Photon-assisted ultrafast electron-hole plasma expansion in direct band semiconductors.

Time-resolved terahertz spectroscopy is used to investigate formation and ultrafast long-distance propagation of electron-hole plasma in strongly photoexcited GaAs and InP. The observed phenomena involve fundamental interactions of electron-hole system with light, which manifest themselves in two different regimes: a coherent one with the plasma propagation speeds up to /10 (in GaAs at 20 K) and an incoherent one reaching up to /25 (in InP at 20 K), both over a macroscopic distance >100 μm. We explore a broad range of experimental conditions by investigating the two materials, by tuning their band gap with temperature and by controlling the interaction strength with the optical pump fluence.

A Frustrated Antipolar Phase Analogous to Classical Spin Liquids.

The study of magnetic frustration in classical spin systems is motivated by the prediction and discovery of classical spin liquid states. These uncommon magnetic phases are characterized by a massive degeneracy of their ground state implying a finite magnetic entropy at zero temperature. While the classical spin liquid state is originally predicted in the Ising triangular lattice antiferromagnet in 1950, this state has never been experimentally observed in any triangular magnets.

Undulations of Smectic A Layers in Achiral Liquid Crystals Manifested as Stripe Textures.

Self-assembly of organic molecules represents a fascinating playground to create various liquid crystalline nanostructures. In this Letter, we study layer undulations on micrometer scale in smectic A phases for achiral compounds, experimentally demonstrated as regular stripe patterns induced by thermal treatment. Undulations, including their anharmonic properties, are evaluated by means of polarimetric imaging and light diffraction experiments in cells with various thicknesses.

Ultrafast Long-Distance Electron-Hole Plasma Expansion in GaAs Mediated by Stimulated Emission and Reabsorption of Photons.

Electron-hole plasma expansion with velocities exceeding c/50 and lasting over 10 ps at 300 K was evidenced by time-resolved terahertz spectroscopy. This regime, in which the carriers are driven over >30  μm is governed by stimulated emission due to low-energy electron-hole pair recombination and reabsorption of the emitted photons outside the plasma volume. At low temperatures a speed of c/10 was observed in the regime where the excitation pulse spectrally overlaps with emitted photons, leading to strong coherent light-matter interaction and optical soliton propagation effects.

Terahertz charge transport dynamics in 3D graphene networks with localization and band regimes.

Terahertz steady-state and time-resolved conductivity and permittivity spectra were measured in 3D graphene networks assembled in free-standing covalently cross-linked graphene aerogels. Investigation of a transition between reduced-graphene oxide and graphene controlled by means of high-temperature annealing allowed us to elucidate the role of defects in the charge carrier transport in the materials. The THz spectra reveal increasing conductivity and decreasing permittivity with frequency.

Terahertz Magnetic and Lattice Excitations in van der Waals Ferromagnet VI.

We use the synergy of infrared, terahertz, and Raman spectroscopies with DFT calculations to shed light on the magnetic and lattice properties of VI. The structural transition at = 79 K is accompanied by a large splitting of polar phonon modes. Below , strong ferromagnetic fluctuations are observed.

Improving security in terahertz wireless links using beam symmetry of vortex and Gaussian beams.

We present an effective way to improve the security of a point-to-point terahertz wireless link on a physical layer supported by numerical calculations in the frame of Fourier optics. The improvement is based on original countermeasures which exploit three independent degrees of freedom of the carrier wave: its intensity and azimuthal and radial symmetry. When the transmission line is intercepted, the light beam is subject to changes in either of the three degrees of freedom.

A Clinicoepidemiological Study of Melanoma in Young Patients (20 Years of Age or Less) in Alberta, Canada, From 1992 to 2011.

The epidemiological trends of malignant melanoma have been well described in the literature. However, there remains a paucity of population-based studies assessing melanoma epidemiology in our younger patients (20 years of age or less). Other studies indicate that melanoma incidence has risen in pediatric populations over the last several decades and that these tumors may display different clinical characteristics from those arising in adult populations.

Crisaborole 2% Ointment (Eucrisa) for Atopic Dermatitis.

Atopic dermatitis is a common cutaneous disease with significant morbidity affecting children and adults. The mainstay of atopic dermatitis therapy has typically included emollients, topical corticosteroids, and topical calcineurin inhibitors. Among the newer advances recently introduced is crisaborole (Eucrisa™), a phosphodiesterase type-4 inhibitor (PDE-4) for the treatment of mild moderate atopic dermatitis.

Terahertz electrical writing speed in an antiferromagnetic memory.

The speed of writing of state-of-the-art ferromagnetic memories is physically limited by an intrinsic gigahertz threshold. Recently, realization of memory devices based on antiferromagnets, in which spin directions periodically alternate from one atomic lattice site to the next has moved research in an alternative direction. We experimentally demonstrate at room temperature that the speed of reversible electrical writing in a memory device can be scaled up to terahertz using an antiferromagnet.

Disfiguring ulcerative neutrophilic dermatosis secondary to doxycycline and isotretinoin in an adolescent boy with acne conglobata.

Acne fulminans is an uncommon and debilitating disease that presents as an acute eruption of nodular and ulcerative acne lesions in association with systemic symptoms. It occurs commonly during treatment of severe acne (eg, acne conglobata) with isotretinoin in young adolescent male patients. Isotretinoin and doxycycline also can potentially induce development of neutrophilic dermatoses in patients with severe acne lesions, which are characterized by the acute appearance of painful ulcerative papulonodules accompanied by systemic symptoms including fever and leukocytosis.

Vitamin B Derivative (Nicotinamide)Appears to Reduce Skin Cancer Risk.

Nicotinamide, an amide form of vitamin B3, has shown the potential to treat a variety of dermatological conditions, including acne, rosacea, and atopic dermatitis. Recent studies have demonstrated the role of nicotinamide, in both topical and oral forms, as a chemopreventive agent against skin cancer. Its anti-carcinogenic role may be due to its ability to enhance DNA repair and prevent ultraviolet (UV)-induced immunosuppression, which is known to contribute to the progression of pre-malignant lesions.

Bulk magnetic terahertz metamaterials based on dielectric microspheres.

Rigid metamaterials were prepared by embedding TiO microspheres into polyethylene. These structures exhibit a series of Mie resonances where the lowest-frequency one is associated with a strong dispersion in the effective magnetic permeability. Using time-domain terahertz spectroscopy, we experimentally demonstrated the magnetic nature of the observed resonance.

Self-referenced ultra-broadband transient terahertz spectroscopy using air-photonics.

Terahertz (THz) air-photonics employs nonlinear interactions of ultrashort laser pulses in air to generate and detect THz pulses. As air is virtually non-dispersive, the optical-THz phase matching condition is automatically met, thus permitting the generation and detection of ultra-broadband THz pulses covering the entire THz spectral range without any gaps. Air-photonics naturally offers unique opportunities for ultra-broadband transient THz spectroscopy, yet many critical challenges inherent to this technique must first be resolved.

Long-range and high-speed electronic spin-transport at a GaAs/AlGaAs semiconductor interface.

Spin-valves or spin-transistors in magnetic memories and logic elements are examples of structures whose functionality depends crucially on the length and time-scales at which spin-information is transferred through the device. In our work we employ spatially resolved optical pump-and-probe technique to investigate these fundamental spin-transport parameters in a model semiconductor system. We demonstrate that in an undoped GaAs/AlGaAs layer, spins are detected at distances reaching more than ten microns at times as short as nanoseconds.

A clinicopathologic review of a case series of dermatofibrosarcoma protuberans with fibrosarcomatous differentiation.

Background: Dermatofibrosarcoma protuberans with fibrosarcomatous differentiation (DFSP-FS) is a rare variant of DFSP with a more aggressive clinical course, characterized by higher rates of local recurrence, metastasis, and death.

Methods: We conducted a clinicopathologic review of all DFSP-FS cases that occurred in Alberta, Canada, from 1997 to 2007.

Results: Of the 75 DFSP cases reviewed, 4 demonstrated fibrosarcomatous differentiation.

Transition between metamaterial and photonic-crystal behavior in arrays of dielectric rods.

Using finite-difference time-domain simulations, we study the interactions of electromagnetic radiation with a square array of dielectric rods parallel to the electric vector. We observe the electric and magnetic Mie resonances which induce intervals of negative effective permittivity and permeability and which contribute to the formation of the photonic band gaps. Owing to the interplay of these phenomena, a narrow spectral range with a negative refractive index can occur.

Fatal case of vulvar pyoderma gangrenosum with pulmonary involvement: case presentation and literature review.

Introduction: We report a case of a 61-year-old woman with locally destructive vulvar pyoderma gangrenosum (PG) with pulmonary involvement who was refractory to numerous systemic therapies and developed complications resulting in her demise.

Objective: To report a rare case of treatment-resistant vulvar PG with pulmonary involvement that proved to be fatal.

Methods: PubMed was used to search for other reports that discuss PG, or more specifically perigenital PG, with pulmonary involvement.

Near-field probing of Mie resonances in single TiO2 microspheres at terahertz frequencies.

We show experimentally that poly-crystalline TiO2 spheres, 20-30 μm in diameter, exhibit a magnetic dipole Mie resonance in the terahertz (THz) frequency band (1.0-1.6 THz) with a narrow line-width (<40 GHz).

Cutaneous squamous cell carcinoma in two pediatric lung transplant patients on prolonged voriconazole treatment.

Oral voriconazole is commonly used for treatment and prophylaxis of invasive fungal disease post-LTx. Development of cutaneous SCC has been described in adult LTx recipients, although it is extremely rare in children. We describe two Caucasian children who developed cutaneous SCC beyond three yr post-LTx.

Multiple soft-mode vibrations of lead zirconate.

Polarized Raman, IR, and time-domain THz spectroscopy of orthorhombic lead zirconate single crystals have yielded a comprehensive picture of temperature-dependent quasiharmonic frequencies of its low-frequency phonon modes. It is argued that these modes primarily involve vibrations of Pb ions and librations of oxygen octahedra. Their relation to phonon modes of the parent cubic phase is proposed.

Epidemiology of sebaceous carcinoma in Alberta, Canada, from 1988 to 2007.

Background: The epidemiology of sebaceous carcinoma (SC) has not previously been examined in a Canadian population.

Objective: To determine the epidemiologic trends of SC in Alberta, Canada, from 1988 to 2007.

Methods: This study was a population-based, retrospective, epidemiologic analysis of SC in Alberta over a 20-year span.

Epidemiology of dermatofibrosarcoma protuberans in Alberta, Canada, from 1988 to 2007.

Background: There have only been a few population-based, epidemiologic studies assessing dermatofibrosarcoma protuberans (DFSP).

Objective: To assess the epidemiology of DFSP in Alberta, Canada, over a 20-year period.

Methods: A population-based, retrospective analysis of all cases of DFSP in Alberta was conducted using data from the Alberta Cancer Registry.