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Paleoproterozoic granitoids of the lesser Himalayan belt are keys to understanding the evolution of the northern Indian continental margin and its position in the Columbia supercontinent assembly. We present whole-rock chemistry and zircon U-Pb geochronological data for Gwaldam Biotite Granite (GBGr) from the Baijnath Klippe (BK) in Kumaun Himalaya to elucidate their petrogenesis and geodynamic implications. Granites are characterized by ferroan, weakly peraluminous nature with high SiO2 and K2O contents, enrichment in LILE (Rb, Th, K and Pb), and depletion in Ba, Nb, P, Hf and Ti. Granites show enrichment in light rare earth element relative to heavy rare earth elements and pronounced negative Eu anomalies. Such chemistry suggests typical A-type granite with high Y/Nb >2 values that characterize it as A2-type granite. Zircon U-Pb ages for the granite yield upper intercept at 1900 ± 3 Ma (core) and 1854 ± 2 Ma (rim). Integrating the chemical and geochronological data, we propose a two-stage evolution model for the area. In the GBGr, the ∼1900 Ma date of zircon core is likely the date of crystallization of the melts presumably formed during the first extensional stage at uppermost mantle – lower crust levels caused by slab break-off/rollback, which followed a post-collisional setting. The second incipient rifting stage produced melt that entrained the zircon cores (∼1900 Ma) during its ascendance and crystallized as the GBGr at ∼1854 Ma when the zircon rims crystallized. It is further proposed that the Paleoproterozoic Northern Indian continental margin later underwent at least two crustal extensions during the Columbia supercontinent agglomeration.
Electroconvulsive therapy (ECT) is a safe and effective treatment for several major psychiatric conditions, including treatment-resistant depression, mania, and schizophrenia; nevertheless, its use remains controversial. Despite its availability in some European countries, ECT is still rarely used in others. This study aims to investigate the experiences and attitudes of early career psychiatrists (ECPs) across Europe towards ECT and to examine how their exposure to ECT influences their perceptions.
Methods
In Europe, a cross-sectional survey was conducted among ECPs, including psychiatric trainees and recently fully qualified psychiatrists.
Results
A total of 573 participants from 30 European countries were included in the study, of whom more than half (N = 312; 54.5%) received ECT training. Overall, ECPs had a positive attitude towards ECT, with the vast majority agreeing or strongly agreeing that ECT is an effective (N = 509; 88.8%) and safe (N = 464; 81.0%) treatment and disagreeing or strongly disagreeing that ECT was used as a form of control or punishment (N = 545; 95.1%). Those who had received ECT training during their psychiatry training were more likely to recommend ECT to their patients (p < 0.001, r = 0.34), and held more positive views on its safety (p < 0.001, r = 0.31) and effectiveness (p < 0.001, r = 0.33). Interest in further education about ECT was moderately high (modal rating on Likert scale: 4, agree), irrespective of prior training exposure.
Conclusions
ECT training is associated with more favorable perceptions of its safety and effectiveness among ECPs. There is a general willingness among ECPs to expand their knowledge and training on ECT, which could enhance patients’ access to this treatment.
Background: The Cognitive Domains and Functional Assessment Questionnaire (CDFAQ) assess cognitive and functional decline based on the DSM-5 criteria for Neurocognitive Disorders. Its accuracy has been assessed and was translated and validated into English. The informant version (CDFAQ-IV) is a 30-item questionnaire that assesses six cognitive domains with 5 items each: Complex Attention (CA), Executive Functions (EF), Learning and
Memory (LM), Language (L), Perceptual-Motor (PM) and Social Cognition. The development of CDFAQ-IV was based on theDSM-5 cognitive domains, but its factor analysis has not been done yet.
Objectives: To perform a Confirmatory Factor Analysis of the CDFAQ-IV to assess the six-factor cognitive domain model.
Methods: Older adults and their informants were invited to participate in this study. The CDFAQ-IV was applied in 292 older adults’ informants. We used the JASP for a Confirmatory Factor Analysis based on Lavaan R Packages. The confirmatory factor analysis was chosen to manual six-factor model. This study was approved by the ethics committee of UFMG.
Results: Concerning model fitness in the confirmatory factor analysis the X2 was significant (p < .001), standardized root mean square residual (SRMR) was .059 (accepted < .08) and the goodness of fit index (GFI) .984 (accepted > .9). However, the root mean square error of approximation (RMSEA) was marginal to the accepted fitness .066 (accepted < .06) and the comparative fit index CFI was .839 under the accepted cutoff (accepted > .9).
Conclusions: The six-factor model of the showed a good fit for three parameters, marginal for one and negative for the CFI. These results point to a convergence of the questionnaire and factors the DSM-5 cognitive domains. These are still preliminary results and we aim to increase our sample to further assess the confirmatory factor analysis.
The Atlantic Forest is one of the most threatened biomes globally. Data from monitoring programs are necessary to evaluate the conservation status of species, prioritise conservation actions and to evaluate the effectiveness of these actions. Birds are particularly well represented in citizen-collected datasets that are used worldwide in ecological and conservation studies. Here, we analyse presence-only data from three online citizen science datasets of Atlantic Forest endemic bird species to evaluate whether the representation of these species was correlated with their global threat status, range and estimated abundance. We conclude that even though species are over- and under-represented with regard to their presumed abundance, data collected by citizen scientists can be used to infer species distribution and, to a lesser degree, species abundance. This pattern holds true for species across global threat status.
Information related to the climate, sowing time, harvest, and crop development is essential for defining appropriate strategies for agricultural activities, which helps both producers and responsible bodies. Paraná, the second largest soybean producer in Brazil, has high climatic variability, which greatly influences planting, harvesting, and crop productivity periods. Therefore, the objective of this study was to regionalize the state of Paraná, considering decennial metrics associated with climate variables and the enhanced vegetation index (EVI) during the soybean cycle. Individual and global analyses of these metrics were conducted performed using multivariate techniques. These analyses were carried out in agricultural scenarios with low, medium, and high precipitation, corresponding to harvest years 2011/2012, 2013/2014, and 2015/2016, respectively. The results obtained from the scores of the retained factors and the cluster analysis were the profile of the groups, with Group 1 presenting more favourable climatic and agronomic conditions for the development of soybean crops for the three harvest years. The opposite occurred for Groups 2 (2011/2012 and 2013/2014) and Group 3 (2015/2016). During the soybean reproductive phases (R2 – R5), precipitation values were inadequate, especially for Group 2 (2011/2012 and 2013/2014) with high water deficit, resulting in a drop in soybean productivity. The climatic and agronomic regionalization of Paraná made it possible to identify the regions most suitable for growing soybeans, the effect of climatic conditions on phenological stages, and the variability of soybean productivity in the three harvest years.
The associations of prior homelessness with current health are unknown. Using nationally representative data collected in private households in England, this study aimed to examine Common Mental Disorders (CMDs), physical health, alcohol/substance dependence, and multimorbidities in people who formerly experienced homelessness compared to people who never experienced homelessness.
Methods
This cross-sectional study utilised data from the 2007 and 2014 Adult Psychiatric Morbidity Surveys. Former homelessness and current physical health problems were self-reported. Current CMDs, alcohol dependence and substance dependence were ascertained using structured validated scales. Survey-weighted logistic regression was used to compare multimorbidities (conditions in combination) for participants who formerly experienced homelessness with those who had never experienced homelessness, adjusting for sociodemographic characteristics, smoking status and adverse experiences. Population attributable fractions (PAFs) were calculated.
Results
Of 13,859 people in the sample, 535 formerly experienced homelessness (3.6%, 95% CI 3.2–4.0). 44.8% of people who formerly experienced homelessness had CMDs (95% CI 40.2–49.5), compared to 15.0% (95% CI 14.3–15.7) for those who had never experienced homelessness. There were substantial associations between prior homelessness and physical multimorbidity (adjusted odds ratio [aOR] 1.98, 95% CI 1.53–2.57), CMD–physical multimorbidity (aOR 3.43, 95% CI 2.77–4.25), CMD–alcohol/substance multimorbidity (aOR 3.53, 95% CI 2.49–5.01) and trimorbidity (CMD–alcohol/substance–physical multimorbidity) (aOR 3.26, 95% CI 2.20–4.83), in models adjusting for sociodemographic characteristics and smoking. After further adjustment for adverse experiences, associations attenuated but persisted for physical multimorbidity (aOR 1.40, 95% CI 1.10–1.79) and CMD–physical multimorbidity (aOR 1.55, 95% CI 1.20–2.00). The largest PAFs were observed for CMD–alcohol/substance multimorbidity (17%) and trimorbidity (16%).
Conclusions
Even in people currently rehoused, marked inequities across multimorbidities remained evident, highlighting the need for longer-term integrated support for people who have previously experienced homelessness.
Silvopastoral systems (SPSs) constitute a modality of agroforestry systems in which trees or shrubs, pastures and animals mutually grow, interacting with the environment, and providing several ecosystem services. This review aims to comprehensively discuss the ecosystem services provided by SPSs in different countries, highlighting the diverse ways these systems can contribute to human well-being and environmental sustainability, also emphasizing the importance of management strategies, the differences among systems and the main shortcomings and challenges to optimizing ecosystem service delivery from SPSs. The review focused on global studies, mainly those published between 2010 and 2024, directly relevant to the topic. We used Google Scholar, Scopus and Web of Science databases for literature screening. SPSs have demonstrated worldwide potential to enhance human food and forage production, nutrient cycling, soil fertility, biological nitrogen fixation, carbon sequestration, greenhouse gas mitigation, erosion control, microclimate regulation, pollination, control of pests and diseases, biodiversity, residue absorption, water quality, spiritual enrichment, recreation and aesthetic experiences. However, most ecosystem services provided by SPSs depend on climate conditions, soil type, choice of species, system design and management practices to ensure that such benefits are not provided at the cost of other important services. Interaction among components is a major challenge for system management and evaluations. Adopting SPSs has the potential to promote sustainable agriculture. Long-term studies are needed to elucidate the implications of multiple interactions within the system and their impact on ecosystem service delivery. Public policies, including evaluating ecosystem services, should be developed to promote the adoption of SPSs.
Avoidable disasters are both saddening and baffling. In 2022, 159 people, mostly in their 20s, and 30s were crushed to death in Itaewon’s narrow alleyway amid South Korea’s first pandemic-restrictions-free Halloween celebration. What is particularly sobering about this tragedy is that although many people called police hotlines as crowds became cramped and static, their calls went unheeded for hours. Rather than order independent investigations into the catastrophe (as of January 2024), the President of South Korea at the time focused on superficial issues such as asking the public to refer to the disaster as an “accident” (which it was not, it was an avoidable disaster) and the casualties as “the dead” (who are casualties indeed, instead of victims of a preventable tragedy). In this paper, we examine how officials’ complacency about public health and safety dangers, ineffective disaster prevention, and preparedness systems, as well as the government’s chronic lack of prioritization of public health and safety may have contributed to the disaster. Furthermore, we discuss the importance of creating integrated public health and safety protection systems to prevent similar tragedies from happening.
A 56-year-old patient diagnosed with bipolar affective disorder type II, who remains stable, with no manifest episodes, thanks to aripiprazole 60mg daily.
Objectives
The aim is to carry out a brief review of the use of the drug as the only stabiliser in bipolar affective disorder.
Methods
A 56-year-old patient, who has been suffering from episodes of hypomania since the age of 40, with episodes of depression. After poor tolerance to the use of the usual stabilisers, and the impossibility of using antidepressants due to hypomanic swings, it was decided to start treatment with aripiprazole orally, up to a maximum of 60mg daily. Despite the fact that the patient, with this treatment, had no side effects and remained more stable psychopathologically, the patient did not comply adequately with the correct dosage, due to his rotating work shifts. This fact explained that although he acknowledged an improvement, he continued with episodes of depressive symptoms lasting several days followed by episodes of hypomanic characteristics.
Results
For this reason, it was decided to change treatment to aripiprazole long-acting injectable, in order to ensure linear blood levels of the drug. Initially, it was decided to prescribe 400mg every 28 days. However, after the first administration, 20 days later, the patient began to show dysphoric mood, with marked emotional lability, living in an egodystonic manner. For this reason, the dose was increased to 600mg on a monthly basis. Since then, after a year and a half with the same treatment, the patient has been stable and in line. There has been no further decompensation of the underlying psychopathology and no side effects.
Conclusions
Aripiprazole in TAB is superior to placebo in type I patients, mainly affecting manic and mixed episodes, but not so much in depressive episodes. It has also been observed that it not only acts in the acute phases, but also has a stabilising function, preventing manic episodes.
One study showed that up to 65% of patients on oral aripiprazole in whom it was replaced by AOM remained clinically stable. In the same study, approximately 50% of those who completed 52 weeks of follow-up were able to maintain clinical stability.
Epilepsy is one of the most common serious brain illness, with symptoms influenced by multiple risk factors and a strong genetic predisposition, rather than having a single expression and cause¹. Neuropsychiatric symptoms in epilepsy can encompass manifestations such as mood alterations, anxiety, sleep disturbances, psychosis, and behavioral disorders. While the motor and sensory manifestations of epileptic seizures are widely recognized, neuropsychiatric symptoms accompanying epilepsy are often underestimated. Therefore, it is essential to understand the most prevalent epidemiological profile of these patients to improve the diagnosis and management of these symptoms.
Objectives
Our goal was to evaluate the neuropsychiatric behavior of epilepsy patients in Brazilian over the past 3 years through hospitalization data in order to outline an epidemiological and behavioral profile.
Methods
A cross-sectional, descriptive, retrospective, and quantitative study was conducted on hospitalizations of individuals simultaneously diagnosed with epilepsy, schizotypal and delusional disorders, and mood disorders in all five regions of Brazil (South, Southeast, Midwest, North, and Northeast) between February 2020 and December 2022. Data from January 2020 were not available. The data used were collected through the Department of Health Informatics of the Brazilian Unified Health System (DATASUS) in the “Hospital Information System of SUS” section, gathering information regarding the nature of care, age range, gender, and ethnicity of the patients.
Results
The analysis covers the years 2020 to 2022, totaling 503,045 hospitalizations. In 2022, the highest number of cases occurred (≈ 37.55%), followed by 2021 (≈ 33.62%) and 2020 (≈ 28.81%). Urgent hospitalizations represented ≈ 90.85% of the total. The most affected age group was 30 to 39 years old (≈ 18.30%). Men were more affected than women (≈ 52.03% and ≈ 47.96%, respectively), and Caucasians accounted for ≈ 36.07% of the hospitalizations. The average length of stay was 19.1 days, and the mortality rate was 1.4%.
Conclusions
Thus, there is a gradual and annual increase in the number of hospitalizations during the observed period. While there is a minimal disparity between the affected genders, it is evident that the profile of male, caucasian, and adult patients is the most prevalent. Moreover, the predominantly urgent nature of hospitalizations points to an alarming scenario regarding this issue. From the analysis of the data obtained in the study, there is a clear need for interventions capable of reducing the prevalence of hospitalizations for neuropsychiatric symptoms in epilepsy patients in Brazil.
Neuropsychiatric disorders are the leading cause of disability worldwide, as seen in cases such as depression, anxiety, bipolar mood disorder and schizophrenia, which can be developed or exacerbated by the use of psychoactive substances. Most mental disorders have an early onset, often leading to early and/or permanent disability, increasing the need and cost of healthcare. Therefore, it is necessary to improve the identification of the epidemiological profile of these cases in the South of Brazil in order to enhance the diagnosis and reduce the costs associated with managing these disorders.
Objectives
The present study aimed to analyze statistical data regarding hospitalizations related to mental disorders caused by the use of psychoactive substances and alcohol in the southern region of Brazil, highlighting the pathological scenario and identifying the most prevalent profiles of these disorders in this region.
Methods
A cross-sectional, descriptive, retrospective, and quantitative study was conducted on hospitalizations of individuals diagnosed with mental and behavioral disorders due to the use of psychoactive substances and alcohol in the states of the Southern region of Brazil (Paraná, Santa Catarina, and Rio Grande do Sul) between February 2020 and December 2022. Data of January 2020 were not available. The data used were collected through the Department of Health Informatics of the Brazilian Unified Health System (DATASUS) in the “Hospital Information System of SUS” section, gathering information regarding the nature of the care, age range, gender, and ethnicity of the patients.
Results
The study covers the years 2020 to 2022, indicating a total of 81,608 hospitalizations, with the year 2022 having the highest number of cases (≈ 37.13%), followed by 2021 (≈ 33.30%) and 2020 (≈ 29.55%). The states with the highest number of hospitalizations were Rio Grande do Sul (≈ 54.90%), Paraná (≈ 29.29%), and Santa Catarina (≈ 15.79%). Urgent hospitalizations accounted for ≈ 87.29% of the total. The most affected age group was 30 to 39 years old (≈ 25.61%). Men were more affected than women (≈ 81.70% and ≈ 18.28%, respectively). Caucasians accounted for ≈ 64.29% of the hospitalizations. The average length of stay was 20.8 days, and the mortality rate was 0.32%.
Conclusions
There is a clear increase in the number of hospitalizations related to mental disorders caused by the use of psychoactive substances in the period from 2020 to 2022 in the southern region of Brazil, with the highest number of cases in the state of Rio Grande do Sul. The most affected population consisted of Caucasian men aged 30 to 39 years old. Furthermore, these results may be related to the increasing trend of psychoactive substance use among the Brazilian population and also the COVID-19 pandemic, which led to a period of underreporting due to social isolation.
Globally, mental disorders account for almost 20% of disease burden and there is growing evidence that mental disorders are associated with various social determinants. Tackling the United Nations Sustainable Development Goals (UN SDGs), which address known social determinants of mental disorders, may be an effective way to reduce the global burden of mental disorders.
Objectives
To examine the evidence base for interventions that seek to improve mental health through targeting the social determinants of mental disorders.
Methods
We conducted a systematic review of reviews, using a five-domain conceptual framework which aligns with the UN SDGs (PROSPERO registration: CRD42022361534). PubMed, PsycInfo, and Scopus were searched from 01 January 2012 until 05 October 2022. Citation follow-up and expert consultation were used to identify additional studies. Systematic reviews including interventions seeking to change or improve a social determinant of mental disorders were eligible for inclusion. Study screening, selection, data extraction, and quality appraisal were conducted in accordance with PRISMA guidelines. The AMSTAR-2 was used to assess included reviews and results were narratively synthesised.
Results
Over 20,000 records were screened, and 101 eligible reviews were included. Most reviews were of low, or critically low, quality. Reviews included interventions which targeted sociocultural (n = 31), economic (n = 24), environmental (n = 19), demographic (n = 15), and neighbourhood (n = 8) determinants of mental disorders. Interventions demonstrating the greatest promise for improved mental health from high and moderate quality reviews (n = 37) included: digital and brief advocacy interventions for female survivors of intimate partner violence; cash transfers for people in low-middle-income countries; improved work schedules, parenting programs, and job clubs in the work environment; psychosocial support programs for vulnerable individuals following environmental events; and social and emotional learning programs for school students. Few effective neighbourhood-level interventions were identified.
Conclusions
This review presents interventions with the strongest evidence base for the prevention of mental disorders and highlights synergies where addressing the UN SDGs can be beneficial for mental health. A range of issues across the literature were identified, including barriers to conducting randomised controlled trials and lack of follow-up limiting the ability to measure long-term mental health outcomes. Interdisciplinary and novel approaches to intervention design, implementation, and evaluation are required to improve the social circumstances and mental health experienced by individuals, communities, and populations.
In recent years, mental health has gained prominence in public health, prompting thorough investigations into psychiatric condition trends. This study conducts a comprehensive epidemiological analysis of hospitalizations for Schizophrenia, Schizotypal, and Delirium Disorders in Rio Grande do Sul (RS) over the past five years. By revealing these patterns, it enhances our understanding of regional mental health dynamics and offers insights for intervention strategies, resource planning, and improved mental healthcare. The ultimate goal is to advance more effective and accessible mental healthcare in RS and beyond.
Objectives
This study aims to analyze the prevalence and epidemiological profile of hospitalizations due to psychiatric disorders to assist in the diagnosis and outcome of affected patients.
Methods
A cross-sectional, descriptive, retrospective, and quantitative study was conducted regarding hospitalizations for Schizophrenia, Schizotypal Disorders, and Delirium in the state of RS between January 2018 and November 2022. Data were collected from the Department of Informatics of the Brazilian Unified Health System (DATASUS) in the “Hospital Information System of SUS” section, focusing on the nature of care, age group, gender, and ethnicity of the patients. The information was aggregated over the five-year period based on the four mentioned descriptors and subsequently analyzed to establish a profile of hospitalizations during that period.
Results
The analysis spans from 2018 to 2022, encompassing a total of 28,345 hospitalizations. In 2019, there was the highest number of cases (22.21%), followed by 2018 (21.08%). Urgent care admissions constituted 85.34% of the total. The age group most affected was 35 to 39 years (11.8%). Men were more affected than women (60.18%), and the majority of hospitalizations were among the Caucasian ethnicity (75.12%). The average length of stay was 23.7 days, and the mortality rate stood at 0.26%.
Conclusions
The increasing trend in hospitalizations, peaking in 2019, highlights the need for preventive measures. Urgent admissions (85.34%) underscore the demand for accessible mental health resources. Men in the 35 to 39 age group are disproportionately affected, suggesting specific risk factors. The predominance of Caucasian ethnicity emphasizes the need for culturally sensitive care. A longer average length of stay (23.7 days) underscores treatment complexity, while a low mortality rate (0.26%) signals effective medical care. In essence, these findings inform tailored mental health policies to enhance service quality and prioritize patient-centered approaches.
Dementia is a syndrome of high prevalence and health impact. The Montreal Cognitive Assessment (MoCA) questionnaire is a screening tool whose use has increased in recent years, especially in cases of mild cognitive impairment. Some studies suggest that its ability to detect cognitive impairment, especially in early or mild stages, seems to be greater than gold-standard instruments (Ciesielska et al., 2016).
Objectives
We have performed a meta-analysis of reliability generalization to see if different adaptations and use in different contexts show consistent results.
Methods
We performed a literature search in PyscINFO and Medline with the terms “Cognitive impairment” AND “internal consistency” AND “Cronbach”, using the following inclusion criteria:
1. Be a study in which the MoCA scale was applied to a population sample.
2. Studies published in the last 10 years.
3. Studies that provide the reliability coefficient or sufficient data to calculate them.
4. Be written in English or Spanish.
We have limited our study to the last 10 years and the English language has given us a total of 19 results in Medline and 132 results in PsycINFO. Subsequently, we completed this search by snowball sampling.
A random effects model was assumed for the statistical calculations and the transformation of our values using the Hakstian and Whalen (1976) proposal. Statistical analysis was performed with the MAJOR package of the Janovi program, based on the R environment.
Results
We obtained a mean reliability for the transformed test scores of 0.42 (95% CI: 0.38 - 0.45), as well as high heterogeneity measured by Cochran’s Q statistic and the I2 index, which is attributed after analysis of moderating variables to the geographical adaptation of the questionnaire and the type of patient on whom it is applied. Our Funnel Plot graph indicates that we do not appear to have committed a publication bias.
Conclusions
Our meta-analysis shows high heterogeneity, mainly explained by the population of origin, both geographically (continent) and clinically (presence of primary cognitive impairment or not), with special incidence in those with impairment secondary to other pathologies, mainly neurological. However, we should consider the high probability that we have not included important variables in our analysis that could increase the explanatory power of our model.
Sucrose yield in sugarcane is a complex process regulated by both environmental and endogenous factors. However, the metabolic balance driving vegetative growth and sucrose accumulation remains poorly understood. Herein, we carried out a comprehensive assessment of carbohydrate dynamics throughout the crop cycle in two sugarcane varieties varying in biomass production, evaluating the carbon metabolism in both leaves and stalks. Our data revealed that the decline in photosynthetic rates during sugarcane maturation is associated not only to accumulation of sugars in leaves but also due to stomatal and non-stomatal limitations. We found that metabolic processes in leaves and stalks were intrinsically linked. While IACSP94-2094 had higher stalk sucrose concentration than IACSP95-5000, this latter produced more biomass. Compared to IACSP95-5000, IACSP94-2094 showed higher sucrose phosphate synthase (SPS) activity in leaves and stalks, along with lower soluble acid invertase (SAI) activity in leaves during the maximum growth stage. Interestingly, IACSP94-2094 also exhibited higher stalk SPS activity and lower stalk SAI activity than IACSP95-5000 during maturation. High biomass production by IACSP95-5000 was associated with higher sucrose synthase (SuSy) and SAI activity in leaves and higher SuSy and soluble neutral invertase (SNI) activity in stalks when compared to IACSP94-2094 during the maximum growth. Despite the contrasting strategies, both varieties displayed similar total sucrose yield, a balance between sucrose concentration and biomass production. This phenomenon implies the presence of a compensatory mechanism in sugarcane, with high biomass production compensating low sucrose accumulation and vice versa.
A centre of a differential system in the plane $ {\mathbb {R}}^2$ is an equilibrium point $p$ having a neighbourhood $U$ such that $U\setminus \{p\}$ is filled with periodic orbits. A centre $p$ is global when $ {\mathbb {R}}^2\setminus \{p\}$ is filled with periodic orbits. In general, it is a difficult problem to distinguish the centres from the foci for a given class of differential systems, and also it is difficult to distinguish the global centres inside the centres. The goal of this paper is to classify the centres and the global centres of the following class of quintic polynomial differential systems
Several samples of large- and small-particle magnetite (Fe3O4), as well as its thermal decomposition products formed at different temperatures and atmospheres, have been studied extensively by Mössbauer spectroscopy (MS), both with and without an applied field of 6T. Synthetic mixtures of magnetite and poorly- or well-crystallized maghemite have also been studied. Large-particle magnetite (MCD > 200 nm), when heated in air for 12 hours at T < 400°C, transforms to a mixture of well-crystallized hematite and magnetite, the latter one remaining stoichiometric, according to the relative area-ratios obtained from MS. Thermal treatment at 1300°C in a controlled O2 partial pressure, produced a mixture of stoichiometric and nonstoichiometric magnetite, but the latter component seems to be composed of particles with different degrees of nonstoichiometry. The Mössbauer spectra of the decomposition products at T < 200°C in air of small-particle magnetite (MCD ~ 80 nm) could be successfully interpreted as a mixture of magnetite and maghemite, rather than nonstoichiometric magnetite. This suggestion is further supported by the experiments with the synthetic mixtures. It is clearly demonstrated that is not possible, even by applying a strong external field, to separate the contribution of the A-site of magnetite from that of maghemite.
Synthetic, relatively well-crystallized aluminum-substituted maghemite samples, γ-(Aly·Fe1−y)2O3, with y = 0, 0.032, 0.058, 0.084, 0.106 and 0.151 have been studied by X-ray diffraction and zero-field Mössbauer spectroscopy in the range 8 K to 475 K, and also with an external field of 60 kOe at 4.2 K and 275 K. It was found that there are two different converging models for fitting the zero-field spectra of the maghemites with a superposition of two Lorentzian-shaped sextets, both resulting in inconsistent values for the hyperfine fields (Hhf) and/or the center shifts (δ) of the tetrahedral (A) and octahedral (B) ferric ions. From the applied-field measurements it is concluded that there is a constant difference of 0.12 ± 0.01 mm/s between δB and δA, regardless of the Al content. For the Al-free sample the center shifts are found as: δA = 0.370 mm/s and δB = 0.491 mm/s at 4.2 K and δA = 0.233 mm/s and δB = 0.357 mm/s at 275 K (relative to metallic iron), with an estimated error of 0.005 mm/s. Both δA and δB are observed to decrease with increasing Al concentration. The effective hyperfine fields for the non-substituted maghemite sample are: Heff,A = 575 kOe and Heff,B = 471 kOe at 4.2 K and Heff,A = 562 kOe and Heff,B = 449 kOe at 275 K, with an error of 1 kOe. The B-site hyperfine field remains approximately constant with Al substitution, while for the A site a slight decrease with increasing Al content was observed.
Magnetic fractionation, chemical, and structural analyses prove that alteration of ilmenite from Manavalakurichi deposit extends only up to the formation of pseudorutile with traces of rutile. The data indicate that ferrous to ferric iron transformation, ferric iron oxide formation, and iron removal contribute to the alteration sequence. The first two highly magnetic fractions are not unaltered ilmenite. A reduction in ilmenite unit cell volume indicates the ferrous-ferric conversion occurred during alteration.