Femtosecond‐laser micromachining (also known as inscription or writing) has been developed as one of the most efficient techniques for direct three‐dimensional microfabrication of transparent optical ...materials. In integrated photonics, by using direct writing of femtosecond/ultrafast laser pulses, optical waveguides can be produced in a wide variety of optical materials. With diverse parameters, the formed waveguides may possess different configurations. This paper focuses on crystalline dielectric materials, and is a review of the state‐of‐the‐art in the fabrication, characterization and applications of femtosecond‐laser micromachined waveguiding structures in optical crystals and ceramics. A brief outlook is presented by focusing on a few potential spotlights.
Femtosecond‐laser micromachining (also known as inscription or writing) has been developed as one of the most efficient techniques for direct three‐dimensional microfabrication of transparent optical materials. In integrated photonics, by using direct writing of femtosecond/ultrafast laser pulses, optical waveguides can be produced in a wide variety of optical materials. With diverse parameters, the formed waveguides may possess different configurations. This paper focuses on crystalline dielectric materials, and is a review of the state‐of‐the‐art in the fabrication, characterization and applications of femtosecond‐laser micromachined waveguiding structures in optical crystals and ceramics. A brief outlook is presented by focusing on a few potential spotlights.
Three dimensional printing technologies represent a revolution in the manufacturing sector because of their unique capabilities for increasing shape complexity while reducing waste material, capital ...cost and design for manufacturing. However, the application of 3D printing technologies for the fabrication of functional components or devices is still an almost unexplored field due to their elevated complexity from the materials and functional points of view. This paper focuses on reviewing previous studies devoted to developing 3D printing technologies for the fabrication of functional parts and devices for energy and environmental applications. The use of 3D printing technologies in these sectors is of special interest since the related devices usually involve expensive advanced materials such as ceramics or composites, which present strong limitations in shape and functionality when processed with classical manufacturing methods. Recent advances regarding the implementation of 3D printing for energy and environmental applications will bring competitive advantages in terms of performance, product flexibility and cost, which will drive a revolution in this sector.
Recent advances regarding the implementation of 3D printing for solid oxide fuel cells, batteries, solar energy and environmental applications are reviewed.
We report the simultaneous measurement of conductance and thermopower of highly conducting single-molecule junctions using a scanning tunneling microscope-based break-junction setup. We start with ...molecular backbones (alkanes and oligophenyls) terminated with trimethyltin end groups that cleave off in situ to create junctions where terminal carbons are covalently bonded to the Au electrodes. We apply a thermal gradient across these junctions and measure their conductance and thermopower. Because of the electronic properties of the highly conducting Au–C links, the thermoelectric properties and power factor are very high. Our results show that the molecular thermopower increases nonlinearly with the molecular length while conductance decreases exponentially with increasing molecular length. Density functional theory calculations show that a gateway state representing the Au–C covalent bond plays a key role in the conductance. With this as input, we analyze a series of simplified models and show that a tight-binding model that explicitly includes the gateway states and the molecular backbone states accurately captures the experimentally measured conductance and thermopower trends.
The application of the Anammox process has been usually focused on the treatment of wastewater with temperatures around 30
°C in order to operate under optimum conditions. In this work, the ...feasibility of the application of the Anammox process at lower temperatures has been tested. First, the short-term effects of temperature on the Anammox biomass were studied using batch tests. An activation energy of 63
kJ
mol
−1 was calculated and the maximum activity was found at 35–40
°C. Activity tests done at 45
°C showed an irreversible loss of the activity due to the biomass lysis.
A SBR was operated at different temperatures (from 30 to 15
°C) to determine the long-term effects. The system was successfully operated at 18
°C but when temperature was decreased to 15
°C, nitrite started to accumulate and the system lost its stability. Adaptation of biomass to low temperatures was observed when the specific activities obtained during first batch tests are compared to those obtained during the operation of the SBR.
Using the data taken at the Pierre Auger Observatory between December 2004 and December 2012, we have examined the implications of the distributions of depths of atmospheric shower maximum (X ...sub(max)), using a hybrid technique, for composition and hadronic interaction models. We do this by fitting the distributions with predictions from a variety of hadronic interaction models for variations in the composition of the primary cosmic rays and examining the quality of the fit. Regardless of what interaction model is assumed, we find that our data are not well described by a mix of protons and iron nuclei over most of the energy range. Acceptable fits can be obtained when intermediate masses are included, and when this is done consistent results for the proton and iron-nuclei contributions can be found using the available models. We observe a strong energy dependence of the resulting proton fractions, and find no support from any of the models for a significant contribution from iron nuclei. However, we also observe a significant disagreement between the models with respect to the relative contributions of the intermediate components.
The supernatant resulting from the anaerobic digestion of sludge generated by wastewater treatment plants (WWTP) is an attractive flow for technologies such as partial nitritation–anammox (CANON), ...nitrite shortcut (NSC) and struvite crystallization processes (SCP). The high concentration of N and P and its low flow rate facilitate the removal of nutrients under more favorable conditions than in the main water line. Despite their operational and economic benefits, the environmental burdens of these technologies also need to be assessed to prove their feasibility under a more holistic perspective.
The potential environmental implications of these technologies were assessed using life cycle assessment, first at pilot plant scale, later integrating them in a modeled full WWTP. Pilot plant results reported a much lower environmental impact for N removal technologies than SCP. Full-scale modeling, however, highlighted that the differences between technologies were not relevant once they are integrated in a WWTP. The impacts associated with the WWTP are slightly reduced in all categories except for eutrophication, where a substantial reduction was achieved using NSC, SCP, and especially when CANON and SCP were combined. This study emphasizes the need for assessing wastewater treatment technologies as part of a WWTP rather than as individual processes and the utility of modeling tools for doing so.
•LCA was used to compare different side-stream treatment technologies.•At pilot plant scale, N removal technologies had the lowest environmental impact.•If part of a full WWTP, P-crystallization technologies presented the lowest impact.•Eutrophication impacts were reduced significantly using side-stream technologies.•Global warming, acidification, and toxicity impacts were only marginally reduced.
One of the most powerful strategies for the preparation of nanotubes is based on the stacking of flat-shaped cyclic peptide components. This strategy allows precise control of the nanotube internal ...diameter, the external properties and, more recently, the structural characterisitics of the internal cavity. The recent advances in these technologies and the applications of the resulting materials are described.
Tuning the internal and external properties of self-assembling cyclic peptide nanotubes.
The Pierre Auger collaboration reports new results bearing on the composition of cosmic rays. The muon number of air showers, created by cosmic rays and measured by the collaboration, is intriguingly ...at odds with all theoretical models, posing a challenge to our current understanding of the mass composition of cosmic rays. We present the first hybrid measurement of the average muon number in air showers at ultrahigh energies, initiated by cosmic rays with zenith angles between 62degrees and 80degrees. The measurement is based on 174 hybrid events recorded simultaneously with the surface detector array and the fluorescence detector of the Pierre Auger Observatory. The muon number for each shower is derived by scaling a simulated reference profile of the lateral muon density distribution at the ground until it fits the data. A 10 super(19) eV shower with a zenith angle of 67degrees, which arrives at the surface detector array at an altitude of 1450 m above sea level, contains on average (2.68 + or - 0.04 + or - 0.48(sys)) x 10 super(7) muons with energies larger than 0.3 GeV. The logarithmic gain d ln N sub( mu )/d ln E of muons with increasing energy between 4 X 10 super(18) eV and 5 x 10 super(19) eV is measured to be (1.029 + or - 0.024 + or - 0.030(sys)).
The CANON (Completely Autotrophic Nitrogen removal Over Nitrite) process was successfully developed in an air pulsing reactor type SBR fed with the supernatant from an anaerobic sludge digester and ...operated at moderately low temperatures (18–24
°C). The SBR was started up as a nitrifying reactor, lowering progressively the dissolved oxygen concentration until reaching partial nitrification. Afterwards, an inoculation with sludge containing Anammox biomass was carried out. Nitrogen volumetric removal rates of 0.25
g
N
L
−1
d
−1 due to Anammox activity were measured 35
d after inoculation even though the inoculum constituted only 8% (w/w) of the biomass present in the reactor and it was poorly enriched in Anammox bacteria. The maximal nitrogen removal rate was of 0.45
g
N
L
−1
d
−1. By working at a dissolved oxygen concentration of 0.5
mg
L
−1 in the bulk liquid, nitrogen removal percentages up to 85% were achieved.
The reactor presented good biomass retention capacity allowing the accumulation of 4.5
g VSS L
−1. The biomass was composed by ammonia oxidizing bacteria (AOB) forming fluffy structures and granules with an average diameter of 1.6
mm. These granules were composed by Anammox bacteria located in internal anoxic layers surrounded by an external aerobic layer where AOB were placed.
PDF
