Magnetic Anisotropy in the Molecular Complex V15

We apply degenerate perturbation theory to investigate the effects of magnetic anisotropy in the magnetic molecule V15. Magnetic anisotropy is introduced via Dzyaloshinskii-Moriya (DM) interaction in the full Hilbert space of the system. Our model provides an explanation for the rounding of transitions in the magnetization as a function of applied field at low temperature, from which an estimate for the DM interaction is found. We find that the calculated energy differences of the lowest energy states are consistent with the available data. Our model also offers a novel explanation for the hysteretic nature of the time-dependent magnetization data.Comment: Final versio

Magnetothermal properties of molecule-based materials

We critically review recent results obtained by studying the low-temperature specific heat of some of the most popular molecular magnets. Perspectives of this field are discussed as well.Comment: 12 pages text + 14 pages figures, Submitted as "feature article" to Journal of Materials Chemistr

Quantum computing with antiferromagnetic spin clusters

We show that a wide range of spin clusters with antiferromagnetic intracluster exchange interaction allows one to define a qubit. For these spin cluster qubits, initialization, quantum gate operation, and readout are possible using the same techniques as for single spins. Quantum gate operation for the spin cluster qubit does not require control over the intracluster exchange interaction. Electric and magnetic fields necessary to effect quantum gates need only be controlled on the length scale of the spin cluster rather than the scale for a single spin. Here, we calculate the energy gap separating the logical qubit states from the next excited state and the matrix elements which determine quantum gate operation times. We discuss spin cluster qubits formed by one- and two-dimensional arrays of s=1/2 spins as well as clusters formed by spins s>1/2. We illustrate the advantages of spin cluster qubits for various suggested implementations of spin qubits and analyze the scaling of decoherence time with spin cluster size.Comment: 15 pages, 7 figures; minor change

A conserved metabolic signature associated with response to fast-acting anti-malarial agents

Characterizing the mode of action of anti-malarial compounds that emerge from high-throughput phenotypic screens is central to understanding how parasite resistance to these drugs can emerge. Here, we have employed untargeted metabolomics to inform on the mechanism of action of anti-malarial leads with different speed of kill profiles being developed by the Novartis Institute of Tropical Diseases (NITD). Time-resolved global changes in malaria parasite metabolite profiles upon drug treatment were quantified using liquid chromatography-based mass spectrometry and compared to untreated controls. Using this approach, we confirmed previously reported metabolomics profiles of the fast-killing (2.5 h) drug dihydroartemisinin (DHA) and the slower killing atovaquone. A slow-acting anti-malarial lead from NITD of imidazolopiperazine (IZP) class, GNF179, elicited little or no discernable metabolic change in malaria parasites in the same 2.5-h window of drug exposure. In contrast, fast-killing drugs, DHA and the spiroindolone (NITD246), elicited similar metabolomic profiles both in terms of kinetics and content. DHA and NITD246 induced peptide losses consistent with disruption of hemoglobin catabolism and also interfered with the pyrimidine biosynthesis pathway. Two members of the recently described class of anti-malarial agents of the 5-aryl-2-amino-imidazothiadiazole class also exhibited a fast-acting profile that featured peptide losses indicative of disrupted hemoglobin catabolism. Our screen demonstrates that structurally unrelated, fast-acting anti-malarial compounds generate similar biochemical signatures in Plasmodium pointing to a common mechanism associated with rapid parasite death. These profiles may be used to identify and possibly predict the mode of action of other fast-acting drug candidates

Serum Ferritin in Pregnancy: The Effect of Iron Supplementation

Summary: Serum ferritin concentration was measured in 196 pregnant women at different stages of gestation. The effect of supplemental iron during pregnancy on ferritin concentration was also studied. The mean serum ferritin concentration in the first 20 weeks of pregnancy was within the normal range for females, but in 13% of patients presenting before the 13th week of gestation the concentrations were in the range of iron deficiency. The values fell in all patients by the 28th week of gestation, but the fall was significantly greater in those subjects not taking supplemental iron and in these the levels were in the range of iron deficiency by the 35th week. By the 6th postpartum week, values had risen in all patients whether iron supplemented or not, but the rise was significantly less in the non‐supplemented group. Serum ferritin appears to provide a useful assessment of body iron stores during pregnancy, particularly in an iron deficiency state not severe enough to produce frank microcytosis, hypochromia, or anaemia

Sexual behaviour in early adolescence: a cross-national comparison of Australian and United States youth

Objective: This study used matched samples from schools in the states of Victoria and Washington to compare sexual behaviour in early adolescence. It was hypothesised that the contrasting dominant policy objectives of harm minimisation in Australia and abstinence in the USA would result in state differences for markers of sexual risk, mirroring prior cross-national findings in substance use. Method: A two-stage cluster sampling approach was used to recruit students from the two states. Self-reported sexual behaviour was examined for 1,596 students in annual surveys from Grade 7 in 2002 to Grade 9 in 2004. Prevalence estimates were derived for each measure of sexual behaviour, and comparisons were made between gender groups in each state. Results: State differences were found for girls\u27 first sex, with significantly more girls in Washington than Victoria having had sex by Grade 7. By Grade 9, significantly more girls in Victoria reported sex in the last year and more sexual partners than girls in Washington. A large proportion of Grade 9 students across both states reported inconsistent contraception use. Conclusions: Contradicting the abstinence policy objective, first sex by Grade 7 was more prevalent in Washington than in Victoria. While sexual behaviour was more prevalent in Grade 9 in Victoria, the sexually active showed no clear cross-national differences in markers of risk such as contraception use and pregnancy outcomes. Findings demonstrate few cross-national differences in adolescent sexual behaviour despite the different policy contexts of Victoria and Washington

Probiotics and Human Milk Differentially Influence the Gut Microbiome and NEC Incidence in Preterm Pigs.

Necrotizing enterocolitis (NEC) is the leading cause of death caused by gastrointestinal disease in preterm infants. Major risk factors include prematurity, formula feeding, and gut microbial colonization. Microbes have been linked to NEC, yet there is no evidence of causal species, and select probiotics have been shown to reduce NEC incidence in infants. In this study, we evaluated the effect of the probiotic Bifidobacterium longum subsp. infantis (BL. infantis), alone and in combination with a human milk oligosaccharide (HMO)-sialylactose (3'SL)-on the microbiome, and the incidence of NEC in preterm piglets fed an infant formula diet. We studied 50 preterm piglets randomized between 5 treatments: (1) Preterm infant formula, (2) Donor human milk (DHM), (3) Infant formula + 3'SL, (4) Infant formula + BL. infantis, and (5) Infant formula and BL. infantis + 3'SL. NEC incidence and severity were assessed through the evaluation of tissue from all the segments of the GI tract. The gut microbiota composition was assessed both daily and terminally through 16S and whole-genome sequencing (WGS) of rectal stool samples and intestinal contents. Dietary BL. infantis and 3'SL supplementation had no effect, yet DHM significantly reduced the incidence of NEC. The abundance of BL. infantis in the gut contents negatively correlated with disease severity. Clostridium sensu stricto 1 and Clostridium perfringens were significantly more abundant in NEC and positively correlated with disease severity. Our results suggest that pre- and probiotics are not sufficient for protection from NEC in an exclusively formula-based diet. The results highlight the differences in microbial species positively associated with both diet and NEC incidence

A conserved metabolic signature associated with response to fast-acting anti-malarial agents

In malaria drug discovery, understanding the mode of action of lead compounds is important as it helps in predicting the potential emergence of drug resistance in the field when these drugs are eventually deployed. In this study, we have employed metabolomics technologies to characterize the potential targets of anti-malarial drug candidates in the developmental pipeline at NITD. We show that NITD fast-acting leads belonging to spiroindolone and imidazothiadiazole class induce a common biochemical theme in drug-exposed malaria parasites which is similar to another fast-acting, clinically available drug, DHA. These biochemical features which are absent in a slower acting NITD lead (GNF17) point to hemoglobin digestion and inhibition of the pyrimidine pathway as potential action points for these drugs. These biochemical themes can be used to identify and inform on the mode of action of fast drug candidates of similar profiles in future drug discovery programs