Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 180
Filtrar
1.
Niger J Clin Pract ; 27(9): 1044-1050, 2024 Sep 01.
Artigo em Inglês | MEDLINE | ID: mdl-39348323

RESUMO

BACKGROUND: While we attempt to restore occlusion in completely edentulous patients there is a consensus among clinicians to articulate the cast using average value and avoid performing facebow transfer. Various studies question the application of facebow transfer in the fabrication of removable complete denture fabrication. AIM: This study was therefore aimed to study the effect on condylar guidance with casts mounted by the facebow method, Bonwill's method, and radiographic method. METHODS: A cross-sectional study was performed using casts of edentulous patients attending the Department of Prosthodontics. After establishing a tentative jaw relationship using wax occlusal rims in the edentulous participants, the casts were mounted by Bonwill's method and the facebow transfer method to a semi-adjustable articulator. Protrusive records of the subjects were used to program the articulator to obtain the condylar guidance values. Digital lateral cephalographs were made both in centric and protrusive jaw relationships. The mandibular condyles were then traced and overlapped to obtain radiographic values. The condylar guidance values obtained by Bonwill's method, facebow method and radiographic method were compared using Wilcoxon's signed rank test and Mann-Whitney U test. The SPSS Statistics for Windows (Version 21.0. Armonk, NY, USA:IBM Corp.), and, at a probability value of 0.05, the significance of every statistical test was predetermined. RESULTS: Ten edentulous 45-70 year olds participated in the study. The mean discrepancy between radiography and facebow methods was 12.8° for the right side and 12.7° for the left (P < 0.005). The difference between radiography and Bonwill's methods was significant (P < 0.005), with a mean difference of 34.3° for the right side and 34.7° for the left side. The difference between Bonwill's method and the facebow method was significant (P < 0.005), with a mean difference of 21.5° for the right side and 22° for the left side. CONCLUSION: The condylar guidance values obtained by clinical methods (Bonwill's and Facebow) were significantly lesser (P < 0.005) compared to the values obtained by radiographic method.


Assuntos
Articuladores Dentários , Côndilo Mandibular , Humanos , Estudos Transversais , Feminino , Masculino , Pessoa de Meia-Idade , Côndilo Mandibular/diagnóstico por imagem , Registro da Relação Maxilomandibular/métodos , Boca Edêntula/diagnóstico por imagem , Cefalometria/métodos , Idoso , Prótese Total
3.
Nat Commun ; 15(1): 7264, 2024 Aug 23.
Artigo em Inglês | MEDLINE | ID: mdl-39179624

RESUMO

The S = 1/2 triangular lattice antiferromagnet (TLAF) is a paradigmatic example of frustrated quantum magnetism. An ongoing challenge involves understanding the influence of exchange anisotropy on the collective behavior within such systems. Using inelastic neutron scattering (INS) and advanced calculation techniques, we have studied the low and high-temperature spin dynamics of Ba2La2CoTe2O12 (BLCTO): a Co2+-based Jeff = 1/2 TLAF that exhibits 120° order below TN = 3.26 K. We determined the spin Hamiltonian by fitting the energy-resolved paramagnetic excitations measured at T > TN, revealing exceptionally strong easy-plane XXZ anisotropy. Below TN, the excitation spectrum exhibits a high energy continuum having a larger spectral weight than the single-magnon modes, suggesting a scenario characterized by a spinon confinement length that markedly exceeds the lattice spacing. We conjecture that this phenomenon arises from the proximity to a quantum melting point, even under strong easy-plane XXZ anisotropy. Finally, we highlight characteristic flat features in the excitation spectrum, which are connected to higher-order van Hove singularities in the magnon dispersion directly induced by easy-plane XXZ anisotropy. Our results provide a rare experimental insight into the nature of highly anisotropic S = 1/2 TLAFs between the Heisenberg and XY limits.

5.
J Am Chem Soc ; 146(28): 19146-19159, 2024 Jul 17.
Artigo em Inglês | MEDLINE | ID: mdl-38953583

RESUMO

Van der Waals (vdW) magnets both allow exploration of fundamental 2D physics and offer a route toward exploiting magnetism in next generation information technology, but vdW magnets with complex, noncollinear spin textures are currently rare. We report here the syntheses, crystal structures, magnetic properties and magnetic ground states of four bulk vdW metal-organic magnets (MOMs): FeCl2(pym), FeCl2(btd), NiCl2(pym), and NiCl2(btd), pym = pyrimidine and btd = 2,1,3-benzothiadiazole. Using a combination of neutron diffraction and bulk magnetometry we show that these materials are noncollinear magnets. Although only NiCl2(btd) has a ferromagnetic ground state, we demonstrate that low-field hysteretic metamagnetic transitions produce states with net magnetization in zero-field and high coercivities for FeCl2(pym) and NiCl2(pym). By combining our bulk magnetic data with diffuse scattering analysis and broken-symmetry density-functional calculations, we probe the magnetic superexchange interactions, which when combined with symmetry analysis allow us to suggest design principles for future noncollinear vdW MOMs. These materials, if delaminated, would prove an interesting new family of 2D magnets.

6.
Int J Mol Sci ; 25(10)2024 May 17.
Artigo em Inglês | MEDLINE | ID: mdl-38791525

RESUMO

The worldwide incidence of prediabetes/type 2 has continued to rise the last 40 years. In the same period, the mean daily energy intake has increased, and the quality of food has significantly changed. The chronic exposure of pancreatic ß-cells to calorie excess (excessive energy intake) and food additives may increase pancreatic insulin secretion, decrease insulin pulses and/or reduce hepatic insulin clearance, thereby causing chronic hyperinsulinemia and peripheral insulin resistance. Chronic calorie excess and hyperinsulinemia may promote lipogenesis, inhibit lipolysis and increase lipid storage in adipocytes. In addition, calorie excess and hyperinsulinemia can induce insulin resistance and contribute to progressive and excessive ectopic fat accumulation in the liver and pancreas by the conversion of excess calories into fat. The personal fat threshold hypothesis proposes that in susceptible individuals, excessive ectopic fat accumulation may eventually lead to hepatic insulin receptor resistance, the loss of pancreatic insulin secretion, hyperglycemia and the development of frank type 2 diabetes. Thus, type 2 diabetes seems (partly) to be caused by hyperinsulinemia-induced excess ectopic fat accumulation in the liver and pancreas. Increasing evidence further shows that interventions (hypocaloric diet and/or bariatric surgery), which remove ectopic fat in the liver and pancreas by introducing a negative energy balance, can normalize insulin secretion and glucose tolerance and induce the sustained biochemical remission of type 2 diabetes. This pathophysiological insight may have major implications and may cause a paradigm shift in the management of type 2 diabetes: avoiding/reducing ectopic fat accumulation in the liver and pancreas may both be essential to prevent and cure type 2 diabetes.


Assuntos
Diabetes Mellitus Tipo 2 , Hiperinsulinismo , Hipernutrição , Humanos , Hiperinsulinismo/metabolismo , Hiperinsulinismo/complicações , Hiperinsulinismo/etiologia , Diabetes Mellitus Tipo 2/metabolismo , Diabetes Mellitus Tipo 2/etiologia , Hipernutrição/complicações , Resistência à Insulina , Tecido Adiposo/metabolismo , Animais , Fígado/metabolismo , Fígado/patologia , Insulina/metabolismo , Pâncreas/metabolismo , Pâncreas/patologia
7.
J Plant Physiol ; 294: 154185, 2024 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-38373389

RESUMO

Five decades ago, the first report of a shift from C3 to CAM (crassulacean acid metabolism) photosynthesis following the imposition of stress was published in this journal. The annual, Mesembryanthemum crystallinum (Aizoaceae), was shown to be a C3 plant when grown under non-saline conditions, and a CAM plant when exposed to high soil salinity. This observation of environmentally triggered CAM eventually led to the introduction of the term facultative CAM, which categorises CAM that is induced or upregulated in response to water-deficit stress and is lost or downregulated when the stress is removed. Reversibility of C3-to-CAM shifts distinguishes stress-driven facultative-CAM responses from purely ontogenetic increases of CAM activity. We briefly review how the understanding of facultative CAM has developed, evaluate the current state of knowledge, and highlight questions of continuing interest. We demonstrate that the long-lived leaves of a perennial facultative-CAM arborescent species, Clusia pratensis, can repeatedly switch between C3 and CAM in response to multiple wet-dry-wet cycles. Undoubtedly, this is a dedicated response to environment, independent of ontogeny. We highlight the potential for engineering facultative CAM into C3 crops to provide a flexible capacity for drought tolerance.


Assuntos
Mesembryanthemum , Fotossíntese , Fotossíntese/fisiologia , Mesembryanthemum/metabolismo , Metabolismo Ácido das Crassuláceas , Produtos Agrícolas/metabolismo , Água/metabolismo
8.
Chem Mater ; 36(1): 501-513, 2024 Jan 09.
Artigo em Inglês | MEDLINE | ID: mdl-38222936

RESUMO

Quantum spin liquids are highly entangled magnetic states with exotic properties. The S = 1/2 square-lattice Heisenberg model is one of the foundational models in frustrated magnetism with a predicted, but never observed, quantum spin liquid state. Isostructural double perovskites Sr2CuTeO6 and Sr2CuWO6 are physical realizations of this model but have distinctly different types of magnetic order and interactions due to a d10/d0 effect. Long-range magnetic order is suppressed in the solid solution Sr2CuTe1-xWxO6 in a wide region of x = 0.05-0.6, where the ground state has been proposed to be a disorder-induced spin liquid. Here, we present a comprehensive neutron scattering study of this system. We show using polarized neutron scattering that the spin liquid-like x = 0.2 and x = 0.5 samples have distinctly different local spin correlations, which suggests that they have different ground states. Low-temperature neutron diffraction measurements of the magnetically ordered W-rich samples reveal magnetic phase separation, which suggests that the previously ignored interlayer coupling between the square planes plays a role in the suppression of magnetic order at x ≈ 0.6. These results highlight the complex magnetism of Sr2CuTe1-xWxO6 and hint at a new quantum critical point between 0.2 < x < 0.4.

9.
Mol Reprod Dev ; 91(1): e23735, 2024 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-38282317

RESUMO

Boar seminal plasma (SP) proteins were associated with differences on sperm resistance to cooling at 17°C. However, information about seminal plasma proteins in boars classified by capacity of semen preservation and in vivo fertility remains lacking. Thus, the objective was to evaluate the SP proteome in boars classified by capacity of semen preservation and putative biomarkers for fertility. The ejaculates from high-preservation (HP) showed higher progressive motility during all 5 days than the low-preservation (LP) boars. There was no difference for farrowing rate between ejaculates from LP (89.7%) and HP boars (88.4%). The LP boars presented lower total piglets born (14.0 ± 0.2) than HP (14.8 ± 0.2; p < 0.01). A total of 257 proteins were identified, where 184 were present in both classes of boar, and 41 and 32 were identified only in LP and HP boars, respectively. Nine proteins were differently expressed: five were more abundant in HP (SPMI, ZPBP1, FN1, HPX, and C3) and four in LP boars (B2M, COL1A1, NKX3-2, and MPZL1). The HP boars had an increased abundance of SP proteins related to sperm resistance and fecundation process which explains the better TPB. LP boars had a higher abundance of SP proteins associated with impaired spermatogenesis.


Assuntos
Preservação do Sêmen , Sêmen , Suínos , Animais , Masculino , Sêmen/metabolismo , Preservação do Sêmen/veterinária , Proteômica , Inseminação Artificial , Espermatozoides , Fertilidade , Análise do Sêmen , Proteínas de Plasma Seminal/metabolismo , Motilidade dos Espermatozoides
10.
Proteomics Clin Appl ; 18(1): e2300008, 2024 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-37329193

RESUMO

PURPOSE: Our main goal is to identify the alterations in the amniotic fluid (AF) metabolome in Zika virus (ZIKV)-infected patients and their relation to congenital Zika syndrome (CZS) progression. EXPERIMENTAL DESIGN: We applied an untargeted metabolomics strategy to analyze seven AF of pregnant women: healthy women and ZIKV-infected women bearing non-microcephalic and microcephalic fetuses. RESULTS: Infected patients were characterized by glycerophospholipid metabolism impairment, which is accentuated in microcephalic phenotypes. Glycerophospholipid decreased concentration in AF can be a consequence of intracellular transport of lipids to the placental or fetal tissues under development. The increased intracellular concentration of lipids can lead to mitochondrial dysfunction and neurodegeneration caused by lipid droplet accumulation. Furthermore, the dysregulation of amino acid metabolism was a molecular fingerprint of microcephalic phenotypes, specifically serine, and proline metabolisms. Both amino acid deficiencies were related to neurodegenerative disorders, intrauterine growth retardation, and placental abnormalities. CONCLUSIONS AND CLINICAL RELEVANCE: This study enhances our understanding of the development of CZS pathology and sheds light on dysregulated pathways that could be relevant for future studies.


Assuntos
Microcefalia , Complicações Infecciosas na Gravidez , Infecção por Zika virus , Zika virus , Feminino , Gravidez , Humanos , Infecção por Zika virus/complicações , Líquido Amniótico , Placenta , Aminoácidos , Lipídeos
11.
Microorganisms ; 11(10)2023 Sep 22.
Artigo em Inglês | MEDLINE | ID: mdl-37894025

RESUMO

The fungicide iprodione (IPR) (3-(3,5-dichlorophenyl) N-isopropyl-2,4-dioxoimidazolidine-1-carboxamide) is a highly toxic compound. Although IPR has been restricted, it is still being applied in many places around the world, constituting an environmental risk. The biodegradation of IPR is an attractive option for reducing its residues. In this study, we isolated thirteen IPR-tolerant bacteria from a biopurification system designed to treat pesticides. A study of biodegradation using different strains was comparatively evaluated, and the best degradation rate of IPR was presented by Achromobacter sp. C1 with a half-life (T1/2) of 9 days. Based on a nano-LC-MS/MS analysis for the strains, proteins solely expressed in the IPR treatment were identified by highlighting the strain Achromobacter sp. C1, with 445 proteins primarily involved in the biosynthesis of secondary metabolites and microbial metabolism in diverse environments. Differentially expressed protein amidases were involved in six metabolic pathways. Interestingly, formamidase was inhibited while other cyclases, i.e., amidase and mandelamide hydrolase, were overexpressed, thereby minimizing the effect of IPR on the metabolism of strain C1. The dynamic changes in the protein profiles of bacteria that degrade IPR have been poorly studied; therefore, our results offer new insight into the metabolism of IPR-degrading microorganisms, with special attention paid to amidases.

12.
Ann Bot ; 132(4): 627-654, 2023 11 25.
Artigo em Inglês | MEDLINE | ID: mdl-37698538

RESUMO

BACKGROUND AND SCOPE: The growth of experimental studies of crassulacean acid metabolism (CAM) in diverse plant clades, coupled with recent advances in molecular systematics, presents an opportunity to re-assess the phylogenetic distribution and diversity of species capable of CAM. It has been more than two decades since the last comprehensive lists of CAM taxa were published, and an updated survey of the occurrence and distribution of CAM taxa is needed to facilitate and guide future CAM research. We aimed to survey the phylogenetic distribution of these taxa, their diverse morphology, physiology and ecology, and the likely number of evolutionary origins of CAM based on currently known lineages. RESULTS AND CONCLUSIONS: We found direct evidence (in the form of experimental or field observations of gas exchange, day-night fluctuations in organic acids, carbon isotope ratios and enzymatic activity) for CAM in 370 genera of vascular plants, representing 38 families. Further assumptions about the frequency of CAM species in CAM clades and the distribution of CAM in the Cactaceae and Crassulaceae bring the currently estimated number of CAM-capable species to nearly 7 % of all vascular plants. The phylogenetic distribution of these taxa suggests a minimum of 66 independent origins of CAM in vascular plants, possibly with dozens more. To achieve further insight into CAM origins, there is a need for more extensive and systematic surveys of previously unstudied lineages, particularly in living material to identify low-level CAM activity, and for denser sampling to increase phylogenetic resolution in CAM-evolving clades. This should allow further progress in understanding the functional significance of this pathway by integration with studies on the evolution and genomics of CAM in its many forms.


Assuntos
Metabolismo Ácido das Crassuláceas , Fotossíntese , Humanos , Filogenia , Fotossíntese/fisiologia , Plantas/genética , Plantas/metabolismo , Planeta Terra
13.
Niger J Clin Pract ; 26(8): 1157-1164, 2023 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-37635611

RESUMO

Background: Human teeth and nails have demonstrated similar factors genetically, embryologically, and morphologically. The fingernail form may be used as a post-extraction guide for selecting the tooth form. Aim: To evaluate the correlation between the maxillary left central incisor tooth form with the left index, middle, and ring fingernails in the Saudi Arabian population. Materials and Methods: A descriptive cross-sectional study with purposive sampling was done among 200 Saudi participants. The maxillary left central incisor and the left index, middle, and ring fingernail were scanned using an intraoral scanner. The 3D digital images were converted to 3D models. The tooth form (tooth length, tooth width, and tooth shape) and nail form (nail length, nail width, and nail shape) were measured using the CAD software. Pearson's correlation coefficient and T-test were used for statistical analysis (P < 0.05). Result: A significant correlation exists between tooth length and nail length, with a maximum correlation toward index nail length (P = 0.015). A significant correlation exists between tooth width and nail width, with a maximum correlation toward ring nail width (P = 0.002). A significant correlation exists between tooth length and nail length in females with a maximum correlation toward index nail length in females (P = 0.001). The mean percentage of similarity between tooth and nail shape (index, middle, and ring) in males and females shows a highly significant difference between them (P = 0.001). The results indicate that the tooth and nail shape are similar (70 to 90%) based on the criteria set by the software. Conclusion: A definite correlation exists between maxillary central incisor tooth form and fingernail form. The fingernail form may be used as a post-extraction guide for selecting the maxillary central incisor tooth form in the Saudi Arabian population.


Assuntos
Incisivo , Unhas , Feminino , Masculino , Humanos , Arábia Saudita , Estudos Transversais , Software
14.
J Phys Condens Matter ; 35(49)2023 Sep 12.
Artigo em Inglês | MEDLINE | ID: mdl-37604160

RESUMO

Magnetic diffuse scattering-the broad magnetic scattering features observed in neutron-diffraction data above a material's magnetic ordering temperature-provides a rich source of information about the material's magnetic Hamiltonian. However, this information has often remained under-utilised due to a lack of available computer software that can fit values of magnetic interaction parameters to such data. Here, an open-source computer program, Spinteract, is presented, which enables straightforward refinement of magnetic interaction parameters to powder and single-crystal magnetic diffuse scattering data. The theory and implementation of this approach are summarised. Examples are presented of refinements to published experimental diffuse-scattering data sets for the canonical antiferromagnet MnO and the highly-frustrated classical spin liquid Gd3Ga5O12. Guidelines for data collection and refinement are outlined, and possible developments of the approach are discussed.

15.
Ann Bot ; 132(4): 597-625, 2023 11 25.
Artigo em Inglês | MEDLINE | ID: mdl-37303205

RESUMO

BACKGROUND: Crassulacean acid metabolism (CAM) photosynthesis is a successful adaptation that has evolved often in angiosperms, gymnosperms, ferns and lycophytes. Present in ~5 % of vascular plants, the CAM diaspora includes all continents apart from Antarctica. Species with CAM inhabit most landscapes colonized by vascular plants, from the Arctic Circle to Tierra del Fuego, from below sea level to 4800 m a.s.l., from rainforests to deserts. They have colonized terrestrial, epiphytic, lithophytic, palustrine and aquatic systems, developing perennial, annual or geophyte strategies that can be structurally arborescent, shrub, forb, cladode, epiphyte, vine or leafless with photosynthetic roots. CAM can enhance survival by conserving water, trapping carbon, reducing carbon loss and/or via photoprotection. SCOPE: This review assesses the phylogenetic diversity and historical biogeography of selected lineages with CAM, i.e. ferns, gymnosperms and eumagnoliids, Orchidaceae, Bromeliaceae, Crassulaceae, Euphorbiaceae, Aizoaceae, Portulacineae (Montiaceae, Basellaceae, Halophytaceae, Didiereaceae, Talinaceae, Portulacaceae, Anacampserotaceae and Cactaceae) and aquatics. CONCLUSIONS: Most extant CAM lineages diversified after the Oligocene/Miocene, as the planet dried and CO2 concentrations dropped. Radiations exploited changing ecological landscapes, including Andean emergence, Panamanian Isthmus closure, Sundaland emergence and submergence, changing climates and desertification. Evidence remains sparse for or against theories that CAM biochemistry tends to evolve before pronounced changes in anatomy and that CAM tends to be a culminating xerophytic trait. In perennial taxa, any form of CAM can occur depending upon the lineage and the habitat, although facultative CAM appears uncommon in epiphytes. CAM annuals lack strong CAM. In CAM annuals, C3 + CAM predominates, and inducible or facultative CAM is common.


Assuntos
Metabolismo Ácido das Crassuláceas , Fotossíntese , Filogenia , Carbono/metabolismo , Ecossistema
16.
Ann Bot ; 132(4): 563-575, 2023 11 25.
Artigo em Inglês | MEDLINE | ID: mdl-37010384

RESUMO

BACKGROUND: In January 1972, Klaus Winter submitted his first paper on crassulacean acid metabolism (CAM) whilst still an undergraduate student in Darmstadt. During the subsequent half-century, he passed his Staatsexamensarbeit, obtained his Dr. rer. nat. summa cum laude and Dr. rer. nat. habil., won a Heinz Maier-Leibnitz Prize and a Heisenberg Fellowship, and has occupied positions in Germany, Australia, the USA and Panama. Now a doyen in CAM circles, and a Senior Staff Scientist at the Smithsonian Tropical Research Institute (STRI), he has published over 300 articles, of which about 44 % are about CAM. SCOPE: I document Winter's career, attempting to place his CAM-related scientific output and evolution in the context of factors that have influenced him as he and his science progressed from the 1970s to the 2020s.


Assuntos
Metabolismo Ácido das Crassuláceas , Humanos , Austrália
17.
Int J Mol Sci ; 24(5)2023 Feb 25.
Artigo em Inglês | MEDLINE | ID: mdl-36901984

RESUMO

The metabolic syndrome is a cluster of overlapping conditions resulting in an increased incidence of type 2 diabetes, cardiovascular disease, and cancer. In the last few decades, prevalence of the metabolic syndrome in the Western world has reached epidemic proportions and this is likely due to alterations in diet and the environment as well as decreased physical activity. This review discusses how the Western diet and lifestyle (Westernization) has played an important etiological role in the pathogenesis of the metabolic syndrome and its consequences by exerting negative effects on activity of the insulin-insulin-like growth factor-I (insulin-IGF-I) system. It is further proposed that interventions that normalize/reduce activity of the insulin-IGF-I system may play a key role in the prevention and treatment of the metabolic syndrome. For successful prevention, limitation, and treatment of the metabolic syndrome, the focus should be primarily on changing our diets and lifestyle in accordance with our genetic make-up, formed in adaptation to Paleolithic diets and lifestyles during a period of several million years of human evolution. Translating this insight into clinical practice, however, requires not only individual changes in our food and lifestyle, starting in pediatric populations at a very young age, but also requires fundamental changes in our current health systems and food industry. Change is needed: primary prevention of the metabolic syndrome should be made a political priority. New strategies and policies should be developed to stimulate and implement behaviors encouraging the sustainable use of healthy diets and lifestyles to prevent the metabolic syndrome before it develops.


Assuntos
Diabetes Mellitus Tipo 2 , Síndrome Metabólica , Criança , Humanos , Insulina , Fator de Crescimento Insulin-Like I/metabolismo , Insulina Regular Humana , Transdução de Sinais
18.
Phys Rev Lett ; 129(23): 237202, 2022 Dec 02.
Artigo em Inglês | MEDLINE | ID: mdl-36563188

RESUMO

Competition among exchange interactions is able to induce novel spin correlations on a bipartite lattice without geometrical frustration. A prototype example is the spiral spin liquid, which is a correlated paramagnetic state characterized by subdimensional degenerate propagation vectors. Here, using spectral graph theory, we show that spiral spin liquids on a bipartite lattice can be approximated by a further-neighbor model on the corresponding line-graph lattice that is nonbipartite, thus broadening the space of candidate materials that may support the spiral spin liquid phases. As illustrations, we examine neutron scattering experiments performed on two spinel compounds, ZnCr_{2}Se_{4} and CuInCr_{4}Se_{8}, to demonstrate the feasibility of this new approach and expose its possible limitations in experimental realizations.

19.
Phys Rev Lett ; 129(13): 137202, 2022 Sep 23.
Artigo em Inglês | MEDLINE | ID: mdl-36206423

RESUMO

The experimental realization of magnetic skyrmion crystals in centrosymmetric materials has been driven by theoretical understanding of how a delicate balance of anisotropy and frustration can stabilize topological spin structures in applied magnetic fields. Recently, the centrosymmetric material Gd_{2}PdSi_{3} was shown to host a field-induced skyrmion crystal, but the skyrmion stabilization mechanism remains unclear. Here, we employ neutron-scattering measurements on an isotopically enriched polycrystalline Gd_{2}PdSi_{3} sample to quantify the interactions that drive skyrmion formation. Our analysis reveals spatially extended interactions in triangular planes, and large ferromagnetic interplanar magnetic interactions that are modulated by the Pd/Si superstructure. The skyrmion crystal emerges from a zero-field helical magnetic order with magnetic moments perpendicular to the magnetic propagation vector, indicating that the magnetic dipolar interaction plays a significant role. Our experimental results establish an interaction space that can promote skyrmion formation, facilitating identification and design of centrosymmetric skyrmion materials.

20.
Int J Mol Sci ; 23(15)2022 Jul 25.
Artigo em Inglês | MEDLINE | ID: mdl-35897752

RESUMO

Recent data suggests that (pre)diabetes onset is preceded by a period of hyperinsulinemia. Consumption of the "modern" Western diet, over-nutrition, genetic background, decreased hepatic insulin clearance, and fetal/metabolic programming may increase insulin secretion, thereby causing chronic hyperinsulinemia. Hyperinsulinemia is an important etiological factor in the development of metabolic syndrome, type 2 diabetes, cardiovascular disease, polycystic ovarian syndrome, and Alzheimer's disease. Recent data suggests that the onset of prediabetes and diabetes are preceded by a variable period of hyperinsulinemia. Emerging data suggest that chromic hyperinsulinemia is also a driving force for increased activation of the hypothalamic-adrenal-pituitary (HPA) axis in subjects with the metabolic syndrome, leading to a state of "functional hypercortisolism". This "functional hypercortisolism" by antagonizing insulin actions may prevent hypoglycemia. It also disturbs energy balance by shifting energy fluxes away from muscles toward abdominal fat stores. Synergistic effects of hyperinsulinemia and "functional hypercortisolism" promote abdominal visceral obesity and insulin resistance which are core pathophysiological components of the metabolic syndrome. It is hypothesized that hyperinsulinemia-induced increased activation of the HPA axis plays an important etiological role in the development of the metabolic syndrome and its consequences. Numerous studies have demonstrated reversibility of hyperinsulinemia with lifestyle, surgical, and pharmaceutical-based therapies. Longitudinal studies should be performed to investigate whether strategies that reduce hyperinsulinemia at an early stage are successfully in preventing increased activation of the HPA axis and the metabolic syndrome.


Assuntos
Síndrome de Cushing , Diabetes Mellitus Tipo 2 , Síndrome Metabólica , Síndrome de Cushing/metabolismo , Diabetes Mellitus Tipo 2/metabolismo , Humanos , Sistema Hipotálamo-Hipofisário/metabolismo , Insulina/metabolismo , Insulina Regular Humana , Síndrome Metabólica/metabolismo , Obesidade/metabolismo , Sistema Hipófise-Suprarrenal/metabolismo
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA