Observation of the Fractional Quantum Hall Effect in Graphene

When electrons are confined in two dimensions and subjected to strong magnetic fields, the Coulomb interactions between them become dominant and can lead to novel states of matter such as fractional quantum Hall liquids. In these liquids electrons linked to magnetic flux quanta form complex composite quasipartices, which are manifested in the quantization of the Hall conductivity as rational fractions of the conductance quantum. The recent experimental discovery of an anomalous integer quantum Hall effect in graphene has opened up a new avenue in the study of correlated 2D electronic systems, in which the interacting electron wavefunctions are those of massless chiral fermions. However, due to the prevailing disorder, graphene has thus far exhibited only weak signatures of correlated electron phenomena, despite concerted experimental efforts and intense theoretical interest. Here, we report the observation of the fractional quantum Hall effect in ultraclean suspended graphene, supporting the existence of strongly correlated electron states in the presence of a magnetic field. In addition, at low carrier density graphene becomes an insulator with an energy gap tunable by magnetic field. These newly discovered quantum states offer the opportunity to study a new state of matter of strongly correlated Dirac fermions in the presence of large magnetic fields

Diagnostic comparison of malaria infection in peripheral blood, placental blood and placental biopsies in Cameroonian parturient women

<p>Abstract</p> <p>Background</p> <p>In sub-Saharan Africa, <it>Plasmodium falciparum </it>malaria in pregnancy presents an enormous diagnostic challenge. The epidemiological and clinical relevance of the different types of malaria diagnosis as well as risk factors associated with malaria infection at delivery were investigated.</p> <p>Method</p> <p>In a cross-sectional survey, 306 women reporting for delivery in the Mutenegene maternity clinic, Fako division, South West province, Cameroon were screened for <it>P. falciparum </it>in peripheral blood, placental blood and placental tissue sections by microscopy. Information relating to the use of intermittent preventive treatment in pregnancy with sulphadoxine/pyrimethamine, history of fever attack, infant birth weights and maternal anaemia were recorded.</p> <p>Results</p> <p>Among these women, <it>P. falciparum </it>infection was detected in 5.6%, 25.5% and 60.5% of the cases in peripheral blood, placental blood and placental histological sections respectively. Placental histology was more sensitive (97.4%) than placental blood film (41.5%) and peripheral blood (8.0%) microscopy. In multivariate analysis, age (≤ 20 years old) (OR = 4.61, 95% CI = 1.47 – 14.70), history of fever attack (OR = 2.98, 95% CI = 1.58 – 5.73) were significant risk factors associated with microscopically detected parasitaemia. The use of ≥ 2 SP doses (OR = 0.18, 95% CI = 0.06 – 0.52) was associated with a significant reduction in the prevalence of microscopic parasitaemia at delivery. Age (>20 years) (OR = 0.34, 95% CI = 0.15 – 0.75) was the only significant risk factor associated with parasitaemia diagnosed by histology only in univariate analysis. Microscopic parasitaemia (OR = 2.74, 95% CI = 1.33–5.62) was a significant risk factor for maternal anaemia at delivery, but neither infection detected by histology only, nor past infection were associated with increased risk of anaemia.</p> <p>Conclusion</p> <p>Placenta histological examination was the most sensitive indicator of malaria infection at delivery. Microscopically detected parasitaemia was associated with increased risk of maternal anaemia at delivery, but not low-grade parasitaemia detected by placental histology only.</p

Altered networks in bothersome tinnitus: a functional connectivity study

<p>Abstract</p> <p>Background</p> <p>The objective was to examine functional connectivity linked to the auditory system in patients with bothersome tinnitus. Activity was low frequency (< 0.1 Hz), spontaneous blood oxygenation level-dependent (BOLD) responses at rest. The question was whether the experience of chronic bothersome tinnitus induced changes in synaptic efficacy between co-activated components. Functional connectivity for seed regions in auditory, visual, attention, and control networks was computed across all 2 mm³brain volumes in 17 patients with moderate-severe bothersome tinnitus (<it>Tinnitus Handicap Index: average </it>53.5 ± 3.6 (range 38-76)) and 17 age-matched controls.</p> <p>Results</p> <p>In bothersome tinnitus, negative correlations reciprocally characterized functional connectivity between auditory and occipital/visual cortex. Negative correlations indicate that when BOLD response magnitudes increased in auditory or visual cortex they decreased in the linked visual or auditory cortex, suggesting reciprocally phase reversed activity between functionally connected locations in tinnitus. Both groups showed similar connectivity with positive correlations within the auditory network. Connectivity for primary visual cortex in tinnitus included extensive negative correlations in the ventral attention temporoparietal junction and in the inferior frontal gyrus and rostral insula - executive control network components. Rostral insula and inferior frontal gyrus connectivity in tinnitus also showed greater negative correlations in occipital cortex.</p> <p>Conclusions</p> <p>These results imply that in bothersome tinnitus there is dissociation between activity in auditory cortex and visual, attention and control networks. The reciprocal negative correlations in connectivity between these networks might be maladaptive or reflect adaptations to reduce phantom noise salience and conflict with attention to non-auditory tasks.</p

A Randomized Controlled Pilot Trial of Azithromycin or Artesunate Added to Sulfadoxine-Pyrimethamine as Treatment for Malaria in Pregnant Women

New anti-malarial regimens are urgently needed in sub-Saharan Africa because of the increase in drug resistance. We investigated the safety and efficacy of azithromycin or artesunate combined with sulfadoxine-pyrimethamine used for treatment of malaria in pregnant women in Blantyre, Malawi.This was a randomized open-label clinical trial, conducted at two rural health centers in Blantyre district, Malawi. A total of 141 pregnant women with uncomplicated Plasmodium falciparum malaria were recruited and randomly allocated to 3 treatment groups: sulfadoxine-pyrimethamine (SP; 3 tablets, 500 mg sulfadoxine and 25 mg pyrimethamine per tablet); SP plus azithromycin (1 g/dayx2 days); or SP plus artesunate (200 mg/dayx3 days). Women received two doses administered at least 4 weeks apart. Heteroduplex tracking assays were performed to distinguish recrudescence from new infections. Main outcome measures were incidence of adverse outcomes, parasite and fever clearance times and recrudescence rates. All treatment regimens were well tolerated. Two women vomited soon after ingesting azithromycin. The parasite clearance time was significantly faster in the SP-artesunate group. Recrudescent episodes of malaria were less frequent with SP-azithromycin [Hazard Ratio 0.19 (95% confidence interval 0.06 to 0.63)] and SP-artesunate [Hazard Ratio 0.25 (95% confidence interval 0.10 to 0.65)] compared with SP monotherapy. With one exception (an abortion in the SP-azithromycin group), all adverse pregnancy outcomes could be attributed to known infectious or obstetrical causes. Because of the small sample size, the effect on birth outcomes, maternal malaria or maternal anemia could not be evaluated.Both SP-artesunate and SP-azithromycin appeared to be safe, well tolerated and efficacious for the treatment of malaria during pregnancy. A larger study is needed to determine their safety and efficacy in preventing poor birth outcomes.ClinialTrials.gov NCT00287300

High exposures to bioactivated cyclophosphamide are related to the occurrence of veno-occlusive disease of the liver following high-dose chemotherapy

We investigated whether the occurrence of veno-occlusive disease of the liver (VOD) may be associated with individual variations in the pharmacokinetics of high-dose cyclophosphamide. Patients received single or multiple courses of cyclophosphamide (1000 or 1500 mg m−2 day−1), thiotepa (80 or 120 mg m−2 day−1) and carboplatin (265–400 mg m−2 day−1) (CTC) for 4 consecutive days. The area under the plasma concentration–time curves (AUCs) were calculated for cyclophosphamide and its activated metabolites 4-hydroxycyclophosphamide and phosphoramide mustard based on multiple blood samples. Possible relationships between the AUCs and the occurrence of VOD were studied. A total of 59 patients (115 courses) were included. Four patients experienced VOD after a second CTC course. The first-course AUC of 4-hydroxycyclophosphamide (P=0.003) but not of phosphoramide mustard (P=0.101) appeared to be predictive of the occurrence of VOD after multiple courses. High exposures to bioactivated cyclophosphamide may lead to increased organ toxicity

Hookworm-Related Anaemia among Pregnant Women: A Systematic Review

Anaemia affects large numbers of pregnant women in developing countries and increases their risk of dying during pregnancy and delivering low birth weight babies, who in turn are at increased risk of dying. Human hookworm infection has long been recognized among the major causes of anaemia in poor communities, but understanding of the benefits of the management of hookworm infection in pregnancy has lagged behind the other major causes of maternal anaemia. Low coverage of anthelmintic treatment in maternal health programmes in many countries has been the result. After systematically reviewing the available literature we observed that increasing hookworm infection intensity is associated with lower haemoglobin levels in pregnant women. We also estimate that between a quarter and a third of pregnant women in sub-Saharan Africa are infected with hookworm and at risk of preventable hookworm-related anaemia. However, all identified intervention studies showed a benefit of deworming for maternal or child health and we argue that increased efforts should be made to increase the coverage of anthelmintic treatment among pregnant women

Affinity Inequality among Serum Antibodies That Originate in Lymphoid Germinal Centers

Upon natural infection with pathogens or vaccination, antibodies are produced by a process called affinity maturation. As affinity maturation ensues, average affinity values between an antibody and ligand increase with time. Purified antibodies isolated from serum are invariably heterogeneous with respect to their affinity for the ligands they bind, whether macromolecular antigens or haptens (low molecular weight approximations of epitopes on antigens). However, less is known about how the extent of this heterogeneity evolves with time during affinity maturation. To shed light on this issue, we have taken advantage of previously published data from Eisen and Siskind (1964). Using the ratio of the strongest to the weakest binding subsets as a metric of heterogeneity (or affinity inequality), we analyzed antibodies isolated from individual serum samples. The ratios were initially as high as 50-fold, and decreased over a few weeks after a single injection of small antigen doses to around unity. This decrease in the effective heterogeneity of antibody affinities with time is consistent with Darwinian evolution in the strong selection limit. By contrast, neither the average affinity nor the heterogeneity evolves much with time for high doses of antigen, as competition between clones of the same affinity is minimal.Ragon Institute of MGH, MIT and HarvardSamsung Scholarship FoundationNational Science Foundation (U.S.). Graduate Research Fellowship (Grant 1122374

Placental Malaria is associated with reduced early life weight development of affected children independent of low birth weight

<p>Abstract</p> <p>Background</p> <p>Infection with <it>Plasmodium falciparum </it>during pregnancy contributes substantially to the disease burden in both mothers and offspring. Placental malaria may lead to intrauterine growth restriction or preterm delivery resulting in low birth weight (LBW), which, in general, is associated with increased infant morbidity and mortality. However, little is known about the possible direct impact of the specific disease processes occurring in PM on longer term outcomes such as subsequent retarded growth development independent of LBW.</p> <p>Methods</p> <p>In an existing West-African cohort, 783 healthy infants with a birth weight of at least 2,000 g were followed up during their first year of life. The aim of the study was to investigate if <it>Plasmodium falciparum </it>infection of the placenta, assessed by placental histology, has an impact on several anthropometric parameters, measured at birth and after three, six and 12 months using generalized estimating equations models adjusting for moderate low birth weight.</p> <p>Results</p> <p>Independent of LBW, first to third born infants who were exposed to either past, chronic or acute placental malaria during pregnancy had significantly lower weight-for-age (-0.43, 95% CI: -0.80;-0.07), weight-for-length (-0.47, 95% CI: -0.84; -0.10) and BMI-for-age z-scores (-0.57, 95% CI: -0.84; -0.10) compared to infants born to mothers who were not diagnosed with placental malaria (p = 0.019, 0.013, and 0.012, respectively). Interestingly, the longitudinal data on histology-based diagnosis of PM also document a sharp decline of PM prevalence in the Sukuta cohort from 16.5% in 2002 to 5.4% in 2004.</p> <p>Conclusions</p> <p>It was demonstrated that PM has a negative impact on the infant's subsequent weight development that is independent of LBW, suggesting that the longer term effects of PM have been underestimated, even in areas where malaria transmission is declining.</p

Abstract Reasoning and Friendship in High Functioning Preadolescents with Autism Spectrum Disorders

To investigate the relationship between cognitive and social functioning, 20 Israeli individuals with HFASD aged 8–12 and 22 age, maternal education, and receptive vocabulary–matched preadolescents with typical development (TYP) came to the lab with a close friend. Measures of abstract reasoning, friendship quality, and dyadic interaction during a play session were obtained. As hypothesized, individuals with HFASD were significantly impaired in abstract reasoning, and there were significant group differences in friend and observer reports of friendship quality. There also was consistency in reports between friends. Two factors—“relationship appearance” and “relationship quality” described positive aspects of the relationships. Disability status and age related to relationship appearance. Proband abstract reasoning was related to relationship quality