Quantum Frequency Translation of Single-Photon States in Photonic Crystal Fiber

We experimentally demonstrate frequency translation of a nonclassical optical field via the Bragg scattering four-wave mixing process in a photonic crystal fiber (PCF). The high nonlinearity and the ability to control dispersion in PCF enable efficient translation between photon channels within the visible to-near-infrared spectral range, useful in quantum networks. Heralded single photons at 683 nm were translated to 659 nm with an efficiency of $28.6 \pm 2.2$ percent. Second-order correlation measurements on the 683-nm and 659-nm fields yielded $g^{(2)}_{683}(0) = 0.21 \pm 0.02$ and $g^{(2)}_{659}(0) = 0.19 \pm 0.05$ respectively, showing the nonclassical nature of both fields.Comment: 5 pages, 3 figure

Thermal effects on the structure and relaxation properties of poly(monocyclopentyl itaconate)

[EN] The effect of thermal treatment and subsequent chemical structural modifications on the viscoelastic and dielectric properties of PMCPI (poly(monocyclopentyl itaconate)) was studied. The low temperature relaxation (gamma-relaxation) is unaffected by the thermal history or chemical modifications. The intermediate relaxation (beta-relaxation) is shifted by about 40 degrees C to higher temperature after thermal treatment. The alpha-relaxation (related to the glass transition temperature T-g) suffers more striking changes when moving to higher temperatures.Díaz Calleja, R.; Sanchis Sánchez, MJ.; Gargallo, L.; Radic, D. (1995). Thermal effects on the structure and relaxation properties of poly(monocyclopentyl itaconate). Macromolecular Chemistry and Physics. 196(11):3789-3796. doi:10.1002/macp.1995.021961129S378937961961

Revegetation of ski runs in Serbia: Case studies of Mts. Stara Planina and Divčibare

Revegetation is the most sustainable method of soil stabilization at ski runs. In order to establish a stable plant community, it is recommended to use native species. However, non-native species are most often used. In this paper the revegetation of ski runs at two ski resorts is investigated: Divčibare and Stara Planina. Seven species were used for the revegetation of the ski run at the Divčibare ski resort of which six species were native. Six species were used for the revegetation of the Stara Planina ski resort, of which two species were native. It was established that the plant species used in the seed mixtures were suitable for erosion control at the investigated ski resorts

Photon pair-state preparation with tailored spectral properties by spontaneous four-wave mixing in photonic-crystal fiber

We study theoretically the generation of photon pairs by spontaneous four-wave mixing (SFWM) in photonic crystal optical fiber. We show that it is possible to engineer two-photon states with specific spectral correlation (``entanglement'') properties suitable for quantum information processing applications. We focus on the case exhibiting no spectral correlations in the two-photon component of the state, which we call factorability, and which allows heralding of single-photon pure-state wave packets without the need for spectral post filtering. We show that spontaneous four wave mixing exhibits a remarkable flexibility, permitting a wider class of two-photon states, including ultra-broadband, highly-anticorrelated states.Comment: 17 pages, 7 figures, submitte

Glaciers and small ice caps in the macro-scale hydrological cycle: an assessment of present conditions and future changes

Glacier and small ice cap melt water contributions to the global hydrologic cycle are an important component of human water supply and for sea level rise. This melt water is used in many arid and semi-arid parts of the world for direct human consumption as well as indirect consumption by irrigation for crops, serving as frozen reservoirs of water that supplement runoff during warm and dry periods of summer when it is needed the most. Additionally, this melt water reaching the oceans represents a direct input to sea level rise and therefore accurate estimates of this contribution have profound economic and geopolitical implications. It has been demonstrated that, on the scale of glacierized river catchments, land surface hydrological models can successfully simulate glacier contribution to streamflow. However, at global scales, the implementation of glacier melt in hydrological models has been rudimentary or non-existent. In this study, a global glacier mass balance model is coupled with the University of New Hampshire Water Balance/Transport Model (WBM) to assess recent and projected future glacier contributions to the hydrological cycle over the global land surface (excluding the ice sheets of Greenland and Antarctica). For instance, results of WBM simulations indicate that seasonal glacier melt water in many arid climate watersheds comprises 40 % or more of their discharge. Implicitly coupled glacier and WBM models compute monthly glacier mass changes and resulting runoff at the glacier terminus for each individual glacier from the globally complete Randolph Glacier Inventory including over 200 000 glaciers. The time series of glacier runoff is aggregated over each hydrological modeling unit and delivered to the hydrological model for routing downstream and mixing with non-glacial contribution of runoff to each drainage basin outlet. WBM tracks and uses glacial and non-glacial components of the in-stream water for filling reservoirs, transfers of water between drainage basins (inter-basin hydrological transfers), and irrigation along the global system of rivers with net discharge to the ocean. Climate scenarios from global climate models prepared for IPCC AR5 are used to explore an expected range of possible future glacier outflow variability to estimate the impacts on human use of these valuable waters and their poorly understood net contribution to sea level change

Characterization of p38α signaling networks in cancer cells using quantitative proteomics and phosphoproteomics

p38α (encoded by MAPK14) is a protein kinase that regulates cellular responses to almost all types of environmental and intracellular stresses. Upon activation, p38α phosphorylates many substrates both in the cytoplasm and nucleus, allowing this pathway to regulate a wide variety of cellular processes. While the role of p38α in the stress response has been widely investigated, its implication in cell homeostasis is less understood. To investigate the signaling networks regulated by p38α in proliferating cancer cells, we performed quantitative proteomic and phosphoproteomic analyses in breast cancer cells in which this pathway had been either genetically targeted or chemically inhibited. Our study identified with high confidence 35 proteins and 82 phosphoproteins (114 phosphosites) that are modulated by p38α, and highlighted the implication of various protein kinases, including MK2 and mTOR, in the p38α-regulated signaling networks. Moreover, functional analyses revealed an important contribution of p38α to the regulation of cell adhesion, DNA replication and RNA metabolism. Indeed, we provide experimental evidence supporting that p38α facilitates cancer cell adhesion, and showed that this p38α function is likely mediated by the modulation of the adaptor protein ArgBP2. Collectively, our results illustrate the complexity of the p38α regulated signaling networks, provide valuable information on p38α-dependent phosphorylation events in cancer cells, and document a mechanism by which p38α can regulate cell adhesion.Copyright © 2023 The Authors. Published by Elsevier Inc. All rights reserved

Mid-infrared optical parametric amplifier using silicon nanophotonic waveguides

All-optical signal processing is envisioned as an approach to dramatically decrease power consumption and speed up performance of next-generation optical telecommunications networks. Nonlinear optical effects, such as four-wave mixing (FWM) and parametric gain, have long been explored to realize all-optical functions in glass fibers. An alternative approach is to employ nanoscale engineering of silicon waveguides to enhance the optical nonlinearities by up to five orders of magnitude, enabling integrated chip-scale all-optical signal processing. Previously, strong two-photon absorption (TPA) of the telecom-band pump has been a fundamental and unavoidable obstacle, limiting parametric gain to values on the order of a few dB. Here we demonstrate a silicon nanophotonic optical parametric amplifier exhibiting gain as large as 25.4 dB, by operating the pump in the mid-IR near one-half the band-gap energy (E~0.55eV, lambda~2200nm), at which parasitic TPA-related absorption vanishes. This gain is high enough to compensate all insertion losses, resulting in 13 dB net off-chip amplification. Furthermore, dispersion engineering dramatically increases the gain bandwidth to more than 220 nm, all realized using an ultra-compact 4 mm silicon chip. Beyond its significant relevance to all-optical signal processing, the broadband parametric gain also facilitates the simultaneous generation of multiple on-chip mid-IR sources through cascaded FWM, covering a 500 nm spectral range. Together, these results provide a foundation for the construction of silicon-based room-temperature mid-IR light sources including tunable chip-scale parametric oscillators, optical frequency combs, and supercontinuum generators

DNA-dependent Protein Kinase Activity Is Not Required for Immunoglobulin Class Switching

Class switch recombination (CSR), similar to V(D)J recombination, is thought to involve DNA double strand breaks and repair by the nonhomologous end–joining pathway. A key component of this pathway is DNA-dependent protein kinase (DNA-PK), consisting of a catalytic subunit (DNA-PKcs) and a DNA-binding heterodimer (Ku70/80). To test whether DNA-PKcs activity is essential for CSR, we examined whether IgM+ B cells from scid mice with site-directed H and L chain transgenes were able to undergo CSR. Although B cells from these mice were shown to lack DNA-PKcs activity, they were able to switch from IgM to IgG or IgA with close to the same efficiency as B cells from control transgenic and nontransgenic scid/+ mice, heterozygous for the scid mutation. We conclude that CSR, unlike V(D)J recombination, can readily occur in the absence of DNA-PKcs activity. We suggest nonhomologous end joining may not be the (primary or only) mechanism used to repair DNA breaks during CSR

SPATIAL DISTRIBUTION OF APODEMUS FLAVICOLLIS AND A. AGRARIUS IN A FOREST COMMUNITY QUERCETUM-PETRAEA ON MT. AVALA (SERBIA)

ABSTRACT Spatial distribution of Apodemus flavicollis and A. agrarius were studied in a forest community Quercetum-petraea at Avala mountain (Serbia). During this study (1996)(1997)(1998)(1999