Competing itinerant and local spin interactions in kagome metal FeGe.

The combination of a geometrically frustrated lattice, and similar energy scales between degrees of freedom endows two-dimensional Kagome metals with a rich array of quantum phases and renders them ideal for studying strong electron correlations and band topology. The Kagome metal, FeGe is a noted example of this, exhibiting A-type collinear antiferromagnetic (AFM) order at TN ≈ 400 K, then establishes a charge density wave (CDW) phase coupled with AFM ordered moment below TCDW ≈ 110 K, and finally forms a c-axis double cone AFM structure around TCanting ≈ 60 K. Here we use neutron scattering to demonstrate the presence of gapless incommensurate spin excitations associated with the double cone AFM structure of FeGe at temperatures well above TCanting and TCDW that merge into gapped commensurate spin waves from the A-type AFM order. Commensurate spin waves follow the Bose factor and fit the Heisenberg Hamiltonian, while the incommensurate spin excitations, emerging below TN where AFM order is commensurate, start to deviate from the Bose factor around TCDW, and peaks at TCanting. This is consistent with a critical scattering of a second order magnetic phase transition with decreasing temperature. By comparing these results with density functional theory calculations, we conclude that the incommensurate magnetic structure arises from the nested Fermi surfaces of itinerant electrons and the formation of a spin density wave order.

An inelastic neutron scattering investigation of holmium orthoferrite.

The inelastic neutron scattering spectra recorded in this study and elsewhere provide a useful set of crystal-field (CF) energy levels for the groundJ= 6 term of Ho3+in HoFeO3. The resolution of the low-energy, temperature-dependent pseudo-quadrupole ground state splitting and magnon peaks is consistent with the self-ordering of the Ho3+sublattice atTHo∼ 8-10 K and supports earlier electron spin resonance investigations of the Ho3+magnon behaviour. Systematic analysis of the grouped singlet CF levels of Ho3: HoFeO3, in conjunction with the CF Kramers doublet levels of the neighbouring Er3+: ErFeO3, has yielded possible sets of CF parameters for the two systems.

Wave Vector Difference of Magnetic Bragg Reflections and Low Energy Magnetic Excitations in Charge-stripe Ordered La2NiO4.11.

We report on the magnetism of charge-stripe ordered La2NiO4.11±0.01 by neutron scattering and µSR. On going towards zero energy transfer there is an observed wave vector offset in the centring of the magnetic excitations and magnetic Bragg reflections, meaning the excitations cannot be described as Goldstone modes of the magnetic order. Weak transverse field µSR measurements determine the magnetically order volume fraction is 87% from the two stripe twins, and the temperature evolution of the magnetic excitations is consistent with the low energy excitations coming from the magnetically ordered volume of the material. We will discuss how these results contrast with the proposed origin of a similar wave vector offset recently observed in a La-based cuprate, and possible origins of this effect in La2NiO4.11.

Measuring the excitations in a new S = 1/2 quantum spin chain material with competing interactions.

Recently a new one-dimensional (1D) quantum spin chain system has been reported: catena-dichloro(2-Cl-3Mpy)copper(II), (where 2-Cl-3Mpy=2-chloro-3-methylpyridine). Preliminary calculations and bulk magnetic property measurements indicate that this system does not undergo magnetic ordering down to 1.8 K and is a prime candidate for investigating frustration in a J 1/J 2 system (where the nearest neighbour interactions, J 1, are ferromagnetic and the next nearest neighbour interactions, J 2, are antiferromagnetic). Calculations predicted three possible magnetic interaction strengths for J 1 below 6 meV depending on the orientation of the ligand. For one of the predicted J 1 values, the existence of a quantum critical point is implied. A deuterated sample of catena-dichloro(2-Cl-3Mpy)copper(II) was synthesised and the excitations measured using inelastic neutron scattering. Scattering indicated the most likely scenario involves spin-chains where each chain consists of only one of the three possible magnetic excitations in this material, rather than the completely random array of exchange interactions within each chain as predicted by Herringer et al (2014 Chem. Eur. J. 20 8355-62). This indicates the possibility of tuning the chemical structure to favour a system which may exhibit a quantum critical point.

Cluster-Based Haldane State in an Edge-Shared Tetrahedral Spin-Cluster Chain: Fedotovite K_{2}Cu_{3}O(SO_{4})_{3}.

Fedotovite K_{2}Cu_{3}O(SO_{4})_{3} is a candidate of new quantum spin systems, in which the edge-shared tetrahedral (EST) spin clusters consisting of Cu^{2+} are connected by weak intercluster couplings forming a one-dimensional array. Comprehensive experimental studies by magnetic susceptibility, magnetization, heat capacity, and inelastic neutron scattering measurements reveal the presence of an effective S=1 Haldane state below T≅4 K. Rigorous theoretical studies provide an insight into the magnetic state of K_{2}Cu_{3}O(SO_{4})_{3}: an EST cluster makes a triplet in the ground state and a one-dimensional chain of the EST induces a cluster-based Haldane state. We predict that the cluster-based Haldane state emerges whenever the number of tetrahedra in the EST is even.

Magnetic correlations in the intermetallic antiferromagnet Nd3Co4Sn13.

Specific heat, magnetic susceptibility, and neutron scattering have been used to investigate the nature of the spin system in the antiferromagnet Nd3Co4Sn13. At room temperature Nd3Co4Sn13 has a cubic, Pm-3n structure similar to Yb3Rh4Sn13. Antiferromagnetic interactions between, Nd3+ ions dominate the magnetic character of this sample and at 2.4 K the Nd spins enter a long range order state with a magnetic propagation vector q = (0 0 0) with an ordered moment of 1.78(2) µB at 1.5 K. The magnetic Bragg intensity grows very slowly below 1 K, reaching ~2.4 µB at 350 mK. The average magnetic Nd3+ configuration corresponds to the 3D irreducible representation Γ7. This magnetic structure can be viewed as three sublattices of antiferromagnetic spin chains coupled with each other in the 120°-configuration. A well-defined magnetic excitation was measured around the 1 1 1 zone centre and the resulting dispersion curve is appropriate for an antiferromagnet with a gap of 0.20(1) meV.

Unexpectedly Enhanced Solubility of Aromatic Amino Acids and Peptides in an Aqueous Solution of Divalent Transition-Metal Cations.

We experimentally observed considerable solubility of tryptophan (Trp) in a CuCl_{2} aqueous solution, which could reach 2-5 times the solubility of Trp in pure water. Theoretical studies show that the strong cation-π interaction between Cu^{2+} and the aromatic ring in Trp modifies the electronic distribution of the aromatic ring to enhance significantly the water affinity of Trp. Similar solubility enhancement has also been observed for other divalent transition-metal cations (e.g., Zn^{2+} and Ni^{2+}), another aromatic amino acid (phenylalanine), and three aromatic peptides (Trp-Phe, Phe-Phe, and Trp-Ala-Phe).

Enhanced ionic liquid mobility induced by confinement in 1D CNT membranes.

Water confined within carbon nanotubes (CNT) exhibits tremendous enhanced transport properties. Here, we extend this result to ionic liquids (IL) confined in vertically aligned CNT membranes. Under confinement, the IL self-diffusion coefficient is increased by a factor 3 compared to its bulk reference. This could lead to high power battery separators.

Hidden magnetic excitation in the pseudogap phase of a high-T(c) superconductor.

The elucidation of the pseudogap phenomenon of the high-transition-temperature (high-T(c)) copper oxides-a set of anomalous physical properties below the characteristic temperature T* and above T(c)-has been a major challenge in condensed matter physics for the past two decades. Following initial indications of broken time-reversal symmetry in photoemission experiments, recent polarized neutron diffraction work demonstrated the universal existence of an unusual magnetic order below T* (refs 3, 4). These findings have the profound implication that the pseudogap regime constitutes a genuine new phase of matter rather than a mere crossover phenomenon. They are furthermore consistent with a particular type of order involving circulating orbital currents, and with the notion that the phase diagram is controlled by a quantum critical point. Here we report inelastic neutron scattering results for HgBa(2)CuO(4+δ) that reveal a fundamental collective magnetic mode associated with the unusual order, and which further support this picture. The mode's intensity rises below the same temperature T* and its dispersion is weak, as expected for an Ising-like order parameter. Its energy of 52-56 meV renders it a new candidate for the hitherto unexplained ubiquitous electron-boson coupling features observed in spectroscopic studies.

Performance of FASTPlaqueTB and a modified protocol in a high HIV prevalence community in South Africa.

Modifications in the FASTPlaqueTB test protocol have resulted in an increase in the analytical limits of detection. This study investigated whether the performance of a modified prototype was able to increase the detection of smear-negative, culture-positive sputum samples as compared to the first generation FASTPlaqueTB test. Modifications to the FASTPlaqueTB did result in increased detection of smear-negative samples, but this was associated with a decrease in the specificity of the test. Before the FASTPlaqueTB can be considered as a viable replacement for smear microscopy and culture for the identification of tuberculosis, further work is required to resolve the performance issues identified in this study.

Increased attendances of people of eastern European origin at sexual health services in London.

OBJECTIVE: To describe the service use of migrants from eight central and eastern European (CEE) countries at two central London genitourinary medicine (GUM) clinics before and after accession to the European Union on 1 May 2004. METHODS: KC60 data collected between 1 June 2001 and 30 April 2007. Data refer to new attendances and exclude those attending for follow-up appointments. RESULTS: 102,604 people attended the clinics at least once over the study period. Between May 2006 and 30 April 2007 individuals born in the eight CEE countries accounted for 7.9% of attendances among women and 2.5% of attendances made by men; the proportion increasing significantly over the 6-year study period (p<0.001). Syphilis was more likely in CEE men (age-adjusted odds ratio (OR) 2.98, 95% CI 1.07 to 8.29) and family planning services were more likely to be required for CEE women (23.9% vs 12.4%, age-adjusted OR 2.33, 95% CI 2.02 to 2.68, p<0.001), than for those born elsewhere. A larger proportion of men from CEE countries were recorded as homosexual or bisexual than men from other countries (38.3% vs 31.9%, p = 0.003). CONCLUSIONS: CEE migrants already have a substantial impact on GUM services in London. If attendance rates continue at the current level CEE women will soon account for over 10% of new attendances. Although the majority of CEE migrants are men, proportionately fewer CEE men accessed GUM services than women. Sexual and reproductive health services need to adapt quickly to meet the needs of this growing population.

Evaluation of a rapid screening test for rifampicin resistance in re-treatment tuberculosis patients in the Eastern Cape.

BACKGROUND AND OBJECTIVES: Patients with multidrug-resistant (MDR) tuberculosis (TB) are at high risk of treatment failure. It is anticipated that early identification of MDR-TB and appropriate treatment will improve patient outcome and disease control. We evaluated the rapid detection of rifampicin resistance in previously treated TB patients, directly from acidfast bacilli (AFB)-positive sputum using a phage-based test, FASTPlaque-Response (Biotec Laboratories Ltd, Ipswich, UK). The ability of rifampicin resistance to predict MDR-TB was also determined. DESIGN: A prospective study was done comparing performance of the rapid phage test with conventional culture and drug susceptibility testing (DST) in AFB-positive TB patients. SETTING: Five primary health clinics and one TB referral centre in the Port Elizabeth Metropolitan area, Eastern Cape. OUTCOME MEASURES: Sensitivity, specificity and overall accuracy of the phage test were determined compared with gold standard culture and DST. Discrepant results were resolved by molecular detection of mutations conferring rifampicin resistance. The proportion of rifampicin-resistant strains that were MDR was also determined. RESULTS: Previously treated patients were at a high risk of MDRTB (35.7%). Sensitivity, specificity and overall accuracy of FASTPlaque-Response for rifampicin resistance determination were 95.4% (95% confidence interval (CI): 91.0 - 99.8%), 97.2% (95% CI: 94.5 - 99.9%) and 96.5% (95% CI: 94.1 - 98.9%) respectively compared with conventional DST (unresolved), calculated for specimens that had both FASTPlaque-Response and conventional DST results available. FASTPlaque-Response results were available in 2 days instead of 28 - 85 days with conventional DST. However, only 70.6% of FASTPlaque-Response results were interpretable compared with 86.3% of conventional DST results. The majority (95.5%) of rifampicinresistant strains were MDR-TB. CONCLUSIONS: Rapid detection of rifampicin resistance using FASTPlaque-Response could contribute to improved management of patients at risk of MDR-TB, such as previously treated patients. However, improvement in control of specimen-related contamination is needed to ensure that a higher proportion of FASTPlaque-Response results are interpretable. Where indicated, early modification of therapy could improve patient prognosis and reduce disease transmission.

Development of an antimicrobial formulation for control of specimen-related contamination in phage-based diagnostic testing for tuberculosis.

AIMS: To develop and evaluate an antimicrobial supplement for use with phage-based tests for rapid detection of drug resistance of tuberculosis (TB). METHODS AND RESULTS: An antimicrobial formulation containing nystatin, oxacillin and aztreonam (NOA) (final concentrations of 50,000 IU l(-1), 2 mg l(-1), and 30 mg l(-1) respectively) was developed. This formulation was tested for its influence on detection of a number of Mycobacterium tuberculosis (MTB) strains using the phage amplification (FASTPlaque) assay. Addition of the supplement did not lead to significant reduction in assay sensitivity. Antimicrobial efficacy was assessed with a range of Gram-positive and -negative organisms. The NOA supplement had a broad antimicrobial effect. The supplement was tested for its effect on growth of MTB culture, and on determination of rifampicin resistance using the phage-based methodology (FASTPlaque-Response). NOA did not significantly affect the growth of a range of rifampicin susceptible and resistant MTB strains, nor did it have an adverse effect on the number of interpretable results, nor the ability to discriminate between rifampicin susceptibility and resistance. CONCLUSION, SIGNIFICANCE AND IMPACT OF STUDY: Use of NOA antimicrobial supplement with rapid phage-based tests for TB will increase the proportion of interpretable results obtained, and enable their wider implementation in disease-endemic countries by improved control of specimen-related contamination.

Simple, phage-based (FASTPplaque) technology to determine rifampicin resistance of Mycobacterium tuberculosis directly from sputum.

SETTING: Cape Town, South Africa. OBJECTIVE: To evaluate the performance of a simple, manual, phage-based test for determining rifampicin (RMP) resistance of Mycobacterium tuberculosis directly from smear-positive sputum specimens. DESIGN: A comparative study of the performance of the FASTPlaque (phage amplification) technology to determine RMP resistance directly from smear-positive sputum compared with isolation and the conventional indirect Middlebrook 7H11 agar proportion method. RESULTS: The FASTPlaque direct RMP test achieved sensitivity, specificity and overall accuracy of 100% (11/11), 100% (134/134) and 100% (145/145), respectively, compared with the conventional indirect susceptibility test method (resolved data). The FASTPlaque direct RMP test reported results within 2 days from receipt of the specimen, while the conventional method took between 27 and 103 days (mean +/- SD 33.2 +/- 7.2 days). CONCLUSION: FASTPlaque technology applied directly to smear-positive sputum offers performance comparable to conventional methods, with results available in 2 days instead of weeks to months. The test may form a useful part of DOTS-Plus programmes to combat multidrug-resistant tuberculosis, improving patient prognosis and reducing ongoing transmission of disease. It does not require specialised equipment, making it appropriate for high-burden countries.

Rapid indication of multidrug-resistant tuberculosis from liquid cultures using FASTPlaqueTB-RIF, a manual phage-based test.

SETTING: A Mycobacteriology Reference Laboratory in Johannesburg, South Africa. OBJECTIVE: To determine the ability of FASTPlaqueTB-RIF, a rapid bacteriophage-based test, to correctly identify rifampicin susceptibility in clinical strains of Mycobacterium tuberculosis after growth in the Bactec 460 semi-automated liquid culture system. DESIGN: A comparative study of FASTPlaqueTB-RIF and conventional drug susceptibility methods, with selection bias to include sufficient rifampicin-resistant strains. RESULTS: Rifampicin susceptibility results were available for 133 strains of M. tuberculosis. Using the Bactec 460 method, 42 of these strains were rifampicin-resistant and 91 strains were rifampicin-susceptible. A further one strain was found to have a mutation in the rpoB gene which was strongly indicative of rifampicin resistance. Sensitivity, specificity and overall accuracy for the FASTPlaqueTB-RIF were respectively 100%, 98.8% and 99.2% for detection of rifampicin resistance; 95.3% (41/43) of the rifampicin-resistant strains were also resistant to isoniazid (multidrug-resistant). CONCLUSION: FASTPlaqueTB-RIF offers performance comparable to the Bactec 460 method, with results available within 2 days and without the need for specialised equipment. This makes FASTPlaqueTB-RIF a rapid test for rifampicin resistance suitable for widespread application. A combination of the FAST-PlaqueTB-RIF test with semi-automated liquid culture reduces the time required to report susceptibility results, enabling rapid and appropriate management of patients with MDR-TB. Rifampicin resistance was a good predictor of multidrug resistance in this population.

Performance of a rapid phage-based test, FASTPlaqueTB, to diagnose pulmonary tuberculosis from sputum specimens in South Africa.

SETTING: Twelve primary health care clinics in the South Peninsula Administration, Cape Town, Western Cape Province, South Africa. OBJECTIVE: To evaluate the performance of FAST-PlaqueTB, a new phage-based test, for the rapid diagnosis of TB in individuals with no previous history of TB treatment presenting at primary health care clinics in Cape Town, South Africa. DESIGN: A comparative study of FASTPlaqueTB, auramine smear microscopy and Lowenstein-Jensen culture of 1692 decontaminated sputum specimens from 853 patients suspected of having TB. Resolution of discrepant results was undertaken by review of clinical information, chest X-ray and follow-up of treatment outcomes. RESULTS: FASTPlaqueTB detected TB in 75.2% of culture-confirmed cases and 70.3% of all cases with a clinical diagnosis of TB, with a specificity of 98.7% and 99.0%, respectively. The performance parameters of FASTPlaqueTB were significantly superior to those of concentrated auramine smear microscopy (63.4% and 61.3% sensitivity, and 97.4% and 97.3% specificity in culture-confirmed and all cases, respectively). Of those patients with two negative sputum smears, FAST-PlaqueTB detected TB in 54.1% of TB cases confirmed by culture and 48.8% of all cases with a clinical diagnosis of TB. A combination of smear microscopy and FASTPlaqueTB enabled 81.2% of culture-confirmed cases and 78.4% of total TB cases to be detected within 2 days of presentation. CONCLUSION: FASTPlaqueTBTM is a rapid, manual test for the diagnosis of TB. The test has significantly higher sensitivity overall compared with auramine sputum smear microscopy in individuals with no previous history of TB treatment, although smear microscopy did detect the most infectious of the TB cases. The FAST-PlaqueTB test is easy to perform, requires no dedicated equipment, and results are read by eye within 48 hours. This test can be useful for the diagnosis of TB in developing countries with a high burden of TB where other rapid diagnostic tests may not be appropriate. The test shows promising performance, particularly in the diagnosis of smear-negative disease, and could be used in conjunction with smear microscopy to aid in the diagnosis of additional cases of TB.

Evaluation of FASTPlaqueTB-RIF, a rapid, manual test for the determination of rifampicin resistance from Mycobacterium tuberculosis cultures.

SETTING: Two Mycobacteriology Reference Laboratories in Johannesburg (Laboratory 1) and Cape Town (Laboratory 2), South Africa. OBJECTIVE: To determine the ability of the FASTPlaqueTB-RIF test to correctly identify rifampicin susceptibility on strains of Mycobacterium tuberculosis cultured on solid media. DESIGN: A comparative study of FASTPlaqueTB-RIF and conventional drug susceptibility methods, with selection bias to include sufficient rifampicin resistant strains. RESULTS: Rifampicin susceptibility results were available for 191 strains of M. tuberculosis. Eighty-one strains were found to be rifampicin resistant and 110 strains were rifampicin susceptible by conventional methods. The sensitivity, specificity and overall accuracy for the FASTPlaqueTB-RIF were 100%, 97% and 98% at Laboratory 1, and 100%, 94% and 97% at Laboratory 2. CONCLUSION: FASTPlaqueTB-RIF offers a performance comparable to the gold standard proportion methods of rifampicin susceptibility testing, as well as the advantage of the speed of results that the newer methods deliver, without the need for specialised equipment. This makes FASTPlaqueTB-RIF a rapid test for rifampicin resistance suitable for widespread application.

The biology and radiobiology of in utero development in relation to radiological protection.

Aspects of intrauterine development relevant to radiological protection but not considered in the recently revised Recommendations of ICRP (1991a) include (i) recently acquired evidence on the totipotency of cells of the morula with implications for dosimetry and risk in the first week of human development in utero; (ii) much older evidence on the earliest stages of myelo- and lymphopoiesis in the human subject that bears on radiosensitivity to leukaemia induction in utero; (iii) much older evidence on species differences that may affect the application to the human of experimental work on radionuclide transport from mother to embryo and fetus; (iv) recent proposals of alternative mechanisms for localization of functions in the developing mammalian forebrain with implications for risk of mental impairment caused by low level irradiation in utero, and (v) a recent demonstration that UNSCEAR (1977) was mistaken when concluding that a high radiosensitivity for teratogenesis is characteristic of the embryo and of preimplantation irradiation. The 1990 Recommendations of ICRP (1991a) to limit exposure of the fetus to radionuclides by reference to the occupation ALI for adults, i.e. women of reproductive age, seems to be a serious mistake.