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1.
PLoS One ; 19(3): e0298678, 2024.
Article in English | MEDLINE | ID: mdl-38498482

ABSTRACT

Throughout history, rivers and lakes have wielded a profound influence on the dynamics of urban transportation expansion. To illustrate this phenomenon, we turn to the century-long evolution of the road network in Wuhan, China, as a case study. The study aims to explore the relationship framework between water bodies and urban transportation, characterized by the sequence of "strong connection" to "weakened connection", then to "mutual restriction", and ultimately to "mutual benefit". Additionally, the analysis of the impact mechanisms of rivers and lakes on urban transportation at different stages of development is also a key research objective. To facilitate our exploration, we select the road networks in Wuhan from four years of 1922, 1969, 1995, and 2023 as the primary research subjects. By establishing water buffers, we scrutinize the evolving characteristics of riverside and lakeside transportation amidst the city's expansion. Based on the modified shortest path model, we introduce the innovative concepts of "Detour Index" and "Weighted Detour Index" to assess the road accessibility of each node in the city based on its inherent environmental conditions. This allows for the effective analysis of the potential impact of water bodies as "obstacles" on the road network at different stages of urban development. The study found that in the areas adjacent to the rivers and lakes in Wuhan, there is insufficient road accessibility based on their inherent environmental conditions. Particularly, some areas along the rivers may become "terminals" in the urban road network. Furthermore, during the process of urban expansion, the correlation between the urban road network and rivers continues to weaken, while the correlation with lakes continues to strengthen. These conclusions can provide valuable insights for the planning of urban roads near water bodies.


Subject(s)
Lakes , Transportation , Humans , Cities , China , Water , Rivers , Environmental Monitoring
2.
Front Bioeng Biotechnol ; 11: 1309688, 2023.
Article in English | MEDLINE | ID: mdl-38026890

ABSTRACT

Osteoarthritis (OA) stands as a prevalent degenerative joint ailment, demanding immediate attention towards the development of efficacious therapeutic interventions. Presently, a definitive cure for OA remains elusive, and when conservative treatment modalities prove ineffective, resorting to a joint prosthesis becomes imperative. Temporary distraction emerges as a pivotal joint-preserving intervention in human OA patients, conferring both clinical amelioration and structural enhancements. Although extant clinical investigations exist, they are characterized by relatively modest sample sizes. Nonetheless, these studies furnish compelling evidence affirming that joint distraction engenders sustained clinical amelioration and structural refinement. Despite substantial strides in the last decade, a bibliometric analysis of joint distraction within the realm of osteoarthritis treatment research has been conspicuously absent. In this context, we have undertaken a comparative investigation utilizing bibliometric methodologies to scrutinize the landscape of joint distraction within osteoarthritis treatment. Our comprehensive analysis encompassed 469 scholarly articles. Our findings evince a consistent escalation in global research interest and publication output pertaining to this subject. The United States emerged as the frontrunner in international collaboration, publication count, and citation frequency, underscoring its preeminence in this domain. The journal "Osteoarthritis and Cartilage" emerged as the principal platform for disseminating research output on this subject. Notably, Mastbergen SC emerged as the most prolific contributor in terms of authorship. The identified keywords predominantly revolved around non-surgical interventions and joint arthroscopy procedures. This bibliometric analysis, augmented by visual representations, furnishes invaluable insights into the evolutionary trajectory of joint distraction as an osteoarthritis treatment modality spanning from 2003 to 2023. These insights will serve as a compass for the scientific community, facilitating further exploration in this promising domain.

3.
Nano Lett ; 23(6): 2362-2369, 2023 Mar 22.
Article in English | MEDLINE | ID: mdl-36861962

ABSTRACT

Phase-change random access memory is a promising technique to realize universal memory and neuromorphic computing, where the demand for robust multibit programming drives exploration for high-accuracy resistance control in memory cells. Here in ScxSb2Te3 phase-change material films, we demonstrate thickness-independent conductance evolution, presenting an unprecedently low resistance-drift coefficient in the range of ∼10-4-10-3, ∼3-2 orders of magnitude lower compared to conventional Ge2Sb2Te5. By atom probe tomography and ab initio simulations, we unveiled that nanoscale chemical inhomogeneity and constrained Peierls distortion together suppress structural relaxation, rendering an almost invariant electronic band structure and thereby the ultralow resistance drift of ScxSb2Te3 films upon aging. Associated with subnanosecond crystallization speed, ScxSb2Te3 serves as the most appropriate candidate for developing high-accuracy cache-type computing chips.

4.
Eur Spine J ; 30(10): 3115-3127, 2021 10.
Article in English | MEDLINE | ID: mdl-34392419

ABSTRACT

OBJECTIVE: We focus on providing the first comprehensive national dataset on the incidence, injury aetiology and mortality of TSCI in China. METHODS: A multi-stage stratified cluster sampling method was used. We included TSCI cases from all hospitals in three regions, nine provinces and 27 cities in China via search of electronic medical records and retrospectively analysed the characteristics of TSCI in China from 2009 to 2018. We estimated the incidence of TSCI in the total population and subgroups. RESULTS: There were 5954 actual cases in 2009, corresponding to a total estimated TSCI incidence of 45.1 cases per million population (95% CI, 44.0-46.3). There were 10,074 actual cases in 2018, corresponding to a total estimated TSCI incidence of 66.5 cases per million population (95% CI, 65.2-67.8) (P < 0.001; annual average percentage change (AAPC), 4.4%). From 2009 to 2018, the incidence of almost all sex/age groups showed an increasing trend over time (P < 0.001; AAPC, 0.7-8.8%). The elderly population (aged 65-74) displayed the highest incidence of TSCI (with an average annual incidence of 127.1 cases per million [95% CI, 119.8-134.3]). CONCLUSIONS: The TSCI incidence increased significantly from 2009 to 2018. The incidence in the elderly populations was consistently high and continues to increase over time. The mortality of TSCI patients in hospitals is relatively low and continues to decrease each year, but elderly individuals remain at a high risk of hospital death.


Subject(s)
Spinal Cord Injuries , Aged , China/epidemiology , Humans , Incidence , Research Design , Retrospective Studies , Spinal Cord Injuries/epidemiology
5.
Zhongguo Xiu Fu Chong Jian Wai Ke Za Zhi ; 34(3): 313-317, 2020 Mar 15.
Article in Chinese | MEDLINE | ID: mdl-32174075

ABSTRACT

OBJECTIVE: To investigate the effect of hydrogen peroxide on anti-infection and reducing postoperative drainage in multi-segmental lumbar surgery. METHODS: A clinical data of 510 patients with multi-segmental lumbar degenerative diseases who were treated with surgery between January 2017 and January 2018 was retrospectively analyzed. In study group, the incisions of 230 cases were washed with hydrogen peroxide before suture. In control group, the incisions of 280 cases were washed with normal saline before suture. There was no significant difference in gender, age, lesion type, disease duration, operative segment, and other clinical data between the two groups ( P>0.05). The operation time, intraoperative blood loss, postoperative drainage volume, and postoperative incidence of infection were recorded and compared between the two groups. The Centers for Disease Control and Prevention (CDC) standard was used to evaluate infection, which was divided into superficial infection and deep infection. RESULTS: All operations completed successfully. There was no significant difference in operation time and intraoperative blood loss between the two groups ( P>0.05). The postoperative drainage volume in the study group was significantly less than that in the control group ( t=-2.990, P=0.005). A total of 13 patients developed infection after operation, including 10 cases of superficial infection (2 cases in the study group and 8 cases in the control group) with the infection time of (7.3±1.5) days, and 3 cases of deep infection (all in the control group) with the infection time of (16.6±3.1) days. The incidences of superficial and deep infections in the study group were lower than those in the control group, but there was no significant difference between the two groups ( χ 2=2.595, P=0.123; P=0.256). All the superficial infections were Staphylococcus aureus infection and recovered after active dressing change. Among the patients with deep infections, 2 cases were infected by Staphylococcus aureus and 1 case was infected by Escherichia coli; and the incisions healed after being washed and sutured thoroughly, and active dressing change. CONCLUSION: The incidence of postoperative infection and postoperative drainage volume can be reduced by washing the incision with hydrogen peroxide in multi-segmental lumbar surgery.


Subject(s)
Drainage , Hydrogen Peroxide/therapeutic use , Spinal Fusion , Humans , Lumbar Vertebrae , Retrospective Studies , Treatment Outcome
6.
Zhongguo Xiu Fu Chong Jian Wai Ke Za Zhi ; 34(1): 69-75, 2020 Jan 15.
Article in Chinese | MEDLINE | ID: mdl-31939238

ABSTRACT

OBJECTIVE: To compare the effectiveness and screw planting accuracy of percutaneous reduction and internal fixation with robot and traditional fluoroscopy-assisted in the treatment of single-level thoracolumbar fractures without neurological symptoms. METHODS: The clinical data of 58 patients with single-level thoracolumbar fractures without neurological symptoms between December 2016 and January 2018 were retrospectively analysed. According to different surgical methods, the patients were divided into group A (28 cases underwent robot-assisted percutaneous reduction and internal fixation) and group B (30 cases underwent fluoroscopy-assisted percutaneous reduction and internal fixation). There was no neurological symptoms, other fractures or organ injuries in the two groups. There was no significant difference in general data of age, gender, fracture location, AO classification, time from injury to surgery, and preoperative vertebral anterior height ratio, sagittal Cobb angle, visual analogue scale (VAS) score, and Oswestry disability index (ODI) score between the two groups ( P>0.05). The screw placement time, operation time, intraoperative blood loss, intraoperative fluoroscopy frequency, hospitalization time, operation cost, postoperative complications, VAS score, ODI score, anterior vertebral height ratio, and sagittal Cobb angle before operation, at 3 days, 6 months after operation, and at last follow-up were recorded and compared between the two groups. The accuracy of the pedicle screw placement was evaluated by Neo's criteria. RESULTS: The screw placement time, operation time, and intraoperative fluoroscopy frequency of group A were significantly less than those of group B, and the operation cost was significantly higher than that of group B ( P<0.05). But there was no significant difference in intraoperative blood loss and hospitalization time between the two groups ( P>0.05). Both groups were followed up 12-24 months, with an average of 15.2 months. The accuracy rate of screw placement in groups A and B was 93.75% (150/160) and 84.71% (144/170), respectively, and the difference was significant ( χ 2=5.820, P=0.008). Except for 1 case of postoperative superficial infection in group A and wound healing after dressing change, there was no complication such as neurovascular injury, screw loosening and fracture in both groups, and there was no significant difference in the incidence of complications between the two groups ( χ 2=0.625, P=0.547). The anterior vertebral height ratio, sagittal Cobb angle, VAS score, and ODI score of the two groups were significantly improved ( P<0.05); there was no significant difference between the two groups at all time points after operation ( P>0.05). CONCLUSION: The spinal robot and traditional fluoroscopy-assisted percutaneous reduction and internal fixation can both achieve satisfactory effectiveness in the treatment of single-level thoracolumbar fractures without neurological symptoms. However, the former has higher accuracy, fewer fluoroscopy times, shorter time of screw placement, and lower technical requirements for the operator. It has wide application potential.


Subject(s)
Fracture Fixation, Internal , Pedicle Screws , Robotics , Spinal Fractures , Fluoroscopy , Humans , Lumbar Vertebrae , Retrospective Studies , Thoracic Vertebrae , Treatment Outcome
7.
World Neurosurg ; 133: e303-e307, 2020 Jan.
Article in English | MEDLINE | ID: mdl-31520754

ABSTRACT

OBJECTIVE: To explore the safety and efficacy of hydrogen peroxide H2O2 in controlling blood loss and surgical site infection (SSI) after multisegmental lumbar spine surgery. METHODS: A total of 2626 patients who had undergone multisegmental lumbar spinal surgery from January 2015 to January 2018 were included in the present study. Stratified by the use of H2O2 irrigation, they were divided into 2 groups: the control group (n = 1345) and the experimental group (n = 1281). The demographic parameters, laboratory examination results, and surgery-related information (e.g., operative time, number of operated levels, intraoperative blood loss, postoperative drainage, postoperative SSI, extubation time), and perioperative complications were recorded. RESULTS: No significant differences were seen regarding the demographic parameters, laboratory examination results, comorbidities, and surgery-related information. The extubation time and postoperative drainage collection were lower in the experimental group (3.6 ± 0.5 vs. 4.1 ± 0.6 days, P = 0.402; 251.8 ± 67.5 vs. 291.8 ± 71.3 mL, P = 0.013). In the control group, the rate of SSI was 2.4% (32 of 1345) and included 17 superficial wound infections and 15 deep wound infections. In the experimental group, the SSI rate was 1.4% (18 of 1281; 15 with a superficial wound infection and 3 with a deep wound infection). Staphylococcus aureus was the most common organism, especially in the experimental group (66.7% vs. 50%). No statistically significant difference was found between the 2 groups in the perioperative complications, including hematencephalon, deep vein thrombosis, pulmonary embolism, and myocardial infarction (P > 0.05). Pneumocephalus was not observed in either group. CONCLUSION: The application of H2O2 in posterior lumbar interbody fusion can reduce the blood loss and incidence of SSI after surgery and was quite beneficial for controlling the increasing number of vancomycin-resistant bacteria.


Subject(s)
Anti-Infective Agents, Local/therapeutic use , Blood Loss, Surgical/prevention & control , Hemostasis, Surgical/methods , Hydrogen Peroxide/therapeutic use , Lumbar Vertebrae/surgery , Spinal Fusion , Surgical Wound Infection/prevention & control , Aged , Anti-Bacterial Agents/therapeutic use , Anti-Infective Agents, Local/administration & dosage , Antibiotic Prophylaxis , Case-Control Studies , Female , Humans , Hydrogen Peroxide/administration & dosage , Male , Middle Aged , Premedication , Retrospective Studies , Staphylococcal Infections/prevention & control , Therapeutic Irrigation
8.
Zhongguo Xiu Fu Chong Jian Wai Ke Za Zhi ; 33(12): 1474-1479, 2019 Dec 15.
Article in Chinese | MEDLINE | ID: mdl-31823543

ABSTRACT

OBJECTIVE: To investigate the safety and effectiveness of debridement and interbody fusion via posterior pedicle lateral approach in treatment of ankylosing spondylitis with thoracolumbar Andersson lesion (AL). METHODS: Between October 2011 and January 2017, 10 patients of ankylosing spondylitis with thoracolumbar AL were treated with debridement via posterior pedicle lateral approach and interbody fusion with bone grafting. There were 8 males and 2 females with an average age of 48.8 years (range, 31-79 years). The disease duration was 1.5-48.0 months (mean, 10.6 months). All patients were single-segment lesion, including 3 cases of T10, 11, 4 cases of T11, 12, and 3 cases of T12, L1. The preoperative visual analogue scale (VAS) score was 8.0±0.8, the Oswestry disability index (ODI) was 68.8%±5.5%, and the Cobb angle of local kyphosis was (26.3±7.1)°. According to American Spinal Injury Association (ASIA) scoring system, neurological impairment was assessed in 1 case of grade C, 4 cases of grade D, and 5 cases of grade E. RESULTS: All the operations of 10 patients completed successfully. The operation time was 120-185 minutes (mean, 151.5 minutes), and the intraoperative blood loss was 300-750 mL (mean, 450.0 mL). Dural sac tear occurred in 1 case during operation and was repaired, with no cerebrospinal fluid leakage after operation. All patients were followed up 24-50 months (mean, 31.2 months). At last follow-up, the VAS score was 1.9±0.9 and ODI was 13.0%±3.0%, showing significant differences when compared with preoperative ones (t=17.530, P=0.000; t=31.890, P=0.000). Neurological function was improved significantly at 24 months after operation, and rated as ASIA grade E. The Cobb angles were (12.6±4.6)° at 3 days and (13.6±4.6)° at 24 months after operation, which were significantly different from those before operation (P<0.05); there was no significant difference between 3 days and 24 months after operation (P>0.05). At 24 months after operation, the grafted bone obtained good fusion at AL segment. During the follow-up, there was no failure of internal fixation such as nail withdrawal, broken nail, and broken rod. CONCLUSION: Debridement and interbody fusion via posterior pedicle lateral approach for the ankylosing spondylitis with thoracolumbar AL can achieve satisfactory effectiveness, good fusion, and a certain correction of local kyphosis.


Subject(s)
Kyphosis , Spinal Fusion , Spondylitis, Ankylosing , Adult , Aged , Bone Transplantation , Debridement , Female , Fracture Fixation, Internal , Humans , Kyphosis/surgery , Lumbar Vertebrae , Male , Middle Aged , Spondylitis, Ankylosing/surgery , Thoracic Vertebrae , Treatment Outcome
9.
Science ; 366(6462): 210-215, 2019 10 11.
Article in English | MEDLINE | ID: mdl-31439757

ABSTRACT

Artificial intelligence and other data-intensive applications have escalated the demand for data storage and processing. New computing devices, such as phase-change random access memory (PCRAM)-based neuro-inspired devices, are promising options for breaking the von Neumann barrier by unifying storage with computing in memory cells. However, current PCRAM devices have considerable noise and drift in electrical resistance that erodes the precision and consistency of these devices. We designed a phase-change heterostructure (PCH) that consists of alternately stacked phase-change and confinement nanolayers to suppress the noise and drift, allowing reliable iterative RESET and cumulative SET operations for high-performance neuro-inspired computing. Our PCH architecture is amenable to industrial production as an intrinsic materials solution, without complex manufacturing procedure or much increased fabrication cost.

10.
Int J Biol Sci ; 15(7): 1460-1471, 2019.
Article in English | MEDLINE | ID: mdl-31337976

ABSTRACT

Growth Arrest Specific 5 (GAS5), a long noncoding RNA (lncRNA), functions as a tumor suppressor in multiple cancers. However, its function, downstream targets and upstream regulatory mechanism are still obscure in osteosarcoma cells. Here, we discovered that GAS5 was downregulated in cancerous osteosarcoma tissues and cells. Using a microarray analysis, we identified that GAS5 can regulate the expression of TP53, Bax, Bim, DDB2, TGFB and ROS1 in osteosarcoma cells. Specifically, GAS5 overexpression in the U2OS osteosarcoma cell line induced TP53, Bax and Bim levels but inhibited DDB2, TGFB and ROS1 expression, resulting in the inhibition of cell proliferation, invasion, colony formation and in vivo tumor formation. By analyzing the GAS5 promoter region (-2000), we identified several potential transcription factor-binding sites including NF-ĸB, IK-1, AP-1, SP1 and IRF1. By individually knocking down these transcription factors, we found that only knockdown of IRF1 affected GAS5 expression. Using immunoprecipitation (IP), mass spectrometry assays, and co-IP assays, we identified that IRF1 formed a transcriptional complex with Histone Deacetylase 1 and 2 (HDAC1/2) and C-terminal binding protein 1 (CtBP1). Functional analyses indicated that the CtBP1-HDAC1/2-IRF1 complex specifically bound to the GAS5 promoter and regulated its expression and downstream events. Knockdown of CtBP1 or overexpression of IRF1 in osteosarcoma cells can significantly reverse their oncogenic phenotypes. Altogether, our results indicated that the CtBP1-HDAC1/2-IRF1 transcriptional complex inhibited GAS5-mediated signaling in osteosarcoma cells, and it might be a potential therapeutic target for osteosarcoma treatment.


Subject(s)
Alcohol Oxidoreductases/metabolism , Bone Neoplasms/metabolism , DNA-Binding Proteins/metabolism , Histone Deacetylase 1/metabolism , Histone Deacetylase 2/metabolism , Interferon Regulatory Factor-1/metabolism , Osteosarcoma/metabolism , RNA, Long Noncoding/genetics , Cell Line, Tumor , Cell Proliferation , Down-Regulation , Gene Expression Regulation, Neoplastic , Humans , Neoplasm Transplantation , Oligonucleotide Array Sequence Analysis , Phenotype , Proto-Oncogene Proteins/metabolism , RNA, Long Noncoding/metabolism , Signal Transduction
11.
Med Sci Monit ; 25: 9981-9990, 2019 Dec 26.
Article in English | MEDLINE | ID: mdl-31907341

ABSTRACT

BACKGROUND Since C2 is adjacent to important nerves and blood vessels, the implantation risk of C2 internal fixation in this area is high and requires high accuracy. This study mainly discussed the application value of 3-dimensional (3D)-printed navigation template in C2 screw placement. MATERIAL AND METHODS A retrospective study compared 3D-printed navigation template-assisted screw placement (group A, n=32) and the C-arm based navigation-assisted screw placement group (group B, n=32). Group A was divided into 2 subgroups: A1 (C2 pedicle screw placement) and A2 (C2 pars screw placement); group B was divided into B1 (C2 pedicle screw placement) and B2 (C2 pars screw placement). The accuracy and safety of screw placement and clinical outcomes were evaluated. RESULTS There were 64 C2 screws placed in group A, and 95.31% achieved a grade A accuracy rating, including 52 screws in group A1 (96.15% grade A) and 12 screws in group A2 (91.67% grade A). A total of 64 C2 screws were placed in group B, and 84.38% achieved a grade A accuracy rating, including 50 screws in group B1 (84.00% grade A) and 14 screws in group B2 (85.71% grade A). The accuracy of screw placement differed significantly between groups A and B (P=0.041) and between groups A1 and B1 (P=0.039) but not between groups A2 and B2 (P=0.636). The postoperative efficacy of the 2 groups was satisfactory. And there were no complications of blood vessels or nerves related to screw placement in either group. CONCLUSIONS Although 3D-printed navigation template-assisted and C-arm based navigation-assisted C2 pedicle and pars screw placement provided similar safety and clinical efficacy, 3D-printed navigation template technology achieved more accurate C2 pedicle screw placement.


Subject(s)
Cervical Vertebrae/surgery , Pedicle Screws , Printing, Three-Dimensional , Adult , Aged , Cervical Vertebrae/diagnostic imaging , Female , Humans , Male , Middle Aged , Perioperative Care , Spinal Fractures/diagnostic imaging , Spinal Fractures/surgery , Treatment Outcome , Visual Analog Scale
12.
Science ; 358(6369): 1423-1427, 2017 12 15.
Article in English | MEDLINE | ID: mdl-29123020

ABSTRACT

Operation speed is a key challenge in phase-change random-access memory (PCRAM) technology, especially for achieving subnanosecond high-speed cache memory. Commercialized PCRAM products are limited by the tens of nanoseconds writing speed, originating from the stochastic crystal nucleation during the crystallization of amorphous germanium antimony telluride (Ge2Sb2Te5). Here, we demonstrate an alloying strategy to speed up the crystallization kinetics. The scandium antimony telluride (Sc0.2Sb2Te3) compound that we designed allows a writing speed of only 700 picoseconds without preprogramming in a large conventional PCRAM device. This ultrafast crystallization stems from the reduced stochasticity of nucleation through geometrically matched and robust scandium telluride (ScTe) chemical bonds that stabilize crystal precursors in the amorphous state. Controlling nucleation through alloy design paves the way for the development of cache-type PCRAM technology to boost the working efficiency of computing systems.

13.
Sci Rep ; 7(1): 5915, 2017 07 19.
Article in English | MEDLINE | ID: mdl-28725023

ABSTRACT

Phase change memory (PCM) is a promising nonvolatile memory to reform current commercial computing system. Inhibiting face-centered cubic (f-) to hexagonal (h-) phase transition of Ge2Sb2Te5 (GST) thin film is essential for realizing high-density, high-speed, and low-power PCM. Although the atomic configurations of f- and h-lattices of GST alloy and the transition mechanisms have been extensively studied, the real transition process should be more complex than previous explanations, e.g. vacancy-ordering model for f-to-h transition. In this study, dynamic crystallization procedure of GST thin film was directly characterized by in situ heating transmission electron microscopy. We reveal that the equilibrium to h-phase is more like an abnormal grain growth process driven by surface energy anisotropy. More specifically, [0001]-oriented h-grains with the lowest surface energy grow much faster by consuming surrounding small grains, no matter what the crystallographic reconfigurations would be on the frontier grain-growth boundaries. We argue the widely accepted vacancy-ordering mechanism may not be indispensable for the large-scale f-to-h grain growth procedure. The real-time observations in this work contribute to a more comprehensive understanding of the crystallization behavior of GST thin film and can be essential for guiding its optimization to achieve high-performance PCM applications.

14.
Sci Rep ; 6: 30645, 2016 07 29.
Article in English | MEDLINE | ID: mdl-27469931

ABSTRACT

Increasing SET operation speed and reducing RESET operation energy have always been the innovation direction of phase change memory (PCM) technology. Here, we demonstrate that ∼87% and ∼42% reductions of RESET operation energy can be achieved on PCM cell based on stoichiometric Ti1Sb2Te5 alloy, compared with Ge2Sb2Te5 and non-stoichiometric Ti0.4Sb2Te3 based PCM cells at the same size, respectively. The Ti1Sb2Te5 based PCM cell also shows one order of magnitude faster SET operation speed compared to that of the Ge2Sb2Te5 based one. The enhancements may be caused by substantially increased concentration of TiTe2 nano-lamellae in crystalline Ti1Sb2Te5 phase. The highly electrical conduction and lowly thermal dissipation of the TiTe2 nano-lamellae play a major role in enhancing the thermal efficiency of the amorphization, prompting the low-energy RESET operation. Our work may inspire the interests to more thorough understanding and tailoring of the nature of the (TiTe2)n(Sb2Te3)m pseudobinary system which will be advantageous to realize high-speed and low-energy PCM applications.

15.
Nat Commun ; 6: 10040, 2015 Nov 27.
Article in English | MEDLINE | ID: mdl-26610374

ABSTRACT

Phase-change memory based on Ti0.4Sb2Te3 material has one order of magnitude faster Set speed and as low as one-fifth of the Reset energy compared with the conventional Ge2Sb2Te5 based device. However, the phase-transition mechanism of the Ti0.4Sb2Te3 material remains inconclusive due to the lack of direct experimental evidence. Here we report a direct atom-by-atom chemical identification of titanium-centered octahedra in crystalline Ti0.4Sb2Te3 material with a state-of-the-art atomic mapping technology. Further, by using soft X-ray absorption spectroscopy and density function theory simulations, we identify in amorphous Ti0.4Sb2Te3 the titanium atoms preferably maintain the octahedral configuration. Our work may pave the way to more thorough understanding and tailoring of the nature of the Ti-Sb-Te material, for promoting the development of dynamic random access memory-like phase-change memory as an emerging storage-class memory to reform current memory hierarchy.

16.
Sci Rep ; 5: 8548, 2015 Feb 24.
Article in English | MEDLINE | ID: mdl-25709082

ABSTRACT

Group IIIA elements, Al, Ga, or In, etc., doped Sb-Te materials have proven good phase change properties, especially the superior data retention ability over popular Ge2Sb2Te5, while their phase transition mechanisms are rarely investigated. In this paper, aiming at the phase transition of Al-Sb-Te materials, we reveal a dominant rule of local structure changes around the Al atoms based on ab initio simulations and nuclear magnetic resonance evidences. By comparing the local chemical environments around Al atoms in respective amorphous and crystalline Al-Sb-Te phases, we believe that Al-centered motifs undergo reversible tetrahedron-octahedron reconfigurations in phase transition process. Such Al-centered local structure rearrangements significantly enhance thermal stability of amorphous phase compared to that of undoped Sb-Te materials, and facilitate a low-energy amorphization due to the weak links among Al-centered and Sb-centered octahedrons. Our studies may provide a useful reference to further understand the underlying physics and optimize performances of all IIIA metal doped Sb-Te phase change materials, prompting the development of NOR/NAND Flash-like phase change memory technology.

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