Dow Chemical (Canada)

A comprehensive analysis of the bioaccumulation of three cyclic (namely, D4, D5, and D6) and five linear (namely, L2, L3, L4, L5, and L6) volatile methylsiloxanes (VMS) in biota was conducted by reviewing 50 published articles and laboratory reports on aquatic (82%) and terrestrial species (18%). A total of 178 bioaccumulation values were evaluated employing a quantitative weight-of-evidence (qWoE) approach provided by the Bioaccumulation Assessment Tool. Considerable variability of bioconcentration factor (BCF) and bioaccumulation factor (BAF) values was observed for VMS in aquatic organisms, which ranged from below to above their respective regulatory threshold values. The frequency of evidence for non-bioaccumulation (ie, BCF or BAF <2000) was ≥50% for D6, L2, L5, and L6. Conversely, laboratory biomagnification factor (BMF) values were generally (≥71%) less than 1, indicating low bioaccumulation potential through dietary uptake. Field BMFs displayed more variability but still suggested a low bioaccumulation potential. Despite the majority (≥65%) of trophic magnification factors (TMFs) in aquatic food webs being below 1, the broad range of TMF values for all VMS examined indicates potential uncertainties introduced by environmental factors in the target environments (e.g., chemical exposure gradient) and sampling bias. Overall, lines of evidence (≥71%) suggest that cyclic and linear VMS generally do not bioaccumulate in aquatic species, with dietary uptake being the primary pathway. For terrestrial species, primarily rats, predicted and field BMFs were less than 1 at 37 °C, primarily via respiratory elimination. Field TMFs for terrestrial food webs, including invertebrates and various bird species with body temperatures of 18 and 40 °C, respectively, were sourced from a single study, where D4 demonstrated trophic dilution, while D5 and D6 generally did not biomagnify in this terrestrial food web.

Otophysans, known for their enhanced hearing enabled by the complex Weberian apparatus, comprise two-thirds of extant freshwater fish species. Previously, they were thought to have originated in fresh water before the breakup of Pangea, implying a nearly 80-million-year gap between the origin and oldest known fossil. However, the discovery of a Late Cretaceous freshwater otophysan challenges this view. Integrating fossil, morphological, and genomic data, we estimate a younger crown group origin of ~154 million years ago. Notably, ancestral range and habitat reconstructions indicate marine origins for the otophysan crown groups, with at least two transitions to fresh water. Functional simulations of the Weberian ossicles of this fossil suggest that the distinctive hearing capabilities of otophysans evolved in conjunction with fusion of hearing ossicle parts and freshwater adaptations.

Baseline surveys serve as a foundational instrument in monitoring and evaluation, significantly enhancing the performance and impact of education projects in refugee camps by providing critical benchmarks for planning, implementation, and assessment. This study examined the influence of baseline surveys in monitoring and evaluation (M&amp;E) on the performance of education projects in refugee camps in Turkana County, Kenya. Guided by international frameworks such as the Convention on the Rights of the Child, Sustainable Development Goal 4, and the 2018 Global Compact on Refugees, the research focused on education initiatives implemented by Windle International Kenya in partnership with the United Nations High Commissioner for Refugees (UNHCR). A census approach was employed, targeting a study population of 141 education stakeholders: 7 principals, 5 head teachers, 72 Board of Management members, 5 M&amp;E officers, 1 County Quality Assurance and Standards Officer (QASO), 1 Sub-County QASO, 15 education officers, 15 project coordinators, 15 finance officers, and 5 program managers. These education stakeholders were selected due to their central roles in the planning, execution, and oversight of education projects, ensuring that the study captured informed perspectives on the influence of baseline surveys within the project context. Data were collected through structured questionnaires and key informant interviews and analysed using descriptive and inferential statistics, including correlation and regression analysis. Qualitative findings from interviews further contextualised the quantitative results. The results indicate a positive and statistically significant relationship between the use of baseline surveys in M&amp;E and the performance of education projects in refugee camps (r = 0.680, p &lt; 0.05; β = 0.172, p = 0.020). Respondents reported that comprehensive baseline surveys contribute to setting project targets, tracking progress, guiding resource allocation, and enhancing stakeholder engagement. Thematic analysis of qualitative responses highlighted the importance of financial support, community sensitisation, and improved security as key factors for project success and teacher retention. The study concludes that baseline surveys are integral to effective M&amp;E, serving as benchmarks for planning, resource allocation, and project evaluation, ultimately improving educational outcomes for refugees. This research recommends that education project implementers prioritise baseline survey practices, ensure stakeholder involvement, invest in staff training, and integrate baseline surveys within standard M&amp;E frameworks to enhance the project's success and performance in refugee settings.

The mechanism by which PdII precursors are reduced to catalytically active low-valent Pd species has been a subject of interest for developing better catalysts. This process is well understood for catalytic systems employing a combination of palladium(ii) acetate [Pd(OAc)2] and tertiary phosphines. However, the mechanism of reduction of palladium(ii) acetylacetonate [Pd(acac)2] in the presence of phosphines has not been thoroughly investigated. This is especially important in the context of the Pd-catalyzed butadiene telomerization process, which uses a combination of Pd(acac)2 and tertiary phosphines in methanol to produce the commercially valuable precursor 1-methoxyoctadiene (MOD-1). In this work, we elucidate the steps for generating the active Pd0 species for this reaction using a combination of Pd(acac)2 and triphenylphosphine (PPh3). The investigations presented in this study provide the following key insights: (a) unification of the steps involved in the generation of the active precatalyst [PdII(acac)(PPh3)2]+; (b) elucidation of the mechanism of reduction of the precatalyst to Pd0 without MOD-1, which parallels the chemistry of the Pd(OAc)2/PPh3 system; and (c) the generation of PdII-octadienyl species from the reaction between the precatalyst and MOD-1, the product of the telomerization reaction. A reversible C-O bond cleavage process was identified that leads to the formation of the PdII π-octadienyl species as the active catalyst in the commercial telomerization process. These studies provide important insights into the reduction of Pd(acac)2 into active Pd0 species or PdII π-allyl species, which have wide implications for both cross-coupling catalysis as well as the telomerization reaction.

Objectives: This study aimed to evaluate the efficacy and postoperative complications of preoperative submucosal dexamethasone injection compared to preoperative dexamethasone injection into the pterygomandibular space for surgical extraction of the impacted lower third molar. Study design and setting: This was a quasi-experimental, cross-sectional study conducted at the Department of Oral and Maxillofacial Surgery, Dow International Dental College, Dow University of Health Sciences, Karachi, from April to July 2021. Methodology: The study sample consisted of 72 patients who reported surgical extraction of their lower wisdom teeth and consented to participate in this study. The patients were randomly divided into the submucosal injection group (SM) and the pterygomandibular space (PM) group. The injection time was recorded on the second and seventh postoperative days. Results: No significant differences in the duration of the intervention were observed between the two groups (23.08 min in PM, 23.07 min in SM). The postoperative facial swelling was significantly reduced transversely (ear lobe to the angle of the mouth) in both groups compared to their respective baselines on the first postoperative day. On the secondpostoperative day, significant changes were observed in the submucosal group in postoperative swelling. Conclusions: Using intraoral dexamethasone injections in third molar surgery significantly reduces conventional complications of surgery while avoiding the systemic side effects of steroids. Dexamethasone should be used regardless of the administration site when warranted, with less apprehension than is common in dentistry

Objective: To identify the sources of learning gaps in biochemistry teaching and learning and explore new teaching and learning strategies, considering the students' perceptions and felt needs. Study Design: Exploratory qualitative study (Social-constructivist philosophical worldview). Place and Duration of Study: Public Sector Medical College, Pakistan, from Jul 2020 to Jul 2021. Methodology: Students from all five years of medical college were recruited voluntarily after their written consent. Ten focus group discussions were conducted, each consisting of approximately 8 to 12 participants. Each session was recorded and then later transcribed verbatim. Verbatim FGDs were reviewed, and codes were given as the concept became recognizable. A code structure was developed via an inductive approach, and then sub-themes and themes were generated. Results: Ten major themes were generated from the FGDs. These themes were teaching, students’ motivation, clinical irrelevance, educational needs, transition difficulty, attitudes, student support, senior peers, curriculum coherence, and assessment. These themes were further elucidated to explain the causes of the learning gaps and provide suggestions. Conclusion: This study concludes that teaching, students’ motivation, clinical irrelevance, educational needs, difficulty in transition, student attitude, student support, senior peers, curriculum coherence, and assessment are the potential sources of the learning gap to achieve intended learning outcomes of biochemistry for medical students.

To meet the accessibility needs of students who are blind or have low vision (BLV), detailed textual descriptions of STEM diagrams within interactive learning tools are cre-ated in real-time and correspond to the configurations of the interactive software system. The descriptions are read by screen readers as alternative (alt) text to provide infor-mation for BLV students to compose mental representa-tions of the diagram. These descriptions provide a unique bridge from the visual language of STEM diagrams to natural language of Large Language Models (LLMs). By interfacing with an LLM, these descriptions are used for personalized exploration by the BLV user and to guide all learners through a defined pedagogical pathway. Results from a usability study with four BLV adults are reported.

Abstract Esters reduce to form ethers and alcohols on contact with metal nanoparticles supported on Brønsted acidic faujasite (M‐FAU) that cleave C−O bonds by hydrogenation and hydrogenolysis pathways. Rates and selectivities for each pathway depend on the metal identity (M=Co, Ni, Cu, Ru, Rh, Pd, and Pt). Pt‐FAU gives propyl acetate consumption rates up to 100 times greater than other M‐FAU catalysts and provides an ethyl propyl ether selectivity of 34 %. Measured formation rates, kinetic isotope effects, and site titrations suggest that ester reduction involves a bifunctional mechanism that implicates the stepwise addition of H* atoms to the carbonyl to form hemiacetals on the metal sites, followed by hemiacetal diffusion to a nearby Brønsted acid site to dehydrate to ethers or decompose to alcohol and aldehyde. The rates of reduction of propyl acetate appear to be determined by the H* addition to the carbonyl and by the C−O cleavage of hemiacetal.

A reliable approach for the determination of volatile oxygenated compounds in high-pressure liquefied hydrocarbons with post-column reaction gas chromatography has been developed.