RESUMO
Generating energetic, few-cycle laser pulses with stabilized carrier-envelope phase at a high-repetition rate constitutes a first step to access the ultra-fast dynamics underlying the interaction of matter with intense, ultrashort pulses in attosecond science or high-field physics. We present here a Ti:Sa-based 1 kHz TW-class laser delivering 17.8 fs pulses with 350 mrad shot-to-shot CEP noise based on an original 10 kHz front-end design. In parallel to this short pulse duration operation mode, it is possible to tune the output wavelength of the front end within a 90 nm range around 800 nm.
RESUMO
The former Eagle and Telbel mine site (hereafter referred to as Joutel mine), located near the town of Joutel in the Nord-du-Québec (Canada) houses a tailings storage facility (TSF) that has been inactive since 1996. Fresh, unweathered tailings (beneath 10-30â¯cm of oxidized horizon) are characterized by an average sulfide content of 6-7â¯wt% and an average Fe-Mn-carbonate content of 20-40â¯wt%. The oxidation of Joutel's tailings under atmospheric conditions resulted in the precipitation of secondary phases such as ferric oxyhydroxides and gypsum. Accumulation of these secondary phases throughout the TSF caused cementation and agglomeration of grains, which decreased the porosity of the material in a horizon below the surface. This horizon, which is referred to as hardpan, is frequently encountered within fine, reactive tailings. Characterizations showed that hardpans have a highly compact texture. The formation of hardpans limits vertical water infiltration and oxygen diffusion and these layers greatly affect the global geochemical behavior of underlying tailings in the Joutel TSF by protecting the unweathered material from oxidation. As a result, the water quality of the TSF is largely controlled by the reactivity of the upper oxidized tailings horizon. Joutel's oxidized tailings showed an acidic behavior early during laboratory kinetic leaching tests despite the near absence of sulfides and neutralizing minerals. However, when unweathered tailings were added under oxidized tailings, the water became neutral and metal leaching rates were reduced. After over a year of laboratory leaching tests, hardpans formed within the columns and the natural phenomenon was reproduced under laboratory conditions.
RESUMO
We present a compact 10 kHz Ti:Sa front end relying on an original double-crystal regenerative amplifier design. This new configuration optimizes the thermal heat load management, allowing the production of a 110 nm large spectrum and maintaining a good beam profile quality. The front end delivers up to 5 W after compression, 17 fs pulses with a 170 mrad shot-to-shot residual carrier-envelope phase noise.
RESUMO
The bulk laser-induced damage threshold (LIDT) fluence of Ti:sapphire is determined under single-pulse irradiation from the femtosecond to nanosecond temporal regimes in the visible and near-infrared spectral domains. In the range of explored laser conditions, the LIDT fluence increases with both pulse duration and wavelength. The results are also compared to laser interaction with sapphire samples and show an increased resistance to laser damage when the material is doped with Ti(3+) ions. These conclusions are of interest for robust operation of high-peak-power femtosecond Ti:sapphire laser chains.
RESUMO
The Wnt/beta-catenin signaling pathway is activated in many human hepatocellular carcinomas (HCC). We tried to identify the genes involved in carcinogenesis and progression of HCC with beta-catenin mutations. We used PCR-based subtractive hybridization to compare gene expression between malignant and benign components of a human HCC occurring in pre-existing adenoma activated for beta-catenin. Two of the genes identified belong to the Regenerating gene (REG) family. They encode the Regenerating islet-derived 3 alpha (REG3A/HIP/PAP/REG-III) and 1 alpha (REG1A) proteins, both involved in liver and pancreatic regeneration and proliferation. Using siRNA directed against beta-catenin, we demonstrated that REG3A is a target of beta-catenin signaling in Huh7 hepatoma cells. The upregulation of REG3A and REG1A expression is significantly correlated to the beta-catenin status in 42 HCC and 28 hepatoblastomas characterized for their beta-catenin status. Thus, we report strong evidence that both genes are downstream targets of the Wnt pathway during liver tumorigenesis.
Assuntos
Antígenos de Neoplasias/genética , Biomarcadores Tumorais/genética , Carcinoma Hepatocelular/genética , Regulação Neoplásica da Expressão Gênica , Lectinas Tipo C/genética , Litostatina/genética , Neoplasias Hepáticas/genética , Mutação , beta Catenina/genética , Adenoma/genética , Adulto , Linhagem Celular Tumoral , Neoplasias do Colo/genética , Hepatoblastoma/genética , Humanos , Masculino , Proteínas Associadas a Pancreatite , Transdução de SinaisRESUMO
Numerical simulations of layered, sulphide-bearing unsaturated waste rock piles are presented to illustrate the effect of coupled processes on the generation of acid mine drainage (AMD). The conceptual 2D systems were simulated using the HYDRUS model for flow and the POLYMIN model for reactive transport. The simulations generated low-pH AMD which was buffered by sequential mineral dissolution and precipitation. Sulphide oxidation rates throughout the pile varied by about two orders of magnitude (0.004-0.4 kg m-3 year-1) due to small changes in moisture content and grain size. In the fine-grained layers, the high reactive surface area induced high oxidation rates, even though capillary forces kept the local moisture content relatively high. In waste rock piles with horizontal layers, most of the acidity discharged through vertical preferential flow channels while with inclined fine grained layers, capillary diversion channeled the AMD to the outer slope boundary, keeping the pile interior relatively dry. The simulation approach will be useful for helping evaluate design strategies for controlling AMD from waste rock.