Now showing items 4847-4866 of 5032

    • U-duct turbulent-flow computation with the ST-VMS method and isogeometric discretization 

      Aydinbakar, Levent; Takizawa, Kenji; Tezduyar, Tayfun E.; Matsuda, Daisaku (2021)
      The U-duct turbulent flow is a known benchmark problem with the computational challenges of high Reynolds number, high curvature and strong flow dependence on the inflow profile. We use this benchmark problem to test and evaluate the Space–Time Variational Multiscale (ST-VMS) method with ST isogeometric discretization. A fully-developed flow field ...
    • UBER v1.0: a universal kinetic equation solver for radiation belts 

      Zheng, Liheng; Chen, Lunjin; Chan, Anthony A.; Wang, Peng; Xia, Zhiyang; (2021)
      Recent proceedings in radiation belt studies have proposed new requirements for numerical methods to solve the kinetic equations involved. In this article, we present a numerical solver that can solve the general form of the radiation belt Fokker–Planck equation and Boltzmann equation in arbitrarily provided coordinate systems and with user-specified ...
    • Ultra-high sensitive acetylene detection using quartz-enhanced photoacoustic spectroscopy with a fiber amplified diode laser and a 30.72 kHz quartz tuning fork 

      Ma, Yufei; He, Ying; Zhang, Ligong; Yu, Xin; Zhang, Jingbo; (2017)
      An ultra-high sensitive acetylene (C2H2) Quartz-enhanced photoacoustic spectroscopy (QEPAS) sensor based on a high power laser and a quartz tuning fork with a resonance frequency f0 of 30.72 kHz was demonstrated. An erbium-doped fiber amplifier (EDFA) amplified distributed feedback diode laser with a center wavelength of 1.53 μm was used as the ...
    • Ultra-High Surface Area Activated Porous Asphalt for CO2 Capture through Competitive Adsorption at High Pressures 

      Jalilov, Almaz S.; Li, Yilun; Tian, Jian; Tour, James M.; NanoCarbon Center (2017)
      This study reports an improved method for activating asphalt to produce ultra-high surface area porous carbons. Pretreatment of asphalt (untreated Gilsonite, uGil) at 400 °C for 3 h removes the more volatile organic compounds to form pretreated asphalt (uGil-P) material with a larger fraction of higher molecular weight π-conjugated asphaltenes. ...
    • Ultra-long-range Rydberg molecules in a divalent atomic system 

      DeSalvo, B.J.; Aman, J.A.; Dunning, F.B.; Killian, T.C.; Sadeghpour, H.R.; (2015)
      We report the creation of ultra-long-range Sr2 molecules comprising one ground-state 5s2 1S0 atom and one atom in a 5sns 3S1 Rydberg state for n ranging from 29 to 36. Molecules are created in a trapped ultracold atomic gas using two-photon excitation near resonant with the 5s5p 3P1 intermediate state, and their formation is detected through ground-state ...
    • Ultracold Nonreactive Molecules in an Optical Lattice: Connecting Chemistry to Many-Body Physics 

      Doçaj, Andris; Wall, Michael L.; Mukherjee, Rick; Hazzard, Kaden R.A.; Rice Center for Quantum Materials (2016)
      We derive effective lattice models for ultracold bosonic or fermionic nonreactive molecules (NRMs) in an optical lattice, analogous to the Hubbard model that describes ultracold atoms in a lattice. In stark contrast to the Hubbard model, which is commonly assumed to accurately describe NRMs, we find that the single on-site interaction parameter U is ...
    • Ultrafast formation of interlayer hot excitons in atomically thin MoS2/WS2ᅠheterostructures 

      Chen, Hailong; Wen, Xiewen; Zhang, Jing; Wu, Tianmin; Gong, Yongji; (2016)
      Van der Waals heterostructures composed of two-dimensional transition-metal dichalcogenides layers have recently emerged as a new family of materials, with great potential for atomically thin opto-electronic and photovoltaic applications. It is puzzling, however, that the photocurrent is yielded so efficiently in these structures, despite the apparent ...
    • Ultrafast laser surgery probe with a calcium fluoride miniaturized objective for bone ablation 

      Subramanian, Kaushik; Subramanian, Kaushik; Andrus, Liam; Andrus, Liam; Pawlowski, Michal; (2021)
      We present a miniaturized ultrafast laser surgery probe with improved miniaturized optics to deliver higher peak powers and enable higher surgical speeds than previously possible. A custom-built miniaturized CaF2 objective showed no evidence of the strong multiphoton absorption observed in our previous ZnS-based probe, enabling higher laser power ...
    • Ultrafast non-radiative dynamics of atomically thin MoSe2 

      Lin, Ming-Fu; Kochat, Vidya; Krishnamoorthy, Aravind; Bassman, Lindsay; Weninger, Clemens; (2017)
      Photo-induced non-radiative energy dissipation is a potential pathway to induce structural-phase transitions in two-dimensional materials. For advancing this field, a quantitative understanding of real-time atomic motion and lattice temperature is required. However, this understanding has been incomplete due to a lack of suitable experimental techniques. ...
    • Ultrafast Optical Microscopy of Single Monolayer Molybdenum Disulfide Flakes 

      (2016)
      We have performed ultrafast optical microscopy on single flakes of atomically thin CVD-grown molybdenum disulfide, using non-degenerate femtosecond pump-probe spectroscopy to excite and probe carriers above and below the indirect and direct band gaps. These measurements reveal the influence of layer thickness on carrier dynamics when probing near the ...
    • Ultrafast probes of electron–hole transitions between two atomic layers 

      Wen, Xiewen; Chen, Hailong; Wu, Tianmin; Yu, Zhihao; Yang, Qirong; (2018)
      Phase transitions of electron-hole pairs on semiconductor/conductor interfaces determine fundamental properties of optoelectronics. To investigate interfacial dynamical transitions of charged quasiparticles, however, remains a grand challenge. By employing ultrafast mid-infrared microspectroscopic probes to detect excitonic internal quantum transitions ...
    • Ultraflexible Neural Electrodes for Long-Lasting Intracortical Recording 

      He, Fei; Lycke, Roy; Ganji, Mehran; Xie, Chong; Luan, Lan; (2020)
      Implanted electrodes provide one of the most important neurotechniques for fundamental and translational neurosciences by permitting time-resolved electrical detection of individual neurons in vivo. However, conventional rigid electrodes typically cannot provide stable, long-lasting recordings. Numerous interwoven biotic and abiotic factors at the ...
    • Ultrahigh resistance of hexagonal boron nitride to mineral scale formation 

      Zuo, Kuichang; Zhang, Xiang; Huang, Xiaochuan; Oliveira, Eliezer F.; Guo, Hua; (2022)
      Formation of mineral scale on a material surface has profound impact on a wide range of natural processes as well as industrial applications. However, how specific material surface characteristics affect the mineral-surface interactions and subsequent mineral scale formation is not well understood. Here we report the superior resistance of hexagonal ...
    • Ultrahigh strength, modulus, and conductivity of graphitic fibers by macromolecular coalescence 

      Lee, Dongju; Kim, Seo Gyun; Hong, Seungki; Madrona, Cristina; Oh, Yuna; (2022)
      Theoretical considerations suggest that the strength of carbon nanotube (CNT) fibers be exceptional; however, their mechanical performance values are much lower than the theoretical values. To achieve macroscopic fibers with ultrahigh performance, we developed a method to form multidimensional nanostructures by coalescence of individual nanotubes. ...
    • Ultrahigh-throughput generation and characterization of cellular aggregates in laser-ablated microwells of poly(dimethylsiloxane) 

      Albritton, Jacob L.; Roybal, Jonathon D.; Paulsen, Samantha J.; Calafat, Nick; Flores-Zaher, Jose A.; (2016)
      Aggregates of cells, also known as multicellular aggregates (MCAs), have been used as microscale tissues in the fields of cancer biology, regenerative medicine, and developmental biology for many decades. However, small MCAs (fewer than 100 cells per aggregate) have remained challenging to manufacture in large quantities at high uniformity. Forced ...
    • Ultrasensitive Plasmonic Platform for Label-Free Detection of Membrane-Associated Species 

      Bruzas, Ian; Unser, Sarah; Yazdi, Sadegh; Ringe, Emilie; Sagle, Laura (2016)
      Lipid membranes and membrane proteins are important biosensing targets, motivating the development of label-free methods with improved sensitivity. Silica-coated metal nanoparticles allow these systems to be combined with supported lipid bilayers for sensing membrane proteins through localized surface plasmon resonance (LSPR). However, the small ...
    • Ultrasensitivity of the Bacillus subtilis sporulation decision 

      (2012)
      Starving Bacillus subtilis cells execute a gene expression program resulting in the formation of stress-resistant spores. Sporulation master regulator, Spo0A, is activated by a phosphorelay and controls the expression of a multitude of genes, including the forespore- specific sigma factor σF and the mother cell-specific sigma factor σE. Identification ...
    • Ultraspecific and Highly Sensitive Nucleic Acid Detection by Integrating a DNA Catalytic Network with a Label-Free Microcavity 

      (2014)
      Nucleic acid detection with label-free biosensors circumvents costly fluorophore functionalization steps associated with conventional assays by utilizing transducers of impressive ultimate detection limits. Despite this technological prowess, molecular recognition at a surface limits the biosensors' sensitivity, specificity, and reusability. It is ...
    • Ultrastrong magnon–magnon coupling dominated by antiresonant interactions 

      Makihara, Takuma; Hayashida, Kenji; Noe Ii, G. Timothy; Li, Xinwei; Marquez Peraca, Nicolas; (2021)
      Exotic quantum vacuum phenomena are predicted in cavity quantum electrodynamics systems with ultrastrong light-matter interactions. Their ground states are predicted to be vacuum squeezed states with suppressed quantum fluctuations owing to antiresonant terms in the Hamiltonian. However, such predictions have not been realized because antiresonant ...
    • Ultrathin AAO Membrane as a Generic Template for Sub-100 nm Nanostructure Fabrication 

      Robatjazi, Hossein; Bahauddin, Shah Mohammad; Macfarlan, Luke H.; Fu, Sidan; Thomann, Isabell; (2016)
      Anodic aluminum oxide (AAO) templates are emerging as a platform for simple, cost-effective, high-throughput top-down nanofabrication of regular arrays of nanostructures. Thus far, however, AAO pattern transfer has largely been restricted to smooth and chemically inert surfaces, mostly Silicon substrates. Here, we present a more generalizable strategy ...