Modulational-instability-free pulse compression in anti-resonant hollow-core photonic crystal fiber

Gas-filled hollow-core photonic crystal fiber (PCF) is used for efficient nonlinear temporal compression of femtosecond laser pulses, two main schemes being direct soliton-effect self-compression, and spectral broadening followed by phase compensation. To obtain stable compressed pulses, it is crucial to avoid decoherence through modulational instability (MI) during spectral broadening. Here we show that changes in dispersion due to spectral anti-crossings between the fundamental core mode and core wall resonances in anti-resonant-guiding hollow-core PCF can strongly alter the MI gain spectrum, enabling MI-free pulse compression for optimized fiber designs. In addition, higher-order dispersion can introduce MI even when the pump pulses lie in the normal dispersion region

Novel mid-infrared dispersive wave generation in gas-filled PCF by transient ionization-driven changes in dispersion

Gas-filled hollow-core photonic crystal fibre (PCF) is being used to generate ever wider supercontinuum spectra, in particular via dispersive wave (DW) emission in the deep and vacuum ultraviolet, with a multitude of applications. DWs are the result of the resonant transfer of energy from a self-compressed soliton, a process which relies crucially on phase matching. It was recently predicted that, in the strong-field regime, the additional transient anomalous dispersion introduced by gas ionization would allow phase-matched DW generation in the mid-infrared (MIR)-something that is forbidden in the absence of free electrons. Here we report for the first time the experimental observation of such MIR DWs, embedded in a 4.7-octave-wide supercontinuum that uniquely reaches simultaneously to the vacuum ultraviolet, with up to 1.7 W of total average power

Improved Nonrelativistic QCD for Heavy Quark Physics

We construct an improved version of nonrelativistic QCD for use in lattice simulations of heavy quark physics, with the goal of reducing systematic errors from all sources to below 10\%. We develop power counting rules to assess the importance of the various operators in the action and compute all leading order corrections required by relativity and finite lattice spacing. We discuss radiative corrections to tree level coupling constants, presenting a procedure that effectively resums the largest such corrections to all orders in perturbation theory. Finally, we comment on the size of nonperturbative contributions to the coupling constants.Comment: 40 pages, 2 figures (not included), in LaTe

Large Attractive Depletion Interactions in Soft Repulsive-Sphere Binary Mixtures

We consider binary mixtures of soft repulsive spherical particles and calculate the depletion interaction between two big spheres mediated by the fluid of small spheres, using different theoretical and simulation methods. The validity of the theoretical approach, a virial expansion in terms of the density of the small spheres, is checked against simulation results. Attention is given to the approach toward the hard-sphere limit, and to the effect of density and temperature on the strength of the depletion potential. Our results indicate, surprisingly, that even a modest degree of softness in the pair potential governing the direct interactions between the particles may lead to a significantly more attractive total effective potential for the big spheres than in the hard-sphere case. This might lead to significant differences in phase behavior, structure and dynamics of a binary mixture of soft repulsive spheres. In particular, a perturbative scheme is applied to predict the phase diagram of an effective system of big spheres interacting via depletion forces for a size ratio of small and big spheres of 0.2; this diagram includes the usual fluid-solid transition but, in the soft-sphere case, the metastable fluid-fluid transition, which is probably absent in hard-sphere mixtures, is close to being stable with respect to direct fluid-solid coexistence. From these results the interesting possibility arises that, for sufficiently soft repulsive particles, this phase transition could become stable. Possible implications for the phase behavior of real colloidal dispersions are discussed.Comment: 31 pages, 8 figures; version accepted for publication in the Journal of Chemical Physic

Kajian Peran Media Online Bagi Pemuda Di Gereja Advent Walantakan Kecamatan Langowan Barat

Tidak dapat dipungkiri bahwa media online mempunyai pengaruh besar dalam kehidupan para pemuda gereja ini. Bagi mereka, media online seakan sudah menjadi candu, tiada hari tanpa menggunakan media online bahkan bisa sampai 24 jam mereka menggunakan media online ini. Media online yang sering digunakan adalah media sosial seperti Facebook, Path, Line, Instagram, Blackberry messenger, dan Youtube. Media online memang menawarkan banyak kemudahan yang membuat para pemuda di gereja Advent Walantakan Kecamatan Langowan Barat ini betah berlama-lama di dunia maya.Dari sekian kelebihan yang telah ditawarkan dari media online ini, terdapat juga banyak dampak negatif yang bermunculan, peneliti mendapatkan fenomena dimana tidak jarang pemuda-pemuda di Gereja Advent Walantakan Kecamatan Langowan Barat ini lebih memilih memainkan atau menggunakan media online, meskipun ia berada ditengah-tengah suatu kegiatan gereja atau sosialisasi dengan orang–orang yang ada disekitarnya. Banyaknya peredaran gambar-gambar maupun video-video porno sekarang ini sudah dianggap hal biasa dalam lalu lintas data komunikasi melalui media online. Selain itu adanya hal-hal yang memberikan kesan rasisme dan unsur-unsur SARA didalamnya dapat mengancam serta merusak kehidupan masyarakat terutama para pemuda Gereja Advent di Walantakan Kecamatan Langowan Barat ini.Hasil penelitian menemukan bahwa para pemuda yang menjadi informan dalam penelitian ini memiliki beragam sarana media online untuk mengakses sarana internet guna menunjang peningkatan mereka dalam hal kemajuan teknologi dan juga agar lebih mudah dalam hal berkomunikasi apabila ada kegiatan-kegiatan pemuda di gereja dan juga organisasi gereja yang mereka jalankan.Menurut mereka media online juga dapat mendorong mereka dalam mencari pertemanan yang baru dengan menggunakan media social, sehingga hal itu juga merupakan salah satu hal yang mendorong para pemuda gereja ini untuk menggunakan media online. Seperti diketahui jika tidak ada pertemanan di media sosial rasanya sudah ketinggalan jaman.Pengguna media internet atau online tidak hanya didorong dari diri sendiri karena keingintahuan akan media baru juga mendorong pertemanan atau mempercepat pertemanan baik sesama teman pemuda di gereja maupun teman-teman lama atau juga teman-teman yang berasal dari berbagai penjuru dunia

PHz-wide spectral interference through coherent plasma-induced fission of higher-order solitons

We identify a novel regime of soliton-plasma interactions in which high-intensity ultrashort pulses of intermediate soliton order undergo coherent plasma-induced fission. Experimental results obtained in gas-filled hollow-core photonic crystal fibers are supported by rigorous numerical simulations. The cumulative blueshift of higher-order input solitons with ionizing intensities results in pulse splitting before the ultimate self-compression point, leading to the generation of robust pulse pairs with PHz bandwidths. The novel dynamics closes the gap between plasma-induced adiabatic soliton compression and modulational instability

Direct characterisation of tuneable few-femtosecond dispersive-wave pulses in the deep UV

Dispersive wave emission (DWE) in gas-filled hollow-core dielectric waveguides is a promising source of tuneable coherent and broadband radiation, but so far the generation of few-femtosecond pulses using this technique has not been demonstrated. Using in-vacuum frequency-resolved optical gating, we directly characterise tuneable 3fs pulses in the deep ultraviolet generated via DWE. Through numerical simulations, we identify that the use of a pressure gradient in the waveguide is critical for the generation of short pulses.Comment: 5 pages, 4 figure

Mutations of Bruton's tyrosine kinase gene in Brazilian patients with X-linked agammaglobulinemia

Mutations in Bruton's tyrosine kinase (BTK) gene are responsible for X-linked agammaglobulinemia (XLA), which is characterized by recurrent bacterial infections, profound hypogammaglobulinemia, and decreased numbers of mature B cells in peripheral blood. We evaluated 5 male Brazilian patients, ranging from 3 to 10 years of age, from unrelated families, whose diagnosis was based on recurrent infections, markedly reduced levels of IgM, IgG and IgA, and circulating B cell numbers <2%. BTK gene analysis was carried out using PCR-SSCP followed by sequencing. We detected three novel (Ala347fsX55, I355T, and Thr324fsX24) and two previously reported mutations (Q196X and E441X). Flow cytometry revealed a reduced expression of BTK protein in patients and a mosaic pattern of BTK expression was obtained from mothers, indicating that they were XLA carriers