Your browser doesn't support javascript.
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 344
Filtrar
1.
J Craniofac Surg ; 2020 Jun 24.
Artigo em Inglês | MEDLINE | ID: mdl-32604309

RESUMO

Chondroma in the area of the spheno-ethmoidal junction is very rare. A 29-year-old male patient with chronic rhinosinusitis with nasal polyps was arranged for a preoperative computed tomography scan, and a lesion was accidentally found in his spheno-ethmoidal junction and involved the skull base. Combined with MRI, the lesion was misdiagnosed as fungal sinusitis. However, no fungal lesions were found during the operation, and cartilage tissue was confirmed only after some bone was ground away under the guidance of a surgical navigation system. Our case indicates that chondroma is easily misdiagnosed as fungal sinusitis when it appears in the sinuses and should be carefully distinguished from fungal sinusitis. Moreover, when lesions involve the skull base, surgical navigation systems are useful in accurately locating lesions.

2.
Br J Nutr ; : 1-31, 2020 Jun 30.
Artigo em Inglês | MEDLINE | ID: mdl-32600494

RESUMO

The European Society for Clinical Nutrition and Metabolism (ESPEN) guidelines recommend Royal Free Hospital-Nutritional Prioritizing Tool (RFH-NPT) to identify malnutrition risk in patients with liver disease. However, little is known about the application of RFH-NPT to screen for the risk of malnutrition in China, where patients primarily suffer from hepatitis virus-related cirrhosis. A total of 155 cirrhosis patients without liver cancer or uncontrolled comorbid illness were enrolled in this prospective study. We administered the Nutritional Risk Screening 2002 (NRS-2002), RFH-NPT, Malnutrition Universal Screening Tool(MUST), and Liver Disease Undernutrition Screening Tool (LDUST) to the patients within 24 h after admission and performed follow-up observations for 1.5 years. The RFH-NPT and NRS-2002 had higher sensitivities (64.8% and 52.4%) and specificities (60% and 70%) than the other tools with regard to screening for the malnutrition risk in cirrhotic patients. The prevalence of nutritional risk was higher under the use of RFH-NPT against the NRS-2002(63% vs. 51%). RFH-NPT tended more easily to detect the malnutrition risk in patients with advanced Child-Pugh classes (B and C) and lower MELD scores (<15) compared with NRS-2002. The RFH-NPT score was an independent predictive factor for mortality. Patients identified as being at high malnutrition risk with the RFH-NPT had a higher mortality rate than those at a low risk; the same result was not obtained with the NRS-2002. Therefore, we suggest that using RFH-NPT improves the ability of clinicians to predict malnutrition risk in patients with cirrhosis primarily caused by hepatitis virus infection at an earlier stage.

3.
Artigo em Inglês | MEDLINE | ID: mdl-32601991

RESUMO

RATIONALE: Although a growing body of evidence indicates that the scores of cognitive function in hemodialysis patients are significantly lower than those of healthy individuals, underlying mechanisms have not been fully elucidated. OBJECTIVES: To investigate the roles of gut microbiota and serum metabolites in hemodialysis patients with mild cognitive decline (MCD). METHODS: A total of 30 healthy individuals and 77 hemodialysis patients were enrolled and were classified into healthy control (HC), normal cognitive function (NCF), and MCD groups by evaluation of Montreal Cognitive Assessment. Fecal samples were analyzed by 16S rRNA and serum samples were analyzed by gas chromatography-mass spectrometry from all subjects. RESULTS: The 16S rRNA study demonstrated that the gut microbiota profiles, including α- and ß-diversity, and a number of 16 gut bacteria were significantly altered in the MCD group compared with those in HC or those with NCF. A metabonomics study showed that a total of 29 serum metabolites were altered in the MCD group. Receiver operating characteristic curves showed that Genus Bilophila and serum putrescine might be sensitive biomarkers to indicate MCD in patients with hemodialysis. CONCLUSIONS: These findings demonstrate gut microbiota and serum metabolites were probably involved in the pathogenesis of hemodialysis-related MCD. Therapeutic strategies targeting abnormalities in gut microbiota and serum metabolites may facilitate the beneficial effects for hemodialysis patients with MCD.

4.
Ear Nose Throat J ; : 145561320922119, 2020 May 12.
Artigo em Inglês | MEDLINE | ID: mdl-32396389

RESUMO

BACKGROUND: The sphenoethmoidal cell and the sphenoid sinus (SS) show great similarity in endoscopy and imaging. Hence, it is important to accurately identify the sphenoethmoidal cell preoperatively to prevent injury of the nerve and artery during endoscopic surgery. The aim of the present study was to investigate a special type of sphenoethmoidal cell. METHODS: A total of 365 inpatients whose paranasal sinus computed tomography (CT) was collected and reviewed from May 2018 to September 2019 were included. The anatomical imaging characteristics of the sphenoethmoidal cell were observed. RESULTS: A special type of the sphenoethmoidal cell was found on 9 sides in 730 sides (1.3%), according to its extension to the SS. Unlike Onodi cell (49.6%) and Jinfeng cell (1.3%), this cell simultaneously extends toward the superolateral, lateral, and inferolateral regions of the SS and is simultaneously closely attached to the optic canal and the maxillary nerve. Presently, this cell is named as the whole lateral type of the sphenoethmoidal cell, and the SS is located at the medial or inferomedial of it. CONCLUSIONS: When evaluating the paranasal sinus CT preoperatively, attention must be paid to the possibility of the whole lateral type of sphenoethmoidal cell appearing, not just Onodi cell, extending into the SS.

5.
Epigenetics ; : 1-15, 2020 May 12.
Artigo em Inglês | MEDLINE | ID: mdl-32396412

RESUMO

Aberrant DNA methylation is significantly associated with the prognosis of patients with colorectal cancer (CRC). Therefore, the aim of this study was to develop a CpG-methylation-based nomogram for prognostic prediction in CRC. First, 378 CRC patients with methylation data from The Cancer Genome Atlas were randomly divided into training cohort (n = 249) and test cohort (n = 129). A multistep screening strategy was performed to identify six CpG sites that were significantly associated with overall survival in the training cohort. Then, Cox regression modelling was performed to construct a prognostic signature based on the candidate CpG sites. The six-CpG signature successfully separated patients into high-risk and low-risk groups in both training and test cohorts, and its performance was superior to that of previously published methylation markers (P < 0.05). Furthermore, we established a prognostic nomogram incorporating this signature, TNM stage, and age. The nomogram exhibited better prediction for overall survival in comparison with the three independent prognostic factors in the training cohort (C-index: 0.798 vs 0.620 to 0.737; P < 0.001). In the test cohort, the performance of nomogram was also superior to that of the three independent prognostic factors (C-index: 0.715 vs 0.590 to 0.665; P < 0.05). Meanwhile, the calibration curves for survival probability showed good agreement between prediction by nomogram and actual observation in both training and test cohorts. Together, the present study provides a novel CpG-methylation-based nomogram as a promising predictor for overall survival of CRC patients, which may help improve decision-making regarding the personalized treatments of patients with CRC.

6.
Phys Chem Chem Phys ; 22(22): 12341-12367, 2020 Jun 14.
Artigo em Inglês | MEDLINE | ID: mdl-32459230

RESUMO

To study large molecular systems beyond the system size that the current state-of-the-art ab initio electronic structure methods could handle, fragment-based quantum mechanical (QM) approaches have been developed over the past years, and proved to be efficient in dealing with large molecular systems at various ab initio levels. According to the fragmentation approach, a large molecular system can be divided into subsystems (fragments), and subsequently the property of the whole system can be approximately obtained by taking a proper combination of the corresponding terms of individual fragments. Therefore, the standard QM calculation of a large system could be circumvented by carrying out a series of calculations on small fragments, which significantly promotes computational efficiency. The electrostatically embedded generalized molecular fractionation with conjugate caps (EE-GMFCC) method is one of the fragment-based QM approaches which has been developed by our research group in recent years. This Perspective presents the theoretical framework of this fragmentation method and its applications in biomolecules, molecular clusters, molecular crystals and liquids, including total energy calculation, protein-ligand/protein binding affinity prediction, geometry optimization, vibrational spectrum simulation, ab initio molecular dynamics simulation, and prediction of excited-state properties.

7.
Anal Biochem ; 600: 113746, 2020 07 01.
Artigo em Inglês | MEDLINE | ID: mdl-32333904

RESUMO

Metabolite profiling in anaerobic alkane biodegradation plays an important role in revealing activation mechanisms. Apart from alkylsuccinates, which are considered to be the usual biomarkers via fumarate addition, the downstream metabolites of C-skeleton rearrangement can also be regarded as biomarkers. However, it is difficult to detect intermediate metabolites in both environmental samples and enrichment cultures, resulting in lacking direct evidence to prove the occurrence of fumarate addition pathway. In this work, a synthetic method of rearrangement metabolites was established. Four compounds, namely, propylmalonic acid, 2-(2-methylbutyl)malonic acid, 2-(2-methylpentyl)malonic acid and 2-(2-methyloctyl)malonic acid, were synthesized and determined by four derivatization approaches. Besides, their mass spectra were obtained. Four characteristic ions were observed at m/z 133 + 14n, 160 + 28n, 173 + 28n and [M - (45 + 14n)]+ (n = 0 and 2 for ethyl and n-butyl esters, respectively). For methyl esterification, mass spectral features were m/z 132, 145 and [M - 31]+, while for silylation, fragments were m/z 73, 147, 217, 248, 261 and [M - 15]+. These data provide basis on identification of potential rearrangement metabolites in anaerobic alkane biodegradation via fumarate addition.

8.
J Inorg Biochem ; 207: 111063, 2020 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-32222581

RESUMO

N-heterocyclic carbenes-modified half-sandwich iridium(III) complex [(η5-C5Me4C6H4C6H5)Ir(C^C)Cl]PF6 (C1) (where C^C is a N-heterocyclic carbene ligand) can effectively prevent the proliferation of human cervical cancer cells. Here, this study aims to investigate the in-deep anticancer effects of this complex on non-small cell lung cancer cells and explore the underlying molecular mechanism. MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay showed that iridium(III) complex had potent cytotoxicity studies towards non-small cell lung cancer cells (A549), human lung squamous cells (L78), human cervical cancer cells (Hela) and human bronchial epithelial cells (BEAS-2B). Colocalization and cellular uptake studies were analyzed by confocal microscopy. Notably, C1 targeted lysosomes and entered the cancer cells partially through an energy-dependent pathway, inducing the release of cathepsins and other proteins. These proteins regulated lysosomal-mitochondrial dysfunction, thus leading to the release of cytochrome c (cyt c), which amplified apoptotic signals by activating many downstream pathways such as caspase pathways to promote cell apoptosis. The results showed that the inhibitory mechanism of this organometallic iridium(III) complex may involve caspase-associated apoptosis initiated by the lysosomal-mitochondrial pathway.

9.
Artigo em Inglês | MEDLINE | ID: mdl-32167638

RESUMO

Full quantum mechanical (FQM) calculation of the excited state of aggregation-induced-emission (AIE) materials is highly sought but still a challenging task. Herein, we employed the recently developed electrostatically embedded generalized molecular fractionation (EE-GMF) method, a method based on the systematic fragmentation approach, to predict, for the first time, the spectra of a prototype AIE fluorophore: di(p-methoxylphenyl)dibenzofulvene (FTPE). Compared to the single molecular or QM/MM calculations, the EE-GMF method shows significantly improved accuracy, nearly reproducing the experimental optical spectra of FTPE in both condensed phases. Importantly, we show that the conventional restriction of the intramolecular rotation mechanism cannot fully account for AIE, whereas the two-body intermolecular quantum mechanical interaction plays a crucial role in AIE.

10.
Hepatol Int ; 14(2): 180-189, 2020 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-32193814

RESUMO

BACKGROUND: Several antiviral agents licenced for blocking mother-to-child transmission (MTCT) of HBV, but their relative efficacy beginning from different trimesters has scarce been evaluated. We aimed to conduct a network meta-analysis to statistically differ the efficacy and safety of each antiviral agents initiating on different timings in preventing mother-to-infant transmission of HBV. METHODS: Studies were included from PubMed, EMBASE, Web of Science, and Cochrane databases through July 1, 2019. Eligible studies recruited randomized controlled trials and nonrandomized studies reporting about infant or/and maternal efficacy and safety outcomes and were screened by two investigators independently. Extracted data were analyzed by pair-wised and network meta-analysis, respectively. RESULTS: 3 Randomized and 32 nonrandomized studies enrolling 6738 pregnant female were included. Using network analysis, any antiviral agent interrupted HBV vertical transmission much more effectively than placebo. No agent showed significant efficacy different from others, but a strong trend toward significance was found in telbivudine and tenofovir, of which had the highest probability of being ranked the first- or second-best treatment for reducing MTCT of HBV. The treatment applied in the first and second trimester had a similar efficacy in preventing MTCT. Compared with the initiation during the third trimester, lower rate of MTCT was revealed when antiviral therapy was administrated before third trimester, (RR = 0.045, 95% CI 0.0053 to 0.20); a similar effect at delivery on suppressing maternal HBV DNA level and converting serum HBeAg were achieved if the timing of antiviral treatment started prior, but an obvious improvement of normalizing ALT flare was calculated out; no statistically differences among maternal and fetal safety outcomes were found if mothers received antiviral agents before pregnant 28 weeks. CONCLUSION: This network meta-analysis recommended the earlier use of telbivudine or tenofovir, tends to be better to prevent MTCT of HBV in pregnancy with no increased adverse maternal or fetal outcomes.

11.
Women Birth ; 2020 Feb 26.
Artigo em Inglês | MEDLINE | ID: mdl-32113872

RESUMO

PROBLEM: The relationship between birthing related factors and breastfeeding confidence remain unknown among Chinese mothers. BACKGROUND: Breastfeeding confidence in the early postpartum period is an important predictor of breastfeeding duration. There are many postpartum and socio-demographic factors that have been linked to breastfeeding confidence. However, the relationship between birthing related factors and this confidence remain unknown. AIM: To explore the relationship between birthing related factors and breastfeeding confidence among Chinese mothers. METHODS: This is a cross-sectional study of 450 mothers who were recruited after birth and before discharge from hospital. From November 2018 to March 2019, we collected data related to socio-demographics and obstetric characteristics, as well as the Chinese version of Breastfeeding Self-Efficacy Scale and the Chinese version of Labor Agentry Scale. Associations of birthing related factors with breastfeeding self-efficacy were investigated. RESULTS: There was a significant correlation between perception of control during labor and breastfeeding confidence. Multiple linear regression showed that higher perception of control in labor scores were significantly associated with higher breastfeeding self-efficacy scores (B=0.282, P=<0.001), and lower breastfeeding self-efficacy scores were associated with women living in an extended family (B=-12.622, P=<0.001), perceived of insufficient milk supply (B=-5.514, P=0.038), mild fatigue (B=-8.021, P=0.03), moderate fatigue (B=-12.955, P=0.004). CONCLUSION: There is a significant relationship between perception of control during labor and maternal breastfeeding confidence in the early postpartum period. Strengthening perception of control during labor can improve breastfeeding self-efficacy. Providing professional and emotional support for women during the intrapartum period should be strengthened.

12.
Artigo em Inglês | MEDLINE | ID: mdl-32149632

RESUMO

We developed a high power piezoelectric characterization system, which was used to study the high-field properties PIN-PMN-PT relaxor ferroelectric single crystals and PZT-4 piezoelectric ceramics. The impedance spectrum of 31-mode was measured under constant voltage by the high power piezoelectric system. From measuring the resonance and anti-resonance frequencies, the high-field behaviors of the electromechanical coupling factors, elastic compliances and piezoelectric coefficients of the PIN-PMN-PT crystals were determined and compared with commercial PZT ceramics. By fitting the equivalent circuit parameters under large electric fields, the mechanical quality factors of the PIN-PMN-PT single crystals and PZT-4 ceramics were calculated as well. The results showed that the mechanical quality factor of the PZT-4 is higher than that of PIN-PMN-PT, and the mechanical quality factors of the PZT-4 and PIN-PMN-PT both decrease sharply first and then decrease slowly with increasing the electric field. The tensile strengths of PIN-PMN-PT crystals and PZT-4 ceramics were also determined by the impedance method, where we found that the tensile strengths of PIN-PMN-PT crystal and PZT-4 ceramic were 19.6 MPa and 76.4 MPa respectively. The 31-mode vibrators of PIN-PMN-PT crystals and PZT-4 ceramics can be driven by largest electric field of 33 V/mm and 65 V/mm under resonance frequency respectively.

13.
Paediatr Anaesth ; 30(5): 552-563, 2020 May.
Artigo em Inglês | MEDLINE | ID: mdl-32198961

RESUMO

BACKGROUND: A growing number of studies have demonstrated the effectiveness of acupuncture in preventing and treating postoperative nausea and vomiting. Here, we used meta-analysis to confirm these benefits in children and to determine the optimal time to perform this treatment. METHODS: Four databases (MEDLINE, EMBASE, CENTRAL, and Chinese Database of Biology and Medicine) were searched from inception until January 16, 2019. We included randomized controlled trials for evaluating the effectiveness of acupuncture in the prevention and treatment of postoperative nausea and vomiting during the early stage (0-4 hours) and within 24 hours postoperatively in pediatrics. Control groups received standardized care control or standardized care combined with sham control. RESULTS: Sixteen literatures and 1773 patients undergoing general anesthesia were included in the study. The results indicated that acupuncture was effective in reducing postoperative vomiting, both during the first 4 hours (RR = 0.47, 95% CI 0.26, 0.84; low quality) and within 24 hours postoperatively (RR = 0.74, 95% CI 0.60, 0.91; low quality). Stratifying by the timing of acupuncture, acupuncture was effective in reducing the first 4 hours (RR = 0.34, 95% CI 0.18, 0.64; moderate quality), and 0-24 hours postoperative vomiting (RR = 0.81, 95% CI 0.70, 0.93; moderate quality) when performed before and during anesthesia, respectively. Further, the RR value was more robust when acupuncture was performed before anesthesia. Acupuncture was also effective in treating 0-24 hours postoperative nausea (RR = 0.73, 95% CI 0.60, 0.88; moderate quality) and in reducing the utilization of remedies during the first 4 hours (RR = 0.64, 95% CI 0.45, 0.89; moderate quality). CONCLUSION: Acupuncture reduces the incidence of postoperative nausea and vomiting as well as the utilization of antiemetic remedies, particularly during the first 4 hours following the operation. Acupuncture performed before anesthesia was demonstrated to be the most ideal intervention time for children.

14.
J Phys Chem B ; 124(9): 1839-1846, 2020 Mar 05.
Artigo em Inglês | MEDLINE | ID: mdl-32083878

RESUMO

Biosurfactants exhibit outstanding interfacial properties and unique biological activities that fairly related to their self-assembly in solutions and at interfaces. Computational simulations provide structural details of biosurfactant aggregates at the molecular level relevant to thermodynamic properties, but the understanding of kinetics of self-assembly remains limited due to lower simulation efficiency. In this work, a coarse-grained model has been developed for microbial lipopeptide surfactin, and surfactin monolayer at the octane/water interface and micelle in aqueous solution were studied using molecular dynamics simulations. Interaction parameters were optimized and validated by comparing with results obtained from experiments and atomistic molecular dynamics simulations. In particular, self-assembly of surfactin in aqueous solution was studied using the optimized parameters. Results showed that coarse-grained simulations well reproduced structural properties of surfactin monolayer and micelle and the molecular behavior such as surfactin orientation and conformation. Self-assembly features of surfactin in different stages have been captured, and the aggregation numbers of dominant clusters were in accordance with experimental data. This report suggested that the present coarse-grained model and interaction parameters allowed surfactin simulations over longer timescales and larger systems, which provide insights into characterizing both the kinetics of surfactin self-assembly and the adsorption of surfactin onto varying interfaces.

15.
Biomed Eng Online ; 19(1): 9, 2020 Feb 12.
Artigo em Inglês | MEDLINE | ID: mdl-32050989

RESUMO

The organ-on-a-chip (OOAC) is in the list of top 10 emerging technologies and refers to a physiological organ biomimetic system built on a microfluidic chip. Through a combination of cell biology, engineering, and biomaterial technology, the microenvironment of the chip simulates that of the organ in terms of tissue interfaces and mechanical stimulation. This reflects the structural and functional characteristics of human tissue and can predict response to an array of stimuli including drug responses and environmental effects. OOAC has broad applications in precision medicine and biological defense strategies. Here, we introduce the concepts of OOAC and review its application to the construction of physiological models, drug development, and toxicology from the perspective of different organs. We further discuss existing challenges and provide future perspectives for its application.

16.
Methods Mol Biol ; 2114: 19-35, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32016884

RESUMO

Computational chemistry allows one to characterize the structure, dynamics, and energetics of protein-ligand interactions, which makes it a valuable tool in drug discovery in both academic research and pharmaceutical industry. Molecular mechanics (MM)-based approaches are widely utilized to assist the discovery of new drug candidates. However, the complexity of protein-ligand interactions challenges the accuracy and efficiency of the commonly used empirical methods. Aiming to provide better accuracy in the description of protein-ligand interactions, quantum mechanics (QM)-based approaches are becoming increasingly explored. In principle, QM calculation includes all contributions to the energy, accounting for terms usually missing in empirical force fields, and provides a greater degree of transferability. The usefulness of QM in drug design cannot be overemphasized. In this chapter, we present recent developments and applications of fragment-based QM method in studying the protein-ligand and protein-protein interactions. We critically discuss the performance of the fragment-based QM method at different ab initio levels while trying to answer a critical question: do QM-based methods really help in drug design?

17.
Nature ; 577(7790): 350-354, 2020 01.
Artigo em Inglês | MEDLINE | ID: mdl-31942055

RESUMO

Transparent piezoelectrics are highly desirable for numerous hybrid ultrasound-optical devices ranging from photoacoustic imaging transducers to transparent actuators for haptic applications1-7. However, it is challenging to achieve high piezoelectricity and perfect transparency simultaneously because most high-performance piezoelectrics are ferroelectrics that contain high-density light-scattering domain walls. Here, through a combination of phase-field simulations and experiments, we demonstrate a relatively simple method of using an alternating-current electric field to engineer the domain structures of originally opaque rhombohedral Pb(Mg1/3Nb2/3)O3-PbTiO3 (PMN-PT) crystals to simultaneously generate near-perfect transparency, an ultrahigh piezoelectric coefficient d33 (greater than 2,100 picocoulombs per newton), an excellent electromechanical coupling factor k33 (about 94 per cent) and a large electro-optical coefficient γ33 (approximately 220 picometres per volt), which is far beyond the performance of the commonly used transparent ferroelectric crystal LiNbO3. We find that increasing the domain size leads to a higher d33 value for the [001]-oriented rhombohedral PMN-PT crystals, challenging the conventional wisdom that decreasing the domain size always results in higher piezoelectricity8-10. This work presents a paradigm for achieving high transparency and piezoelectricity by ferroelectric domain engineering, and we expect the transparent ferroelectric crystals reported here to provide a route to a wide range of hybrid device applications, such as medical imaging, self-energy-harvesting touch screens and invisible robotic devices.

18.
Ear Nose Throat J ; : 145561319898940, 2020 Jan 07.
Artigo em Inglês | MEDLINE | ID: mdl-31910671

RESUMO

INTRODUCTION: Posttransplant lymphoproliferative disorder (PTLD) is a serious disease that usually occurs after solid organ transplant and stem cell transplant. Posttransplant lymphoproliferative disorder often involves the head and neck, but it is rare to present as a nasal deformity. Here, we describe a case of external nasal enlargement resulting from PTLD. CASE REPORT: A 40-year-old man presented with an enlarged external nose half a year ago. The nasal ala thickened, and the external nose was gradually enlarged, accompanied by bilateral nasal obstructions. A biopsy was taken under endoscopy procedure, and the result suggested a diagnosis of PTLD. DISCUSSION: Posttransplant lymphoproliferative disorder usually appears in lymphoid tissues that form Waldeyer's rings or cervical lymph nodes in the head and neck. The early involvement of other head and neck subpoints is considered rare. This case is the first report of PTLD presenting as an external nasal deformity. The symptoms and clinical manifestations of PTLD in otorhinolaryngology are usually diverse and nonspecific but are early symptoms in the clinical course of PTLD.

19.
Molecules ; 25(3)2020 Jan 23.
Artigo em Inglês | MEDLINE | ID: mdl-31979295

RESUMO

The behavior of ice under extreme conditions undergoes the change of intermolecular binding patterns and leads to the structural phase transitions, which are needed for modeling the convection and internal structure of the giant planets and moons of the solar system as well as H2O-rich exoplanets. Such extreme conditions limit the structural explorations in laboratory but open a door for the theoretical study. The ice phases IX and XIII are located in the high pressure and low temperature region of the phase diagram. However, to the best of our knowledge, the phase transition boundary between these two phases is still not clear. In this work, based on the second-order Møller-Plesset perturbation (MP2) theory, we theoretically investigate the ice phases IX and XIII and predict their structures, vibrational spectra and Gibbs free energies at various extreme conditions, and for the first time confirm that the phase transition from ice IX to XIII can occur around 0.30 GPa and 154 K. The proposed work, taking into account the many-body electrostatic effect and the dispersion interactions from the first principles, opens up the possibility of completing the ice phase diagram and provides an efficient method to explore new phases of molecular crystals.

SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA