The relationship between meal carbohydrate quantity and the insulin to carbohydrate ratio required to maintain glycaemia is non-linear in young people with type 1 diabetes: A randomized crossover trial.

OBJECTIVE: To determine if the relationship between meal carbohydrate quantity and the insulin to carbohydrate ratio (ICR) required to maintain glycaemia is linear in people with type 1 diabetes. METHODS: We used an open labelled randomized four-arm cross-over study design. Participants (N = 31) aged 12-27 years, HbA1c ≤ 64 mmol/mol (8.0%) received insulin doses based on the individual's ICR and the study breakfast carbohydrate quantity and then consumed four breakfasts containing 20, 50, 100 and 150 g of carbohydrate over four consecutive days in randomized order. The breakfast fat and protein percentages were standardized. Postprandial glycaemia was assessed by 5 h continuous glucose monitoring. The primary outcome was percent time in range (TIR) and secondary outcomes included hypoglycaemia, glucose excursion and incremental area under the curve. Statistical analysis included linear mixed modelling and Wilcoxon signed rank tests. RESULTS: The 20 g carbohydrate breakfast had the largest proportion of TIR (0.74 ± 0.29 p < 0.04). Hypoglycaemia was more frequent in the 50 g (n = 13, 42%) and 100 g (n = 15, 50%) breakfasts compared to the 20 g (n = 6, 20%) and 150 g (n = 7, 26%) breakfasts (p < 0.029). The 150 g breakfast glucose excursion pattern was different from the smaller breakfasts with the lowest glucose excursion 0-2 h and the highest excursion from 3.5 to 5 h. CONCLUSIONS: A non-linear relationship between insulin requirement and breakfast carbohydrate content was observed, suggesting that strengthened ICRs are needed for meals with ≤20 and ≥150 g of carbohydrate. Meals with ≥150 g of carbohydrate may benefit from dual wave bolusing.

Hybrid closed-loop therapy with a first-generation system increases confidence and independence in diabetes management in youth with type 1 diabetes.

AIM: Hybrid closed-loop (HCL) therapy improves glycaemic control in adolescents with type 1 diabetes; however, little is known about their lived experience using these systems. The aim of this study was to explore the lived experiences of youth with type 1 diabetes using HCL therapy, and their parents, to provide insight into their lived experiences. METHODS: Adolescents and young adults aged 12-25 years, who used Medtronic MiniMed™ 670G HCL system during a 6-month randomised clinical trial, and their parents, were invited to participate in a semi-structured interview at the end of the study. Open-ended questions were used to explore the lived experiences of families using HCL. The interviews were audio-recorded, transcribed and analysed using thematic analysis to determine the main themes. RESULTS: In all, 17 young people with type 1 diabetes mean ± SD age: 17.5 ± 4.2 years, diabetes duration: 11.0 ± 4.9 years and HbA1c 64 ± 9 mmol/mol (8.0 ± 0.8%) and 10 parents were interviewed. Three themes were identified: (1) 'Developing confidence and trust in the system', (2) 'Reduction in anxiety' and (3) 'Issues with device'. They reported a positive experience using HCL, with improvements in glucose levels and increased independence with diabetes management. However, frustration around the number of alarms and notifications associated with the system were also identified as issues. CONCLUSION: Both youth and parents acknowledged the benefits of this first-generation HCL system in improving glycaemic outcomes and in providing flexibility and independence. These lived experiences provide valuable information in the introduction and provision of targeted education with HCL therapy.

The Influence of Social Desirability on Sexual Behavior Surveys: A Review.

Research in fields for which self-reported behaviors can be compared with factual data reveals that misreporting is pervasive and often extreme. The degree of misreporting is correlated with the level of social desirability, i.e., the need to respond in a culturally appropriate manner. People who are influenced by social desirability tend to over-report culturally desired behaviors and under-report undesired behaviors. This paper reviews socially desirable responding in sexual behavior research. Given the very private nature of the sexual activity, sex researchers generally lack a gold standard by which to compare self-reported sexual behaviors and have relied on the anonymity of participants as the methodology to assure honest answers on sexual behavior surveys. However, indirect evidence indicates that under-reporting (e.g., of a number of sexual partners, receptive anal intercourse, condom use) is common. Among the general population, several studies have now reported that even with anonymous responding, there are significant correlations between a variety of self-reported sexual behaviors (e.g., use of condoms, sexual fantasies, exposure to pornography, penis size) and social desirability, with evidence that extreme under- or over-reporting is as common as is found in other fields. When asking highly sensitive questions, sex researchers should always include a measure of social desirability and take that into account when analyzing their results.

Oral-Genital Contact and the Meaning of "Had Sex": The Role of Social Desirability.

Previous studies have found that a large proportion of college students do not consider oral-genital contact as having "had sex." In all studies, the questions posed were hypothetical. In the present study, university students were asked about their own personal sexual experiences. From a large pool of participants, two subgroups were identified: those who responded "No" to having "had sex" but responded "Yes" to having had oral-genital contact (No-Yes), and those who responded "Yes" to having had both sex and oral-genital contact (Yes-Yes). None of the participants in these two subgroups self-reported vaginal or anal intercourse. The No-Yes group was significantly higher in social desirability (p < .0005) as measured by the Marlowe-Crowne scale and was also significantly higher in religiosity (p < .01) as measured on a 7-point Likert scale. There was a modest correlation between level of religiosity and social desirability (r = .25, p < .01). It was concluded that many students who have had oral-genital contact but deny having had sex do so because of impression management, i.e., a desire to present themselves more positively. These results provide further evidence that social desirability responding is a serious problem for sex researchers, one that affects even the most basic questions about having had sex.

Insulin strategies for dietary fat and protein in type 1 diabetes: A systematic review.

AIM: To identify and report the efficacy of insulin strategies used to manage glycaemia following fat and/or fat and protein meals in type 1 diabetes. METHODS: A systematic literature search of medical databases from 1995 to 2021 was undertaken. Inclusion criteria were randomised controlled trials that reported at least one of the following glycaemic outcomes: mean glucose, area under the curve, time in range or hypoglycaemic episodes. RESULTS: Eighteen studies were included. Thirteen studies gave additional insulin. Five studies gave an additional 30%-43% of the insulin-to-carbohydrate ratio (ICR) for 32-50 g of fat and 31%-51% ICR for 7-35 g of fat with 12-27 g of protein added to control meals. A further eight studies gave -28% to +75% ICR using algorithms based on fat and protein for meals with 19-50 g of carbohydrate, 2-79 g of fat and 10-60 g of protein, only one study reported a glycaemic benefit of giving less than an additional 24% ICR. Eight studies evaluated insulin delivery patterns. Four of six studies in pump therapy, and one of two studies in multiple daily injections showed the combination of bolus and split dose, respectively, were superior. Five studies examined the insulin dose split, four demonstrated 60%-125% ICR upfront was necessary. Two studies investigated the timing of insulin delivery, both reported administration 15 min before the meal lowered postprandial glycaemia. CONCLUSIONS: Findings highlight the glycaemic benefit of an additional 24%-75% ICR for fat and fat and protein meals. For these meals, there is supportive evidence for insulin delivery in a combination bolus with a minimum upfront dose of 60% ICR, 15 min before the meal.

For a high fat, high protein breakfast, preprandial administration of 125% of the insulin dose improves postprandial glycaemic excursions in people with type 1 diabetes using multiple daily injections: A cross-over trial.

AIM: To determine the glycaemic impact of an increased insulin dose, split insulin dose and regular insulin for a high fat, high protein breakfast in people with type 1 diabetes using multiple daily injections (≥4/day). METHODS: In this cross-over trial, participants received the same high fat, high protein breakfast (carbohydrate:30 g, fat:40 g, protein:50 g) for 4 days. Four different insulin strategies were randomly allocated and tested; 100% of the insulin-to-carbohydrate ratio (ICR) given in a single dose using aspart insulin (100Asp), 125% ICR given in a single dose using aspart (125Asp) or regular insulin (125Reg) and 125% ICR given in a split dose using aspart insulin (100:25Asp). Insulin was given 0.25 hr pre-meal and for 100:25Asp, also 1 hr post-meal. Postprandial sensor glucose was measured for 5 hr. RESULTS: In all, 24 children and adults were participated. The 5-hr incremental area under the curves for 100Asp, 125Asp, 125Reg and 100:25Asp were 620 mmol/L.min [95% CI: 451,788], 341 mmol/L.min [169,512], 675 mmol/L.min [504,847] and 434 mmol/L.min [259,608], respectively. The 5-hr incremental area under the curve for 125Asp was significantly lower than for 100Asp (p = 0.016) and for 125Reg (p = 0.002). There was one episode of hypoglycaemia in 125Reg. CONCLUSIONS: For a high fat, high protein breakfast, giving 125% ICR preprandially, using aspart insulin significantly improved postprandial glycaemia without hypoglycaemia. There was no additional glycaemic benefit from giving insulin in a split dose (100:25%) or replacing aspart with regular insulin.

In children and young people with type 1 diabetes using Pump therapy, an additional 40% of the insulin dose for a high-fat, high-protein breakfast improves postprandial glycaemic excursions: A cross-over trial.

AIM: To determine the insulin requirement for a high-fat, high-protein breakfast to optimise postprandial glycaemic excursions in children and young people with type 1 diabetes using insulin pumps. METHODS: In all, 27 participants aged 10-23 years, BMI <95th percentile (2-18 years) or BMI <30 kg/m2 (19-25 years) and HbA1c ≤64 mmol/mol (≤8.0%) consumed a high-fat, high-protein breakfast (carbohydrate: 30 g, fat: 40 g and protein: 50 g) for 4 days. In this cross-over trial, insulin was administered, based on the insulin-to-carbohydrate ratio (ICR) of 100% (control), 120%, 140% and 160%, in an order defined by a randomisation sequence and delivered in a combination bolus, 60% » hr pre-meal and 40% over 3 hr. Postprandial sensor glucose was assessed for 6 hr. RESULTS: Comparing 100% ICR, 140% ICR and 160% ICR resulted in significantly lower 6-hr areas under the glucose curves: mean (95%CI) (822 mmol/L.min [605,1039] and 567 [350,784] vs 1249 [1042,1457], p ≤ 0.001) and peak glucose excursions (4.0 mmol/L [3.0,4.9] and 2.7 [1.7,3.6] vs 6.0 [5.0,6.9],p < 0.001). Rates of hypoglycaemia for 100%-160% ICR were 7.7%, 7.7%, 12% and 19% respectively (p ≥ 0.139). With increasing insulin dose, a step-wise reduction in mean glucose excursion was observed from 1 to 6 hr (p = 0.008). CONCLUSIONS: Incrementally increasing the insulin dose for a high-fat, high-protein breakfast resulted in a predictable, dose-dependent reduction in postprandial glycaemia: 140% ICR improved postprandial glycaemic excursions without a statistically significant increase in hypoglycaemia. These findings support a safe, practical method for insulin adjustment for high-fat, high-protein meals that can be readily implemented in practice to improve postprandial glycaemia.

Does dietary fat cause a dose dependent glycemic response in youth with type 1 diabetes?

OBJECTIVE: To determine the glycemic impact of dietary fat alone consumed without prandial insulin in individuals with T1D. RESEARCH DESIGN AND METHODS: Thirty participants with T1D (aged 8-18 years) consumed a test drink with either 20 g glucose or 1, 13, 26, 39, 51 g of fat with negligible carbohydrate/protein on 6 consecutive evenings, in a randomized order without insulin. Continuous glucose monitoring was used to measure glucose levels for 8 h postprandially. Primary outcome was mean glycemic excursion at each 30 min interval for each test condition. Generalized linear mixed models with a random effect for people with diabetes were used to test for an increase in blood glucose excursion with increasing quantity of fat. RESULTS: Glycemic excursions after 20 g glucose were higher than after fat drinks over the first 2 h (p < 0.05). Glycemic excursion for the fat drinks demonstrated a dose response, statistically significant from 4 h (p = 0.026), such that increasing loads of fat caused a proportionally larger increase in glycemic excursion, remaining statistically significant until 8 h (p < 0.05). Overall, for every 10 g fat added to the drink, glucose concentrations rose by a mean of 0.28 mmol L-1 from 330 min (95% CI 0.15 to 0.39, p < 0.001). CONCLUSIONS: Fat ingested without other macronutrients increases glucose excursions from 4 to 8 h after ingestion, in a dose dependent manner. These observations may impact on insulin dosing for high-fat foods in individuals with T1D.

Changes to care delivery at nine international pediatric diabetes clinics in response to the COVID-19 global pandemic.

BACKGROUND: Pediatric diabetes clinics around the world rapidly adapted care in response to COVID-19. We explored provider perceptions of care delivery adaptations and challenges for providers and patients across nine international pediatric diabetes clinics. METHODS: Providers in a quality improvement collaborative completed a questionnaire about clinic adaptations, including roles, care delivery methods, and provider and patient concerns and challenges. We employed a rapid analysis to identify main themes. RESULTS: Providers described adaptations within multiple domains of care delivery, including provider roles and workload, clinical encounter and team meeting format, care delivery platforms, self-management technology education, and patient-provider data sharing. Providers reported concerns about potential negative impacts on patients from COVID-19 and the clinical adaptations it required, including fears related to telemedicine efficacy, blood glucose and insulin pump/pen data sharing, and delayed care-seeking. Particular concern was expressed about already vulnerable patients. Simultaneously, providers reported 'silver linings' of adaptations that they perceived as having potential to inform care and self-management recommendations going forward, including time-saving clinic processes, telemedicine, lifestyle changes compelled by COVID-19, and improvements to family and clinic staff literacy around data sharing. CONCLUSIONS: Providers across diverse clinical settings reported care delivery adaptations in response to COVID-19-particularly telemedicine processes-created challenges and opportunities to improve care quality and patient health. To develop quality care during COVID-19, providers emphasized the importance of generating evidence about which in-person or telemedicine processes were most beneficial for specific care scenarios, and incorporating the unique care needs of the most vulnerable patients.

Average-Size Erect Penis: Fiction, Fact, and the Need for Counseling.

Most men believe that the average length of an erect penis is greater than 6 inches (15.24 cm). This belief is due, in part, to several often-cited studies that relied on self-reported measurements, with means of about 6.2 inches (15.75 cm) for heterosexual men and even greater for gay men. These studies suffered from both volunteer bias and social desirability bias. In this review, the combined mean for 10 studies in which researchers took measurements of erect penises was 5.36 inches (13.61 cm; n = 1,629). For 21 studies in which researchers measured stretched penises, the mean was approximately 5.11 inches (12.98 cm; n = 13,719). Based on these studies, the average length of an erect penis is between 5.1 and 5.5 inches (12.95-13.97 cm), but after taking volunteer bias into account, it is probably toward the lower end of this range. Studies show that a majority of men wish they were larger, with some choosing penile lengthening surgery. These surgeries are considered by the American Urological Association to be risky. Most men seeking surgery have normal sized penises. Counseling with factual information about penis size might be effective in alleviating concerns for the majority of men who worry about having a small penis.

Temporal trends in diabetic ketoacidosis at diagnosis of paediatric type 1 diabetes between 2006 and 2016: results from 13 countries in three continents.

AIMS/HYPOTHESIS: The aim of this work was to evaluate geographical variability and trends in the prevalence of diabetic ketoacidosis (DKA), between 2006 and 2016, at the diagnosis of childhood-onset type 1 diabetes in 13 countries over three continents. METHODS: An international retrospective study on DKA at diagnosis of diabetes was conducted. Data on age, sex, date of diabetes diagnosis, ethnic minority status and presence of DKA at diabetes onset were obtained from Australia, Austria, Czechia, Denmark, Germany, Italy, Luxembourg, New Zealand, Norway, Slovenia, Sweden, USA and the UK (Wales). Mean prevalence was estimated for the entire period, both overall and by country, adjusted for sex and age group. Temporal trends in annual prevalence of DKA were estimated using logistic regression analysis for each country, before and after adjustment for sex, age group and ethnic minority status. RESULTS: During the study period, new-onset type 1 diabetes was diagnosed in 59,000 children (median age [interquartile range], 9.0 years [5.5-11.7]; male sex, 52.9%). The overall adjusted DKA prevalence was 29.9%, with the lowest prevalence in Sweden and Denmark and the highest in Luxembourg and Italy. The adjusted DKA prevalence significantly increased over time in Australia, Germany and the USA while it decreased in Italy. Preschool children, adolescents and children from ethnic minority groups were at highest risk of DKA at diabetes diagnosis in most countries. A significantly higher risk was also found for females in Denmark, Germany and Slovenia. CONCLUSIONS/INTERPRETATION: DKA prevalence at type 1 diabetes diagnosis varied considerably across countries, albeit it was generally high and showed a slight increase between 2006 and 2016. Increased awareness of symptoms to prevent delay in diagnosis is warranted, especially in preschool children, adolescents and children from ethnic minority groups.

The effect of patient-managed stress dosing on electrolytes and blood pressure in acute illness in children with adrenal insufficiency.

BACKGROUND: Adrenal crises (AC) are acute episodes of adrenal insufficiency (AI). Manifestations include hypotension and electrolyte disturbances. Glucocorticoid stress dosing (SD) can prevent AC progression, but its effect on physiological parameters has not been assessed in a 'real world setting'. AIMS: To assess the effect of prior self-managed glucocorticoid dose escalation on physiological markers in children with congenital adrenal hyperplasia (CAH) presenting to hospital for an acute illness. METHODS: An audit of records of all children with CAH presenting to paediatric referral hospital between 2000 and 2015. Potassium, sodium and glucose levels, and hypotension were compared between children who had and had not used SD. RESULTS: There were 321 attendances by patients with CAH and an acute illness during the study period. Any form of SD was used by 64.2% (n = 206); intramuscular (IM) hydrocortisone was used by 22.1% (n = 71) and oral only by 41.7% (n = 134). Use of SD (oral and/or IM) was associated with a significantly lower mean potassium level (4.02 ± 0.71 vs. 4.27 ± 0.79 mmol/l, P < .05). Linear regression analysis showed that age (beta: -0.04 years (95% CI -0.06, -0.02)), diarrhoea (beta: -0.41 (95% CI -0.06, -0.02)) and any form of stress dosing (oral, IM or both) (beta: -0.29 (95% CI -0.55, -0.04)) were each independently and significantly associated with potassium levels. SD was not significantly associated with sodium or glucose concentrations or with estimates of hypotension. CONCLUSION: Patient-initiated SD resulted in a significant reduction in hyperkalaemia and lowered mean potassium levels in paediatric patients with CAH but did not alter significantly sodium and glucose concentrations or incidences of hypotension.

The immunohistochemical, DNA methylation, and chromosomal copy number profile of cauda equina paraganglioma is distinct from extra-spinal paraganglioma.

Paragangliomas are neuroendocrine tumors of the autonomic nervous system that are variably clinically functional and have a potential for metastasis. Up to 40% occur in the setting of a hereditary syndrome, most commonly due to germline mutations in succinate dehydrogenase (SDHx) genes. Immunohistochemically, paragangliomas are characteristically GATA3-positive and cytokeratin-negative, with loss of SDHB expression in most hereditary cases. In contrast, the rare paragangliomas arising in the cauda equina (CEP) or filum terminale region have been shown to be hormonally silent, clinically indolent, and have variable keratin expression, suggesting these tumors may represent a separate pathologic entity. We retrospectively evaluated 17 CEPs from 11 male and 6 female patients with a median age of 38 years (range 21-82), none with a family history of neuroendocrine neoplasia. Six of the 17 tumors demonstrated prominent gangliocytic or ganglioneuromatous differentiation. By immunohistochemistry, none of the CEPs showed GATA3 positivity or loss of SDHB staining; all 17 CEPs were cytokeratin positive. Genome-wide DNA methylation profiling was performed on 12 of the tumors and compared with publicly available genome-wide DNA methylation data. Clustering analysis showed that CEPs form a distinct epigenetic group, separate from paragangliomas of extraspinal sites, pheochromocytomas, and other neuroendocrine neoplasms. Copy number analysis revealed diploid genomes in the vast majority of CEPs, whereas extraspinal paragangliomas were mostly aneuploid with recurrent trisomy 1q and monosomies of 1p, 3, and 11, none of which were present in the cohort of CEP. Together, these findings indicate that CEPs likely represent a distinct entity. Future genomic studies are needed to further elucidate the molecular pathogenesis of these tumors.

Social Desirability and Young Men's Self-Reports of Penis Size.

Previous studies demonstrate that many men have insecurities about the size of their penises, often resulting in low sexual self-esteem and sexual problems. In the present study, mean self-reported erect penis length by 130 sexually experienced college men (6.62 inches) was greater than found in previous studies in which researchers took measurements. This suggests that many of the men embellished their responses. Only 26.9% of the sexually experienced men self-reported penis lengths of less than 6 inches, while 30.8% self-reported lengths of 7 inches or more (with 10% self-reporting 8 inches or more). The correlation with Marlowe-Crowne social desirability scores was +.257 (p < .01), indicating that men with a high level of social desirability were more likely than others to self-report having a large penis.

Variations in the management of acute illness in children with congenital adrenal hyperplasia: An audit of three paediatric hospitals.

OBJECTIVE: Episodes of acute adrenal insufficiency (AI)/adrenal crises (AC) are a serious consequence of congenital adrenal hyperplasia (CAH). This study aimed to assess morbidity from acute illness in CAH and identify factors associated with use of IV hydrocortisone, admission and diagnosis of an AC. METHOD: An audit of acute illness presentations among children with CAH to paediatric hospitals in New South Wales, Australia, between 2000 and 2015. RESULTS: There were 321 acute presentations among 75 children with CAH. Two-thirds (66.7%, n = 214) of these resulted in admission and 49.2% (n = 158) of the patients received intravenous (IV) hydrocortisone. An AC was diagnosed in (9.0%). Prior to presentation, 64.2% (n = 206) had used oral stress dosing and 22.1% (n = 71) had been given intramuscular (IM) hydrocortisone. Vomiting was recorded in 61.1% (n = 196), 32.7% (n = 64) of whom had used IM hydrocortisone. Admission, AC diagnosis and use of stress dosing varied significantly between hospitals. IM use varied from 7.0% in one metropolitan hospital to 45.8% in the regional hospital. Children aged up to 12 months had the lowest levels of stress dosing and IV hydrocortisone administration. Higher numbers of prior hospital attendances for acute illness were associated with increased use of IM hydrocortisone. CONCLUSION: Prehospital and in-hospital management of children with CAH can vary between health services. Children under 12 months have lower levels of stress dosing prior to hospital than other age groups. Experience with acute episodes improves self-management of CAH in the context of acute illness in educated patient populations.

Young children with type 1 diabetes can achieve glycemic targets without hypoglycemia: Results of a novel intensive diabetes management program.

BACKGROUND: Young children with type 1 diabetes (T1D) present unique challenges for intensive diabetes management. We describe an intensive diabetes program adapted for young children and compare glycemic control, anthropometry, dietary practices and insulin regimens before and after implementation. METHODS: Cross sectional data from children with T1D aged ≥0.5 to <7.0 years attending the John Hunter Children's Hospital (JHCH), Australia in 2004, 2010 and 2016 were compared. Outcome measures were glycemic control assessed by hemoglobin A1c (HbA1c ); severe hypoglycemia episodes; body mass index standard deviation scores (BMI-SDS); diabetes ketoacidosis (DKA) episodes; and insulin regimen-twice daily injections, multiple daily injections, or continuous subcutaneous insulin infusion. RESULTS: Mean HbA1c declined by 12 mmol/mol over the study period (P < .01). The proportion of children achieving a mean HbA1c < 58 mmol/mol increased significantly from 31% in 2004 to 64% in 2010 (P < .01), and from 64% in 2010 to 83% in 2016 (P = .04). The mean BMI-SDS was significantly lower in 2010 when compared with 2004 (P<.01); however, this trend plateaued between 2010 and 2016 (P = .97). Severe hypoglycemia and DKA occurred infrequently. The prevalence of overweight or obesity increased from 2010 to 2016 (P = .03). CONCLUSIONS: The JHCH intensive diabetes management program has resulted in 83% of young children in 2016 achieving target glycemia without an increase in severe hypoglycemia or DKA. Overweight remains a challenge in this population warranting action to reduce weight and protect these children from future obesity-related health risks.

C50Cl10, a planar aromatic fullerene. Computational study of 13C-NMR chemical shift anisotropy patterns and aromatic properties.

The isolated-pentagon-rule (IPR) is a prime determinant of fullerene stabilization accounting for the difficult isolation of hollow Cn (n < 60) species. In this connection, the isolation and structural characterization of D5h-C50Cl10 as an IPR-violating fullerene are of interest owing to the study of factors providing further stability. Herein, we use DFT calculations to explore its aromatic behavior. In this connection the C50Cl10 structure is considered as a fullerene displaying a planar-aromatic character provided by the face-to-face disposition of two IPR structural motifs, mediated by ten exobonded sp3-carbons. In addition, the D5h-C50Br10 counterpart appears to be another promising structure as the target for explorative synthesis. Owing to the curvature of its IPR motif, an interesting variation in the 13C-NMR patterns relative to corannulene is described, where the relation between CI and CII signals is useful to evaluate the degree of the curvature of the π-surface. The charge distribution of C50Cl10 reveals a more electron-deficient IPR dome in comparison to C60, envisaging an enhanced chemistry related to bare fullerenes. In addition, the -Cl and -Br exobonded atoms provide effective σ-holes, suggesting such oblate fullerenes as interesting two-dimensional five-fold symmetric synthons useful for the formation of supramolecular species. Hence, an interesting chemistry and supramolecular array derivatives are potential applications to be further explored towards the development of novel nano-devices.

High Useful Yield and Isotopic Analysis of Uranium by Resonance Ionization Mass Spectrometry.

Useful yields from resonance ionization mass spectrometry can be extremely high compared to other mass spectrometry techniques, but uranium analysis shows strong matrix effects arising from the tendency of uranium to form strongly bound oxide molecules that do not dissociate appreciably on energetic ion bombardment. We demonstrate a useful yield of 24% for metallic uranium. Modeling the laser ionization and ion transmission processes shows that the high useful yield is attributable to a high ion fraction achieved by resonance ionization. We quantify the reduction of uranium oxide surface layers by Ar+ and Ga+ sputtering. The useful yield for uranium atoms from a uranium dioxide matrix is 0.4% and rises to 2% when the surface is in sputter equilibrium with the ion beam. The lower useful yield from the oxide is almost entirely due to uranium oxide molecules reducing the neutral atom content of the sputtered flux. We demonstrate rapid isotopic analysis of solid uranium oxide at a precision of <0.5% relative standard deviation using relatively broadband lasers to mitigate spectroscopic fractionation.