Properties of Erbium and Ytterbium Doped Gallium Nitride Layers Fabricated by Magnetron Sputtering

We report about some properties of erbium and erbium/ytterbium doped gallium nitride (GaN) layers fabricated by magnetron sputtering onsilicon, quartz and Corning glass substrates. For fabricating GaN layers two types of targets were used - gallium in a stainless steel cup anda Ga2O3 target. Deposition was carried out in the Ar+N2 gas mixture. For erbium and ytterbium doping into GaN layers, erbium metallicpowder and ytterbium powder or Er2O3 and Yb2O3 pellets were laid on the top of the target. The samples were characterized by X-raydiffraction (XRD), photoluminescence spectra and nuclear analytical methods. While the use of a metallic gallium target ensured thedeposition of well-developed polycrystalline layers, the use of gallium oxide target provided GaN films with poorly developed crystals. Bothapproaches enabled doping with erbium and ytterbium ions during deposition, and typical emission at 1 530 nm due to the Er3+ intra-4f 4I13/2 → 4I15/2 transition was observed

Properties of Erbium Doped Hydrogenated Amorphous Carbon Layers Fabricated by Sputtering and Plasma Assisted Chemical Vapor Deposition

We report about properties of carbon layers doped with Er3+ ions fabricated by Plasma Assisted Chemical Vapor Deposition (PACVD) and by sputtering on silicon or glass substrates. The structure of the samples was characterized by X-ray diffraction and their composition was determined by Rutherford Backscattering Spectroscopy and Elastic Recoil Detection Analysis. The Absorbance spectrum was taken in the spectral range from 400 nm to 600 nm. Photoluminescence spectra were obtained using two types of Ar laser (λex=514.5 nm, lex=488 nm) and also using a semiconductor laser (λex=980 nm). Samples fabricated by magnetron sputtering exhibited typical emission at 1530 nm when pumped at 514.5 nm.&nbsp

Optical Properties of Erbium and Erbium/Ytterbium Doped Polymethylmethacrylate

In this paper we report on the fabrication and properties of Er3 and Er3/Yb3 doped Polymethylmethacrylate (PMMA) layers. The reported layers were fabricated by spin coating on silicon or on quartz substrates. Infrared spectroscopy was used for an investigation of O-H stretching vibration. Measurement were made of the transmission spectra in the wavelength ranges from 350 to 700 nm for the Er3 doped samples and from 900 to 1040 nm for the Yb3 doped samples. The refractive indices were investigated in the spectral range from 300 to 1100 nm using optical ellipsometry and the photoluminescence spectra were measured in the infrared region

eIF4GI links nutrient sensing by mTOR to cell proliferation and inhibition of autophagy

Translation initiation factors have complex functions in cells that are not yet understood. We show that depletion of initiation factor eIF4GI only modestly reduces overall protein synthesis in cells, but phenocopies nutrient starvation or inhibition of protein kinase mTOR, a key nutrient sensor. eIF4GI depletion impairs cell proliferation, bioenergetics, and mitochondrial activity, thereby promoting autophagy. Translation of mRNAs involved in cell growth, proliferation, and bioenergetics were selectively inhibited by reduction of eIF4GI, as was the mRNA encoding Skp2 that inhibits p27, whereas catabolic pathway factors were increased. Depletion or overexpression of other eIF4G family members did not recapitulate these results. The majority of mRNAs that were translationally impaired with eIF4GI depletion were excluded from polyribosomes due to the presence of multiple upstream open reading frames and low mRNA abundance. These results suggest that the high levels of eIF4GI observed in many breast cancers might act to specifically increase proliferation, prevent autophagy, and release tumor cells from control by nutrient sensing

Brain abscess and stroke in children and adults with hereditary hemorrhagic telangiectasia: Analysis of a large national claims database

BACKGROUND AND OBJECTIVES: Hereditary hemorrhagic telangiectasia (HHT) is an inherited disease associated with pathogenic variants in transforming growth factor-β signaling pathway-related genes, resulting in abnormal vascular development in various organs. Brain arteriovenous malformations (AVMs) may lead to intracranial hemorrhage, and brain abscess or ischemic stroke may result from right to left shunting via pulmonary AVMs. We aimed to investigate the risk for these severe complications in both adults and children with HHT. METHODS: We conducted a case-control study among participants aged 1-64 years in the MarketScan Commercial (2006-2019) and Multistate Medicaid Databases (2011-2019). We identified cases with HHT using RESULTS: A total of 5,796 patients with HHT, of whom 588 were children (age younger than 16 years), were matched with 57,960 controls. There was an increased incidence of brain abscesses in HHT cases compared with controls, with an RR of 35.6 (95% CI 15.4-82.5). No brain abscesses were recorded in children aged 15 years or younger. Hemorrhagic strokes/subarachnoid hemorrhages were more common in HHT cases, with an RR of 4.01 (95% CI 2.8-5.7) in adults and 60.2 (95% CI 7.2-500.4) in children. Ischemic strokes were also more common in cases, with an RR of 3.7 (95% CI, 3.0-4.5) in adults and 70.4 (95% CI 8.7-572.3) in children. DISCUSSION: We observed a much higher incidence of severe CNS vascular complications in patients with HHT, particularly in children. Although a higher incidence of brain abscesses was noted in adult patients with HHT, no brain abscesses were recorded in children, a result that may be considered when surveillance recommendations for this population are revisited

Fuel cell applications for novel metalloporphyrin catalysts

This project utilized Computer-Aided Molecular Design (CAMD) to develop a new class of metalloporphyrin materials for use as catalysts for two fuel cell reactions. The first reaction is the reduction of oxygen at the fuel cell cathode, and this reaction was the main focus of the research. The second reaction we attempted to catalyze was the oxidation of methanol at the anode. Two classes of novel metalloporphyrins were developed. The first class comprised the dodecaphenylporphyrins whose steric bulk forces them into a non-planar geometry having a pocket where oxygen or methanol is more tightly bound to the porphyrin than it is in the case of planar porphyrins. Significant improvements in the catalytic reduction of oxygen by the dodecaphenyl porphyrins were measured in electrochemical cells. The dodecaphenylporphyrins were further modified by fluorinating the peripheral phenyl groups to varying degrees. The fluorination strongly affected their redox potential, but no effect on their catalytic activity towards oxygen was observed. The second class of porphyrin catalysts was a series of hydrogen-bonding porphyrins whose interaction with oxygen is enhanced. Enhancements in the interaction of oxygen with the porphyrins having hydrogen bonding groups were observed spectroscopically. Computer modeling was performed using Molecular Simulations new CERIUS2 Version 1.6 and a research version of POLYGRAF from Bill Goddard`s research group at the California Institute of Technology. We reoptimized the force field because of an error that was in POLYGRAF and corrected a problem in treatment of the metal in early versions of the program. This improved force field was reported in a J. Am. Chem. Soc. manuscript. Experimental measurements made on the newly developed catalysts included the electrochemical testing in a fuel cell configuration and spectroscopic measurements (UV-Vis, Raman and XPS) to characterize the catalysts

Tailoring the Nanostructure Anodically Formed in the Passive Oxide on Aluminum -Relevance to Localized Corrosion Initiation

Anodic processes at a passive metal surface like aluminum could be envisioned as being initiated or controlled by nano-scale structural changes within the metal's surface oxide. Examples include proposed roles for nanostructure formation in the pit initiation for Al corrosion (1,2), void formation on pit initiation of Al during anodic etching (3), and possibly deformationinduced nanostructure in pore formation in Al (4). Characterizing the nanostructure present in the passive oxide and learning how to control structure formation offers an opportunity to electrochemically explore deterministic relationships between known structure and anodic event initiation. Recent work has shown that voids can nucleate at the aluminum/aluminum oxide interface and grow into the passive oxide at standard slow rate polarization in moderate chloride solutions well below the onset for pit initiation (5). Analytical transmission electron microscopy argues that these voids are encapsulated absence of matter produced by cation and anion vacancy saturation and coalescence in the oxide. Atomic force microscopy coupled with scanning electron microscopy show that these voids can transition to pores at efficiencies up to 20% of the void population or 2x10 10 cm -2 prior to the initiation of pitting. These results demonstrate that interfacial voids are formed as a result of ion transport through the passive oxide and provide a foundation for exploring their role in pit initiation. Most of this work has focused on anhydrous oxides to model the initial passive oxide on Al. These oxides are formed on atomically clean (vacuum prepared) bulk Al surfaces (both single and poly-crystalline) and nanocrystalline evaporated Al films exposed to O 2 at room temperature and atmospheric pressure. The length of time for equilibration of the model oxide in a deaerated electrolyte is the factor that controls the extent to which voids and pores form. Time-of-flight secondary ion mass spectrometric (TOF-SIMS) measurements show that solution equilibration produces a slow growth of the initial 3 nm oxide up to an equilibration value of 4.5 nm over a period of 16 hours. Anodic polarization of the initial oxide produces a near-equivalent final thickness over a much faster time scale. It is this more rapidly formed film that exhibits a larger passive charge density (and larger void and pore densities) that exceeds values expected for uniform growth to its measured limiting thickness. The excess charge density has to be consumed either by vacancy generation (and subsequent coalescence) or dissolution. Dissolution alone appears an unlikely explanation given reported rates in a mixed chloride/borate electrolyte (6). An initial attempt can be made to identify whether these structures play a role in pit initiation by exploiting this equilibration time effect. In limited cases, we have been able to show that higher density void nucleation produced by using shorter equilibration times can lead to high densities of pores that maintain a minimum (< 20 nm) diameter. It is this high density of transitioning features that might be expected to increase the probability of pitting event when compared the absence of detectable pores for long equilibration times. We have observed as much as a 200 mV shift in the stable mean pitting potential to more active values with decreased equilibration time. Where these results provide an indication that voids and pores can contribute to pitting, they do not identify the necessity for these structures in a generalized pitting mechanism. More recent work is focused on exploiting how the passive oxide is formed in an effort to tailor its resulting ion transmission characteristics and range of nanostructure exhibited. Our eventual goal is to learn how to control this nanostructure to a level where statistical studies of current transient events (i.e. metastable pitting events) can be correlated to characteristics of the feature population. Hydrous oxides produced by exposure of atomically clean Al to pure water vapor with and without subsequent dehydration show even larger variation in passive charge density response with anodic polarization. These results indicate that the initial characteristics of the oxide prior to immersion in the electrolyte could provide a wider range of control of structure density and size. The use of alternate electrolytes containing borate produces unique differences in the nanostructure population. One quite interesting effect of the borate anion is that TOF-SIMS and x-ray photoelectron spectroscopy show it attenuates the equilibrium concentration of chloride within the outer layer and/or at the barrier oxide interface in the passive oxide. Electrochemical impedance measurements indicate a reduced defect concentration within the barrier layer when borate is present while electron microscopy shows the void population is suppressed when borate anion is present. These results suggest that electrolyte composition can be used to control the nanostructure population as well

Modelling mutational landscapes of human cancers in vitro

Experimental models that recapitulate mutational landscapes of human cancers are needed to decipher the rapidly expanding data on human somatic mutations. We demonstrate that mutation patterns in immortalised cell lines derived from primary murine embryonic fibroblasts (MEFs) exposed in vitro to carcinogens recapitulate key features of mutational signatures observed in human cancers. In experiments with several cancer-causing agents we obtained high genome-wide concordance between human tumour mutation data and in vitro data with respect to predominant substitution types, strand bias and sequence context. Moreover, we found signature mutations in well-studied human cancer driver genes. To explore endogenous mutagenesis, we used MEFs ectopically expressing activation-induced cytidine deaminase (AID) and observed an excess of AID signature mutations in immortalised cell lines compared to their non-transgenic counterparts. MEF immortalisation is thus a simple and powerful strategy for modelling cancer mutation landscapes that facilitates the interpretation of human tumour genome-wide sequencing data

Selective targeting of activating and inhibitory Smads by distinct WWP2 ubiquitin ligase isoforms differentially modulates TGFβ signalling and EMT

Ubiquitin-dependent mechanisms have emerged as essential regulatory elements controlling cellular levels of Smads and TGFß-dependent biological outputs such as epithelial–mesenchymal transition (EMT). In this study, we identify a HECT E3 ubiquitin ligase known as WWP2 (Full-length WWP2-FL), together with two WWP2 isoforms (N-terminal, WWP2-N; C-terminal WWP2-C), as novel Smad-binding partners. We show that WWP2-FL interacts exclusively with Smad2, Smad3 and Smad7 in the TGFß pathway. Interestingly, the WWP2-N isoform interacts with Smad2 and Smad3, whereas WWP2-C interacts only with Smad7. In addition, WWP2-FL and WWP2-C have a preference for Smad7 based on protein turnover and ubiquitination studies. Unexpectedly, we also find that WWP2-N, which lacks the HECT ubiquitin ligase domain, can also interact with WWP2-FL in a TGFß-regulated manner and activate endogenous WWP2 ubiquitin ligase activity causing degradation of unstimulated Smad2 and Smad3. Consistent with our protein interaction data, overexpression and knockdown approaches reveal that WWP2 isoforms differentially modulate TGFß-dependent transcription and EMT. Finally, we show that selective disruption of WWP2 interactions with inhibitory Smad7 can stabilise Smad7 protein levels and prevent TGFß-induced EMT. Collectively, our data suggest that WWP2-N can stimulate WWP2-FL leading to increased activity against unstimulated Smad2 and Smad3, and that Smad7 is a preferred substrate for WWP2-FL and WWP2-C following prolonged TGFß stimulation. Significantly, this is the first report of an interdependent biological role for distinct HECT E3 ubiquitin ligase isoforms, and highlights an entirely novel regulatory paradigm that selectively limits the level of inhibitory and activating Smads

Layers of Metal Nanoparticles on Semiconductors Deposited by Electrophoresis from Solutions with Reverse Micelles

Pd nanoparticles were prepared with reverse micelles of water/AOT/isooctane solution and deposited onto silicon or InP substrates by electrophoresis. A large change of capacitance-voltage characteristics of mercury contacts on a semiconductor was found after Pd deposition. This change could be modified when the Pd deposition is followed by a partial removal of the deposited AOT. The deposited Pd nanoparticles were investigated by optical mictroscopy, SIMS and SEM. Finally, Schottky diodes with barrier height as high as 1.07 eV were prepared by deposition of Pd nanoparticles on n-type InP and by a partial removal of superfluous AOT. These diodes are prospective structures for further testing as hydrogen sensors