Hofstadter's butterfly and the fractal quantum Hall effect in moiré superlattices.

Electrons moving through a spatially periodic lattice potential develop a quantized energy spectrum consisting of discrete Bloch bands. In two dimensions, electrons moving through a magnetic field also develop a quantized energy spectrum, consisting of highly degenerate Landau energy levels. When subject to both a magnetic field and a periodic electrostatic potential, two-dimensional systems of electrons exhibit a self-similar recursive energy spectrum. Known as Hofstadter's butterfly, this complex spectrum results from an interplay between the characteristic lengths associated with the two quantizing fields, and is one of the first quantum fractals discovered in physics. In the decades since its prediction, experimental attempts to study this effect have been limited by difficulties in reconciling the two length scales. Typical atomic lattices (with periodicities of less than one nanometre) require unfeasibly large magnetic fields to reach the commensurability condition, and in artificially engineered structures (with periodicities greater than about 100 nanometres) the corresponding fields are too small to overcome disorder completely. Here we demonstrate that moiré superlattices arising in bilayer graphene coupled to hexagonal boron nitride provide a periodic modulation with ideal length scales of the order of ten nanometres, enabling unprecedented experimental access to the fractal spectrum. We confirm that quantum Hall features associated with the fractal gaps are described by two integer topological quantum numbers, and report evidence of their recursive structure. Observation of a Hofstadter spectrum in bilayer graphene means that it is possible to investigate emergent behaviour within a fractal energy landscape in a system with tunable internal degrees of freedom.

Landau level spectroscopy of electron-electron interactions in graphene.

We present magneto-Raman scattering studies of electronic inter-Landau level excitations in quasineutral graphene samples with different strengths of Coulomb interaction. The band velocity associated with these excitations is found to depend on the dielectric environment, on the index of Landau level involved, and to vary as a function of the magnetic field. This contradicts the single-particle picture of noninteracting massless Dirac electrons but is accounted for by theory when the effect of electron-electron interaction is taken into account. Raman active, zero-momentum inter-Landau level excitations in graphene are sensitive to electron-electron interactions due to the nonapplicability of the Kohn theorem in this system, with a clearly nonparabolic dispersion relation.

Project CAPE: a high-fidelity, in situ simulation program to increase Critical Access Hospital Emergency Department provider comfort with seriously ill pediatric patients.

OBJECTIVES: Variation exists between the qualities of emergency department (ED) care provided to urban versus rural pediatric patients. We implemented a pediatric simulation program in the Critical Access Hospital (CAH) ED setting and evaluated whether this training would increase provider comfort with seriously ill children. METHODS: Five CAH hospitals conducted 6 scenarios for 12 months. Baseline surveys assessed ED staff exposure to and comfort with children. Surveys were repeated after 6 and 12 months. Respondents' answers were matched longitudinally. Changes in responses over time were analyzed using paired t tests for continuous variables. Changes in frequencies and percentages of categorical variables over time were analyzed using χ test. Scenario participants completed an additional survey at the end of each simulation. RESULTS: The baseline survey was completed by 104 of 150 eligible participants, giving a 71% response rate. Fifty-eight percent completed at least 1 additional survey. On survey 1, mean provider comfort score for procedures was 69 (0-100 point scale). Scores increased 6 points from surveys 1 to 2 and a total of 6.5 points from surveys 1 to 3 (P < 0.05).One hundred fifty postscenario surveys were completed. Of the providers, 83.7% believed that scenario participation increased their comfort with children. One hundred percent of the providers in month 12 felt that they would benefit from additional scenarios. CONCLUSIONS: An in situ pediatric simulation program can be implemented effectively in CAH EDs and results in increased comfort with pediatric patients. Such a program could be used as the core feature of a CAH education program aimed at improving the quality of pediatric emergency services provided at these safety net institutions.

Photonic crystal for graphene plasmons.

Photonic crystals are commonly implemented in media with periodically varying optical properties. Photonic crystals enable exquisite control of light propagation in integrated optical circuits, and also emulate advanced physical concepts. However, common photonic crystals are unfit for in-operando on/off controls. We overcome this limitation and demonstrate a broadly tunable two-dimensional photonic crystal for surface plasmon polaritons. Our platform consists of a continuous graphene monolayer integrated in a back-gated platform with nano-structured gate insulators. Infrared nano-imaging reveals the formation of a photonic bandgap and strong modulation of the local plasmonic density of states that can be turned on/off or gradually tuned by the applied gate voltage. We also implement an artificial domain wall which supports highly confined one-dimensional plasmonic modes. Our electrostatically-tunable photonic crystals are derived from standard metal oxide semiconductor field effect transistor technology and pave a way for practical on-chip light manipulation.

Nutritional aspects of women strength athletes.

Strength training elicits sports related and health benefits for both men and women. Although sexual dimorphism is observed in exercise metabolism, there is little information outlining the specific nutritional needs of women strength athletes. Many women athletes restrict energy intake, specifically fat consumption, in order to modify body composition, but this nutritional practice is often counter-productive. Compared to men, women appear to be less reliant on glycogen during exercise and less responsive to carbohydrate mediated glycogen synthesis during recovery. Female strength athletes may require more protein than their sedentary and endurance training counterparts to attain positive nitrogen balance and promote protein synthesis. Therefore, women strength athletes should put less emphasis on a very high carbohydrate intake and more emphasis on quality protein and fat consumption in the context of energy balance to enhance adaptations to training and improve general health. Attention to timing of nutrient ingestion, macronutrient quality, and dietary supplementation (for example, creatine) are briefly discussed as important components of a nutritionally adequate and effective strength training diet for women.

Multiple measures of motor lateralization in human primates (Homo sapiens).

Laterality was assessed in 100 human (Homo sapiens) subjects through the use of five measures of motoric behavior in three categories: locomotor, manual, postural. Locomotor measures included leading limb for initiation of walking and whole-body turning. Performance and questionnaire measures were used to assess lateral hand bias. Postural bias was assessed as the weight distribution in quiet standing. Population-level biases on the manual and leading limb measures were to the right; on posture and turning, to the left. Locomotor measures were found to be altered by marching experience. Only the manual measures were correlated. We compare the results with those of nonhuman primate studies that have used similar measures and discuss some patterns of laterality common to human and nonhuman primates.

Multiple measures of hand-use lateralization in the ring-tailed lemur (Lemur catta).

Evaluated a free-ranging matriline of 13 ring-tailed lemurs (Lemur catta) from videotaped records for lateralized hand use with 2 tasks and 4 measures: food reaching, feeding posture, duration of food holding, and manipulation of food between mouth and hand while eating. Binomial z scores determined 7 lemurs to be left preferent in reaching, 3 right, and 3 ambipreferent. Ideographic analyses suggested possible sex-linked and early experience twin effects. When compared to right and ambipreferent lemurs, left reach preferent lemurs used the left hand more but bimanuals grasped less in food holding and also engaged in less hand-mouth food manipulation. The tendency to manipulate food was not correlated with bimanual holding but was inversely related to left hand holding and directly related to right hand holding. These patterns are discussed as possible precursors of human bimanual manipulation.

Posturally related variations in the hand preferences of the ruffed lemur (Varecia variegata variegata).

The hand preferences of 5 semi-free-ranging black-and-white ruffed lemurs were assessed by using three distinct testing procedures. Testing conditions varied in the extent to which they required animals to make a whole body postural adjustment prior to making a reach. Minimal bodily adjustment was necessary for free foraging, whereas discrete food presentations on land (DFP-land) and in a moat (DFP-moat) promoted a gross reorientation of the animal's entire body. In the DFP-moat condition 4 animals exhibited exclusive use of the left hand, and only 1 of 515 reaches was made with the right hand. Similarly, all 5 animals showed a pronounced left hand preference in the DFP-land condition. The free-foraging condition revealed a hand preference for only 1 of the 5 subjects, and that preference was weak in comparison with those measured in the other two test conditions. These findings indicate that whole body postural adjustments critically influenced the expression of hand preference and should be taken into consideration in future studies of primate hand preferences.

Cholesterolaemic influence of palmitic acid in the sn-1, 3 v. the sn-2 position with high or low dietary linoleic acid in healthy young men.

Healthy young men were fed four diets for 2 weeks each providing natural fats containing palmitic acid (16 : 0) predominantly in the sn-1, 3 position of dietary TAG or containing 16 : 0 predominantly in the sn-2 position with low or high levels of linoleic acid (18 : 2n-6). Two treatments supplied 16 : 0 in the sn-1, 3 positions from palmstearin with low (3 % energy) or high (>7 % energy) 18 : 2n-6 and two treatments supplied 16 : 0 in the sn-2 position from lard with high or low levels of 18 : 2n-6. Diets contained 30-35 % energy as fat, 7-11 % energy as 16 : 0 and moderate levels of cholesterol. Fasting serum cholesterol and lipoprotein concentrations were measured. Cholesterol fractional synthesis rate (FSR) was determined by 2H incorporation. Diets providing 16 : 0 in the sn-2 position resulted in lower fasting serum total cholesterol (TC) and a lower TC:HDL ratio than diets providing 16 : 0 in the sn-1, 3 positions. Diets with high levels of 18 : 2n-6 significantly decreased the TC:HDL ratio, reaffirming the well-known cholesterol-reducing effect of 18 : 2n-6. A lower non-esterified cholesterol FSR was observed with low dietary levels of 18 : 2n-6. No differences between dietary treatments were found for serum HDL-cholesterol, LDL-cholesterol or TAG. It is concluded that dietary fats containing 16 : 0 in the sn-2 position may result in slightly lower fasting TC than diets providing 16 : 0 in the sn-1, 3 positions, while the level of n-6 polyunsaturated fat influences endogenous cholesterol synthesis.

Characteristics of life events during adolescence.

Two studies of the characteristics of life events during adolescence are reported. In the first, open-ended reports of major life events and daily events were obtained from early, middle, and late adolescents. Analyses of the frequency of past events perceived as positive versus negative revealed effects for type of event (major vs. daily), age, and gender. In contrast, anticipated events were perceived similarly across age and gender. The second study examined judgments by older adolescents of the valence, type, and domain of life events. Consensus regarding these characteristics was achieved on only a small portion of events. The implications of these findings for the measurement of life events during adolescence are highlighted.

Primary neonatal hyperparathyroidism: a devastating neurodevelopmental disorder if left untreated.

We describe a 29-year-old male with untreated primary neonatal hyperparathyroidism. Hypotonia, poor feeding, failure to thrive, and developmental delay were noted in early infancy and in incidental serum calcium of 3.8 mmol/L was dismissed as a laboratory error. Childhood was characterized by profound muscle wasting and progressive spastic quadriparesis. Distinctive skeletal deformities, facial dysmorphism, and perichondral calcifications are now evident in adulthood. Elevated serum calcium (range: 2.7-3.3 mM; normal less than 2.7 mM), serum immunoreactive parathyroid hormone (range: 1,405-1,817 pg/mL; normal 50-140 pg/mL), and markedly decreased urinary calcium excretion (0.04 mumol/dL glomerular filtrate; normal greater than 25) suggested the diagnosis of primary neonatal hyperparathyroidism. This was supported by evidence of hypocalciuric hypercalcemia--the autosomal dominant carrier state--in both the parents. Our case illustrates the profound neurodevelopmental deficits arising from sustained hypercalcemia in infancy and childhood. Although this disorder is not lethal, it should be considered a neonatal emergency, since surgical parathyroidectomy can result in cure.

Quantifying the MB isoenzyme of creatine kinase with the Abbott "IMx" immunoassay analyzer.

In this two-step automated assay of the MB isoenzyme of creatine kinase (CK-MB), developed for the Abbott "IMx" immunoassay analyzer, monoclonal anti-CK-MB antibody immobilized onto latex microparticles and polyclonal anti-CK-MM antibody coupled to alkaline phosphatase are used. Within-run CVs ranged from 3.9% to 9.0%, between-run CVs from 0.0% to 5.6%, and the sensitivity was 0.2 microgram/L. Twenty-four results can be obtained in about 37 min. Analytical recovery of CK-MB added to human serum or plasma ranged from 89% to 109%. Icteric, lipemic, or hemolyzed samples did not interfere with CK-MB recovery. Cross-reactivity with CK-MM and CK-BB was 0.012% and 0.001%, respectively. The normal reference interval was 0-5 micrograms/L. IMx CK-MB results correlated well with CK-MB enzyme activity as determined by electrophoresis (n = 203; r = 0.97; slope = 0.90; y-intercept = -4.29) and with commercial immunoassays. We think that this assay will be useful for confirmation of acute myocardial infarction, both in critical-care units and in the clinical laboratory.

Fully automated assay of glycohemoglobin with the Abbott IMx analyzer: novel approaches for separation and detection.

We describe a novel assay for measuring glycohemoglobin directly from anticoagulated whole blood with the Abbott IMx analyzer. The glycohemoglobin is labeled with a soluble polyanionic affinity reagent and the anionic complex is then captured with a cationic solid-phase matrix. Glycohemoglobin is quantified by measuring the quenching by heme of the static fluorescence from an added fluorophore. The assay is standardized to report both percent total glycohemoglobin (%GHb) and percent hemoglobin A1c (%HbA1c). Glucose, bilirubin, triglycerides, labile fraction, and hemoglobin variants do not interfere in the assay. Within- and between-run CVs are approximately 4-5%, with total CVs of approximately 6.5%. Highly significant linear correlations (r > 0.97) were obtained in comparison studies with two major assay methodologies. The time to obtain one result is approximately 10 min (including assay of a control), 56 min for 22 results. We describe the development, standardization, and validation of this new method.

A new variant of spondylometaphyseal dysplasia with autosomal dominant mode of inheritance.

Clinical and radiographic evaluation of an infant boy and his father revealed findings suggesting a new variant of spondylometaphyseal dysplasia with an apparently autosomal dominant mode of inheritance. The main clinical findings included short stature and marked ligamentous laxity in the infant. X-ray findings included severe and peculiar multiple metaphyseal involvement and striking vertebral undermineralisation in the infant, and platyspondyly in the father. However, all the epiphyses were normal. Laboratory studies were essentially normal except for an extremely raised serum alkaline phosphatase in the infant. The uniqueness of these findings suggests a new variant of the spondylometaphyseal dysplasias, distinct from the cases described initially by Kozlowski et al and subsequent investigators.