93 research outputs found
Avoided ferromagnetic quantum critical point in CeRuPO
CeRuPO is a rare example of a ferromagnetic (FM) Kondo-lattice system.
External pressure suppresses the ordering temperature to zero at about
GPa. Our ac-susceptibility and electrical-resistivity
investigations evidence that the type of magnetic ordering changes from FM to
antiferromagnetic (AFM) at about GPa. Studies in applied
magnetic fields suggest that ferromagnetic and antiferromagnetic correlations
compete for the ground state at , but finally the AFM correlations win.
The change in the magnetic ground-state properties is closely related to the
pressure evolution of the crystalline-electric-field level (CEF) scheme and the
magnetic Ruderman-Kittel-Kasuya-Yosida (RKKY) exchange interaction. The
N\'{e}el temperature disappears abruptly in a first-order-like fashion at
, hinting at the absence of a quantum critical point. This is consistent
with the low-temperature transport properties exhibiting Landau-Fermi-liquid
(LFL) behavior in the whole investigated pressure range up to 7.5 GPa.Comment: 12 figure
Effect of pressure and Ir substitution in YbRh2Si2
In this article we present a study of the electrical resistivity of
Yb(Rh-xIrx)2Si2, x=0.06, under high pressure and in magnetic field. Ir
substitution is expanding the unit cell and leads to a suppression of the
antiferromagnetic transition temperature to zero, where eventually a quantum
critical point (QCP) exists. We applied hydrostatic pressure to reverse the
effect of substitution. Our results indicate that Yb(Rh0.94Ir0.06)2Si2 is
situated in the immediate proximity to a volume controlled QCP, but still on
the magnetically ordered side of the phase diagram. The temperature - pressure
phase diagram of Yb(Rh0.94Ir0.06)2Si2 resembles that of the pure compound.
Substitution acts mainly as chemical pressure. Disorder introduced by
substitution has only minor effects.Comment: 9 pages, 7 figures, accepted for publication in J. Phys.: Condens.
Matte
Temporal variability in the nutrient biogeochemistry of the surface North Atlantic: 15 years of ship of opportunity data
Ocean biological processes play an important role in the global carbon cycle via the production of organic matter and its subsequent export. Often, this flux is assumed to be in steady state; however, it is dependent on nutrients introduced to surface waters via multiple mechanisms, some of which are likely to exhibit both intraâannual and interannual variability leading to comparable variability in ocean carbon uptake. Here we test this variability using surface (5 m) inorganic nutrient concentrations from voluntary observing ships and satelliteâderived estimates of chlorophyll and net primary production. At lower latitudes, the seasonality is small, and the monthly averages of nitrate:phosphate are lower than the canonical 16:1 Redfield ratio, implying nitrogen limitation, a situation confirmed via a series of nutrient limitation experiments conducted between Bermuda and Puerto Rico. The nutrient seasonal cycle is more pronounced at higher latitudes, with clear interannual variability. Over a large area of the midlatitude North Atlantic, the winters of 2009/2010 and 2010/2011 had nitrate values more than 1ÎŒmolâLâ1 higher than the 2002â2017 average, suggesting that during this period, the system may have shifted to phosphorus limitation. This nitrate increase meant that, in the region between 31° and 39° N, new production calculated from nitrate uptake was 20.5g C mâ2 in 2010, more than four times higher than the median value of the whole observing period. Overall, we suggest that substantial variability in nutrient concentrations and biological carbon uptake occurs in the North Atlantic with interannual variability apparent over a number of different time scales
a pilot study, 2013
Introduction After recognition of European outbreaks of Clostridium difficile
infections (CDIs) associated with the emergence of PCR ribotype 027/NAP1 in
2005, CDI surveillance at country level was encouraged by the European Centre
for Disease Prevention and Control (ECDC) [1]. In 2008, an ECDC-supported
European CDI survey (ECDIS) identified large intercountry variations in
incidence rates and distribution of prevalent PCR ribotypes, with the
outbreak-related PCR ribotype 027 being detected in 5% (range: 0â26) of the
characterised isolates [2]. The surveillance period was limited to one month
and the representation of European hospitals was incomplete; however, this has
been the only European (comprising European Union (EU)/European Economic Area
(EEA) and EU candidate countries) CDI surveillance study. The authors
highlighted the need for national and European surveillance to control CDI.
Yet, European countries were found to have limited capacity for diagnostic
testing, particularly in terms of standard use of optimal methods and absence
of surveillance protocols and a fully validated, standardised and exchangeable
typing system for surveillance and/or outbreak investigation. As of 2011, 14
European countries had implemented national CDI surveillance, with various
methodologies [3]. National surveillance systems have since reported a
decrease in CDI incidence rate and/or prevalence of PCR ribotype 027 in some
European countries [4-8]. However, CDI generally remains poorly controlled in
Europe [9], and PCR ribotype 027 continues to spread in eastern Europe [10-12]
and globally [13]. In 2010, ECDC launched a new project, the European C.
difficile Infection Surveillance Network (ECDIS-Net), to enhance surveillance
of CDI and laboratory capacity to test for CDI in Europe. The goal of ECDIS-
Net was to establish a standardised CDI surveillance protocol suitable for
application all over Europe in order to: (i) estimate the incidence rate and
total infection rate of CDI (including recurrent CDI cases) in European acute
care hospitals; (ii) provide participating hospitals with a standardised tool
to measure and compare their own incidence rates with those observed in other
participating hospitals; (iii) assess adverse outcomes of CDI such as
complications and death; and (iv) describe the epidemiology of CDI concerning
antibiotic susceptibility, PCR ribotypes, presence of tcdA, tcdB and binary
toxins and detect new emerging types at local, national and European level.
The primary objectives of the present study were to: (i) test the pilot
protocol for the surveillance of CDI in European acute care hospitals
developed by ECDIS-Net (methodology, variables and indicators); (ii) assess
the feasibility and workload of collecting the required hospital data, case-
based epidemiological and microbiological data; and (iii) evaluate the quality
of data collected, whether in the presence or absence of existing national CDI
surveillance activities. A secondary aim was to assess the relationship
between patient and microbiological characteristics and in-hospital outcome of
CDI to confirm the added value of collecting detailed epidemiological and
microbiological data on CDI at European level
Risk Factors for Primary Clostridium difficile Infection; Results From the Observational Study of Risk Factors for Clostridium difficile Infection in Hospitalized Patients With Infective Diarrhea (ORCHID)
Background: There are inconsistent data on the risk factors for Clostridium difficile infection (CDI) in the literature.
Aims: To use two C. difficile infection (CDI) case-control study groups to compare risk factors in hospitalized patients with diarrhea across different countries.
Methods: A multi-center group of CDI cases/controls were identified by standardized testing from seven countries from the prior EUropean, multi-center, prospective bi-annual point prevalence study of CLostridium difficile Infection in hospitalized patients with Diarrhea (EUCLID). A second group of CDI cases/controls was identified from a single center in Germany [parallel study site (PSS)]. Data were extracted from the medical notes to assess CDI risk factors. Univariate analyses and multivariate logistic regression models were used to identify and compare risk factors between the two groups.
Results: There were 253 and 158 cases and 921 and 584 controls in the PSS and EUCLID groups, respectively. Significant variables from univariate analyses in both groups were age â„65, number of antibiotics (OR 1.2 for each additional antibiotic) and prior hospital admission (all p < 0.001). Congestive heart failure, diabetes, admission from assisted living or Emergency Department, proton pump inhibitors, and chronic renal disease were significant in PSS (all p < 0.05) but not EUCLID. Dementia and admitted with other bacterial diseases were significant in EUCLID (p < 0.05) but not PSS. Following multivariate analyses, age â„ 65, number of antibiotics and prior hospital admission were consistently identified as CDI risk factors in each individual group and combined datasets.
Conclusion: Our results show that the same CDI risk factors were identified across datasets. These were age â„ 65 years, antibiotic use and prior hospital admission. Importantly, the odds of developing CDI increases with each extra antibiotic prescribed
Standardised surveillance of Clostridium Difficile Infection in European acute care hospitals: A pilot study, 2013
Clostridium difficile infection (CDI) remains poorly controlled in many European countries, of which several have not yet implemented national CDI surveillance. In 2013, experts from the European CDI Surveillance Network project and from the European Centre for Disease Prevention and Control developed a protocol with three options of CDI surveillance for acute care hospitals: a âminimalâ option (aggregated hospital data), a âlightâ option (including patient data for CDI cases) and an âenhancedâ option (including microbiological data on the first 10 CDI episodes per hospital). A total of 37 hospitals in 14 European countries tested these options for a three-month period (between 13 May and 1 November 2013). All 37 hospitals successfully completed the minimal surveillance option (for 1,152 patients). Clinical data were submitted for 94% (1,078/1,152) of the patients in the light option; information on CDI origin and outcome was complete for 94% (1,016/1,078) and 98% (294/300) of the patients in the light and enhanced options, respectively. The workload of the options was 1.1, 2.0 and 3.0 person-days per 10,000 hospital discharges, respectively. Enhanced surveillance was tested and was successful in 32 of the hospitals, showing that C. difficile PCR ribotype 027 was predominant (30% (79/267)). This study showed that standardised multicountry surveillance, with the option of integrating clinical and molecular data, is a feasible strategy for monitoring CDI in Europe
Ăvaluation de la tension artĂ©rielle et de la pression du pouls dans le syndrome mĂ©tabolique
Objectif. Lâobjectif de notre Ă©tude est dâĂ©valuer la pression artĂ©rielle et la pression diffĂ©rentielle chez les patients atteints du syndrome mĂ©tabolique (SM), afin de dĂ©celer et de prĂ©venir les complications cardiovasculaires qui peuvent survenir chez ces patients.
MatĂ©riels et mĂ©thodes. Lâanalyse des casâtĂ©moin a Ă©tĂ© faite sur un total de 1528 patients, dans un cabinet de mĂ©decine familiale, les sujets Ă©tant rĂ©partis en deux groupes: le lot avec SM et le groupe tĂ©moin (sans SM). Le groupe avec SM se composait de 388 patients diagnostiquĂ©s selon les critĂšres harmonisĂ©s. Le groupe tĂ©moin sans SM Ă©tait composĂ© de 1140 patients nâayant pas prĂ©sentĂ© au moins trois critĂšres diagnostiques du syndrome mĂ©tabolique.
Résultats. La pression différentielle, les valeurs calculées pour les patients atteints de syndrome métabolique ont été généralement plus élevées que le taux moyen escompté à 40 mmHg, avec une valeur moyenne de 47,86 ± 12,02 mmHg. Le groupe de contrÎle a une valeur moyenne (40,28 ±12.20 mmHg) du pouls, une pression significativement plus faible (p<0.0001).
Conclusions. La tension diffĂ©rentielle est associĂ©e aux complications cardiovasculaires positives, en particulier chez les personnes ĂągĂ©es et surtout aux valeurs supĂ©rieure ou Ă©gale Ă 60 mmHg, mais cette association nâest pas indĂ©pendante de la tension artĂ©rielle
Activation of ERAD Pathway by Human Hepatitis B Virus Modulates Viral and Subviral Particle Production
Hepatitis B virus (HBV) belongs to the Hepadnaviridae family of enveloped DNA viruses. It was previously shown that HBV can induce endoplasmic reticulum (ER) stress and activate the IRE1-XBP1 pathway of the unfolded protein response (UPR), through the expression of the viral regulatory protein X (HBx). However, it remained obscure whether or not this activation had any functional consequences on the target genes of the UPR pathway. Of these targets, the ER degradation-enhancing, mannosidase-like proteins (EDEMs) are thought to play an important role in relieving the ER stress during UPR, by recognizing terminally misfolded glycoproteins and delivering them to the ER-associated degradation (ERAD). In this study, we investigated the role of EDEMs in the HBV life-cycle. We found that synthesis of EDEMs (EDEM1 and its homologues, EDEM2 and EDEM3) is significantly up-regulated in cells with persistent or transient HBV replication. Co-expression of the wild-type HBV envelope proteins with EDEM1 resulted in their massive degradation, a process reversed by EDEM1 silencing. Surprisingly, the autophagy/lysosomes, rather than the proteasome were involved in disposal of the HBV envelope proteins. Importantly, inhibition of the endogenous EDEM1 expression in HBV replicating cells significantly increased secretion of both, enveloped virus and subviral particles. This is the first report showing that HBV activates the ERAD pathway, which, in turn, reduces the amount of envelope proteins, possibly as a mechanism to control the level of virus particles in infected cells and facilitate the establishment of chronic infections
Quantum entanglement and disentanglement of multi-atom systems
We present a review of recent research on quantum entanglement, with special
emphasis on entanglement between single atoms, processing of an encoded
entanglement and its temporary evolution. Analysis based on the density matrix
formalism are described. We give a simple description of the entangling
procedure and explore the role of the environment in creation of entanglement
and in disentanglement of atomic systems. A particular process we will focus on
is spontaneous emission, usually recognized as an irreversible loss of
information and entanglement encoded in the internal states of the system. We
illustrate some certain circumstances where this irreversible process can in
fact induce entanglement between separated systems. We also show how
spontaneous emission reveals a competition between the Bell states of a two
qubit system that leads to the recently discovered "sudden" features in the
temporal evolution of entanglement. An another problem illustrated in details
is a deterministic preparation of atoms and atomic ensembles in long-lived
stationary squeezed states and entangled cluster states. We then determine how
to trigger the evolution of the stable entanglement and also address the issue
of a steered evolution of entanglement between desired pairs of qubits that can
be achieved simply by varying the parameters of a given system.Comment: Review articl
Separation of energy scales in undoped YbRhSi under hydrostatic pressure
The temperature ()-magnetic field () phase diagram of YbRhSi in
the vicinity of its quantum critical point is investigated by low-
magnetization measurements. Our analysis reveals that the energy scale
, previously related to the Kondo breakdown and terminating at 0.06
T for , remains unchanged under pressure, whereas the antiferromagnetic
critical field increases from 0.06 T () to 0.29 T ( GPa),
resulting in a crossing of and . Our results are very
similar to those on Yb(RhCo)Si, proving that the Co-induced
disorder can not be the reason for the detachment of both scales under chemical
pressure
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