Metamagnetism in the 2D Hubbard Model with easy axis

Although the Hubbard model is widely investigated, there are surprisingly few attempts to study the behavior of such a model in an external magnetic field. Using the Projector Quantum Monte Carlo technique, we show that the Hubbard model with an easy axis exhibits metamagnetic behavior if an external field is turned on. For the case of intermediate correlations strength $U$, we observe a smooth transition from an antiferromagnetic regime to a paramagnetic phase. While the staggered magnetization will decrease linearly up to a critical field $B_c$, uniform magnetization develops only for fields higher than $B_c$.Comment: RevTeX 5 pages + 2 postscript figures (included), accepted for PRB Rapid Communication

Large Orbital Magnetic Moment and Coulomb Correlation effects in FeBr2

We have performed an all-electron fully relativistic density functional calculation to study the magnetic properties of FeBr2. We show for the first time that the correlation effect enhances the contribution from orbital degrees of freedom of $d$ electrons to the total magnetic moment on Fe$^{2+}$ as opposed to common notion of nearly total quenching of the orbital moment on Fe$^{2+}$ site. The insulating nature of the system is correctly predicted when the Hubbard parameter U is included. Energy bands around the gap are very narrow in width and originate from the localized Fe-3$d$ orbitals, which indicates that FeBr2 is a typical example of the Mott insulator.Comment: 4 pages, 3 figures, revtex4, PRB accepte

Competing Ground States in Triple-layered Sr4Ru3O10: Verging on Itinerant Ferromagnetism with Critical Fluctuations

Sr4Ru3O10 is characterized by a sharp metamagnetic transition and ferromagnetic behavior occurring within the basal plane and along the c-axis, respectively. Resistivity at magnetic field, B, exhibits low-frequency quantum oscillations when B||c-axis and large magnetoresistivity accompanied by critical fluctuations driven by the metamagnetism when B^c-axis. The complex behavior evidenced in resistivity, magnetization and specific heat presented is not characteristic of any obvious ground states, and points to an exotic state that shows a delicate balance between fluctuations and order.Comment: 18 pages, 4 figure

Monitoring Procalcitonin in Febrile Neutropenia: What Is Its Utility for Initial Diagnosis of Infection and Reassessment in Persistent Fever?

Background: Management of febrile neutropenic episodes (FE) is challenged by lacking microbiological and clinical documentation of infection. We aimed at evaluating the utility of monitoring blood procalcitonin (PCT) in FE for initial diagnosis of infection and reassessment in persistent fever.Methods: PCT kinetics was prospectively monitored in 194 consecutive FE (1771 blood samples): 65 microbiologically documented infections (MDI, 33.5%; 49 due to non-coagulase-negative staphylococci, non-CNS), 68 clinically documented infections (CDI, 35%; 39 deep-seated), and 61 fever of unexplained origin (FUO, 31.5%).Results: At fever onset median PCT was 190 pg/mL (range 30-26'800), without significant difference among MDI, CDI and FUO. PCT peak occurred on day 2 after onset of fever: non-CNS-MDI/deep-seated-CDI (656, 80-86350) vs. FUO (205, 33-771; p<0.001). PCT >500 pg/mL distinguished non-CNS-MDI/deep-seated-CDI from FUO with 56% sensitivity and 90% specificity. PCT was >500 pg/ml in only 10% of FUO (688, 570-771). A PCT peak >500 pg/mL (1196, 524-11950) occurred beyond 3 days of persistent fever in 17/21 (81%) invasive fungal diseases (IFD). This late PCT peak identified IFD with 81% sensitivity and 57% specificity and preceded diagnosis according to EORTC-MSG criteria in 41% of cases. In IFD responding to therapy, median days to PCT <500 pg/mL and defervescence were 5 (1-23) vs. 10 (3-22; p = 0.026), respectively.Conclusion: While procalcitonin is not useful for diagnosis of infection at onset of neutropenic fever, it may help to distinguish a minority of potentially severe infections among FUOs on day 2 after onset of fever. In persistent fever monitoring procalcitonin contributes to early diagnosis and follow-up of invasive mycose

Procalcitonin for diagnosis of infection and guide to antibiotic decisions: past, present and future

There are a number of limitations to using conventional diagnostic markers for patients with clinical suspicion of infection. As a consequence, unnecessary and prolonged exposure to antimicrobial agents adversely affect patient outcomes, while inappropriate antibiotic therapy increases antibiotic resistance. A growing body of evidence supports the use of procalcitonin (PCT) to improve diagnosis of bacterial infections and to guide antibiotic therapy. For patients with upper and lower respiratory tract infection, post-operative infections and for severe sepsis patients in the intensive care unit, randomized-controlled trials have shown a benefit of using PCT algorithms to guide decisions about initiation and/or discontinuation of antibiotic therapy. For some other types of infections, observational studies have shown promising first results, but further intervention studies are needed before use of PCT in clinical routine can be recommended. The aim of this review is to summarize the current evidence for PCT in different infections and clinical settings, and discuss the reliability of this marker when used with validated diagnostic algorithms

Research approvals iceberg: how a 'low-key' study in England needed 89 professionals to approve it and how we can do better.

BACKGROUND: The red tape and delays around research ethics and governance approvals frequently frustrate researchers yet, as the lesser of two evils, are largely accepted as unavoidable. Here we quantify aspects of the research ethics and governance approvals for one interview- and questionnaire-based study conducted in England which used the National Health Service (NHS) procedures and the electronic Integrated Research Application System (IRAS). We demonstrate the enormous impact of existing approvals processes on costs of studies, including opportunity costs to focus on the substantive research, and suggest directions for radical system change. MAIN TEXT: We have recorded 491 exchanges with 89 individuals involved in research ethics and governance approvals, generating 193 pages of email text excluding attachments. These are conservative estimates (e.g. only records of the research associate were used). The exchanges were conducted outside IRAS, expected to be the platform where all necessary documents are provided and questions addressed. Importantly, the figures exclude the actual work of preparing the ethics documentation (such as the ethics application, information sheets and consent forms). We propose six areas of work to enable system change: 1. Support the development of a broad range of customised research ethics and governance templates to complement generic, typically clinical trials orientated, ones; 2. Develop more sophisticated and flexible frameworks for study classification; 3. Link with associated processes for assessment, feedback, monitoring and reporting, such as ones involving funders and patient and public involvement groups; 4. Invest in a new generation IT infrastructure; 5. Enhance system capacity through increasing online reviewer participation and training; and 6. Encourage researchers to quantify the approvals processes for their studies. CONCLUSION: Ethics and governance approvals are burdensome for historical reasons and not because of the nature of the task. There are many opportunities to improve their efficiency and analytic depth in an age of innovation, increased connectivity and distributed working. If we continue to work under current systems, we are perpetuating, paradoxically, an unethical system of research approvals by virtue of its wastefulness and impoverished ethical debate

Genetic diversity and risk factors for the transmission of antimicrobial resistance across human, animals and environmental compartments in East Africa: a review.

BACKGROUND The emergence and spread of antimicrobial resistance (AMR) present a challenge to disease control in East Africa. Resistance to beta-lactams, which are by far the most used antibiotics worldwide and include the penicillins, cephalosporins, monobactams and carbapenems, is reducing options for effective control of both Gram-positive and Gram-negative bacteria. The World Health Organization, Food and Agricultural Organization and the World Organization for Animal Health have all advocated surveillance of AMR using an integrated One Health approach. Regional consortia also have strengthened collaboration to address the AMR problem through surveillance, training and research in a holistic and multisectoral approach. This review paper contains collective information on risk factors for transmission, clinical relevance and diversity of resistance genes relating to extended-spectrum beta-lactamase-producing (ESBL) and carbapenemase-producing Enterobacteriaceae, and Methicillin-resistant Staphylococcus aureus (MRSA) across the human, animal and environmental compartments in East Africa. MAIN BODY The review of the AMR literature (years 2001 to 2019) was performed using search engines such as PubMed, Scopus, Science Direct, Google and Web of Science. The search terms included 'antimicrobial resistance and human-animal-environment', 'antimicrobial resistance, risk factors, genetic diversity, and human-animal-environment' combined with respective countries of East Africa. In general, the risk factors identified were associated with the transmission of AMR. The marked genetic diversity due to multiple sequence types among drug-resistant bacteria and their replicon plasmid types sourced from the animal, human and environment were reported. The main ESBL, MRSA and carbapenem related genes/plasmids were the CTX-Ms (45.7%), SCCmec type III (27.3%) and IMP types (23.8%), respectively. CONCLUSION The high diversity of the AMR genes suggests there may be multiple sources of resistance bacteria, or the possible exchange of strains or a flow of genes amongst different strains due to transfer by mobile genetic elements. Therefore, there should be harmonized One Health guidelines for the use of antibiotics, as well as regulations governing their importation and sale. Moreover, the trend of ESBLs, MRSA and carbapenem resistant (CAR) carriage rates is dynamic and are on rise over time period, posing a public health concern in East Africa. Collaborative surveillance of AMR in partnership with regional and external institutions using an integrated One Health approach is required for expert knowledge and technology transfer to facilitate information sharing for informed decision-making

Layer-dependent ferromagnetism in a van der Waals crystal down to the monolayer limit

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