Differential assembly diversifies GABAA receptor structures and signalling.

Type A γ-aminobutyric acid receptors (GABAARs) are pentameric ligand-gated chloride channels that mediate fast inhibitory signalling in neural circuits1,2 and can be modulated by essential medicines including general anaesthetics and benzodiazepines3. Human GABAAR subunits are encoded by 19 paralogous genes that can, in theory, give rise to 495,235 receptor types. However, the principles that govern the formation of pentamers, the permutational landscape of receptors that may emerge from a subunit set and the effect that this has on GABAergic signalling remain largely unknown. Here we use cryogenic electron microscopy to determine the structures of extrasynaptic GABAARs assembled from α4, ß3 and δ subunits, and their counterparts incorporating γ2 instead of δ subunits. In each case, we identified two receptor subtypes with distinct stoichiometries and arrangements, all four differing from those previously observed for synaptic, α1-containing receptors4-7. This, in turn, affects receptor responses to physiological and synthetic modulators by creating or eliminating ligand-binding sites at subunit interfaces. We provide structural and functional evidence that selected GABAAR arrangements can act as coincidence detectors, simultaneously responding to two neurotransmitters: GABA and histamine. Using assembly simulations and single-cell RNA sequencing data8,9, we calculated the upper bounds for receptor diversity in recombinant systems and in vivo. We propose that differential assembly is a pervasive mechanism for regulating the physiology and pharmacology of GABAARs.

Cryo-EM structure of the human α1ß3γ2 GABAA receptor in a lipid bilayer.

Type A γ-aminobutyric acid (GABAA) receptors are pentameric ligand-gated ion channels and the main drivers of fast inhibitory neurotransmission in the vertebrate nervous system1,2. Their dysfunction is implicated in a range of neurological disorders, including depression, epilepsy and schizophrenia3,4. Among the numerous assemblies that are theoretically possible, the most prevalent in the brain are the α1ß2/3γ2 GABAA receptors5. The ß3 subunit has an important role in maintaining inhibitory tone, and the expression of this subunit alone is sufficient to rescue inhibitory synaptic transmission in ß1-ß3 triple knockout neurons6. So far, efforts to generate accurate structural models for heteromeric GABAA receptors have been hampered by the use of engineered receptors and the presence of detergents7-9. Notably, some recent cryo-electron microscopy reconstructions have reported 'collapsed' conformations8,9; however, these disagree with the structure of the prototypical pentameric ligand-gated ion channel the Torpedo nicotinic acetylcholine receptor10,11, the large body of structural work on homologous homopentameric receptor variants12 and the logic of an ion-channel architecture. Here we present a high-resolution cryo-electron microscopy structure of the full-length human α1ß3γ2L-a major synaptic GABAA receptor isoform-that is functionally reconstituted in lipid nanodiscs. The receptor is bound to a positive allosteric modulator 'megabody' and is in a desensitized conformation. Each GABAA receptor pentamer contains two phosphatidylinositol-4,5-bisphosphate molecules, the head groups of which occupy positively charged pockets in the intracellular juxtamembrane regions of α1 subunits. Beyond this level, the intracellular M3-M4 loops are largely disordered, possibly because interacting post-synaptic proteins are not present. This structure illustrates the molecular principles of heteromeric GABAA receptor organization and provides a reference framework for future mechanistic investigations of GABAergic signalling and pharmacology.

Author Correction: GABAA receptor signalling mechanisms revealed by structural pharmacology.

In Fig. 5b, d, the arrows showing transmembrane domain rotations were inadvertently pointing clockwise instead of anticlockwise. Similarly, 'anticlockwise' should have been 'clockwise' in the sentence 'This conformational change of the ECD triggers a clockwise rotation of the TMD.' In Extended Data Table 1, the units of the column 'Model resolution' should have been Å instead of Å2. These errors have been corrected online.

GABAA receptor signalling mechanisms revealed by structural pharmacology.

Type-A γ-aminobutyric (GABAA) receptors are ligand-gated chloride channels with a very rich pharmacology. Some of their modulators, including benzodiazepines and general anaesthetics, are among the most successful drugs in clinical use and are common substances of abuse. Without reliable structural data, the mechanistic basis for the pharmacological modulation of GABAA receptors remains largely unknown. Here we report several high-resolution cryo-electron microscopy structures in which the full-length human α1ß3γ2L GABAA receptor in lipid nanodiscs is bound to the channel-blocker picrotoxin, the competitive antagonist bicuculline, the agonist GABA (γ-aminobutyric acid), and the classical benzodiazepines alprazolam and diazepam. We describe the binding modes and mechanistic effects of these ligands, the closed and desensitized states of the GABAA receptor gating cycle, and the basis for allosteric coupling between the extracellular, agonist-binding region and the transmembrane, pore-forming region. This work provides a structural framework in which to integrate previous physiology and pharmacology research and a rational basis for the development of GABAA receptor modulators.

The clinico-pathological spectrum of plaque-type blue naevi and their potential for malignant transformation.

AIMS: Plaque-type blue naevi are rare melanocytic tumours presenting as large, pigmented plaques at birth or during childhood. There is a risk for malignant transformation, but no larger comprehensive studies exist and the diagnosis is challenging, especially on limited biopsy material. The aim is to describe the clinicopathological features and behaviour of the disease more comprehensively. METHODS AND RESULTS: We retrieved eight plaque-type blue naevi, presenting as large, pigmented plaques (median = 7 cm; range = 3-26) most frequently affecting the scalp (four) followed by the cheek, arm, abdominal wall and gluteal cleft (one each), with a slight female predilection. Median age at time of biopsy was 39.5 years (range = 15-90), but three tumours had been present at birth and one since childhood. Histopathologically, the tumours were poorly circumscribed and composed of cellular fascicles of uniform spindle cells in a background of variably prominent pigmented dendritic cells affecting dermis and subcutaneous tissues. The majority had mutations in GNAQ. One tumour showed malignant transformation, characterised by an expansile nodule of pleomorphic epithelioid melanocytes with rhabdoid morphology, high mitotic activity and areas of necrosis. This patient developed metastatic melanoma to lymph nodes. All patients are alive with a median follow-up of 60 months. CONCLUSION: Plaque-type blue naevi are diagnostically challenging tumours with risk for malignant transformation. Awareness and familiarity with the salient clinicopathological features are necessary for reliable diagnosis, and long-term clinical follow-up is required to monitor for malignant transformation.

Applying the antecedent, behaviour, and consequence taxonomy to unintentional firearm injury as determined by a collaborative firearm injury database.

BACKGROUND: Unintentional firearm injury (UFI) remains a significant problem in the USA with respect to preventable injury and death. The antecedent, behaviour and consequence (ABC) taxonomy has been used by law enforcement agencies to evaluate unintentional firearm discharge. Using an adapted ABC taxonomy, we sought to categorise civilian UFI in our community to identify modifiable behaviours. METHODS: Using a collaborative firearm injury database (containing both a university-based level 1 trauma registry and a metropolitan law enforcement database), all UFIs from August 2008 through December 2021 were identified. Perceived threat (antecedent), behaviour and injured party (consequence) were identified for each incident. RESULTS: During the study period, 937 incidents of UFI were identified with 64.2% of incidents occurring during routine firearm tasks. 30.4% of UFI occurred during neglectful firearm behaviour such as inappropriate storage. Most injuries occurred under situations of low perceived threat. UFI involving children was most often due to inappropriate storage of weapons, while cleaning a firearm was the most common behaviour in adults. Overall, 16.5% of UFI involved injury to persons other than the one handling the weapon and approximately 1.3% of UFI resulted in mortality. CONCLUSIONS: The majority of UFI occurred during routine and expected firearm tasks such as firearm cleaning. Prevention programmes should not overlook these modifiable behaviours in an effort to reduce UFIs, complications and deaths.

The occurrence of mental health symptoms in isotretinoin-treated adolescents.

BACKGROUND: Isotretinoin treatment for acne can reduce adverse psychiatric outcomes in adults, but there has been little investigation of the incidence of psychiatric outcomes in treated adolescents. METHODS: This retrospective cohort study using the Rochester Epidemiology Project identified 606 patients aged 12-18 prescribed isotretinoin over a 10-year period between January 1, 2008 and December 31, 2017. Medical records were reviewed to identify psychiatric diagnoses before and during isotretinoin therapy, as well as psychiatric symptoms not captured by formal diagnoses and changes to isotretinoin dosing because of psychiatric diagnoses or symptoms. RESULTS: One hundred seventy-seven (29.2%) had a psychiatric diagnosis prior to isotretinoin initiation, but 98 (16.2%) had a new psychiatric diagnosis or psychiatric symptom while taking isotretinoin. Patients with a psychiatric history were no more likely than those without to receive a new psychiatric diagnosis during treatment (4.5% vs. 3.7%; p = .650), but did experience more psychiatric symptoms, primarily low mood and mood swings (23.7% vs. 7.7%; p < .001). Only 25.5% of the 98 with a new psychiatric diagnosis or psychiatric symptom had a subsequent dose change. A dose change was more likely if patients received a new psychiatric diagnosis (41.7% vs. 20.3%; p = .037) or patients did not have a psychosocial explanation for psychiatric symptoms (34.4% vs. 10.8%; p = .009). CONCLUSIONS: A substantial proportion of adolescent patients prescribed isotretinoin had a prior psychiatric diagnosis. This predicts more psychiatric symptoms during isotretinoin treatment. Adolescents with a psychiatric history who have worsening symptoms and those with new-onset psychiatric symptoms would benefit from close monitoring while taking isotretinoin.

Improving the Therapeutic Index of Smp24, a Venom-Derived Antimicrobial Peptide: Increased Activity against Gram-Negative Bacteria.

Antimicrobial peptides (AMPs) are naturally occurring compounds which possess a rapid killing mechanism and low resistance potential. Consequently, they are being viewed as potential alternatives to traditional antibiotics. One of the major factors limiting further development of AMPs is off-target toxicity. Enhancements to antimicrobial peptides which can maximise antimicrobial activity whilst reducing mammalian cytotoxicity would make these peptides more attractive as future pharmaceuticals. We have previously characterised Smp24, an AMP derived from the venom of the scorpion Scorpio maurus palmatus. This study sought to better understand the relationship between the structure, function and bacterial selectivity of this peptide by performing single amino acid substitutions. The antimicrobial, haemolytic and cytotoxic activity of modified Smp24 peptides was determined. The results of these investigations were compared with the activity of native Smp24 to determine which modifications produced enhanced therapeutic indices. The structure-function relationship of Smp24 was investigated by performing N-terminal, mid-chain and C-terminal amino acid substitutions and determining the effect that they had on the antimicrobial and cytotoxic activity of the peptide. Increased charge at the N-, mid- and C-termini of the peptide resulted in increased antimicrobial activity. Increased hydrophobicity at the N-terminus resulted in reduced haemolysis and cytotoxicity. Reduced antimicrobial, haemolytic and cytotoxic activity was observed by increased hydrophobicity at the mid-chain. Functional improvements have been made to modified peptides when compared with native Smp24, which has produced peptides with enhanced therapeutic indices.

Spray Pattern and Plume Geometry Testing and Methodology: An IPAC-RS Working Group Overview.

Plume characterization for orally inhaled and nasal drug products (OINDP) provides valuable information during OINDP development. Spray pattern and plume geometry techniques, methods, and technology have evolved over the past 20 years since the publication of the original 1998 FDA MDI DPI draft guidance. The International Pharmaceutical Aerosol Consortium on Regulation and Science (IPAC-RS) discusses the historical context and background to plume geometry and spray pattern characterization studies; provides an analysis of the current regulatory context; addresses results from its industry surveys on application and value of such testing; and presents case studies and best practices-seeking to provide insights to regulatory bodies and other stakeholders. Assessment and consideration of published studies and industry experience note the value of plume geometry and spray pattern in development, and that further data is needed regarding their use in assessing formulation characteristics. Continued dialogue between industry and regulatory bodies is needed to establish the optimum use of these techniques.

Photoaffinity labeling identifies an intersubunit steroid-binding site in heteromeric GABA type A (GABAA) receptors.

Allopregnanolone (3α5α-P), pregnanolone, and their synthetic derivatives are potent positive allosteric modulators (PAMs) of GABAA receptors (GABAARs) with in vivo anesthetic, anxiolytic, and anti-convulsant effects. Mutational analysis, photoaffinity labeling, and structural studies have provided evidence for intersubunit and intrasubunit steroid-binding sites in the GABAAR transmembrane domain, but revealed only little definition of their binding properties. Here, we identified steroid-binding sites in purified human α1ß3 and α1ß3γ2 GABAARs by photoaffinity labeling with [3H]21-[4-(3-(trifluoromethyl)-3H-diazirine-3-yl)benzoxy]allopregnanolone ([3H]21-pTFDBzox-AP), a potent GABAAR PAM. Protein microsequencing established 3α5α-P inhibitable photolabeling of amino acids near the cytoplasmic end of the ß subunit M4 (ß3Pro-415, ß3Leu-417, and ß3Thr-418) and M3 (ß3Arg-309) helices located at the base of a pocket in the ß+-α- subunit interface that extends to the level of αGln-242, a steroid sensitivity determinant in the αM1 helix. Competition photolabeling established that this site binds with high affinity a structurally diverse group of 3α-OH steroids that act as anesthetics, anti-epileptics, and anti-depressants. The presence of a 3α-OH was crucial: 3-acetylated, 3-deoxy, and 3-oxo analogs of 3α5α-P, as well as 3ß-OH analogs that are GABAAR antagonists, bound with at least 1000-fold lower affinity than 3α5α-P. Similarly, for GABAAR PAMs with the C-20 carbonyl of 3α5α-P or pregnanolone reduced to a hydroxyl, binding affinity is reduced by 1,000-fold, whereas binding is retained after deoxygenation at the C-20 position. These results provide a first insight into the structure-activity relationship at the GABAAR ß+-α- subunit interface steroid-binding site and identify several steroid PAMs that act via other sites.

Comparing patterns of care and outcomes after operative management of complications after bariatric surgery at MBSAQIP accredited bariatric centers and non-bariatric facilities.

BACKGROUND: Many operations for complications after bariatric surgery are performed by surgeons without bariatric expertise at centers without teams who routinely care for bariatric patients. This study sought to evaluate whether bariatric expertise affects patterns of care and perioperative outcomes among patients undergoing operative intervention for complications after bariatric surgery. METHODS: Administrative claims data from the Kentucky Office of Health Policy were queried for inpatients undergoing operative intervention for complications related to bariatric surgery between 2015 and 2018. Patients were stratified with respect to whether or not they underwent surgery at a Metabolic and Bariatric Surgery Accreditation and Quality Improvement Program (MBSAQIP) accredited bariatric surgery center (BCE) or not (non-BCE). Groups were compared with respect to demographic, procedural, and outcome variables. RESULTS: BCE patients were more often Caucasian than non-BCE patients (p < 0.001) and have either private insurance or Medicare coverage (p = 0.02). Regarding operative approach, operations were more likely to be performed laparoscopically in BCE (88.5% BCE vs. 80.9% non-BCE, p = 0.007). Length of stay was significantly shorter for BCE patients (median 2 days BCE vs. 3 days non-BCE, p < 0.001), and BCE patients were more likely to be discharged home (85.4% BCE vs. 78.5% non-BCE, p = 0.02). Inpatient mortality and average total charges per patient did not differ significantly between the two groups CONCLUSIONS: Surgical management of complications after bariatric surgery at BCE is associated with greater utilization of minimally invasive techniques, shorter hospital stay, and increased likelihood of routine home discharge. These findings should prompt a review and standardization of care patterns for patients with complications after bariatric surgery aimed at optimizing outcomes and improving value.

Competitive Antagonism of Etomidate Action by Diazepam: In Vitro GABAA Receptor and In Vivo Zebrafish Studies.

BACKGROUND: Recent cryo-electron microscopic imaging studies have shown that in addition to binding to the classical extracellular benzodiazepine binding site of the α1ß3γ2L γ-aminobutyric acid type A (GABAA) receptor, diazepam also binds to etomidate binding sites located in the transmembrane receptor domain. Because such binding is characterized by low modulatory efficacy, the authors hypothesized that diazepam would act in vitro and in vivo as a competitive etomidate antagonist. METHODS: The concentration-dependent actions of diazepam on 20 µM etomidate-activated and 6 µM GABA-activated currents were defined (in the absence and presence of flumazenil) in oocyte-expressed α1ß3γ2L GABAA receptors using voltage clamp electrophysiology. The ability of diazepam to inhibit receptor labeling of purified α1ß3γ2L GABAA receptors by [H]azietomidate was assessed in photoaffinity labeling protection studies. The impact of diazepam (in the absence and presence of flumazenil) on the anesthetic potencies of etomidate and ketamine was compared in a zebrafish model. RESULTS: At nanomolar concentrations, diazepam comparably potentiated etomidate-activated and GABA-activated GABAA receptor peak current amplitudes in a flumazenil-reversible manner. The half-maximal potentiating concentrations were 39 nM (95% CI, 27 to 55 nM) and 26 nM (95% CI, 16 to 41 nM), respectively. However, at micromolar concentrations, diazepam reduced etomidate-activated, but not GABA-activated, GABAA receptor peak current amplitudes in a concentration-dependent manner with a half-maximal inhibitory concentration of 9.6 µM (95% CI, 7.6 to 12 µM). Diazepam (12.5 to 50 µM) also right-shifted the etomidate-concentration response curve for direct activation without reducing the maximal response and inhibited receptor photoaffinity labeling by [H]azietomidate. When administered with flumazenil, 50 µM diazepam shifted the etomidate (but not the ketamine) concentration-response curve for anesthesia rightward, increasing the etomidate EC50 by 18-fold. CONCLUSIONS: At micromolar concentrations and in the presence of flumazenil to inhibit allosteric modulation via the classical benzodiazepine binding site of the GABAA receptor, diazepam acts as an in vitro and in vivo competitive etomidate antagonist.

Multiple Epidermolytic Acanthomas: Rare Vulval Lesions Which May be Mistaken for Viral Warts.

Epidermolytic acanthoma is a rare benign lesion that most often presents as a solitary or multiple small papular lesions on the trunk, face, limbs or external male genitalia. Only a small number of cases have been reported occurring on the vulva and clinically and histologically they may mimic and be misdiagnosed as viral warts. We report 2 cases of multiple epidermolytic acanthomas localized to the vulva. Molecular tests (in situ hybridization and polymerase chain reaction) showed no evidence of human papillomavirus infection and p16 staining was negative. We stress the need for pathologists to consider epidermolytic acanthoma in the differential diagnosis of multiple vulval lesions resembling viral warts.

The Boeing 737 MAX: Lessons for Engineering Ethics.

The crash of two 737 MAX passenger aircraft in late 2018 and early 2019, and subsequent grounding of the entire fleet of 737 MAX jets, turned a global spotlight on Boeing's practices and culture. Explanations for the crashes include: design flaws within the MAX's new flight control software system designed to prevent stalls; internal pressure to keep pace with Boeing's chief competitor, Airbus; Boeing's lack of transparency about the new software; and the lack of adequate monitoring of Boeing by the FAA, especially during the certification of the MAX and following the first crash. While these and other factors have been the subject of numerous government reports and investigative journalism articles, little to date has been written on the ethical significance of the accidents, in particular the ethical responsibilities of the engineers at Boeing and the FAA involved in designing and certifying the MAX. Lessons learned from this case include the need to strengthen the voice of engineers within large organizations. There is also the need for greater involvement of professional engineering societies in ethics-related activities and for broader focus on moral courage in engineering ethics education.

Identifying Drugs that Bind Selectively to Intersubunit General Anesthetic Sites in the α1ß3γ2 GABAAR Transmembrane Domain.

GABAA receptors (GABAARs) are targets for important classes of clinical agents (e.g., anxiolytics, anticonvulsants, and general anesthetics) that act as positive allosteric modulators (PAMs). Previously, using photoreactive analogs of etomidate ([3H]azietomidate) and mephobarbital [[3H]1-methyl-5-allyl-5-(m-trifluoromethyl-diazirynylphenyl)barbituric acid ([3H]R-mTFD-MPAB)], we identified two homologous but pharmacologically distinct classes of general anesthetic binding sites in the α1ß3γ2 GABAAR transmembrane domain at ß +-α - (ß + sites) and α +-ß -/γ +-ß - (ß - sites) subunit interfaces. We now use competition photolabeling with [3H]azietomidate and [3H]R-mTFD-MPAB to identify para-substituted propofol analogs and other drugs that bind selectively to intersubunit anesthetic sites. Propofol and 4-chloro-propofol bind with 5-fold selectivity to ß +, while derivatives with bulkier lipophilic substitutions [4-(tert-butyl)-propofol and 4-(hydroxyl(phenyl)methyl)-propofol] bind with ∼10-fold higher affinity to ß - sites. Similar to R-mTFD-MPAB and propofol, these drugs bind in the presence of GABA with similar affinity to the α +-ß - and γ +-ß - sites. However, we discovered four compounds that bind with different affinities to the two ß - interface sites. Two of these bind with higher affinity to one of the ß - sites than to the ß + sites. We deduce that 4-benzoyl-propofol binds with >100-fold higher affinity to the γ +-ß - site than to the α +-ß - or ß +-α - sites, whereas loreclezole, an anticonvulsant, binds with 5- and 100-fold higher affinity to the α +-ß - site than to the ß + and γ +-ß - sites. These studies provide a first identification of PAMs that bind selectively to a single intersubunit site in the GABAAR transmembrane domain, a property that may facilitate the development of subtype selective GABAAR PAMs.

An international multicenter study to evaluate reproducibility of automated scoring for assessment of Ki67 in breast cancer.

The nuclear proliferation biomarker Ki67 has potential prognostic, predictive, and monitoring roles in breast cancer. Unacceptable between-laboratory variability has limited its clinical value. The International Ki67 in Breast Cancer Working Group investigated whether Ki67 immunohistochemistry can be analytically validated and standardized across laboratories using automated machine-based scoring. Sets of pre-stained core-cut biopsy sections of 30 breast tumors were circulated to 14 laboratories for scanning and automated assessment of the average and maximum percentage of tumor cells positive for Ki67. Seven unique scanners and 10 software platforms were involved in this study. Pre-specified analyses included evaluation of reproducibility between all laboratories (primary) as well as among those using scanners from a single vendor (secondary). The primary reproducibility metric was intraclass correlation coefficient between laboratories, with success considered to be intraclass correlation coefficient >0.80. Intraclass correlation coefficient for automated average scores across 16 operators was 0.83 (95% credible interval: 0.73-0.91) and intraclass correlation coefficient for maximum scores across 10 operators was 0.63 (95% credible interval: 0.44-0.80). For the laboratories using scanners from a single vendor (8 score sets), intraclass correlation coefficient for average automated scores was 0.89 (95% credible interval: 0.81-0.96), which was similar to the intraclass correlation coefficient of 0.87 (95% credible interval: 0.81-0.93) achieved using these same slides in a prior visual-reading reproducibility study. Automated machine assessment of average Ki67 has the potential to achieve between-laboratory reproducibility similar to that for a rigorously standardized pathologist-based visual assessment of Ki67. The observed intraclass correlation coefficient was worse for maximum compared to average scoring methods, suggesting that maximum score methods may be suboptimal for consistent measurement of proliferation. Automated average scoring methods show promise for assessment of Ki67 scoring, but requires further standardization and subsequent clinical validation.

Identification of binding sites contributing to volatile anesthetic effects on GABA type A receptors.

Most general anesthetics enhance GABA type A (GABAA) receptor activity at clinically relevant concentrations. Sites of action of volatile anesthetics on the GABAA receptor remain unknown, whereas sites of action of many intravenous anesthetics have been identified in GABAA receptors by using photolabeling. Here, we used photoactivatable analogs of isoflurane (AziISO) and sevoflurane (AziSEVO) to locate their sites on α1ß3γ2L and α1ß3 GABAA receptors. As with isoflurane and sevoflurane, AziISO and AziSEVO enhanced the currents elicited by GABA. AziISO and AziSEVO each labeled 10 residues in α1ß3 receptors and 9 and 8 residues, respectively, in α1ß3γ2L receptors. Photolabeled residues were concentrated in transmembrane domains and located in either subunit interfaces or in the interface between the extracellular domain and the transmembrane domain. The majority of these transmembrane residues were protected from photolabeling with the addition of excess parent anesthetic, which indicated specificity. Binding sites were primarily located within α+/ß- and ß+/α- subunit interfaces, but residues in the α+/γ- interface were also identified, which provided a basis for differential receptor subtype sensitivity. Isoflurane and sevoflurane did not always share binding sites, which suggests an unexpected degree of selectivity.-Woll, K. A., Zhou, X., Bhanu, N. V., Garcia, B. A., Covarrubias, M., Miller, K. W., Eckenhoff, R. G. Identification of binding sites contributing to volatile anesthetic effects on GABA type A receptors.

Investigation into Photoinduced Auto-Oxidation of Polycyclic Aromatic Hydrocarbons Resulting in Brown Carbon Production.

Brown carbon (BrC) is a collection of oxidized atmospheric aromatic compounds detected worldwide with broad functionality. This multifunctional nature allows BrC to be water-soluble and bioavailable and demonstrate light absorption at multiple wavelengths. Polycyclic aromatic hydrocarbons (PAH) are major primary products of combustion emissions and have long been known to oxidize in the environment as components of secondary organic aerosols. In this study, we have exposed aqueous PAH suspensions to simulated sunlight to investigate oxidized PAH as BrC precursors. Illuminated samples of naphthalene and anthracene demonstrated growth of several new products with absorptions and oxidation consistent with humic-like substances (HULIS). Reactions of aqueous naphthalene, anthracene, and their oxidized derivatives were found to produce chromatographic and spectroscopic evidence of HULIS formation when exposed to sunlight. The association of oxyradicals with HULIS has implications on human health via lung tissue damage; and its absorption character may add to radiative forcing processes in the atmosphere. The overall product characterizations from naphthalene and anthracene indicate reaction mechanism pathways that use oxidized alcohol and quinone as intermediate species.

Understanding frames: A qualitative exploration of standing frame use for young people with cerebral palsy in educational settings.

BACKGROUND: Consensus opinion supports standing frame use as part of postural management for nonambulant young people with cerebral palsy. Most young people with cerebral palsy in the United Kingdom, who use standing frames, use them at nursery or school, rather than at home. In this paper we report professionals' and parents' experiences and views of standing frame use specifically in educational settings. This research was conducted as part of a large mixed methods study to determine the acceptability and inform the design of a future trial of standing frames. METHODS: Qualitative methods were used: focus groups with educational professionals, parents and clinicians (paediatricians, physiotherapists and occupational therapists) were convened. Data were analysed thematically using framework analysis. RESULTS: Five focus groups were conducted. The overarching theme "flexibility" encompassed four subordinate themes: (i) "balancing education and therapy," which described the way education professionals had to juggle different priorities from health professionals within a multi-disciplinary team; (ii) "young people's autonomy," which highlighted participants' belief that standing frame use should be centred on the individual young person and their needs; (iii) "working within logistical boundaries," which demonstrated that "ideal" standing frame use was not always possible due to logistical issues (e.g., staffing and standing frame availability); and (iv) "competence and confidence," which highlighted that educational professionals felt that they lacked the training to confidently position young people in their standing frame. CONCLUSIONS: This paper highlights the complexity of standing frame use in the educational setting. If a standing frame programme is prescribed to be delivered in an educational setting, strong multidisciplinary and interagency communication is essential to balance therapy versus education. Training is required to ensure staff are competent in using the standing frame with the young person understanding their individual requirements. A flexible approach-inclusive of the young person's needs, logistical demands and resource-is necessary.

Self-Driving Cars and Engineering Ethics: The Need for a System Level Analysis.

The literature on self-driving cars and ethics continues to grow. Yet much of it focuses on ethical complexities emerging from an individual vehicle. That is an important but insufficient step towards determining how the technology will impact human lives and society more generally. What must complement ongoing discussions is a broader, system level of analysis that engages with the interactions and effects that these cars will have on one another and on the socio-technical systems in which they are embedded. To bring the conversation of self-driving cars to the system level, we make use of two traffic scenarios which highlight some of the complexities that designers, policymakers, and others should consider related to the technology. We then describe three approaches that could be used to address such complexities and their associated shortcomings. We conclude by bringing attention to the "Moral Responsibility for Computing Artifacts: The Rules", a framework that can provide insight into how to approach ethical issues related to self-driving cars.