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Wafer-scale high-κ HfO<sub>2</sub> dielectric films with sub-5-Å equivalent oxide thickness for 2D MoS<sub>2</sub> transistors
No full textHigh-κ gate dielectrics are indispensable in modern transistor technology and play a pivotal role in efficient capacitive gating and suppression of leakage currents. However, the realization of industry-compatible high-κ gate dielectrics at a sub-5-Å equivalent oxide thickness (EOT) remains challenging. Here we report the realization of 1.3-nm thick hafnium oxide (HfO2) dielectrics via an industry-compatible multiple oxidation atomic layer deposition process at 200 °C. A low EOT down to 2.5 Å is demonstrated for 1.3-nm thick HfO2 dielectrics on metal gates with a low leakage current of 10−6 A/cm2 and a robust breakdown electric field of ~22.3 MV/cm. Remarkably, such low EOT high-κ/metal gates can be directly implanted into emerging two-dimensional (2D) transistors and low-power logic circuits on 8-inch wafer scale to showcase their potentials. The as-fabricated molybdenum disulfide (MoS2) transistors exhibit a large on-state current density of 260 µA/µm at source-drain bias of 0.5 V, a high on/off ratio of 108, an average subthreshold slope (SS) of 75 mV/dec, and small capacitance equivalent thickness (CET) values of 0.34 nm for gate-first transistors and 0.50 nm for gate-last transistors. Our ultra-scaled dielectrics hold significant promise for advanced semiconductor fabrication processes towards the angstrom era
Dispersive Fluorine/Bromine Interactions as Key Selectivity Determinant: Asymmetric Cyclopropanations with 3,3,3-Trifluoro-2-diazopropionate Catalyzed by a Heterochiral-at-The-Metal Centers Dirhodium Paddlewheel Complex
No full textAsymmetric cyclopropanation reactions of 3,3,3-trifluoro-2-diazopropionate have so far been largely beyond the scope of dirhodium catalysts. This significant gap in coverage is now closed with the aid of a new class of paddlewheel complex with “backbone chirality”, in which an array of only three different achiral ligands (acetamidate, trifluoroacetate, calix[4]arene dicarboxylate) renders the two rhodium centers inequivalent and chiral-at-the-metal each. The –NH group of the acetamidate engages the ester carbonyl of the metal carbene intermediate into favorable interligand hydrogen bonding, which in turn controls the trajectory of the incoming olefinic reaction partner. In addition, a dispersive interaction between the −CF3 group flanking the carbene center and a strategically placed bromine substituent on the calixarene dicarboxylate locks the conformation of the reactive intermediate in place within the chiral binding site, which translates into high diastereoselectivity and optical purity alike. The same type of interhalogen London dispersion interaction can also benefit [2 + 1] cycloadditions of other fluorinated carbene donors
Dialectical materialism and quantum physics: the unpublished 1957 lectures of David Bohm in Israel
No full textThis is the story of David Bohm's hitherto unpublished notes, uncovered from a series of lectures given in Israel in 1957 to a group of Marxist physicists from the Hashomer Hatsair (young guard) movement. The notes explore quantum theory and dialectical materialism, as well as shedding light on the intellectual and emotional resources of his persistent rebellion against orthodoxies in science.The discussion places his lectures notes in a wider historical, scientific, and philosophical context and traces Bohm's intellectual development from an early attempt to better understand the Copenhagen interpretation of quantum mechanics to his elaboration of an alternative causal interpretation based on the notion of "hidden variables."As the lecture notes strikingly illustrate, dialectical materialism played a fundamental role for the further development of his understanding of quantum mechanics. Bohm placed the notions of infinity of nature and the unity of opposites in the center of his natural philosophy, drawing from the works of Hegel, Marx, Engels, and Lenin. The authors also examine Bohm's legacy in the history of quantum mechanics and his contribution to preparing the "second quantum revolution." Bohm's engagement with dialectical materialism and his role as a dissident to the orthodox interpretation of quantum mechanics were pivotal in bringing about the novel insights and technologies associated with this second quantum revolution. During the 1960s, Bohm developed a growing interest in the nature of consciousness and engaged with the philosopher Jiddu Krishnamurti. In spite of a seemingly fundamental break with earlier philosophical positions, this new phase in Bohm's intellectual odyssey was not completely unrelated to his fascination with and deep understanding of Hegel's philosophy, which the lecture notes amply document for the first time.Introduction 1:Setting the stage 2:Commentaries on Bohm's lectures: A framework of dialectical thinking 3:Lecture Notes (LN) 4:Bohm's legac
Exploring innovative G-CSF schedules in AML cytarabine-based consolidation through a digital twin study of white blood cell recovery
No full textAsymmetric Carbonium Ion Catalysis: The Intramolecular Hydroalkoxylation of Cyclopropanes
No full textCyclopropanes serve as valuable synthetic intermediates in drug discovery and natural product synthesis. However, the stereoselective functionalization of cyclopropanes remains a fundamental challenge, traditionally necessitating the prior activation of the parent hydrocarbon. Here, we report an organocatalytic asymmetric intramolecular hydroalkoxylation of cyclopropanes that overcomes this constraint using chiral imidodiphosphorimidate catalysts. Our strategy directly affords enantioenriched substituted tetrahydrofurans with high enantioselectivity (up to 96.5:3.5 er). Kinetic analyses reveal a zero-order dependence on the substrate and support catalyst saturation. Combined experimental and computational studies suggest that the prereaction catalyst–substrate ion pair is stabilized through noncovalent interactions leading to the formation of a transient cycloproponium ion-like transition state. This work provides a potentially general platform for stereoselective cyclopropane functionalization
Signs and Signification in a Global Comparative Perspective: Premodern and Early Modern Sources in Original and Translation
No full textFoxi1 regulates multipotent mucociliary progenitors and ionocyte specification through transcriptional and epigenetic mechanisms
No full textFoxi1 is a master regulator of ionocytes (ISCs/INCs) across species and organs. Two subtypes of ISCs exist, and both α- and β-ISCs regulate pH- and ion-homeostasis in epithelia. Gain and loss of FOXI1 function are associated with human diseases, including Pendred syndrome, male infertility, renal acidosis, and cancers. Foxi1 was predominantly studied in the context of ISC specification, however, reports indicate additional functions in early and ectodermal development. Here, we re-investigated the functions of Foxi1 in Xenopus laevis embryonic mucociliary epidermis developpment and found a novel function for Foxi1 in the generation of Notch-ligand expressing mucociliary multipotent progenitors (MPPs). We demonstrate that MPPs are a distinct sub-population of epidermal cells in which Foxi1 has two concentration-dependent functions: At low levels, Foxi1 maintains ectodermal competence in MPPs through transcriptional and epigenetic mechanisms, while at high levels, Foxi1 induces a multi-step process of ISC specification and differentiation in cooperation with Ubp1 and Dmrt2. We further describe how foxi1 expression is affected through auto- and Notch-regulation, and how this developmental program affects mucociliary patterning. Together, we reveal novel functions for MPPs and Foxi1 in Xenopus mucociliary epidermis formation, relevant to our understanding of vertebrate development and human disease
Overlap-Kernel EPI: Estimating MRI Shot-to-Shot Phase Variations by Shifted-Kernel Extraction From Overlap Regions at Arbitrary k-Space Locations
No full textPurpose: In multi-shot EPI, shot-dependent phase fluctuations can introduce ghost artifacts, undermining advantages for enhancing resolution or reducing distortion, particularly in diffusion scans. Here, a novel self-navigation strategy based on shift-invariant kernel extraction is proposed, enabling robust estimation of phase inconsistencies from overlap bands at any k-space locations. It is inspired by RF sensitivity auto-calibration in parallel imaging, and extends traditional self-navigation trajectories beyond oversampled k-space center.Theory and Methods: Our shot-to-shot correction method only requires shot-to-shot sampling trajectories to slightly overlap at arbitrary k-space locations. Such k-space overlaps can be defined as shot-dependent auto-calibrating-signal regions, where a GRAPPA/ESPIRiT-type operation can be applied to explicitly extract shot-to-shot signal variation maps in one step. This inherits GRAPPA/ESPIRiT's robustness, and offers much greater flexibility in designing self-navigated multi-shot sequences.Results: Our kernel extraction techniques in four self-navigated 2D SE-EPI and GE-EPI sequences are successfully demonstrated, as well as minor applications in extracting maps from navigator data and B0 maps. Given sufficient SNR, self-navigation EPI can reach identical/better reconstruction quality compared to navigator corrections, applicable to various trajectories. Additionally, it is particularly suitable for the two-shot and four-shot mosaic EPI, where stronger shot-dependent eddy currents can also be removed, and the self-navigated ACS has higher SNR than the refocused navigator echoes.Conclusion: This paper rigorously analyzes subspace algorithms for phase-stabilized multi-shot MRI, significantly broadens the self-navigation concept, and provides a more complete picture of the connections between signal fluctuations calibration in EPI and RF sensitivity calibration in parallel imaging
