1,720,966 research outputs found
Beach-cast brown seaweed (Ascophyllum nodosum) for the extraction of bioactive compounds and production of hydrochar using subcritical water as a green solvent
No full textBeach-cast brown seaweeds are a rich source of potential bioproducts but are currently either left to degrade on coastlines or harvested and discarded in landfills, becoming an environmental burden and resulting in underutilized biomass. This thesis explores the valorization of beach-cast seaweed using hydrothermal processing. A common brown seaweed, Ascophyllum nodosum, abundant along the North Atlantic seashores, is used to investigate lower temperature hydrothermal processing, subcritical water (SCW) extraction as an effective process to produce bioactive compounds (i.e., alginate, fucoidan, phenolics, and carotenoids) in liquid product while simultaneously producing a valuable solid by-product (hydrochar).
A comprehensive literature review identified knowledge gaps in bioactive compound extraction and challenges in scaling SCW processing, guiding the subsequent experimental investigations. The beach-cast A. nodosum was extracted using an Accelerated Solvent Extractor (ASE) under high-pressure SCW conditions (100–200 °C and 100 bar) to evaluate its valorization potential. Experimental design, kinetic studies, and rate modeling identified temperature as the most critical parameter impacting the ASE process. The key bioactive compounds (crude alginate, crude fucoidan, and antioxidant-rich crude extract) and nutrients (minerals and vitamins) exhibited comparable yields and qualities to those reported from fresh seaweeds, demonstrating the feasibility of using beach-cast seaweed as a sustainable feedstock.
The scalability of SCW was studied using a 600 mL bench-scale pressurized reactor under low-pressure SCW conditions (100–240 °C, 1–33 bar). A screening factorial design (SFD) and central composite design (CCD) were used to study the effects of final temperature, hold time at that final temperature, water-to-biomass ratio, water pH, and agitation speed. Final temperature and hold time were identified as the most significant parameters impacting yields and qualities of bioactive compounds and hydrochar.
A key challenge identified in the SCW scale-up is the variability in heating times across reactors, which complicates process optimization and control. To address this, the severity factor (log Ro) was evaluated as a single parameter (0.59–5.10) to integrate final temperature (100–240 °C), heating time (31–99 min), and hold time (0–24 min) for beach-cast A. nodosum valorization. The results demonstrated that the SCW process could recover crude alginate (15.75 dry wt% at log Rₒ = 1.99), crude fucoidan (39.94 dry wt% at log Rₒ = 2.39), antioxidant-rich crude extract (53.84–55.07 dry wt% at log Rₒ = 3.18–3.22), and hydrochar (29.53 dry wt% at log Rₒ = 3.79) at the maximum yields and/or qualities. Characterization of solid and liquid products revealed potential applications across biofuels, animal feeds, diet supplements, cosmetics, and natural antioxidant ingredients.
This thesis establishes a holistic framework for the sustainable valorization of beach-cast seaweeds. By demonstrating the conversion of “waste” A. nodosum into multiple high-value products, the research contributes to regional sustainability, supports zero-waste concepts, and provides practical design tools (i.e., severity factor) for guiding future SCW scale-up and industrial application
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Thermochemical modeling of a hydrolysis moving bed reactor in the Cu-Cl cycle of hydrogen production
No full textThis study focuses on simulating the hydrolysis step of the Copper-Chlorine (Cu-Cl) Cycle in a moving bed reactor (MBR). The
hydrolysis reaction is one of three reactions in the Cu-Cl cycle for hydrogen production. Several recent studies have highlighted
fluidized bed reactors as a promising reactor for this reaction, with lab scale studies ongoing. However, a potential alternative
reactor system, to decrease associated costs and energy requirements of high steam to copper ratios, is an MBR. Alternative
heterogeneous MBRs have been successful in reducing steam requirements in steam gasification of coal and biomass. These
operations demonstrate comparable reaction models to the hydrolysis reaction, which indicate the potential of moving bed reactors
as an attractive alternative for the process. Simulation of MBRs can be used as a tool to establish the feasibility and design of a lab
scale and scaled up MBR, however, there are no current models for this reaction system. This reactor model uses the Shrinking
Core Model (SCM) for heterogenous reactions, reaction kinetics, and mass and energy balances, to represent the system. The
resulting simulation is first validated by established reaction system / data and then applied to the Cu-Cl system. The model is then
used to investigate whether a series of MBRs could improve the steam to copper ratio and conversion of the hydrolysis reaction, as
well as the overall cycle efficiency
Feasibility study on hydrothermal carbonization of shrimp shell waste: emphasis on hydrochar characterization and chitin retention
No full textThe Canadian shrimp processing industry generates substantial quantities of shell waste
rich in chitin—a valuable biopolymer with broad applications, from biomedicine to environmental
remediation. However, the high moisture content and rapid degradation of shrimp shell waste
present challenges for efficient chitin extraction. This thesis investigates hydrothermal
carbonization (HTC) as a sustainable pre-treatment method to stabilize shrimp shell biomass,
enhance chitin isolation, and produce a versatile carbon-rich hydrochar by-product. HTC, effective
for processing high-moisture biomass, offers an energy-efficient alternative to conventional drying
and chemical treatments (e.g., hydrochloric acid and sodium hydroxide), providing a scalable
solution for sustainable waste management.
In this study, the effects of varying HTC conditions—including temperature, residence time,
and water-to-biomass ratios—on shrimp shell hydrochar yield and characteristics were
systematically examined. Detailed analyses, including surface area, ash content, pH, mineral
composition, and functional group identification via FTIR, were conducted to assess the potential
of HTC-treated hydrochar as an intermediate product for chitin extraction. Results indicate that
optimized HTC conditions reduce organic impurities while retaining key structural properties of
chitin, effectively streamlining its isolation. Furthermore, the residual hydrochar exhibits
properties suitable for environmental applications, including potential uses as a bioadsorbent and
soil amendment.
This work offers a dual-benefit approach for the seafood industry, addressing waste
stabilization and enhancing chitin recovery through HTC pre-treatment. Future research should
focus on refining HTC parameters to maximize chitin purity and yield, investigating additional
post-HTC purification steps, and exploring the functional performance of HTC-derived hydrochar
in specific environmental applications, such as heavy metal adsorption and soil nutrient
enhancement. These efforts will contribute to establishing a more comprehensive and sustainable
waste valorization pathway, advancing circular economy principles within the seafood industry.Includes bibliographical reference
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Understanding the microbial corrosion from the first principle at the atomistic scale
No full textThe corrosion of the metals (Fe, Ni, and Zn) is influenced by various factors, such as the presence
of microbes on the surface, type of surface, and environmental conditions; however, the
mechanisms controlling this impact are poorly understood. The corrosion-causing components can
be sulfur, hydrogen, H₂S and SO₄ over the metal surfaces. The propagation of the corrosion could
be minimized either by allying or applying inhibitors on the surface. A molecular modeling
approach using Density Functional Theory (DFT) could be a useful tool to understand such a
complex transformation occurring in the environment. Microbes can eliminate protons from the
biofilm or consume electrons from the metal surface. This electron removal activity is modeled as
an electric field. A positive/negative electric field is proposed for electron donation/acceptance to
mimic the microbes over the surface. The change in adsorption energy due to the electric field for
the corrosive species and inhibitors is studied in this thesis.
It has been observed that the adsorption energy of the sulfur, hydrogen, and SO₄, on the Fe (110),
Fe (100), and Fe (310) surfaces increased with the application of the electric field irrespective of
the direction (negative/ positive) of the electric field. The H₂S, spontaneously dissociates over the
Fe (100) surface. The molecular form of the H₂S is weakly adsorbed on the Fe (100) surface;
however, the sulfur and hydrogen are strongly adsorbed over the iron surface. The addition of an
allying element (Cr) improves the corrosion-resistant property of the iron. Furthermore, the
hydrogen atom can diffuse into the sublayer of iron; however, doping the Cr atom into iron
increases the diffusion barrier. This study shows that hydrogen diffusion into to sublayer of iron
follows a tortuous path.
The propagation of the corrosion could be explained by the thermochemical stability of the
material. The Pourbaix diagram for the metals Zn, Ni, and alloy Zn-Ni are drawn utilizing Gibbs
free energy of formation (ΔƒG). The Porbaix diagram for the Zn₁₁Ni₂,ZnNi and ZnNi₃ are
compared and discussed. It was found that for the corrosion of the Zn-rich alloy, ZnNi, has a
bigger area for the phase Ni²⁺,Zn²⁺, than Zn₁₁Ni₂: however, for corrosion of Ni-rich alloy ZnNi₃
has a bigger area for phase Ni²⁺,Zn²⁺ than Zn₁₁Ni₂.
The adsorption of corrosion inhibitors, Sulfacetamide (SFC), Sulfamerazine (SFM),
Sulfapyridine (SFP), and Sulfathiazole (SFT) increases with the application of electric field, which
implies these inhibitors could be used for protection against microbial corrosion.
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The present study is valid for static conditions, however molecular dynamics could be applied to
understand microbial corrosion at atomic scale. The adsorption energy of various species and
Pourbaix diagram of metal/alloys are calculated at standard conditions. The present study did not
discuss the corrosion due to multispecies, however most of the corrosion occurs in presence of
multi species.Includes bibliographical reference
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
The potential of biofuels in Newfoundland and Labrador's economy: a transdisciplinary case study of Corner Brook pulp and paper (cbppl)
No full textThis study explores the potential of biofuels to support sustainable energy transition in Newfoundland and Labrador (NL), using Corner Brook Pulp and Paper Limited (CBPPL) as a transdisciplinary case study. In response to the province's continued reliance on fossil fuels and its commitment to net-zero emissions, the research examines how locally produced biofuels derived from forestry by-products can phaseout fossil fuels in NL and offer environmental, economic, and social benefits.
Using a mixed-methods approach, I employed Life Cycle Assessment (LCA) to evaluate the environmental performance of four biofuels, biodiesel, bio-oil, syngas, and pellets, while Net Present Value (NPV) analysis is used to determine their economic feasibility. Social acceptability and community perspectives are explored through semi-structured interviews with stakeholders in the region.
Results show that all four biofuels offer environmental benefits when compared to the fossil fuels currently used in the province. However, each biofuel presents different trade-offs. While some exhibit strong economic performance, others are more socially or environmentally favorable. Among them, biodiesel emerged as the most balanced option, offering consistent advantages across environmental, economic, and social dimensions. I conclude that while no single biofuel is universally optimal in all contexts, biodiesel stands out as the most promising candidate in aligning with the principles of sustainable development.
This research offers practical insights for policymakers, industry stakeholders, and researchers by identifying viable biofuel pathways for the province. It also demonstrates the value of collaborative, transdisciplinary research in addressing complex energy and sustainability challenges
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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