Tension and Compression Properties of 3D-Printed Composites: Print Orientation and Strain Rate Effects.

This study examines the impact of three factors on the tensile and compressive behaviour of 3D-printed parts: (1) the addition of short carbon fibres to the nylon filament used for 3D printing, (2) the infill pattern, and (3) the speed at which the materials are strained during testing. The results show that adding carbon fibres to the nylon filament reduces variability between tests and emphasises the effect of print orientation. When the infill pattern is aligned with the direction of loading, the tensile strength of all samples increases, with the largest increase of 100% observed in the carbon fibre-reinforced samples, compared to a 37% increase in the strength of nylon samples. The carbon fibre-reinforced samples are also highly dependent on strain rate, with a 60% increase in tensile strength observed at a faster testing speed of 300 mm/min (9 min-1) compared to 5 mm/min (0.15 min-1). Nylon samples show a decrease of approximately 10% in tensile strength at the same increased speed. The compressive strength of the composite samples increases by up to 130% when the print path is parallel to the loading direction. Increases of up to 50% are observed in the compressive modulus of the composite samples at a test speed of 255 mm/min (9 min-1) compared to 1.3 mm/min (0.05 min-1). Similar trends are not seen in pure nylon samples. This study is the first to report on the variation of Poisson's ratio of short carbon fibre-reinforced 3D-printed parts. The results show increases of up to 34% and 76% in the tensile and compressive Poisson's ratios, respectively, when printing parameters are altered. The findings from this research will contribute to the design and numerical modelling of 3D-printed composites.

PIN-FORMED is required for shoot phototropism/gravitropism and facilitates meristem formation in Marchantia polymorpha.

PIN-FORMED auxin efflux transporters, a subclass of which is plasma membrane-localised, mediate a variety of land-plant developmental processes via their polar localisation and subsequent directional auxin transport. We provide the first characterisation of PIN proteins in liverworts using Marchantia polymorpha as a model system. Marchantia polymorpha possesses a single PIN-FORMED gene, whose protein product is predicted to be plasma membrane-localised, MpPIN1. To characterise MpPIN1, we created loss-of-function alleles and produced complementation lines in both M. polymorpha and Arabidopsis. In M. polymorpha, gene expression and protein localisation were tracked using an MpPIN1 transgene encoding a translationally fused fluorescent protein. Overexpression of MpPIN1 can partially complement loss of an orthologous gene, PIN-FORMED1, in Arabidopsis. In M. polymorpha, MpPIN1 influences development in numerous ways throughout its life cycle. Most notably, MpPIN1 is required to establish gemmaling dorsiventral polarity and for orthotropic growth of gametangiophore stalks, where MpPIN1 is basally polarised. PIN activity is largely conserved within land plants, with PIN-mediated auxin flow providing a flexible mechanism to organise growth. Specifically, PIN is fundamentally linked to orthotropism and to the establishment of de novo meristems, the latter potentially involving the formation of both auxin biosynthesis maxima and auxin-signalling minima.

The renaissance and enlightenment of Marchantia as a model system.

The liverwort Marchantia polymorpha has been utilized as a model for biological studies since the 18th century. In the past few decades, there has been a Renaissance in its utilization in genomic and genetic approaches to investigating physiological, developmental, and evolutionary aspects of land plant biology. The reasons for its adoption are similar to those of other genetic models, e.g. simple cultivation, ready access via its worldwide distribution, ease of crossing, facile genetics, and more recently, efficient transformation, genome editing, and genomic resources. The haploid gametophyte dominant life cycle of M. polymorpha is conducive to forward genetic approaches. The lack of ancient whole-genome duplications within liverworts facilitates reverse genetic approaches, and possibly related to this genomic stability, liverworts possess sex chromosomes that evolved in the ancestral liverwort. As a representative of one of the three bryophyte lineages, its phylogenetic position allows comparative approaches to provide insights into ancestral land plants. Given the karyotype and genome stability within liverworts, the resources developed for M. polymorpha have facilitated the development of related species as models for biological processes lacking in M. polymorpha.

Health Care Use, Costs, and Survival Trajectory of Home Mechanical Insufflation-Exsufflation.

BACKGROUND: Despite expert recommendations for use, limited evidence identifies effectiveness of mechanical insufflation-exsufflation (MI-E) in addressing respiratory morbidity and resultant health care utilization and costs for individuals with neuromuscular disorders. We examined the impact of provision of publicly funded MI-E devices on health care utilization, health care costs, and survival trajectory. METHODS: This is a retrospective pre/post cohort study linking data on prospectively recruited participants using MI-E to health administrative databases to quantify outcomes. RESULTS: We linked data from 106 participants (8 age < 15 y) and determined annualized health care use pre/post device. We found no difference in emergency department (ED) visit or hospital admission rates. Following MI-E approval, participants required fewer hospital days (median [interquartile range] [IQR]) 0 [0-9] vs 0 [0-4], P = .03). Rates of physician specialist visits also decreased (median IQR 7 [4-11] vs 4 [2-7], P < .001). Conversely, rates of home care nursing and homemaking/personal support visits increased. Following MI-E, total costs were lower for 59.4%, not different for 13.2%, and higher for 27.4%. Physician billing costs decreased whereas home care costs increased. Regression modeling identified pre-MI-E costs were the most important predictor of costs after approval. At 12 months, 23 (21.7%) participants had died. Risk of death was higher for those using more medical devices (hazard ratio 1.12, [95% CI 1.02-1.22]) in the home. CONCLUSIONS: Provision of publicly funded MI-E devices did not influence rates of ED visits or hospital admission but did shift health care utilization and costs from the acute care to community sector. Although increased community costs negated cost savings from physician billings, evidence suggests costs savings from reduced hospital days and fewer specialist visits. Risk of death was highest in individuals requiring multiple medical technologies.

Dying for change: A roadmap to refine the fish acute toxicity test after 40 years of applying a lethal endpoint.

The fish acute toxicity test (TG203; OECD, 2019) is frequently used and highly embedded in hazard and risk assessment globally. The test estimates the concentration of a chemical that kills 50% of the fish (LC50) over a 96 h exposure and is considered one of the most severe scientific procedures undertaken. Over the years, discussions at the Organisation for Economic Co-operation and Development (OECD) have resulted in changes to the test which reduce the number of fish used, as well as the development of a (potential) replacement test (TG236, OECD, 2013). However, refinement of the mortality endpoint with an earlier (moribundity) endpoint was not considered feasible during the Test Guideline's (TG) last update in 2019. Several stakeholders met at a UK-based workshop to discuss how TG203 can be refined, and identified two key opportunities to reduce fish suffering: (1) application of clinical signs that predict mortality and (2) shortening the test duration. However, several aspects need to be addressed before these refinements can be adopted. TG203 has required recording of major categories of sublethal clinical signs since its conception, with the option to record more detailed signs introduced in the 2019 update. However, in the absence of guidance, differences in identification, recording and reporting of clinical signs between technicians and laboratories is likely to have generated piecemeal data of varying quality. Harmonisation of reporting templates, and training in clinical sign recognition and recording are needed to standardise clinical sign data. This is critical to enable robust data-driven detection of clinical signs that predict mortality. Discussions suggested that the 96 h duration of TG203 cannot stand up to scientific scrutiny. Feedback and data from UK contract research organisations (CROs) conducting the test were that a substantial proportion of mortalities occur in the first 24 h. Refinement of TG203 by shortening the test duration would reduce suffering (and test failure rate) but requires a mechanism to correct new results to previous 96 h LC50 data. The actions needed to implement both refinement opportunities are summarised here within a roadmap. A shift in regulatory assessment, where the 96 h LC50 is a familiar base for decisions, will also be critical.

Education Experiences of Adult Subjects and Caregivers for Mechanical Insufflation-Exsufflation at Home.

BACKGROUND: In 2014, the Ministry of Health of Ontario, Canada, approved a program of public funding for specialist-prescribed mechanical insufflation-exsufflation (MI-E) devices for home use by individuals with neuromuscular respiratory insufficiency. Since 2014, 1,926 MI-E devices have been provided, exceeding device-use projections. Few studies describe the initial and ongoing education and support needs of home MI-E users and their family caregivers. This study aimed to explore the requirements of initial and ongoing education and support for MI-E device use, user confidence, and barriers and facilitators to home MI-E. METHODS: We conducted semi-structured interviews with new (< 6 months) and established (6-48 months) MI-E users and family caregivers. Device users rated their confidence on a numeric rating scale of 1 (not confident) to 10 (very confident). RESULTS: We recruited 14 new and 14 established MI-E users and caregivers (including 9 dyads), and we conducted 28 interviews. Both new and established users were highly confident in use of MI-E (mean ± SD scores were 8.8 ± 1.2 and 8.3 ± 2.1, respectively). Overall, the subjects were satisfied with their initial education, which consisted of a 1-2 h one-on-one session at home or in the clinic with a device demonstration and hands-on practice. Subjects viewed hands-on practice and teaching of caregivers as more beneficial than written materials. Ongoing support for device use was variable. Most subjects indicated a lack of specific follow-up, which resulted in uncertainty about whether they were using the MI-E device correctly or whether MI-E was effective. Facilitators to device utilization were ease of use, initial training, support from formal or informal caregivers, and symptom relief. Barriers were inadequate education on MI-E purpose, technique, and benefit; lack of follow-up; and inadequate knowledge of MI-E by nonspecialist health providers. CONCLUSIONS: The current model of home MI-E education at initiation meets user and caregiver needs. Better ongoing education and follow-up are needed to sustain the benefits through assessment of MI-E technique and its effectiveness.

Something ancient and something neofunctionalized-evolution of land plant hormone signaling pathways.

The evolution of land plants from a charophycean algal ancestor was accompanied by an increased diversity of regulatory networks, including signaling pathways mediating cellular communication within plants and between plants and the environment. Canonical land plant hormone signaling pathways were originally identified in angiosperms, and comparative studies in basal taxa show that they have been assembled from both ancient and newly evolved components, both before and during land plant evolution. In this review we present our current understanding, and highlight several uncertainties, of the evolution of hormone signaling pathways, focusing on the biosynthetic pathways generating putative ligands and the downstream perception and signaling pathways often leading to transcriptional responses.

Class C ARFs evolved before the origin of land plants and antagonize differentiation and developmental transitions in Marchantia polymorpha.

A plethora of developmental and physiological processes in land plants is influenced by auxin, to a large extent via alterations in gene expression by AUXIN RESPONSE FACTORs (ARFs). The canonical auxin transcriptional response system is a land plant innovation, however, charophycean algae possess orthologues of at least some classes of ARF and AUXIN/INDOLE-3-ACETIC ACID (AUX/IAA) genes, suggesting that elements of the canonical land plant system existed in an ancestral alga. We reconstructed the phylogenetic relationships between streptophyte ARF and AUX/IAA genes and functionally characterized the solitary class C ARF, MpARF3, in Marchantia polymorpha. Phylogenetic analyses indicate that multiple ARF classes, including class C ARFs, existed in an ancestral alga. Loss- and gain-of-function MpARF3 alleles result in pleiotropic effects in the gametophyte, with MpARF3 inhibiting differentiation and developmental transitions in multiple stages of the life cycle. Although loss-of-function Mparf3 and Mpmir160 alleles respond to exogenous auxin treatments, strong miR-resistant MpARF3 alleles are auxin-insensitive, suggesting that class C ARFs act in a context-dependent fashion. We conclude that two modules independently evolved to regulate a pre-existing ARF transcriptional network. Whereas the auxin-TIR1-AUX/IAA pathway evolved to repress class A/B ARF activity, miR160 evolved to repress class C ARFs in a dynamic fashion.

Efficient and Inducible Use of Artificial MicroRNAs in Marchantia polymorpha.

We describe the efficient use of artificial microRNAs (amiRs) in Marchantia polymorpha using both endogenous and heterologous primary microRNA (pri-miR) hairpin backbones. Targeting of two transcription factor genes, MpARF1 and MpRR-B, mediating different hormonal responses, demonstrated that amiRs can create specific and reproducible physiological and morphological defects, facilitating interpretation of gene function. A third amiR was designed to target a gene encoding a component of the Polycomb recessive complex 2, MpE(z), and constitutive expression of this amiR results in sporeling lethality. Adaptation of an estrogen-inducible system allowed analysis of the phenotypic effects of induction of this amiR during other stages of the life cycle. We discuss the advantages and challenges of the use of amiRs as a tool for reverse genetic analysis in M. polymorpha.

The outcome of pedicle screw instrumentation removal for ongoing low back pain following posterolateral lumbar fusion.

BACKGROUND: Our aim was to determine whether patients derived benefit from removal of pedicle screw instrumentation for axial pain without other cause using our surgical technique and patient selection. A secondary aim was to investigate factors that were associated with poorer outcomes for this procedure as well as complication rate in this cohort. METHODS: Theater records from a single spinal surgeon's practice were reviewed to identify patients that had undergone lumbar fusion for discogenic back pain with subsequent pedicle screw instrumentation removal (Expedium, DePuy Synthes) in the preceding 3 years with a minimum of 18 months follow-up. Inclusion criteria were persisting midline axial back pain with computed tomography (CT)-confirmed solid fusion with non-radicular symptoms and nil other potential causes found, e.g., infection. Case note review along with pre- and post-operative Oswestry disability index (ODI) questionnaires and visual analog scores (VAS) were assessed for all patients. Surgical technique included re-use of previous midline posterior incision and the Wiltse approach with removal of implants, confirmation of a solid fusion mass, washout and bone grafting of removal sites. RESULTS: From 50 consecutive patients who underwent removal of posterolateral instrumentation for an index elective lumbar fusion for discogenic back pain, 34 patients were identified that met the criteria with a mean follow-up of 25 months (range, 18-36 months). The VAS and ODI improved in 22/34 (65%) of participants. The mean cohort VAS score was 6.6 pre-surgery and 4.3 post-surgery (P=0.04). Preoperative and postoperative mean Oswestry disability scores were 64 and 41, respectively (P=0.05). There was a statistically significant difference in the proportion of patients with poorer compared to satisfactory outcomes with regards to compensable status, preoperative grade II opioid use and shorter time between fusion and removal procedure. Complications were one postoperative hematoma and one superficial wound infection, both of which settled without re-operation. CONCLUSIONS: Approximately two thirds of patients were satisfied with removal of instrumentation for treatment of residual low back pain (LBP) following elective lumbar fusion and recorded reduced VAS and grade II opioid use. A subset of patients remained that did not derive benefit and were associated with compensable status, preoperative grade II opioid use and a shorter time between fusion and removal procedure. A prospective cohort study with preoperative diagnostic injections and standardized imaging and microscopic techniques would strengthen future studies. However, this study suggests that removal of instrumentation is safe and provides modest benefit as a palliative procedure for a subset of patients with significant disability from chronic LBP without an underlying cause following lumbar fusion.

Extraction of bioavailable contaminants from marine sediments: an approach to reducing toxicity using adsorbent parcels.

This paper demonstrates an approach to reducing acute toxicity in marine sediments using adsorbent parcels. Acute toxicity tests were carried using the marine amphipod Corophium volutator. Marine sediments were spiked with two know contaminants tributyltin and naphthalene and then treated with adsorbent parcels containing either amberlite XAD4 or activated carbon. Results showed that both types of adsorbent parcels were effective in reducing acute toxicity, not only within spiked sediments containing naphthalene and/or tributyltin, but also in an environmental field samples form an expected contaminated site. Adsorbent parcels such as these could provide a practical approach to remediate areas of contaminated sediment within marine environments. Furthermore adsorbents can be used as an identification tool for problematic contaminants using a toxicity identification evaluation approach.

Towards a scheme of toxic equivalency factors (TEFs) for the acute toxicity of PAHs in sediment.

Toxic equivalency factors/quotients (TEF/TEQs) express the toxicity of complex mixtures. For PAHs, TEF values are available for assessing their carcinogenic potential and are expressed as benzo[a]pyrene equivalents. This study develops a similar approach for their acute toxicity in sediments. Acute toxicity (10 day EC50) values were generated using the marine amphipod Corophium volutator bioassay for twelve low molecular weight PAHs. The results ranged from 24 to > 1000 mg/Kg sediment dry weight for 4-methyldibenzothiophene and anthracene, respectively. Phenanthrene was used as the reference compound (TEF=1) and so the TEQ values derived are expressed as phenanthrene equivalents. In order to illustrate the applicability of this approach to the development of marine indicators we plotted TEQ values for acute toxicity to UK environmental monitoring data. Further work is required to validate the TEF values produced and to extend the TEQ approach to include a wider range of low molecular weight PAHs.

Justice, leader-member exchange, and job performance: are their relationships mediated by organizational culture?

The hypothesis that organizational justice is linked to leader-member exchange, which in turn affects job performance, was examined. It was predicted that two dimensions of organizational culture, employee supportiveness and attention to detail, would affect both leader-member exchange and organizational justice. Results from a sample of 75 employees of a public service organization found solid support for the predicted model. Contrary to expectations, however, the two aspects of organizational culture were found to play a mediating role: they were affected by organizational justice and in turn affected leader-member exchange. The theoretical implications of the results are discussed.