Plant Response to Cold Stress: Cold Stress Changes Antioxidant Metabolism in Heading Type Kimchi Cabbage (Brassica rapa L. ssp. Pekinensis).

Cold stress is known as the important yield-limiting factor of heading type Kimchi cabbage (HtKc, Brassica rapa L. ssp. pekinensis), which is an economically important crop worldwide. However, the biochemical and molecular responses to cold stress in HtKc are largely unknown. In this study, we conducted transcriptome analyses on HtKc grown under normal versus cold conditions to investigate the molecular mechanism underlying HtKc responses to cold stress. A total of 2131 genes (936 up-regulated and 1195 down-regulated) were identified as differentially expressed genes and were significantly annotated in the category of "response to stimulus". In addition, cold stress caused the accumulation of polyphenolic compounds, including p-coumaric, ferulic, and sinapic acids, in HtKc by inducing the phenylpropanoid pathway. The results of the chemical-based antioxidant assay indicated that the cold-induced polyphenolic compounds improved the free-radical scavenging activity and antioxidant capacity, suggesting that the phenylpropanoid pathway induced by cold stress contributes to resistance to cold-induced reactive oxygen species in HtKc. Taken together, our results will serve as an important base to improve the cold tolerance in plants via enhancing the antioxidant machinery.

Impact of moderate and extreme climate change scenarios on growth, morphological features, photosynthesis, and fruit production of hot pepper.

Horticultural crop production and changes in physiological aspects during the growing season may be affected by climate change factors (CC), which include increased temperature and the associated doubling or tripling of atmospheric CO2 concentrations. However, the potential effects are complex and many parameters might impact on the observed effects. To evaluate the effects of CC, the growth, yield, fruit characteristics, photosynthetic traits, and morphological characteristics of hot peppers were investigated. The hot peppers were grown under two CC scenarios, with the Representative Concentration Pathway (RCP) of 4.5 (Temp.; +3.4°C, CO2 conc.; 540 µmol/mol, Precipitation +17.3%) and RCP 8.5 (Temp.; +6.0°C and CO2 conc.; 940 µmol/mol, Precipitation +20.3%), respectively, using extreme weather simulators. This was compared with existing weather conditions occurring in Jeonju, South Korea in terms of air temperature, relative humidity, radiation, and precipitation. Overall, the plant height showed the highest under moderate CC conditions (RCP 4.5) among all the treatments tested. The number of leaves in the RCP 8.5 condition showed 7,739/plants, which was 2.2 times higher than that of the control. In addition, fruit shape was shortened and percentage dry matter was also the highest. The yield of hot pepper in the CC RCP 4.5 and 8.5 conditions were decreased by 21.5% and 89.2% when compared with that of the control, respectively. The days to harvest in the condition of CC scenarios were shortened from 5 to 13 compared with that of control, predominantly due to the increased air temperature. The results indicated that the severe RCP CC scenarios made reduction in the yields and negative affection on the fruit qualities. Overall, hot pepper was tolerant of mild CC scenarios of temperature × CO2 but was significantly affected by more extreme CC interacting parameter concentrations (or similar).

Efficient, tunable flip-chip-integrated III-V/Si hybrid external-cavity laser array.

We demonstrate a surface-normal coupled tunable hybrid silicon laser array for the first time using passively-aligned, high-accuracy flip chip bonding. A 2x6 III-V reflective semiconductor optical amplifier (RSOA) array with integrated total internal reflection mirrors is bonded to a CMOS SOI chip with grating couplers and silicon ring reflectors to form a tunable hybrid external-cavity laser array. Waveguide-coupled wall plug efficiency (wcWPE) of 2% and output power of 3 mW has been achieved for all 12 lasers. We further improved the performance by reducing the thickness of metal/dielectric stacks and achieved 10mW output power and 5% wcWPE with the same integration techniques. This non-invasive, one-step back end of the line (BEOL) integration approach provides a promising solution to high density laser sources for future large-scale photonic integrated circuits.

Error-free operation of a polarization-insensitive 4λ x 25 Gbps silicon photonic WDM receiver with closed-loop thermal stabilization of Si microrings.

We report the first closed-loop operation of a 100 Gbps polarization-insensitive, 4-channel wavelength-tracking WDM receiver in silicon photonics platform. Error-free operation is achieved with input polarization scrambling over input wavelength change of 4.5 nm using efficient thermal tuning of Si microring demux, corresponding to greater than 60°C fluctuation in temperature.

An all-solid-state, WDM silicon photonic digital link for chip-to-chip communications.

We describe a multiwavelength hybrid-integrated solid-state link on a 3 µm silicon-on-insulator (SOI) nanophotonic platform. The link spans three chips and employs germanium-silicon electroabsorption waveguide modulators, silicon transport waveguides, echelle gratings for multiplexing and demultiplexing, and pure germanium waveguide photo-detectors. The 8λ WDM Tx and Rx components are interconnected via a routing "bridge" chip using edge-coupled optical proximity communication. The packaged, retimed digital WDM link is demonstrated at 10 Gb/s and 10(-12) BER, with three wavelength channels consuming an on-chip power below 1.5 pJ/bit, excluding the external laser power.

Demonstration of 12.2% wall plug efficiency in uncooled single mode external-cavity tunable Si/III-V hybrid laser.

A Si/III-V hybrid laser has been a highly sought after device for energy-efficient and cost-effective high-speed silicon photonics communication. We present a high wall-plug efficiency external-cavity hybrid laser created by integrating an independently optimized SOI ring reflector and a III-V gain chip. In our demonstration, the uncooled integrated laser achieved a waveguide-coupled wall-plug efficiency of 12.2% at room temperature with an optical output power of ~10 mW. The laser operated single-mode near 1550 nm with a linewidth of 0.22 pm. This is a tunable light source with 8 nm wavelength tuning range. A proof-of-concept laser wavelength stabilization technique has also been demonstrated. Using a simple feedback loop, we achieved mode-hop-free operation in a packaged external-cavity hybrid laser as bias current was varied by 60mA.

A high-speed, tunable silicon photonic ring modulator integrated with ultra-efficient active wavelength control.

We report the first complete 10G silicon photonic ring modulator with integrated ultra-efficient CMOS driver and closed-loop wavelength control. A selective substrate removal technique was used to improve the ring tuning efficiency. Limited by the thermal tuner driver output power, a maximum open-loop tuning range of about 4.5nm was measured with about 14mW of total tuning power including the heater driver circuit power consumption. Stable wavelength locking was achieved with a low-power mixed-signal closed-loop wavelength controller. An active wavelength tracking range of > 500GHz was demonstrated with controller energy cost of only 20fJ/bit.

High power and widely tunable Si hybrid external-cavity laser for power efficient Si photonics WDM links.

A highly efficient silicon (Si) hybrid external cavity laser with a wavelength tunable ring reflector is fabricated on a complementary metal-oxide semiconductor (CMOS)-compatible Si-on-insulator (SOI) platform and experimental results with high output power are demonstrated. A III-V semiconductor gain chip is edge-coupled into a SOI cavity chip through a SiN(x) spot size converter and Si grating couplers are incorporated to enable wafer-scale characterization. The laser output power reaches 20 mW and the highest wall-plug efficiency of 7.8% is measured at 17.3 mW in un-cooled condition. The laser wavelength tuning ranges are 8 nm for the single ring reflector cavity and 35 nm for the vernier ring reflector cavity, respectively. The Si hybrid laser is a promising light source for energy-efficient Si CMOS photonic links.

Vertical-coupled high-efficiency tunable III-V- CMOS SOI hybrid external-cavity laser.

We demonstrate a hybrid III-V/SOI laser by vertically coupling a III-V RSOA chip with a SOI-CMOS chip containing a tunable wavelength selective reflector. We report a waveguide-coupled wall-plug-efficiency of 5.5% and output power of 10 mW. A silicon resistor-based microheater was integrated to thermally tune a ring resonator for precise lasing wavelength control. A high tuning efficiency of 2.2 nm/mW over a range of 18 nm was achieved by locally removing the SOI handler substrate. C-band single mode lasing was confirmed with a side mode suppression ratio of 35 dB. This grating coupler based vertical integration approach can be scaled up in two dimensions for efficient multi-wavelength sources in silicon photonics.

Ultralow-loss, high-density SOI optical waveguide routing for macrochip interconnects.

We report optical waveguides up to one meter long with 0.026 dB/cm loss fabricated in a 300nm thick SOI CMOS process. Combined with tight bends and compact interlayer grating couplers, we demonstrate a complete toolbox for ultralow-loss, high-density waveguide routing for macrochip interconnects.

Electrically pumped sub-wavelength metallo-dielectric pedestal pillar lasers.

Electrically driven subwavelength scale metallo-dielectric pedestal pillar lasers are designed and experimentally demonstrated. The metallo-dielectric cavity significantly enhances the quality factor (Q > 1500) of the wavelength and subwavelength scale lasers and the pedestal structure significantly reduces the threshold gain (< 400 cm(-1)) which can potentially enable laser operation at room temperature. We observed continuous wave lasing in 750 nm gain core radius laser at temperatures between 77 K and 140 K with a threshold current of 50 µA (at 77 K). We also observed lasing from a 355 nm gain core radius laser at temperatures between 77 K and 100 K.

Human cytomegalovirus infection causes degradation of Sp100 proteins that suppress viral gene expression.

The interferon-inducible Sp100 proteins are thought to play roles in the chromatin pathway and in transcriptional regulation. Sp100A, the smallest isoform, is one of the major components of PML nuclear bodies (NBs) that exhibit intrinsic antiviral activity against several viruses. Since PML NBs are disrupted by the immediate-early 1 (IE1) protein during human cytomegalovirus (HCMV) infection, the modulation of Sp100 protein expression or activity during infection has been suggested. Here, we show that Sp100 proteins are lost largely in the late stages of HCMV infection. This event required viral gene expression and involved posttranscriptional control. The mutant virus with deletion of the sequence for IE1 (CR208) did not have Sp100 loss. In CR208 infection, PML depletion by RNA interference abrogated the accumulation of SUMO-modified Sp100A and of certain high-molecular-weight Sp100 isoforms but did not significantly affect unmodified Sp100A, suggesting that the IE1-induced disruption of PML NBs is not sufficient for the complete loss of Sp100 proteins. Sp100A loss was found to require proteasome activity. Depletion of all Sp100 proteins by RNA silencing enhanced HCMV replication and major IE (MIE) gene expression. Sp100 knockdown enhanced the acetylation level of histones associated with the MIE promoter, demonstrating that the repressive effect of Sp100 proteins may involve, at least in part, the epigenetic control of the MIE promoter. Sp100A was found to interact directly with IE1 through the N-terminal dimerization domain. These findings indicate that the IE1-dependent loss of Sp100 proteins during HCMV infection may represent an important requirement for efficient viral growth.

Visible frequency magnetic activity in silver nanocluster metamaterial.

We experimentally observe magnetic resonance in the visible frequency region from self-assembled silver nanocluster metamaterials. Extensive numerical modeling studies were conducted to find the optimal nanocluster dimensions. Self-assembly of silver nanoparticles coated with nanoscale silica coating was then performed on polymer templates fabricated by laser interference lithography. The nanoclusters supported magnetic resonance in the visible region, and the extracted effective permeability exhibited Lorentz-like resonance. The experimentally observed lowest value for the real part of permeability was 0.06. The nanocluster metamaterial represents a practical metamaterial architecture that is compatible with the scalable bottom-up manufacturing process.

Metal nanocluster metamaterial fabricated by the colloidal self-assembly.

A new bottom-up approach for fabricating the optical metamaterial is reported. An array of metal nanoparticle clusters can provide both electric and magnetic activity in the optical frequency region through the excitation of the collective plasmon resonance. A two-dimensional square array of gold nanoparticle clusters (nanoclusters) was fabricated by using the template-directed colloidal self-assembly. The optical measurements showed strong extinction peaks in the near-infrared region owing to the electric resonance supported by the nanoclusters. The peak positions were in excellent agreement with the numerical simulations. The metal nanocluster metamaterial represents a promising new architecture for an optical metamaterial that can be fabricated by a scalable bottom-up fabrication technique.

Depressed-type of early colon cancer with extensive lymph node metastasis.

Early colorectal cancer (ECC) is defined as invasive tumor limited to the colonic and rectal mucosa or submucosa, regardless of the presence or absence of lymph node metastasis. The incidence of lymph node metastasis in ECC ranges from 0 to 15.4%, and risk factors include depth of submucosal invasion, growth patterns (polypoid or non-polypoid), histologic subclassification, and lymphatic invasion. Of non-polypoid growth patterns, the depressed types of colorectal cancer have higher malignant potential than polypoid types, even for small sizes. Unfortunately, this type is also difficult to detect on colonoscopic examination. In this report, we describe a case of depressed type ECC with extensive lymph node metastasis without regional lymph node involvement.