Synthesis and Properties of Ba6Fe2Te3S7, with an Fe Dimer in a Magnetic Singlet State

A new quaternary sulfide telluride, Ba6Fe2Te3S7, was synthesized by a solid-state reaction, and its crystal structure is novel. X-ray diffraction data on powder and single crystals reveal an orthorhombic lattice with a = 9.7543(3) Å, b = 18.2766(6) Å, and c = 12.0549(4) Å, and the noncentrosymmetric space group Cmc21 (No. 36). The properties of the compound were studied by magnetic susceptibility investigations, specific heat measurements, Mössbauer spectroscopy, and density functional theory calculations. Assuming Ba2+ and, as verified by the Mössbauer spectra, Fe3+, the charge balance requires the presence of a polytelluride, suggested to be a straight-chain [Te34-] polyanion. Further, the crystal structure contains [Fe2S7]8- dimers of two vertex-sharing tetrahedra, with a nearly linear Fe-S-Fe atom arrangement. The dimer exhibits antiferromagnetic coupling, with a coupling constant J = -10.5 meV (H = -2JS1S2) and S = 5/2, resulting in a spin singlet ground state. The interdimer magnetic interaction is so weak that the magnetic dimers can be treated as individuals.

Ruthenium-Alloyed Iron Phosphide Single Crystal with Increased Fermi Level for Efficient Hydrogen Evolution

Transition metal phosphide alloying is an effective approach for optimizing the electronic structure and improving the intrinsic performance of the hydrogen evolution reaction (HER). However, obtaining 3d transition metal phosphides alloyed with noble metals is still a challenge owing to their difference in electronegativity, and the influence of their electronic structure modulated by noble metals on the HER reaction also remains unclear. In this study, we successfully incorporated Ru into an Fe₂P single crystal via the Bridgeman method and used it as a model catalyst, which effectively promoted HER. Hall transport measurements combined with first-principles calculations revealed that Ru acted as an electron dopant in the structure and increased the Fermi level, leading to a decreased water dissociation barrier and an improved electron-transfer Volmer step at low overpotentials. Additionally, the (21̅1) facet of Ru-Fe₂P was found to be more active than its (001) facet, mainly due to the lower H desorption barrier at high overpotentials. The synergistic effect of Ru and Fe sites was also revealed to facilitate H* and OH* desorption compared with Fe₂P. Therefore, this study elucidates the boosting effect of Ru-alloyed iron phosphides and offers new understanding about the relationship between their electronic structure and HER performance.

Oxygen deficiency in Sr2FeO4-x: electrochemical control and impact on magnetic properties

The oxygen-deficient system Sr₂FeO_4-x was explored by heating the stoichiometric Fe⁴⁺ oxide Sr₂FeO₄ in well-defined oxygen partial pressures which were controlled electrochemically by solid-state electrolyte coulometry. Samples with x up to about 0.2 were obtained by this route. X-ray diffraction analysis reveals that the K₂NiF₄-type crystal structure (space group I4/mmm) of the parent compound is retained. The lattice parameter a slightly decreases while the c-parameter increases with increasing x, which is in contrast to the Ruddlesden-Popper system Sr₃Fe₂O_7-x and suggests removal of oxygen atoms from FeO₂ lattice planes. The magnetic properties were studied by magnetization, ⁵⁷Fe Mössbauer, and powder neutron diffraction experiments. The results suggest that extraction of oxygen atoms from the lattice progressively changes the elliptical spiral spin ordering of the parent compound to an inhomogeneous magnetic state with coexistence of long-range ordered regions adopting a circular spin spiral and smaller magnetic clusters.

Evolution of transition metal charge states in correlation with the structural and magnetic properties in disordered double perovskites Ca2-xLaxFeRuO6 (0.5 ≤ x ≤ 2)

A series of disordered Ca_1.5La_0.5FeRuO₆, CaLaFeRuO₆ and La₂FeRuO₆ double perovskites were prepared by the solid-state reaction method and investigated by neutron powder diffraction, X-ray absorption near-edge structure (XANES) analysis at the Ru-K edge, Mössbauer spectroscopy, DC magnetization and resistivity measurements. All compounds crystallize in the orthorhombic crystal structure with the space group Pbnm down to 3 K, showing a random distribution of Fe and Ru at the B site. Thermogravimetric analysis indicates oxygen deficiency in the Ca-rich and formal oxygen hyperstoichiometry in the La-rich members of the present series. While Mössbauer spectra verify the Fe³⁺ state for all compositions, the XANES study reveals a variable Ruⁿ⁺ oxidation state which decreases with increasing La content. The end member actually is a Ru³⁺/Ru⁴⁺ compound with possibly some cation vacancies. From magnetic susceptibility and neutron diffraction measurements, the presence of a G-type antiferromagnetic ordering was observed with a drastic increase in transition temperature from 275 K (Ca_1.5La_0.5FeRuO₆) to 570 K (La₂FeRuO₆). Mössbauer spectroscopy confirms the presence of long-range ordering but, due to local variations in the exchange interactions, the magnetic states are microscopically inhomogeneous. All the samples are variable range hopping semiconductors. A complex interplay between structural features, charge states, anion or cation defects, and atomic disorder determines the magnetic properties of the present disordered 3d/4d double perovskite series.

Large Anomalous Hall and Nernst Effects in High Curie-Temperature Iron-Based Heusler Compounds

The interplay between topology and magnetism has recently sparked the frontier studies of magnetic topological materials that exhibit intriguing anomalous Hall and Nernst effects owning to the large intrinsic Berry curvature (BC). To better understand the anomalous quantum transport properties of these materials and their implications for future applications such as electronic and thermoelectric devices, it is crucial to discover more novel material platforms for performing anomalous transverse transport studies. Here, it is experimentally demonstrated that low-cost Fe-based Heusler compounds exhibit large anomalous Hall and Nernst effects. An anomalous Hall conductivity of 250-750 S cm-1 and Nernst thermopower of above 2 µV K-1 are observed near room temperature. The positive effect of anti-site disorder on the anomalous Hall transport is revealed. Considering the very high Curie temperature (nearly 1000 K), larger Nernst thermopowers at high temperatures are expected owing to the existing magnetic order and the intrinsic BC. This work provides a background for developing low-cost Fe-based Heusler compounds as a new material platform for anomalous transport studies and applications, in particular, near and above room temperature.

Hidden Charge Order in an Iron Oxide Square-Lattice Compound

Since the discovery of charge disproportionation in the FeO_{2} square-lattice compound Sr_{3}Fe_{2}O_{7} by Mössbauer spectroscopy more than fifty years ago, the spatial ordering pattern of the disproportionated charges has remained "hidden" to conventional diffraction probes, despite numerous x-ray and neutron scattering studies. We have used neutron Larmor diffraction and Fe K-edge resonant x-ray scattering to demonstrate checkerboard charge order in the FeO_{2} planes that vanishes at a sharp second-order phase transition upon heating above 332 K. Stacking disorder of the checkerboard pattern due to frustrated interlayer interactions broadens the corresponding superstructure reflections and greatly reduces their amplitude, thus explaining the difficulty of detecting them by conventional probes. We discuss the implications of these findings for research on "hidden order" in other materials.

Temporal rarity is a better predictor of local extinction risk than spatial rarity

Spatial rarity is often used to predict extinction risk, but rarity can also occur temporally. Perhaps more relevant in the context of global change is whether a species is core to a community (persistent) or transient (intermittently present), with transient species often susceptible to human activities that reduce niche space. Using 5-12 yr of data on 1,447 plant species from 49 grasslands on five continents, we show that local abundance and species persistence under ambient conditions are both effective predictors of local extinction risk following experimental exclusion of grazers or addition of nutrients; persistence was a more powerful predictor than local abundance. While perturbations increased the risk of exclusion for low persistence and abundance species, transient but abundant species were also highly likely to be excluded from a perturbed plot relative to ambient conditions. Moreover, low persistence and low abundance species that were not excluded from perturbed plots tended to have a modest increase in abundance following perturbance. Last, even core species with high abundances had large decreases in persistence and increased losses in perturbed plots, threatening the long-term stability of these grasslands. Our results demonstrate that expanding the concept of rarity to include temporal dynamics, in addition to local abundance, more effectively predicts extinction risk in response to environmental change than either rarity axis predicts alone.

High-mobility band-like charge transport in a semiconducting two-dimensional metal-organic framework

Metal-organic frameworks (MOFs) are hybrid materials based on crystalline coordination polymers that consist of metal ions connected by organic ligands. In addition to the traditional applications in gas storage and separation or catalysis, the long-range crystalline order in MOFs, as well as the tunable coupling between the organic and inorganic constituents, has led to the recent development of electrically conductive MOFs as a new generation of electronic materials. However, to date, the nature of charge transport in the MOFs has remained elusive. Here we demonstrate, using high-frequency terahertz photoconductivity and Hall effect measurements, Drude-type band-like transport in a semiconducting, π-d conjugated porous Fe₃(THT)₂(NH₄)₃ (THT, 2,3,6,7,10,11-triphenylenehexathiol) two-dimensional MOF, with a room-temperature mobility up to ~ 220 cm² V^-1 s^-1. The temperature-dependent conductivity reveals that this mobility represents a lower limit for the material, as mobility is limited by impurity scattering. These results illustrate the potential for high-mobility semiconducting MOFs as active materials in thin-film optoelectronic devices.

A coronene-based semiconducting two-dimensional metal-organic framework with ferromagnetic behavior

Metal-organic frameworks (MOFs) have so far been highlighted for their potential roles in catalysis, gas storage and separation. However, the realization of high electrical conductivity (>10-3 S cm-1) and magnetic ordering in MOFs will afford them new functions for spintronics, which remains relatively unexplored. Here, we demonstrate the synthesis of a two-dimensional MOF by solvothermal methods using perthiolated coronene as a ligand and planar iron-bis(dithiolene) as linkages enabling a full π-d conjugation. This 2D MOF exhibits a high electrical conductivity of ~10 S cm-1 at 300 K, which decreases upon cooling, suggesting a typical semiconductor nature. Magnetization and 57Fe Mössbauer experiments reveal the evolution of ferromagnetism within nanoscale magnetic clusters below 20 K, thus evidencing exchange interactions between the intermediate spin S = 3/2 iron(III) centers via the delocalized π electrons. Our results illustrate that conjugated 2D MOFs have potential as ferromagnetic semiconductors for application in spintronics.

Crystal and magnetic structure of antiferromagnetic Mn2PtPd

We have investigated the crystal and magnetic structure of Mn₂PtPd alloy using powder x-ray and neutron diffraction experiments. This compound is believed to belong to the Heusler family having crystal symmetry I4/mmm (TiAl₃-type). However, in this work we found that the Pd and Pt atoms are disordered and thus Mn₂PtPd crystallizes in the L1₀ structure having P4/mmm symmetry (CuAu-I type) like MnPt and MnPd binary alloys. The lattice constants are a  =  2.86 Å and c  =  3.62 Å at room temperature. Mn₂PtPd has a collinear antiferromagnetic spin structure below the Néel temperature T _N  =  866 K, where Mn moments of ~4 µ _B lie in the ab-plane. We observed a strong change in the lattice parameters near T _N. The sample exhibits metallic behaviour, where electrical resistivity and carrier concentration are of the order of 10^-5 Ω cm and 10²¹ cm^-3, respectively.

Verwey-type charge ordering transition in an open-shell p-electron compound

The Verwey transition in Fe₃O₄, a complex structural phase transition concomitant with a jump in electrical conductivity by two orders of magnitude, has been a benchmark for charge ordering (CO) phenomena in mixed-valence transition metal materials. CO is of central importance, because it frequently competes with functional properties such as superconductivity or metallic ferromagnetism. However, the CO state in Fe₃O₄ turned out to be complex, and the mechanism of the Verwey transition remains controversial. We demonstrate an archetypical Verwey-type transition in an open p-shell anionic mixed-valence compound using complementary diffraction and spectroscopic techniques. In Cs₄O₆, a phase change from a cubic structure with a single crystallographic site for the molecular O₂^x- building units to a tetragonal structure with ordered superoxide O₂^- and peroxide O₂^2- entities is accompanied by a drastic drop in electronic conductivity and molecular charge fluctuation rates. The simple CO pattern of molecular units and the lack of magnetic order suggest Cs₄O₆ as a model system for disentangling the complex interplay of charge, lattice, orbital, and spin degrees of freedom in Verwey-type CO processes.

Successive Phase Transitions in Fe2+ Ladder Compounds Sr2Fe3Ch2O3 (Ch = S, Se)

Small single crystals of Sr₂Fe₃Ch₂O₃ (Ch = S, Se) have been synthesized by flux methods, and bulk materials have been obtained by solid state reactions. Both compounds are isostructural to the compound Sr₂Co₃S₂O₃ (space group Pbam), which contains a novel hybrid spin ladder: a combination of a 2-leg rectangular ladder and a necklace ladder. The 2-leg ladder acts as a well-defined magnetic entity, while intimate magnetic coupling to the necklace ladder induces three successive phase transitions in the range of 40-120 K in each composition (Ch = S or Se), as revealed by Mössbauer spectroscopy, thermodynamics, and magnetometry. The complex magnetic behaviors can be explained by the unique spin-lattice topology.

Canted Antiferromagnetism on Rectangular Layers of Fe2+ in Polymorphic CaFeSeO

From stoichiometric amounts of CaO, Fe, and Se, pure powders and single crystals of quaternary [Formula: see text] can be obtained by solid-state reaction and self-flux growth, respectively. The as-synthesized compound exhibits a polymorphic crystal structure, where the two modifications have different stacking sequences of [Formula: see text] layers. The two polymorphs have similar unit cells but different crystal symmetries (Cmc2₁ and Pnma), of which the former is non-centrosymmetric. Fe is divalent (d⁶) and high-spin, as proven by X-ray spectroscopy, Mössbauer spectroscopy, and powder neutron diffraction data. The latter two, in combination with magnetic susceptibility and specific heat data, reveal a long-range antiferromagnetic spin order (T_N = 160 K) with a minor spin canting. CaFeSeO is an electronic insulator, as confirmed by resistivity measurements and density functional theory calculations. The latter also suggest a relatively small energy difference between the two polymorphs, explaining their intimate intergrowth.

Familiar Correlates of Gang Membership: An Exploratory Study of Mexican-American Youth

The differences between the families of youths who are gang members versus youths not in gangs were investigated. Data were collected from thirty mothers using a semi-structured interview. Results indicated that family related variables distinguish the families of gang members from the control families. Specifically, youths in gangs are more likely to come from families which put less emphasis on intrafamilial socialization, youth supervision, and outward expression of affection. Furthermore, mothers of youths who were gang members appeared more dissatisfied and fatalistic. Theoretical and practical implications are discussed.

Phonon-Modulated Magnetic Interactions and Spin Tomonaga-Luttinger Liquid in the p-Orbital Antiferromagnet CsO2

The magnetic response of antiferromagnetic CsO2, coming from the p-orbital S=1/2 spins of anionic O2(-) molecules, is followed by 133Cs nuclear magnetic resonance across the structural phase transition occurring at T(s1)=61  K on cooling. Above T(s1), where spins form a square magnetic lattice, we observe a huge, nonmonotonic temperature dependence of the exchange coupling originating from thermal librations of O2(-) molecules. Below T(s1), where antiferromagnetic spin chains are formed as a result of p-orbital ordering, we observe a spin Tomonaga-Luttinger-liquid behavior of spin dynamics. These two interesting phenomena, which provide rare simple manifestations of the coupling between spin, lattice, and orbital degrees of freedom, establish CsO2 as a model system for molecular solids.

k=0 magnetic structure and absence of ferroelectricity in SmFeO3

SmFeO3 has attracted considerable attention very recently due to its reported multiferroic properties above room temperature. We have performed powder and single crystal neutron diffraction as well as complementary polarization dependent soft X-ray absorption spectroscopy measurements on floating-zone grown SmFeO3 single crystals in order to determine its magnetic structure. We found a k=0 G-type collinear antiferromagnetic structure that is not compatible with inverse Dzyaloshinskii-Moriya interaction driven ferroelectricity. While the structural data reveal a clear sign for magneto-elastic coupling at the Néel-temperature of ∼675  K, the dielectric measurements remain silent as far as ferroelectricity is concerned.

Abstract P1-04-16: Multi-center experience with CELLSEARCH® circulating tumor cell kit on patients with metastatic breast cancer

Background: Clinical studies have shown that circulating tumor cell (CTC) detection via the CELLSEARCH® assay is a validated prognostic marker for the prediction of progression-free survival (PFS) and overall survival (OS) in metastatic breast cancer (mBC) patients. We evaluated the impact of CTC testing on OS using real-world observational data from multiple centers.

Material and Methods: Electronic medical records (EMR) were used to identify patients who were: (i) women > 18 years diagnosed with mBC on or after their date of registration, (ii) registered to the EMR system on or after 4/1/2010, and (iii) followed for at least 2 months from the time of metastases. Patients who had CTC testing were required to have at least 1 valid CTC test result. OS among mBC patients with CTC testing was compared to a cohort of patients without CTC testing (non-CTC) using a Cox model controlling for age, race, hormone receptor status, and scanning frequency.

Results: CTC patients were treated in 43 centers and grouped into two main sites based on region (N1 = 123, N2 = 240); non-CTC patients were treated in 58 different centers (N = 1,115). Mean (SD) ages of CTC and non-CTC patients were 66 (13) and 65 (14) years, respectively. ER or PR+ patients comprised 77% of the CTC tested and 72% of the non-CTC samples. The majority of patients in both cohorts were Caucasian (83% - CTC, 57% - non-CTC). A Cox model comparing OS between CTC and non-CTC patients did not show a survival benefit due to CTC testing. Comparing CTC testing frequency between the two sites showed that, on average, the 123 patients from site 1 were tested more frequently than the 240 patients in site 2 (0.6 vs. 0.3 CTC tests/month, p-value<0.001). The model that compared OS between CTC patients from site 1 showed a 43% reduction in risk of death (HR = 0.58, p-value = 0.005) compared to the overall cohort of non-CTC patients. Patients from site 2 did not show a reduction in risk of death compared to non-CTC patients, but a significant interaction between CTC testing and race (Caucasian vs. non-Caucasian) (p-value = 0.005) was observed. For Caucasians, CTC patients exhibited a 37% reduction in risk of death compared to non-CTC patients; reduction in risk of death was not observed for non-Caucasians CTC patients. This interaction (p-value = 0.005) was consistent among the subset of ER or PR+ Caucasian patients relative to non-CTC ER or PR+ Caucasian patients (HR = 0.55). For site 1, the subset of ER or PR+ CTC also had a lower risk of dying compared to ER or PR+ non-CTC (HR = 0.47, p-value = 0.004).

Discussion: These results suggest that frequent serial testing for CTC may be associated with better prognosis compared to no CTC testing or even infrequent CTC testing. By more frequent monitoring, the assessment of serial CTCs provide clinicians with more frequent information, which in turn can provide a clearer understanding of a patient's cancer progression in a metastatic setting. One limitation of these results is the difficulty in ruling out other potential drivers. Particularly, results regarding the racial differences in outcomes where race might serve as a proxy for a number of factors such as severity of disease which is difficult to derive from a retrospective observational database.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P1-04-16.

Predicting invasion in grassland ecosystems: is exotic dominance the real embarrassment of richness?

Invasions have increased the size of regional species pools, but are typically assumed to reduce native diversity. However, global-scale tests of this assumption have been elusive because of the focus on exotic species richness, rather than relative abundance. This is problematic because low invader richness can indicate invasion resistance by the native community or, alternatively, dominance by a single exotic species. Here, we used a globally replicated study to quantify relationships between exotic richness and abundance in grass-dominated ecosystems in 13 countries on six continents, ranging from salt marshes to alpine tundra. We tested effects of human land use, native community diversity, herbivore pressure, and nutrient limitation on exotic plant dominance. Despite its widespread use, exotic richness was a poor proxy for exotic dominance at low exotic richness, because sites that contained few exotic species ranged from relatively pristine (low exotic richness and cover) to almost completely exotic-dominated ones (low exotic richness but high exotic cover). Both exotic cover and richness were predicted by native plant diversity (native grass richness) and land use (distance to cultivation). Although climate was important for predicting both exotic cover and richness, climatic factors predicting cover (precipitation variability) differed from those predicting richness (maximum temperature and mean temperature in the wettest quarter). Herbivory and nutrient limitation did not predict exotic richness or cover. Exotic dominance was greatest in areas with low native grass richness at the site- or regional-scale. Although this could reflect native grass displacement, a lack of biotic resistance is a more likely explanation, given that grasses comprise the most aggressive invaders. These findings underscore the need to move beyond richness as a surrogate for the extent of invasion, because this metric confounds monodominance with invasion resistance. Monitoring species' relative abundance will more rapidly advance our understanding of invasions.

Lattice instability and competing spin structures in the double perovskite insulator Sr2FeOsO6

The semiconductor Sr2FeOsO6, depending on temperature, adopts two types of spin structures that differ in the spin sequence of ferrimagnetic iron-osmium layers along the tetragonal c axis. Neutron powder diffraction experiments, 57Fe Mössbauer spectra, and density functional theory calculations suggest that this behavior arises because a lattice instability resulting in alternating iron-osmium distances fine-tunes the balance of competing exchange interactions. Thus, Sr2FeOsO6 is an example of a double perovskite, in which the electronic phases are controlled by the interplay of spin, orbital, and lattice degrees of freedom.

Vision in athletes with intellectual disabilities: the need for improved eyecare

BACKGROUND

Special Olympics provides sporting opportunities for people with intellectual disabilities (ID), and Lions Clubs International Opening Eyes GB offers vision screening for athletes at Special Olympics Games.

METHODS

Opening Eyes GB screened the vision of 505 UK athletes at its inaugural event in 2001. The results were analysed and are presented here.

RESULTS

Results showed that athletes do not differ from other people with ID in being at high risk of ocular and visual defects and many are not accessing eyecare. 15% reported never having an optometric eye examination, and yet 19% of these athletes had a significant refractive error, 32% had ocular anomalies and 6% were visually impaired. Overall, findings confirmed the high prevalence of refractive errors and strabismus amongst people with ID. 40% of athletes had ocular abnormalities, including 15.6% with blepharitis, a readily treatable condition that causes discomfort. 9% had lens opacities, of which half were probably impairing sight. An important finding was that many athletes have reduced vision and 14% could be classified as visually impaired (WHO definition) even when refractive errors were fully corrected.

CONCLUSIONS

Special Olympics athletes should be encouraged to have regular eye examinations (as indeed, should all people with ID), and educators, carers and coaches need appropriate information about the visual status of their charges.

Magnetism, charge order, and giant magnetoresistance in SrFeO(3-delta) single crystals

The electronic and magnetic properties of SrFeO(3-delta) single crystals with controlled oxygen content (0< or =delta< or =0.19) have been studied systematically by susceptibility, transport, and spectroscopic techniques. An intimate correlation between the spin-charge ordering and the electronic transport behavior is found. Giant negative as well as positive magnetoresistance are observed.

Abatement of cockroach allergen (Bla g 1) in low-income, urban housing: A randomized controlled trial

BACKGROUND

Clinically relevant reductions in exposure to cockroach allergen, an important risk factor for asthma in inner-city households, have proven difficult to achieve in intervention trials.

OBJECTIVE

This study investigated a method for the abatement of cockroach allergen in low-income, urban homes. The goal was to reduce mean Bla g 1 concentrations below the previously proposed thresholds for allergic sensitization and asthma morbidity.

METHODS

A prerandomized, nonmasked trial with 16 intervention and 15 control homes was conducted. Study inclusion was based on 50 to 500 cockroaches trapped in a 3-day period. The interventions consisted of occupant education, placement of insecticide bait, and professional cleaning. Vacuumed dust and multiple swab samples were collected at 0, 1, 2, 4, and 6 months in intervention homes and at 0 and 6 months in control homes. Room maps containing cockroach and allergen data were used to guide and monitor the interventions.

RESULTS

From 0 to 6 months among intervention homes, geometric mean Bla g 1 concentrations (U/g dust) decreased from 633 to 24 on kitchen floors (96% reduction), from 25 to 4.3 on living room floors/sofas (83% reduction), from 46 to 7.3 on bedroom floors (84% reduction), and from 6.1 to 1.0 in bedroom beds (84% reduction). These reductions, with the exception of that on the bedroom floor (P =.06), were statistically significant relative to changes in control homes.

CONCLUSIONS

Substantial reductions in cockroach allergen levels can be achieved in inner-city homes. In this study, allergen levels were reduced below the sensitization threshold (2 U/g) in beds, arguably the most relevant site for exposure, and below the asthma morbidity threshold (8 U/g) on bedroom floors and living room floors/sofas. The level on kitchen floors, although reduced 96%, remained above the asthma morbidity threshold. Future studies will test the intervention's effectiveness in asthma prevention trials.

Pressure-induced quenching of the Jahn-Teller distortion and insulator-to-metal transition in LaMnO(3)

LaMnO(3) was studied by synchrotron x-ray diffraction, optical spectroscopies, and transport measurements under pressures up to 40 GPa. The cooperative Jahn-Teller (JT) distortion is continuously reduced with increasing pressure. There is strong indication that the JT effect and the concomitant orbital order are completely suppressed above 18 GPa. The system, however, retains its insulating state to approximately 32 GPa, where it undergoes a bandwidth-driven insulator-metal transition. Delocalization of electron states, which suppresses the JT effect but is insufficient to make the system metallic, appears to be a key feature of LaMnO(3) at 20-30 GPa.

The effect of grazing on the spatial heterogeneity of vegetation

Grazing can alter the spatial heterogeneity of vegetation, influencing ecosystem processes and biodiversity. Our objective was to identify why grazing causes increases in the spatial heterogeneity of vegetation in some cases, but decreases in others. The immediate effect of grazing on heterogeneity depends on the interaction between the spatial pattern of grazing and the pre-existing spatial pattern of vegetation. Depending on the scale of observation and on the factors that determine animal distribution, grazing patterns may be stronger or weaker than vegetation patterns, or may mirror the spatial structure of vegetation. For each possible interaction between these patterns, we make a prediction about resulting changes in the spatial heterogeneity of vegetation. Case studies from the literature support our predictions, although ecosystems characterized by strong plant-soil interactions present important exceptions. While the processes by which grazing causes increases in heterogeneity are clear, how grazing leads to decreases in heterogeneity is less so. To explore how grazing can consistently dampen the fine-scale spatial patterns of competing plant species, we built a cell-based simulation model that features two competing plant species, different grazing patterns, and different sources of vegetation pattern. Only the simulations that included neighborhood interactions as a source of vegetation pattern produced results consistent with the predictions we derived from the literature review.

Risk factors for all-terrain vehicle injuries: a national case-control study

A case-control study design was used to determine and quantify all-terrain vehicle (ATV) risk factors. The analysis was based on the results of two national probability surveys conducted in 1997: a survey of injured ATV drivers treated in hospital emergency departments and a survey of the general population of ATV users. Cases were drawn from the injury survey; controls (ATV drivers who had not been injured) were drawn from the user survey. Risk factors were quantified by means of a binary logistic regression analysis. After adjustment for covariates, injury risks were systematically related to a number of driver characteristics (age, gender, driving experience), driver use patterns (monthly driving times, recreational vs. nonrecreational use), and vehicle characteristics (number of wheels, engine size). The results of the analysis suggest that future safety efforts should focus on reducing child injuries, getting new drivers to participate in hands-on training programs, and encouraging consumers to dispose of the three-wheel ATVs still in use.

The Effect of epsilon-aminocaproic acid on perioperative blood loss in patients with idiopathic scoliosis undergoing posterior spinal fusion: a preliminary prospective study

STUDY DESIGN

A prospective study evaluating the efficacy of epsilon-aminocaproic acid (EACA) in decreasing perioperative blood loss in idiopathic scoliosis.

OBJECTIVES

To compare the perioperative blood loss and need for blood replacement in two groups of patients undergoing surgery for idiopathic scoliosis. One group received intraoperative EACA; the other did not and served as controls.

SUMMARY OF BACKGROUND DATA

Excessive blood loss increases the operative time, risk for blood product disease transmission, postoperative complications, and costs associated with posterior spinal fusion and instrumentation. EACA is an antifibrinolytic agent that has been shown to be effective in reducing perioperative blood loss during pediatric cardiothoracic surgical procedures. We hypothesized that it would also be effective in lowering blood loss during posterior spinal fusion for idiopathic scoliosis.

METHODS

We compared the perioperative blood loss of 28 consecutive pediatric patients with idiopathic scoliosis who underwent posterior spinal fusion and received intraoperative EACA with 31 consecutive patients who did not receive this medication and served as a control group.

RESULTS

The patients in both groups were similar. Patients in the EACA group demonstrated statistically significant decreases in total estimated perioperative blood loss and the need for autologous blood transfusion. The patients in the EACA group had no intraoperative or postoperative complications related to the use of this medication.

CONCLUSIONS

Based on these preliminary findings, we believe that EACA is helpful in decreasing blood loss in patients undergoing posterior spinal fusion and instrumentation, and may decrease the number of autologous units needed to maintain safe perioperative hemoglobin levels, thereby improving safety and lowering cost associated with scoliosis surgery.

Employee privacy: legal and research developments and implications for personnel administration

The contemporary emphasis on privacy has created a myriad of complex personnel problems and associated approaches to handle them. These privacy-oriented problems generally involve social, ethical, legal, managerial, and even political considerations. Personnel administrators are constantly confronted with the privacy issue. This article attempts to synthesize privacy information relevant to personnel administration, and to provide personnel administrators with managerial guidance for handling employee privacy problems in the work environment. It places particular emphasis on differentiating between ethical and legal aspects of privacy in our society, and, accordingly, on clarifying existing confusion over the impact of so-called "privacy laws" on personnel administration.

Increased CYP2J expression and epoxyeicosatrienoic acid formation in spontaneously hypertensive rat kidney

Epoxyeicosatrienoic acids (EETs) are major products of cytochrome P450 (CYP)-catalyzed metabolism of arachidonic acid in the kidney. The potent effect of EETs on renal vascular tone and tubular ion and water transport implicates their role in the regulation of renal function and blood pressure. The present study was designed to test the hypothesis that CYP-catalyzed EET formation was altered in the spontaneously hypertensive rat (SHR) kidney. The formation of 14,15- and 11,12-EET was approximately 2-fold higher in incubations of arachidonic acid with SHR renal cortical microsomes relative to microsomes from normotensive Wistar-Kyoto (WKY) rats. This was consistent with increased expression of a CYP2J2 immunoreactive protein in the SHR cortex and outer medulla. In contrast, there was no significant difference in the levels of the CYP2E and CYP2C epoxygenases in SHR and WKY kidneys. Protein and RNA analysis suggests that the CYP2J2 immunoreactive protein that is overexpressed in the SHR kidney is distinct from the known rat CYP2J isoforms. EET formation also was documented in vivo from measurements of urinary EET excretion. Importantly, the excretion rates of 14,15-, and 11,12-EETs were 2.5- and 1.8-fold higher, respectively, in SHR than WKY kidney. These studies provide both in vitro and in vivo evidence for increased EET formation in the SHR kidney and identify a novel CYP2J2 immunoreactive protein that is differentially expressed in the hypertensive kidney. In light of the known biological properties of the EETs, these findings may be important in elucidating the mechanisms that control renal vascular tone and tubular ion transport in the SHR.