Micromachined Millimetre-Wave Passive Components at 38 and 77 GHz

A precision micro-fabrication technique has been developed for millimetre-wave components of air-filled three-dimensional structures, such as rectangular coaxial lines or waveguides. The devices are formed by bonding several layers of micromachining defined slices with a thickness of a few hundred micrometres. The slices are thickphotoresist SU8 defined by photolithography, or silicon with a pattern defined by deep reactive ion etching; both are coated with gold by evaporation. The process is simple, and low-cost, as compared with conventional precision metal machining, but yields mm-wave components with good performance. The components are light weight and truly airfilled with no dielectric support. This paper reviews several of these micromachined mm-wave components at 38 and 77 GHz for communications and radar applications

Micromachined 3D millimetre-wave and terahertz devices

Micromachining is a very promising technology to manufacture miniature three-dimensional (3D) devices at millimeter-wave (mm-wave) and terahertz (THz) frequencies. After a decade’s development, this technology has begun to demonstrate its viability and capability. It has delivered devices with competitive performance to traditional metal machining or electroforming, for coaxial and waveguide structures with sub-millimeter dimensions. This paper will discuss three strands of work that tackle three main challenges - fabrications, designs and measurements – in this technology. Several passive devices will be presented to illustrate the progress made on the multilayered SU8 techniques. These include guided transmission structures and devices based on rectangular coaxial lines, waveguides and free-space frequency selective surfaces. The concerned frequency covers from 30 GHz to 1 THz

Graphene-like carbon sheet/Fe3O4 nanocomposites derived from soda papermaking black liquor for high performance lithium ion batteries

Alkali lignins and its degradation products in the soda papermaking black liquor (SPBL) are renewable resource with the highest natural carbon content. In this work we convert SPBL into the high-performance carbon-based nanocomposite anodes. The unique functional groups of lignin biomass induce spontaneous formation of graphene-like carbon sheet (GCS) in-situ doped SiC/S. The lamellar GCS/FeO nanocomposite (GCS/FO-NC) is facilely prepared via one-step in-situ thermo-chemical method at 700\ua0°C, in which donut shaped FeO nanoparticles with superlattices and inner surface are homogeneously embedded in the interlayer of GCS and are also anchored on its surface. The GCS/FO-NC anode exhibits a ultrahigh first discharge specific capacity of 3829\ua0mAh\ua0g at 50\ua0mA\ua0g in a coin-type Li ion battery, which is more than 4 times the theoretical capacity (924\ua0mAh\ua0g) of FeO and 5 times that of the graphene anode (744\ua0mAh. g). Even at a high current density (1000\ua0mA\ua0g), it still exhibits a high reversible capacity (750\ua0mAh\ua0g) after 1400 discharge/charge cycles. More importantly, the removal efficiency of chemical oxygen demand of SPBL is up to 83.4% during the synthesis process, which reduce its load to environment and synthetic cost of carbon-based nanocomposite anodes

Estimating the carbon dynamics of South Korean forests from 1954 to 2012

Forests play an important role in the global carbon (C) cycle, and the South Korean forests also contribute to this global C cycle. While the South Korean forest ecosystem was almost completely destroyed by exploitation and the Korean War, it has successfully recovered because of national-scale reforestation programs since 1973. There have been several studies on the estimation of C stocks and balances over the past decades in the South Korean forests. However, a retrospective long-term study that includes biomass and dead organic matter C and validates dead organic matter C is still lacking. Accordingly, we estimated the C stocks and their changes of both biomass and dead organic matter C during the 1954-2012 period using a process-based model, the Korean Forest Soil Carbon model, and the 5th South Korean national forest inventory (NFI) report. Validation processes were also conducted based on the 5th NFI and statistical data. Simulation results showed that the biomass C stocks increased from 36.4 to 440.4 Tg C at a rate of 7.0 Tg C yrg-1 during the period 1954-2012. The dead organic matter C stocks increased from 386.0 to 463.1 Tg C at a rate of 1.3 Tg C yrg-1 during the same period. The estimates of biomass and dead organic matter C stocks agreed well with observed C stock data. The annual net biome production (NBP) during the period 1954-2012 was 141.3 g C mg-2 yrg-1, which increased from ??'8.8 g C mg-2 yrg-1 in 1955 to 436.6 g C mg-2 yrg-1 in 2012. Because of the small forested area, the South Korean forests had a comparatively lower contribution to the annual C sequestration by global forests. In contrast, because of the extensive reforestation programs, the NBP of South Korean forests was much higher than those of other countries. Our results could provide the forest C dynamics in South Korean forests before and after the onset of reforestation programs.Korea Forest Service (S111314L100120, S111114L030100) and Korea Ministry of Environment (C314-00131-0408-0).Scopu

Properties and Performance of Two Wide Field of View Cherenkov/Fluorescence Telescope Array Prototypes

A wide field of view Cherenkov/fluorescence telescope array is one of the main components of the Large High Altitude Air Shower Observatory project. To serve as Cherenkov and fluorescence detectors, a flexible and mobile design is adopted for easy reconfiguring of the telescope array. Two prototype telescopes have been constructed and successfully run at the site of the ARGO-YBJ experiment in Tibet. The features and performance of the telescopes are presented

Mitochondria transfer can enhance the murine embryo development

Purpose To evaluate the effect of mitochondrial transfer on embryonic development. Materials and methods Mitochondria concentrates were collected from murine hepatocytes and fertilized murine zygotes from young and older mice in the 2PN stage were subjected to mitochondrial transfer and cultured in vitro to evaluate the embryonic development. Results After extended in vitro culture, 37.65% and 20.91% embryos from the young mice developed to the blastocyst stage in the injected and control groups respectively, which is statistically significant. There was no difference in terms of hatching rates (1.76% and 1.82% respectively). Zygotes from the older mice (> 20 weeks old) that received mitochondrial transfer also had a better developmental outcome than the control group (54.35% and 18.92% developed to morula stage, 43.48% and 8.11% developed to the blastocyst stage respectively), which is statistically significant. Conclusions Our results for the murine model provide direct scientific evidence that mitochondrial transfer improves embryonic development. However, potential risks such as mitochondrial heteroplasmy, nuclear-mitochondrial interaction and epigenetic aspects all deserve further evaluation before mitochondrial transfer is applied clinically

Thermodynamic behavior of IIA string theory on a pp-wave

We obtain the thermal one loop free energy and the Hagedorn temperature of IIA superstring theory on the pp-wave geometry which comes from the circle compactification of the maximally supersymmetric eleven dimensional one. We use both operator and path integral methods and find the complete agreement between them in the free energy expression. In particular, the free energy in the $\mu \to \infty$ limit is shown to be identical with that of IIB string theory on maximally supersymmetric pp-wave, which indicates the universal thermal behavior of strings in the large class of pp-wave backgrounds. We show that the zero point energy and the modular properties of the free energy are naturally incorporated into the path integral formalism.Comment: 25 pages, Latex, JHEP style, v4: revised for clarity without change in main contents, version to appear in JHE

The autism-linked UBE3A T485A mutant E3 ubiquitin ligase activates the Wnt/β-catenin pathway by inhibiting the proteasome

UBE3A is a HECT domain E3 ubiquitin ligase whose dysfunction is linked to autism, Angelman syndrome, and cancer. Recently, we characterized a de novo autism-linked UBE3A mutant (UBE3AT485A) that disrupts phosphorylation control of UBE3A activity. Through quantitative proteomics and reporter assays, we found that the UBE3AT485A protein ubiquitinates multiple proteasome subunits, reduces proteasome subunit abundance and activity, stabilizes nuclear β-catenin, and stimulates canonical Wnt signaling more effectively than wild-type UBE3A. We also found that UBE3AT485A activates Wnt signaling to a greater extent in cells with low levels of ongoing Wnt signaling, suggesting that cells with low basal Wnt activity are particularly vulnerable to UBE3AT485A mutation. Ligase-dead UBE3A did not stimulate Wnt pathway activation. Overexpression of several proteasome subunits reversed the effect of UBE3AT485A on Wnt signaling. We also observed that subunits that interact with UBE3A and affect Wnt signaling are located along one side of the 19S regulatory particle, indicating a previously unrecognized spatial organization to the proteasome. Altogether, our findings indicate that UBE3A regulates Wnt signaling in a cell context-dependent manner and that an autism-linked mutation exacerbates these signaling effects. Our study has broad implications for human disorders associated with UBE3A gain or loss of function and suggests that dysfunctional UBE3A might affect additional proteins and pathways that are sensitive to proteasome activity

NGN, QCD_2 and chiral phase transition from string theory

We construct a D2-D8-$\bar{D8}$ configuration in string theory, it can be described at low energy by two dimensional field theory. In the weak coupling region, the low energy theory is a nonlocal generalization of Gross-Neveu(GN) model which dynamically breaks the chiral flavor symmetry $U(N_f)_L \times U(N_f)_R$ at large $N_c$ and finite $N_f$. However, in the strong coupling region, we can use the SUGRA/Born-Infeld approximation to describe the low energy dynamics of the system. Also, we analyze the low energy dynamics about the configuration of wrapping the one direction of D2 brane on a circle with anti-periodic boundary condition of fermions. The fermions and scalars on D2 branes get mass and decouple from the low energy theory. The IR dynamics is described by the $QCD_2$ at weak coupling. In the opposite region, the dynamics has a holographic dual description. And we have discussed the phase transition of chiral symmetry breaking at finite temperature. Finally, after performing T-duality, this configuration is related to some other brane configurations.Comment: 30 pages, 3 figures, minor change

Flavor changing single top quark production channels at e^+e^- colliders in the effective Lagrangian description

We perform a global analysis of the sensitivity of LEP2 and e^+e^- colliders with a c.m. energy in the range 500 - 2000 GeV to new flavor-changing single top quark production in the effective Lagrangian approach. The processes considered are sensitive to new flavor-changing effective vertices such as Ztc, htc, four-Fermi tcee contact terms as well as a right-handed Wtb coupling. We show that e^+ e^- colliders are most sensitive to the physics responsible for the contact tcee vertices. For example, it is found that the recent data from the 189 GeV LEP2 run can be used to rule out any new flavor physics that can generate these four-Fermi operators up to energy scales of \Lambda > 0.7 - 1.4 TeV, depending on the type of the four-Fermi interaction. We also show that a corresponding limit of \Lambda > 1.3 - 2.5 and \Lambda > 17 - 27 TeV can be reached at the future 200 GeV LEP2 run and a 1000 GeV e^+e^- collider, respectively. We note that these limits are much stronger than the typical limits which can be placed on flavor diagonal four-Fermi couplings. Similar results hold for \mu^+\mu^- colliders and for tu(bar) associated production. Finally we briefly comment on the necessity of measuring all flavor-changing effective vertices as they can be produced by different types of heavy physics.Comment: 34 pages, plain latex, 7 figures embadded in the text using epsfig. Added new references and discussions regarding their relevance to the paper. Added more comments on the comparison between flavor-changing and flavor-diagonal contact terms and on the importance of measuring the Ztc verte