Topological superconductivity emerging in one- or two-dimensional hybrid materials is predicted as a key ingredient for quantum computing. However, not only the design of complex heterostructures is primordial for future applications but also the characterization of their electronic and structural properties at the atomic scale using the most advanced scanning probe microscopy techniques with functionalized tips. We report on the topographic signatures observed by scanning tunneling microscopy (STM) of carbon monoxide (CO) molecules, iron (Fe) atoms and sodium chloride (NaCl) islands deposited on superconducting Pb(111). For the CO adsorption a comparison with the Pb(110) substrate is demonstrated. We show a general propensity of these adsorbates to diffuse at low temperature under gentle scanning conditions. Our findings provide new insights into high-resolution probe microscopy imaging with terminated tips, decoupling atoms and molecules by NaCl islands or tip-induced lateral manipulation of iron atoms on top of the prototypical Pb(111) superconducting surface. The realization of MZMs in two dimensions has been also observed in vortex cores on a proximitized topological insulator surface [The most exciting manifestation of topological superconductivity –3 is the surface –20, in i surface ,21–22 or surface . The finSTM/AFM generally allows for a controlled repositioning of adsorbates, both by lateral and vertical manipulations –26. Atoms-wave superconductor [15It is, however, astonishing that most recent advances in manipulation experiments or contrast enhancement with functionalized tips are hitherto at their infancy, when studying a superconducting surface by STM/AFM. Although the earliest proposal for observing MZMs suggested to reposition Fe adatoms one by one with an STM tip in an one-dimensional fashion on an onductor , this stonductor –1536. Onductor 15 and Ta surface, investigated with STM at 4.8 K. We show that CO molecules on Pb(111) are hardly visible in STM images due to their high diffusion induced by the tip even at low temperature. This differs distinctly from the adsorption on Pb(110), which has also been performed. In contrast, NaCl islands and single Fe atoms are more stable. Nevertheless, a general propensity for a tip-induced displacement of these adsorbates on the Pb(111) surface can be fulfilled. We believe that our results help to identify these adsorbates and constitute an important step for future experiments to perform high-resolution STM/AFM imaging with CO-terminated tips or in the electronic decoupling of atoms and molecules from the prototypical Pb(111) superconducting surface.p ≈ 1 × 10−7 mbar for one minute. This leads to a surface coverage of about 0.1–0.3 monolayers, as we readily observed on noble metals such as Cu, Ag or Au [The Pb(111) single crystal, purchased from Mateck GmbH, was cleaned by several sputtering and annealing cycles in ultra-high vacuum (UHV). CO dosing on the cold substrate was done in the microscope chamber by increasing the pressure via a leak valve up to Ag or Au –46. IronT = 4.8 K) from Omicron GmbH in UHV (p ≈ 1 × 10−10 mbar) operated with Nanonis RC5 electronics. The sensor is a tuning fork sensor in a qPlus design [f0 ≈ 25 kHz, spring constant k ≈ 1800 N/m, quality factor Q ≈ 14000, and oscillation amplitude A ≈ 0.5 Å). The tip mounted to the qPlus sensor consists of a 25 μm-thick PtIr wire, shortened and sharpened with a focused ion beam. A clean and sharp Pb tip was then prepared at low temperature by repeated indentations into the surface. STM images were acquired in constant-current mode with the bias voltage applied to the tip. All experimental data were analysed by using Gwyddion [The experiments were performed using a low-temperature STM/AFM microscope  surface is expected to be hPb =  = 2.85 Å. Experimentally, a pristine Pb(111) sample  sample  shows, aAfter CO dosing in the microscope chamber (see section “Sample preparation”), a coverage of 0.1–0.2 monolayers is expected to adsorb on the metal surface, as observed on different noble metals –46. Figu row direction of Pb(110). The dimer-like protrusions ((D) in aPb = 4.95 Å between two Pb(110) rows (dashed lines in T) is rotated by about 16° compared to the  rows. Its length of ≈11 Å corresponds to about three Pb(110) atomic rows, the additional length of ≈1 Å is again imputed to tilted CO during tip scanning. Last, these protrusions have a slight apparent depression around them, which might be related to a strong interaction with the Pb lattice. While the D features are all aligned in the same direction, the orientation of the T features differs slightly. Both features have an apparent height of ≈0.3 Å, as extracted from the profile of Similar CO adsorption experiments were also conducted on Pb(110) . There,  rows of the Pb(110) surface, as shown by the model in  rows. The CO molecule is tilted similarly as on the Cu(110)-(2 × 1)O surface [Overall, the CO adsorption on Pb(110) shows strong similarities with CO adsorbed on Cu(110)  and Cu [T = 4.8 K, independent of the scanning conditions. As is, these islands exhibit characteristics similar to the ones on conventional metals [We next investigated the adsorption of NaCl on Pb(111) . Upon su Cu(111) . Occasio Cu(111)  or CO mol metals ,43–44. T1, Fe2 and Fe3, respectively, in the following). Note that we also do not exclude that few Fe adatoms are hydrogenated [ogenated –65.−1, the trapped Fe atom is successfully displaced over the surface. During this process, a so-called “atom manipulation image” [To confirm this assumption, we laterally manipulated single Fe adatoms with the STM tip –67 to inn image”  can be on image” ,38 or scn image” –71, sincn image” .1) and an assumed dimer (Fe2) are displayed. 1 and Fe2 aggregates to be h1 ≈ 0.4 Å and h2 ≈ 1.2 Å, respectively. As a verification, we then conducted the transfer of a single Fe atom from the Fe2 cluster to one surrounding Fe1 in order to form a new dimer. The result of such manipulation is shown in 1 and Fe2 remains identical as demonstrated by the STM profile of Using this method, we transferred single atoms between different Fe clusters. In 2 in 3). Compared to the heights of Fe1 and Fe2, the height of Fe3 is about h3 = 1.7 Å. This evolution of STM apparent heights as a function of number of atoms in small Fe clusters is in good agreement with a similar study of Fe clusters on Cu(111) [Finally, we brought by two successive tip manipulations the atoms of Fe Cu(111) .Our results report on the systematic characterization by STM of the adsorption of carbon monoxide (CO), sodium chloride (NaCl) and iron adatoms (Fe) on the superconducting Pb(111) surface at low temperature (4.7 K). We show a surprising absence of STM topographic signatures of CO molecules on Pb(111), which we impute to their high propensity of diffusing under gentle scanning conditions. In contrast, CO molecules become apparent by STM on Pb(110), since they initiate attractive dipole–dipole interactions, which support the formation of linear aggregates. Furthermore, we show that deposition of NaCl on Pb(111) leads to bilayer islands similar to literature data. Lastly, cold-temperature deposition (≤15 K) of Fe on Pb(111) leads to the adsorption of adatoms and small Fe clusters. Using tip-induced lateral manipulations, we demonstrate the exchange of Fe single atoms between these clusters and characterize the variation of apparent STM height of each cluster as a function of the number of atoms. Overall, our findings provide new basic insights regarding the way to achieve high-resolution STM/AFM imaging with functionalized tips, decoupling of atoms or molecules and tip-induced lateral manipulation of Fe atoms above the prototypical Pb(111) superconducting surface.


In this postmortem study, Asby  n = 75), vascular dementia patients (n = 22) and age-matched control subjects (n = 46), stratified according to the presence or absence of terminal systemic infection. Brain cytokine levels were measured using Mesoscale Discovery Multiplex Assays and markers of cerebrovascular function were assessed by ELISA. Multiple brain cytokines were elevated in Alzheimer’s disease and vascular dementia: IL-15 and IL-17A were maximally elevated in end-stage Alzheimer’s disease (Braak tangle stage V–VI) whereas IL-2, IL-5, IL12p40 and IL-16 were highest in intermediate Braak tangle stage III–IV disease. Several cytokines  were further raised in Alzheimer’s disease with systemic infection. Cerebral hypoperfusion—indicated by decreased MAG:PLP1 and increased vascular endothelial growth factor-A (VEGF)—and blood–brain barrier leakiness, indicated by raised levels of fibrinogen, were exacerbated in Alzheimer’s disease and vascular dementia patients, and also in non-dementia controls, with systemic infection. Amyloid-β42 level did not vary with infection or in association with brain cytokine levels. In controls, cortical perfusion declined with increasing IFN-γ, IL-2, IL-4, IL-6, IL-10, IL-12p70, IL-13 and tumour necrosis factor-α (TNF-α) but these relationships were lost with progression of Alzheimer’s disease, and with infection (even in Braak stage 0–II brains). Cortical platelet-derived growth factor receptor-β (PDGFRβ), a pericyte marker, was reduced, and endothelin-1 (EDN1) level was increased in Alzheimer’s disease; these were related to amyloid-β level and disease progression and only modestly affected by systemic infection. Our findings indicate that systemic infection alters brain cytokine levels and exacerbates cerebral hypoperfusion and blood–brain barrier leakiness associated with Alzheimer’s disease and vascular dementia, independently of the level of insoluble amyloid-β, and highlight systemic infection as an important contributor to dementia, requiring early identification and treatment in the elderly population.We studied the effects of systemic infection on brain cytokine level and cerebral vascular function in Alzheimer’s disease and vascular dementia, in superior temporal cortex (Brodmann area 22) from Alzheimer’s disease patients ( It increases the risk of coronary artery disease,In view of the contribution of vascular dysfunction to the development and progression of Alzheimer’s disease, the accelerated cognitive decline in Alzheimer’s disease patients with systemic infection, and the known effects of infection and inflammation on extracranial vascular function, we hypothesized that the deleterious influence of systemic infection in dementia, particularly in Alzheimer’s disease, is at least partly mediated by exacerbated vascular dysfunction. We have used human post-mortem brain tissue to examine whether terminal systemic infection alters cytokine levels within the brain, and biochemical markers of cerebral oxygenation, blood–brain barrier function and other measures of vascular integrity and function, at different stages of Alzheimer’s disease as indicated by Braak tangle stage, in comparison with the effects in non-dementia controls and in cases with vascular dementia and mixed vascular and Alzheimer’s disease pathology. We show that systemic infection causes neuroinflammation and cerebral vascular dysfunction even in non-dementia controls, and exacerbates these processes in Alzheimer’s disease and vascular dementia.The use of human brain tissue for this study was approved by the management committee of the South West Dementia Brain Bank (Human Tissue Authority licence number 12273) under the terms of Bristol Research Ethics Committee approval (18/SW/0029). The right cerebral hemisphere had previously been fixed in buffered formalin for 3 weeks and was used for pathological assessment. The left cerebral hemisphere had been sliced and frozen at −80°C. Most brains were dissected within 72 h of death.n = 22) or without systemic infection (n = 24); patients with Alzheimer’s disease who died with (n = 42) or without systemic infection (n = 33); and vascular dementia patients who died with (n = 7) or without systemic infection (n = 15).We studied 75 Alzheimer’s disease cases, 22 vascular dementia and 46 age-matched controls. A clinical history, which included post-mortem assessment and information on the death certificate, was used to subdivide cases according to whether systemic infection was or was not recorded as the primary cause of death in to the following groups: controls who died with  was homogenized in 500 μl RIPA buffer (Thermo Fisher Scientific) supplemented with protease inhibitor cocktail  and phosphatase inhibitor cocktail  using a PrecellysInflammatory proteins were measured on the V-Plex MSD electrochemiluminescence multi-spot assay platform  using the V-Plex MSD Proinflammatory Human Protein Panel (cat. no. K15049D) and Cytokine Human Protein Panel (cat. no. K15050D), respectively. Brain homogenate  was used for each assay according to the manufacturer’s protocol, as previously described.® automated tissue processor  as previously described.,,g for 15 min at 4°C for and then aliquoted and stored at –80°C until required. Total protein was measured for all samples by use of Total Protein Kit according to manufacturer s guidelines (Sigma Aldrich).Fresh frozen superior temporal cortex (BA22) (200 mg) was dissected and proteins were extracted in 1 ml of 1% sodium dodecyl sulphate lysis buffer, in a Precellys® Optima plate reader (BMG Labtech) after the addition of 2 N sulfuric acid. The concentration of MAG was interpolated from a serial dilution of recombinant human MAG (6.25–400 ng/ml) and adjusted for total protein level within each sample. The concentration of PLP1 was interpolated from a standard curve generated by serial dilution of recombinant human PLP1 (0.156–10 ng/ml) and adjusted for total protein. The ratio of MAG:PLP1 was calculated and is presented for each individual.The level of MAG was measured in homogenates diluted 1 in 10 in PBS, by in-house direct ELISA as previously described.,,® Optima plate reader after the addition of 2 N sulfuric acid. VEGF concentration was interpolated from serial dilutions of recombinant human VEGF (2000–31.25 pg/ml) and adjusted for total protein level.VEGF level was measured using the human VEGF-A ELISA kit (R&D Systems) as described previously.Fibrinogen level was measured in brain tissue homogenates (2 μl + 248 μl PBS) using a commercially available sandwich ELISA  as described previously.® OPTIMA plate reader (BMG Labtech). The absolute concentration of PDGFRβ was interpolated from the standard curve for each case, derived from serial dilution of recombinant PDGFRβ, and adjusted for total protein.PDGFRβ level was measured by sandwich ELISA  as described previously.® Optima plate reader (BMG Labtech). Absolute EDN1 level was interpolated from a standard curve generated by assaying serial dilutions of recombinant human EDN1 (0.343–250 pg/ml).EDN1 was measured in tissue samples by a commercial sandwich ELISA  as described previously.42 measurement were prepared as reported previously.42 in guanidine samples (diluted 1:2500 for Alzheimer’s disease samples and 1:625 for control and vascular dementia samples). Amyloid-β42 concentration was interpolated from serial dilutions of recombinant human amyloid-β42 (7.8–500 pg/ml) and corrected for sample dilution. Samples were measured in duplicate and the means calculated.Soluble and insoluble (guanidine‐extractable) fractions for amyloid-βP‐values < 0.05 were considered statistically significant.The distribution of the data and identification of potential outliers were examined for all markers assessed by examination of quantile-quantile plots (not shown). To assess the effect of Alzheimer’s disease and/or systemic infection on inflammatory brain cytokines and vascular markers, we used both one-way and two-way ANOVAs, or their non-parametric equivalents , as appropriate. Data are presented as mean ± standard error of the mean (SEM). Pearson’s or Spearman’s tests were used as appropriate to assess linear correlation. All statistical analysis was performed with SPSS version 21  and GraphPad Prism version 8 . All data within the article are linked to the MRC UK-BBN by unique numeric MRC UK-BBN identifier . FurtherAPOE ε4 homozygotes and heterozygotes in the Alzheimer’s disease cohort but with a similar distribution of these alleles between the infection and non-infection Alzheimer’s disease groups.We studied 143 cases comprising 75 Alzheimer’s disease , 22 vascular dementia/mixed  and 46 age-matched controls . The age-at-onset of dementia, disease duration and Braak tangle stage for each of the six groups is shown in Recorded causes of death in addition to dementia are listed in We performed one-way ANOVAs to assess differences in brain cytokine level between control, Alzheimer’s disease and vascular dementia groups after stratification according to the presence of infection . In contWe assessed brain cytokine levels in relation to tangle progression, a proxy marker of disease stage in Alzheimer’s disease, in a combined Alzheimer’s disease and control cohort stratified into Braak stages 0–II (BS0–II), III–IV (BSIII–IV), and V–VI (BSV–VI). IL-15 and IL-17A were significantly elevated in end-stage disease (BSV–VI) compared to BS0–II  AandB. ILAandSupplementary Fig.Supplementary Fig.2D–The MAG:PLP1 ratio was highly significantly reduced in Alzheimer’s disease and vascular dementia patients compared to age-matched controls . In a coSupplementary Fig.,Supplementary Fig. 4P = 0.008)  .Fibrinogen level within the brain, a marker of blood–brain barrier leakiness, was significantly higher in both Alzheimer’s disease and vascular dementia patients than control subjects , and sigSupplementary Fig.P < 0.05) and BSV–VI (P < 0.01) than in BS0–II (P = 0.039) but not for vascular dementia versus controls running a two-way ANOVA.The level of PDGFRβ, a protein expressed mainly by pericytesFig. 2D andn BS0–II 4D. When We have previously shown that cortical EDN1 level is elevated in Alzheimer’s disease.42 level in guanidine-HCL extracts (i.e. in the insoluble pellet fraction) was significantly increased in Alzheimer’s disease, and to a much lesser extent in vascular dementia, compared to age-matched controls (42 did not vary according to the presence of systemic infection in any of the groups and did not correlate with brain cytokine levels (data not shown).Amyloid-βcontrols . AmyloidIn the absence of infection or substantial Alzheimer’s disease tangle pathology (i.e. in BS 0–II), cortical perfusion, as indicated by MAG:PLP1, correlated negatively with the levels of several cytokines  but with few exceptions this correlation was lost with infection or progression of tangle pathology . NotablySimilarly, VEGF correlated positively with IFN-γ, IL-13 and IL-16 in BS0–II in the absence of systemic infection or substantial tangle pathology but the association was again lost in BSIII–IV and V–VI, and even sooner, in BS0–II, in cases with infection .,MAG:PLP1 and VEGF showed the expected negative correlation, as previously reported42 in controls and Alzheimer’s disease cases, but not vascular dementia   – the relationship was lost in BSV–VI cases and with systemic infection as early as BS0–II AandB. FiA BSIII–IVSupplementary Fig. 7Candnfection .APOE ε4, as was EDN1 level  (EDN1 correlated with amyloid-β < 0.01) . Systemi < 0.01) .In the absence of systemic infection, EDN1 correlated positively with the level of IL-15, IL-5, IL-1β and IL-17A in BSIII–IV or BSV–VI disease. These relationships were lost in systemic infection . TNF-α w42 level, contributes to raised brain cytokine level and vascular insufficiency, particularly cerebral hypoperfusion and blood–brain barrier leakiness in early Alzheimer’s disease. Markers of cerebral hypoperfusion and blood–brain barrier breakdown were associated with elevated levels of brain cytokines in early disease (BS0–II) but these relationships were often lost in the presence of systemic infection or disease pathology. In contrast, systemic infection only contributed modestly to disease-related changes in late-stage disease and the expression of the vasoconstrictor, EDN1, and the pericyte marker, PDGFRβ, were associated with amyloid-β42 at a later stage of disease. These data indicate that the contribution of systemic infection to brain cytokine expression and vascular insufficiency varies according to disease stage: cerebral hypoperfusion and blood–brain barrier is exacerbated by infection and is related to elevated brain cytokine expression at an early stage of Alzheimer’s disease, independently of amyloid-β, whereas pericyte loss, raised EDN1, and further blood–brain barrier breakdown, are related to amyloid-β accumulation in late-stage disease.In this post-mortem study, we show that brain cytokine levels and markers of cerebrovascular dysfunction in the superior temporal gyrus are exacerbated in the presence of terminal systemic infection in Alzheimer’s disease and vascular dementia, and in healthy age-matched controls. The influence of systemic infection on brain cytokines and vascular function varied with the stage of disease (as indicated by Braak tangle stage); brain cytokines were often highest at BSIII–IV and markers of cerebral vascular function were often impaired at this early to intermediate stage of disease. Our data indicate that systemic infection, independently of amyloid-β,in vitro,Systemic infection has long been recognized as a cause of cognitive impairment and delirium. Alzheimer’s disease patients with raised serum levels of pro-inflammatory cytokines IL-1β and TNF-α are indeed at increased risk of subsequent cognitive decline.,42 level, and amyloid-β42 levels were unchanged by infection, possibly suggesting that the impact of systemic infection of brain cytokines occurred independently of amyloid-β pathology.For many cytokines, , however, the level was highest in BSIII–IV disease, suggesting perhaps that the deleterious effects of systemic infection on the brain are likely to be maximal at an early to intermediate stage of Alzheimer’s disease. This is consistent with clinical observations,,APOE ε4,APOE ε4.,,Cerebrovascular dysfunction, associated with reduced cerebral blood flow42, EDN1, and fibrinogen, and reduced PDGFRβ.,,42 and was inversely related to the concentration of PDGFRβ and to the MAG:PLP1 ratio.42 . Indeed, in cases with no or minimal Alzheimer’s disease pathology (BS0–II), MAG:PLP1 declined and VEGF and fibrinogen increased by magnitudes similar to those in end-stage Alzheimer’s disease in control donors with terminal infection. In contrast, systemic infection appeared to have a more modest effect on EDN1 and PDGFRβ level. We previously showed that EDN1, fibrinogen and PDGFRβ are related to amyloid-β42 level.42 in Braak tangle stage III–IV and V–VI disease but not BS0–II, perhaps reflecting a threshold effect of classical Alzheimer’s disease pathological processes on the regulation of these vasoactive molecules. Together, these data indicate a complex relationship between cerebrovascular dysfunction in Alzheimer’s disease, likely to involve multiple mediators, which is both dependent and independent of amyloid-β and tau depending on stage of disease.Our recent post-mortem studies indicate that biochemical markers of pathological hypoperfusion and reduced oxygenation of the cerebral cortex in Alzheimer’s disease and vascular dementia are associated with elevated levels of amyloid-βIt is likely that cerebrovascular dysfunction associated with systemic infection is related to the systemic effects of circulating cytokines as well as localized brain-expressed pro-inflammatory cytokines. In this study, we found that in the absence of significant brain pathology or systemic infection, the expression of several brain cytokines was higher in brains that were less well perfused, i.e. with lower MAG:PLP1. The relationships were lost in the presence of systemic infection and disease pathology, suggesting that these pathological processes overwhelm the normal, relatively subtle, inflammatory responses to reductions in perfusion. Cytokines play a multifactorial role in vascular injury, mediating both vasoconstriction and dilatation , and other pro-inflammatory cytokines, such as TNF-α, upregulating the expression of the potent vasoconstrictors, Ang-II and EDN1,,,Experimental chronic cerebral hypoperfusion caused an increase in pro-inflammatory cytokines,,42 level and was only modestly affected by systemic infection. The effects of systemic infectionSystemic infection and neuroinflammation alter blood–brain barrier permeability (reviewed in Varatharaj and Galea42. PDGFRβ, a marker of pericytes, EDN1 levels, and fibrinogen level, were associated with amyloid-β42 level at a more advanced stage of disease and appeared to be only modestly affected by systemic infection. The retrospective, observational, post-mortem nature of this study imposes limitations on the interpretation of our findings, particularly insofar as the evidence is circumstantial and does not inform directly on causality or underlying mechanisms. The extent to which our findings are relevant to the progression of disease in a chronic condition with an extended prodromal phase remains to be determined. However, we know that cerebrovascular dysfunction is a strong predictor of cognitive decline and demonstrable in the early stages of dementia, perhaps independent of amyloid-β and tau, and our observations are in keeping with studies in animal models of amyloid-β accumulation which indicate that both systemic infection and cerebral hypoperfusion exacerbate disease progression and pathology. Preservation of proteins is always a concern in post-mortem studies, but to assess vascular function we have used biochemical markers that we have previously shown that to be stable for up to 72 h under simulated post-mortem conditions.,In conclusion, we have found that systemic infection is associated with elevated levels of multiple cytokines within the brain and exacerbates hypoperfusion and blood–brain barrier leakage at an early/intermediate disease stage possibly independently of amyloid-β42. Our findings suggest that systemic infection exacerbates Alzheimer’s disease mostly through additive, cytokine-mediated vascular dysfunction that is independent of the level of insoluble amyloid-β42 in the early stages of disease.In conclusion, our data are in keeping with a range of previous experimental and observational studies of the relationship between systemic inflammation and cytokine levels within the brain; the effects of cytokines on microvascular perfusion and permeability; the association of both hypoperfusion and blood–brain barrier breakdown with cognitive impairment; and the deleterious impact of systemic infection on the progression of dementia in Alzheimer’s disease. In Alzheimer’s disease, vascular dysfunction is strongly associated with the level of insoluble amyloid-βawab094_Supplementary_DataClick here for additional data file.


In response to the COVID-19 pandemic many publishers and researchers have sped up their adoption of Open Science practices, sometimes embracing them fully and sometimes partially or in a sub-optimal manner. In this article, we express concerns about the violation of some of the Open Science principles and its potential impact on the quality of research output. We provide evidence of the misuses of these principles at different stages of the scientific process. We call for a wider adoption of Open Science practices in the hope that this work will encourage a broader endorsement of Open Science principles and serve as a reminder that science should always be a rigorous process, reliable and transparent, especially in the context of a pandemic where research findings are being translated into practice even more rapidly. We provide all data and scripts at  The number of total citations in the media was even higher for preprints available on platforms dedicated to biomedical research. Out of 1,208 COVID-19 preprints found on bioRxiv, the median number of citations was 30 ([15−85]) and 444 (36.8%) of these preprints were mentioned at least once in the news. Similarly, out of 4,629 COVID-19 preprints submitted to medRxiv, the median number of citations was 12 ([6−36]) and 1,124 (24.3%) of these preprints were mentioned at least once in the news. These findings highlight the increasing trend in preprint sharing during the pandemic, raising concerns about the spread of potentially misleading and unverified data. However, Fraser et al.  OR “COVID-2019”[abstract] OR “severe acute respiratory syndrome coronavirus 2”[Supplementary Concept] OR “severe acute respiratory syndrome coronavirus 2”[abstract] OR “2019-nCoV”[abstract] OR “SARS-CoV-2”[abstract] OR “2019nCoV”[abstract] OR ((“Wuhan”[abstract] AND (“coronavirus”[MeSH Terms] OR “coronavirus”[abstract])) AND (2019/12[PDAT] OR 2020[PDAT])) The reviewing times were extracted from the data using a MATLAB script, available on the OSF repository.


The experimental results have also generated controversy related to the limitations and interpretation of the experimental approaches and ultimately their physiological relevance, particularly when considering differences between mouse, the primary animal model, and human. As a result, consensus is lacking regarding the relative importance of islet cell proliferation or progenitor differentiation and transdifferentiation of other pancreatic cell types in generating new β cells. In this review we summarize and evaluate recent experimental approaches and findings related to islet regeneration and address their relevance and potential clinical application in the fight against diabetes.In all forms of diabetes, β cell mass or function is reduced and therefore the capacity of the pancreatic cells for regeneration or replenishment is a critical need. Diverse lines of research have shown the capacity of endocrine as well as acinar, ductal and centroacinar cells to generate new β cells. Several experimental approaches using injury models, pharmacological or genetic interventions, isolation and  Insulin-producing β cells are critical for maintaining systemic glucose homeostasis. In both type 1 diabetes (T1D) and type 2 diabetes (T2D), reduced and/or inadequate β cell mass leads to insufficient insulin secretion and hyperglycemia. T1D is the result of autoimmune destruction of β cells. At clinical T1D onset, there are still remaining β cells, but the β cell mass declines further with increasing T1D duration. However, many individuals with long-standing T1D continue to secrete some insulin, indicating the persistence of some β cells. In T2D, the combination of insulin resistance due to obesity and impaired functional β cell mass leads to hyperglycemia. With increasing duration of T2D, β cell mass and function progressively declines. Thus, in both forms of diabetes, there is a great need to restore or increase β cell mass  than human islets, in which the β:α ratio is closer to 2:1. Mouse islet cells have shown greater plasticity with respect to proliferation, dedifferentiation and transdifferentiation than do human islets. As discussed below, many of the individual mitogenic pathways in β cells were identified in mouse experiments. Unfortunately, the targeting of individual pathways in human β cells was not sufficient to stimulate significant proliferation as it was in mice. Only when combinatorial approaches were employed did human β cells achieve proliferation to a level that could potentially restore β cell mass in a diabetic setting. All of these differences, among others, indicate that caution is required when translating findings from mice to humans.+ cells and migrate into the mesenchyme to form the islets that contain insulin producing β-cells  could upregulate prolactin signaling targets, they failed to stimulate human β cell proliferation  drive cell cycle entry and progression and CDK inhibitors are commonly upregulated in cells that have exited regular cell cycle. This is the case in adult β cells where CDK inhibitors such as p16feration . A majorThe most successful identification of β cells mitogens has come through studies designed to identify soluble signals that stimulate β cell proliferation. Using high throughput methods, DYRK1A inhibitors were shown to stimulate adult human β cell proliferation implicating the Calcineurin/NFAT/DYRK1A pathway as a major mitogenic pathway in β cells . At the More success in the human setting has come from studies of multiple mitogenic pathways. Combined inhibition of the Calcineurin/NFAT/DYRK1A pathway with the DYRK1A inhibitor, Harmine, and the TGFβ signaling pathway, with inhibitors such as ALK5, resulted in a synergistic increase in β cell proliferation in primary cultures and human islet xenografts . The TGFi.e., highest proliferation in the early neonatal period with a steep decline in proliferation into adulthood . Interestingly, combined loss of these genes and expression of β cell markers were observed in α cells of T1D human islets suggesting that this transdifferentiation may actually be employed in humans for β cell mass replenishment . They represent 5-10% of the total endocrine cells at birth but their numbers decline significantly postnatally , 88. Lin β cells . The ide+ cells as well as quiescent progenitors such as Dclk1+ and Stmn+ cells that can mediate complete acinar restoration following cerulein mediated acute pancreatitis  resulted in duct dedifferentiation and expansion followed by recapitulation of aspects of embryonic development to form apparently new pancreatic lobes containing islets . Regenerin vitro , 118. Hoin vitro , 120. Inin vitro –123. Extin vitro  led to din vitro . Apart fCAII) promoter to drive Cre expression, suggested that duct cells contributed to β cell neogenesis, particularly following PDL  exist in all vertebrates. CACs are rare, specialized cells situated in the middle of the acinar lobules. They are small, with minimal cytoplasm, numerous mitochondria, and long cytoplasmic extensions, some of which reach the endocrine compartment. They are contiguous with ductal cells and form a fenestrated lining on the luminal surface of each acinus , 146. Thwing PDL , 154. Thtic buds . Aldh1b1tic buds . Lineagein vitro . Similarantation . Immunofpression .Identification of additional surface markers and elucidation of self-renewing and differentiation requirements may provide the means to isolate, expand and differentiate human CACs into endocrine cells for diabetes treatment.Single cell RNA Seq has revealed that there is significant heterogeneity among pancreas differentiated cells that were once considered homogeneous stable populations , 158–160in vivo, particularly in rodents, even under physiological conditions and several mitogenic pathways have been identified that show promise when manipulated in combination , and by DK106755, DK117147, DK20593] (AP), The Leona M. and Harry B. Helmsley Charitable Trust, and the Department of Veterans Affairs (BX000666)(AP), the German Center for Diabetes Research (DZD)(82DZD00101) (AG) the German Research Foundation (DFG)(GA 2004/3-2 and IRTG 2251)(AG), and the Greek General Secreteriat of Research and Technology (GSRT) (Code: T1EDK-03532)(IS).Work in the authors’ laboratories was supported by funding provided by the National Institute of Diabetes and Digestive and Kidney Diseases [the Human Islet Research Network (HIRN; RRID : SCR_014393; 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.All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article, or claim that may be made by its manufacturer, is not guaranteed or endorsed by the publisher.


To compare intraoperative 3D fluoroscopy with a ceiling-mounted flat panel detector in plate osteosynthesis of distal radius fractures (AO/OTA 2R3C1.2) with volar locking plate systems to conventional 2D fluoroscopy for detection of insufficient fracture reduction, plate misplacement and protruding screws.Using a common volar approach on 12 cadaver forearms, total intraarticular distal radius fractures were induced, manually reduced and internally fixated with a 2.4 distal radius locking compression plate. 2D  and 3D  fluoroscopic images were taken as well as computed tomographies. Fluoroscopic images, Cone Beam CT (CBCT), 360° rotating sequences  and CT scans were co-evaluated by a specialist orthopedic surgeon and a specialist radiologist regarding quality of fracture reduction, position of plate, position of the three distal locking screws and position of the three diaphyseal screws. In reference to gold standard CT, sensitivity and specifity were analyzed.“Movie” showed highest sensitivity for detection of insufficient fracture reduction (88%). Sensitivity for detection of incorrect position of plate was 100% for CBCT and 90% for “Movie.” For intraarticular position of screws, 2D fluoroscopy and CBCT showed highest sensitivity and specifity . Regarding detection of only marginal intraarticular position of screws, sensitivity and specifity of 2D fluoroscopy reached 100% (CBCT: 100 and 83%). “Movie” showed highest sensitivity for detection of overlapping position of screws (100%). When it comes to specifity, CBCT achieved 100%. Regarding detection of only marginal overlapping position of screws, 2D fluoroscopy and “Movie” showed highest sensitivity (100%). CBCT achieved highest specifity (100%).As for assessment of quality of fracture reduction and detection of incorrect position of plate as well as overlapping position of the three diaphyseal screws CBCT and “Movie” are comparable to CT – especially when combined. Particularly sensitivity is high compared to standard 2D fluoroscopy. Distal radius fractures are amongst the most common fractures , 2. In rThe volar locking plate system was established in 2000 and has rapidly become gold standard in treatment of distal radius fractures –10. It iConventional intraoperative 2D fluoroscopy – even when performing additional views – does not detect screw misplacements reliably –21. ThusIn recent years, hybrid operating rooms have been installed widely. Originally designed for cardiac and vascular interventions, they nowadays are more and more used interdisciplinarily , 29–35. The purpose of this study is to show that, by using Allura Xper FD 20 with FlexMove in plate osteosynthesis of distal radius fractures with volar locking plate systems, insufficient fracture reduction, plate misplacement and protruding screws are more likely to be discovered intraoperatively and therefore corrected immediately than by using conventional intraoperative 2D fluoroscopy alone. The need for postoperative CT and revision surgery can be reduced.All methods were carried out in accordance with relevant guidelines and regulations. Ethics approval was obtained from the Ethics committee of the Christian-Albrecht-University Kiel, Schleswig-Holstein, Germany, Number AZ: D 485/18. All donors underwent informed consent for the use of their cadavers in the anatomical department.The surgical preparations took place at Christian-Albrechts-University, Department of Anatomy, Kiel. A total of 12 cadaver forearms were prepared. Using numbers provided by the Department of Anatomy preserved the donators’ anonymity and guaranteed the discriminability of the specimens.After having performed a common volar approach, a 22 mm Stille type chisel and a 3 kg hammer were used to conduct the osteotomy. In order to mimic a total intraarticular distal radius fracture (AO/OTA 2R3C1.2), a coronal and an intraarticular sagittal osteotomy were induced.Following manual reduction, a 2.4 distal radius locking compression plate  was used for internal fixation. Three locking screws were placed in the distal fragments and one cortical and two locking screws were inserted into the diaphysis, always using a depth gauge to measure for screw length.Fluoroscopic images in anterior-posterior and lateral planes were taken at Department of Anatomy using an Expo 8000 image intensifier . CBCT 3D-reconstruction see Fig. .Fig. 2CBquality of fracture reduction ,position of plate ,position of the three distal locking screws ; 2: intraarticular),position of the three diaphyseal screws ; 2: overlapping).2D Fluoroscopic images, CBCT reconstructions, “Movie” sequences and CT scans were co-evaluated by a specialist orthopedic surgeon  and a specialist radiologist  neither of which was involved in surgical preparations or imaging procedures. Consensus had to be achieved. In four weekly sessions 12 of the overall 48 image series were evaluated at a time in random order. To avoid recognitions, only one modality per specimen per session was assessed. Parameters to be evaluated were:Due to the relatively small number of specimens, descriptive statistics was the method of choice. If there were three assessment criteria (e.g. in plate positioning), the resulting 3 × 3 cross tabulation had to be divided into two 2 × 2 cross tabulations to allow a statistical evaluation for sensitivity and specifity. In reference to gold standard CT, true positive (TP), false negative (FN), true negative (TN) and false positive (FP) cases were listed for 2D fluoroscopy, CBCT and “Movie”. Finally, sensitivity (TP/(TP + FN)) and specifity (TN/(TN + FP)) were analyzed.“Movie” showed highest sensitivity for detection of insufficient fracture reduction (88%). All three methods achieved 100% for specifity . Regarding detection of only marginal intraarticular position of screws, sensitivity and specifity of 2D fluoroscopy reached 100% . When it comes to specifity, CBCT achieved 100%, “Movie” 94% and 2D fluoroscopy 83%. Regarding detection of only marginal overlapping position of screws, 2D fluoroscopy and “Movie” showed highest sensitivity (100%). CBCT achieved highest specifity  for the three modalities 2D fluoroscopy, “Movie” and CBCT against the gold standard CT.As far as quality of fracture reduction is concerned, “Movie” (88%) is more sensitive than 2D fluoroscopy (75%). A possible explanation could be that the sequence provides a large series of multiple planes (230 over 190°) which results in an easier detection of gaps and steps. In our experience, the “Movie” creates a deeper understanding of the fracture’s morphology in the surgeon’s imagination.As for detection of correct position of plate, CBCT is as sensitive as CT. With its sensitivity of 90%, “Movie” is not far apart from gold standard as well. We assume the 3D capabilities of all three modalities helped in the assessment.Surprisingly, there was no difference in sensitivity and specifity for detection of intraarticular position of the three distal locking screws between CBCT and 2D fluoroscopy . A possible explanation could be the fact that the two co-evaluating specialists are well trained in detecting intraarticular screws in fluoroscopic images. Furthermore, CBCT is known to be prone to metal artifacts . Like otFinally, CBCT  and “Movie”  were far more sensitive and specific in detection of position of the three diaphyseal screws than 2D fluoroscopy . Again, the 3D capabilities of CBCT and “Movie” allowed the two specialists to exactly visualize the complex and individual anatomy  of the distal radius. Maybe the fluoroscopy’s results could have been improved by taking additional planes.In both, position of the three distal locking screws and position of the three diaphyseal screws, we drew a line between “marginally intraarticular/intraarticular” and marginally overlapping/overlapping” at 2 mm. This derived from our own experience and may be subject for further debate.There are a few limitations: First, there is our setup with anatomic cadaver specimens rather than a real surgical setting. Therefore, no clinical information was obtainable. Nevertheless, this setup ensured a standard procedure especially in terms of type of fracture and surgical approach. We consent with Beisemann et al. that improved reposition and enhanced implant positioning will influence the clinical outcome favorably . BesidesAnother downside of our study was the small number of specimens. This limits the statistic power of the data and allowed descriptive statistics only. Unfortunately, there were no more specimens available at the time.The data was evaluated by a specialist orthopedic surgeon and a specialist radiologist. They both are well trained in evaluating fluoroscopic images and CT reconstructions, but to a lesser extent in the evaluation of CBCT reconstructions and “Movie” sequences. Furthermore, a specialist radiologist is usually not a member of the surgical team. Thus, the evaluation didn’t reflect the common intraoperative situation.All imaging modalities underly some subjective bias and error. Even the gold standard CT may be misinterpreted and there will always remain some uncertainty regarding the accuracy of ratings.Finally, we did not examine the potential intraoperative radiation exposure of the patient or the surgical team (including the anesthetist)  nor did As for assessment of quality of fracture reduction and detection of correct position of plate as well as position of the three diaphyseal screws CBCT and “Movie” are comparable to CT – especially when combined. Particularly sensitivity is high compared to standard 2D fluoroscopy.


After this article  was publIn Helios dataset , and representative results are included in Several statements in the article describe A2780 cell results and/or compare A2780 versus A2780/C30 results, yet many of the A2780 cell results described were not reported in the article or public dataset. The A2780 data have been added to the Fig 2C did not show image data for all doses represented in the graphs or indicate whether the NT image is from the cisplatin or from the carboplatin experiment. Image data for the full dose response series is provided in Fig 3B and 3D did not report control data showing expression levels throughout the timecourse in non-treated cells. Control data for these experiments have been provided in The Results section includes a discussion of results for serous tumors versus clear ovarian cancers, but aside from the quantitative summary results in the text these subgroup data were not reported in the article. Results to support these statements are in PLOS ONE’s Data Availability policy. The data underlying these statements are in There are five statements in the article that refer to data not shown, which is not allowed per PLOS ONE’s Editorial Board reviewed the data files and the updated figure and advised that the concerns have been satisfactorily addressed.A member of S1 Fig(A2780 data corresponding to results shown in (JPG)Click here for additional data file.S2 Fig Typical comet assay images of A2780 cells treated with cisplatin (0–150 μg/ml) for 3h or carboplatin (0–300 μg/ml) for 24h and analyzed at the end of the treatment. NT, non-treated.(JPG)Click here for additional data file.S3 Fig Typical comet assay images of A2780/C30 cells treated with cisplatin (0–150 μg/ml) for 3h or carboplatin (0–300 μg/ml) for 24h and analyzed at the end of the treatment. NT, non-treated.(JPG)Click here for additional data file.S4 File(DOC)Click here for additional data file.S5 File(DOC)Click here for additional data file.S6 File(ZIP)Click here for additional data file.S7 File(ZIP)Click here for additional data file.


It has been suggested that differences in specific leaf area (SLA), which potentially reflects variation in internal CO2 diffusion, can impact leaf δ13C. Furthermore, although it is known that water movement is important for elemental uptake, it is not clear how manipulation of transpiration for increased water-use efficiency may impact nutrient accumulation. Here, we characterize the genetic architecture of leaf δ13C and test its relationship to SLA and the ionome in five populations of maize. Five significant QTL for leaf δ13C were identified, including novel QTL as well as some that were identified previously in maize kernels. One of the QTL regions contains an Erecta-like gene, the ortholog of which has been shown to regulate transpiration efficiency and leaf δ13C in Arabidopsis. QTL for δ13C were located in the same general chromosome region, but slightly shifted, when comparing data from two different years. Our data does not support a relationship between δ13C and SLA, and of the 19 elements analyzed, only a weak correlation between molybdenum and δ13C was detected. Together these data add to the genetic understanding of leaf δ13C in maize and suggest that improvements to plant water use may be possible without significantly influencing elemental homeostasis.With increased demand on freshwater resources for agriculture, it is imperative that more water-use efficient crops are developed. Leaf stable carbon isotope composition, δ Characterization of the genetic architecture of leaf δ13C will provide a better context for understanding what drives δ13C, which will allow breeders to utilize this trait in crop improvement.There have been several previous studies that have used quantitative genetics to investigate δeaf δ13C . The lacAll experiments were planted at the University of Illinois Crop Sciences Research Farm, Urbana, IL, USA and were subject to natural conditions without supplemental irrigation. Plants did not show signs of stress prior to sample collection. Weather data collected less than 1.5 km from the field site can be found in Supplementary Table S5 . NAM RIL13C analysis from the 2015 NAM RIL populations were collected 6 weeks after planting (approximately V9) as follows. A rectangular piece of tissue approximately 7.5 cm × 5 cm was taken from the middle of the leaf blade (excluding the midrib) of the uppermost fully expanded leaf from four plants in each plot. Samples were placed in a coin envelope and dried at 65°C for at least 7 days. After drying, four-hole punches (each 0.058532 cm2) were taken and placed in a 6 mm × 4 mm tin capsules (OEA Laboratories # C11350.500P) for analysis using a Delta PlusXP (Washington State University) isotope ratio mass spectrometer. Leaf samples for SLA measurements were collected from four plants in each of the plots  using a 1.6 cm diameter cork borer. Leaf discs were dried at 65°C for at least 7 days prior to weighing on an analytical balance (Model MS204S). SLA was calculated as the area of a leaf disc divided by its dry weight. These same leaf discs were then used for ionomics analyses as described in 13C analysis from the GWAS panel and the 2019 NAM RIL population were collected at approximately V10 (6–7 weeks after planting) using the hole punch method and processed as described previously .All analyses were completed using custom scripts (available upon request) and statistical packages in R . A mixedP-values for multiple testing. The correlation matrix was visualized using pairs.panel in the R package “psych” ). The previously identified marker was added to the model and re-run in a stepwise regression procedure. The final model included all identified QTL. Significance thresholds were determined by 200 permutations and alpha was set at 0.05. All analysis was completed using custom scripts in R ). All 836 marker-by-family terms were tested. SNP effects were nested in families to reflect the potential for unique QTL allele effects within each family. Significance thresholds were determined using 1000 permutations for each family independently and alpha was set at 0.05. The lowest resulting P-value was recorded for each permutation.The analysis was completed using HapMapv2 . All phenotypic datasets were quality controlled for complete technical replicates and availability of genotypic data. A list of all genotypes used in each analysis is provided in Supplementary Tables S1–S4 and have been uploaded to figshare. Briefly, the δ13C analysis was completed with 640 RILs; including 156 CML103 RILs, 160 CML333 RILs, 159 NC358 RILs, and 165 Tx303 RILs (Supplementary Table S1). The element analysis was completed using a total of 704 RILs; including 175 CML103 RILs, 181 CML333 RILs, 175 NC358 RILs, and 173 Tx303 RILs (Supplementary Table S1). The SLA analysis used a total of 683 RILs; including 172 CML103 RILs, 176 CML333 RILs, 168 NC358 RILs, and 167 Tx303 RILs (Supplementary Table S1). The Joint linkage analysis was completed using a total of 624 RILs; including 154 CML103 RILs, 159 CML333 RILs, 151 NC358 RILs, and 160 Tx303 RILs (Supplementary Table S2). Supplementary Table S3 lists the 413 lines used in the GWAS of leaf δ13C. Supplementary Table S4 includes the QTL coordinates identified in the elemental QTL analyses. Supplementary Figure S1 shows the distribution of leaf δ13C for each of the NAM RIL families. Supplementary Figure S2 presents the correlation matrix for the elemental analysis, and Supplementary Figure S3 shows the chromosomes where significant QTL were identified for each element. Supplementary Figure S4 is the LOD plot from the GWAS mapping of leaf δ13C. Supplementary material is available at figshare: https://doi.org/10.25387/g3.14114234.Genotypic datasets were downloaded from Panzea CyVerse iPlant Data Storage Commons (13C than B73 (P < 0.05), when grown as replicated controls among the RILs. However, the Tx303 and NC358 parental lines were not found to be significantly different from B73. Transgressive segregation was observed in all four RIL families .The RIL families generated from four NAM founder lines  were grown for linkage analysis. Consistent with previous studies, both the CML103 and CML333 parent lines had a significantly less negative leaf δ13C in the NAM RIL families CML103, CML333, and Tx303 but not in NC358 . In addition to testing for a correlation with leaf δ13C, QTL mapping was performed for SLA to identify any possible overlaps with genomic regions identified for leaf δ13C. Mapping of SLA in the four RIL families identified two significant QTL. In the CML103 RIL family, a QTL was identified on chromosome 5 at 86.1 Mb and in the Tx303 RIL family a QTL on chromosome 9 at 107.8 Mb. Neither of the SLA QTL identified overlapped with QTL for leaf δ13C (SLA was used as a proxy trait to test for a relationship between leaf thickness and leaf δeaf δ13C .r > ± 0.7) were identified with δ13C. However, there was a weak but significant correlation  between leaf δ13C and Mo , but no strong correlations  increased in later steps of the model. However, no new QTL was identified with this approach.A joint linkage analysis was performed for leaf δ3, and 5  as in thOne of the biparental mapping populations was grown in a second field trial to investigate the repeatability of the QTL between years. The CML103 RIL family had a significant QTL on chromosome 5 in both years . The pea13C using a biparental mapping strategy .Once significant QTL intervals were identified for leaf δstrategy , we perf13C has a moderately high heritability in maize . However, er1 was located outside of the 1 LOD interval of the 2019 chromosome 5 QTL. Furthermore, mapping of BLUE further shifted the chromosome 5 QTL peak away from er1 (er1 in variation of leaf δ13C. This would be an interesting area of future research given that this gene was found to effect δ13C in Arabidopsis by changing stomatal density (Although the QTL analyses presented here do not provide gene-level resolution, we were able to look for candidate genes within the intervals. The 2015 chromosome 5 QTL includes an Erecta-like gene (from er1 . Unfortu density . However13C can be controlled by different factors depending on the genetic background. Furthermore, if in fact leaf δ13C is controlled by many small-effect QTL, this may explain why the GWAS did not identify any significant SNP associations with leaf δ13C. Identifying rare alleles with small to moderate effect size is a known weakness of the GWAS method (13C would allow future analyses to move beyond single marker tests and instead look at SNPs in genes representing a particular pathway or process that could be collectively significant. This approach was successfully used to study maize lipid biosynthesis (The linkage analyses using biparental mapping populations identified several significant QTL, but none of the single-family QTL were independently identified in more than one family . This re2 into mesophyll cells is a potential source of variation in leaf δ13C, which could be linked to stomatal density or leaf thickness. Previous work in maize has shown that stomatal density is not correlated with leaf δ13C in a small diversity panel of maize (13C in maize, but in rice δ13C and SLA have shared QTL (13C in four RIL families, and no correlation was observed. Likewise, a comparison of the QTL analyses showed no overlapping regions for SLA and those mapped for leaf δ13C. This result suggests two possibilities. First, it is possible that differences in SLA observed in these populations are not due to leaf thickness, but rather composition. Identifying the causative genes underlying the QTL would give insight into the mechanism. A second possibility is that leaf anatomical traits other than leaf thickness influence leaf δ13C. A variety of anatomical traits could affect δ13C and would not be directly captured by measurement of SLA, such as stomatal ratios, interveinal distance, mesophyll surface area, chloroplast placement, and cell wall thickness. Variation in anatomical traits has the potential to influence CO2 diffusion as well as bundle sheath leakiness to CO2, both of which could influence leaf δ13C.The diffusion of COof maize . SLA has13C was Molybdenum. Molybdenum is required for several vital biological processes related to nitrogen and water (13C and molybdenum, which is contrary to expectation given that an increase in δ13C signifies a decrease in WUE. Overall, it is encouraging that the majority of elements sampled were not associated with δ13C. This suggests that breeding for leaf δ13C as a means to reduce transpiration would be unlikely to result in plants with nutrient uptake deficiencies.With our data, we were able to indirectly test the relationship between nutrient uptake and transpiration. If reducing transpiration limits nutrient uptake, transpiration efficiency as a trait for increasing WUE would have limited application. The 19 elements tested here were previously reported to have narrow-sense heritabilities ranging from 0.11 to 0.66 . The onlnd water . Because13C and its relationship to SLA and nutrient accumulation, the QTL mapping of the analyzed elements was an interesting biproduct. Mapping the leaf ionome of the four RIL families resulted in many significant QTL, including some overlapping intervals for different elements. Multi element QTLs are common, and are thought to be due to loci affecting processes such as the acidification of the rhizosphere or altering the permeability of the casparian strip (Although the main focus of this study was to investigate leaf δan strip . Interes


Scaling down material synthesis to crystalline structures only few atoms in size and precisely positioned in device configurations remains highly challenging, but is crucial for new applications e.g., in quantum computing. We propose to use the sidewall facets of larger III–V semiconductor nanowires (NWs), with controllable axial stacking of different crystal phases, as templates for site-selective growth of ordered few atoms 1D and 2D structures. We demonstrate this concept of self-selective growth by Bi deposition and incorporation into the surfaces of GaAs NWs to form GaBi structures. Using low temperature scanning tunneling microscopy (STM), we observe the crystal structure dependent self-selective growth process, where ordered 1D GaBi atomic chains and 2D islands are alloyed into surfaces of the wurtzite (Wz)  Site-selected crystal material synthesis at the atomic scale has been a long-standing challenge. Here the authors use nanowire crystal phase heterostructures as templates for self-selective growth of one- and two-dimensional GaBi nanostructures, which allows versatile design with atomic-scale precision. In this way, e.g., single atom transistors based on P doping atoms in Si have been demonstrated3, and quantum dots (QDs) formed of chains of In atoms on an InAs surface have been studied4. While these approaches give fascinating insight into quantum processes, they are not suitable for large-scale industrial device processing, and demanding to implement even for scientific purposes. Scalable approaches, on the other hand, are typically based on complex processing recipes using lithography and etching steps5. Many impressive examples can be found, including InAs nanoribbons based on multi-step epitaxial lift-off and overgrowth demonstrating high-performance transistor behavior6, or self-assembled QDs aligned in chains by substrate strain engineering7 or cleaved-edge overgrowth8, aiming for optoelectronic application. In these approaches, however, the lateral positioning is limited by the spatial resolution of the lithographic processes, and the nanostructures formed on top of the substrates are at least several nm high and contain millions of atoms, thus being far from atomic-scale precision, which has to be the ultimate goal for quantum devices9. 2D small islands and 1D chains of atoms have been grown on macroscopically homogeneous group IV semiconductor surfaces12. However, formation of such nanostructures with precise spatial control on III–V or other compound semiconductor heterostructures remains an open challenge.Site-selected formation of semiconductor nanostructures has so far mainly been realized by two types of approaches: Nanostructures with full control over the spatial position of each atom have been produced by means of atom manipulation13 as templates for site-selected overgrowth, after mechanical transfer of the NWs from the growth sample onto a suitable substrate14. Such NW heterostructures can be grown with atomically sharp transitions between cubic zincblende (Zb) and hexagonal Wz segments and tunable length of the corresponding segments, providing the desired spatial precision and control. The wires themselves can be placed intentionally in devices after or even during growth15. Interestingly, the various surface facets of both Zb and Wz crystal phase18 of III–V semiconductor NWs offer an extra degree of freedom for surface-related growth phenomena. Previous STM studies have successfully resolved the atomic structure of these facets and the Wz/Zb interface on GaAs19 and other III–V20 NWs, showing that the Zb {110}, Wz 18.In an alternative approach, we use side facets of crystal phase engineered III–V semiconductor NWs22. However, III–V alloys with a high Bi content (>20% of the group-V atoms) could not yet be realized24, and especially GaBi has been considered as thermodynamically unstable27, while Bi is also known to act as surfactant in the GaAs/InAs material system28. Alternatively, one can consider to deposit Bi atoms onto the surfaces of binary III–V compounds and thus obtain a high Bi concentration at the surface. So far, Bi deposition on the non-polar GaAs(110) surface was reported to result in the growth of terraces and islands of pure Bi29, while after Bi deposition on polar surfaces such as GaAs(001) or {111} mainly Bi-terminated surface reconstructions were observed , which should still be detectable with STM down to at least 3 bilayers34, however, we find no such protrusions. These results suggest Bi-incorporation on GaAs NWs after growth as a successful approach for achieving local GaBi formation, which has been considered unstable in bulk27, confined within the top most atomic layer.Bi atoms surface incorporation can be found on both Zb and Wz facets, as shown in Fig. 35 and around vacancies. Furthermore, Bi atoms will have more freedom for strain relaxation when incorporating on the step edges.On the {110}-type facets, Bi atoms are found in a random distribution in the middle of the terraces, as confirmed by autocorrelation analysis  during Bi deposition, only metallic Bi clusters will be formed on the surface. On the contrary, if the sample temperature is too high , Bi atoms tend to evaporate directly when landing on the GaAs surface, thus resulting in a very low Bi deposition and incorporation rate. Synchrotron based nano-focused X-ray photoelectron spectroscopy (XPS) has been performed to study the Bi incorporation process as well, as shown in Supplementary Fig. We conclude that the crystal-phase selective Bi incorporation on GaAs NWs is a result of the interplay between the atomic morphology and the surface energy of the different NW facets. In our model, the self-selected diffusion paths and incorporation sites for Bi atoms are determined by the surface energy and the next nearest neighbor geometry. By carefully tailoring Wz/Zb heterostructure NWs, unique 2D and 1D nanostructures of pure GaBi which are fully confined to one atomic layer can be achieved, growing self-selectively on the NW −2 and nominal diameters of 30, 50, and 70 nm were deposited onto GaAs30 in order to enable the particle-assisted NW growth mode. After annealing the substrates at a set temperature of 630 °C for 10 min in an AsH3/H2 atmosphere, a step necessary to remove surface oxides and allow for a proper surface conditioning, the temperature was set to 550 °C for NW growth. The precursor materials trimethylgallium (TMGa) and arsine (AsH3) were set to molar fractions of χTMGa = 1.9 × 10−5 as well as χAsH3 = 4.5 × 10−5 and 4.4 × 10−3 for Wz and Zb conditions, respectively, and, after a temperature stabilization step, introduced into the reactor chamber in order to initialize NW growth. Heterostructured NWs consisting of alternating segments of Wz and Zb, specifically designed for the experiments, were engineered by only switching the group-V precursor flow. For detailed information about the growth of sharp crystal structure interfaces in III–V NW systems, the reader is kindly referred to ref. 38 and references therein. In the presented work the focus was on two types of heterostructured GaAs NWs. Type I had Wz facets of a length of around 43 nm with many small terraces on the NW facets of typically 2–8 nm resulting in a high density of atomic surface steps. Type II sample instead had WZ facets of a length of around 35 nm with terraces typically larger than 8 nm, corresponding to significantly fewer atomic surface steps. Here the terrace size refers to the length of a surface terrace along the direction perpendicular to the NW growth direction. Scanning electron microscopy (SEM) for morphological and structural characterization was carried out in standard and transmission imaging mode in dedicated microscopes (Zeiss Leo Gemini 1560 and Hitachi SU 8010).GaAs NWs were prepared by metal-organic vapor phase epitaxy (MOVPE) using a 3 × 2” Aixtron close-coupled showerhead reactor (CCS) at a total reactor flow of 8 slm, a total reactor pressure of 100 mbar, and hydrogen as carrier gas. Au aerosol particles with a total areal density of 1 μm14, and loaded into the STM chamber with a base pressure of less than 1 × 10−10 mbar. After this, the samples were annealed to 500 °C for 1–3 h in an atomic hydrogen beam, provided by a thermal cracker (MBE Komponenten) operating at a hydrogen chamber pressure of 2 × 10−6 mbar, in order to remove the native oxide which forms on the NW surfaces upon transport in air. This procedure has been proven before to be a suitable way to clean III–V NWs18. The cleaned NW surfaces were studied using an Omicron low-temperature (LT) STM, operated in constant current mode at 5 K. Chosen values of sample bias, VT, and tunneling current, IT, are indicated in the figure captions. Tungsten tips were employed that had been electrochemically etched and afterward cleaned in UHV by electron bombardment. Significant tip-induced band bending effects were observed; due to dopant freeze-out, relatively high sample bias was required upon STM imaging. The Bi deposition was performed on the oxide-free sample, making use of a multi-chamber UHV cluster tool without breaking vacuum, using an effusion cell with a PBN crucible at a sample temperature of 250 °C. The temperature of the Bi cell was set to 420 °C (450 °C for the sample with the larger surface terraces), resulting in an atomic Bi-flux of 4.0 (7.8) × 1013 atoms cm−2 min−1. The deposition time was 363 s (187 s), corresponding to a deposited Bi amount of 0.5 ML (for both samples).For STM imaging, the NWs were broken off their growth substrates, mechanically transferred onto n-type GaAs Supplementary InformationPeer Review File


Solid-state welding offers distinct advantages for joining reactive materials, such as magnesium (Mg) and its alloys. This study investigates the effect of linear friction welding (LFW) on the microstructure and mechanical properties of cast AZ91 (Mg–9Al–1Zn) and AZ91–2Ca alloys, which (to the best knowledge of the authors) has not been reported in the literature. Using the same set of LFW process parameters, similar alloy joints—namely, AZ91/AZ91 and AZ91–2Ca/AZ91–2Ca—were manufactured and found to exhibit integral bonding at the interface without defects, such as porosity, inclusions, and/or cracking. Microstructural examination of the AZ91/AZ91 joint revealed dissolution of the Al-rich second phase in the weld zone, while the Mn containing phases remained and were refined. In the AZ91–2Ca/AZ91–2Ca joint, the weld zone retained Ca- and Mn-rich phases, which were also refined due to the LFW process. In both joint types, extensive recrystallization occurred during LFW, as evidenced by the refinement of the grains from ~1000 µm in the base materials to roughly 2–6 µm in the weld zone. These microstructural changes in the AZ91/AZ91 and AZ91–2Ca/AZ91–2Ca joints increased the hardness in the weld zone by 32%. The use of digital image correlation for strain mapping along the sample gage length during tensile testing revealed that the local strains were about 50% lower in the weld zone relative to the AZ91 and AZ91–2Ca base materials. This points to the higher strength of the weld zone in the AZ91/AZ91 and AZ91–2Ca/AZ91–2Ca joints due to the fine grain size, second phase refinement, and strong basal texture. Final fracture during tensile loading of both joints occurred in the base materials. Certain drawbacks, such as the perceived ignition risk, have traditionally hindered the widespread use of Mg in commercial aircraft. Solid Mg reacts readily with oxygen, forming a magnesium oxide (MgO) scale that is fairly compact and protective up to 475 °C [Weight saving in commercial aircraft  is one oe change . Magnesinium ρ = .5 g/cm3.It is known that the ignition tendency of Mg is composition dependent. Mg alloys with alkaline earth ,7 and raMg alloy castings have a great potential to increase the buy-to-fly ratio of aerospace components close to 1 . Moreover, the buy-to-flight ratio of aerospace assemblies can also be minimized using welding techniques instead of mechanical fastening . HoweverTo address these challenges, solid-state joining techniques, such as friction stir welding (FSW), have been proposed to join Mg alloys ,24,25. DConsidering this, the present work was undertaken to comprehensively study the effectiveness of LFW for two cast Mg alloys of importance to the aerospace and automotive industries: Mg–9Al–1Zn–0.3Mn (AZ91) and AZ91 + 2 wt.% Ca (AZ91–2Ca). It is noteworthy that Ca was selected as a compositional addition in this study due to its positive effect in increasing the ignition resistance of AZ91, as well as improving the corrosion ,30,31,326/CO2 atmosphere. The pure Mg used to synthesize the alloys was supplied by Magnesium Elektron Limited  with a purity of 99.9%, while the Mg-30 wt.% Ca and Mg-0.75 wt.% Mn master alloys were provided by Timminco Metals . The pure Al and Zn pellets, used as additions, were supplied by Alfa Aesar . First, pure Mg was melted at 690 °C; then, the Mg–Mn master alloy, Mg–Ca master alloy, and pure elements were added consecutively in that order. The molten alloy was stirred after each addition using a graphite rod to homogenize the melt; then, the alloy was held for 10 min to ensure complete dissolution, followed by pouring at 730 °C into an H13 tool-steel mold preheated at 400 °C and coated with boron nitride to assist casting ejection. The resulting cast plates were 12.5 cm × 10 cm with a thickness of 2.5 cm. The composition of the AZ91–2Ca alloy is presented in The AZ91–2Ca alloy, used in this study, was synthesized in McGill’s Light Metals Research Laboratory . The alloy was melted using a Norax Induction Furnace (20 kW/5 kHz)  using a graphite crucible under a protective SFCoupons for LFW—12.0 mm (D) × 24.5 mm (W) × 33.0 mm (L)—were machined with a tolerance of 0.02 mm from the cast plates of AZ91 and AZ91–2Ca. The faying surfaces of the coupons were lightly sanded at the joint interface using 320-grit sandpaper and then cleaned with ethanol just before placing them in the LFW sample holder. The equipment used for LFW was an MTS LFW process development system (PDS) at the National Research Council Canada’s Aerospace Manufacturing Technology Center , which consisted of two hydraulic actuators: an in-plane actuator oscillating the lower coupon in the horizontal direction and a forge actuator applying a downward load through the top stationary coupon. More details about the technical specifications of the MTS LFW PDS system and the LFW process are provided in .The LFW experiments were conducted in air (without shielding gas protection) at an ambient temperature of 22 °C using a pressure of 50 MPa, a frequency of 50 Hz, and an oscillating amplitude of 2 mm. During LFW, temperature measurements were made using a FLIR SC8300HD thermal camera . To assure the accuracy of the surface temperature measurements, the thermal camera used in this study was blackbody calibrated to NIST traceability. However, having calibrated the thermal camera on a blackbody source (or perfect radiator), the ability to measure the temperature on the interface of the AZ91/AZ91 and AZ91–2Ca/AZ91–2Ca joints depends directly on the actual surface emissivity within the process temperature range. Hence, the methodology used to determine the average emissivity value involved heating the AZ91 and AZ91–2Ca coupons to 500 °C in a furnace and monitoring their actual temperature using a thermocouple attached to their surface. Then, the surface temperatures on the AZ91 and AZ91–2Ca coupons were also measured with the thermal camera. The emissivity was adjusted by matching the surface temperature measurements from the thermal camera to that of the contact thermocouple during cooling from 500 to 250 °C. This resulted in an average emissivity of 0.58.After LFW, metallographic and tensile test samples were extracted from the AZ91/AZ91 and AZ91–2Ca/AZ91–2Ca welds, as illustrated in Vickers microhardness testing across transverse weld sections  was performed on polished (mirror finished) surfaces of the metallography samples using a Struers DuraScan80 hardness tester  equipped with a motorized x-y stage and a built-in microprocessor for automated measurement of hardness values. Hardness profiles were determined based on the average of three measurements for each point with a load of 500 g and a dwell period of 15 s at an indent spacing of 0.2 mm. The minimum test point separation distance for all measurements was at least three times the diagonal measurement of the indent to avoid any potential effect of strain fields from the neighboring indents.® . Prior to testing, one side of the tensile sample was marked with two pieces of retroreflective tape to define the gage length for the laser extensometer measurements during testing. On the opposite side, the surface of the tensile sample was first painted with a white background and then a high-contrast random pattern of black speckles was applied. As the functionality of the Aramis® system is sensitive to the quality of this speckle pattern, verification of pattern recognition was performed before tensile testing to ensure proper strain recording along the entire gage length, as described in [−1. To obtain the global stress–strain curves and related mechanical properties, the load data collected from the tensile testing machine were used to calculate the engineering stresses during the test, while the related strains were calculated from the displacement obtained from the laser extensometer. The tensile properties evaluated in this work included the yield strength (YS), ultimate tensile strength (UTS), and elongation (EL) for each sample. Three tensile samples for each weld combination were tested to obtain the average stress–strain response.Guided by the principles given in ASTM E8M-16a , standarribed in ,39. TensThe stereoscopic images in 1712, also known as the β-phase. For the AZ91/AZ91 linear friction weld, both phases were present in the base material and the central weld zone. For AZ91–2Ca/AZ91–2Ca weld, however, no significant peaks belonging to the β–Mg1712 phase were observed in the central weld zone, though they were present in the XRD spectrum of the AZ91–2Ca alloy.Other phases with a smaller volume fraction may be present, but were not detectable via XRD. FactSage-FTlite™ simulations were performed to predict the additional phases that may form given the composition of the alloys. Scheil–Gulliver calculations were utilized wherein full mixing in the liquid and no diffusion in the solid were considered; this calculation simulated the fast solidification  experien1712—that was also observed through XRD—along with Mn-rich smaller particles, previously identified as Al8Mn5 in the literature concerning AZ91 [2Ca phase in the form of plates connected to the network of the β–Mg1712 phase; previously, the presence of the Al2Ca phase has been reported in the literature involving Ca addition to AZ91 [65–φ phase predicted in the AZ91–2Ca alloy that was not observed via SEM. Its composition is similar to the more predominant β–Mg1712 phase; hence it may coexist in small quantities with this phase at the interdendritic regions.ing AZ91 . Additio1712 particles became progressively smaller when traversing from the base material (bottom) towards the central weld zone (top). Thus, this central weld zone 12 particles, along with some fragmented Al8Mn5 stringers that were oriented parallel to the welding direction and remained in the microstructure despite the deformation process. A closer look at the β–Mg1712 particles 12 phase in the base material, but were dispersed throughout the matrix in the central weld zone.The AZ91/AZ91 weld region consisted of a central weld zone with an abrupt transition to the base material, as shown in eld zone b containarticles c revealearticles f and Zn articles g distrib2Ca and the Al8Mn5 predicted by the FactSage-FTlite™ calculations. Similar microstructural phases and particles have been observed in Ca containing Mg–Al alloys joined via FSW and friction stir processing (FSP), including studies on AZ91–1Ca (Mg–9Al–1Zn–1Ca) [2Ca and refined or dissolved β–Mg17Al12, similar to our observations on the AZ91/AZ91 and AZ91–2Ca/AZ91–2Ca welds joined via LFW.Similar to the AZ91/AZ91 weld, the AZ91–2Ca/AZ91–2Ca weld also indicated an abrupt transition between the base material and the central weld zone a. Howeve1Zn–1Ca) , AMX602 1Zn–1Ca) , and AZX1Zn–1Ca) . SpecifiGrain structures and the crystallographic micro-texture of the Mg alloys were analyzed via EBSD. Both cast alloys displayed large grains (>500 µm) with thick dendritic arms . A rando0.5) and AZ91–2Ca (66.3 ± 3.1 HV0.5) base materials. In addition, the apparent size of the higher hardness weld region in the AZ91/AZ91 weld was observed to be larger than that in the AZ91–2Ca/AZ91–2Ca weld, which is in agreement with microstructural  evolutions, as reported above. However, though the transition from the central weld zone to the base materials was observed microscopically to be rather abrupt, the hardness maps of AZ91/AZ91 and AZ91–2Ca/AZ91–2Ca welds suggest minor hardening in a heat-affected zone  on either side of the central weld zone. In addition, fluctuations in the hardness measurements were noticed, especially in the base material regions, which may be attributed to the presence of large intermetallic particles and casting defects that affect the micro-indentation results.Both Vickers microhardness and static tensile testing were used to gauge the impact of the LFW process on the mechanical properties of the AZ91/AZ91 and AZ91–2Ca/AZ91–2Ca welds. The average Vickers micro-hardness values for the base materials and the central weld zones are shown in 2Ca phase instead of the β–Mg1712 phase, which led to early fracture during tensile loading. The yield strength of the AZ91/AZ91 and AZ91–2Ca/AZ91–2Ca welds was similar or higher than the as-cast base materials . Tensile fracture of both the AZ91/AZ91 and AZ91–2Ca/AZ91–2Ca welds occurred outside the weld region, close to the edge of the 25 mm gage length region, indicating that the welded region is stronger than the base materials, which agrees with the hardness data in The mechanical properties of the AZ91/AZ91 and AZ91–2Ca/AZ91–2Ca welds, obtained through tensile testing, are shown in ®. These maps demonstrate that the highest local strains right before fracture are in the base material region and not within the weld region. In addition, locally, the maximum strain value in the AZ91 base material was 3.7%, which is nearly twice the global strain of 2% for the AZ91/AZ91 weld. Similarly, the maximum value of the local strain in the AZ91–2Ca base material was nearly 1.1%, about 10% higher than the global strain of 1% for the AZ91–2Ca/AZ91–2Ca weld. By contrast, the local strains in the central weld region were considerably lower (~50%), between 1.2 and 1.6% in the AZ91/AZ91 weld and 0.5 and 0.7 in the AZ91–2Ca/AZ91–2Ca weld. This further highlights the higher strength of the central weld region compared to the cast Mg base materials.From the thermal camera readings given in Previous work has suggested that the ejection of a larger flash from the weld may lead to increased heat dissipation and lower welding temperatures . The steWithin the flash, there was also a clear interface between the two sides/coupons of the AZ91/AZ91 and AZ91–2Ca/AZ91–2Ca welds . In partMicrostructures: From the thermal history during LFW of the Mg alloys, the weld regions reached average temperatures of 351 °C (AZ91/AZ91) and 407 °C (AZ91–2Ca/AZ91–2Ca). The room temperature microstructures in the weld region after LFW are expected to result from rapid cooling (quenching) of the phase constituents existing at these elevated temperatures. AZ91/AZ91 weld: The simulations indicate that the amount of the β–Mg17Al12 phase in the AZ91 alloy reduces from the room temperature value of ~11.9 wt% in an as-cast structure to 3.3 wt% in the weld region at the maximum average temperature of 351 °C recorded during LFW  fraction at 351 °C relative to that in an as-cast AZ91 structure at room temperature.ring LFW . In addiAZ91–2Ca/AZ91–2Ca weld: For the AZ91–2Ca/AZ91–2Ca weld simulation, no β–Mg17Al12 phase particles remain at the maximum average temperature of 407 °C recorded during LFW. This prediction agrees with the absence of the β–Mg17Al12 phase particles in the microscopic/EDS observations of AZ91–2Ca/AZ91–2Ca weld region (2Ca particles remains unchanged (as it only disperses) at ~4.6 wt%, which also agrees with the as-welded microstructures given in 8Mn5 particles dissolve in the AZ91–2Ca/AZ91–2Ca weld and, instead, the ternary Mn2CaAl10 phase is present. This phase transformation is the only feature that does not completely agree with the observed EDS analysis, as the Al–Mn phases seem to contain no Ca. This can be attributed to the EDS detection limit or an incomplete transformation due to the short time elapsed at the high temperatures during LFW.d region , as wellHigh Temperature Deformation, Recrystallization, and Texture: Both Mg alloys exhibit strong basal recrystallization textures after LFW. The basal planes rotate perpendicular to the compression axis  during deformation. The most common recrystallization mechanism that is seen in Mg alloys is related to grain-boundary bulging that will yield recrystallization textures similar to the texture of parent grains, which are basal. It is reported that in FSW, a strong basal texture is generated perpendicular to the force direction to accommodate the deformation induced by the rotative pin [H, at the respective weld peak-temperatures of AZ91 and AZ91–2Ca are 0.87 and 0.91, respectively. Despite the higher weld-peak and homologous temperatures, AZ91–2Ca does not exhibit non-basal texture components activated by high temperature deformation. It can be inferred that the mechanism for the generation of the non-basal grains in AZ91 is other than grain boundary bulging. Other mechanisms of non-basal texture in recrystallized grains of Mg alloys may be due to particle-stimulated nucleation (PSN) or twin-induced nucleation (TIN).tive pin ; we can Particle-Stimulated Nucleation (PSN): The microstructural investigation and the thermodynamic simulations in this work show that while the β–Mg1712 s phase particles disappeared and the Al2Ca phase remained in the AZ91–2Ca weld, very little second phase 12) remained in the AZ91 weld. In Mg–Al-based alloys, the β–Mg1712 phase has not been associated with the nucleation of non-basal grain orientations, hence, it is unlikely that the non-basal texture component is a result of PSN. Since AZ91–2Ca weld does not show any non-basal texture component, the Ca phase does not seem to have a role in texture weakening either.Twin-Induced Nucleation (TIN): In this study, non-basal texture was observed in the shear bands of the AZ91 weld. Shear-bands in Mg occur as a result of discontinuous recrystallization (grain boundary bulging) or twinning [twinning , especiatwinning . As an etwinning . Twinnintwinning . It can twinning , it can Base alloys: AZ91–2Ca shows a lower yield strength, ultimate tensile strength, and ductility compared to AZ91. The lower ductility in the AZ91–2Ca base material compared to AZ91 is due to the additional brittle secondary phase, Al2Ca, which also accounts for the lower ultimate tensile strength and final strain (EL) values reached. AZ91–2Ca also shows a lower yield strength due to the lower amount of the β–Mg1712 phase.AZ91/AZ91 and AZ91–2Ca/AZ91–2Ca welds: Tensile fracture of the welds for both Mg alloys occurred outside the weld region. This is readily explained by the recrystallized basal texture seen in the central weld zone of the AZ91/AZ91 and AZ91–2Ca/AZ91–2Ca welds. The basal planes of the central welded zone are oriented perpendicular to the tensile axis 12 phase dissolved, enriching the α–Mg matrix in Al. The Al8Mn5 phase remained in both Mg alloys and the Al2Ca remained in AZ91–2Ca, albeit evenly dispersed through the central weld zone due to deformation.Both alloys showed microstructural changes with increasing temperature during LFW. At the welding temperatures, the β–Mg0.5 and 88 ± 2.7 HV0.5 in the AZ91/AZ91 and AZ91–2Ca/AZ91–2Ca welds, respectively. Relative to the AZ91 and AZ91–2Ca base material, the central weld zone was about 32% harder.The LFW process generated a recrystallized microstructure in the central weld zone of the AZ91/AZ91 and AZ91–2Ca/AZ91–2Ca welds. Compared to large grain size of AZ91 and AZ91–2Ca base materials (~1000 µm), the fine equiaxed grains in the central weld zone were about 2–6 µm in size. This grain refinement contributed to increase in the hardness of the central weld zone to 87 ± 3.0 HVTensile testing of the AZ91/AZ91 and AZ91–2Ca/AZ91–2Ca welds was undertaken using digital image correlation to measure the strain distribution in the gauge length section of the tensile samples. The tensile strength properties of the welds were similar or slightly higher than the base materials and final failure occurred exclusively in the AZ91 and AZ91–2Ca base materials. Examination of the strain distribution across the AZ91/AZ91 and AZ91–2Ca/AZ91–2Ca joints just before final fracture indicated that the local strains in the central weld zone were about 50% lower than those in the base material regions.A basal recrystallization texture developed in the weld region of the AZ91/AZ91 and AZ91–2Ca/AZ91–2Ca joints, such that the basal planes were oriented perpendicular to the LFW forging direction and the tensile stress axis. This strong basal texture also strengthened the weld region locally  relative to the base material during tensile testing.Developing the LFW process for joining Mg alloys is of interest for assembly of net-shape parts with complex geometries that cannot be joined through other advanced methods, such as friction stir welding. The present research is a first study (to the best knowledge of the authors) on evaluating the feasibility of applying LFW to join AZ91 to AZ91 and AZ91–2Ca to AZ91–2Ca. The following conclusions can be drawn based on the observations of the microstructural phase constituents, texture, microhardness evolution, and tensile properties of the AZ91/AZ91 and AZ91–2Ca/AZ91–2Ca welds: