Thermal Evolution of Dirac Magnons in the Honeycomb Ferromagnet CrBr_{3}.

CrBr_{3} is an excellent realization of the two-dimensional honeycomb ferromagnet, which offers a bosonic equivalent of graphene with Dirac magnons and topological character. We perform inelastic neutron scattering measurements using state-of-the-art instrumentation to update 50-year-old data, thereby enabling a definitive comparison both with recent experimental claims of a significant gap at the Dirac point and with theoretical predictions for thermal magnon renormalization. We demonstrate that CrBr_{3} has next-neighbor J_{2} and J_{3} interactions approximately 5% of J_{1}, an ideal Dirac magnon dispersion at the K point, and the associated signature of isospin winding. The magnon lifetime and the thermal band renormalization show the universal T^{2} evolution expected from an interacting spin-wave treatment, but the measured dispersion lacks the predicted van Hove features, pointing to the need for more sophisticated theoretical analysis.

Pauling Entropy, Metastability, and Equilibrium in Dy_{2}Ti_{2}O_{7} Spin Ice.

Determining the fate of the Pauling entropy in the classical spin ice material Dy_{2}Ti_{2}O_{7} with respect to the third law of thermodynamics has become an important test case for understanding the existence and stability of ice-rule states in general. The standard model of spin ice-the dipolar spin ice model-predicts an ordering transition at T≈0.15 K, but recent experiments by Pomaranski et al. suggest an entropy recovery over long timescales at temperatures as high as 0.5 K, much too high to be compatible with the theory. Using neutron scattering and specific heat measurements at low temperatures and with long timescales (0.35 K/10^{6} s and 0.5 K/10^{5} s, respectively) on several isotopically enriched samples, we find no evidence of a reduction of ice-rule correlations or spin entropy. High-resolution simulations of the neutron structure factor show that the spin correlations remain well described by the dipolar spin ice model at all temperatures. Furthermore, by careful consideration of hyperfine contributions, we conclude that the original entropy measurements of Ramirez et al. are, after all, essentially correct: The short-time relaxation method used in that study gives a reasonably accurate estimate of the equilibrium spin ice entropy due to a cancellation of contributions.

Dipolar Spin Ice States with a Fast Monopole Hopping Rate in CdEr_{2}X_{4} (X=Se, S).

Excitations in a spin ice behave as magnetic monopoles, and their population and mobility control the dynamics of a spin ice at low temperature. CdEr_{2}Se_{4} is reported to have the Pauling entropy characteristic of a spin ice, but its dynamics are three orders of magnitude faster than the canonical spin ice Dy_{2}Ti_{2}O_{7}. In this Letter we use diffuse neutron scattering to show that both CdEr_{2}Se_{4} and CdEr_{2}S_{4} support a dipolar spin ice state-the host phase for a Coulomb gas of emergent magnetic monopoles. These Coulomb gases have similar parameters to those in Dy_{2}Ti_{2}O_{7}, i.e., dilute and uncorrelated, and so cannot provide three orders faster dynamics through a larger monopole population alone. We investigate the monopole dynamics using ac susceptometry and neutron spin echo spectroscopy, and verify the crystal electric field Hamiltonian of the Er^{3+} ions using inelastic neutron scattering. A quantitative calculation of the monopole hopping rate using our Coulomb gas and crystal electric field parameters shows that the fast dynamics in CdEr_{2}X_{4} (X=Se, S) are primarily due to much faster monopole hopping. Our work suggests that CdEr_{2}X_{4} offer the possibility to study alternative spin ice ground states and dynamics, with equilibration possible at much lower temperatures than the rare earth pyrochlore examples.

Magnetic Excitations and Electronic Interactions in Sr_{2}CuTeO_{6}: A Spin-1/2 Square Lattice Heisenberg Antiferromagnet.

Sr_{2}CuTeO_{6} presents an opportunity for exploring low-dimensional magnetism on a square lattice of S=1/2 Cu^{2+} ions. We employ ab initio multireference configuration interaction calculations to unravel the Cu^{2+} electronic structure and to evaluate exchange interactions in Sr_{2}CuTeO_{6}. The latter results are validated by inelastic neutron scattering using linear spin-wave theory and series-expansion corrections for quantum effects to extract true coupling parameters. Using this methodology, which is quite general, we demonstrate that Sr_{2}CuTeO_{6} is an almost ideal realization of a nearest-neighbor Heisenberg antiferromagnet but with relatively weak coupling of 7.18(5) meV.

Measurement of the charge and current of magnetic monopoles in spin ice.

The transport of electrically charged quasiparticles (based on electrons or ions) plays a pivotal role in modern technology as well as in determining the essential functions of biological organisms. In contrast, the transport of magnetic charges has barely been explored experimentally, mainly because magnetic charges, in contrast to electric ones, are generally considered at best to be convenient macroscopic parameters, rather than well-defined quasiparticles. However, it was recently proposed that magnetic charges can exist in certain materials in the form of emergent excitations that manifest like point charges, or magnetic monopoles. Here we address the question of whether such magnetic charges and their associated currents-'magnetricity'-can be measured directly in experiment, without recourse to any material-specific theory. By mapping the problem onto Onsager's theory of electrolytes, we show that this is indeed possible, and devise an appropriate method for the measurement of magnetic charges and their dynamics. Using muon spin rotation as a suitable local probe, we apply the method to a real material, the 'spin ice' Dy(2)Ti(2)O(7) (refs 5-8). Our experimental measurements prove that magnetic charges exist in this material, interact via a Coulomb potential, and have measurable currents. We further characterize deviations from Ohm's law, and determine the elementary unit of magnetic charge to be 5 mu(B) A(-1), which is equal to that recently predicted using the microscopic theory of spin ice. Our measurement of magnetic charge and magnetic current establishes an instance of a perfect symmetry between electricity and magnetism.

Magnetoelastic excitations in the pyrochlore spin liquid Tb2Ti2O7.

At low temperatures, Tb2Ti2O7 enters a spin liquid state, despite expectations of magnetic order and/or a structural distortion. Using neutron scattering, we have discovered that in this spin liquid state an excited crystal field level is coupled to a transverse acoustic phonon, forming a hybrid excitation. Magnetic and phononlike branches with identical dispersion relations can be identified, and the hybridization vanishes in the paramagnetic state. We suggest that Tb2Ti2O7 is aptly named a "magnetoelastic spin liquid" and that the hybridization of the excitations suppresses both magnetic ordering and the structural distortion. The spin liquid phase of Tb2Ti2O7 can now be regarded as a Coulomb phase with propagating bosonic spin excitations.

Power-law spin correlations in the pyrochlore antiferromagnet Tb(2)Ti(2)O(7).

We investigate the low-temperature state of the rare-earth pyrochlore Tb(2)Ti(2)O(7) using polarized neutron scattering. Tb(2)Ti(2)O(7) is often described as an antiferromagnetic spin liquid with spin correlations extending over lengths comparable to individual tetrahedra of the pyrochlore lattice. We confirm this picture at 20 K but find that at 0.05 K the data contain evidence of pinch-point scattering, suggesting that the low temperature state of Tb(2)Ti(2)O(7) has power-law spin correlations.

Consequence of excess configurational entropy on fragility: the case of a polymer-oligomer blend.

By taking advantage of the molecular weight dependence of the glass transition of polymers and their ability to form perfectly miscible blends, we propose a way to modify the fragility of a system, from fragile to strong, keeping the same glass properties, i.e., vibrational density of states, mean-square displacement, and local structure. Both slow and fast dynamics are investigated by calorimetry and neutron scattering in an athermal polystyrene-oligomer blend, and compared to those of a pure 17-mer polystyrene considered to be a reference, of the same Tg. Whereas the blend and the pure 17-mer have the same heat capacity in the glass and in the liquid, their fragilities differ strongly. Thus, the difference in fragility is related to an extra configurational entropy created by the mixing process and acting at a scale much larger than the interchain distance, without affecting the fast dynamics and the structure of the glass.

Special temperatures in frustrated ferromagnets.

The description and detection of unconventional magnetic states, such as spin liquids, is a recurring topic in condensed matter physics. While much of the efforts have traditionally been directed at geometrically frustrated antiferromagnets, recent studies reveal that systems featuring competing antiferromagnetic and ferromagnetic interactions are also promising candidate materials. We find that this competition leads to the notion of special temperatures, analogous to those of gases, at which the competing interactions balance, and the system is quasi-ideal. Although induced by weak perturbing interactions, these special temperatures are surprisingly high and constitute an accessible experimental diagnostic of eventual order or spin-liquid properties. The well characterised Hamiltonian and extended low-temperature susceptibility measurement of the canonical frustrated ferromagnet Dy2Ti2O7 enables us to formulate both a phenomenological and microscopic theory of special temperatures for magnets. Other members of this class of magnets include kapellasite Cu3Zn(OH)6Cl2 and the spinel GeCo2O4.

Acute intravenous exposure to silver nanoparticles during pregnancy induces particle size and vehicle dependent changes in vascular tissue contractility in Sprague Dawley rats.

The use of silver nanoparticles (AgNP) raises safety concerns during susceptible life stages such as pregnancy. We hypothesized that acute intravenous exposure to AgNP during late stages of pregnancy will increase vascular tissue contractility, potentially contributing to alterations in fetal growth. Sprague Dawley rats were exposed to a single dose of PVP or Citrate stabilized 20 or 110nm AgNP (700µg/kg). Differential vascular responses and EC50 values were observed in myographic studies in uterine, mesenteric arteries and thoracic aortic segments, 24h post-exposure. Reciprocal responses were observed in aortic and uterine vessels following PVP stabilized AgNP with an increased force of contraction in uterine artery and increased relaxation responses in aorta. Citrate stabilized AgNP exposure increased contractile force in both uterine and aortic vessels. Intravenous AgNP exposure during pregnancy displayed particle size and vehicle dependent moderate changes in vascular tissue contractility, potentially influencing fetal blood supply.

Characterization of the biliary and urinary glutathione and N-acetylcysteine metabolites of the hepatic carcinogen 1'-hydroxysafrole and its 1'-oxo metabolite in rats and mice.

The hepatocarcinogen safrole is metabolized both to 1'-hydroxysafrole, a proximate hepatocarcinogen, and to 1'-oxosafrole, which is electrophilic but has little or no carcinogenic activity in rats and mice. As a part of a study on the metabolic interrelationships of these metabolites, their biliary and urinary conjugates were investigated. Administration of a single i.p. dose of [2',3'-3H]-1'-oxosafrole to male Sprague-Dawley rats or female CD-1 mice with cannulated bile ducts resulted in the excretion of 2 major biliary metabolites. These metabolites were isolated by high-performance liquid chromatography and characterized by 1H-nuclear magnetic resonance spectroscopy as 3'-(glutathion-S-yl)-1'-oxo-2',3'-dihydrosafrole and 3'-(N-acetylcystein-S-yl)-1'-oxo-2',3'-dihydrosafrole. The latter conjugate was also found in the urine. These conjugates were synthesized by non-enzymatic reaction of 1'-oxosafrole with glutathione and N-acetylcysteine at pH 8. After a single i.p. dose of [2',3'-3H]-1'-hydroxysafrole, the major biliary and urinary metabolite in rats was the glucuronide of this alcohol. Lower levels of the glutathione and N-acetylcysteine conjugates of 1'-oxosafrole appeared in the bile, and the latter conjugate was also found in the urine. Similar findings were made on the biliary metabolites of 1'-hydroxysafrole in mice. Although the sulfuric acid ester of 1'-hydroxysafrole is the major metabolite leading to the formation of DNA adducts in the liver, it was, at most, of minor importance in the formation of glutathione adducts. Only a very small percentage of a dose of 1'-hydroxysafrole was excreted in the bile of rats or mice as products that cochromatographed with 1'-(glutathion-S-yl)-safrole and 3'-(glutathion-S-yl)-isosafrole; no 3'-(N-acetylcystein-S-yl)-isosafrole was detected. These latter conjugates were synthesized by nonenzymatic reactions at pH 8.5 of the model electrophilic ester 1'-acetoxysafrole with glutathione or N-acetylcysteine.

Major role of hepatic sulfotransferase activity in the metabolic activation, DNA adduct formation, and carcinogenicity of 1'-hydroxy-2',3'-dehydroestragole in infant male C57BL/6J x C3H/HeJ F1 mice.

1'-Hydroxy-2',3'-dehydroestragole is a synthetic acetylenic analogue of 1'-hydroxyestragole, the proximate carcinogenic metabolite of the naturally occurring hepatocarcinogen estragole (1-allyl-4-methoxybenzene). This analogue is considerably more potent than 1'-hydroxyestragole as an hepatocarcinogen in mice. 1'-Acetoxy-2',3'-dehydroestragole reacted readily with deoxyguanosine or deoxyguanosine 5'-monophosphate at neutrality to form two adducts. Adduct I, isolated and characterized after dephosphorylation of the deoxyguanosine 5'-monophosphate product, was a 1:1 mixture of two diastereomers of N2-(2',3'-dehydroestragol-1'-yl)deoxyguanosine. Adduct II was shown to be N-7-(2',3'-dehydroestragol-1'-yl)guanine. The reaction of deoxyadenosine with 1'-acetoxy-2',3'-dehydroestragole at neutrality produced Adducts III and IV. Adduct IV was characterized as N6-(2',3'-dehydroestragol-1'-yl)deoxyadenosine. Administration of [1'-3H]-1'-hydroxy-2',3'-dehydroestragole to male preweanling C57BL/6J x C3H/HeJ F1 (hereafter called B6C3F1) mice resulted in extensive covalent binding to hepatic DNA, RNA, and protein. On hydrolysis of the DNA to nucleosides, a single major adduct accounted for greater than 85% of the DNA-bound 3H. This adduct comigrated with Adduct I in two high performance liquid chromatography systems, had a pH partition profile identical to that of Adduct I, and was present as a mixture of diastereomers in a ratio of 2:1. The identity of the DNA adduct formed in vivo with Adduct I from the reaction of 1'-acetoxydehydroestragole indicated that a reactive ester was a major metabolic precursor in vivo. There was no significant loss of Adduct I from the hepatic DNA by 21 days after a single injection of a carcinogenic dose of 1'-hydroxy-2',3'-dehydroestragole. Adducts II, III, and IV were not detected in significant amounts in the hepatic DNA isolated by a phenol extraction method or by a more rapid hydroxylapatite method. Cytosolic sulfotransferase activity was demonstrated for 1-hydroxy-2',3'-dehydroestragole in mouse liver, and inhibition of this activity by greater than 95% was found on addition of 10 microM pentachlorophenol. The administration of pentachlorophenol (0.04 mumol/g body weight) 45 min prior to a single dose of 1'-hydroxy-2',3'-dehydroestragole (0.04 mumol/g body weight) in 12-day-old male B6C3F1 mice greatly inhibited (87-97%) the covalent binding of 1'-hydroxy-2',3'-dehydroestragole to hepatic macromolecules and the formation of hepatomas at 10 months.(ABSTRACT TRUNCATED AT 400 WORDS)

Further characterization of the DNA adducts formed by electrophilic esters of the hepatocarcinogens 1'-hydroxysafrole and 1'-hydroxyestragole in vitro and in mouse liver in vivo, including new adducts at C-8 and N-7 of guanine residues.

The identities of the adducts formed on reaction of the model electrophilic and carcinogenic esters 1'-acetoxysafrole or 1'-acetoxyestragole with deoxyguanosine in vitro and those formed in vivo in the hepatic DNA of 12-day-old male C57BL/6 X C3H/He F1 (hereafter called B6C3F1) mice treated with 1'-hydroxysafrole or 1'-acetoxysafrole were investigated further with more discriminating high-performance liquid chromatography systems than previously used. The adducts formed from the reactions of 1'-acetoxysafrole or 1'-acetoxyestragole are strictly analogous and are distinguished by the prefixes S and E, respectively. Five adducts, including S(E)-II identified by Phillips et al. (Cancer Res., 41: 176-186, 2664-2671, 1981) as N2-(trans-isosafrol-3'-yl)deoxyguanosine and the analogous isoestragole derivative, have been characterized from the reactions with each ester. Adducts S-I and E-I, tentatively identified by Phillips et al. as N2-(safrol-1'-yl)- or N2-(estragol-1'-yl)deoxyguanosine, were each resolved into a pair of diastereomers. The proposed structures for each diastereomer were confirmed by nuclear magnetic resonance and circular dichroism spectroscopy. Two new adducts, i.e., S(E)-V and S(E)-VI, were isolated from each reaction mixture. On the basis of their pKas, their loss of 3H from [8-3H]deoxyguanosine, their retention of 3H from [1',2'-3H]deoxyguanosine, and their nuclear magnetic resonance spectra, Adducts S-V and E-V were characterized as 8-(trans-isosafrol-3'-yl)- and 8-(trans-isoestragol-3'-yl)deoxyguanosine, respectively. Adducts S-VI and E-VI were characterized in a similar manner as 7-(trans-isosafrol-3'-yl)- and 7-(trans-isoestragol-3'-yl)guanine, respectively. Adducts S-III and E-III, minor components described in the earlier studies, were not observed in the present work. High-performance liquid chromatography of hydrolysates of the hepatic DNA of male 12-day-old B6C3F1 mice killed 9 h after a single dose (0.1 mumol/g body weight) of [2',3'-3H]-1'-hydroxysafrole showed that Adducts S-Ia, S-Ib, S-II, S-IV (identified by Phillips et al. as N6-(trans-isosafrol-3'-yl)deoxyadenosine), S-V, and S-VI were present at average levels of 3.5, 7.0, 24.4, 2.9, 1.2, and 3.6 pmol/mg DNA, respectively. Similar levels of these adducts were found in the hepatic DNA after administration of the same dose of [2',3'-3H]-1'-acetoxysafrole under identical conditions.

Molecular dosimetry of ethylene oxide: formation and persistence of N-(2-hydroxyethyl)valine in hemoglobin following repeated exposures of rats and mice.

The formation of N-(2-hydroxyethyl)valine (HEVal) in hemoglobin was investigated in male F344 rats (10/group) and B6C3F1 mice (20/group) exposed to 0, 3, 10, 33, 100, or 300 (rats only) ppm ethylene oxide (ETO) by inhalation for 6 h/day for 4 weeks (5 days/week) or exposed to 100 (mice) or 300 ppm (rats) ETO for 1 or 3 days, or 1, 2, or 4 weeks (5 days/week). The persistence of HEVal was studied in animals killed up to 10 days after cessation of the 4-week time-course studies. HEVal was determined by a modified Edman degradation and quantitation of the resulting pentafluorophenylthiohydantoin derivative, using gas chromatography-mass spectrometry. The resulting experimental data were compared to simulations derived with a model for the formation and removal of hemoglobin adducts (T.R. Fennell, S.C.J. Sumner, and V.E. Walker, Cancer Epidemiol., Biomarkers & Prev., 1: 213-219, 1992). Repeated exposures of rats and mice for 4 weeks to 300 and 100 ppm ETO, respectively, led to an accumulation of HEVal that was 14 (rats) and 15 (mice) times greater than that found after 1 day of exposure [28 +/- 2 (SE) and 9.4 +/- 0.4 (SE) pmol HEVal/mg globin in rats and mice, respectively]. After cessation of exposures, HEVal was lost faster than predicted by the normal erythrocyte life span alone. An initial phase of rapid decline in HEVal concentrations was consistent with the removal of older, more heavily alkylated populations of RBCs, accompanied by a burst of erythropoiesis. The dose-response curves for HEVal were linear between 3 and 33 ppm ETO, with 3.5 +/- 0.2 and 3.4 +/- 0.3 pmol adduct/mg globin formed in rats and mice, respectively, after 4 weeks of exposure to 3 ppm ETO. Above 33 ppm ETO, the slope of the dose-response curves increased. Comparison of the dose response for HEVal in rats exposed to ETO for 4 weeks to the dose-response for N tau-(2-hydroxyethyl)histidine in rats exposed to the same concentrations of ETO for 2 years (S. Osterman-Golkar et al., Teratog. Carcinog. Mutagen., 3: 395-405, 1983) suggested that exposures to ETO can reduce the life span of erythrocytes in a concentration- and time-dependent manner. Correlation of the experimental data and simulations for the formation and removal of HEVal demonstrated that perturbations in erythropoiesis and RBC life span complicate the estimation of exposures to ETO when estimates are based upon hemoglobin adduct measurements in heavily exposed individuals.(ABSTRACT TRUNCATED AT 400 WORDS)

Molecular dosimetry of ethylene oxide: formation and persistence of 7-(2-hydroxyethyl)guanine in DNA following repeated exposures of rats and mice.

The formation of 7-(2-hydroxyethyl)guanine (7-HEG) in DNA of target and nontarget tissues was investigated in male B6C3F1 mice (20/group) and F344 rats (10/group) exposed to 0, 3, 10, 33, 100, or 300 (rats only) ppm ethylene oxide (ETO) by inhalation for 6 h/day for 4 weeks (5 days/week) and mice exposed to 100 ppm ETO for 1 or 3 days or 1, 2, or 4 weeks (5 days/week). The persistence of 7-HEG was studied in mice killed up to 7 days after cessation of the 4-week time-course study. In addition, the formation of O6-(2-hydroxyethyl)guanine and 3-(2-hydroxyethyl)adenine was evaluated in rats exposed to 300 ppm ETO. DNA samples from control and treated animals were analyzed for 7-HEG using neutral thermal hydrolysis, microconcentration, and high-performance liquid chromatography separation with fluorescence detection. Fluorescence-linked high-performance liquid chromatography was used for O6-(2-hydroxyethyl)guanine quantitation, and immunochromatography and gas chromatography-mass spectrometry were used for 3-(2-hydroxyethyl)adenine detection. Analysis of DNA from tissues of control mice and rats revealed the presence of peaks equivalent to 2-6 pmol 7-HEG/mg DNA. In mice exposed to 100 ppm ETO, 7-HEG accumulated to a similar extent in target and nontarget tissues, with adduct concentrations ranging from 17.5 +/- 3.0 (SE) (testis) to 32.9 +/- 1.9 (lung) pmol adduct/mg DNA after 4 weeks of exposure. Concurrent exposures of mice and rats to 100 ppm ETO for 4 weeks led to 2- to 3-fold lower concentrations of 7-HEG in mouse DNA in all tissues compared to rat DNA. 7-HEG disappeared slowly in a nearly linear fashion from the DNA of mouse kidney (t1/2 = 6.9 days) and rat brain and lung (t1/2 = 5.4-5.8 days), which was consistent with the loss of adduct mainly by chemical depurination. In contrast, a more rapid removal of 7-HEG from other mouse (t1/2 = 1.0-2.3 days) and rat (t1/2 = 2.9-4.8 days) tissues was consistent with adduct loss by depurination and DNA repair. Dose-response relationships for 7-HEG were nonlinear in both mice and rats, with the alkylating efficiency of ETO increasing at high exposures.(ABSTRACT TRUNCATED AT 400 WORDS)

Attenuation of cocaine self-administration by chronic oral phendimetrazine in rhesus monkeys.

Chronic treatment with the monoamine releaser d-amphetamine has been consistently shown to decrease cocaine self-administration in laboratory studies and clinical trials. However, the abuse potential of d-amphetamine is an obstacle to widespread clinical use. Approaches are needed that exploit the efficacy of the agonist approach but avoid the abuse potential associated with dopamine releasers. The present study assessed the effectiveness of chronic oral administration of phendimetrazine (PDM), a pro-drug for the monoamine releaser phenmetrazine (PM), to decrease cocaine self-administration in four rhesus monkeys. Each day, monkeys pressed a lever to receive food pellets under a 50-response fixed-ratio (FR) schedule of reinforcement and self-administered cocaine (0.003-0.56 mg/kg per injection, i.v.) under a progressive-ratio (PR) schedule in the evening. After completing a cocaine self-administration dose-response curve, sessions were suspended and PDM was administered (1.0-9.0 mg/kg, p.o., b.i.d.). Cocaine self-administration was assessed using the PR schedule once every 7 days while food-maintained responding was studied daily. When a persistent decrease in self-administration was observed, the cocaine dose-effect curve was re-determined. Daily PDM treatment decreased cocaine self-administration by 30-90% across monkeys for at least 4 weeks. In two monkeys, effects were completely selective for cocaine. Tolerance developed to initial decreases in food-maintained responding in the third monkey and in the fourth subject, fluctuations were observed that were lower in magnitude than effects on cocaine self-administration. Cocaine dose-effect curves were shifted down and/or rightward in three monkeys. These data provide further support for the use of agonist medications for cocaine abuse, and indicate that the promising effects of d-amphetamine extend to a more clinically viable pharmacotherapy.

Magnetodielectric detection of magnetic quadrupole order in Ba(TiO)Cu4(PO4)4 with Cu4O12 square cupolas.

In vortex-like spin arrangements, multiple spins can combine into emergent multipole moments. Such multipole moments have broken space-inversion and time-reversal symmetries, and can therefore exhibit linear magnetoelectric (ME) activity. Three types of such multipole moments are known: toroidal; monopole; and quadrupole moments. So far, however, the ME activity of these multipole moments has only been established experimentally for the toroidal moment. Here we propose a magnetic square cupola cluster, in which four corner-sharing square-coordinated metal-ligand fragments form a noncoplanar buckled structure, as a promising structural unit that carries an ME-active multipole moment. We substantiate this idea by observing clear magnetodielectric signals associated with an antiferroic ME-active magnetic quadrupole order in the real material Ba(TiO)Cu4(PO4)4. The present result serves as a useful guide for exploring and designing new ME-active materials based on vortex-like spin arrangements.

Human exposure and internal dose assessments of acrylamide in food.

This review provides a framework contributing to the risk assessment of acrylamide in food. It is based on the outcome of the ILSI Europe FOSIE process, a risk assessment framework for chemicals in foods and adds to the overall framework by focusing especially on exposure assessment and internal dose assessment of acrylamide in food. Since the finding that acrylamide is formed in food during heat processing and preparation of food, much effort has been (and still is being) put into understanding its mechanism of formation, on developing analytical methods and determination of levels in food, and on evaluation of its toxicity and potential toxicity and potential human health consequences. Although several exposure estimations have been proposed, a systematic review of key information relevant to exposure assessment is currently lacking. The European and North American branches of the International Life Sciences Institute, ILSI, discussed critical aspects of exposure assessment, parameters influencing the outcome of exposure assessment and summarised data relevant to the acrylamide exposure assessment to aid the risk characterisation process. This paper reviews the data on acrylamide levels in food including its formation and analytical methods, the determination of human consumption patterns, dietary intake of the general population, estimation of maximum intake levels and identification of groups of potentially high intakes. Possible options and consequences of mitigation efforts to reduce exposure are discussed. Furthermore the association of intake levels with biomarkers of exposure and internal dose, considering aspects of bioavailability, is reviewed, and a physiologically-based toxicokinetic (PBTK) model is described that provides a good description of the kinetics of acrylamide in the rat. Each of the sections concludes with a summary of remaining gaps and uncertainties.

The implementation of a nurse-provided, ward-based bilevel non-invasive ventilation service.

Bilevel non-invasive ventilation (NIV) is now standard of care for patients with acute hypercapnic respiratory failure (AHRF), and has an increasing role to play in patients with stable chronic hypercapnic respiratory failure (CHRF). The institution of an NIV service in a hospital setting requires major infrastructural and multidisciplinary input to be effective. This paper describes our experiences in setting up a 24-hour, nurse-provided, ward-based NIV service in a new acute teaching hospital in Dublin over a 39-month period. In addition, we provide audit data on 78 patients with AHRF treated with NIV by this service over this time period. The majority of patients (65) had their respiratory acidosis corrected and were discharged home; 11 patients failed NIV and were intubated and mechanically ventilated in the ITU; 13 patients died, 8 from respiratory causes and 5 from non-respiratory causes, indicating the critical nature of this condition.

Cardiac Ischemia Reperfusion Injury Following Instillation of 20 nm Citrate-capped Nanosilver.

BACKGROUND: Silver nanoparticles (AgNP) have garnered much interest due to their antimicrobial properties, becoming one of the most utilized nano-scale materials. However, any potential evocable cardiovascular injury associated with exposure has not been reported to date. We have previously demonstrated expansion of myocardial infarction after intratracheal (IT) instillation of carbon-based nanomaterials. We hypothesized pulmonary exposure to Ag core AgNP induces a measureable increase in circulating cytokines, expansion of cardiac ischemia-reperfusion (I/R) injury and is associated with depressed coronary constrictor and relaxation responses. Secondarily, we addressed the potential contribution of silver ion release on AgNP toxicity. METHODS: Male Sprague-Dawley rats were exposed to 200 µl of 1 mg/ml of 20 nm citrate-capped Ag core AgNP, 0.01, 0.1, 1 mg/ml Silver Acetate (AgAc), or a citrate vehicle by intratracheal (IT) instillation. One and 7 days following IT instillation the lungs were evaluated for inflammation and the presence of silver; serum was analyzed for concentrations of selected cytokines; cardiac I/R injury and coronary artery reactivity were assessed. RESULTS: AgNP instillation resulted in modest pulmonary inflammation with detection of silver in lung tissue and alveolar macrophages, elevation of serum cytokines: G-CSF, MIP-1α, IL-1ß, IL-2, IL-6, IL-13, IL-10, IL-18, IL-17α, TNFα, and RANTES, expansion of I/R injury and depression of the coronary vessel reactivity at 1 day post IT compared to vehicle treated rats. Silver within lung tissue was persistent at 7 days post IT instillation and was associated with an elevation in cytokines: IL-2, IL-13, and TNFα and expansion of I/R injury. AgAc resulted in a concentration dependent infarct expansion and depressed vascular reactivity without marked pulmonary inflammation or serum cytokine response. CONCLUSIONS: Based on these data, IT instillation of AgNP increases circulating levels of several key cytokines, which may contribute to persistent expansion of I/R injury possibly through an impaired vascular responsiveness.