title: Systematic review of metal-based alloys with autogenous antibacterial capability

authors: Alshammari, Y

abstract: Pathogenic bacterial infection, especially in surgical and nosocomial settings, is an outstanding and long-lasting challenge due to the ability of microorganisms to evolve and develop mechanisms to become drug-resistant (i.e., superbugs). Considerable efforts have been made in recent years to develop metal-based alloys with autogenous antibacterial capability and to comprehend their mechanism of action, which are systematically reviewed in this work. To comprehensively understand current developments, antibacterial mechanisms (e.g., cell wall/membrane disruption), resistance mechanisms (e.g., permeability barrier), and the primary standardized techniques used to assess the antibacterial response (e.g., plate-count method) are initially introduced. Subsequently, metallic elements with intrinsic antibacterial response are presented alongside a brief discussion of the effects that manufacturing methods have on the ability to achieve metal-based alloys with autogenous antibacterial properties. The several antibacterial metal-based alloys currently being developed, which include Co-, Fe-, Mg-, Ti-, and Zn-based alloys, and some few other metal-based alloy systems, were analyzed in detail, and an effort to comparatively evaluate the antibacterial and mechanical response of the different alloys developed so far was made. Generally, the incorporation of Cu or Ag, which are well-known antibacterial metallic elements, shows remarkable effectiveness against both Gram-positive and Gram-negative bacteria. Additionally, some few other elements like Ca, Ce, and rare earths have been investigated, and some of them show antibacterial capability. The work is complemented with some challenges to be addressed and opportunities to be taken.

text: Systematic review of metal-based alloys with autogenous antibacterial capability Pathogenic bacterial infection, especially in surgical and nosocomial settings, is an outstanding and long-lasting challenge due to the ability of microorganisms to evolve and develop mechanisms to become drug-resistant (i.e., superbugs). Considerable efforts have been made in recent years to develop metal-based alloys with autogenous antibacterial capability and to comprehend their mechanism of action, which are systematically reviewed in this work. To comprehensively understand current developments, antibacterial mechanisms (e.g., cell wall/membrane disruption), resistance mechanisms (e.g., permeability barrier), and the primary standardized techniques used to assess the antibacterial response (e.g., plate-count method) are initially introduced. Subsequently, metallic elements with intrinsic antibacterial response are presented alongside a brief discussion of the effects that manufacturing methods have on the ability to achieve metal-based alloys with autogenous antibacterial properties. The several antibacterial metal-based alloys currently being developed, which include Co-, Fe-, Mg-, Ti-, and Zn-based alloys, and some few other metal-based alloy systems, were analyzed in detail, and an effort to comparatively evaluate the antibacterial and mechanical response of the different alloys developed so far was made. Generally, the incorporation of Cu or Ag, which are well-known antibacterial metallic elements, shows remarkable effectiveness against both Gram-positive and Gram-negative bacteria. Additionally, some few other elements like Ca, Ce, and rare earths have been investigated, and some of them show antibacterial capability. The work is complemented with some challenges to be addressed and opportunities to be taken.

year: 2025-04-07

title: Depth-differentiated, multivariate control of biopore number under different land-use practices

authors: Stolze, Katharina

subjects: earthworm communities

abstract: Earthworms and (tap-)roots impact the soil structure by creating large biopores, affecting infiltration capacity, seepage, nutrient cycling, and soil aeration. Despite the importance of biopores for the functions of soils and the fact that several hundreds of biopores >2 mm in diameter may occur on one square meter of soil, knowledge on the interdependence of soil properties, land-use intensity, and biopore number is still rudimentary. In this study, we investigate the linkage of the number of biopores (>2 mm i.d.) with the earthworm community, root biomass, and soil properties, including pH, water content, soil organic carbon (SOC), as well as the land-use intensity (pasture vs. cropland) as a function of the soil depth (15, 30 and 50 cm). Hypothesized causal relationships among these factors were analyzed by piecewise structural equation modelling (SEM). We found various and novel linkages between roots, earthworms, biopores, and soil properties depending on soil depth. In topsoil (at 15 cm depth), roots directly affected the number of small-sized biopores, and anecic earthworms were related to medium-sized biopores. These effects diminished with depth. We identified land-use intensity as the factor preponderating the relations between biopores, root biomass, and earthworm number in the topsoil horizons, thereby masking other interactions among variables. This appeared as high multicollinearity among variables in the SEM of the topsoil. Land-use intensity effects were found to impact the whole soil profile but decreased with soil depth. To further elucidate the single effects of soil properties on biopore-forming biota and number of biopores in the topsoil, we excluded land-use intensity as a variable in subsequent analyses. Biopores increased with soil pH and soil water content but decreased with increasing SOC. Based on our SEM analysis, we conclude that the occurrence, frequency, and persistence of biopores are the consequence of intricate interdependencies between earthworm communities, roots, and site-specific soil properties, governed by land-use intensity.

text: Depth-differentiated, multivariate control of biopore number under different land-use practices Earthworms and (tap-)roots impact the soil structure by creating large biopores, affecting infiltration capacity, seepage, nutrient cycling, and soil aeration. Despite the importance of biopores for the functions of soils and the fact that several hundreds of biopores >2 mm in diameter may occur on one square meter of soil, knowledge on the interdependence of soil properties, land-use intensity, and biopore number is still rudimentary. In this study, we investigate the linkage of the number of biopores (>2 mm i.d.) with the earthworm community, root biomass, and soil properties, including pH, water content, soil organic carbon (SOC), as well as the land-use intensity (pasture vs. cropland) as a function of the soil depth (15, 30 and 50 cm). Hypothesized causal relationships among these factors were analyzed by piecewise structural equation modelling (SEM). We found various and novel linkages between roots, earthworms, biopores, and soil properties depending on soil depth. In topsoil (at 15 cm depth), roots directly affected the number of small-sized biopores, and anecic earthworms were related to medium-sized biopores. These effects diminished with depth. We identified land-use intensity as the factor preponderating the relations between biopores, root biomass, and earthworm number in the topsoil horizons, thereby masking other interactions among variables. This appeared as high multicollinearity among variables in the SEM of the topsoil. Land-use intensity effects were found to impact the whole soil profile but decreased with soil depth. To further elucidate the single effects of soil properties on biopore-forming biota and number of biopores in the topsoil, we excluded land-use intensity as a variable in subsequent analyses. Biopores increased with soil pH and soil water content but decreased with increasing SOC. Based on our SEM analysis, we conclude that the occurrence, frequency, and persistence of biopores are the consequence of intricate interdependencies between earthworm communities, roots, and site-specific soil properties, governed by land-use intensity.

year: 2022

title: Intersecting knowledge worlds: Describing the cultural interfaces within a socioscientific issue

authors: Wagner, Brent

subjects: cultural interface

abstract: Increasing numbers of science teachers in Aotearoa New Zealand are exploring ways to incorporate indigenous mātauranga Māori (Māori knowledge and ways of knowing) into their science programmes. This article presents findings from a study that examined how senior biology students in two English-medium secondary schools incorporated mātauranga Māori alongside biological science knowledge in their discussions about the use of 1080 poison to control mammalian predators. From a social constructivist ontology and interpretivist mode of inquiry using qualitative methodology, a triadic epistemic agency conceptual framework was developed inductively and used to analyse students’ written scripts for their national school leaving qualification (NCEA), and transcriptions of individual interviews. The study took place prior to the introduction of equal status to mātauranga Māori within the New Zealand Curriculum. Deductive analysis using the Triadic identified a group of ten students who drew from both knowledge systems, with varying degrees of knowledge integration. In addition to detailed representations of the theoretical space of the locale of the learner, the findings also identified three distinctive cultural interfaces occupied by the students: conflicted, parallel, and, connected. The findings underscore the importance of enabling diverse knowledge systems in biology classes to converge. Specifically, the incorporation of mātauranga Māori alongside biological science knowledge encourages a critical stance towards knowledge claims, supports pluralist knowledge use among culturally and linguistically diverse learners and promotes critical engagement with socioscientific issues (SSI) in senior secondary school biology.

text: Intersecting knowledge worlds: Describing the cultural interfaces within a socioscientific issue Increasing numbers of science teachers in Aotearoa New Zealand are exploring ways to incorporate indigenous mātauranga Māori (Māori knowledge and ways of knowing) into their science programmes. This article presents findings from a study that examined how senior biology students in two English-medium secondary schools incorporated mātauranga Māori alongside biological science knowledge in their discussions about the use of 1080 poison to control mammalian predators. From a social constructivist ontology and interpretivist mode of inquiry using qualitative methodology, a triadic epistemic agency conceptual framework was developed inductively and used to analyse students’ written scripts for their national school leaving qualification (NCEA), and transcriptions of individual interviews. The study took place prior to the introduction of equal status to mātauranga Māori within the New Zealand Curriculum. Deductive analysis using the Triadic identified a group of ten students who drew from both knowledge systems, with varying degrees of knowledge integration. In addition to detailed representations of the theoretical space of the locale of the learner, the findings also identified three distinctive cultural interfaces occupied by the students: conflicted, parallel, and, connected. The findings underscore the importance of enabling diverse knowledge systems in biology classes to converge. Specifically, the incorporation of mātauranga Māori alongside biological science knowledge encourages a critical stance towards knowledge claims, supports pluralist knowledge use among culturally and linguistically diverse learners and promotes critical engagement with socioscientific issues (SSI) in senior secondary school biology.

year: 2026