Absence of magnetic long range order in Y2_{2}CrSbO7_{7}: bond-disorder induced magnetic frustration in a ferromagnetic pyrochlore

The consequences of nonmagnetic-ion dilution for the pyrochlore family Y$_{2}$($M_{1-x}N_{x}$)$_{2}$O$_{7}$ ($M$ = magnetic ion, $N$ = nonmagnetic ion) have been investigated. As a first step, we experimentally examine the magnetic properties of Y$_{2}$CrSbO$_{7}$ ($x$ = 0.5), in which the magnetic sites (Cr$^{3+}$) are percolative. Although the effective Cr-Cr spin exchange is ferromagnetic, as evidenced by a positive Curie-Weiss temperature, $\Theta_\mathrm{{CW}}$ = 20.1(6) K, our high-resolution neutron powder diffraction measurements detect no sign of magnetic long range order down to 2 K. In order to understand our observations, we performed numerical simulations to study the bond-disorder introduced by the ionic size mismatch between $M$ and $N$. Based on these simulations, bond-disorder ($x_{b}$ $\simeq$ 0.23) percolates well ahead of site-disorder ($x_{s}$ $\simeq$ 0.61). This model successfully reproduces the critical region (0.2 < $x$ < 0.25) for the N\'eel to spin glass phase transition in Zn(Cr$_{1-x}$Ga$_{x}$)$_{2}$O$_{4}$, where the Cr/Ga-sublattice forms the same corner-sharing tetrahedral network as the $M/N$-sublattice in Y$_{2}$($M_{1-x}N_{x}$)$_{2}$O$_{7}$, and the rapid drop in magnetically ordered moment in the N\'eel phase [Lee $et$ $al$, Phys. Rev. B 77, 014405 (2008)]. Our study stresses the nonnegligible role of bond-disorder on magnetic frustration, even in ferromagnets

Acute Leukemias Immunophenotypes at Agakhan University Hospital, Nairobi

Objective: The aim was to determine relative frequencies of acute  leukemia immunophenotypes using commonly expressed markers and to describe the clinicopathological characteristics.Design: This was a prospective cross-sectional study.Setting: The study was based at Aga khan clinical laboratory department.Subjects: One hundred and thirty two (132) consecutive blood and bone marrow specimens from patients suspected to have acute leukemia were analysed for cytomorphological characteristics and immunophenotyping. The clinical-pathological characteristics were also recorded. Immunological category was assigned using the EGIL criteria.Results: There were 88 AML and 42 ALL patients analysed for  immunophenotypes. Only tw cases of biphenotypic leukemia were found. The commonest overall AML morphological sub-type was AML-M2, 26 (29.5%). Majority of ALL cases were B-cell immunological sub-type (96.6%). Early pre-B phenotype constituted 62.07% and Common B-cell ALL 37.93%. There were only 4 cases of T-cell ALL. Majority of patientspresented with anaemia with a median hemoglobin of 7.5g/dl (range 2-15g/dl). The median platelet count was 55 (range 4-462 × 109/L).Conclusion: Immunophenotyping of acute leukemia is beneficial in accurate diagnosis of patients with these malignancies in this setup. T-cell ALL, AML-M6 and M7 are less frequent than what has been reported in most studies in Africa.Key words: acute leukemia, immunophenotype, WHO, EGIL, CD marker

Environmental and occupational factors associated with chronic myeloid leukemia: a case-control study

Background: The relationship between chronic myeloid leukemia (CML) and a broad range of exposures to occupational and environmental factors known to cause leukemia in general is limited. CML is by and large incurable and treatment is just palliative and life prolonging, with high case fatality rate, even in the best centers. Furthermore treatment is very expensive. Identification of leukemogenic factors is therefore important if this can lead to simple public health interventions. Objective: The objective was to determine key environmental and occupational exposure factors that may be associated with CML. Methods: This was a case-control study involving CML cases enrolled in Glivec International Patient Assistance Program (GIPAP) clinics at the Nairobi Hospital and Aga Khan University Hospital and two control groups for each case, matched for age and sex: a family- and hospital-based control, was carried out. One hundred and eight cases with age and-gender-matched family- and hospital-based controls were recruited and a standard questionnaire was administered. Individual data on demographics, occupation, environment, and exposures to benzene and farm organochemical products were obtained. Clinical examination was carried out in control subjects. Statistical analysis was done using bivariate and multivariate analysis to look for associations between exposure factors and CML. Results: The median age at diagnosis of CML cases was 41.32 years with an age range of 8–81 years and a male to female ratio of 1.7:1. Most of our cases were concentrated in or around Nairobi. There was no significant correlation found for exposure to benzene or pesticides. Long duration of exposure to pesticides in the family control group was significantly associated (t-test, P = 0.017) with risk of CML. Conclusions: Associations between exposures to organic solvents like pesticides and CML were indicated but were not entirely consistent, although no associations with benzene products were found. Nevertheless, for almost all cases of Ph chromosome-positive CML, other explanations must be sought for

High magnetic field studies of the Vortex Lattice structure in YBa2Cu3O7

We report on small angle neutron scattering measurements of the vortex lattice in twin-free YBa2Cu3O7, extending the previously investigated maximum field of 11~T up to 16.7~T with the field applied parallel to the c axis. This is the first microscopic study of vortex matter in this region of the superconducting phase. We find the high field VL displays a rhombic structure, with a field-dependent coordination that passes through a square configuration, and which does not lock-in to a field-independent structure. The VL pinning reduces with increasing temperature, but is seen to affect the VL correlation length even above the irreversibility temperature of the lattice structure. At high field and temperature we observe a melting transition, which appears to be first order, with no detectable signal from a vortex liquid above the transition

‘Thrown in at the deep end’: a qualitative analysis into the transition from trainee to consultant during the COVID-19 pandemic and lessons for the future

Background Sustained crises such as the COVID-19 pandemic would be expected to impact the transition from trainee to consultant for anaesthetists or intensivists, but limited research exists on this important topic. This study aimed to examine the social context of this crucial career transition during the pandemic and post-pandemic periods. Methods We conducted semi-structured interviews with anaesthetists and intensivists who became consultants after the first UK lockdown. Thematic analysis was used and data saturation was reached at 33 interviews. Results The pandemic substantially impacted the transition to consultant role in various ways, including professional identity, clinical and non-clinical responsibilities, and wellbeing. Participants experienced identity confusion, self-doubt, and moral injury, resulting in intense emotional distress, feelings of guilt and helplessness, which persisted beyond the pandemic. They also felt unprepared for their consultant roles because of disruptions in training. The pandemic exaggerated the vulnerability of those transitioning to consultants, because of increased clinical uncertainties, and pressures of the growing backlog. Additionally, the pandemic impacted on the wellbeing of those transitioning to consultants, intensifying feelings of anxiety and stress. We also identified unique opportunities presented by the pandemic, which accelerated learning and encouraged post-traumatic growth. Our study identified practical solutions that may improve transition experience at individual, organisational, and national levels. Conclusions Persistent crises significantly impact the transition from trainee to consultant. Our findings generated insights into the challenges of this critical career transition and staff wellbeing, and serve to inform approaches of ongoing support for those transitioning to consultants

Unconventional gap structures and the intermediate mixed state: a vortex lattice study of the noncentrosymmetric superconductor BiPd

We report on neutron scattering measurements on the vortex lattice of the noncentrosymmetric superconductor BiPd. We observe the existence of the intermediate mixed state, a region where Meissner and vortex lattice phases coexist, which is a feature of low $\kappa$ Type-II superconductors. Following this, we obtain an estimate of the value of $\kappa$ using the extended London model, which confirms the expectation that $\kappa$ should be small. Finally, we find that the temperature dependence of the vortex lattice form factor fits well to a model designed to describe singlet-triplet mixing in non-centrosymmetric superconductors, which may shed light on the question of the gap structure in BiPd

Rectus sheath haematoma or leaking aortic aneurysm - a diagnostic challenge: a case report

© 2009 Shaw et al; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution Licens

Observations of the effect of strong Pauli paramagnetism on the vortex lattice in superconducting CeCu2Si2

We present the results of a study of the vortex lattice in the heavy fermion superconductor CeCu2Si2, using small angle neutron scattering SANS . In this material at temperatures well below Tc amp; 8764;0.6 K, the value of the upper critical field Bc2 amp; 8764;2.2 T is strongly limited by the Pauli paramagnetism of the heavy fermions. In this temperature region, our SANS data show an increase in the magnetization of the flux line cores with field, followed by a rapid fall near Bc2. This behavior is the effect of Pauli paramagnetism and we present a theory based model, which can be used to describe this effect in a range of materials. The pairing in CeCu2Si2 appears to arise from the effect of magnetic fluctuations, but the evidence for a d wave order parameter is rather weak. We find that the vortex lattice structure in CeCu2Si2 is close to regular hexagonal. There are no phase transitions to square or rhombic structures; such transitions are expected for d wave superconductors and observed in CeCoIn5; however, the temperature dependence of the SANS intensity indicates that both large and small gap values are present, most likely due to multiband s wave superconductivity, rather than a nodal gap structur

Background Determination for the LUX-ZEPLIN (LZ) Dark Matter Experiment

The LUX-ZEPLIN experiment recently reported limits on WIMP-nucleus interactions from its initial science run, down to $9.2\times10^{-48}$ cm$^2$ for the spin-independent interaction of a 36 GeV/c$^2$ WIMP at 90% confidence level. In this paper, we present a comprehensive analysis of the backgrounds important for this result and for other upcoming physics analyses, including neutrinoless double-beta decay searches and effective field theory interpretations of LUX-ZEPLIN data. We confirm that the in-situ determinations of bulk and fixed radioactive backgrounds are consistent with expectations from the ex-situ assays. The observed background rate after WIMP search criteria were applied was $(6.3\pm0.5)\times10^{-5}$ events/keV$_{ee}$/kg/day in the low-energy region, approximately 60 times lower than the equivalent rate reported by the LUX experiment.Comment: 25 pages, 15 figure

A search for new physics in low-energy electron recoils from the first LZ exposure

The LUX-ZEPLIN (LZ) experiment is a dark matter detector centered on a dual-phase xenon time projection chamber. We report searches for new physics appearing through few-keV-scale electron recoils, using the experiment's first exposure of 60 live days and a fiducial mass of 5.5t. The data are found to be consistent with a background-only hypothesis, and limits are set on models for new physics including solar axion electron coupling, solar neutrino magnetic moment and millicharge, and electron couplings to galactic axion-like particles and hidden photons. Similar limits are set on weakly interacting massive particle (WIMP) dark matter producing signals through ionized atomic states from the Migdal effect.Comment: 13 pages, 10 figures. See https://tinyurl.com/LZDataReleaseRun1ER for a data release related to this pape