Photodynamics of quantum emitters in hexagonal boron nitride revealed by low-temperature spectroscopy

© 2017 American Physical Society. Quantum emitters in hexagonal boron nitride (hBN) have recently emerged as promising bright single photon sources. In this Rapid Communication we investigate in detail their optical properties at cryogenic temperatures. In particular, we perform temperature-resolved photoluminescence studies and measure photon coherence times from the hBN emitters. The obtained value of 81(1)ps translates to a width of ∼6.5GHz which is higher than the Fourier transform limited value of ∼32MHz. To account for the photodynamics of the emitter, we perform ultrafast spectral diffusion measurements that partially account for the coherence times. Our results provide important insight into the relaxation processes in quantum emitters in hBN which is mandatory to evaluate their applicability for quantum information processing

Solution processed amorphous silicon surface passivation layers

Amorphous silicon thin films, fabricated by thermal conversion of neopentasilane, were used to passivate crystalline silicon surfaces. The conversion is investigated using X ray and constant final state yield photoelectron spectroscopy, and minority charge carrier lifetime spectroscopy. Liquid processed amorphous silicon exhibits high Urbach energies from 90 to 120 meV and 200 meV lower optical band gaps than material prepared by plasma enhanced chemical vapor deposition. Applying a hydrogen plasma treatment, a minority charge carrier lifetime of 1.37 ms at an injection level of 1015 cm3 enabling an implied open circuit voltage of 724 mV was achieved, demonstrating excellent silicon surface passivatio

Wiring up pre-characterized single-photon emitters by laser lithography

Future quantum optical chips will likely be hybrid in nature and include many single-photon emitters, waveguides, filters, as well as single-photon detectors. Here, we introduce a scalable optical localization-selection-lithography procedure for wiring up a large number of single-photon emitters via polymeric photonic wire bonds in three dimensions. First, we localize and characterize nitrogen vacancies in nanodiamonds inside a solid photoresist exhibiting low background fluorescence. Next, without intermediate steps and using the same optical instrument, we perform aligned three-dimensional laser lithography. As a proof of concept, we design, fabricate, and characterize three-dimensional functional waveguide elements on an optical chip. Each element consists of one single-photon emitter centered in a crossed-arc waveguide configuration, allowing for integrated optical excitation and efficient background suppression at the same time

Differentially expressed microRNAs in maternal plasma for the noninvasive prenatal diagnosis of Down syndrome (trisomy 21).

OBJECTIVES: Most developmental processes are under the control of small regulatory RNAs called microRNAs (miRNAs). We hypothesize that different fetal developmental processes might be reflected by extracellular miRNAs in maternal plasma and may be utilized as biomarkers for the noninvasive prenatal diagnosis of chromosomal aneuploidies. In this proof-of-concept study, we report on the identification of extracellular miRNAs in maternal plasma of Down syndrome (DS) pregnancies. METHODS: Using high-throughput quantitative PCR (HT-qPCR), 1043 miRNAs were investigated in maternal plasma via comparison of seven DS pregnancies with age and fetal sex matched controls. RESULTS: Six hundred and ninety-five miRNAs were identified. Thirty-six significantly differentially expressed mature miRNAs were identified as potential biomarkers. Hierarchical cluster analysis of these miRNAs resulted in the clear discrimination of DS from euploid pregnancies. Gene targets of the differentially expressed miRNAs were enriched in signaling pathways such as mucin type-O-glycans, ECM-receptor interactions, TGF-beta, and endocytosis, which have been previously associated with DS. CONCLUSIONS: miRNAs are promising and stable biomarkers for a broad range of diseases and may allow a reliable, cost-efficient diagnostic tool for the noninvasive prenatal diagnosis of DS

Extracellular electrophysiological measurements of cooperative signals in astrocytes populations

Astrocytes are neuroglial cells that exhibit functional electrical properties sensitive to neuronal activity and capable of modulating neurotransmission. Thus, electrophysiological recordings of astroglial activity are very attractive to study the dynamics of glial signaling. This contribution reports on the use of ultra-sensitive planar electrodes combined with low noise and low frequency amplifiers that enable the detection of extracellular signals produced by primary cultures of astrocytes isolated from mouse cerebral cortex. Recorded activity is characterized by spontaneous bursts comprised of discrete signals with pronounced changes on the signal rate and amplitude. Weak and sporadic signals become synchronized and evolve with time to higher amplitude signals with a quasi-periodic behavior, revealing a cooperative signaling process. The methodology presented herewith enables the study of ionic fluctuations of population of cells, complementing the single cells observation by calcium imaging as well as by patch-clamp techniques.Portuguese Foundation for Science and Technology (FCT) [PTDC/EEI-AUT/5442/2014]; Instituto de Telecomunicacoes [UID/Multi/04326/2013]; Associated Laboratory - Institute of Nanoscience and Nanotechnology [POCI-01-0145-FEDER-016623]; [PTDC/CTM-NAN/3146/2014]info:eu-repo/semantics/publishedVersio

Anti-CRISPR AcrIIA5 Potently Inhibits All Cas9 Homologs Used for Genome Editing

CRISPR-Cas9 systems provide powerful tools for genome editing. However, optimal employment of this technology will require control of Cas9 activity so that the timing, tissue specificity, and accuracy of editing may be precisely modulated. Anti-CRISPR proteins, which are small, naturally occurring inhibitors of CRISPR-Cas systems, are well suited for this purpose. A number of anti-CRISPR proteins have been shown to potently inhibit subgroups of CRISPR-Cas9 systems, but their maximal inhibitory activity is generally restricted to specific Cas9 homologs. Since Cas9 homologs vary in important properties, differing Cas9s may be optimal for particular genome-editing applications. To facilitate the practical exploitation of multiple Cas9 homologs, here we identify one anti-CRISPR, called AcrIIA5, that potently inhibits nine diverse type II-A and type II-C Cas9 homologs, including those currently used for genome editing. We show that the activity of AcrIIA5 results in partial in vivo cleavage of a single-guide RNA (sgRNA), suggesting that its mechanism involves RNA interaction

Development of outcome measures for autoimmune dermatoses

Validated outcome measures are essential in monitoring disease severity. Specifically in dermatology, which relies heavily on the clinical evaluation of the patient and not on laboratory values and radiographic tests, outcome measures help standardize patient care. Validated cutaneous scoring systems, much like standardized laboratory values, facilitate disease management and follow therapeutic response. Several cutaneous autoimmune dermatoses, specifically cutaneous lupus erythematosus (CLE), dermatomyositis (DM), and pemphigus vulgaris (PV), lack such outcome measures. As a result, evaluation of disease severity and patients’ response to therapy over time is less reliable. Ultimately, patient care is compromised. These diseases, which are often chronic and relapsing and remitting, are also often refractory to treatment. Without outcome measures, new therapies cannot be systematically assessed in these diseases. Clinical trials that are completed without standardized outcome measures produce less reliable results. Therefore, the development of validated outcome measures in these autoimmune dermatoses is critical. However, the process of developing these tools is as important, if not more so, than their availability. This review examines the steps that should be considered when developing outcome measures, while further examining their importance in clinical practice and trials. Finally, this review more closely looks at CLE, DM, and PV and addresses the recent and ongoing progress that has been made in the development of their outcome measures

YAP1 withdrawal in hepatoblastoma drives therapeutic differentiation of tumor cells to functional hepatocyte-like cells

BACKGROUND and AIMS: Despite surgical and chemotherapeutic advances, the five-year survival rate for Stage IV Hepatoblastoma (HB), the predominant pediatric liver tumor, remains at 27%. YAP1 and beta-Catenin co-activation occurs in 80% of children\u27s HB; however, a lack of conditional genetic models precludes tumor maintenance exploration. Thus, the need for a targeted therapy remains unmet. Given the predominance of YAP1 and beta-Catenin activation in HB, we sought to evaluate YAP1 as a therapeutic target in HB. APPROACH and RESULTS: We engineered the first conditional HB murine model using hydrodynamic injection to deliver transposon plasmids encoding inducible YAP1(S127A) , constitutive beta-Catenin(DelN90) , and a luciferase reporter to murine liver. Tumor regression was evaluated using bioluminescent imaging, and tumor landscape characterized using RNA and ATAC sequencing, and DNA foot-printing. Here we show that YAP1(S127A) withdrawal mediates \u3e90% tumor regression with survival for 230+ days in mice. YAP1 (S127A) withdrawal promotes apoptosis in a subset of tumor cells and in remaining cells induces a cell fate switch driving therapeutic differentiation of HB tumors into Ki-67 negative hbHep cells with hepatocyte-like morphology and mature hepatocyte gene expression. YAP1 (S127A) withdrawal drives formation of hbHeps by modulating liver differentiation transcription factor (TF) occupancy. Indeed, tumor-derived hbHeps, consistent with their reprogrammed transcriptional landscape, regain partial hepatocyte function and rescue liver damage in mice. CONCLUSIONS: YAP1(S127A) withdrawal, without silencing oncogenic beta-Catenin, significantly regresses hepatoblastoma, providing the first in vivo data to support YAP1 as a therapeutic target for HB. YAP1(S127A) withdrawal alone sufficiently drives long-term regression in hepatoblastoma because it promotes cell death in a subset of tumor cells and modulates transcription factor occupancy to reverse the fate of residual tumor cells to mimic functional hepatocytes

Palmitic Acid Hydroxystearic Acids Activate GPR40, Which Is Involved in Their Beneficial Effects on Glucose Homeostasis.

Palmitic acid hydroxystearic acids (PAHSAs) are endogenous lipids with anti-diabetic and anti-inflammatory effects. PAHSA levels are reduced in serum and adipose tissue of insulin-resistant people and high-fat diet (HFD)-fed mice. Here, we investigated whether chronic PAHSA treatment enhances insulin sensitivity and which receptors mediate PAHSA effects. Chronic PAHSA administration in chow- and HFD-fed mice raises serum and tissue PAHSA levels ∼1.4- to 3-fold. This improves insulin sensitivity and glucose tolerance without altering body weight. PAHSA administration in chow-fed, but not HFD-fed, mice augments insulin and glucagon-like peptide (GLP-1) secretion. PAHSAs are selective agonists for GPR40, increasing Ca+2 flux, but not intracellular cyclic AMP. Blocking GPR40 reverses improvements in glucose tolerance and insulin sensitivity in PAHSA-treated chow- and HFD-fed mice and directly inhibits PAHSA augmentation of glucose-stimulated insulin secretion in human islets. In contrast, GLP-1 receptor blockade in PAHSA-treated chow-fed mice reduces PAHSA effects on glucose tolerance, but not on insulin sensitivity. Thus, PAHSAs activate GPR40, which is involved in their beneficial metabolic effects.Supported by NIH grants R01 DK43051, P30 DK57521 (B.B.K.), and R01 DK106210 (B.B.K. and A. Saghatelian); a grant from the JPB Foundation (B.B.K.); and T32DK07516 (B.B.K. and J.L.)

Comparative profiling identifies C13orf3 as a component of the Ska complex required for mammalian cell division

Proliferation of mammalian cells requires the coordinated function of many proteins to accurately divide a cell into two daughter cells. Several RNAi screens have identified previously uncharacterised genes that are implicated in mammalian cell division. The molecular function for these genes needs to be investigated to place them into pathways. Phenotypic profiling is a useful method to assign putative functions to uncharacterised genes. Here, we show that the analysis of protein localisation is useful to refine a phenotypic profile. We show the utility of this approach by defining a function of the previously uncharacterised gene C13orf3 during cell division. C13orf3 localises to centrosomes, the mitotic spindle, kinetochores, spindle midzone, and the cleavage furrow during cell division and is specifically phosphorylated during mitosis. Furthermore, C13orf3 is required for centrosome integrity and anaphase onset. Depletion by RNAi leads to mitotic arrest in metaphase with an activation of the spindle assembly checkpoint and loss of sister chromatid cohesion. Proteomic analyses identify C13orf3 (Ska3) as a new component of the Ska complex and show a direct interaction with a regulatory subunit of the protein phosphatase PP2A. All together, these data identify C13orf3 as an important factor for metaphase to anaphase progression and highlight the potential of combined RNAi screening and protein localisation analyses