Jin Wang

Argonne National Laboratory, Lemont, Illinois, United States

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Publications (141)531.31 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: Unveiling the near-field dynamics of high-speed and optically dense liquid fuel jets and sprays, such as velocity and turbulence intensity fields, is of great importance for successful interpretation and modeling of the spraying and combustion process in internal combustion engines. Characterizing the dynamics using conventional laser optical techniques have been difficult in the near-nozzle region where the fuel jet, ligaments, and droplets interact with visible light strongly producing severe multiple scattering and optical opacity. Here, we use a novel technique to characterize the velocity and turbulence intensity fields of the high-speed diesel sprays in the near-field by multi-exposed X-ray phase-contrast images. With the X-ray-imaging data, the effects of the orifice inlet geometry and injection pressure on the near-field dynamics of the diesel sprays are investigated. Notable features of the spray dynamics in the near-nozzle region and beyond are discussed by comparing the measurement results with the predictions of conventional gas jet theories.
    Fuel 10/2014; 133:299–309. · 3.36 Impact Factor
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    ABSTRACT: Polymers that are thermally insulating in bulk forms have been found to exhibit higher thermal conductivities when stretched under tension. This enhanced heat transport performance is believed to arise from the orientational alignment of the polymer chains induced by tensile stretching. In this work, a novel high-sensitivity micro-device platform was employed to determine the axial thermal conductivity of individual Nylon-11 polymer nanofibers fabricated by electrospinning and post-stretching. Their thermal conductivity showed a correlation with the crystalline morphology measured by high-resolution wide-angle X-ray scattering. The relationship between the nanofiber internal structures and thermal conductivities could provide insights into the understanding of phonon transport mechanisms in polymeric systems and also guide future development of the fabrication and control of polymer nanofibers with extraordinary thermal performance and other desired properties.
    Nanoscale 06/2014; 6(14):8283-8291. · 6.73 Impact Factor
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    ABSTRACT: Vaccination has been the most widely used strategy to protect against viral infections for centuries. However, the molecular mechanisms governing the long-term persistence of immunological memory in response to vaccines remain unclear. Here we show that autophagy has a critical role in the maintenance of memory B cells that protect against influenza virus infection. Memory B cells displayed elevated levels of basal autophagy with increased expression of genes that regulate autophagy initiation or autophagosome maturation. Mice with B cell-specific deletion of Atg7 (B/Atg7(-/-) mice) showed normal primary antibody responses after immunization against influenza but failed to generate protective secondary antibody responses when challenged with influenza viruses, resulting in high viral loads, widespread lung destruction and increased fatality. Our results suggest that autophagy is essential for the survival of virus-specific memory B cells in mice and the maintenance of protective antibody responses required to combat infections.
    Nature medicine 04/2014; · 27.14 Impact Factor
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    ABSTRACT: Cavitation is an intricate multiphase phenomenon that interplays with turbulence in fluid flows. It exhibits clear duality in characteristics, being both destructive and beneficial in our daily lives and industrial processes. Despite the multitude of occurrences of this phenomenon, highly dynamic and multiphase cavitating flows have not been fundamentally well understood in guiding the effort to harness the transient and localized power generated by this process. In a microscale, multiphase flow liquid injection system, we synergistically combined experiments using time-resolved x-radiography and a novel simulation method to reveal the relationship between the injector geometry and the in-nozzle cavitation quantitatively. We demonstrate that a slight alteration of the geometry on the micrometer scale can induce distinct laminar-like or cavitating flows, validating the multiphase computational fluid dynamics simulation. Furthermore, the simulation identifies a critical geometric parameter with which the high-speed flow undergoes an intriguing transition from non-cavitating to cavitating.
    Scientific Reports 06/2013; 3:2067. · 5.08 Impact Factor
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    ABSTRACT: Improvement of spray atomization and penetration characteristics of the gasoline direct-injection (GDi) multihole injector is a critical component of the GDi combustion developments, especially in the context of engine downsizing and turbo-charging trend that is adopted in order to achieve the European target CO2, US CAFE, and concomitant stringent emissions standards. Significant R&D efforts are directed towards optimization of the nozzle designs, in order to improve the GDi multi-hole spray characteristics. This publication reports VOF-LES analyses of GDi singlehole skew-angled nozzles, with β=30° skew (bend) angle and different nozzle geometries. The objective is to extend previous works to include the effect of nozzle-hole skew angle on the nozzle flow and spray primary breakup. VOFLES simulations of a single nozzle-hole of a purposedesigned GDi multi-hole seat geometry, with three identical nozzle-holes per 120° seat segment, are performed. The simulations are complemented by comparison with the spray near-field breakup structure obtained through optical shadowgraphy and phase-contrast x-ray imaging techniques. The spray shadographic and X-ray imaging data reveal the jet primary breakup in the immediate vicinity of the nozzle, representative of the “atomization regime”. The jet morphology indicate the effect of injector valve-group hydraulic pressure oscillations. The VOFLES simulations show fully-attached nozzle flow, and an “atomization regime” spray primary breakup in close agreement with the spray imaging data. The simulations highlight the effect of nozzle counter-bore on the jet primary atomization, through influence on the jet interface instability and, more notable, the physical interaction with the atomizing spray plume. Overall, the comparison of VOF-LES simulations with the spray imaging data shows good predictive capability with respect to the jet primary breakup, the plume macroscale features (trajectory, cone angle) and the observed effect of nozzle geometry.
    SAE 2013 World Congress and Exhibition; 04/2013
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    ABSTRACT: The pathway of interfacial self-assembly of large-scale, highly-ordered 2D nanoparticle/polymer monolayer or bilayer arrays from a toluene solution at an air/water interface was investigated using grazing-incidence small-angle scattering at a synchrotron source. Interfacial-assembly of the ordered nanoparticle/polymer array was found to occur through two stages: formation of an incipient randomly close-packed interfacial monolayer followed by compression of the monolayer to form a close-packed lattice driven by solvent evaporation from the polymer. Because the nanoparticles are hydrophobic, they localize exclusively to the polymer-air interface during self-assembly, creating a through thickness asymmetric film as confirmed by x-ray reflectivity. The interfacial self-assembly approach can be extended to form binary NP/polymer arrays. It is anticipated that by understanding the interfacial self-assembly pathway, this simple evaporative procedure could be conducted as a continuous process amenable to large area nanoparticle-based manufacturing needed for emerging energy technologies.
    Nano Letters 01/2013; · 13.03 Impact Factor
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    ABSTRACT: Engagement of the TCR induces activation-induced cell death (AICD) of T cells that have been previously stimulated. However, a portion of these T cells can survive and undergo further activation. The molecular mechanism that decides whether a T cell will live or die after TCR re-engagement is unclear. We found that cross-linking of TCR in preactivated primary mouse T cells led to the cleavage of anti-apoptotic Bcl-2 and Bcl-xL in dying cells. Cleavage-resistant Bcl-2 and Bcl-xL were more efficient than their wild-type counterparts in the inhibition of apoptosis in primary mouse T cells and in the H9 T cell line after TCR cross-linking. In contrast, the surviving T cells after TCR re-engagement displayed upregulation of Bcl-xL, and knockdown of Bcl-xL promoted AICD. This indicates that caspase-mediated cleavage of anti-apoptotic Bcl-2 or Bcl-xL facilitates AICD in T cells, whereas upregulation of Bcl-xL promotes T cell survival and allows further T cell activation. Our data suggest that cleavage of anti-apoptotic Bcl-2 and Bcl-xL contributes to the decision between T cell activation and apoptosis after TCR re-engagement.
    The Journal of Immunology 11/2012; · 5.52 Impact Factor
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    ABSTRACT: We demonstrate the use of electrostatically driven micro-electromechanical systems (MEMS) devices to control and deliver synchrotron x-ray pulses at high repetition rates. Torsional MEMS micromirrors, rotating at duty cycles of 2 kHz and higher, were used to modulate grazing-incidence x rays, producing x-ray bunches shorter than 10 μs. We find that dynamic deformation of the oscillating micromirror is a limiting factor in the duration of the x-ray pulses produced, and we describe plans for reaching higher operating frequencies using mirrors designed for minimal deformation.
    Proc SPIE 10/2012;
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    ABSTRACT: Lensless X-ray coherent diffraction imaging (CDI) has emerged as a thriving field promising applications in materials and biological sciences with a theoretical imaging resolution only limited by the X-ray wavelength. Most CDI methods use transmission geometry, which is not suitable for nanostructures grown on opaque substrates or for objects of interest comprising only surfaces or interfaces. Attempts have been made to perform CDI experiments in reflection geometry, both optically and with X-rays, but the reconstruction resulted in mostly planar images, with less success in the third dimension. Here, we discuss the development of coherent surface scattering imaging in grazing-incidence geometry that takes advantage of enhanced X-ray surface scattering and interference near total external reflection. We demonstrate the successful reconstruction of substrate-supported non-periodic surface patterns in three dimensions with nanometre resolution in the direction normal to the substrate, promising wide applications in elucidating structures in substrate-supported and buried nanoelectronics and photonics.
    Nature Photonics 09/2012; 6(9):588-592. · 27.25 Impact Factor
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    ABSTRACT: Mitochondrial disruption during apoptosis results in the activation of caspase-9 and a downstream caspase cascade. Triggering this caspase cascade leads to the cleavage of anti-apoptotic Bcl-2 family proteins, resulting in feedback amplification of mitochondrial disruption. However, whether such a feedback loop plays an important role in the promotion of caspase activation and execution of apoptosis has not been well established. We observed that mutated Bcl-2 or Bcl-xL that are resistant to cleavage by caspases inhibited caspase-9-induced caspase activation in human H9 T cells. The release of Smac after the activation of caspase-9 was also inhibited by cleavage-resistant Bcl-2 or Bcl-xL. Consistently, caspase-9-deficient cells were defective in the release of Smac after induction of apoptosis. Moreover, addition of a Smac mimetic overcame the inhibitory effects of cleavage-resistant Bcl-2/Bcl-xL, and restored caspase-9-mediated cell death. Our data suggest that caspase-9-induced feedback disruption of mitochondria plays an important role in promoting the activation of caspases, while a defect in this process can be overcome by promoting Smac functions.
    Journal of clinical & cellular immunology. 08/2012; 3(3).
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    ABSTRACT: In recent years, X-ray radiography has been used to probe the internal structure of dense sprays with microsecond time resolution and a spatial resolution of 15 µm even in high-pressure environments. Recently, the 7BM beamline at the Advanced Photon Source (APS) has been commissioned to focus on the needs of X-ray spray radiography measurements. The spatial resolution and X-ray intensity at this beamline represent a significant improvement over previous time-resolved X-ray radiography measurements at the APS.
    Journal of Synchrotron Radiation 07/2012; 19(Pt 4):654-7. · 2.19 Impact Factor
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    ABSTRACT: As an increasingly important structural-characterization technique, grazing-incidence X-ray scattering (GIXS) has found wide applications for in situ and real-time studies of nanostructures and nanocomposites at surfaces and interfaces. A dedicated beamline has been designed, constructed and optimized at beamline 8-ID-E at the Advanced Photon Source for high-resolution and coherent GIXS experiments. The effectiveness and applicability of the beamline and the scattering techniques have been demonstrated by a host of experiments including reflectivity, grazing-incidence static and kinetic scattering, and coherent surface X-ray photon correlation spectroscopy. The applicable systems that can be studied at 8-ID-E include liquid surfaces and nanostructured thin films.
    Journal of Synchrotron Radiation 07/2012; 19(Pt 4):627-36. · 2.19 Impact Factor
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    ABSTRACT: The development of the 3^rd and 4^th generation synchrotrons has stimulated extensive research activities in x-ray imaging techniques. Among all, coherent diffractive imaging (CDI) shows great promise, as its resolution is only limited by the wavelength of the source. Most of the CDI work reported thus far used transmission geometry, which however is not suitable for samples on opaque substrates or in which only the surfaces are the regions of interest. Even though two groups have performed CDI experiments (using laser or x-ray) in reflection geometry and succeeded in reconstructing the planar image of the surface, the theoretical underpinnings and analysis approaches of their techniques are essentially identical to transmission CDI. Most importantly, they couldn't obtain the structural information along sample thickness direction. Here, we introduce a reflection CDI technique that works at grazing-incidence geometry. By visualizing Au nanostructures fabricated on Si substrate, we demonstrate that this innovative imaging technique is capable of obtaining both 2D and 3D information of surfaces or buried structures in the samples. In the meanwhile, we will also explain the grazing-incidence-scattering based-algorithm developed for 3D phase retrieval.
    02/2012;
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    Min Chen, Kumar Felix, Jin Wang
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    ABSTRACT: After stimulation of antigen-specific T cells, dendritic cell (DCs) are susceptible to killing by these activated T cells that involve perforin and Fas-dependent mechanisms. Fas-dependent DC apoptosis has been shown to limit DC accumulation and prevent the development of autoimmunity. However, a role for perforin in the maintenance of DC homeostasis for immune regulation remains to be determined. Here we show that perforin deficiency in mice, together with the deletion of Fas in DCs (perforin(-/-)DC-Fas(-/-)), led to DC accumulation, uncontrolled T-cell activation, and IFN-γ production by CD8+ T cells, resulting in the development of lethal hemophagocytic lymphohistiocytosis. Consistently, adoptive transfer of Fas(-/-) DCs induced over-activation and IFN-γ production in perforin(-/-) CD8+ T cells. Neutralization of IFN-γ prevented the spreading of inflammatory responses to different cell types and protected the survival of perforin(-/-)DC-Fas(-/-) mice. Our data suggest that perforin and Fas synergize in the maintenance of DC homeostasis to limit T cell activation, and prevent the initiation of an inflammatory cascade.
    Blood 01/2012; 119(1):127-36. · 9.78 Impact Factor
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    ABSTRACT: We describe a MEMS micromirror for modulation of X-ray pulses needed for critical time-resolved process studies of cyclical and far-from-equilibrium phenomena. This MEMS micromirror leverages grazing-angle reflection of X-ray pulses to generate its temporal modulation response. The generated responses are 1.5μs wide for 8keV X-rays and have been successfully used to isolate single X-ray pulses separated 1.59μs from their suppressed neighboring pulses.
    Optical MEMS and Nanophotonics (OMN), 2012 International Conference on; 01/2012
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    Min Chen, Jin Wang
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    ABSTRACT: In response to antigen stimulations, cells in the immune system undergo dynamic activation, differentiation, expansion and turnover. Programmed cell death is important for maintaining homeostasis of different cell types in the immune system. Dendritic cells (DCs) are a heterogeneous population of antigen presenting cells that capture, process and present antigens to stimulate lymphocytes. DCs have also emerged as major regulators of both innate and adaptive immune responses. Conventional myeloid DCs are relatively short-lived compared to lymphocytes in lymphoid organs. Mitochondrion-dependent apoptosis governed by Bcl-2 family members plays a major role in regulating spontaneous DC turnover. Killing of DCs by antigen-specific T cells also provides a negative feedback mechanism to restrict the duration and the scope of immune responses. Defects in cell death in DCs lead to DC accumulation, resulting in overactivation of lymphocytes and the development of autoimmunity in mice. Programmed cell death in DCs may play essential roles in the regulation of the duration and magnitude of immune responses, and in the protection against autoimmunity and uncontrolled inflammation.
    Journal of clinical & cellular immunology. 12/2011; S3.
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    Min Chen, Kumar Felix, Jin Wang
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    ABSTRACT: Dendritic cells (DCs) harbor an active mitochondrion-dependent cell death pathway regulated by Bcl-2 family members and undergo rapid turnover in vivo. However, the functions for mitochondrion-dependent cell death of DCs in immune regulation remain to be elucidated. In this article, we show that DC-specific knockout of proapoptotic Bcl-2 family members, Bax and Bak, induced spontaneous T cell activation and autoimmunity in mice. In addition to a defect in spontaneous cell death, Bax(-/-)Bak(-/-) DCs were resistant to killing by CD4(+)Foxp3(+) T regulatory cells (Tregs) compared with wild-type DCs. Tregs inhibited the activation of T effector cells by wild-type, but not Bax(-/-)Bak(-/-), DCs. Bax(-/-)Bak(-/-) DCs showed increased propensity for inducing autoantibodies. Moreover, the autoimmune potential of Bax(-/-)Bak(-/-) DCs was resistant to suppression by Tregs. Our data suggested that Bax and Bak mediate intrinsic spontaneous cell death in DCs, as well as regulate DC killing triggered by Tregs. Bax- and Bak-dependent cell death mechanisms help to maintain DC homeostasis and contribute to the regulation of T cell activation and the suppression of autoimmunity.
    The Journal of Immunology 12/2011; 187(11):5684-92. · 5.52 Impact Factor
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    ABSTRACT: A symmetric diblock copolymer, poly(pentafluorostyrene-b-styrene) (PPFS-b-PS), is synthesized by atom transfer radical polymerization (ATRP). The behavior of PPFS-b-PS thin films on silicon wafers is investigated. Lamellar microdomains oriented parallel to the film surface are formed when the thin films are heated to 220 °C for 24 h, due to preferential interfacial interactions and the low surface energy of the PPFS. An electric field is used to overcome the low surface energy of the fluorinated block and preferential interactions with the substrate so as to force the lamellar microdomains to orient normal to the surface.
    Macromolecular Chemistry and Physics 11/2011; 212(22). · 2.39 Impact Factor
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    ABSTRACT: Multi-hole DI injectors are being adopted in the advanced downsized DISI ICE powertrain in the automotive industry worldwide because of their robustness and cost-performance. Although their injector design and spray resembles those of DI diesel injectors, there are many basic but distinct differences due to different injection pressure and fuel properties, the sac design, lower L/D aspect ratios in the nozzle hole, closer spray-to-spray angle and hense interactions. This paper used Phase-Contrast X ray techniques to visualize the spray near a 3-hole DI gasoline research model injector exit and compared to the visible light visualization and the internal flow predictions using with multi-dimensional multi-phase CFD simulations. The results show that strong interactions of the vortex strings, cavitation, and turbulence in and near the nozzles make the multi-phase turbulent flow very complicated and dominate the near nozzle breakup mechanisms quite unlike those of diesel injections.
    SAE Technical Paper Series. 08/2011; 2011-01-1881.
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    ABSTRACT: We monitor the structural evolution of a poly(tert-butyl methacrylate)-poly(methyl methacrylate) (PtBMA–PMMA) diblock copolymer thin film undergoing conversion via reactive annealing to yield poly(methacrylic acid)–poly(methyl methacrylate) (PMAA–PMMA). Using grazing-incidence small-angle X-ray scattering (GISAXS) and atomic force microscopy (AFM), we confirm the generation of well-ordered cylindrical microdomains in the PtBMA–PMMA precursor film after solvent annealing. After initiating thermal deprotection, the high degree of ordering can be maintained up to 25% conversion of the diblock into PMAA–PMMA. Beyond this point, a significant decrease in the overall film thickness associated with the conversion process cannot accommodate the hexagonal lattice adopted by the cylindrical microdomains. At the same time, rearrangement of PMMA cores in a PtBMA matrix that is becoming progressively glassier presents further difficulties in maintaining a reasonable structure. The fully converted PMAA–PMMA film contains a system of cylindrical microdomains that lack good ordering.
    Macromolecules. 07/2011; 44(16).

Publication Stats

1k Citations
531.31 Total Impact Points

Institutions

  • 1998–2014
    • Argonne National Laboratory
      • • Division of X-ray Science
      • • Center for Transportation Research
      • • Center for Nanoscale Materials
      Lemont, Illinois, United States
  • 2006–2012
    • Baylor College of Medicine
      • Department of Pathology & Immunology
      Houston, TX, United States
  • 2008–2011
    • University of New Mexico
      • Department of Chemical and Nuclear Engineering
      Albuquerque, NM, United States
  • 2004–2011
    • Northwestern University
      • Department of Materials Science and Engineering
      Evanston, IL, United States
  • 2010
    • DePaul University
      Chicago, Illinois, United States
  • 2005
    • University of Massachusetts Amherst
      • Department of Polymer Science and Engineering
      Amherst Center, MA, United States
  • 2003–2005
    • Cornell University
      • Department of Physics
      Ithaca, NY, United States