Order parameter fluctuations at a buried quantum critical point

Quantum criticality is a central concept in condensed matter physics, but the direct observation of quantum critical fluctuations has remained elusive. Here we present an X-ray diffraction study of the charge density wave (CDW) in 2H-NbSe(2) at high pressure and low temperature, where we observe a broad regime of order parameter fluctuations that are controlled by proximity to a quantum critical point. X-rays can track the CDW despite the fact that the quantum critical regime is shrouded inside a superconducting phase; and in contrast to transport probes, allow direct measurement of the critical fluctuations of the charge order. Concurrent measurements of the crystal lattice point to a critical transition that is continuous in nature. Our results confirm the long-standing expectations of enhanced quantum fluctuations in low-dimensional systems, and may help to constrain theories of the quantum critical Fermi surface.     

歌诗达塞琳娜号与钻石公主号应对新型冠状病毒肺炎疫情应急处置措施的对比及启示

本文通过梳理歌诗达塞琳娜号与钻石公主号邮轮的基本情况及其在应对新型冠状病毒疫情时的紧急处理防控措施,探讨两艘邮轮在处置时的不同,并提出相关建议。     

Single-spin stochastic optical reconstruction microscopy

We experimentally demonstrate precision addressing of single-quantum emitters by combined optical microscopy and spin resonance techniques. To this end, we use nitrogen vacancy (NV) color centers in diamond confined within a few ten nanometers as individually resolvable quantum systems. By developing a stochastic optical reconstruction microscopy (STORM) technique for NV centers, we are able to simultaneously perform sub–diffraction-limit imaging and optically detected spin resonance (ODMR) measurements on NV spins. This allows the assignment of spin resonance spectra to individual NV center locations with nanometer-scale resolution and thus further improves spatial discrimination. For example, we resolved formerly indistinguishable emitters by their spectra. Furthermore, ODMR spectra contain metrology information allowing for sub–diffraction-limit sensing of, for instance, magnetic or electric fields with inherently parallel data acquisition. As an example, we have detected nuclear spins with nanometer-scale precision. Finally, we give prospects of how this technique can evolve into a fully parallel quantum sensor for nanometer resolution imaging of delocalized quantum correlations.Stochastic reconstruction microscopy (STORM) techniques have led to a wealth of applications in fluorescence imaging (1–3); for example, few ten-nanometers 3D spatial resolution (lateral 20 nm, axial 50 nm) has been achieved in cellular imaging. So far, STORM fluorophores have been used as markers to achieve nanoscale microscopy of specific targets (4). Here, we present a spin-based approach that promises to combine sub–diffraction-limit imaging via STORM and simultaneous sensing of various physical quantities.As a prominent multipurpose probe and highly photostable single emitter, we use the nitrogen vacancy (NV) spin defect in diamond. It can be applied for nanometer-scale scanning magnetometry (5–8) as well as magnetic imaging (9–14) (e.g., for imaging spin distributions, magnetic particles or organisms, or device intrinsic fields), the measurement of electric fields, and diamond lattice strain (15–18) (e.g., for imaging elementary charges or charge distributions, or for imaging strain fields induced by mechanical action on the diamond surface). Very recently, precise temperature measurements (19, 20) even in living cells (21) have been demonstrated.During the last decades, a variety of methods have been invented to circumvent the diffraction limit in farfield optical microscopy. One approach reduces the spatial region within a laser focus from which optical response of a single emitter is possible by exploiting optical nonlinearities. Examples are stimulated emission depletion (STED) and ground-state depletion (GSD) microscopy (22, 23). Another approach tailors the timing of optical response of several emitters from within a diffraction-limited spot to distinguish them in the time domain. One example is stochastic optical reconstruction microscopy (24–26). This latter technique is intrinsically parallel as it uses a CCD array for imaging and is therefore particularly suited for high-throughput imaging.STED and GSD microscopy, which are both scanning techniques, have been recently implemented for NV centers in diamond (27, 28) with resolutions down to a few nanometers (29). In addition, localization-based superresolution microscopy has been shown with NV centers in nanodiamonds (30).Here, we experimentally demonstrate STORM for NV centers in diamond as a new optical superresolution technique with wide-field parallel image acquisition for NV centers in bulk diamond. Our technique is based on recently gained profound knowledge about statistical charge state switching of single NV centers (31), and its scalability relies on the homogeneity of this charge state dynamics for NV centers in bulk diamond. Furthermore, we combine optical superresolution microscopy with high–spectral-resolution optically detected magnetic resonance (ODMR). On the one hand, we use the latter technique to assign magnetic resonance data to nanometer-scale locations, which is important for qubit or metrology applications (9–11, 32). On the other hand, different magnetic resonance fingerprints of closely spaced NV centers are used to further increase the already obtained superresolution, as demonstrated in refs. 32 and 33, which is important for emitter localization in imaging applications.     

The effectiveness of different root debridement modalities in open flap surgery

Abstract. It is unclear what degree of roughness or smoothness result from use of hand instruments alone in comparison to the use of hand instruments in combination with other aids and how it may effect the grade of cleanliness. The aim of this study was to determine in vivo whether the combination of hand instruments with other aids can increase the effectiveness of root debridement. 11 patients with holpless 4 mandibular incisors were involved in this study. After elevating a lingual and buccal mucoperiosteal flap, the 4 incisors were randomly treated with either: (1) no treatment (control); (2) 5-niin scaling (method 1); (3) 4-min scaling and 1-min instrumentation with a perio-diamond bur (15 μm) (method 2); (4) 3-min scaling, 1-min instrumentation with a perio-diamond bur (15 μm) and 1 min with an air abrasive system (method 3). The cleanliness of the surface was determined using the method of Eschler and -Rapley. The degree of roughness (Ra and Rt) were measured with a laser beam (computer supported optical surface sensor system). In addition, an SEM analysis was performed. With regard to the remaining calculus (surface cleanliness), method 3 yielded significantly better results than the other 2 methods. The roughness analyses also exhibited that method 3 is superior to methods 1 and 2. The qualitative results of the SEM investigations demonstrated the most homogenous and smooth surfaces with method 3. Root debridement in vivo was most significant using a combination of different treatment modalities (i. e., curettes, perio-diamond bur and air abrasive system).     

金刚石涂膜材料对成骨细胞骨钙素表达的影响

目的:探讨不同种植材料表面成骨细胞的功能状态.方法:用Wistar大鼠颅顶骨建立体外培养成骨细胞模型,将第三代成骨细胞接种到金刚石涂膜(CVD)、羟基磷灰石(HA)、纯钛(Ti)3种种植材料表面,通过反转录聚合酶链式扩增方法测定成骨细胞骨钙素mRNA.结果:CVD表面的成骨细胞骨钙素mRNA表达比HA出现早,Ti表面未见骨钙素mRNA表达.结论:CVD表面骨钙素的早期表达,推测其有成骨功能,适合成骨细胞生长.     

Substance loss caused by scaling with different sonic scaler inserts--an in vitro study

BACKGROUND, AIMS: Depending on the phase of periodontal treatment, power-driven inserts with different power levels are necessary: during initial treatment and flap operations, it must be possible to remove calculus which firmly adheres to the root surface with great efficiency; in contrast, gentle root-surface instrumentation has a high priority during maintenance treatment. Recently, modified sonic scaler inserts have been introduced: diamond-coated inserts for open flap operations and slim probe-shaped sonic scaler inserts for deplaqueing during maintenance. METHOD: We compared the substance removal by these inserts to that of a conventional insert. In a bench system which allows application force, stroke height, and width and frequency of instrumentation to be monitored and also permits assessment of the topography before and after instrumentation (yielding depth removal and removed volume), we instrumented aluminum rods in triplicate and bovine roots in a 5-fold repetition. RESULTS: With high application forces (1.0 N), the diamond-coated inserts removed 30 to 50% more substance than the conventional one. Except for the slim inserts, there was a significant linear relationship between increasing force and removed volume. Probe-shaped inserts do not remove considerable substance even with increasing pressures. CONCLUSIONS: Diamond-coated inserts remove tooth substance very effectively and must thus be handled with care: more pressure effects more removal. Probe-shaped inserts can be used without risk during maintenance visits.     

综合饮食疗法防治急性心肌梗塞便秘的临床研究

急性心肌梗塞 (AMI)患者发生便秘是导致心律失常、心衰及猝死等严重并发症的重要原因。综合饮食疗法是防治 AMI患者发生便秘的重要措施。依据综合饮食疗法与一般饮食将 59名 AMI患者随机分为综合饮食组为观察组 ,一般饮食组为对照组 ,两组便秘发生率比较 ,P <0 .0 5(x2 =6.0 6) ,结果表明 ,综合饮食能够明显降低 AMI患者便秘发生率 ,明显降低 AMI患者猝死 ,提高生存率     

用于航天器冷凝水处理的硼掺杂金刚石电极的制备及应用

目的 通过电化学催化氧化技术,将硼掺杂金刚石(BDD)电极高效应用于航天器冷凝水的处理工作中.方法 采用热丝化学气相沉积(HFCVD)技术在铌板上制备得到了大面积、均匀分布的BDD电极,并将制得的BDD电极用于降解模拟冷凝水实验.结果 模拟冷凝水处理量为200 mL,在电流密度为10,13,15 mA/cm2条件下,达到80％ TOC去除率分别需要150,120,100 min,功耗为7.48,11.4,14.59W;对处理后的冷凝水成分分析发现,冷凝水中原有的醇类物质被完全氧化;而且电极在连续运行之后也并未发现明显的剥落现象.结论 制得的BDD电极与二氧化铅电极相比,无论是在稳定性还是处理效率方面,都具有显著的优势.     

Bonding changes in hot fluid hydrogen at megabar pressures

Raman spectroscopy in laser-heated diamond anvil cells has been employed to probe the bonding state and phase diagram of dense hydrogen up to 140 GPa and 1,500 K. The measurements were made possible as a result of the development of new techniques for containing and probing the hot, dense fluid, which is of fundamental importance in physics, planetary science, and astrophysics. A pronounced discontinuous softening of the molecular vibron was found at elevated temperatures along with a large broadening and decrease in intensity of the roton bands. These phenomena indicate the existence of a state of the fluid having significantly modified intramolecular bonding. The results are consistent with the existence of a pressure-induced transformation in the fluid related to the presence of a temperature maximum in the melting line as a function of pressure.     

Effect of helium on structure and compression behavior of SiO2 glass

The behavior of volatiles is crucial for understanding the evolution of the Earth's interior, hydrosphere, and atmosphere. Noble gases as neutral species can serve as probes and be used for examining gas solubility in silicate melts and structural responses to any gas inclusion. Here, we report experimental results that reveal a strong effect of helium on the intermediate range structural order of SiO(2) glass and an unusually rigid behavior of the glass. The structure factor data show that the first sharp diffraction peak position of SiO(2) glass in helium medium remains essentially the same under pressures up to 18.6 GPa, suggesting that helium may have entered in the voids in SiO(2) glass under pressure. The dissolved helium makes the SiO(2) glass much less compressible at high pressures. GeO(2) glass and SiO(2) glass with H(2) as pressure medium do not display this effect. These observations suggest that the effect of helium on the structure and compression of SiO(2) glass is unique.