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Optically active point defects in wide-bandgap crystals are leading building blocks for quantum information technologies including quantum processors, repeaters, simulators, and sensors. Although defects and impurities are ubiquitous in all materials, select defect configurations in certain materials harbor coherent electronic and nuclear quantum states that can be optically and electronically addressed in solid-state devices, in some cases even at room temperature. Historically, the study of quantum point defects has been limited to a relatively small set of host materials and defect systems. In this article, we consider the potential for identifying defects in new materials, either to advance known applications in quantum science or to enable entirely new capabilities. We propose that, in principle, it should be possible to reverse the historical approach, which is partially based on accidental discovery, in order to quantum defects with desired properties suitable for specific applications. We discuss the biggest obstacles on the road towards this goal, in particular those related to theoretical prediction, materials growth and processing, and experimental characterization.

In many physical problems several scales are present in space or time, caused by inhomogeneity of the medium or complexity of the mechanical process. A fundamental approach is to first construct micro-scale models, and then deduce the macro-scale laws and the constitutive relations by properly averaging over the micro-scale. The perturbation method of multiple scales can be used to derive averaged equations for a much larger scale from considerations of the small scales. In the mechanics of multiscale media, the analytical scheme of upscaling is known as the Theory of Homogenization.

Solid state quantum defects are promising candidates for scalable quantum information systems which can be seamlessly integrated with the conventional semiconductor electronic devices within the 3D monolithically integrated hybrid classical-quantum devices. Diamond nitrogen-vacancy (NV) center defects are the representative examples, but the controlled positioning of an NV center within bulk diamond is an outstanding challenge. Furthermore, quantum defect properties may not be easily tuned for bulk crystalline quantum defects. In comparison, 2D semiconductors, such as transition metal dichalcogenides (TMDs), are promising solid platform to host a quantum defect with tunable properties and a possibility of position control. Here, we computationally discover a promising defect family for spin qubit realization in 2D TMDs. The defects consist of transition metal atoms substituted at chalcogen sites with desirable spin-triplet ground state, zero-field splitting in the tens of GHz, and strong zero-phonon coupling to optical transitions in the highly desirable telecom band. Defect centers in two-dimensional materials has shown promise for applications in quantum information and sensing. Lee et al. computationally discover a class of substitutional defect centers in monolayer transition metal dichalcogenides with promising qubit characteristics operating at telecom wavelengths.

Magnetic proximity effects are integral to manipulating spintronic1,2, superconducting3,4, excitonic5 and topological phenomena6–8 in heterostructures. These effects are highly sensitive to the interfacial electronic properties, such as electron wavefunction overlap and band alignment. The recent emergence of magnetic two-dimensional materials opens new possibilities for exploring proximity effects in van der Waals heterostructures9–12. In particular, atomically thin CrI3 exhibits layered antiferromagnetism, in which adjacent ferromagnetic monolayers are antiferromagnetically coupled9. Here we report a layer-resolved magnetic proximity effect in heterostructures formed by monolayer WSe2 and bi/trilayer CrI3. By controlling the individual layer magnetization in CrI3 with a magnetic field, we show that the spin-dependent charge transfer between WSe2 and CrI3 is dominated by the interfacial CrI3 layer, while the proximity exchange field is highly sensitive to the layered magnetic structure as a whole. In combination with reflective magnetic circular dichroism measurements, these properties allow the use of monolayer WSe2 as a spatially sensitive magnetic sensor to map out layered antiferromagnetic domain structures at zero magnetic field as well as antiferromagnetic/ferromagnetic domains at finite magnetic fields. Our work reveals a way to control proximity effects and probe interfacial magnetic order via van der Waals engineering13.Controlling the individual layer magnetization in CrI3 enables the observation of a layer-resolved magnetic proximity effect in WSe2/CrI3 heterostructures.

Integrated quantum photonic technologies are key for future applications in quantum information1,2, ultralow-power opto-electronics3 and sensing4. As individual quantum bits, nitrogen-vacancy centres in diamond are among the most promising solid-state systems identified to date, because of their long-lived electron and nuclear spin coherence, and capability for individual optical initialization, readout and information storage 5-9. The major outstanding hurdle lies in interconnecting many nitrogen vacancies for large-scale computation. One of the most promising approaches in this regard is to couple them to optical resonators, which can be further interconnected in a photonic network. Here10-12, we demonstrate coupling of the zero-phonon line of individual nitrogen vacancies to the modes of microring resonators fabricated in single-crystal diamond. Zero-phonon line enhancement by more than a factor of 10 is estimated from lifetime measurements. The devices are fabricated using standard semiconductor techniques and off-the-shelf materials, thus enabling integrated diamond photonics. © 2011 Macmillan Publishers Limited. All rights reserved.

The existence of stress de-activation was further supported by the observation that an external mechanical stress on adhering bacteria enhances the antimicrobial efficacy of quaternary ammonium compounds in solution [17]. Since the great majority of bacterial strains and species possess a negative surface charge [18], strong adhesion forces can be found on positively charged surfaces, such as quaternary ammonium-coated surfaces that are known to kill bacteria upon contact [19] in this \"lethal\" regime of strong adhesion forces (see Figure 1).\\n EPS was stained with calcofluor white, rendering blue fluorescence. Upon first approach of a bacterium to a surface, it becomes attached to a layer of highly viscous water adjacent to the surface that is subsequently slowly penetrated to allow stronger contact with the surface, after which protein structures on the cell surface re-orient themselves to allow optimal binding. Since it is unlikely that metabolic processes and phenotypic changes occur within minutes, we envisage that adhesion forces after physico-chemical strengthening represent the transition forces between the three adhesion force regimes depicted in Figure 1.

Biomaterials for the restoration of oral function are prone to biofilm formation, affecting oral health. Oral bacteria adhere to hydrophobic and hydrophilic surfaces, but due to fluctuating shear, little biofilm accumulates on hydrophobic surfaces in vivo. More biofilm accumulates on rough than on smooth surfaces. Oral biofilms mostly consist of multiple bacterial strains, but Candida species are found on acrylic dentures. Biofilms on gold and amalgam in vivo are thick and fully covering, but barely viable. Biofilms on ceramics are thin and highly viable. Biofilms on composites and glass-ionomer cements cause surface deterioration, which enhances biofilm formation again. Residual monomer release from composites influences biofilm growth in vitro, but effects in vivo are less pronounced, probably due to the large volume of saliva into which compounds are released and its continuous refreshment. Similarly, conflicting results have been reported on effects of fluoride release from glass-ionomer cements. Finally, biomaterial-associated infection of implants and devices elsewhere in the body is compared with oral biofilm formation. Biomaterial modifications to discourage biofilm formation on implants and devices are critically discussed for possible applications in dentistry. It is concluded that, for dental applications, antimicrobial coatings killing bacteria upon contact are more promising than antimicrobial-releasing coatings.

Nanoparticles possess unique features due to their small size and can be composed of different surface chemistries. Carbon quantum dots possess several unique physico-chemical and antibacterial activities. This review provides an overview of different methods to prepare carbon quantum dots from different carbon sources in order to provide guidelines for choosing methods and carbon sources that yield carbon quantum dots with optimal antibacterial efficacy. Antibacterial activities of carbon quantum dots predominantly involve cell wall damage and disruption of the matrix of infectious biofilms through reactive oxygen species (ROS) generation to cause dispersal of infecting pathogens that enhance their susceptibility to antibiotics. Quaternized carbon quantum dots from organic carbon sources have been found to be equally efficacious for controlling wound infection and pneumonia in rodents as antibiotics. Carbon quantum dots derived through heating of natural carbon sources can inherit properties that resemble those of the carbon sources they are derived from. This makes antibiotics, medicinal herbs and plants or probiotic bacteria ideal sources for the synthesis of antibacterial carbon quantum dots. Importantly, carbon quantum dots have been suggested to yield a lower chance of inducing bacterial resistance than antibiotics, making carbon quantum dots attractive for large scale clinical use.

γ-Secretase has primarily been studied in neurons, whereas increasing evidence highlights its importance in microglia. Previous research has shown that the pharmacological inhibition of γ-secretase impairs microglial phagocytic activity. In this study, we used a genetically encoded Förster resonance energy transfer (FRET)-based biosensor to record γ-secretase activity, aiming to determine if naturally occurring cell-by-cell variations in endogenous γ-secretase activity are associated with phagocytic activity. Using the Notch1 N100 Y-T biosensor, we found that the regulation of endogenous γ-secretase activity varies among individual BV-2 microglial cells. Our multiplexed time-lapse imaging revealed that the phagocytosis of E. coli bioparticles was impaired in cells with lower γ-secretase activity compared to those with higher activity. Complementary biochemical analysis, utilizing Zymosan bioparticles and fluorescence-activated cell sorting (FACS), further demonstrated that cells with reduced phagocytic activity exhibited decreased endogenous γ-secretase activity. Collectively, our confirmatory study supports previous findings that microglial phagocytic activity is closely linked to γ-secretase and emphasizes the essential role of γ-secretase in microglia.

Our unique multiplexed imaging assays employing FRET biosensors have previously detected that γ-secretase processes APP C99 primarily in late endosomes and lysosomes in live/intact neurons. Moreover we have shown that Aβ peptides are enriched in the same subcellular loci. Given that γ-secretase is integrated into the membrane bilayer and functionally links to lipid membrane properties in vitro, it is presumable that γ-secretase function correlates with endosome and lysosome membrane properties in live/intact cells. In the present study, we show using unique live-cell imaging and biochemical assays that the endo-lysosomal membrane in primary neurons is more disordered and, as a result, more permeable than in CHO cells. Interestingly, γ-secretase processivity is decreased in primary neurons, resulting in the predominant production of long Aβ42 instead of short Aβ38. In contrast, CHO cells favor Aβ38 over the Aβ42 generation. Our findings are consistent with the previous in vitro studies, demonstrating the functional interaction between lipid membrane properties and γ-secretase and provide further evidence that γ-secretase acts in late endosomes and lysosomes in live/intact cells.