The cogwheel model of hierarchical self-organization provides a route to highly ordered crystalline helical columnar hexagonal arrays of perylene bisimides (PBIs) conjugated to (3,4,5)-dimethyloctyl ...(racemic dm8*, r) minidendrons. Cogwheel PBIs assemble with identical structural order irrespective of molecular chirality to generate helical columns jacketed with an alkyl coat with length equal to half the helical pitch, exhibiting helical deracemization in the crystal state. These assemblies were accessible only via annealing or cooling and reheating at 1 °C/min. Recently it was discovered that hybrid rr8 sequence-defined dendrons with r and linear n-octyl (8) chains enabled the formation of the cogwheel phase at 10 °C/min upon heating but not cooling. Here we report four libraries of hybrid PBIs with sequence-defined dendrons containing r and n-alkyl (C n H2n+1) chains with n = 6, 7, 9, and 10. Structural analysis of these libraries by fiber X-ray diffraction and differential scanning calorimetry reveals that the 9r9 sequence enables an extraordinary acceleration of cogwheel assembly at rates of up to 50 °C/min on heating and cooling, providing, to the best of our knowledge, the fastest crystallizing supramolecular or covalent macromolecule known. Solid-state NMR studies help to elucidate this unexpected and unprecedented extraordinary acceleration of hierarchical self-organization, which arises from a combination of crystal packing of the ideal tertiary structure and alkyl chain dynamics. This general model raises questions about the use of achiral motifs to achieve high structural order in chiral systems and the need for disorder to create order in complex biological and bioinspired synthetic systems.
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A ring expansion of tetramic acids (pyrrolidine-2,4-diones) to N-oxy-2,5-diketopiperazines (DKPs) is described. This method allows for the facile and late-stage construction of the ...hydroxamic acid moiety and can thereby serve as a general method for accessing N-oxy-2,5-DKP natural products.
A dendronized perylene bisimide (PBI) that self-organizes into hexagonal arrays of supramolecular double helices with identical single-crystal-like order that disregards chirality was recently ...reported. A cogwheel model of self-assembly that explains this process was proposed. Accessing the highly ordered cogwheel phase required very slow heating and cooling or extended periods of annealing. Analogous PBIs with linear alkyl chains did not exhibit the cogwheel assembly. Here a library of sequence-defined dendrons containing all possible compositions of linear and racemic alkyl chains was employed to construct self-assembling PBIs. Thermal and structural analysis of their assemblies by differential scanning calorimetry (DSC) and fiber X-ray diffraction (XRD) revealed that the incorporation of n-alkyl chains accelerates the formation of the high order cogwheel phase, rendering the previously invisible phase accessible under standard heating and cooling rates. Small changes to the primary structure, as constitutional isomerism, result in significant changes to macroscopic properties such as melting of the periodic array. This study demonstrated how changes to the sequence-defined primary structure, including the relocation of methyl groups between two constitutional isomers, dictate tertiary and quaternary structure in hierarchical assemblies. This led to the discovery of a sequence that self-organizes the cogwheel assembly much faster than even the corresponding homochiral compounds and demonstrated that defined-sequence, which has long been recognized as a determinant for the complex structure of biomacromolecules including proteins and nucleic acids, plays the same role also in supramolecular synthetic systems.
A library containing 10 air-stable NiIIX(Aryl)(PCy3)2 σ-complexes as precatalysts (X = Cl, Br, OTs, OMs, aryl = 1-naphthyl, 2-naphthyl; X = Cl, 1-acenaphthenyl, 1-(2-methoxynaphthyl), ...9-phenanthrenyl, 9-anthracyl) was synthesized and demonstrated to quantitatively cross-couple 2-methoxyphenyl dimethylsulfamate with methyl 4-(5,5-dimethyl-1,3,2-dioxaborinane-2-yl)benzoate at 23 °C in dry THF in the presence of K3PO4(H2O)3.2 in less than 60 min. Lower or higher amounts of H2O in K3PO4 and as received THF mediate the same transformation in a maximum three times longer reaction time.
BACKGROUND:Magnetic resonance imaging (MRI) is preferred for imaging the central nervous system (CNS). An important hazard for neurostimulation patients is heating at the electrode interface induced, ...for example, by 64-MHz radiofrequency (RF) magnetic fields of a 1.5T scanner.
OBJECTIVE:We performed studies to define the thermal dose (time and temperature) that would not cause symptomatic neurological injury.
METHODS:Approaches included animal studies where leads with temperature probes were implanted in the brain or spine of sheep and exposed to RF-induced temperatures of 37°C to 49°C for 30 minutes. Histopathological examinations were performed 7 days after recovery. We also reviewed the threshold for RF lesions in the CNS, and for CNS injury from cancer hyperthermia. Cumulative equivalent minutes at 43°C was used to normalize the data to exposure times and temperatures expected during MRI.
RESULTS:Deep brain and spinal RF heating up to 43°C for 30 minutes produced indistinguishable effects compared with 37°C controls. Exposures greater than 43°C for 30 minutes produced temperature-dependent, localized thermal damage. These results are consistent with limits on hyperthermia exposure to 41.8°C for 60 minutes in patients who have cancer and with the reversibility of low-temperature and short-duration trial heating during RF lesion procedures.
CONCLUSION:A safe temperature for induced lead heating is 43°C for 30 minutes. MRI-related RF heating above 43°C or longer than 30 minutes may be associated with increased risk of clinically evident thermal damage to neural structures immediately surrounding implanted leads. The establishment of a thermal dose limit is a first step toward making specific neurostimulation systems conditionally safe during MRI procedures.
ABBREVIATIONS:ASTM, American Society for Testing and MaterialsCEM, cumulative effect minutesCNS, central nervous systemDBS, deep brain stimulationRF, radiofrequencySAR, specific absorption rateSCS, spinal cord stimulationWBHT, whole-body human hyperthermia
A six-year-old child presented with airway obstruction requiring emergency tracheostomy secondary to infection in the remnant left Wharton's duct following SMG ligation. Whilst co-morbidities ...contributing to, and management of sialorrhea are well documented; near-catastrophic post-operative complications are not. We reflect on efficacy of surgical management in sialorrhea, and re-evaluate procedural morbidity.
For three decades, researchers have sought to gain a greater understanding of the developmental antecedents to later perpetration or victimization of violence in romantic relationships. Whereas the ...majority of early studies focused on family-of-origin factors, attention in recent years has turned to additional ecologies such as peer relationships. This review highlights accomplishments of both family and peer studies that focus on violent romantic relationships in an effort to summarize the current state of knowledge. Attention is given to epidemiology and developmental family and peer factors, with special attention given to mechanisms that mediate and/or moderate the relation between family and peer factors and later participation in violent relationships. A critical approach is taken throughout the review in order to identify limitations of previous studies, and to highlight key findings. A case is made for viewing these developmental antecedents as a result of multiple developmental ecologies that is perhaps best summarized as a culture of violence.
Alcohol screening and brief intervention (SBI) in trauma patients has been reported in literature to be effective in changing harmful drinking patterns and injury recurrence. Despite good evidence ...that SBI can benefit patients and provide a more holistic care, it is not routinely implemented in acute medical settings in Australia, in particular emergency departments (EDs).
This paper aims to assess the knowledge, confidence, and practice of alcohol SBI in trauma patients by emergency physicians throughout Australia and New Zealand through an online survey.
Major EDs in Australia and Zealand were approached to participate in an online survey. Results from the survey were analyzed using simple descriptive summary statistics.
Fifty-eight physicians participated in the online survey. Almost all physicians reported at least 10% of all patients managed in ED had traumatic injuries and 35% had alcohol involvement. About 66% were consultant physicians and 84% had 5 or more years of practice. Sixty-four percent agreed to have adequate training in SBI, 22% had adequate time and resources, 47% would like more training in patient screening, and 72% were more likely to deliver SBI in 5 min. Limited time and resources were seen as major barriers. It was found that better understating of SBI may lead to higher confidence and more practice, or vice versa.
High proportion of participants in this survey felt under-equipped to deliver SBI due to time limitation, perceived lack of resources, unsuitable environment, and supportive staff. There exists an opportunity to develop a shortened and efficient SBI program that can improve utilization of SBI in an emergency setting.
The Wide Range Achievement Test, 3rd edition, Reading Recognition subtest (WRAT-3 RR) is an established measure of premorbid ability. Furthermore, its long-term reliability is not well documented, ...particularly in diverse populations with CNS-relevant disease. Objective: We examined test-retest reliability of the WRAT-3 RR over time in an HIV+ sample of predominantly racial/ethnic minority adults. Method: Participants (N = 88) completed a comprehensive neuropsychological battery, including the WRAT-3 RR, on at least two separate study visits. Intraclass correlation coefficients (ICCs) were computed using scores from baseline and follow-up assessments to determine the test-retest reliability of the WRAT-3 RR across racial/ethnic groups and changes in medical (immunological) and clinical (neurocognitive) factors. Additionally, Fisher's Z tests were used to determine the significance of the differences between ICCs. Results: The average test-retest interval was 58.7 months (SD = 36.4). The overall WRAT-3 RR test-retest reliability was high (r = .97, p < .001) and remained robust across all demographic, medical, and clinical variables (all r's > .92). ICCs did not differ significantly between the subgroups tested (all Fisher's Z p's > .05). Conclusions: Overall, this study supports the appropriateness of word-reading tests, such as the WRAT-3 RR, for use as stable premorbid IQ estimates among ethnically diverse groups. Moreover, this study supports the reliability of this measure in the context of change in health and neurocognitive status and in lengthy inter-test intervals. These findings offer strong rationale for reading as a "hold" test, even in the presence of a chronic, variable disease such as HIV.
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