Phase change materials (PCMs) are highly attractive for nonvolatile electrical and all-optical memory applications because of unique features such as ultrafast and reversible phase transitions, long-term endurance, and high scalability to nanoscale dimensions. Understanding their transient characteristics upon phase transition in both the electrical and the optical domains is essential for using PCMs in future multifunctional optoelectronic circuits. Here, we use a PCM nanowire embedded into a nanophotonic circuit to study switching dynamics in mixed-mode operation. Evanescent coupling between light traveling along waveguides and a phase-change nanowire enables reversible phase transition between amorphous and crystalline states. We perform time-resolved measurements of the transient change in both the optical transmission and resistance of the nanowire and show reversible switching operations in both the optical and the electrical domains. Our results pave the way toward on-chip multifunctional optoelectronic integrated devices, waveguide integrated memories, and hybrid processing applications.

Ga14Sb86 film has been studied to explore its suitability as a novel active material for phase change memory application. With a crystallization temperature about 220 °C, Ga14Sb86 film has the activation energy of crystallization larger than 4.6 eV obtained both by nonisothermal and isothermal methods. This leads to an ultralong data retention, which is characterized by the temperature for ten years data retention at 162 °C. The reversible phase change can be realized by a pulse as short as 20 ns. Ga14Sb86-based cell shows a good endurance up to 3.2x105 SET-RESET cycles during endurance test.

ZnSb films have higher crystallization temperature (~257 °C), larger crystalline activation energy (~5.63 eV), better 10 year-data-retention (~201 °C) and lower melting temperature (~500 °C).

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The thermal stability of amorphous Sb2Te film can be significantly improved by the addition of Cu. CuSb4Te2 alloy is considered to be a potential candidate for phase change random access memory (PCRAM), as evidenced by a higher crystallization temperature, a better data retention ability, and a faster switching speed in comparison with those of Ge2Sb2Te5. A reversible switching between set and reset states can be realized by an electric pulse as short as 7 ns for CuSb4Te2-based PCRAM cell. In addition, CuSb4Te2 shows endurance up to 1.5 × 105 cycles with a resistance ratio of about two orders of magnitude.

How to identify the early signs of hypertensive heart disease is the key to block or reverse the process of heart failure. The aim of this study was to evaluate the predictive value of left atrial (LA) enlargement in the early stage of hypertensive heart disease and to explore the correlations between LA enlargement and heart failure with normal ejection fraction (HFnEF), as well as the metabolic syndrome (MetS). Baseline clinical characteristics, biochemical indices, electrocardiographic and echocardiographic data were collected from 341 consecutive patients with essential hypertension. Among those patients, LA enlargement was more frequently presented than LV enlargement (57.2% vs 17.9%). Compared with patients without HFnEF, the prevalence of LA enlargement was higher in patients with HFnEF (82.9% vs 49.0%, P<.0001). From grade 2 to grade 3 hypertension, LA size was significantly larger in patients with MetS (P<.01) than those without. Multivariate linear regression analyses showed that age, body mass index, waist circumference, triglyceride level, and left ventricular diameter were independent predictors of LA enlargement. The simple measurement for identification of LA enlargement potentially allows early recognition of those patients at risk for heart failure, particularly among patients with MetS. J Clin Hypertens (Greenwich). 2014;16:192-197. ª2014 Wiley Periodicals, Inc.Recent epidemiological data show that more than 200 million adults present with hypertension in China, which was found as the second leading cause of heart failure. From hypertension to hypertensive heart disease is a slow and progressive process, and persistent high pressure load may lead to compensatory left ventricular (LV) hypertrophy. LV hypertrophy or enlargement confirmed by electrocardiography (ECG) or echocardiography is about 10% to 30% in unselected hypertensive patients. Previous studies 1 have shown that echocardiographic left atrial (LA) enlargement occurring before LV hypertrophy is an early sign of hypertensive heart disease. LA volume provides a sensitive morphophysiologic expression of the severity of LV diastolic dysfunction, and appears to be a useful index of cardiovascular risk and disease burden, and LA volume indexed to body surface is independently associated with outcome of cardiovascular diseases.2 A report by Nicolaou and colleagues 3 has recently revealed that the metabolic syndrome (MetS) increases LA diameter in paroxysmal atrial fibrillation patients and obesity was an important covariate of LA size in hypertensive patients. However, the prevalence of LA enlargement and its correlation to heart failure with normal ejection fraction (HFnEF) and MetS have not been assessed in Chinese hypertensive patients.The aims of the present study were 3-fold: (1) to investigate the prevalence of LA enlargement in patients with essential hypertension; (2) to assess the relationship between LA enlargement and HFnEF, as well as MetS; and (3) to explore independent predictors of LA enlargement.

Superlattice-like GaSb/Sb4Te phase change film was proposed for multilevel phase change memory with the feature of three stable resistance states. Two distinct transition temperatures of around 170 and 230 °C were observed in the superlattice-like GaSb/Sb4Te thin film. Under elevated temperature, the precipitated rhombohedral Sb phase was found in the Sb4Te layer, which was followed by the crystallization of rhombohedral Sb2Te3, whereas the GaSb layer remained almost in the amorphous state except the impinged Sb grains. The formation of percolation path for crystallization in the GaSb layer can account for the multilevel resistance states. For the GaSb/Sb4Te-based device, the reversibly electrical switching was realized under the electrical pulse as short as 10 ns, and the endurance was achieved at least 105 cycles among different resistance states.

In this paper, Te-free Ga-Sb-Se material is considered to be a storage medium for phase change memory. Compared with Ge2Sb2Te5, Ga1Sb6Se3 exhibits a better thermal stability, which leads to a brilliant performance for data retention. Ga1Sb6Se3-based phase change memory cell shows reversible switching between reset and set states with a resistance ratio of two orders of magnitude. The minimum reset/set voltages are significantly lower than those of Ge2Sb2Te5-based one. Meanwhile, Ga1Sb6Se3 film possesses a faster switching speed than Ge2Sb2Te5. Thermal simulation confirms the improvement of cell performance originating from the low thermal conductivity and low melting point of Ga1Sb6Se3.