72 research outputs found
Conversion of cellulose to activated carbons for high-performance supercapacitors
Biomass-derived activated carbons are promising materials that can be used in various
applications. Current work investigates the possibilities of the cellulose-derived activated carbons
in substituting the commercial alternatives for the supercapacitors’ electrodes with high
efficiency, stable performance and relatively low cost. Hydrothermal carbonization (HTC)
followed by chemical activation with KOH is used to convert cellulose into highly porous
activated carbons. The effect of HTC parameters on the material porosity development and
electrochemical properties of the electrodes is evaluated with several variations of the residence
time and the weight ratio between cellulose and water during the pretreatment. The analysis
shows that intensification of the HTC process (longer residence time and higher water/cellulose
ratio) results in increase of the surface area of both hydrochar samples and subsequent activated
carbons: with the highest surface area for the sample produced after 2 h HTC treatment with
water/cellulose ratio of 6/1 – 2,645 m2 g
-1
. As for the electrochemical analysis, the highest values
of the specific capacitance are found for the samples produced from 2 h HTC treatment:
110.3 F g
-1
(water/cellulose ratio of 3/1) and 102.5 F g
-1
(water/cellulose ratio of 6/1).
Additionally, it is noted that electrodes produced from the samples treated during 4 h have higher
impedance at low operation frequency. The present study proves the possibility to substitute
commercial activated carbons with cellulose-derived materials, the porosity of which can be
tuned accordingly already during the pretreatment step
Use of principal component analysis to evaluate thermal properties and combustibility of coffee-pine wood briquettes
Submitted: February 1st, 2021 ; Accepted: March 30th, 2021 ; Published: May 21st, 2021 ; Correspondence: [email protected] coffee production chain is a potential source of residual biomass inherent to the
high productivity that can contribute to the generation of value-added products. The residues from
the coffee sector are typically disposed to landfill without treatment causing potential
environmental inconveniences. Briquetting presents an alternative process to produce a uniform
fuel with high energy density. Briquettes facilitates easy transportation, enables better handling
and storage of biomass residues. Properties such as low equilibrium moisture content, high energy
density and compressive strength were reported for different coffee-pine wood briquettes
treatments. Moreover, understanding of the thermal properties of the briquettes during
combustion is crucial to evaluate their final application. This research is the first study that
investigates the combustibility properties and kinetic parameters of the thermal decomposition of
briquettes from coffee-pine wood using differential and integral thermal analysis under
non-isothermal conditions. Multivariate analysis of the collected parameters through principal
components analysis (PCA), was implemented to reduce the dimensionality of the data.
The desired profile in the combustibility is directly related to high temperatures and long burning
times, thus, the tested briquettes displayed a significant combustibility potential, reporting peak
temperatures and burnout times around 600 °C and 27 minutes, respectively. Activation energy
kinetic parameter in the range of 12–42 kJ mol-1
and average reactivity of 0.14–0.22 min-1
, were
also found. The results revealed the not thermally hard material to degrade when compared to
biomasses typically used for combustion
2D dynamic mesh model for deposit shape prediction in boiler bank of recovery boiler with different tube spacing arrangements
Paper presented to the 10th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Florida, 14-16 July 2014.CFD tools are essential in the design and operation of
boilers. One particular aspect that can be modelled by CFD is
the deposition and plugging in heat transfer surfaces of boilers.
Fouling and slagging are the most typical causes of
unscheduled boiler shutdowns. This is why appropriate
predictions of deposition geometries and rates are of high
interest. Among other applications, CFD Multiphase
approaches are capable of modelling particle-laden streams.
However, the relatively large number of models to select, each
one with its own properties, typical applications, benefits and
drawbacks- creates difficulties when trying to determine which
model to use at first approach.
The problem that we are going to tackle is of a really
complicated and multidisciplinary nature (thermo-fluid
mechanics, sticking/rebounding of particles, sintering, among
others). Dynamic mesh capabilities in commercial CFD
software packages are able to modify the interphase fluiddeposit
according to the growth rate, assuming it has been
accurately calculated by a convenient multiphase model for
particle-laden flows. In this work, such a CFD model for
prediction of deposition shapes in a classical boiler bank of a
Kraft Recovery Boiler will be developed and presented. The
effect of tube transversal spacing will also be analyzeddc201
Response of macroinvertebrates to experimental nutrient and fish additions in European localities at different latitudes
The sedimentary and plant-associated macroinvertebrate communities have been examined in a series of mesocosm experiments carried out in five locations, in Finland, Sweden, UK, Northwest Spain and Mediterranean Spain (the International Mesocosm Experiment). The experiments were designed to investigate how shallow lake ecosystems respond to the addition of nutrients and planktivorous fish along a climate gradient. Nutrient additions increased sedimentary benthos densities and total biomass to a plateau at intermediate levels of nutrients. The effect was greater in the warmest localities. Beyond the saturation point a further increase in nutrient loading had different effects depending on locality. Only in the southernmost site (in Mediterranean Spain), did it induce a shift to a turbid phase and macrophyte disappearance. Thus there are breakpoints in the relationship with nutrients, leading to alternative sediment communities subsequent to the water alternative states. Presence of fish increased the densities and biomass of sediment macroinvertebrates, more clearly in the more southern locality, where the fish Gambusia did not prey in the bottom animals. A stabilising role of macrophytes was observed by cutting them, samples taken three weeks after cutting indicated a higher effect of fish on the sediment community when macrophytes were not present. Nutrients tended also to increase densities of plant associated macroinvertebrates at low levels with a flattening of response at intermediate levels and a decline at high levels. At high fish level the numbers and biomass of plant-associated macroinvertebrates were lowered in all cases, because of increased predation. However fish addition at low level in most cases had the opposite effect, because their predation pressure was not high and regeneration of nutrients through their activities might increase food availability and control invertebrate predators. Fish influenced especially community composition, because they prey selectively. Addition of fish at low densities increased macroinvertebrate diversity. A diel migratory cycle was observed in plant-associated macroinvertebrates, but only in the southerly locations. Latitudinal influences on the structure of the macroinvertebrate communities occur but that they operate indirectly. There was a prominent effect of nutrients on these communities so that starting trophy is very important. Fish effects are layered on these and depend to a large extent on the particular range of diet of the species involved.Se ha estudiado la comunidad de macroinvertebrados bentónicos del sedimento asà como la de los asociados a los macrófitos en una serie de mesocosmos concebidos para un experimento múltiple simultáneo llevado a cabo en cinco localidades europeas: Finlandia, Suecia, Reino Unido (UK), Noroeste de España y Levante Español. El experimento fue diseñado para investigar como responden los ecosistemas de lagos someros a los aportes de nutrientes y a la abundancia de peces planctÃvoros a lo largo de un gradiente climático. La adición de nutrientes incrementó la densidad del bentos del sedimento y su biomasa hasta estabilizarse a niveles intermedios de nutrientes, siendo este efecto mayor en las latitudes más bajas y cálidas. Más allá del punto de saturación, un aumento adicional de la carga de nutrientes tuvo efectos diferentes dependiendo de la localidad y solo en el lugar de menor latitud, (en el Levante Español) indujo el cambio hacia una fase turbia, con desaparición de los macrófitos, esto es, hay puntos de ruptura relacionados con la carga de nutrientes que conducen a comunidades alternativas en el sedimento, subsiguientes a los mencionados estados alternativos en las aguas someras. La presencia de peces aumentó la densidad y biomasa de los macroinvertebrados del sedimento, ello también más claramente en la localidad situada más al Sur, ya que el pez planctÃvoro ensayado (Gambusia) por lo general no depreda en los animales del sedimento. Se observó también el papel estabilizador de los macrófitos comparando las muestras tomadas antes y después de que estos fueran cortados, por ejemplo se observó un efecto mayor de los peces en las comunidades del sedimento cuando los macrófitos no estaban presentes. Los nutrientes tendieron también a incrementar las densidades de los macroinvertebrados asociados a los macrófitos cuando se aportan a bajos niveles, con una estabilización de la respuesta para los valores intermedios y un declive para los valores más altos. Cuando se adicionaron densidades altas de peces, el número y biomasa de los macroinvertebrados asociados a los macrófitos descendieron en todos los casos, como resultado del aumento de la depredación. Sin embargo, las adiciones a baja densidad de peces, en la mayorÃa de los casos, tuvo el efecto contrario, ya que su presión de depredación no es alta y pueden contribuir a la regeneración de los nutrientes a través de la vÃa detrÃtica que incrementa la disponibilidad de alimento, asà como al control de otros invertebrados depredadores. La presencia de peces influenció especialmente la composición de la comunidad, ya que su depredación es selectiva. La adición de peces en bajas densidades aumentó la diversidad de los macroinvertebrados. También fue observado que el ciclo diario de migración en los macroinvertebrados asociados a los macrófitos, es más importante en las localidades ubicadas en las latitudes de más al Sur. Las influencias latitudinales en la estructura de las comunidades de macroinvertebrados, si bien sucede, opera indirectamente. Hay un efecto dominante de los nutrientes en estas comunidades, y el nivel trófico de las condiciones iniciales es muy importante. Los efectos de los peces se subordinan al de los nutrientes y dependen en gran medida de la dieta de las especies involucradas
The Safety and Efficacy of Live Viral Vaccines in Patients With Cartilage-Hair Hypoplasia
Background: Live viral vaccines are generally contraindicated in patients with combined immunodeficiency including cartilage-hair hypoplasia (CHH); however, they may be tolerated in milder syndromes. We evaluated the safety and efficacy of live viral vaccines in patients with CHH.Methods: We analyzed hospital and immunization records of 104 patients with CHH and measured serum antibodies to measles, mumps, rubella, and varicella zoster virus (VZV) in all patients who agreed to blood sampling (n= 50). We conducted a clinical trial (identifier: NCT02383797) of live VZV vaccine on five subjects with CHH who lacked varicella history, had no clinical symptoms of immunodeficiency, and were seronegative for VZV; humoral and cellular immunologic responses were assessed post-immunization.Results: A large proportion of patients have been immunized with live viral vaccines, including measles-mumps-rubella (MMR) (n= 40, 38%) and VZV (n= 10, 10%) vaccines, with no serious adverse events. Of the 50 patients tested for antibodies, previous immunization has been documented with MMR (n= 22), rubella (n= 2) and measles (n= 1) vaccines. Patients with CHH demonstrated seropositivity rates of 96%/75%/91% to measles, mumps and rubella, respectively, measured at a medium of 24 years post-immunization. Clinical trial participants developed humoral and cellular responses to VZV vaccine. One trial participant developed post-immunization rash and knee swelling, both resolved without treatment.Conclusion: No serious adverse events have been recorded after immunization with live viral vaccines in Finnish patients with CHH. Patients generate humoral and cellular immune response to live viral vaccines. Immunization with live vaccines may be considered in selected CHH patients with no or clinically mild immunodeficiency
The human long non-coding RNA gene RMRP has pleiotropic effects and regulates cell-cycle progression at G2
RMRP was the first non-coding nuclear RNA gene implicated in a disease. Its mutations cause cartilage-hair hypoplasia (CHH), an autosomal recessive skeletal dysplasia with growth failure, immunodeficiency, and a high risk for malignancies. This study aimed to gain further insight into the role of RNA Component of Mitochondrial RNA Processing Endoribonuclease (RMRP) in cellular physiology and disease pathogenesis. We combined transcriptome analysis with single-cell analysis using fibroblasts from CHH patients and healthy controls. To directly assess cell cycle progression, we followed CHH fibroblasts by pulse-labeling and time-lapse microscopy. Transcriptome analysis identified 35 significantly upregulated and 130 downregulated genes in CHH fibroblasts. The downregulated genes were significantly connected to the cell cycle. Multiple other pathways, involving regulation of apoptosis, bone and cartilage formation, and lymphocyte function, were also affected, as well as PI3K-Akt signaling. Cell-cycle studies indicated that the CHH cells were delayed specifically in the passage from G2 phase to mitosis. Our findings expand the mechanistic understanding of CHH, indicate possible pathways for therapeutic intervention and add to the limited understanding of the functions of RMRP.Peer reviewe
Interactions between Predation and Resources Shape Zooplankton Population Dynamics
Identifying the relative importance of predation and resources in population dynamics has a long tradition in ecology, while interactions between them have been studied less intensively. In order to disentangle the effects of predation by juvenile fish, algal resource availability and their interactive effects on zooplankton population dynamics, we conducted an enclosure experiment where zooplankton were exposed to a gradient of predation of roach (Rutilus rutilus) at different algal concentrations. We show that zooplankton populations collapse under high predation pressure irrespective of resource availability, confirming that juvenile fish are able to severely reduce zooplankton prey when occurring in high densities. At lower predation pressure, however, the effect of predation depended on algal resource availability since high algal resource supply buffered against predation. Hence, we suggest that interactions between mass-hatching of fish, and the strong fluctuations in algal resources in spring have the potential to regulate zooplankton population dynamics. In a broader perspective, increasing spring temperatures due to global warming will most likely affect the timing of these processes and have consequences for the spring and summer zooplankton dynamics
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