Apparatus for high resolution microwave spectroscopy in strong magnetic fields

We have developed a low temperature, high-resolution microwave surface impedance probe that is able to operate in high static magnetic fields. Surface impedance is measured by cavity perturbation of dielectric resonators, with sufficient sensitivity to resolve the microwave absorption of sub-mm-sized superconducting samples. The resonators are constructed from high permittivity single-crystal rutile (TiO2) and have quality factors in excess of 10^6. Resonators with such high performance have traditionally required the use of superconducting materials, making them incompatible with large magnetic fields and subject to problems associated with aging and power-dependent response. Rutile resonators avoid these problems while retaining comparable sensitivity to surface impedance. Our cylindrical rutile resonators have a hollow bore and are excited in TE_01(n-d) modes, providing homogeneous microwave fields at the center of the resonator where the sample is positioned. Using a sapphire hot-finger technique, measurements can be made at sample temperatures in the range 1.1 K to 200 K, while the probe itself remains immersed in a liquid helium bath at 4.2 K. The novel apparatus described in this article is an extremely robust and versatile system for microwave spectroscopy, integrating several important features into a single system. These include: operation at high magnetic fields; multiple measurement frequencies between 2.64 GHz and 14.0 GHz in a single resonator; excellent frequency stability, with typical drifts < 1 Hz per hour; the ability to withdraw the sample from the resonator for background calibration; and a small pot of liquid helium separate from the external bath that provides a sample base temperature of 1.1 K.Comment: 10 pages, 5 figure

Standard cell optimization and physical design in advanced technology nodes

Integrated circuits (ICs) are at the heart of modern electronics, which rely heavily on the state-of-the-art semiconductor manufacturing technology. The key to pushing forward semiconductor technology is IC feature-size miniaturization. However, this brings ever-increasing design complexities and manufacturing challenges to the $340 billion semiconductor industry. The manufacturing of two-dimensional layout on high-density metal layers depends on complex design-for-manufacturing techniques and sophisticated empirical optimizations, which introduces huge amounts of turnaround time and yield loss in advanced technology nodes. Our study reveals that unidirectional layout design can significantly reduce the manufacturing complexities and improve the yield, which is becoming increasingly adopted in semiconductor industry [61, 89]. The lithography printing of unidirectional layout can be tightly controlled using advanced patterning techniques, such as self-aligned double and quadruple patterning. Despite the manufacturing benefits, unidirectional layout leads to more restrictive solution space and brings significant impacts on the IC design automation ow for routing closure. Notably, unidirectional routing limits the standard cell pin accessibility, which further exacerbates the resource competitions during routing. Moreover, for post-routing optimization, traditional redundant-via insertion has become obsolete under unidirectional routing style, which makes the yield enhancement task extremely challenging. Regardless of complex multiple patterning and design-for-manufacturing approaches, mask optimization through resolution enhancement techniques remains as the key strategy to improve the yield of the semiconductor manufacturing processes. Among them, Sub-Resolution Assist Feature (SRAF) generation is a very important method to improve lithographic process windows. Model-based SRAF generation has been widely used to achieve high accuracy but it is time-consuming and hard to obtain consistent SRAFs. This dissertation proposes novel CAD algorithms and methodologies for standard cell optimization and physical design in advanced technology nodes, which ultimately reduces the design cycle and manufacturing cost of IC design. First, a standard cell pin access optimization engine is proposed to evaluate the pin accessibility of a given standard cell library. We further propose novel pin access planning techniques and concurrent pin access optimizations to efficiently resolve the routing resource competitions, which generates much better routing solutions than state-of-the-art, manufacturing-friendly routers. To systematically improve the manufacturing yield in the post-routing stage, a global optimization engine has been introduced for redundant local-loop insertion considering advanced manufacturing constraints. Finally, we propose the first machine learning-based framework for fast yet consistent SRAF generation with the high quality of results.Electrical and Computer Engineerin

Intragranular Nanocomposite Powders As Building Blocks For Ceramic Nanocomposites

A powder-based bottom-up processing scheme is introduced for the production of ceramic nanocomposites. Internal displacement reactions between solid solution powders and metallic reactants proceeding via gaseous intermediates are utilized to generate nanostructured building blocks for the synthesis of ceramic nanocomposites. Subsequent rapid sintering results in ceramic nanocomposites, whose microstructures are inherited from the building blocks. This processing scheme is demonstrated for the production of titanium carbide nanocomposites featuring up to 28 wt.% intragranular tungsten inclusions derived from titanium-tungsten mixed carbide powders. Heat treatment of mixed carbide powders in evacuated ampoules containing titanium sponge and iodine at 1000°C for 24 h resulted in nanocomposite powders featuring tungsten precipitates within titanium carbide grains that were subsequently consolidated via spark plasma sintering at 1300°C for 10 min to produce titanium carbide/metallic tungsten nanocomposites. Transformation of mixed titanium–tungsten carbide powders to titanium carbide/metallic tungsten nanocomposite powders was analyzed via X-ray diffraction. Electron microscopy observations of microstructures pre- and post- sintering showed that the intragranular character of nanocomposite powders can be retained in sintered ceramic nanocomposites. The building block approach demonstrated in this work represents an improved method to make ceramic nanocomposites with majority intragranular character

Solar-driven broad spectrum fungicides based on monodispersed Cu₇S₄ nanorods with strong near-infrared photothermal efficiency

The development of low-cost and biocompatible inorganic photothermal nanoagents with broadband sunlight absorption and high photothermal conversion efficiency as broad spectrum fungicides is highly desirable for the large scale antibacterial treatment especially in the wild, because of their highly efficient anti-bacteria ability via solar irradiation. Here, we present a facile strategy for the synthesis of Cu7S4 nanorods (NRs) with broadband light absorption (300-3300 nm) and high photothermal conversion efficiency (57.8%, 808 nm), and the use of these NRs as broad spectrum fungicides for efficient disinfection using natural sunlight as light source. In the presence of Cu7S4 NRs, with natural sunlight irradiation (70 mW cm-2), both Gram-positive (S. aureus) and Gram-negative (E. coli) bacterium strains (2 mL, 106 mL-1) were completely killed in 10 min. These results suggest that our Cu7S4 NRs are effective and broad spectrum photothermal anti-bacterial agents regardless of drug resistance, that are particularly suitable for anti-bacteria activity in the wild using solar irradiation where artificial light sources are not available. Due to their strong near infrared (NIR) absorption, these biocompatible and low-cost Cu7S4 NRs may also serve as promising agents for photothermal therapy of tumors, disinfection in clinics, food sterilization and environmental treatment.</p

Femtosecond photonic viral inactivation probed using solid-state nanopores

We report on detection of virus inactivation using femtosecond laser radiation by measuring the conductance of a solid state nanopore designed for detecting single particles. Conventional methods of assaying for viral inactivation based on plaque forming assays require 24–48 h for bacterial growth. Nanopore conductance measurements provide information on morphological changes at a single virion level.We show that analysis of a time series of nanopore conductance can quantify the detection of inactivation, requiring only a few minutes from collection to analysis. Morphological changes were verified by dynamic light scattering. Statistical analysis maximizing the information entropy provides a measure of the log reduction value. This work provides a rapid method for assaying viral inactivation with femtosecond lasers using solid-state nanopores.First author draf

Formation and evolution of epitaxial Co5Ge7Co5Ge7 film on Ge (001) surface by solid-state reaction in an in situ ultrahigh-vacuum transmission electron microscope

A thin metallic cobalt (Co) layer was deposited on a single-crystal Ge (001) surface at room temperature by the electron-beam evaporation of a pure Co metal source in an ultrahigh-vacuum transmission electron microscope. The formation and epitaxial growth of a cobalt germanide Co5Ge7Co5Ge7 phase on the Ge (001) surface was studied in situ by gradually heating the sample from room temperature to ∼ 350 °C∼350°C. The occurrence of an epitaxial hexagonal-close-packed Co and the reaction between Co and Ge were observed at ∼ 225 °C∼225°C. After annealing at ∼ 300 °C∼300°C for 26.5 h, a continuous epitaxial Co5Ge7Co5Ge7 film formed on the Ge (001) substrate. With further annealing at a higher temperature, the continuous Co5Ge7Co5Ge7 layer broke up and formed three-dimensional islands in order to relieve the strain energy in the epitaxial Co5Ge7Co5Ge7 layer. Two epitaxial relationships between Co5Ge7Co5Ge7 and Ge, i.e., Co5Ge7〈110〉(001)//Ge〈100〉(001)Co5Ge7〈110〉(001)∕∕Ge〈100〉(001) and Co5Ge7〈001〉(110)//Ge〈100〉(001)Co5Ge7〈001〉(110)∕∕Ge〈100〉(001) were found by electron diffraction.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/87837/2/211909_1.pd

Impact of amoxicillin-clavulanate followed by autologous fecal microbiota transplantation on fecal microbiome structure and metabolic potential

The spread of multidrug resistance among pathogenic organisms threatens the efficacy of antimicrobial treatment options. The human gut serves as a reservoir for many drug-resistant organisms and their resistance genes, and perturbation of the gut microbiome by antimicrobial exposure can open metabolic niches to resistant pathogens. Once established in the gut, antimicrobial-resistant bacteria can persist even after antimicrobial exposure ceases. Strategies to prevent multidrug-resistant organism (MDRO) infections are scarce, but autologous fecal microbiota transplantation (autoFMT) may limit gastrointestinal MDRO expansion. AutoFMT involves banking one’s feces during a healthy state for later use in restoring gut microbiota following perturbation. This pilot study evaluated the effect of amoxicillin-clavulanic acid (Amox-Clav) exposure and autoFMT on gastrointestinal microbiome taxonomic composition, resistance gene content, and metabolic capacity. Importantly, we found that metabolic capacity was perturbed even in cases where gross phylogeny remained unchanged and that autoFMT was safe and well tolerated.Strategies to prevent multidrug-resistant organism (MDRO) infections are scarce, but autologous fecal microbiota transplantation (autoFMT) may limit gastrointestinal MDRO expansion. AutoFMT involves banking one’s feces during a healthy state for later use in restoring gut microbiota following perturbation. This pilot study evaluated the effect of autoFMT on gastrointestinal microbiome taxonomic composition, resistance gene content, and metabolic capacity after exposure to amoxicillin-clavulanic acid (Amox-Clav). Ten healthy participants were enrolled. All received 5 days of Amox-Clav. Half were randomized to autoFMT, derived from stool collected pre-antimicrobial exposure, by enema, and half to saline enema. Participants submitted stool samples pre- and post-Amox-Clav and enema and during a 90-day follow-up period. Shotgun metagenomic sequencing revealed taxonomic composition, resistance gene content, and metabolic capacity. Amox-Clav significantly altered gut taxonomic composition in all participants (n = 10, P  0.05, compared to enrollment). Alterations to microbial metabolic capacity occurred following antimicrobial exposure even in participants without substantial taxonomic disruption, potentially creating open niches for pathogen colonization. Our findings suggest that metabolic potential is an important consideration for complete assessment of antimicrobial impact on the microbiome. AutoFMT was well tolerated and may have contributed to phylogenetic recovery. (This study has been registered at ClinicalTrials.gov under identifier NCT02046525.