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1.
Lung Cancer ; 192: 107831, 2024 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-38805902

RESUMO

OBJECTIVES: This study aims to investigate the association between DNA double-strand breaks (DSBs) repair capacity, variations in DSBs-related genes, and the occurrence and prognosis of lung cancer in the Chinese population. METHODS: Peripheral blood mononuclear cells (PBMC) were collected from 98 lung cancer patients and 60 healthy individuals. The individual DSBs repair capacity was assessed by measuring changes in γ-H2AX levels after treatment with etoposide. Exonic sequencing of 45 DSBs-related genes was performed on PBMC DNA. Logistic regression analysis was conducted to examine the relationship between lung cancer risk and DSBs repair capacity as well as germlines gene variations. Survival analysis employed the Cox proportional hazards regression model, Kaplan-Meier method, and Log-rank test. RESULTS: Lower DSBs repair capacity predicted an increased risk of developing lung cancer (OR = 0.94, 95 %CI = 0.917-0.964, P<0.001). Among lung cancer patients, higher DSBs repair capacity was associated with shorter progression-free survival (PFS) during first-line treatment (HR = 1.80, 95 %CI = 1.10-3.00, P = 0.031). Patients with BRCA1 mutations had shorter overall survival (OS) (HR = 1.92, 95 %CI = 1.12-3.28, P = 0.018). Patients with FOXO3 mutations had shorter PFS (HR = 4.23, 95 %CI = 1.44-12.36, P = 0.009). Analysis of patients treated with immune checkpoint inhibitors (ICIs) indicated that LIG4 mutations were associated with shorter PFS (HR = 2.90, 95 %CI = 1.00-8.10, P = 0.041). CONCLUSIONS: This study concludes that assessing DSBs repair capacity holds promise for predicting both lung cancer risk and prognosis in the Chinese population. Further large-scale studies and functional validation of specific gene mutations related to double-strand breaks are necessary for confirmation.


Assuntos
Quebras de DNA de Cadeia Dupla , Reparo do DNA , Neoplasias Pulmonares , Humanos , Neoplasias Pulmonares/genética , Neoplasias Pulmonares/mortalidade , Neoplasias Pulmonares/patologia , Neoplasias Pulmonares/tratamento farmacológico , Feminino , Masculino , Prognóstico , Pessoa de Meia-Idade , Reparo do DNA/genética , Idoso , Biomarcadores Tumorais/genética , Predisposição Genética para Doença , Leucócitos Mononucleares/metabolismo , Fatores de Risco
2.
Exp Neurol ; 374: 114718, 2024 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-38336285

RESUMO

Executive function, including working memory, attention and inhibitory control, is crucial for decision making, thinking and planning. Lisdexamfetamine, the prodrug of d-amphetamine, has been approved for treating attention-deficit hyperactivity disorder and binge eating disorder, but whether it improves executive function under non-disease condition, as well as the underlying pharmacokinetic and neurochemical properties, remains unclear. Here, using trial unique non-matching to location task and five-choice serial reaction time task of rats, we found lisdexamfetamine (p.o) enhanced spatial working memory and sustained attention under various cognitive load conditions, while d-amphetamine (i.p) only improved these cognitive performances under certain high cognitive load condition. Additionally, lisdexamfetamine evoked less impulsivity than d-amphetamine, indicating lower adverse effect on inhibitory control. In vivo pharmacokinetics showed lisdexamfetamine produced a relative stable and lasting release of amphetamine base both in plasma and in brain tissue, whereas d-amphetamine injection elicited rapid increase and dramatical decrease in amphetamine base levels. Microdialysis revealed lisdexamfetamine caused lasting release of dopamine within the medial prefrontal cortex (mPFC), whereas d-amphetamine produced rapid increase followed by decline to dopamine level. Moreover, lisdexamfetamine elicited more obvious efflux of noradrenaline than that of d-amphetamine. The distinct neurochemical profiles may be partly attributed to the different action of two drugs to membranous catecholamine transporters level within mPFC, detecting by Western Blotting. Taken together, due to its certain pharmacokinetic and catecholamine releasing profiles, lisdexamfetamine produced better pharmacological action to improving executive function. Our finding provided valuable evidence on the ideal pharmacokinetic and neurochemical characteristics of amphetamine-type psychostimulants in cognition enhancement.


Assuntos
Estimulantes do Sistema Nervoso Central , Dimesilato de Lisdexanfetamina , Ratos , Animais , Dimesilato de Lisdexanfetamina/farmacologia , Função Executiva , Dopamina , Estimulantes do Sistema Nervoso Central/efeitos adversos , Dextroanfetamina/efeitos adversos , Dextroanfetamina/farmacocinética , Anfetamina/farmacologia , Catecolaminas , Cognição
3.
Parasit Vectors ; 16(1): 280, 2023 Aug 14.
Artigo em Inglês | MEDLINE | ID: mdl-37580819

RESUMO

BACKGROUND: Inflammatory bowel disease (IBD), including Crohn's disease (CD) and ulcerative colitis (UC), is increasing worldwide. Although there is currently no completely curative treatment, helminthic therapy shows certain therapeutic potential for UC. Many studies have found that Trichinella spiralis (T.s) has a protective effect on UC, but the specific mechanism is still unclear. METHODS: Balb/c mice drank dextran sulfate sodium (DSS) to induce acute colitis and then were treated with T.s. In vitro experiments, the LPS combination with ATP was used to induce the pyroptosis model, followed by intervention with crude protein from T.s (T.s cp). Additionally, the pyroptosis agonist of NSC or the pyroptosis inhibitor vx-765 was added to intervene to explore the role of pyroptosis in DSS-induced acute colitis. The degree of pyroptosis was evaluated by western blot, qPCR and IHC, etc., in vivo and in vitro. RESULTS: T.s intervention significantly inhibited NLRP3 inflammasome activation and GSDMD-mediated pyroptosis by downregulating the expression of pyroptosis-related signatures in vitro (cellular inflammatory model) and in vivo (DSS-induced UC mice model). Furthermore, blockade of GSDMD-mediated pyroptosis by the caspase-1 inhibitor vx-765 has a similar therapeutic effect on DSS-induced UC mice with T.s intervention, thus indicating that T.s intervention alleviated DSS-induced UC in mice by inhibiting GSDMD-mediated pyroptosis. CONCLUSION: This study showed that T.s could alleviate the pathological severity UC via GSDMD-mediated pyroptosis, and it provides new insight into the mechanistic study and application of helminths in treating colitis.


Assuntos
Colite Ulcerativa , Colite , Gasderminas , Doenças Inflamatórias Intestinais , Trichinella spiralis , Animais , Camundongos , Colite/induzido quimicamente , Colite Ulcerativa/induzido quimicamente , Colite Ulcerativa/tratamento farmacológico , Sulfato de Dextrana/toxicidade , Modelos Animais de Doenças , Camundongos Endogâmicos C57BL , Piroptose
4.
SN Bus Econ ; 3(1): 33, 2023.
Artigo em Inglês | MEDLINE | ID: mdl-36684689

RESUMO

This paper aims to analyze the articles regarding the role of good governance in sustainable tourism for China. Following the PRISMA guidelines, a systematic literature review approach has been conducted in this paper. A total number of 100 peer-reviewed journal papers have been critically evaluated. Our review analysis shows that taking necessary steps under good governance can promote sustainable tourism development in China. Few policy recommendations and future research aspects have also been included in the paper. Supplementary Information: The online version contains supplementary material available at 10.1007/s43546-022-00408-x.

6.
Sci Rep ; 12(1): 20442, 2022 11 28.
Artigo em Inglês | MEDLINE | ID: mdl-36443338

RESUMO

An enriched environment (EE) is a promising strategy for protecting the intestinal mucosal barrier and regulating the brain-gut axis, but the optimal EE intervention duration is unknown. Here, different EE intervention durations were applied to assess the optimal intervention duration in rats with colorectal cancer. We used a rat model of 1, 2-dimethylhydrazine-induced colorectal cancer. The rats were housed in an EE for 0, 2, 4, 8 weeks and 8-week blank group. The intestinal mucosa and serum TNF-α, IL-6, IL-10, ATP, CRF, and occludin levels and bacterial translocation (BT) were measured, and the intestinal mucosa morphology was evaluated. In 8 weeks, the effect of tumor on intestinal mucosal barrier was not obvious and the EE had a greater impact on it. Eight weeks of EE was more beneficial to the intestinal mucosal mechanical barrier than 2 or 4 weeks of intervention. A significant difference in BT was found between the 4- and 8-week groups. Overall, the analysis of inflammatory factor regulation revealed that the two blank groups exhibited the worst effect, and the intervention effect at 8 weeks was better than that at 2 and 4 weeks. CRF at 4 weeks was higher than that at 8-week blank group. The effect of 8-week intervention duration on the intestinal mucosal barrier was generally better than that of 2- and 4-week durations and intervention within 4 weeks can help to stabilize and promote the secretion of brain gut peptide, but the effect of different intervention durations on the brain-gut peptide levels was not obvious. In the future, we can further explore the molecular biological mechanism of the effect of different EE intervention durations on the intestinal mucosal barrier and analyze the effect of an EE on other brain-gut peptides.


Assuntos
Eixo Encéfalo-Intestino , Neoplasias Colorretais , Animais , Ratos , Translocação Bacteriana , Mucosa Intestinal , Ocludina , Neoplasias Colorretais/induzido quimicamente , Neoplasias Colorretais/terapia
7.
Parasit Vectors ; 15(1): 364, 2022 Oct 12.
Artigo em Inglês | MEDLINE | ID: mdl-36224608

RESUMO

BACKGROUND: There is presently no effective and safe vaccine for Toxoplasma gondii for humans. The study described here was designed to search for a novel group of optimal B cell and T cell epitopes from Toxoplasma membrane proteins using genome-wide comprehensive screening. METHODS: The amino acid sequences of membrane proteins of T. gondii were obtained from the UniProt database. The ABCPred and BepiPred servers were employed to predict the linear B cell epitopes. The Immune Epitope Database (IEDB) online service was utilized to forecast T cell epitopes within T. gondii membrane proteins that bind to human leukocyte antigen (HLA) class I (HLA-I) or HLA-II molecules. RESULTS: From the 314 membrane proteins of T. gondii, a total of 14 linear B cell epitopes embedded in 12 membrane proteins were identified. Eight epitopes for major histocompatibility complex (MHC) class I (MHC-I) molecules and 18 epitopes for MHC-II molecules were ultimately selected, for which world population coverage percentiles were 71.94% and 99.76%, respectively. The top rated combinations of linear B cell epitopes and T cell epitopes covering both BALB/c mice and a majority of the human population were identified for the development of a protective vaccine. CONCLUSIONS: The ultimate vaccine construct described here, which comprises B cells, MHC-I and MHC-II epitopes, might protect individuals against T. gondii infection by inducing humoral and cellular immune responses.


Assuntos
Toxoplasma , Vacinas , Animais , Epitopos de Linfócito B/genética , Epitopos de Linfócito T/genética , Antígenos de Histocompatibilidade Classe II , Humanos , Proteínas de Membrana/genética , Camundongos , Camundongos Endogâmicos BALB C , Toxoplasma/genética
8.
World J Clin Cases ; 10(14): 4661-4668, 2022 May 16.
Artigo em Inglês | MEDLINE | ID: mdl-35663055

RESUMO

BACKGROUND: Papillary thyroid carcinoma (PTC) is the most common endocrine malignancy. Papillary thyroid microcarcinoma (PTMC) accounts for the majority of PTC cases. However, concurrent pulmonary and hepatic metastases of PTMC are rarely seen. Here, we present a patient with coexisting liver and lung metastases from PTMC. CASE SUMMARY: We describe a 26-year-old woman with PTMC with multiple concurrent metastases. After 3 d of unexplained fever, she was admitted to our hospital. Her thyroid functional tests were abnormal. Her positron emission tomography (PET)/magnetic resonance imaging (MRI) examination showed increased fluorodeoxyglucose (FDG) metabolism and space-occupying lesions in the left lobe of the thyroid. Additionally, PET/MRI images revealed multiple nodules in the lung and liver with increased FDG metabolism. Chest computer tomography (CT) showed multiple pulmonary metastases. Abdominal ultrasound and liver MRI showed multiple space-occupying lesions in the liver. The patient underwent total thyroidectomy and central lymph node dissection. Postoperative pathological analysis showed a papillary microcarcinoma multiplex in the left lobe of the thyroid. A diagnosis of hepatopulmonary metastases from papillary thyroid microcarcinoma was made. The patient was given iodine-131 treatment one year after the surgery. She recovered well after the operation, and the incision healed well. After discharge, she was treated with oral levothyroxine sodium tablets, and symptomatic and supportive treatments were also given to promote radioactive excretion and prevent bone marrow suppression by iodine-131 treatment. CONCLUSION: Since patients with thyroid cancer concurrent with hepatopulmonary metastases have rarely been reported, our case will highlight the clinical and pathological profiles of these patients.

9.
Front Psychiatry ; 13: 885574, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-35558431

RESUMO

D-amphetamine has been used to enhance cognitive performance over the last few decades. Due to the rapid absorption after administration, d-amphetamine shows narrow effective window and severe abuse potential. Lisdexamfetamine, a prodrug of d-amphetamine, reduces the magnitude of plasma d-amphetamine concentration and prolongs the action duration when compared with immediate-release d-amphetamine at equimolar doses. However, the differences of these two drugs, which produce distinct pharmacokinetic characteristics, in cognition improvement still unclear. In present study, we compared the effects of d-amphetamine (i.p) and lisdexamfetamine (p.o) at equimolar doses (0.2, 0.5, 1.5, 4.5, and 13.5 mg/kg of d-amphetamine base) on locomotion, spatial working memory and recognition memory in rats. Given the crucial involvement of dopamine neurotransmitter system within the medial prefrontal cortex (mPFC) in cognitive processing, microdialysis was conducted to profile the difference in neurochemical characteristics between the two drugs. In our results, d-amphetamine ranges from 0.5 to 1.5 mg/kg significantly increased locomotor activity. However, d-amphetamine ranges from 0.2 to 13.5 mg/kg failed to improve spatial working memory and recognition memory in Y-maze-based spontaneous alternation and two-trial delayed alternation tasks of rats, respectively. In contrast, lisdexamfetamine with 4.5 mg/kg significantly increased the locomotion and improved both spatial working and recognition memory. Further, microdialysis showed that lisdexamfetamine induced lower magnitude and longer duration of extracellular dopamine increase than that of d-amphetamine. These results suggest that lisdexamfetamine was more effective than d-amphetamine in improving spatial cognitive performance, which was attributed to the steady and lasting dopamine release pattern within the mPFC.

10.
J Complement Integr Med ; 19(4): 817-826, 2022 Dec 01.
Artigo em Inglês | MEDLINE | ID: mdl-34187114

RESUMO

To date, there is no quantitative review examining the influence of heart rate variability biofeedback (HRV BFB) on the athlete population. Such an undertaking may provide valuable information on the autonomic and respiration responses of athletes when performing HRV BFB. Thus, purpose of this preliminary systematic review and meta-analysis on the effects of HRV BFB on HRV and respiration of athletes. Searches of Springerlink, SportDiscus, Web of Science, PROQUEST Academic Research Library, Google Scholar, and ScienceDirect were conducted for studies that met the following criteria: (1) experimental studies involving athletes that underwent randomized control trial; (2) availability of HRV BFB as a treatment compared with a control (CON)/placebo (PLA); (3) any pre and post HRV variable and/or breathing frequency as dependent variable/s; and, (4) peer-reviewed articles written in English. Four out of 660 studies involving 115 athletes (25 females and 90 males) ages 16-30 years old were assessed in this review. Preliminary findings suggest the promising ability of HRV BFB to improve respiratory mechanics in athlete population. More work is needed to determine the autonomic modulatory effect of HRV BFB in athletes.

11.
Pestic Biochem Physiol ; 175: 104859, 2021 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-33993955

RESUMO

Vanillin is a natural antimicrobial agent; however, there are few reports on its antifungal effect on postharvest pathogenic fungi. This study aimed to investigate the in vivo and in vitro antifungal activities of vanillin against gray mold (caused by B. cinerea) and black rot (caused by A. alternata) of cherry tomato fruit and to explain its possible mechanism of action. Vanillin strongly inhibits Botrytis cinerea and Alternaria alternata mycelial growth, spore germination, and germ tube elongation in a concentration-dependent manner (P<0.05). In vivo experiments showed that 4000 mg L-1 vanillin treatment inhibited cherry tomato gray mold and black rot occurrence. Besides, intercellular electrolytes, soluble proteins, and soluble sugars leakage indicated that 50 or 100 mg L-1 vanillin treatment increased Botrytis cinerea and Alternaria alternata membrane permeability. The increase of malondialdehyde and hydrogen peroxide contents confirmed that 50 or 100 mg L-1 vanillin treatment damages the pathogen membranes. Importantly, vanillin treatment inhibited the pathogenicity-related enzyme activities of the two pathogens to reduce their infection ability, among them PL enzyme activity in A. alternata was most inhibited, reducing by 94.7 % at 6 h treated with 100 mg L-1 vanillin. The hyphae morphology of the two pathogens changed, the mycelia were severely damaged, and the hyphae surface was deformed, shrunk, or even broken after 100 mg L-1 vanillin treatment. In summary, vanillin had a substantial inhibitory effect on postharvest gray mold and black rot in cherry tomato fruit. Therefore, vanillin can be an effective alternative to prevent and control cherry tomato postharvest diseases.


Assuntos
Solanum lycopersicum , Alternaria , Benzaldeídos , Botrytis , Frutas , Doenças das Plantas
12.
Spectrochim Acta A Mol Biomol Spectrosc ; 71(2): 714-9, 2008 Nov 15.
Artigo em Inglês | MEDLINE | ID: mdl-18337165

RESUMO

The electron paramagnetic resonance (EPR) parameters (g factors g parallel, g perpendicular and hyperfine structure constants A parallel, A perpendicular) for Co2+ ions in LiNbO3 and LiTaO3 crystals are calculated from the second-order perturbation formulas based on the cluster approach for 3d7 ions in trigonal octahedral clusters. The calculated results are in reasonable agreement with the experimental values. From the calculations, the negative sign of A parallel for Co2+ in the two crystals and the more exact and rational values of A parallel for Co2+ in LiTaO3 are suggested. The defect structures (characterized by the Co2+ displacement DeltaZ along C3 axis and the O(2-) displacement DeltaX in an oxygen triangle towards the center of the triangle) for the Co2+ centers in both crystals are estimated. The results are discussed.


Assuntos
Cobalto/química , Lítio/química , Nióbio/química , Óxidos/química , Tantálio/química , Cátions Bivalentes/química , Cristalização , Espectroscopia de Ressonância de Spin Eletrônica
13.
Spectrochim Acta A Mol Biomol Spectrosc ; 71(2): 417-20, 2008 Nov 15.
Artigo em Inglês | MEDLINE | ID: mdl-18280780

RESUMO

The electron paramagnetic resonance (EPR) zero-field splittings (ZFSs) D of Mn2+ in ZnGeP2 and CdGeP2 crystals are calculated from both the microscopic spin-orbit coupling mechanism and the empirical superposition model. From the calculations, the ZFS D of ZnGeP2:Mn2+ is reasonably explained by using the local tilting angle tauMn2+ (rather than the corresponding angle tauZn2+ in the host crystal) and the local tilting angle tauMn2+ (which has not been reported) in CdGeP2:Mn2+ is estimated. The intrinsic ZFS parameter b2(R0) approximately -0.052(6)cm(-1) (with R0 approximately 2.43 angstroms) is suggested for Mn2+-P(3-) combination by using the local tilting angles tauMn2+. The value is quite unlike that (approximately 0.4(2)cm(-1)) obtained in the previous paper by combining the crystallographic data of host crystals with the ZFSs for Mn2+ ions in crystals. The reasonableness of these results is discussed.


Assuntos
Cádmio/química , Germânio/química , Manganês/química , Fosfinas/química , Zinco/química , Cátions Bivalentes/química , Cristalização , Modelos Químicos
14.
Spectrochim Acta A Mol Biomol Spectrosc ; 71(3): 739-42, 2008 Dec 01.
Artigo em Inglês | MEDLINE | ID: mdl-18280786

RESUMO

The high-order perturbation formulas of spin-Hamiltonian (SH) parameters (g factors g( parallel), g( perpendicular) and zero-field splitting D) for 3d(8) ions in trigonal octahedral sites of crystals are derived considering not only the crystal-field (CF) mechanism, but also the charge-transfer (CT) mechanism (which is neglected in the extensively used CF theory). From these formulas and by considering the suitable impurity-induced local lattice relaxation, the SH parameters of CsCdX(3):Ni(2+) (X=Cl, Br) crystals are calculated. The results are in reasonable agreement with the experimental values. The sign of Q(CT) (Q=Deltag( parallel), Deltag( perpendicular) or D, where the g-shift Deltag(i)=g(i)-g(e), g(e) approximately 2.0023 is the free-electron value) due to CT mechanism is the same as that of the corresponding Q(CF) due to CF mechanism. The relative importance of CT mechanism (characterized by Q(CT)/Q(CF)) increases with the increasing atomic number of ligand X. So, for 3d(n) ion clusters in crystals with heavy element ligand ion (e.g., Br(-)), the reasonable explanations of SH parameters should contain the contributions from both CF and CT mechanisms.


Assuntos
Cádmio/química , Césio/química , Níquel/química , Brometos/química , Cloretos/química , Cristalização , Espectroscopia de Ressonância de Spin Eletrônica , Modelos Químicos , Marcadores de Spin
15.
Artigo em Inglês | MEDLINE | ID: mdl-16829175

RESUMO

The EPR parameters (zero-field splitting D and g factors g parallel, g perpendicular) of Mn5+ -doped Li3PO4 and Li3VO4 crystals are calculated from the complete high-order perturbation formulas based on a molecular orbital scheme for a 3d2 ion in tetragonal MX4 clusters. These formulas include not only the contribution coming from crystal-field excitations, but also that arising from charge-transfer excitations (which is discarded in crystal field theory). The calculated results are in reasonable agreement with the observed values. The contributions to EPR parameters coming from the charge-transfer excitations are comparable with those arising from the crystal-field excitations. It appears that for a high valence state 3dn ion in crystals, the reasonable explanations of EPR parameters should take the contributions due to both crystal-field and charge-transfer excitations into account.


Assuntos
Compostos de Lítio/química , Manganês/química , Compostos de Vanádio/química , Espectroscopia de Ressonância de Spin Eletrônica/métodos
16.
Artigo em Inglês | MEDLINE | ID: mdl-16344247

RESUMO

The EPR parameters (zero-field splitting D and g factors g(parallel), g(perpendicular)) and the first excited state splitting Delta(2E) of the trigonal Cr3+-Vc centers (Vc denotes the cation vacancy in a C3 axis) in Cr3+-doped fluoroperovskites KMgF3, KZnF3, CsCdF3, CsCaF3, RbCdF3 and BaLiF3 are studied from the high-order perturbation formulas. From the studies, the defect structures (characterized by the vacancy-induced displacements Delta x1 of Cr3+ ion and Delta x2 of the three F- ion between Cr3+ and Vc) of these trigonal Cr3+-Vc centers are determined. It is found that the signs of displacements Delta x1 and Delta x2 are consistent with the expectations based on the electrostatic interactions, and the magnitudes of Delta x1 and Delta x2 for Cr3+ in the inverse perovskite BaLiF3 are larger than those for Cr3+ in the classical perovskites. The results are discussed.


Assuntos
Compostos de Cálcio/química , Cromo/química , Fluoretos/química , Óxidos/química , Titânio/química , Espectroscopia de Ressonância de Spin Eletrônica , Estrutura Molecular
17.
Spectrochim Acta A Mol Biomol Spectrosc ; 62(4-5): 769-72, 2005 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-16103006

RESUMO

From the high-order perturbation formulas of EPR parameters (zero-field splitting D, g factors gparallel, gperpendicular and hyperfine structure constants Aparallel, Aperpendicular) based on the two spin-orbit coupling parameter model for 3d3 ions in trigonal symmetry, the EPR parameters of Cr3+ and V2+ ions in HfS2 crystals are calculated. From the calculations, it is found that the local trigonal distortion angle theta of impurity center in HfS2:Cr3+ is smaller than that in HfS2:V2+. The dominant cause of the small zero-field splitting |D| and g-anisotropy |Deltag|=|gparallel-gperpendicular| in HfS2:Cr3+ (compound to HfS2:V2+) is due to the small local trigonal distortion angle theta rather than to the small impurity-ligand distance R in HfS2:Cr3+.


Assuntos
Cromo/química , Espectroscopia de Ressonância de Spin Eletrônica/métodos , Compostos de Enxofre/química , Vanádio/química , Cristalização , Íons/química , Modelos Químicos
18.
Spectrochim Acta A Mol Biomol Spectrosc ; 61(11-12): 2720-3, 2005 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-16043069

RESUMO

The axial Ti2+ center in a nearly wholly cubic ZnS crystal is assigned to the Ti2+ ion on the hexagonal site of wurtzite structure caused by stacking faults. On the ground of the assignment, the EPR parameters (zero-field splitting D, g factor g( parallel) and g-anisotropy Deltag=g( parallel)-g( perpendicular)) of the axial Ti2+ center are calculated from the high-order perturbation formulas based on the cluster approach for the EPR parameters of 3d2 ion in trigonal symmetry. From the calculations, the local atom-position parameter u(loc) (which is different from the corresponding parameter u in the host wurtzite structure) and hence the defect structure of the Ti2+ center are estimated. The results (the calculated EPR parameters and the defect structure) are discussed.


Assuntos
Cátions Bivalentes/química , Titânio/química , Sulfato de Zinco/química , Carbono/química , Cobalto/química , Espectroscopia de Ressonância de Spin Eletrônica , Hidrogênio/química
19.
Artigo em Inglês | MEDLINE | ID: mdl-15741128

RESUMO

The calculations of EPR parameters (g factors g||, g(perpendicular) and zero-field splitting D) related to the impurity structures have been made from the high-order perturbation formulas for Cr(3+) ions in trigonal KSc(MoO(4))(2), RbIn(MoO(4))(2) and RbSc(MoO(4))(2) crystals. It is found that the MO(6) octahedra in these crystals change from the trigonal elongation in the pure crystals to the trigonal compression in the impurity centers. The results are discussed.


Assuntos
Cromo/química , Espectroscopia de Ressonância de Spin Eletrônica , Índio/química , Molibdênio/química , Compostos de Potássio/química , Rubídio/química , Cristalização , Matemática
20.
Artigo em Inglês | MEDLINE | ID: mdl-15683795

RESUMO

The zero-field splittings induced by the electric-field have been studied theoretically from the formulas, including three important microscopic mechanisms for a substitutional Mn2+ ion in SrCl2 crystal. From the studies, it is found that the zero-field splitting can be attributed primarily to the electric-field-induced displacement of Mn2+ ion along the electric-field direction and the magnitudes of the displacements at various strengths of electric-field are obtained. The results are comparable with those obtained from the potential-energy curve of Mn2+ center.


Assuntos
Manganês/química , Estrôncio/química , Cristalografia , Interpretação Estatística de Dados , Espectroscopia de Ressonância de Spin Eletrônica
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