다중혈관 관상동맥 환자에서 y-문합을 이용하여 양쪽 내흉동맥만을 사용한 우회술의 조기 성적

[신간의 별자리x] 우리/미술, 그리고 ‘슬픔의 박물관’

Photoinduced reactivity of titanium dioxide

Cause, conseguenze e strategie di mitigazione Proponiamo il primo di una serie di articoli in cui affronteremo l’attuale problema dei mutamenti climatici. Presentiamo il documento redatto, votato e pubblicato dall’Ipcc - Comitato intergovernativo sui cambiamenti climatici - che illustra la sintesi delle ricerche svolte su questo tema rilevante.

/pdf/climate-change-2007-the-physical-science-basis-1x93ttz9jt.pdf

Climate Change 2007: The Physical Science Basis.

Graphene’s success has shown that it is possible to create stable, single and few-atom-thick layers of van der Waals materials, and also that these materials can exhibit fascinating and technologically useful properties. Here we review the state-of-the-art of 2D materials beyond graphene. Initially, we will outline the different chemical classes of 2D materials and discuss the various strategies to prepare single-layer, few-layer, and multilayer assembly materials in solution, on substrates, and on the wafer scale. Additionally, we present an experimental guide for identifying and characterizing single-layer-thick materials, as well as outlining emerging techniques that yield both local and global information. We describe the differences that occur in the electronic structure between the bulk and the single layer and discuss various methods of tuning their electronic properties by manipulating the surface. Finally, we highlight the properties and advantages of single-, few-, and many-layer 2D materials in...

/pdf/progress-challenges-and-opportunities-in-two-dimensional-1sweg4hljr.pdf

Progress, Challenges, and Opportunities in Two-Dimensional Materials Beyond Graphene

A facile and practical method for the stereospecific synthesis ofa-oxoketene O,S-acetals in water has been developed. Catalyzed by tetrabutylammonium bromide at room temperature, the one-pot reaction of various p-dicarbonyl compounds, 2-bromoethanol, and carbon disulfide, in the presence of potassium carbonate, leads to the corresponding α-oxoketene O,S-acetals stereospecifically in good to excellent yields. The catalyst in the aqueous phase can be recycled after the separation of the organic products.

A Clean, Facile, and StereospecificSynthesis of α-Oxoketene O,S-Acetals in Water

Superconducting thick films (200$\mu$m-300$\mu$m) of YBCO have been fabricated successfully on MgO substrates by a new approach. The precursor powders (YBa2Cu3O7-$\delta$(Y123)+0.1molY2BaCuO5(Y211)) are placed between two MgO (10mm x 10mm) slices to form sandwich structure. The YBCO thick films have been obtained from the precursors by modified melt growth process. Resistance measurements of YBCO thick films show Tcon of 87.3K and $\Delta$T of 4.5K. Estimates using hysteresis loops and the Bean model give a value of 2.78 x 10$^{3}$ A/cm2 (77K, 0T) for the critical current density. The observations of scanning electron microscopy (SEM) and x-ray diffraction patterns (XRD) show the supercoducting Y123 phase matrix containing discrete Y211 inclusions. 
Keywords: superconducting thick films, YBCO, Y211 phase, peritectic temperature

http://arxiv.org/pdf/cond-mat/0301448.pdf

Preparation of YBCO superconducting thick films On MgO substrates by modified melt growth process

Developing versatile and high sensitivity sensors is beneficial for promoting flexible electronic devices and human-machine interactive systems. Researchers are working on the exploration of various active sensing materials toward broad detection, multifunction, and low-power consumption. Here, a versatile ion-gel fibrous membrane is presented by electrospinning technology and utilized to construct capacitive sensors and triboelectric nanogenerator (TENG). The iontronic capacitive sensor exhibits inherently favorable sensitivity and repeatability, which retains long-term stability after 5000 cycles. The capacitive sensor can also detect a clear pulse waveform at the human wrist and enable the mapping of pressure distribution by a capacitive sensory matrix. For the iontronic TENG, the maximum peak power is 54.56 µW and can be used to power commercial electronics. In addition, the prepared iontronic TENG array can achieve interactive, rapidly responsive, and accurate dynamic monitoring, which broadens the exploration to direct and effective sensory devices. The versatile ion-gel fibrous membrane is promising to provide an outstanding approach for physiological detection, biomechanical energy harvesting, human-machine interaction, and self-powered monitoring systems. 

Versatile Ion‐Gel Fibrous Membrane for Energy‐Harvesting Iontronic Skin

Nonlinear optical (NLO) crystals are the vital components of laser science and technology, as they can convert lasers in common wavelengths into new wavelength bands for ultraviolet (UV), IR, and even terahertz laser output. Known UV NLO crystals mainly focus on crystals containing cations, but covalent crystals have rarely been reported. Here we report two covalent NLO crystals, B2 O3 I and B2 O3 II. According to the first-principles calculations, B2 O3 I and II have extremely short absorption edges of about 134 nm and 141 nm, large NLO coefficients of d22 =1.38 pm/V and d24 =0.702 pm/V, as well as sufficient birefringences of 0.037 and 0.031, respectively. Notably, the absorption edges are almost the shortest among NLO crystals. Meanwhile, the NLO coefficients are evidently larger than that of another well-known covalent NLO crystal α-SiO2 and are comparable to those of the commercial UV NLO crystal LiBO3 with Li+ cation. Furthermore, the birefringences are significantly larger than that of α-SiO2 , which are favorable to the phase matching for both crystals. These results reveal that B2 O3 I and B2 O3 II are excellent candidates for UV NLO applications. In-depth calculations are carried out to reveal the origin of excellent NLO properties. These covalent crystals provide a new direction for the research of UV NLO crystals.

Two Covalent Ultraviolet Nonlinear Optical Crystals

Linear Discriminant Analysis (LDA) is one of the most widely-used channel compensation techniques in current speaker and language recognition systems. In this study, we propose a technique of Between-Class Covariance Correction (BCC) to improve language recognition performance. This approach builds on the idea of WithinClass Covariance Correction (WCC), which was introduced as a means to compensate for mismatch between different development data-sets in speaker recognition. In BCC, we compute eigendirections representing the multimodal distributions of language i-vectors, and show that incorporating these directions in LDA leads to an improvement in recognition performance. Considering each cluster in the multi-modal i-vector distribution as a separate class, the betweenand within-cluster covariance matrices are used to update the global between-language covariance. This is in contrast to WCC, for which the within-class covariance is updated. Using the proposed method, a relative overall improvement of +8.4% Equal Error Rate (EER) is obtained on the 2015 NIST Language Recognition Evaluation (LRE) data. Our approach offers insights toward addressing the challenging problem of mismatch compensation, which has much wider applications in both speaker and language recognition.

Qian Zhang

Papers

A Clean, Facile, and StereospecificSynthesis of α-Oxoketene O,S-Acetals in Water

Preparation of YBCO superconducting thick films On MgO substrates by modified melt growth process

Versatile Ion‐Gel Fibrous Membrane for Energy‐Harvesting Iontronic Skin

Two Covalent Ultraviolet Nonlinear Optical Crystals

Between-Class Covariance Correction For Linear Discriminant Analysis in Language Recognition.