Formation of asymmetric belt-like aggregates from a bio-based surfactant derived from dehydroabietic acid

The morphology and physicochemical properties of ordered molecular aggregates are closely related to surfactant molecules. Herein, a rosin-based amine oxide surfactant containing a large hydrophobic group (abbreviated R-10-AO) was synthesized from dehydroabietic acid, which is an important derivative of rosin. Cryogenic transmission electron microscopy (cryo-TEM) images and small-angle X-ray scattering (SAXS) showed that at a concentration of ∼5 mM, R-10-AO molecules formed flexible nanobelts with a thickness of only 2-3 nm. The width of these nanobelts was 50-150 nm and the length was more than 1 μm. The formation of the stable nanobelts arose from the strong van der Waals forces of the bulky hydrophobic portions of R-10-AO in solution, facilitating the stability of the asymmetrical aggregates. Rheological tests showed that the formed nanobelts were thermodynamically stable. The entanglement of these nanobelts led to significant viscoelasticity of the solutions. The zero-shear viscosity (η₀) of the R-10-AO solution reached 10 Pa s at a concentration of 5 mM, which is much greater than that of most wormlike micellar solutions. This work provides the inspirations of preparing aggregates with novel properties using natural products.

Behavior of Smart Surfactants in Stabilizing pH-Responsive Emulsions

Newly structured pH-responsive smart surfactants (N⁺ -(n)-N, n=14, 16) from alkyl trimethylammonium bromides are reported. In neutral and alkaline media N⁺ -(n)-N behaves as a normal cationic surfactant and stabilizes conventional emulsions alone, as well as Pickering emulsions and oil-in-dispersion emulsions together with oppositely and similarly charged nanoparticles, respectively. In acidic media N⁺ -(n)-N becomes a hydrophilic Bola-type surfactant, N⁺ -(n)-NH⁺ , and is an inferior emulsifier either when used alone or together with charged nanoparticles, resulting in demulsification. N⁺ -(n)-NH⁺ returns to the aqueous phase alone or together with nanoparticles after demulsification without contaminating the oil phase, and the aqueous phase can be recycled when triggered by pH change. This protocol is a green process and leads to preparation of various temporarily stable emulsions which are often used in emulsion polymerization, heterogeneous catalysis, and oil transportation.

Transition between a Pickering Emulsion and an Oil-in-Dispersion Emulsion Costabilized by Alumina Nanoparticles and a Cationic Surfactant

The transition between a novel oil-in-dispersion emulsion and an oil-in-water (O/W) Pickering emulsion triggered by pH was achieved using alumina nanoparticles in combination with a cationic surfactant. In acidic and neutral aqueous media, positively charged particles and the surfactant both at very low concentrations costabilize an oil-in-dispersion emulsion with the surfactant adsorbed at droplet interfaces and particles dispersed in the aqueous phase between the droplets. In alkaline media, however, particles become negatively charged and are hydrophobized in situ by adsorption of the surfactant to become surface-active and stabilize an O/W Pickering emulsion. The transition between the two is also possible by lowering the pH. The transformation can be achieved several times in a mixture of 0.1 wt % nanoparticles and 0.01 mM surfactant. This transition is significant, since particles can be made to either adsorb at the oil-water interface, which is beneficial for applications like biphasic catalysis, or remain dispersed in the aqueous phase, which is favorable for their recovery and reuse.

Covalent Immobilization of L-Asparaginase and Optimization of Its Enzyme Reactor for Reducing Acrylamide Formation in a Heated Food Model System

Acrylamide is a potent carcinogen and neurotoxin that is mainly formed by the Maillard reaction of asparagine with starch at high temperatures. In this work, a food safety immobilization system for L-asparaginase (L-ASNase) consisting of food-grade agarose (Aga) spheres and N-hydroxysuccinimide esters was developed to decrease the formation of acrylamide in a fluid food model system. L-asparaginase was successfully immobilized with a maximum immobilization efficiency of 68.43%. The immobilized enzymes exhibited superior storage stability and reusability with 93.21 and 72.25% of the initial activity retained after six consecutive cycles and storage for 28 days, indicating its high industrial application potential. Meanwhile, a simplified mathematical model of the enzyme reactor was developed and verified with experiments, which demonstrated its auxiliary role in the design and optimization of reactors. In addition, simulated fluidized food components were continuously catalyzed in the designed packed bed reactor, achieving a reduction rate of nearly 89%.

Supramolecular Hydrogels with Chiral Nanofibril Structures Formed from β-Cyclodextrin and a Rosin-Based Amino Acid Surfactant

The rational combination of natural molecules is expected to provide new soft material building blocks. Herein, a rosin-based amino acid surfactant was synthesized using dehydroabietic acid and l-serine as the starting materials (denoted as R-6-Ser). Supramolecular hydrogels were formed when β-cyclodextrin (β-CD) was mixed with R-6-Ser at molar ratios of over 0.5:1 and above certain concentrations. The hydrogels were investigated using rheometry, small-angle X-ray scattering, CD spectroscopy, and cryo-transmission electron microscopy (cryo-TEM). The β-CD associated with the isopropyl benzyl group of the dehydroabietic acid unit in R-6-Ser and formed R-6-Ser@β-CD complexes. The complexes and R-6-Ser self-assembled to form elongated right-handed rigid fibers with a diameter of approximately 7-8 nm, which were responsible for the elasticity of the hydrogels. This work demonstrated the feasibility of preparing supramolecular hydrogels from a diterpenoid-based surfactant and β-CD and provides a new means of utilizing the secretions of pine trees.

An Investigation of the Relationship Between COMLEX-USA Licensure Examination Performance and State Licensing Board Disciplinary Actions

PURPOSE

Passing the Comprehensive Osteopathic Medical Licensing Examination of the United States (COMLEX-USA) serves as a licensing requirement, yet there is limited understanding between this high-stakes exam and performance outcomes. This study examined the relationship between COMLEX-USA scores and disciplinary actions received by osteopathic physicians.

METHOD

Data for osteopathic physicians (N = 26,383) who graduated from medical school between 2004 and 2013 were analyzed using multinomial logistic regression to assess the relationship between COMLEX-USA scores and placement into one of 3 disciplinary action categories relative to no action received, controlling for years in practice and gender.

RESULTS

Less than 1% of physicians in this study (n = 187) had a disciplinary action(s). Controlling for all COMLEX-USA levels, years in practice, and gender, higher Level 3 scores were associated with significant decreased odds for all action categories: revoked licensed (odds ratio [OR] = 0.51, 95% confidence interval [CI] 0.36, 0.72; P < .001), imposed limitations to practice (OR = 0.59, 95% CI 0.41, 0.84; P < .01), and other action imposed (OR = 0.48, 95% CI 0.33, 0.69; P < .001), relative to not receiving an action. In these same models, higher Level 2 Performance Evaluation Biomedical/Biomechanical Domain scores decreased the odds for an action that revoked a license (OR = 0.75, 95% CI 0.58, 0.98; P < .05) and imposed limitations to practice (OR = 0.64, 95% CI 0.49, 0.84; P < .001).

CONCLUSIONS

These findings provide evidence that the COMLEX-USA delivers useful information regarding the likelihood of a practitioner receiving state board disciplinary actions.

Association Between American Board of Surgery Initial Certification and Risk of Receiving Severe Disciplinary Actions Against Medical Licenses

Importance

Board certification is used as a marker of surgeon quality and professionalism. Although some research has linked certification in surgery to outcomes, more research is needed.

Objective

To measure associations between surgeons obtaining American Board of Surgery (ABS) certification and examination performance with receiving future severe disciplinary actions against their medical licenses.

Design, Setting, and Participants

Retrospective analysis of severe license action rates for surgeons who attempted ABS certification based on certification status and examination performance. Surgeons who attempted to become certified were classified as certified or failing to obtain certification. Additionally, groups were further categorized based on whether the surgeon had to repeat examinations and whether they ultimately passed. The study included surgeons who initially attempted certification between 1976 and 2017 (n = 44 290). Severe license actions from 1976 to 2018 were obtained from the Federation of State Medical Boards, and certification data were obtained from the ABS database. Data were analyzed between 1978 and 2008.

Main Outcomes and Measures

Severe license action rates were analyzed across certified surgeons and those failing to obtain certification, as well as across examination performance groups.

Results

The final dataset included 36 197 men (81.7%) and 8093 women (18.3%). The incidence of severe license actions was significantly greater for surgeons who attempted and failed to obtain certification (incidence rate per 1000 person-years = 2.49; 95% CI, 2.13-2.85) than surgeons who were certified (incidence rate per 1000 person years = 0.77; 95% CI, 0.71-0.83). Adjusting for sex and international medical graduate status, the risk of receiving a severe license action across time was also significantly greater for surgeons who failed to obtain certification. Surgeons who progressed further in the certification examination sequence and had fewer repeated examinations had a lower incidence and less risk over time of receiving severe license actions.

Conclusions and Relevance

Obtaining board certification was associated with a lower rate of receiving severe license actions from a state medical board. Passing examinations in the certification examination process on the first attempt was also associated with lower severe license action rates. This study provides supporting evidence that board certification is 1 marker of surgeon quality and professionalism.

Highly wet aqueous foams stabilized by an amphiphilic bio-based hydrogelator derived from dehydroabietic acid

Exploration of novel molecular aggregates that stabilize foam systems is helpful to optimize foam properties. Herein, solutions of a rosin-based low-molecular-weight hydrogelator, abbreviated as R-6-AO, were used to generate foams above the critical gelation temperature (Tgel). The foams with R-6-AO concentrations above the critical gelation concentration were very stable below Tgel. The high stability of the foams under such conditions was attributed to the self-assembly of nanoscale fibers of R-6-AO in the liquid films of the foams, leading to extremely slow drainage of water. The foams showed strong water retention and were classified as very wet foams. For example, the foams generated from 10 mM (0.44 wt%) R-6-AO solution subjected to a fast cooling process contained about 45 vol% trapped water after 2000 min. In comparison, the water volume fraction of a 10 mM sodium dodecyl sulfate (SDS) foam decreased from 20 vol% to 1 vol% within 18 min. Because the growth, elongation, and cross-linking of the assembled nanofibers in the liquid films were affected by the cooling process, the stability of these foams also depended on the initial preparation temperature. The present system reveals the importance of microstructures in regulating foam behavior and serves as a new type of condition-sensitive intelligent foam.

Widely Adaptable Oil-in-Water Gel Emulsions Stabilized by an Amphiphilic Hydrogelator Derived from Dehydroabietic Acid

A surfactant, R-6-AO, derived from dehydroabietic acid has been synthesized. It behaves as a highly efficient low-molecular-weight hydrogelator with an extremely low critical gelation concentration (CGC) of 0.18 wt % (4 mm). R-6-AO not only stabilizes oil-in-water (O/W) emulsions at concentrations above its critical micelle concentration (cmc) of 0.6 mm, but also forms gel emulsions at concentrations beyond the CGC with the oil volume fraction freely adjustable between 2 % and 95 %. Cryo-TEM images reveal that R-6-AO molecules self-assemble into left-handed helical fibers with cross-sectional diameters of about 10 nm in pure water, which can be turned to very stable hydrogels at concentrations above the CGC. The gel emulsions stabilized by R-6-AO can be prepared with different oils (n-dodecane, n-decane, n-octane, soybean oil, olive oil, tricaprylin) owing to the tricyclic diterpene hydrophobic structure in their molecules that enables them to adopt a unique arrangement in the fibers.

Body mass index cut-off points for predicting chronic non-communicable disease should differ by gender and age group

OBJECTIVES

The objective of this study to determine whether body mass index (BMI) in different genders and age groups need different thresholds when predicting chronic non-communicable diseases (CNCDs).

STUDY DESIGN

This is a cross-sectional study.

METHODS

Data were obtained from the China Health and Nutrition Survey conducted in 2009. Sequential sample cluster analysis was used to group age according to BMI. Propensity score matching was used to eliminate the influence of age. Receiver operating characteristic curve based on gender and age group was used to evaluate the cut-off values and efficiency of BMI in each group.

RESULTS

A total of 8469 individuals were enrolled in this study. Results of sequential sample cluster analyses showed age was divided into three groups: 18-39, 40-59 and 60-99 years. There were significant differences in the distribution of BMI among the three groups for both males and females (P < 0.001). Statistical differences were observed in the distribution of BMI between genders in the 18-39- and 60-99-year-old age groups (P < 0.001). For men, the cut-off values of BMI were ≥25 kg/m², ≥24 kg/m² and ≥23 kg/m² in the 18-39, 40-59 and 60-99 years old groups, respectively; for women, the corresponding cut-off points were ≥25 kg/m², ≥23 kg/m² and ≥25 kg/m² in groups.

CONCLUSIONS

The thresholds for BMI might be different between gender and age group. In addition, it might not be suitable to determine cut-off values of BMI to predict CNCDs for people aged ≥60 years.

FSMB Census of Licensed Physicians in the United States, 2018

There are 985,026 physicians with Doctor of Medicine (MD) and Doctor of Osteopathic Medicine (DO) degrees licensed to practice medicine in the United States and the District of Columbia, according to physician census data compiled by the Federation of State Medical Boards (FSMB). These qualified physicians graduated from 2,089 medical schools in 167 countries and are available to serve a U.S. national population of 327,167,434. While the percentage of physicians who are international medical graduates have remained relatively stable over the last eight years, the percentage of physicians who are women, possess a DO degree, have three or more licenses, or are graduates of a medical school in the Caribbean have increased by varying degrees during that same period.

This report marks the fifth biennial physician census that the FSMB has published, highlighting key characteristics of the nation's available physician workforce, including numbers of licensees by geographic region and state, type of medical degree, location of medical school, age, gender, specialty certification and number of active licenses per physician. The number of licensed physicians in the United States has been growing steadily, due in part to an expansion in the number of medical schools and students during the past two decades, even as concerns of a physician shortage to meet health care demands persist. The average age of licensed physicians continues to increase, and more licensed physicians appear to be specialty certified, though the latter finding may reflect more comprehensive reporting. This census was compiled using the FSMB's Physician Data Center (PDC), which collects, collates and analyzes physician data directly from the nation's state medical and osteopathic boards and is uniquely positioned to provide a comprehensive snapshot of information about licensed physicians. A periodic national census of this type offers useful demographic and licensure information about the available physician workforce that may be useful to policy makers, researchers and related health care organizations to better understand and address the nation's health care needs.

The Relationship Between Board Certification and Disciplinary Actions Against Board-Eligible Family Physicians

PURPOSE

Lack of specialty board certification has been reported as a significant physician-level predictor of receiving a disciplinary action from a state medical board. This study investigated the association between family physicians receiving a disciplinary action from a state medical board and certification by the American Board of Family Medicine (ABFM).

METHOD

Three datasets were merged and a series of logistic regressions were conducted examining the relationship between certification status and disciplinary actions when adjusting for covariates. Data were available from 1976 to 2017. Predictor variables were gender, age, medical training degree type, medical school location, and the severity of the action.

RESULTS

Of the family physicians in this sample, 95% (114,454/120,443) had never received any disciplinary action. Having ever been certified was associated with a reduced likelihood of ever receiving an action (odds ratio [OR] = 0.35; 95% confidence interval [CI] = 0.30, 0.40; P < .001), and having held a prior but not current certification at the time of the action was associated with an increase in receiving the most severe type of action (OR = 3.71; 95% CI = 2.24, 6.13; P < .001).

CONCLUSIONS

Disciplinary actions are uncommon events. Family physicians who had ever been ABFM certified were less likely to receive an action. The most severe actions were associated with decreased odds of being board certified at the time of the action. Receiving the most severe action type increased the likelihood of physicians holding a prior but not current certification.

Viscoelastic lyotropic liquid crystals formed in a bio-based trimeric surfactant system

Exploring the self-assembly of oligomeric surfactants is expected to bridge the gap between conventional and polymeric surfactants. Using the natural resource rosin as the starting material, a bio-based star-shaped trimeric quaternary ammonium surfactant (abbreviated tri-R-4-Phe) was synthesized. With three bulky dehydroabietic acid units in the hydrophobic group, tri-R-4-Phe has a molecular weight of 1684.9 and shows strong affinity towards both water and nonpolar organic compounds. In the presence of tri-R-4-Phe, C12EO3 was able to form lamellar lyotropic liquid crystals over a wide concentration range in water. The tri-R-4-Phe/C12EO3/water tertiary system was investigated by polarizing optical microscopy (POM), small angle X-ray scattering (SAXS) and rheological measurements. The investigated samples with different formulations all showed strong viscoelasticity, and the viscosity increased with the surfactant content. All samples showed interesting shear banding phenomena due to the shear induced mesoscale phase transition in tri-R-4-Phe/C12EO3/water systems. The present work reveals the unique behaviour of trimeric surfactant involved LLC systems and the result may be helpful in investigating delicate molecular self-assembly using natural resources.