Toward predicting photosynthetic efficiency and biomass gain in crop genotypes over a field season.

Photosynthesis acclimates quickly to the fluctuating environment in order to optimize the absorption of sunlight energy, specifically the photosynthetic photon fluence rate (PPFR), to fuel plant growth. The conversion efficiency of intercepted PPFR to photochemical energy (ɛe) and to biomass (ɛc) are critical parameters to describe plant productivity over time. However, they mask the link of instantaneous photochemical energy uptake under specific conditions, that is, the operating efficiency of photosystem II (Fq'/Fm'), and biomass accumulation. Therefore, the identification of energy- and thus resource-efficient genotypes under changing environmental conditions is impeded. We long-term monitored Fq'/Fm' at the canopy level for 21 soybean (Glycine max (L.) Merr.) and maize (Zea mays) genotypes under greenhouse and field conditions using automated chlorophyll fluorescence and spectral scans. Fq'/Fm' derived under incident sunlight during the entire growing season was modeled based on genotypic interactions with different environmental variables. This allowed us to cumulate the photochemical energy uptake and thus estimate ɛe noninvasively. ɛe ranged from 48% to 62%, depending on the genotype, and up to 9% of photochemical energy was transduced into biomass in the most efficient C4 maize genotype. Most strikingly, ɛe correlated with shoot biomass in seven independent experiments under varying conditions with up to r = 0.68. Thus, we estimated biomass production by integrating photosynthetic response to environmental stresses over the growing season and identified energy-efficient genotypes. This has great potential to improve crop growth models and to estimate the productivity of breeding lines or whole ecosystems at any time point using autonomous measuring systems.

Dual-polarization multiplexing amorphous Si:H grating couplers for silicon photonic transmitters in the photonic BiCMOS backend of line.

In this paper, we report on polarization combining two-dimensional grating couplers (2D GCs) on amorphous Si:H, fabricated in the backend of line of a photonic BiCMOS platform. The 2D GCs can be used as an interface of a hybrid silicon photonic coherent transmitter, which can be implemented on bulk Si wafers. The fabricated 2D GCs operate in the telecom C-band and show an experimental coupling efficiency of - 5 dB with a wafer variation of ± 1.2 dB. Possibilities for efficiency enhancement and improved performance stability in future design generations are outlined and extension toward O-band devices is also investigated.

Si photonic-electronic monolithically integrated optical receiver with a built-in temperature-controlled wavelength filter.

We present a Si photonic-electronic integrated ring-resonator based optical receiver that contains a temperature-controlled ring-resonator filter (RRF), a Ge photodetector, and receiver circuits in a single chip. The temperature controller automatically determines the RRF temperature at which the maximum transmission of the desired WDM signal is achieved and maintains this condition against any temperature or input wavelength fluctuation. This Si photonic-electronic integrated circuit is realized with 0.25-µm photonic BiCMOS technology, and its operation is successfully confirmed with measurement.

Toward coherent O-band data center interconnects.

Upcoming generations of coherent intra/inter data center interconnects currently lack a clear path toward a reduction of cost and power consumption, which are the driving factors for these data links. In this work, the tradeoffs associated with a transition from coherent C-band to O-band silicon photonics are addressed and evaluated. The discussion includes the fundamental components of coherent data links, namely the optical components, fiber link and transceivers. As a major component of these links, a monolithic silicon photonic BiCMOS O-band coherent receiver is evaluated for its potential performance and compared to an analogous C-band device.

Genotypic variation in the response of soybean to elevated CO2.

The impact of elevated CO2 (eCO2) on soybean productivity is essential to the global food supply because it is the world's leading source of vegetable proteins. This study aimed to understand the yield responses and nutritional impact under free-air CO2 enrichment (FACE) conditions of soybean genotypes. Here we report that grain yield increased by 46.9% and no reduction in harvest index was observed among soybean genotypes. Elevated CO2 improved the photosynthetic carbon assimilation rate, leaf area, plant height, and aboveground biomass at vegetative and pod filling stages. Besides the positive effects on yield parameters, eCO2 differentially affected the overall grain quality. The levels of calcium (Ca), phosphorous (P), potassium (K), magnesium (Mg), manganese (Mn), iron (Fe), boron (B), and zinc (Zn) grain minerals decreased by 22.9, 9.0, 4.9, 10.1, 21.3, 28.1, 18.5, and 25.9% under eCO2 conditions, respectively. Soluble sugars and starch increased by 9.1 and 16.0%, respectively, phytic acid accumulation increased by 8.1%, but grain protein content significantly decreased by 5.6% across soybean genotypes. Furthermore, the antioxidant activity decreased by 36.9%, but the total phenolic content was not affected by eCO2 conditions. Genotypes, such as Winsconsin Black, Primorskaja, and L-117, were considered the most responsive to eCO2 in terms of yield enhancement and less affected in the nutritional quality. Our results confirm the existence of genetic variability in soybean responses to eCO2, and differences between genotypes in yield improvement and decreased sensitivity to eCO2 in terms of grain quality loss could be included in future soybean selection to enable adaptation to climate change.

The Nature of Chalcogen-Bonding-Type Tellurium-Nitrogen Interactions: A First Experimental Structure from the Gas Phase.

(C6 F5 )Te(CH2 )3 NMe2 (1), a perfluorophenyltellurium derivative capable of forming intramolecular N⋅⋅⋅Te interactions, was prepared and characterized. The donor-free reference substance (C6 F5 )TeMe (2) and the unsupported adduct (C6 F5 )(Me)Te⋅NMe2 Et (2 b) were studied in parallel. Molecular structures of 1, 2 and 2 b were determined by single-crystal X-ray diffraction and for 1 and 2 by gas-phase electron diffraction. The structure of 1 shows N⋅⋅⋅Te distances of 2.639(1) Š(solid) and 2.92(3) Š(gas). Ab initio plus NBO and QTAIM calculations show significant charge transfer effects within the N⋅⋅⋅Te interactions and indicate σ-hole interactions.

Molecular Mechanisms Responsible for Pharmacological Effects of Genipin on Mitochondrial Proteins.

Genipin, a natural compound from Gardenia jasminoides, is a well-known compound in Chinese medicine that is used for the treatment of cancer, inflammation, and diabetes. The use of genipin in classical medicine is hindered because of its unknown molecular mechanisms of action apart from its strong cross-linking ability. Genipin is increasingly applied as a specific inhibitor of proton transport mediated by mitochondrial uncoupling protein 2 (UCP2). However, its specificity for UCP2 is questionable, and the underlying mechanism behind its action is unknown. Here, we investigated the effect of genipin in different systems, including neuroblastoma cells, isolated mitochondria, isolated mitochondrial proteins, and planar lipid bilayer membranes reconstituted with recombinant proteins. We revealed that genipin activated dicarboxylate carrier and decreased the activity of UCP1, UCP3, and complex III of the respiratory chain alongside with UCP2 inhibition. Based on competitive inhibition experiments, the use of amino acid blockers, and site-directed mutagenesis of UCP1, we propose a mechanism of genipin's action on UCPs. At low concentrations, genipin binds to arginine residues located in the UCP funnel, which leads to a decrease in UCP's proton transporting function in the presence of long chain fatty acids. At concentrations above 200 µM, the inhibitory action of genipin on UCPs is overlaid by increased nonspecific membrane conductance due to the formation of protein-genipin aggregates. Understanding the concentration-dependent mechanism of genipin action in cells will allow its targeted application as a drug in the above-mentioned diseases.

Modular coherent photonic-aided payload receiver for communications satellites.

Ubiquitous satellite communications are in a leading position for bridging the digital divide. Fulfilling such a mission will require satellite services on par with fibre services, both in bandwidth and cost. Achieving such a performance requires a new generation of communications payloads powered by large-scale processors, enabling a dynamic allocation of hundreds of beams with a total capacity beyond 1 Tbit s-1. The fact that the scale of the processor is proportional to the wavelength of its signals has made photonics a key technology for its implementation. However, one last challenge hinders the introduction of photonics: while large-scale processors demand a modular implementation, coherency among signals must be preserved using simple methods. Here, we demonstrate a coherent photonic-aided receiver meeting such demands. This work shows that a modular and coherent photonic-aided payload is feasible, making way to an extensive introduction of photonics in next generation communications satellites.

The Expression of Uncoupling Protein 3 Coincides With the Fatty Acid Oxidation Type of Metabolism in Adult Murine Heart.

The involvement of mitochondrial uncoupling proteins 2 and 3 in the pathogenesis of cardiovascular diseases is widely acknowledged. However, contradictory reports show that the functions of UCP2/UCP3 are still disputed. We have previously described that UCP2 is highly abundant in cells that rely on glycolysis, such as stem, cancer and activated immune cells. In contrast, high amounts of UCP3 are present in brown adipose tissue, followed by heart and skeletal muscles - all known to metabolize fatty acids (FA) to a high extent. Using two different models - mouse embryonic stem cell (mESC) differentiation to cardiomyocytes (CM) and murine heart at different developmental stages - we now tested the concept that the expression ratio between UCP2 and UCP3 indicates the metabolism type in CM. Our results revealed the tight correlation between UCP3 abundance, expression of mitochondrial fatty acid oxidation (FAO) markers and presence of multiple connections between mitochondria and lipid droplets. We further demonstrated that the time course of UCP3 expression neither coincided with the onset of the electrical activity in CM, derived from mESC, nor with the expression of respiratory chain proteins, the observation which rendered protein participation in ROS regulation unlikely. The present data imply that UCP3 may facilitate FAO by transporting FAs into mitochondria. In contrast, UCP2 was highly abundant at early stages of heart development and in mESC. Understanding, that the expression patterns of UCP3 and UCP2 in heart during development reflect the type of the cell metabolism is key to the uncovering their different functions. Their expression ratio may be an important diagnostic criterion for the degree of CM differentiation and/or severity of a heart failure.

Reconfigurable monitoring and control system for tunable optical delay lines.

In this Letter, we propose a monitoring and control system (MCS) for operating tunable optical delay lines (TODLs), regardless of their operation principle and implementation technology. The monitoring system resorts to two out-of-band pilot tones added to the input optical signal. The amplitude and phase difference between tones are retrieved to the control system, which calculates and applies the TODL control signals. The MCS was validated using a Mach-Zehnder delay interferometer-based TODL, implemented in three different silicon photonic integrated circuits (PICs). The three PICs resort to different kinds of phase shifters based on thermo-optic, carrier-injection, and carrier-depletion effects. The proposed MCS enabled tuning the delay within the entire range of the TODL in all tested PICs. The scalability of the MCS for large-scale photonic beamformers is discussed.

Mechanism of Long-Chain Free Fatty Acid Protonation at the Membrane-Water Interface.

Long-chain free fatty acids (FFAs) play an important role in several physiological and pathological processes such as lipid fusion, adjustments of membrane permeability and fluidity, and the regulation of enzyme and protein activities. FFA-facilitated membrane proton transport (flip-flop) and FFA-dependent proton transport by membrane proteins (e.g., mitochondrial uncoupling proteins) are governed by the difference between FFA's intrinsic pKa value and the pH in the immediate membrane vicinity. Thus far, a quantitative understanding of the process has been hampered, because the pKa value shifts upon moving the FFA from the aqueous solution into the membrane. For the same FFA, pKa values between 5 and 10.5 were reported. Here, we systematically evaluated the dependence of pKa values on chain length and number of double bonds by measuring the ζ-potential of liposomes reconstituted with FFA at different pH values. The experimentally obtained intrinsic pKa values (6.25, 6.93, and 7.28 for DOPC membranes) increased with FFA chain length (C16, C18, and C20), indicating that the hydrophobic energy of transfer into the bilayer is an important pKa determinant. The observed pKa decrease in DOPC with increasing number of FFA double bonds (7.28, 6.49, 6.16, and 6.13 for C20:0, C20:1, C20:2, and C20:4, respectively) is in line with a decrease in transfer energy. Molecular dynamic simulations revealed that the ionized carboxylic group of the FFAs occupied a fixed position in the bilayer independent of chain length, underlining the importance of Born energy. We conclude that pKa is determined by the interplay between the energetic costs for 1) burying the charged moiety into the lipid bilayer and 2) transferring the hydrophobic protonated FFA into the bilayer.

Dimensioning of a multibeam coherent photonic beamformer fed by a phased array antenna.

The design and dimensioning of a photonic-aided payload for a multi-beam high-throughput communications satellite is a complex problem in which the antenna, RF and photonic subsystems must be considered as a whole for achieving best performance with lowest mass and power consumption. In this paper, we propose and dimension the receiving stage of a communications satellite comprising a phased array antenna (PAA) feeding a multibeam photonic beamforming system (PBS). The PBS uses a single wavelength and resorts to heterodyne detection such that the retrieved beams are frequency downconverted. End-to-end system modeling shows that the complexity of the PAA and PBS can be traded-off for signal-to-noise ratio (SNR) or power consumption without compromising the beam width. The dimensioning of a realistic scenario is presented, showing that an SNR and beam crosstalk on the order of 20 dB are achievable with a total power consumption below 1 kW for a typical number of 100 antenna elements (AEs).

1.024 Tb/s wavelength conversion in a silicon waveguide with reverse-biased p-i-n junction.

We experimentally show an all-optical wavelength conversion of 8 × 32-GBd single-polarization 16QAM signals using a silicon nano-rib waveguide. The application of reverse biasing of the p-i-n junction of the waveguide allows a conversion efficiency of -8.5 dB with a measured 3-dB optical bandwidth of about 40 nm. Using digital coherent reception, it is shown that the receiver optical signal-to-noise ratio penalty, at a bit-error ratio of 1 × 10-3, of the wavelength-converted signals over all eight channels was less than 0.6 dB with reference to their respective back-to-back signal channels.

Nutrient deprivation in neuroblastoma cells alters 4-hydroxynonenal-induced stress response.

4-hydroxy-2-nonenal (HNE), a toxic lipid peroxidation product, is associated with oxidative damage in cells and involved in various diseases including the initiation and progression of cancer. Cancer cells have a high, adaptable metabolism with a shift from oxidative phosphorylation to glycolysis and rely on high levels of glucose and glutamine as essential nutrients for cell growth. Here we investigated whether the toxic effects of HNE on the mitochondrial membrane potential (MMP) of cancer cells depends on their metabolic state by deprivation of glucose and/or glutamine. The addition of 16 µM HNE to N18TG2 neuroblastoma cells incubated in glucose medium led to a severe reduction of MMP, which was similar to the MMP of cells fed with both glucose and glutamine. In contrast, HNE addition to cells starved in glutamine medium increased their MMP slightly for a prolonged time period and this was accompanied by increased cellular survival. We found that ß-oxidation of HNE did not cause the increased MMP, since the aldehyde dehydrogenase was distinctly more active in cells with glucose medium. However, after blocking fatty acid ß-oxidation in cells starved in glutamine medium with etomoxir, which inhibits carnitine palmitoyltransferase 1, HNE addition induced a strong reduction of MMP similar to cells in glucose medium. Surprisingly, the effect of more toxic 4-oxo-2-nonenal was less pronounced. Our results suggest that in contrast to cells fed with glucose, glutamine-fed cancer cells are capable of ß-oxidizing fatty acids to maintain their MMP to combat the toxic effects of HNE.

High bandwidth, high responsivity waveguide-coupled germanium p-i-n photodiode.

A novel waveguide-coupled germanium p-i-n photodiode is demonstrated which combines high responsivity with very high -3 dB bandwidth at a medium dark current. Bandwidth values are 40 GHz at zero bias and more than 70 GHz at -1 V. Responsivity at 1.55 µm wavelength ranges from 0.84 A/W at zero bias to 1 A/W at -1 V. Room temperature dark current density at -1 V is about 1 A/cm2. The high responsivity mainly results from the use of a new, low-loss contact scheme, which moreover also reduces the negative effect of photo carrier diffusion on bandwidth.

Vertical optical ring resonators fully integrated with nanophotonic waveguides on silicon-on-insulator substrates.

We demonstrate full integration of vertical optical ring resonators with silicon nanophotonic waveguides on silicon-on-insulator substrates to accomplish a significant step toward 3D photonic integration. The on-chip integration is realized by rolling up 2D differentially strained TiO(2) nanomembranes into 3D microtube cavities on a nanophotonic microchip. The integration configuration allows for out-of-plane optical coupling between the in-plane nanowaveguides and the vertical microtube cavities as a compact and mechanically stable optical unit, which could enable refined vertical light transfer in 3D stacks of multiple photonic layers. In this vertical transmission scheme, resonant filtering of optical signals at telecommunication wavelengths is demonstrated based on subwavelength thick-walled microcavities. Moreover, an array of microtube cavities is prepared, and each microtube cavity is integrated with multiple waveguides, which opens up interesting perspectives toward parallel and multi-routing through a single-cavity device as well as high-throughput optofluidic sensing schemes.

Optimization of fiber grating couplers on SOI using advanced search algorithms.

A one-dimensional fiber grating coupler is derived from a waveguide with random etches using implementations of particle swarm and genetic algorithms. The resulting gratings yield a theoretical coupling efficiency of up to 1.1 dB and prompt clear design rules for the layout of highly efficient fiber grating couplers.

Phase regeneration of DPSK signals in a silicon waveguide with reverse-biased p-i-n junction.

Phase regeneration of differential phase-shift keying (DPSK) signals is demonstrated using a silicon waveguide as nonlinear medium for the first time. A p-i-n junction across the waveguide enables decreasing the nonlinear losses introduced by free-carrier absorption (FCA), thus allowing phase-sensitive extinction ratios as high as 20 dB to be reached under continuous-wave (CW) pumping operation. Furthermore the regeneration properties are investigated under dynamic operation for a 10-Gb/s DPSK signal degraded by phase noise, showing receiver sensitivity improvements above 14 dB. Different phase noise frequencies and amplitudes are examined, resulting in an improvement of the performance of the regenerated signal in all the considered cases.

Matching p-i-n-junctions and optical modes enables fast and ultra-small silicon modulators.

In this article a new method is presented that allows for low loss implementation of fast carrier transport structures in diffraction limited photonic crystal resonators. We utilize a 'node-matched doping' process in which precise silicon doping results in comb-like shaped, highly-doped diode areas that are matched to the spatial field distribution of the optical modes of a Fabry-Pérot resonator. While the doping is only applied to areas with low optical field strength, the intrinsic diode region overlaps with an optical field maximum. The presented node-matched diode-modulators, combining small size, high-speed, thermal stability and energy-efficient switching could become the centerpiece for monolithically integrated transceivers.