Solvent Effects on the Selectivity of Palladium-Catalyzed Suzuki-Miyaura Couplings

The use of polar solvents MeCN or dimethylformamide (DMF) was previously shown to induce a selectivity switch in the Pd/P^tBu₃-catalyzed Suzuki-Miyaura coupling of chloroaryl triflates. This phenomenon was attributed to the ability of polar solvents to stabilize anionic transition states for oxidative addition. However, we demonstrate that selectivity in this reaction does not trend with solvent dielectic constant. Unlike MeCN and DMF, water, alcohols, and several polar aprotic solvents such as MeNO₂, acetone, and propylene carbonate provide the same selectivity as nonpolar solvents. These results indicate that the role of solvent on the selectivity of Suzuki-Miyaura couplings may be more complex than previously envisioned. Furthermore, this observation has the potential for synthetic value as it greatly broadens the scope of solvents that can be used for chloride-selective cross coupling of chloroaryl triflates.     

Survival and success of family‐owned small businesses after hurricane Katrina: Impact of disaster assistance and adaptive capacity

The study's purpose is to examine the relative importance of direct disaster assistance to family‐owned small firms on their survival and success while considering the components of their adaptive capacity after experiencing Hurricane Katrina. This study employed data from the 2013 and 2015 Small Business Survival and Demise after a Natural Disaster Project (SBSD), a project funded by the National Science Foundation. The logistic regression results show that family businesses with SBA loans (or loan guarantees) were significantly more likely to survive. In addition, family businesses where household and family issues were more frequently in conflict with work demands were more likely to survive. On the other hand, the OLS regression results indicate that family businesses with more stress and more family–business conflict were less likely to succeed.     

Development and Psychometric Testing of the Rate and Accumulation Concept Inventory

Background

Because a fundamental understanding of rate and accumulation principles is important for engineering students across all subdisciplines, a method is needed to assess their understanding of these principles.

Purpose/Hypothesis

This article discusses the development of the Rate and Accumulation Concept Inventory (RACI) instrument and provides an analysis of its validity and reliability. The RACI is designed to test students’ (1) overall mastery of rate and accumulation concepts and (2) mastery of specific rate and accumulation concepts (e.g., mathematics, mass flow, and heat flow).

Design/Methods

Exploratory findings of students’ conceptual understanding prompted the development of a preliminary RACI instrument. Two pilot studies were conducted, with adjustments made to the instrument between each. Data from the second pilot were used to assess evidence of validity and reliability through classical test theory, item response theory, and structural equation modeling.

Results

Validity and reliability evidence indicates that the RACI can be used to measure students’ overall understanding of the concepts identified, though several items require revision or removal. Issues of potential construct underrepresentation were found in two of the conceptual categories.

Conclusions

The evidence of reliability and validity indicates the appropriateness of the RACI for assessing engineering students’ overall understanding of rate and accumulation principles. Additional research is needed to further enhance the validity and reliability of the RACI as a diagnostic tool, particularly in measuring students’ understanding of rate and accumulation concepts in particular physical contexts.     

Personalized Hydrogels for Engineering Diverse Fully Autologous Tissue Implants

Despite incremental improvements in the field of tissue engineering, no technology is currently available for producing completely autologous implants where both the cells and the scaffolding material are generated from the patient, and thus do not provoke an immune response that may lead to implant rejection. Here, a new approach is introduced to efficiently engineer any tissue type, which its differentiation cues are known, from one small tissue biopsy. Pieces of omental tissues are extracted from patients and, while the cells are reprogrammed to become induced pluripotent stem cells, the extracellular matrix is processed into an immunologically matching, thermoresponsive hydrogel. Efficient cell differentiation within a large 3D hydrogel is reported, and, as a proof of concept, the generation of functional cardiac, cortical, spinal cord, and adipogenic tissue implants is demonstrated. This versatile bioengineering approach may assist to regenerate any tissue and organ with a minimal risk for immune rejection.     

Chronic pain is underestimated and undertreated in dialysis patients: A retrospective case study

Significant chronic pain is highly prevalent in chronic kidney disease patients and is associated with morbidity and mortality. In this study, we retrospectively evaluated the incidence and treatment of pain in the dialysis unit of our tertiary referral center. The cohort included 147 patients. Over 66% reported significant (VAS >40) chronic pain during the preceding 3 months, most often characterized as stabbing (38%) and with concurrent itching (44%). Only 33% of patients received chronic pain medications, while 55.6% of patients with severe pain and 45.9% with pain characterized as the worst imaginable did not receive any analgesics. Pregabalin or weak opioids were the most frequently used. In conclusion, chronic pain is highly prevalent and markedly undertreated in dialysis patients, despite its significant adverse impact.     

坦德鲁姆步行桥 澳大利亚墨尔本

正连接比拉容马尔公园(Birrarung Marr)和墨尔本公园体育区的新坦德鲁姆人行天桥,为墨尔本公园建造了一个新的主要到达途径。澳大利亚网球公开赛期间,这座桥是一个主要行人入口。一条经过比拉容马尔公园坡道通向大桥,坡道的布置与已建桥梁和公园景观地形相得益彰。在我们的设计中,我们把"演讲角"的历史景观同横跨"蝙蝠侠大道"的墨尔本公园的网球场连接起     

In-Silico Identified New Natural Sortase A Inhibitors Disrupt S. aureus Biofilm Formation

Sortase A (SrtA) is a membrane-associated enzyme that anchors surface-exposed proteins to the cell wall envelope of Gram-positive bacteria such as Staphylococcus aureus. As SrtA is essential for Gram-positive bacterial pathogenesis but dispensable for microbial growth or viability, SrtA is considered a favorable target for the enhancement of novel anti-infective drugs that aim to interfere with key bacterial virulence mechanisms, such as biofilm formation, without developing drug resistance. Here, we used virtual screening to search an in-house natural compound library and identified two natural compounds, N1287 (Skyrin) and N2576 ((4,5-dichloro-1H-pyrrol-2-yl)-[2,4-dihydroxy-3-(4-methyl-pentyl)-phenyl]-methanone) that inhibited the enzymatic activity of SrtA. These compounds also significantly reduced the growth of S. aureus but possessed moderate mammalian toxicity. Furthermore, S. aureus strains treated with these compounds exhibited reduction in adherence to host fibrinogen, as well as biofilm formation. Hence, these compounds may represent an anti-infective therapy without the side effects of antibiotics.     

Enhanced Fluorescence for Bioassembly by Environment‐Switching Doping of Metal Ions

The self‐assembly of cyclodipeptides composed of natural aromatic amino acids into supramolecular structures of diverse morphologies with intrinsic emissions in the visible light region is demonstrated. The assembly process can be halted at the initial oligomerization by coordination with zinc ions, with the most prominent effect observed for cyclo‐dihistidine (cyclo‐HH). This process is mediated by attracting and pulling of the metal ions from the solvent into the peptide environment, rather than by direct interaction in the solvent as commonly accepted, thus forming an “environment‐switching” doping mechanism. The doping induces a change of cyclo‐HH molecular configurations and leads to the formation of pseudo “core/shell” clusters, comprising peptides and zinc ions organized in ordered conformations partially surrounded by relatively amorphous layers, thus significantly enhancing the emissions and allowing the application of the assemblies for ecofriendly color‐converted light emitting diodes. These findings shed light into the very initial coordination procedure and elucidate an alternative mechanism of metal ions doping on biomolecules, thus presenting a promising avenue for integration of the bioorganic world and the optoelectronic field.