Sub-micron, Metal Gate, High-к Dielectric, Implant-free, Enhancement-mode III-V MOSFETs

The performance of 300nm, 500nm and 1μm metal gate, implant free, enhancement mode III-V MOSFETs are reported. Devices are realised using a 10nm MBE grown Ga2O3/(GaxGd1-x)2O3 high-κ (κ=20) dielectric stack grown upon a δ-doped AlGaAs/InGaAs/AlGaAs/GaAs heterostructure. Enhancement mode operation is maintained across the three reported gate lengths with a reduction in threshold voltage from 0.26 V to 0.08 V as the gate dimension is reduced from 1 μm to 300 nm. An increase in transconductance is also observed with reduced gate dimension. Maximum drain current of 420 μA/μm and extrinsic transconductance of 400 µS/µm are obtained from these devices. Gate leakage current of less than 100pA and subthreshold slope of 90 mV/decade were obtained for all gate lengths. These are believed to be the highest performance submicron enhancement mode III-V MOSFETs reported to date

Dielectric study on mixtures of ionic liquids

Ionic liquids are promising candidates for electrolytes in energy-storage systems. We demonstrate that mixing two ionic liquids allows to precisely tune their physical properties, like the dc conductivity. Moreover, these mixtures enable the gradual modification of the fragility parameter, which is believed to be a measure of the complexity of the energy landscape in supercooled liquids. The physical origin of this index is still under debate; therefore, mixing ionic liquids can provide further insights. From the chemical point of view, tuning ionic liquids via mixing is an easy and thus an economic way. For this study, we performed detailed investigations by broadband dielectric spectroscopy and differential scanning calorimetry on two mixing series of ionic liquids. One series combines an imidazole based with a pyridine based ionic liquid and the other two different anions in an imidazole based ionic liquid. The analysis of the glass-transition temperatures and the thorough evaluations of the measured dielectric permittivity and conductivity spectra reveal that the dynamics in mixtures of ionic liquids are well defined by the fractions of their parent compounds.Comment: 9 pages, 4 figure

Sequential Sparse NMF

Nonnegative Matrix Factorization (NMF) is a standard tool for data analysis. An important variant is the Sparse NMF problem. A natural measure of sparsity is the L₀ norm, however its optimization is NP-hard. Here, we consider a sparsity measure linear in the ratio of the L₁ and L₂ norms, and propose an efficient algorithm to handle the norm constraints which arise when optimizing this measure. Although algorithms for solving these are available, they are typically inefficient. We present experimental evidence that our new algorithm performs an order of magnitude faster compared to the previous state-of-the-art

Sequential Sparse NMF

Nonnegative Matrix Factorization (NMF) is a standard tool for data analysis. An important variant is the Sparse NMF problem. A natural measure of sparsity is the L₀ norm, however its optimization is NP-hard. Here, we consider a sparsity measure linear in the ratio of the L₁ and L₂ norms, and propose an efficient algorithm to handle the norm constraints which arise when optimizing this measure. Although algorithms for solving these are available, they are typically inefficient. We present experimental evidence that our new algorithm performs an order of magnitude faster compared to the previous state-of-the-art

Langzeitwirkung von Bodenschutzkalkungen auf die Waldvegetation - Einfluss von Bodeneigenschaften und Lichtangebot

Um die Frage einer Langzeitwirkung von Kalkungsmaßnahmen auf die Waldvegetation zu beantworten, wurden vegetationskundliche und bodenchemische Daten aus den Jahren 1990, 1997/98 und 2015 von niedersächsischen Versuchsflächen ausgewertet. Die aus jeweils einer Kalkungs- und einer Nullparzelle bestehenden Kalkungspärchen, umfassen ein weites Spektrum von Standorten und Hauptbaumarten (Fichte, Kiefer, Buche und Eiche). Die Kalkungsparzellen wurden mit praxisüblichen Dosierungen von 3 bis 4 t CaCO3-Äquivalenten Trockensubstanz pro Hektar erstmals Anfang der 1980er Jahre und nochmals 1993 gekalkt. Weiterhin wurde das Lichtangebot im Jahr 2016 auf den vegetationskundlichen Aufnahmeflächen mit einem Solariscope gemessen. Ein Ziel dieser Untersuchung war es herauszufinden, ob sich eine zunehmende Wiederversauerung der Oberböden 22 Jahre nach der letzten Bodenschutzkalkung auf die Waldbodenvegetation auswirkt. Als Kenngrößen wurden die Basensättigung, der pH-Wert, die Austauschkapazität sowie die austauschbaren Vorräte an Calcium und Magnesium herangezogen. Zusätzlich wurde das in erster Linie von den Hauptbaumarten und deren Behandlung abhängige Lichtangebot in der Auswertung mit berücksichtigt. Im Ergebnis zeigt sich, dass praxisübliche Kalkungsmaßnahmen die Waldvegetation langfristig verändern. Für alle drei Untersuchungszeitpunkte konnten auf den Kalkungsparzellen signifikant höhere Gefäßpflanzen-Artenzahlen, höhere Anteile von walduntypischen Offenlandarten und höhere mittlere Stickstoffzahlen festgestellt werden. Dies bestätigen im Wesentlichen die Ergebnisse einer Auswertung, welche bereits auf Basis der Vegetationsdaten von 1990 und 1997 durchgeführt wurde (1). Anhand der bodenchemischen Daten ist zwar eine zunehmende Oberbodenversauerung seit der letzten Kalkung feststellbar, doch ist diese Veränderung offenbar noch zu gering, um sich entscheidend auf die Pflanzenartenzusammensetzung auszuwirken. Dennoch zeigt sich, dass der Einfluss der Kalkung auf die Waldvegetation abnimmt, während der Einfluss der Hauptbaumarten zunimmt. Hierbei weisen Buchenwälder mit geringem Lichtangebot am Waldboden die geringsten und Kiefernwälder mit hohem Lichtangebot die größten Unterschiede zwischen Kalkungs- und Nullparzelle hinsichtlich Gefäßpflanzen- und Offenlandartenzahl sowie hinsichtlich der mittleren Stickstoffzeigerwerte auf

Enhancement Mode n-MOSFET with High-κ Dielectric on GaAs Substrate

In this paper, we report MOS heterostructures grown by molecular beam epitaxy on III-V substrates, employing a high-κ dielectric stack comprised of gallium oxide and gadolinium gallium oxide. Mobilities exceeding 12,000 and 6,000 cm2/Vs, for sheet carrier concentration ns of about 2.5x1012 cm-2 were measured on MOSFET structures on InP and GaAs substrates, respectively. These structures were designed for enhancement mode operation and include a 10 nm thick strained InGa1-xAs channel layer with In mole fraction x of 0.3 and 0.75 on GaAs and InP substrates, respectively

Determining the electronic performance limitations in top-down fabricated Si nanowires with mean widths down to 4 nm

Silicon nanowires have been patterned with mean widths down to 4 nm using top-down lithography and dry etching. Performance-limiting scattering processes have been measured directly which provide new insight into the electronic conduction mechanisms within the nanowires. Results demonstrate a transition from 3-dimensional (3D) to 2D and then 1D as the nanowire mean widths are reduced from 12 to 4 nm. The importance of high quality surface passivation is demonstrated by a lack of significant donor deactivation, resulting in neutral impurity scattering ultimately limiting the electronic performance. The results indicate the important parameters requiring optimization when fabricating nanowires with atomic dimensions

Interleukin-1β sequesters hypoxia inducible factor 2α to the primary cilium.

BACKGROUND: The primary cilium coordinates signalling in development, health and disease. Previously we have shown that the cilium is essential for the anabolic response to loading and the inflammatory response to interleukin-1β (IL-1β). We have also shown the primary cilium elongates in response to IL-1β exposure. Both anabolic phenotype and inflammatory pathology are proposed to be dependent on hypoxia-inducible factor 2 alpha (HIF-2α). The present study tests the hypothesis that an association exists between the primary cilium and HIFs in inflammatory signalling. RESULTS: Here we show, in articular chondrocytes, that IL-1β-induces primary cilia elongation with alterations to cilia trafficking of arl13b. This elongation is associated with a transient increase in HIF-2α expression and accumulation in the primary cilium. Prolyl hydroxylase inhibition results in primary cilia elongation also associated with accumulation of HIF-2α in the ciliary base and axoneme. This recruitment and the associated cilia elongation is not inhibited by blockade of HIFα transcription activity or rescue of basal HIF-2α expression. Hypomorphic mutation to intraflagellar transport protein IFT88 results in limited ciliogenesis. This is associated with increased HIF-2α expression and inhibited response to prolyl hydroxylase inhibition. CONCLUSIONS: These findings suggest that ciliary sequestration of HIF-2α provides negative regulation of HIF-2α expression and potentially activity. This study indicates, for the first time, that the primary cilium regulates HIF signalling during inflammation