Crystal genes in a marginal glass-forming system of Ni50Zr50

The marginal glass-forming ability (GFA) of a binary Ni-Zr system is an issue to be explained considering numerous bulk metallic glasses (BMGs) found in a Cu-Zr system. Using molecular dynamics, the structures and dynamics of Ni₅₀Zr₅₀ metallic liquid and glass are investigated at the atomistic level. To achieve a well-relaxed glassy sample, a sub-T_g annealing method is applied and the final sample is closer to the experiments than the models prepared by continuous cooling. With the state-of-the-art structural analysis tools such as cluster alignment and pair-wise alignment methods, two glass-forming motifs with some mixed traits of a metastable B2 crystalline phase and a crystalline Ni-centered B33 motif are found to be dominant in the undercooled liquid and glass samples. A new chemical order characterization on each short-range order (SRO) structure is accomplished based on the cluster alignment method. The significant amount of the crystalline motif and the few icosahedra in the glassy sample deteriorate the GFA.

Fe-Si networks in Na2FeSiO4 cathode materials

Using a combination of adaptive genetic algorithm search, motif-network search scheme and first-principles calculations, we have systematically studied the low-energy crystal structures of Na2FeSiO4. We show that the low-energy crystal structures with different space group symmetries can be classified into several families based on the topologies of their Fe-Si networks. In addition to the diamond-like network which is shared by most of the low-energy structures, another three robust Fe-Si networks are also found to be stable during the charge/discharge process. The electrochemical properties of representative structures from these four different Fe-Si networks in Na2FeSiO4 and Li2FeSiO4 are investigated and found to be strongly correlated with the Fe-Si network topologies. Our studies provide a new route to characterize the crystal structures of Na2FeSiO4 and Li2FeSiO4 and offer useful guidance for the design of promising cathodes for Na/Li ion batteries.

Structural signature and transition dynamics of Sb2Te3 melt upon fast cooling

Sb-centered defective octahedrons connect with each other via four-fold rings, a close link of the four-fold ring and defective octahedrons in amorphous Sb₂Te₃ has been revealed.

Novel penta-graphene nanotubes: strain-induced structural and semiconductor-metal transitions

Research into novel one-dimensional (1D) materials and associated structural transitions is of significant scientific interest. It is widely accepted that a 1D system with a short-range interaction cannot have 1D phase transition at finite temperature. Herein, we propose a series of new stable carbon nanotubes by rolling up penta-graphene sheets, which exhibit fascinating well-defined 1D phase transitions triggered by axial strain. Our first-principles calculations show that such penta-graphene nanotubes (PGNTs) are dynamically stable by phonon calculations, but transform from a tri-layer structure to a highly defective single-walled nanotube at low temperature in molecular dynamics simulations. We show that moderate compressive strains can drive structural transitions of (4,4), (5,5), and (6,6) PGNTs, during which the distances of neighboring carbon dimers in the inner shell have a sudden drop, corresponding to dimer-dimer nonbonding to bonding transitions. After such transition, the tubes become much more thermally stable and undergo semiconductor-metal transitions under increasing strain. The band gaps of PGNTs are not sensitive to chirality whereas they can be tuned effectively from visible to short-wavelength infrared by appropriate strain, making them appealing materials for flexible nano-optoelectronics. These findings provide useful insight into unusual phase transitions in low-dimensional systems.

[Identification of Y-chromosomal Genetic Types for the Soldier's Remains from Huaihai Campaign]

OBJECTIVES

To identify the Y-chromosomal genetic types for the soldier's remains from Huaihai Campaign, and to offer a clue for search of their paternal relatives.

METHODS

DNA of the remains were extracted by the ancient DNA extraction method. Yfiler kit was used for the multiplex amplification of 17 Y-STR loci. The haplogroups of the samples were speculated. Detailed genotyping of the selected Y-SNP was performed based on the latest Y-chromosome phylogenetic tree. Haplotype-sharing analysis was done based on the data of Y-SNP and Y-STR, the closest modern individual information to the genetic relationship of remains was gained.

RESULTS

A total of 8 Y-STR haplotypes were observed on 17 Y-STR loci of 8 male individuals. Furthermore, 6 Y-SNP haplogroups were identified, which were O2a1-M95+, O1a1-P203+, O3*-M122+/M234-, D1-M15+, C3*-ST and R1a1-M17+.

CONCLUSIONS

Identification of Y-chromosomal genetic types for the soldier's remains from Huaihai Campaign shows a reference value on inferring the geographical origins of old materials.

[Chinese expert consensus for non-antiinfective effects and clinical use of macrolides]

Important/potential value of macrolides has been proved in the management of chronic respiratory diseases by increasing basic and clinical trials.Through three face-to-face discussions, 10 experts examined important data and drafted this consensus related to macrolides: (1) mechanism of non-antiinfective effects; (2) clinical use in chronic respiratory diseases; (3) cautions of long-term use.The mechanism out of non-antiinfective effects includes anti-inflammatory effect, modifying airway secretion, immune-regulation related to antibacterial effect, corticoid saving effect and anti-viral effect.The efficacy of long-term use of low-dose macrolides is definitely confirmed in diffuse panbronchiolitis, chronic rhinosinusitis. It is considerably used in bronchiectasia, cystic fibrosis, severe asthma and chronic obstructive pulmonary disease. Further studies should be conducted in cryptogenic organizing pneumonia and respiratory viral infection. It should be paid attention to its possible adverse effects (including drug interactions, cardiac toxicity, ototoxicity and disturbance of intestinal flora) and drug resistance in long-term use.A Chinese consensus for non-antiinfective effects and clinical use of macrolides is developed for the first time, which aims to expand their rational use and the further research.

High-pressure structures of yttrium hydrides

In this work, the crystal structures of YH₃ and YH₄ at high pressure (100-250 GPa) have been explored using a genetic algorithm combined with first-principles calculations. New structures of YH₃ with space group symmetries of P21/m and I4/mmm were predicted. The electronic structures and the phonon dispersion properties of various YH₃ and YH₄ structures at different temperatures and pressures were investigated. Among YH₃ phases, the P21/m structure of YH₃ was found to have a relatively high superconducting transformation temperature T _c of 19 K at 120 GPa, which is reduced to 9 K at 200 GPa. Other YH₃ structures have much lower T _cs. Compared with YH₃, the T _c of the YH₄ compound is much higher, i.e. 94 K at 120 GPa and 55 K at 200 GPa.

Identifying the heterogeneity of COPD by V/P SPECT: a new tool for improving the diagnosis of parenchymal defects and grading the severity of small airways disease

Introduction

Airway obstruction and possible concomitant pulmonary diseases in COPD cannot be identified conventionally with any single diagnostic tool. We aimed to diagnose and grade COPD severity and identify pulmonary comorbidities associated with COPD with ventilation/perfusion single-photon emission computed tomography (V/P SPECT) using Technegas as the functional ventilation imaging agent.

Methods

94 COPD patients (aged 43–86 years, Global Initiative for Chronic Obstructive Lung Disease (GOLD) stages I–IV) were examined with V/P SPECT and spirometry. Ventilation and perfusion defects were analyzed blindly according to the European guidelines. Penetration grade of Technegas in V SPECT measured the degree of obstructive small airways disease. Total preserved lung function and penetration grade of Technegas in V SPECT were assessed by V/P SPECT and compared to GOLD stages and spirometry.

Results

Signs of small airway obstruction in the ventilation SPECT images were found in 92 patients. Emphysema was identified in 81 patients. Two patients had no signs of COPD, but both of them had a pulmonary embolism, and in one of them we also suspected a lung tumor. The penetration grade of Technegas in V SPECT and total preserved lung function correlated significantly to GOLD stages (r=0.63 and −0.60, respectively, P<0.0001). V/P SPECT identified pulmonary embolism in 30 patients (32%). A pattern typical for heart failure was present in 26 patients (28%). Parenchymal changes typical for pneumonia or lung tumor were present in several cases.

Conclusion

V/P SPECT, using Technegas as the functional ventilation imaging agent, is a new tool to diagnose COPD and to grade its severity. Additionally, it revealed heterogeneity of COPD caused by pulmonary comorbidities. The characteristics of these comorbidities suggest their significant impact in clarifying symptoms, and also their influence on the prognosis.

Si-centered capped trigonal prism ordering in liquid Pd82Si18 alloy study by first-principles calculations

Distribution of trigonal prism capped with three half-octahedra (orange clusters), archimedean anti-prism (green ones) and icosahedron (blue ones) clusters in Pd₈₂Si₁₈ at different temperature (a) 900 K, (b) 1216 K. (c) Connection way of different clusters, and pink ones are the sharing atoms.

Hybrid silicon–carbon nanostructures for broadband optical absorption

Superposition of the optical spectra of the assemble of Sim@C_2nwhich exhibit a broadband optical absorption and the spectrum of solar radiation.

Effects of Oxygen Impurities on Glass-Formation Ability in Zr2Cu Alloy

Using ab initio molecular dynamics simulations, we show that oxygen (O) impurities have a noticeable influence on the glass-formation ability (GFA) in Zr2Cu alloy. Cu-centered icosahedral clusters and Zr-centered Kasper polyhedra are the dominate short-range orders in undercooled Zr2Cu liquid which are most likely to be responsible for the glass formation in Zr2Cu systems. When O is introduced, a Zr octahedron is formed around the O impurity. Most of the Zr atoms in the octahedron also serve as the bridging atoms for cross-linked Kasper polyhedral network, resulting in an O-centered medium range order (MRO) structure. Meanwhile, Cu atoms are moved away from the first shell of O-centered octahedral clusters. With 1 at. % O impurities, the fractions of Zr-centered clusters are less affected, while the increase of ideal icosahedral order and decrease of distorted icosahedral order lead to a more stable atomic structure. This result suggests that a low concentration of O impurities would improve the GFA in Zr2Cu alloy. However, when ∼5 at. % O impurities are included, the ideal icosahedral clusters and Zr-centered Kasper polyhedra are seriously suppressed by the formation of O-centered MRO, which can lead to deterioration of GFA. Our analyses provide useful insight into glass formation behavior in O-doped metallic alloy systems.

[A three years longitudinal follow-up study of pulmonary function changes in patients with chronic obstructive pulmonary disease]

OBJECTIVE

To investigate the characteristics and the risk factors of pulmonary function in patients with chronic obstructive pulmonary disease (COPD) for a 3 year follow-up.

METHODS

Subjects diagnosed as COPD were followed up for 3 years in the Management Center of Chronic Respiratory Disease at XINQIAO Hospital from September 2009 to June 2012.This was a retrospective study. Parameters related to respiratory function mainly first second forced expiratory volume (FEV1), COPD assessment test (CAT), 6 minutes walking distance (6MWD) and acute exacerbation were recorded during follow-up.

RESULTS

Although the majority of patients were treated with drugs such as inhaled corticosteroid combined with long-term bronchial dilatation during the three years, FEV1 decreased progressively. The average annual decline of FEV1 was(31.80±61.99)ml, translating into a mean annual decline of(3.74±6.18)%. However, there were significant differences in changes of FEV1. Approximately, FEV1 in 78.3% (47/60) patients decreased, only 21.7%(13/60) patients kept stable FEV1. There was a correlation between decrease of FEV1, FEV1%predicted and the exacerbation (r=0.298, 0.361, 0.273; P<0.05). Logistic regression showed that the positive bronchodilator reversibility and the initial FEV1 were the independent factors associated with significant changes in FEV1 (respectively, OR=5.54, 95%CI 1.55-19.73; OR=8.28, 95%CI 1.42-48.32).

CONCLUSION

The changes of pulmonary function in patients with COPD are heterogeneous, although most patients are treated in a standard way. Nearly 80% patients still represent deterioration of pulmonary function. Decline of FEV1 is closely related to the initial pulmonary function and bronchodilator reversibility.

Tight-binding calculation studies of vacancy and adatom defects in graphene

Computational studies of complex defects in graphene usually need to deal with a larger number of atoms than the current first-principles methods can handle. Here, we show that a recently developed three-center tight-binding potential for carbon is very efficient for large scale atomistic simulations and can accurately describe the structures and energies of various defects in graphene. Using the three-center tight-binding potential, we have systematically studied the stable structures and formation energies of vacancy and embedded-atom defects of various sizes up to four vacancies and four embedded atoms in graphene. Our calculations reveal low-energy defect structures and provide a more comprehensive understanding of the structures and stability of defects in graphene.

Ab initio molecular dynamics simulations of short-range order in Zr₅₀Cu₄₅Al₅ and Cu₅₀Zr₄₅Al₅ metallic glasses

Comparative analysis between Zr-rich Zr50Cu45Al5 and Cu-rich Cu50Zr45Al5 metallic glasses (MGs) is extensively performed to locate the key structural motifs accounting for their difference of glass forming ability. Here we adopt ab initio molecular dynamics simulations to investigate the local atomic structures of Zr50Cu45Al5 and Cu50Zr45Al5 MGs. A high content of icosahedral-related (full and distorted) orders was found in both samples, while in the Zr-rich MG full icosahedrons ⟨0, 0, 12, 0⟩ is dominant, and in the Cu-rich one the distorted icosahedral orders, especially ⟨0, 2, 8, 2⟩ and ⟨0, 2, 8, 1⟩, are prominent. And the ⟨0, 2, 8, 2⟩ polyhedra in Cu50Zr45Al5 MG mainly originate from Al-centered clusters, while the ⟨0, 0, 12, 0⟩ in Zr50Cu45Al5 derives from both Cu-centered clusters and Al-centered clusters. These difference may be ascribed to the atomic size difference and chemical property between Cu and Zr atoms. The relatively large size of Zr and large negative heat of mixing between Zr and Al atoms, enhancing the packing density and stability of metallic glass system, may be responsible for the higher glass forming ability of Zr50Cu45Al5.

[Effect of blastocyst quality on the strategy of single blastocyst transfer in frozen-thawed cycles]

OBJECTIVE

To investigate the effect of blastocyst quality on the strategy of single blastocyst transfer in frozen-thawed cycles.

METHODS

A retrospective analysis was performed in Reproductive Medicine Center, Maternal and Child Health Hospital of Guangxi Zhuang Autonomous Region on clinical data of single frozen-thawed blastocyst transfer cycles from January 2008 to December 2013. All cycles were divided into four groups (AA, AB/BA, BB, BC/CB) according to the blastocyst score, then the clinical outcomes were compared between groups. And on this basis, the clinical outcomes were further explored when the group of outcomes with single blastocyst transfer wasn't ideal, which would diverted to transfer two blastocyst.

RESULTS

In single frozen blastocyst transfer cycles, the clinical pregnancy rate of each group with the blastocyst scored AA, AB/BA, BB, BC/CB were 61.4% (470/765), 51.2% (330/645), 40.5% (407/1 005), 22.9% (60/262), live births rate in each group were 52.2% (399/765), 41.2% (266/645), 30.4% (306/1 005), 13.7% (36/262), and the abortion rate were 13.6% (64/470), 16.7% (55/330), 21.4% (87/407), 35.0%(21/60), separately. This showed that the clinical pregnancy rate and live births rate decreased significantly with the decline of blastocyst quality (P<0.01), but the abortion rate showed significant upward trend (P<0.01). When single blastocyst scored ≥BB grade transferred, an acceptable clinical pregnancy rate (>40%) and live births rate (>30%) could be obtained, however, the clinical pregnancy rate of 22.9% and live births rate of 13.7% could only be acquired when blastocyst scored BC/CB only transferred one embryo, which significant lower than those of each group scored ≥BB grade (P<0.01). So, after that, the blastocyst scored BC/CB were further divided into two groups (single blastocyst transferred versus two blastocyst transferred) to investigate, then the result showed that the clinical pregnancy rate [22.9% versus 38.5%(67/174),P<0.01] and live births rate [13.7% versus 30.5%(16/67),P<0.01] were significantly increased in the group of two blastocyst transferred compared with the group of one blastocyst transferred, and the abortion rate was also significantly decreased from 35.0% to 17.9% (12/67;P<0.05). So when two blastocyst scored BC/CB were transferred, the clinical outcomes were similar to the group of one blastocyst scored BB transferred (P>0.05).

CONCLUSIONS

Of single blastocyst transfer in frozen-thawed cycles, the clinical pregnancy rate and liver births rate showed significant upward trend, but the abortion rate showed significant downward trend, with the decline of blastocyst quality. When the blastocyst scored ≥BB grade, the single blastocyst transfer could be considered to be performed.

Predictive potential role of glutathione S-transferases polymorphisms in response to chemotherapy and breast cancer prognosis

The aim of this study was to evaluate the role of GSTM1 null/present, GSTT1 null/present, and GSTP1 polymorphisms in the clinical response to chemotherapy and treatment outcome of breast cancer. The GSTM1, GSTT1, and GSTP1 IIe105Val polymorphism genotypes were analyzed using polymerase chain reaction coupled with restriction fragment length polymorphism. Conditional logistic regression analysis revealed that breast cancer patients carrying the GG genotype of GSTP1 IIe105Val showed a significantly better response to chemotherapy compared to those expressing the AA genotype [odds ratio = 2.66, 95% confidence interval (CI) = 1.24-5.91, P = 0.007]. The Cox proportional hazards model indicated that the GG genotype of GSTP1 IIe105Val in breast cancer patients was correlated with a lower risk of death from all causes than those with AA genotype. The adjusted hazard ratio (95%CI) for the GG genotype of GSTP1 IIe105Val was 0.44 (0.18-0.99; P = 0.03). In conclusion, the results of our study indicated that the GG genotype of GSTP1 IIe105Val was significantly associated with better response to chemotherapy and longer overall survival, compared to the wide-type genotype.

Dynamics and Diffusion Mechanism of Low-Density Liquid Silicon

A first-order phase transition from a high-density liquid to a low-density liquid has been proposed to explain the various thermodynamic anomies of water. It also has been proposed that such liquid-liquid phase transition would exist in supercooled silicon. Computer simulation studies show that, across the transition, the diffusivity drops roughly 2 orders of magnitude, and the structures exhibit considerable tetrahedral ordering. The resulting phase is a highly viscous, low-density liquid silicon. Investigations on the atomic diffusion of such a novel form of liquid silicon are of high interest. Here we report such diffusion results from molecular dynamics simulations using the classical Stillinger-Weber (SW) potential of silicon. We show that the atomic diffusion of the low-density liquid is highly correlated with local tetrahedral geometries. We also show that atoms diffuse through hopping processes within short ranges, which gradually accumulate to an overall random motion for long ranges as in normal liquids. There is a close relationship between dynamical heterogeneity and hopping process. We point out that the above diffusion mechanism is closely related to the strong directional bonding nature of the distorted tetrahedral network. Our work offers new insights into the complex behavior of the highly viscous low density liquid silicon, suggesting similar diffusion behaviors in other tetrahedral coordinated liquids that exhibit liquid-liquid phase transition such as carbon and germanium.

Si78 double cage structure and special optical properties

We performed first-principles calculations to study the structural stability of Si78 clusters with or without hydrogen passivation. The calculations reveal that an endohedral double cage isomer is more stable than the diamond-like structure, whereas the opposite is found for the hydrogen passivated isomers. In particular, the hydrogenated double cage and diamond-like structure may display blue shifts to the visible and UV regions, respectively. The IR vibration spectra, ionization potential (IP) and electronic density-of-states of the clusters were calculated and discussed.

Theoretical study on the structures and optical absorption of Si₁₇₂ nanoclusters

The structures and optical properties of silicon nanoclusters (Si NCs) have attracted continuous interest in the last few decades. However, it is a great challenge to determine the structures of Si NCs for accurate property calculation due to the complication and competition of various structural motifs. In this work, a Si172 NC with a size of about 1.8 nm was investigated using a genetic algorithm combined with tight-binding and DFT calculations. We found that a diamond crystalline core with 50 atoms (1.2 nm) was formed in the Si172 NC. It can be expected that at a size of about 172 atoms, a diamond crystalline structure can nucleate from the center of the Si NCs. The optical properties of the pure and hydrogenated Si172 NC structures also have been studied using the TDDFT method. Compared with the pure Si172 NC, the absorption peaks of the hydrogenated Si172 NC are obviously blue-shifted.

Efficient and accurate treatment of electron correlations with Correlation Matrix Renormalization theory

We present an efficient method for calculating the electronic structure and total energy of strongly correlated electron systems. The method extends the traditional Gutzwiller approximation for one-particle operators to the evaluation of the expectation values of two particle operators in the many-electron Hamiltonian. The method is free of adjustable Coulomb parameters, and has no double counting issues in the calculation of total energy, and has the correct atomic limit. We demonstrate that the method describes well the bonding and dissociation behaviors of the hydrogen and nitrogen clusters, as well as the ammonia composed of hydrogen and nitrogen atoms. We also show that the method can satisfactorily tackle great challenging problems faced by the density functional theory recently discussed in the literature. The computational workload of our method is similar to the Hartree-Fock approach while the results are comparable to high-level quantum chemistry calculations.

Analysis of postoperative PSA changes after ultrasound-guided permanent [125I] seed implantation for the treatment of prostate cancer

The aim of this study was to explore postoperative changes in prostate-specific antigen (PSA) levels and risk factors that influence the clinical effects of ultrasound-guided permanent [(125)I] seed implantation in the treatment of prostate cancer. From July 2009 to December 2012, 41 prostate cancer patients who underwent transrectal ultrasound-guided [(125)I] seed implantation were followed up for 3-56 months. The patients were divided into 2 groups according to their results: group A, benign rebound group, 31 cases; and group B, biochemical relapse group, 10 cases. A blood analysis of group A showed that the initial PSA rise after a nadir occurred postoperatively at 16.8 ± 1.2 months, and in 65.8% (27/41) patients the rise occurred during 15-27 weeks. For group B, the initial PSA rise after a nadir occurred postoperatively at 30.2 ± 2.1 months, and the difference in the time parameter of the initial PSA rise after the nadir was statistically significant between the 2 groups (P < 0.01). During treatment, age was shown to be a risk factor for group A (P = 0.0027, P < 0.01). Postoperative changes in PSA levels after ultrasound-guided permanent [(125)I] seed implantation contributed to the assessment of the clinical treatment effects.

A computational study of diffusion in a glass-forming metallic liquid

Liquid phase diffusion plays a critical role in phase transformations (e.g. glass transformation and devitrification) observed in marginal glass forming systems such as Al-Sm. Controlling transformation pathways in such cases requires a comprehensive description of diffusivity, including the associated composition and temperature dependencies. In the computational study reported here, we examine atomic diffusion in Al-Sm liquids using ab initio molecular dynamics (AIMD) and determine the diffusivities of Al and Sm for selected alloy compositions. Non-Arrhenius diffusion behavior is observed in the undercooled liquids with an enhanced local structural ordering. Through assessment of our AIMD result, we construct a general formulation for Al-Sm liquid, involving a diffusion mobility database that includes composition and temperature dependence. A Volmer-Fulcher-Tammann (VFT) equation is adopted for describing the non-Arrhenius behavior observed in the undercooled liquid. The composition dependence of diffusivity is found quite strong, even for the Al-rich region contrary to the sole previous report on this binary system. The model is used in combination with the available thermodynamic database to predict specific diffusivities and compares well with reported experimental data for 0.6 at.% and 5.6 at.% Sm in Al-Sm alloys.