ABSTRACT
A key question in research on the neurobiology of language is to which extent the language production and comprehension systems share neural infrastructure, but this question has not been addressed in the context of conversation. We utilized a public fMRI dataset where 24 participants engaged in unscripted conversations with a confederate outside the scanner, via an audio-video link. We provide evidence indicating that the two systems share neural infrastructure in the left-lateralized perisylvian language network, but diverge regarding the level of activation in regions within the network. Activity in the left inferior frontal gyrus was stronger in production compared to comprehension, while comprehension showed stronger recruitment of the left anterior middle temporal gyrus and superior temporal sulcus, compared to production. Although our results are reminiscent of the classical Broca-Wernicke model, the anterior (rather than posterior) temporal activation is a notable difference from that model. This is one of the findings that may be a consequence of the conversational setting, another being that conversational production activated what we interpret as higher-level socio-pragmatic processes. In conclusion, we present evidence for partial overlap and functional asymmetry of the neural infrastructure of production and comprehension, in the above-mentioned frontal vs temporal regions during conversation.
Subject(s)
Comprehension , Magnetic Resonance Imaging , Humans , Comprehension/physiology , Magnetic Resonance Imaging/methods , Communication , Language , Prefrontal Cortex , Brain MappingABSTRACT
This work reports the rational design and fabrication of magneto-active microfiber meshes with controlled hexagonal microstructures via melt electrowriting (MEW) of a magnetized polycaprolactone-based composite. In situ iron oxide nanoparticle deposition on oxidized graphene yields homogeneously dispersed magnetic particles with sizes above 0.5 µm and low aspect ratio, preventing cellular internalization and toxicity. With these fillers, homogeneous magnetic composites with high magnetic content (up to 20 weight %) are obtained and processed in a solvent-free manner for the first time. MEW of magnetic composites enabled the creation of skeletal muscle-inspired design of hexagonal scaffolds with tunable fiber diameter, reconfigurable modularity, and zonal distribution of magneto-active and nonactive material, with elastic tensile deformability. External magnetic fields below 300 mT are sufficient to trigger out-of-plane reversible deformation. In vitro culture of C2C12 myoblasts on three-dimensional (3D) Matrigel/collagen/MEW scaffolds showed that microfibers guided the formation of 3D myotube architectures, and the presence of magnetic particles does not significantly affect viability or differentiation rates after 8 days. Centimeter-sized skeletal muscle constructs allowed for reversible, continued, and dynamic magneto-mechanical stimulation. Overall, these innovative microfiber scaffolds provide magnetically deformable platforms suitable for dynamic culture of skeletal muscle, offering potential for in vitro disease modeling.
Subject(s)
Tissue Engineering , Tissue Scaffolds , Tissue Scaffolds/chemistry , Tissue Engineering/methods , Muscle, Skeletal , Printing, Three-DimensionalABSTRACT
Plant-based diets have emerged as athletic performance enhancers for various types of exercise. Therefore, the present study evaluated the effectiveness of plant-based diets on aerobic and strength/power performances, as well as on BMI of physically active individuals. This systematic review and meta-analysis was conducted and reported according to the guidelines outlined in the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) statement. A systematic search of electronic databases, including PubMed, Web of Science and SPORTDiscus, was performed. On the basis of the search and inclusion criteria, four and six studies evaluating the effects of plant-based diets on aerobic and strength/power performances in humans were, respectively, included in the systematic review and meta-analysis. Plant-based diets had a moderate but positive effect on aerobic performance (0·55; 95 % CI 0·29, 0·81) and no effect on strength/power performance (-0·30; 95 % CI -0·67, 0·07). The altogether analyses of both aerobic and strength/power exercises revealed that athletic performance was unchanged (0·01; 95 % CI -0·21, 0·22) in athletes who adopted plant-based diets. However, a small negative effect on BMI (-0·27; 95 % CI -0·40, -0·15) was induced by these diets. The results indicate that plant-based diets have the potential to exclusively assist aerobic performance. On the other hand, these diets do not jeopardise strength/power performance. Overall, the predicted effects of plant-based diets on physical performance are impactless, even though the BMI of their adherents is reduced.
Subject(s)
Athletic Performance , Diet, Plant-Based , Humans , Diet , Exercise , Exercise Therapy , Muscle StrengthABSTRACT
Hydroxycoumarins are an important source of biologically active compounds. Previous studies have shown that the number and position of the hydroxyl substituents in the scaffold play an important role for the observed biological activity. In the present study, 3-(3-hydroxyphenyl)-7-hydroxycoumarin was synthesized, and potential cytogenotoxic effects determined in human HepG2/C3A cells displaying phase 1 and phase 2 enzymes (metabolizing cell ability) and compared to human peripheral blood mononuclear cells (PBMC) without xenobiotics metabolizing capacity. Cell viability was determined with concentrations between 0.01 and 10 µg/ml of 3-(3-hydroxyphenyl)-7-hydroxycoumarin using MTT (3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyl tetrazolium bromide) and trypan blue tests. Genotoxicity was determined utilizing the comet assay, and the clastogenic/aneugenic potential employing the micronucleus (MN) test. The results of the in vitro cytotoxicity assays showed a significant decrease in cell viability of PBMC following exposure to 10 µg/ml concentration of the studied compound after 48 and 72 hr. Comet assay observations noted significant DNA damage in PBMC after 4 hr treatment. No marked cytogenotoxic effects were found in HepG2/C3A cells. No chromosomal mutations were observed in both cell lines. It is important to note that 3-(3-hydroxyphenyl)-7-hydroxycoumarin may exert beneficial pharmacological actions at the low micromolar range and with half-life less than 24 hr. Therefore, the results obtained encourage the continuation of studies on this new molecule for medicinal purposes, but its potential toxicity at higher concentrations and longer exposure times needs to be investigated in further studies.
Subject(s)
DNA Damage , Leukocytes, Mononuclear , Humans , Comet Assay/methods , Micronucleus Tests/methods , Cell Death , Umbelliferones/pharmacologyABSTRACT
PURPOSE: Although bariatric surgery is an effective intervention for obesity, it comes with risks such as early postoperative bleeding (EPB). Identifying preoperative risk factors for this complication can help patients' risk stratification and optimization. We performed a systematic review and meta-analysis to find predictors for early postoperative bleeding after Roux-en-Y gastric bypass (RYGB). METHODS: We conducted a systematic review, searching PubMed, Cochrane Library, and Web of Science until November 2023. We performed a random-effects meta-analysis to explore preoperative risk factors associated with early postoperative bleeding after RYGB. Sources of heterogeneity were explored by leave-one-out analyses. RESULTS: 23 studies were included, comprising 232,488 patients. Male gender (meta-analytical RR = 1.42, 95%CI = 1.21-1.66, I2 = 18%, Q Cochran test p-value = 0.29) and revisional surgery (meta-analytical RR = 1.35, 95%CI = 1.12-1.62, I2 = 22%, Q Cochran test p = 0.21) were associated with higher risk of EPB. On average, patients with EPB were older than the remainder (MD for the mean age = 2.82 years, 95%CI = 0.97-4.67, I2 = 0.00%, Q Cochran test p = 0.46). Except for hypertension (meta-analytical RR = 1.33, 95%CI = 1.02-1.73, I2 = 66%, Q Cochran test p < 0.0001), comorbidities were not associated with a higher risk of EPB. CONCLUSION: Preoperative risk factors, including age, gender, hypertension, and revisional bariatric surgery, are associated with early postoperative bleeding after RYGB. Further primary studies, with higher methodological quality, are required to detail more risk factors.
Subject(s)
Gastric Bypass , Postoperative Hemorrhage , Humans , Gastric Bypass/adverse effects , Risk Factors , Postoperative Hemorrhage/etiology , Postoperative Hemorrhage/epidemiology , Obesity, Morbid/surgery , Risk AssessmentABSTRACT
Epidemiological surveillance of animal tuberculosis (TB) based on whole genome sequencing (WGS) of Mycobacterium bovis has recently gained track due to its high resolution to identify infection sources, characterize the pathogen population structure, and facilitate contact tracing. However, the workflow from bacterial isolation to sequence data analysis has several technical challenges that may severely impact the power to understand the epidemiological scenario and inform outbreak response. While trying to use archived DNA from cultured samples obtained during routine official surveillance of animal TB in Portugal, we struggled against three major challenges: the low amount of M. bovis DNA obtained from routinely processed animal samples; the lack of purity of M. bovis DNA, i.e., high levels of contamination with DNA from other organisms; and the co-occurrence of more than one M. bovis strain per sample (within-host mixed infection). The loss of isolated genomes generates missed links in transmission chain reconstruction, hampering the biological and epidemiological interpretation of data as a whole. Upon identification of these challenges, we implemented an integrated solution framework based on whole genome amplification and a dedicated computational pipeline to minimize their effects and recover as many genomes as possible. With the approaches described herein, we were able to recover 62 out of 100 samples that would have otherwise been lost. Based on these results, we discuss adjustments that should be made in official and research laboratories to facilitate the sequential implementation of bacteriological culture, PCR, downstream genomics, and computational-based methods. All of this in a time frame supporting data-driven intervention.
Subject(s)
Coinfection , Mycobacterium bovis , Tuberculosis , Animals , Mycobacterium bovis/genetics , Tuberculosis/epidemiology , Tuberculosis/veterinary , DNA , GenomicsABSTRACT
PURPOSE: The prompt initiation of a betalactam antibiotic in febrile neutropenic patients is considered standard of care, while the empiric use of vancomycin is recommended by guidelines in specific situations, with a low level of evidence. The objective of this study was to assess the utilization of vancomycin in the management of febrile neutropenia within four Brazilian medical centers that implemented more stringent criteria for its administration. METHODS: A comprehensive retrospective analysis was performed encompassing all instances of febrile neutropenia observed during the period from 2013 to 2019. The primary focus was to identify the reasons for initiating vancomycin therapy. RESULTS: A total of 536 consecutive episodes of febrile neutropenia were documented, involving 384 patients with a median age of 52 years (range 18-86). Chemotherapy preceded febrile neutropenia in 59.7% of cases, while 40.3% occurred after hematopoietic stem cell transplantation. The most prevalent underlying diseases were acute myeloid leukemia (26.5%) and non-Hodgkin's lymphoma (22%). According to international guidelines, vancomycin should have been initiated at the onset of fever in 145 episodes (27%); however, it was administered in only 27 cases (5.0%). Three episodes were associated with Staphylococcus aureus bacteremia, two of which were methicillin resistant. The 15-day and 30-day mortality rates were 5.0% and 9.9%, respectively. CONCLUSIONS: The results of this study underscore the notably low utilization rate of vancomycin in cases of febrile neutropenia, despite clear indications outlined in established guidelines. These findings emphasize the importance of carefully implementing guideline recommendations, considering local epidemiological factors, especially when the strength of recommendation is weak.
Subject(s)
Febrile Neutropenia , Vancomycin , Humans , Adolescent , Young Adult , Adult , Middle Aged , Aged , Aged, 80 and over , Vancomycin/therapeutic use , Vancomycin/adverse effects , Anti-Bacterial Agents , Retrospective Studies , Brazil , Fever/etiology , Fever/chemically induced , Febrile Neutropenia/drug therapy , Febrile Neutropenia/chemically inducedABSTRACT
BACKGROUND: Bariatric surgery is the most effective treatment for sustained weight reduction and obesity-related comorbidities. The development of gallstones as a result of rapid weight loss is a well-known consequence of bariatric procedures. It remains unclear, if there is an increased risk of these gallstones becoming symptomatic. METHODS: A retrospective analysis of 505 consecutive patients submitted to either Roux-en-Y Gastric Bypass or Sleeve Gastrectomy between January and December 2019 was performed. The aim of our study was to determine the incidence of symptomatic cholelithiasis in asymptomatic patients with their gallbladder in situ after bariatric surgery and to identify potential risk factors for its development. RESULTS: Of the 505 patients included, 79 (15.6%) underwent either previous cholecystectomy. (n = 67, 84.8%) or concomitant cholecystectomy during bariatric surgery (n = 12, 15.2%). Among the remaining 426 (84.4%) patients, only 8 (1.9%) became symptomatic during the 12-month follow-up period. When compared with patients who remained asymptomatic, they had a higher median preoperative BMI (47.0 vs. 42.8, p = 0.046) and prevalence of cholelithiasis on preoperative ultrasound (62.5% vs. 10.7%, p = 0.001). Multivariate analysis revealed preoperative BMI and cholelithiasis on preoperative ultrasound as independent risk factors for symptomatic biliary disease (OR 1.187, 95%CI 1.025-1.376, p = 0.022 and OR 10.720, 95%CI 1.613-71.246, p = 0.014, respectively). CONCLUSION: Considering a low incidence of symptomatic gallstones after bariatric surgery, concomitant cholecystectomy should only be performed in symptomatic patients undergoing bariatric surgery. Preoperative factors, such as a higher BMI and positive ultrasound for cholelithiasis, may be related to the development of symptomatic gallstones.
Subject(s)
Bariatric Surgery , Gallstones , Gastric Bypass , Obesity, Morbid , Humans , Gallstones/surgery , Retrospective Studies , Incidence , Watchful Waiting , Obesity, Morbid/surgery , Bariatric Surgery/adverse effects , Gastric Bypass/adverse effects , Gastrectomy/adverse effectsABSTRACT
Recent studies have investigated the use of infrared thermography (IRT) to monitor body surface temperature and correlate it with factors related to animal welfare and performance. In this context, this work proposes a new method for extracting characteristics for the temperature matrix obtained using IRT data from regions of the body surface of cows which, if associated with environmental variables through a machine learning algorithm it generates computational classifiers for heat stress condition. IRT data were collected from different parts of the body of 18 lactating cows housed in a free-stall, monitored for 40 non-consecutive days, three times a day (5:00 a.m., 1:00 p.m., and 7:00 p.m.), during summer and winter, along with physiological data (rectal temperature and respiratory rate) and meteorological data for each time. The IRT data is used to create a descriptor vector based on frequency, accounting for temperatures for a pre-defined range, referred to in the study as 'Thermal Signature' (TS). The generated database was used for training and assessing computational models based on Artificial Neural Network (ANN) to classify heat stress conditions. The models were built using the following predictive attributes for each instance: TS, air temperature, black globe temperature and wet bulb temperature. The goal attribute used for supervised training was the heat stress level classification generated from the rectal temperature and respiratory rate values measured. The models based on different ANN architectures were compared through metrics of the confusion matrix between predicted and measured data, obtaining better results with 8 TS ranges. The best accuracy for classification into four heat stress levels (Comfort, Alert, Danger, and Emergency) was 83.29% using the TS of the ocular region. The classifier for two heat levels of stress (Comfort and Danger) obtained accuracy of 90.10% also using the 8 TS bands of the ocular region.
Subject(s)
Heat Stress Disorders , Thermography , Female , Cattle , Animals , Thermography/methods , Lactation , Body Temperature/physiology , Heat-Shock Response , Models, Animal , Heat Stress Disorders/veterinaryABSTRACT
Toscana virus (TOSV) is emergent in the Mediterranean region and responsible for outbreaks of encephalitis or meningoencephalitis. Sicilian phlebovirus (SFSV) cause epidemics of febrile illness during the summer. The aim of this study was to evaluate the presence of antibodies against TOSV and SFSV in humans in the southwest of Portugal. Neutralizing antibodies to TOSV and SFSV were respectively detected in 5.3% and 4.3% out of 400 human sera tested highlighting the need to increase public health awareness regarding phleboviruses and to include them in the differential diagnosis in patients presenting with fever of short duration and neurological manifestations.
Subject(s)
Antibodies, Viral/blood , Phlebotomus Fever/blood , Phlebotomus Fever/epidemiology , Phlebotomus Fever/virology , Phlebovirus/immunology , Sandfly fever Naples virus/immunology , Adolescent , Adult , Aged , Antibodies, Neutralizing/blood , Female , Humans , Male , Middle Aged , Phlebovirus/genetics , Portugal/epidemiology , Sandfly fever Naples virus/genetics , Seasons , Seroepidemiologic Studies , Young AdultABSTRACT
BACKGROUND: Regarding the assessment of patients' immune and nutritional status, prognostic nutritional index (PNI) has been reported as a predictive marker for surgical outcomes in various types of cancer. The aim of our study was to evaluate the effect of PNI in prognosis of gastric cancer patients submitted to curative-intent resectional surgery. MATERIAL AND METHODS: A retrospective analysis with 637 gastric cancer cases submitted to curative-intent surgery, between 2010 and 2017, in an upper GI surgery unit. We analyzed 396 patients that met the inclusion criteria for this study. The median follow-up was 37 (0-113) months. RESULTS: According to Youden's method, the optimal PNI cutoff for OS was 41.625 (sensitivity 89.3% and specificity 41.3%). OS was significantly shorter in the lower-PNI group of patients when compared to the higher-PNI group (40.26 vs 77.49 months; p < 0.001). Higher PNI had a positive impact on OS in univariable analysis. When adjusted to pStage, higher PNI was still significantly associated with better OS (HR 0.405; CI 95% 0.253-0.649; p < 0.001). Regarding DFS, higher PNI was associated with better DFS (HR 0.421; CI 95% 0.218-0.815; p = 0.010). Higher-PNI group had a protective effect regarding postoperative morbidity and mortality. CONCLUSIONS: In this cohort, PNI was disclosed to significantly impact GC patients' OS and DFS, including in multivariable analysis when adjusting for classical prognostic features. PNI can be used to predict patients at increased risk of postoperative morbidity and mortality. This index may be of use in identifying candidate patients who would benefit from perioperative nutritional support to improve surgical outcomes.
Subject(s)
Nutrition Assessment , Stomach Neoplasms , Humans , Stomach Neoplasms/surgery , Gastrectomy/adverse effects , Prognosis , Retrospective Studies , Nutritional StatusABSTRACT
A questionnaire survey of animal and human health authorities in Europe revealed that leishmaniases are not notifiable in all countries with autochthonous cases. Few countries implement surveillance and control targeting both animal and human infections. Leishmaniases are considered emergent diseases in most countries, and lack of resources is a challenge for control.
Subject(s)
Leishmaniasis , Animals , Europe , European Union , HumansABSTRACT
The use of glyphosate has been increasing over the years, making it one of the most consumed herbicides in the world. Although children are considered a vulnerable population, only four previous published studies determined glyphosate in the urine of non-occupationally exposed children. The paucity of epidemiological data and biomonitoring surveys are considered major gaps, that hinder the implementation of science driven policies in the protection of public health. The aim of the present study was to determine glyphosate in the urine of 41 Portuguese children (2-13 years old) and identify potential determinants of exposure. Glyphosate was detected in 95.1% of the samples (1.77 ± 0.86 µg/L), up to a maximum value of 4.35 µg/L. Glyphosate concentrations were higher in the urine of children aged 7-9 years, living near agricultural areas (<1 km), with a higher percentage of consumption of home-produced foods, and whose parents applied herbicides in the backyard. Risk assessment revealed an exposure representing 1-5.58% of the established Acceptable Daily Intake (ADI) of glyphosate (0.5 mg/kg bw/day). The results should be further analyzed considering the age of the participants, for which no adjusted ADI exists. This was the first published report of glyphosate exposure in the urine of Portuguese children.
Subject(s)
Biological Monitoring , Herbicides , Adolescent , Child , Child, Preschool , Glycine/analogs & derivatives , Humans , Risk Assessment , GlyphosateABSTRACT
In the COVID-19 era, while we are encouraged to be physically far away from each other, social and scientific networking is needed more than ever. The dire consequences of social distancing can be diminished by social networking. Social media, a quintessential component of social networking, facilitates the dissemination of reliable information and fighting against misinformation by health authorities. Distance learning, telemedicine, and telehealth are among the most prominent applications of networking during this pandemic. Additionally, the COVID-19 pandemic highlights the importance of collaborative scientific efforts. In this chapter, we summarize the advantages of harnessing both social and scientific networking in minimizing the harms of this pandemic. We also discuss the extra collaborative measures we can take in our fight against COVID-19, particularly in the scientific field.
Subject(s)
COVID-19 , Social Media , Humans , Pandemics , Physical Distancing , SARS-CoV-2 , SocializationABSTRACT
Some common practices in aquaculture, ornamental trade and fish facilities may disturb the behavioural repertoire of fish and its natural adaptive value, reducing welfare and impairing fish production. Hence, it is necessary to understand fish behaviour, as well as the factors affecting it, to improve the quality of fish's life under artificial environment. Here, we reviewed the behaviour of the angelfish Pterophyllum scalare, an Amazonian cichlid used worldwide both as an ornamental fish and as a fish model in scientific research. We characterized social, reproductive and feeding behaviour, as well as the amazing cognitive ability of the angelfish. In addition, we reviewed the effects of environmental enrichment and suggested some important variables that need to be considered for rearing P. scalare. In this review, we show for the first time a synthesis on behaviour and a best practice overview to improve the welfare of angelfish as a target species. Nonetheless, most topics reviewed fit a broader set of fish species, particularly ornamental ones. This synthesis can therefore open a path for further behavioural research applied to the welfare of angelfish and bring insights to other fish species.
Subject(s)
Cichlids , Animals , Aquaculture , Feeding BehaviorABSTRACT
Human biomonitoring (HBM) data provide information on total exposure regardless of the route and sources of exposure. HBM studies have been applied to quantify human exposure to contaminants and environmental/occupational pollutants by means of determining the parent compounds, their metabolites, or even their reaction products in biological matrices. HBM studies performed among the Portuguese population are dispersed and limited. Thus, to overcome this knowledge gap, this work reviews the published Portuguese HBM information concerning mycotoxins detected in the urine, serum, milk, hair, and nails of different groups of the Portuguese population. This integrative approach to the available HBM data allows us to analyze the main determinants and patterns of exposure of the Portuguese population to the selected hazardous compounds, as well as to assess the potential health risks. We also aimed to identify the main difficulties and challenges of HBM through the analysis of the enrolled studies. Ultimately, this study aims to support national and European policies in promoting human health by summarizing the most important outcomes and lessons learned through the HBM studies carried out in Portugal.
Subject(s)
Biological Monitoring/methods , Environmental Pollutants/analysis , Mycotoxins/analysis , Biological Monitoring/standards , Biological Monitoring/statistics & numerical data , Body Fluids/chemistry , Humans , PortugalABSTRACT
Human biomonitoring (HBM) data provide information on total exposure regardless of the route and sources of exposure. HBM studies have been applied to quantify human exposure to contaminants and environmental/occupational pollutants by determining the parent compounds, their metabolites or even their reaction products in biological matrices. HBM studies performed among the Portuguese population are disperse and limited. To overcome this knowledge gap, this review gathers, for the first time, the published Portuguese HBM information concerning polycyclic aromatic hydrocarbons (PAHs), metals, metalloids, and pesticides concentrations detected in the urine, serum, milk, hair, and nails of different groups of the Portuguese population. This integrative insight of available HBM data allows the analysis of the main determinants and patterns of exposure of the Portuguese population to these selected hazardous compounds, as well as assessment of the potential health risks. Identification of the main difficulties and challenges of HBM through analysis of the enrolled studies was also an aim. Ultimately, this study aimed to support national and European policies promoting human health and summarizes the most important outcomes and lessons learned through the HBM studies carried out in Portugal.
Subject(s)
Environmental Monitoring , Environmental Pollutants/analysis , Metalloids/analysis , Metals/analysis , Pesticides/analysis , Polycyclic Aromatic Hydrocarbons/analysis , Environmental Monitoring/methods , Environmental Pollutants/adverse effects , Humans , PortugalABSTRACT
Speech is a human hallmark, but its evolutionary origins continue to defy scientific explanation. Recently, the open-close mouth rhythm of 2-7 Hz (cycles/second) characteristic of all spoken languages has been identified in the orofacial signals of several nonhuman primate genera, including orangutans, but evidence from any of the African apes remained missing. Evolutionary continuity for the emergence of speech is, thus, still inconclusive. To address this empirical gap, we investigated the rhythm of chimpanzee lip-smacks across four populations (two captive and two wild). We found that lip-smacks exhibit a speech-like rhythm at approximately 4 Hz, closing a gap in the evidence for the evolution of speech-rhythm within the primate order. We observed sizeable rhythmic variation within and between chimpanzee populations, with differences of over 2 Hz at each level. This variation did not result, however, in systematic group differences within our sample. To further explore the phylogenetic and evolutionary perspective on this variability, inter-individual and inter-population analyses will be necessary across primate species producing mouth signals at speech-like rhythm. Our findings support the hypothesis that speech recruited ancient primate rhythmic signals and suggest that multi-site studies may still reveal new windows of understanding about these signals' use and production along the evolutionary timeline of speech.
Subject(s)
Pan troglodytes , Speech , Animals , Biological Evolution , Humans , Lip , Phylogeny , Primates , Vocalization, AnimalABSTRACT
SbPO4 is a complex monoclinic layered material characterized by a strong activity of the nonbonding lone electron pair (LEP) of Sb. The strong cation LEP leads to the formation of layers piled up along the a axis and linked by weak Sb-O electrostatic interactions. In fact, Sb has 4-fold coordination with O similarly to what occurs with the P-O coordination, despite the large difference in ionic radii and electronegativity between both elements. Here we report a joint experimental and theoretical study of the structural and vibrational properties of SbPO4 at high pressure. We show that SbPO4 is not only one of the most compressible phosphates but also one of the most compressible compounds of the ABO4 family. Moreover, it has a considerable anisotropic compression behavior, with the largest compression occurring along a direction close to the a axis and governed by the compression of the LEP and the weak interlayer Sb-O bonds. The strong compression along the a axis leads to a subtle modification of the monoclinic crystal structure above 3 GPa, leading from a 2D to a 3D material. Moreover, the onset of a reversible pressure-induced phase transition is observed above 9 GPa, which is completed above 20 GPa. We propose that the high-pressure phase is a triclinic distortion of the original monoclinic phase. The understanding of the compression mechanism of SbPO4 can aid to improve the ion intercalation and catalytic properties of this layered compound.
ABSTRACT
High pressure X-ray diffraction, Raman scattering, and electrical measurements, together with theoretical calculations, which include the analysis of the topological electron density and electronic localization function, evidence the presence of an isostructural phase transition around 2 GPa, a Fermi resonance around 3.5 GPa, and a pressure-induced decomposition of SnSb2Te4 into the high-pressure phases of its parent binary compounds (α-Sb2Te3 and SnTe) above 7 GPa. The internal polyhedral compressibility, the behavior of the Raman-active modes, the electrical behavior, and the nature of its different bonds under compression have been discussed and compared with their parent binary compounds and with related ternary materials. In this context, the Raman spectrum of SnSb2Te4 exhibits vibrational modes that are associated but forbidden in rocksalt-type SnTe; thus showing a novel way to experimentally observe the forbidden vibrational modes of some compounds. Here, some of the bonds are identified with metavalent bonding, which were already observed in their parent binary compounds. The behavior of SnSb2Te4 is framed within the extended orbital radii map of BA2Te4 compounds, so our results pave the way to understand the pressure behavior and stability ranges of other "natural van der Waals" compounds with similar stoichiometry.