en la tolerancia con buen perfil de seguridad. La coadministración del probiótico Lactobacillus rhamnosus a ITO con maní fue eficaz en la inducción de la falta de respuesta y cambios inmunes sostenidos. Se concluye que la ITO puede ser una vía eficaz y segura para la alergia a la leche, huevo y maní. Los protocolos muestran resultados diferentes en eficacia y seguridad, por lo que se requieren más ensayos clínicos.(AU)

The treatment of food allergy is to educate the patient to avoid ingestion and, when it is not possible, to use, among other procedures, the immunotherapy with the offending food. The objective of this review is to present evidence on efficacy and safety of immunotherapy in food allergy and recommended for implementation pathways. It was accessed databases with describer's immunotherapy, food allergy, pathways, desensitization, efficacy and safety. The OIT from microwave hot milk was effective with good safety profile in children with CM. Chymotrypsin inhibits the formation of ßLg and is a new candidate for oral immunotherapy CM. The OIT with milk and omalizumab has shown significant improvement in security measures, but not in the efficacy results. OIT in children with egg allergy develop tolerance decreasing the risk of allergic reactions. It has also increased tolerance uncooked egg. In peanut allergy desensitization induced OIT in children and resulted in a significant increase in tolerance with good safety profile. The co-administration of probiotic Lactobacillus rhamnosus with peanut OIT was effective in inducing immune unresponsiveness and sustained changes. It is concluded that the OIT can be an effective and safe for allergy to milk, egg and peanut route. Protocols show different results in efficacy and safety so more clinical trials are required.(AU)

Polarization effects on the electric properties of urea and thiourea molecules in solid phase.

We present theoretical results for the dipole moment, linear polarizability, and first hyperpolarizability of the urea and thiourea molecules in solid phase. The in-crystal electric properties were determined by applying a supermolecule approach in combination with an iterative electrostatic scheme, in which the surrounding molecules are represented by point charges. It is found for both urea and thiourea molecules that the influence of the polarization effects is mild for the linear polarizability, but it is marked for the dipole moment and first hyperpolarizability. The replacement of oxygen atoms by sulfur atoms increases, in general, the electric responses. Our second-order Møller-Plesset perturbation theory based iterative scheme predicts for the in-crystal dipole moment of urea and thiourea the values of 7.54 and 9.19 D which are, respectively, increased by 61% and 58%, in comparison with the corresponding isolated values. The result for urea is in agreement with the available experimental result of 6.56 D. In addition, we present an estimate of macroscopic quantities considering explicit unit cells of urea and thiourea crystals including environment polarization effects. These supermolecule calculations take into account partially the exchange and dispersion effects. The results illustrate the role played by the electrostatic interactions on the static second-order nonlinear susceptibility of the urea crystal.

Spin-Current to Charge-Current Conversion and Magnetoresistance in a Hybrid Structure of Graphene and Yttrium Iron Garnet.

The use of graphene in spintronic devices depends, among other things, on its ability to convert a spin excitation into an electric charge signal, a phenomenon that requires a spin-orbit coupling (SOC). Here we report the observation of two effects that show the existence of SOC in large-area CVD grown single-layer graphene deposited on a single crystal film of the ferrimagnetic insulator yttrium iron garnet (YIG). The first is a magnetoresistance of graphene induced by the magnetic proximity effect with YIG. The second is the detection of a dc voltage along the graphene layer resulting from the conversion of the spin current generated by spin pumping from microwave driven ferromagnetic resonance into a charge current, which is attributed to the inverse Rashba-Edelstein effect.

Investigation of biotechnological potential of sponge-associated bacteria collected in Brazilian coast.

Marine bacteria are a rich source of structurally unique natural compounds, several of which have shown a wide variety of biological activities. In this study, the metabolites present in the culture supernatants of the eight sponge-associated bacteria were extracted using ethyl acetate, and all extracts showed activity against Staphylococcus aureus. Subsequently, the extracts of the Pseudomonas fluorescens H40 and H41, and Pseudomonas aeruginosa H51 were subjected to solvent partitioning, and the active fractions were submitted to chromatographic separation. Three different active fractions were obtained, one of which was identified as diketopiperazine cyclo-(L-Leu-L-Pro). This substance was bactericidal for Staph. aureus and Ps. aeruginosa and showed cytotoxic activity against HEp-2 tumour cells. Putative gene fragments coding for the type I polyketide synthase (PKS-I) and nonribosomal peptide synthetase (NRPS) domains were PCR-amplified from five and three strains, respectively. The results suggest that sponge-associated bacteria analysed in this study may represent a potential source for production of antimicrobial substances against bacterial pathogens of medical importance.