Relative Iron Content Research Articles

Temporal and spatial variations in the physical and chemical properties of anaerobic granular sludge within a Pilot Spiral Symmetry Stream Anaerobic Bioreactor

Anaerobic granular sludge (AGS) determines the high performance of the bioreactor. To study the regionalization of granular sludge in the bioreactor, a Pilot Spiral Symmetry Stream Anaerobic Bioreactor (P-SSSAB) was established over 216 days, divided into three zones (I, II, and III) from bottom to top. AGS at the bottom of P-SSSAB had a higher porosity (60.35 %–83.27 %) and more suitable settling velocity (60 m/h) when the particle size range was 1.0–2.0 mm. This proved the better metabolic activity and superior settling performance in zone I than in zones II and III. In addition, the elemental composition of AGS in various zones was analyzed. The relative content of iron (5.66 %, 3.36 %, and 1.38 %, respectively) and sulfur (2.47 %, 2.19 %, and 1.49 %, respectively) in zone I, II, and III tended to decrease with the height of P-SSSAB. This also verified the better mass transfer performance and operational stability in lower zone than in upper zone. However, the monitoring of bed temperature in various zones revealed that the microbial activity in zone I was 6.7×10−12~3.5×10−2 times and 1.8×10−15~1.4×10−3 times that in zones II and III, respectively, which indicated that the unit activity of AGS in zone I was the worst. It indicated that AGS in lower zone had poor unit activity but had the highest unit capacity due to the high sludge concentration. Besides, the unit capacity of the upper zone was too weak to produce enough alkalinity to neutralize acid produced by excessive hydrolysis and acidification in lower zone, resulting in the worst treatment efficiency of the upper zone. Therefore, temperature and concentration ratios under various spatial distributions in bioreactors are vital to the overall sewage treatment stability and efficiency of bioreactors in actual engineering applications.

Automatic Segmentation and Quantification of Nigrosome-1 Neuromelanin and Iron in MRI: A Candidate Biomarker for Parkinson's Disease.

There is a lack of automated tools for the segmentation and quantification of neuromelanin (NM) and iron in the nigrosome-1 (N1). Existing tools evaluate the N1 sign, i.e., the presence or absence of the "swallow-tail" in iron-sensitive MRI, or globally analyze the MRI signal in an area containing the N1, without providing a volumetric delineation. Present an automated method to segment the N1 and quantify differences in N1's NM and iron content between Parkinson's disease (PD) patients and healthy controls (HCs). Study whether N1 degeneration is clinically related to PD and could be used as a biomarker of the disease. Prospective. Seventy-one PD (65.3 ± 10.3 years old, 34 female/37 male); 30 HC (62.7 ± 7.8 years old, 17 female/13 male). 3 T Anatomical T1-weighted MPRAGE, NM-MRI T1-weighted gradient with magnetization transfer, susceptibility-weighted imaging (SWI). N1 was automatically segmented in SWI images using a multi-image atlas, populated with healthy N1 structures manually annotated by a neurologist. Relative NM and iron content were quantified and their diagnostic performance assessed and compared with the substantia nigra pars compacta (SNc). The association between image parameters and clinically relevant variables was studied. Nonparametric tests were used (Mann-Whitney's U, chi-square, and Friedman tests) at P = 0.05. N1's relative NM content decreased and relative iron content increased in PD patients compared with HCs (NM-CRHC = 22.55 ± 1.49; NM-CRPD = 19.79 ± 1.92; NM-nVolHC = 2.69 × 10-5 ± 1.02 × 10-5; NM-nVolPD = 1.18 × 10-5 ± 0.96 × 10-5; Iron-CRHC = 10.51 ± 2.64; Iron-CRPD = 19.35 ± 7.88; Iron-nVolHC = 0.72 × 10-5 ± 0.81 × 10-5; Iron-nVolPD = 2.82 × 10-5 ± 2.04 × 10-5). Binary logistic regression analyses combining N1 and SNc image parameters yielded a top AUC = 0.955. Significant correlation was found between most N1 parameters and both disease duration (ρNM-CR = -0.31; ρiron-CR = 0.43; ρiron-nVol = 0.46) and the motor status (ρNM-nVol = -0.27; ρiron-CR = 0.33; ρiron-nVol = 0.28), suggesting NM reduction along with iron accumulation in N1 as the disease progresses. This method provides a fully automatic N1 segmentation, and the analyses performed reveal that N1 relative NM and iron quantification improves diagnostic performance and suggest a relative NM reduction along with a relative iron accumulation in N1 as the disease progresses. 1 TECHNICAL EFFICACY: Stage 1.

Effect of partial substitution of iron for group IV elements on the structure and superconducting properties of the Fe(Se-=SUB=-0.2-=/SUB=-Te-=SUB=-0.8-=/SUB=-)-=SUB=-0.82-=/SUB=- compound

The structure and superconducting properties of the Fe1-x(A)x(Se0.2Te0.8)0.82 (x = 0.1, 0.2) compound, where A is Cu, Zn, Bi or Group IV elements (Pb, Sn, Ge), were studied. It was shown that the effect of substitution of some iron atoms on the structure and superconducting properties of the Fe(Se,Te) compound depends on whether a solid solution with a substituting element was formed. If complete dissolution of the replacement element occured (Cu, Zn), then a significant degradation of the superconducting properties was observed. If a separate chalcogenide phase was formed (substitution by Pb, Sn, Ge), then a slight change in the superconducting properties was observed. Such a slight change and even improvement in the superconducting properties upon precipitation of the chalcogenide phase can be associated with both the positive effect of an increase in the relative content of iron and a decrease in the number of iron atoms in the interstitial sites of the β-phase. The preservation of the superconducting properties of the Fe(Se,Te) compound with a small substitution of iron for group IV elements can be used to create wires based on Fe(Se,Te), since impurity chalcogenide particles can act as effective pinning centers. Keywords: Iron-based superconductor, FeSeTe, critical parameters, substitution, structure, electrical resistivity, magnetoresistance, pressure effect.

Влияние частичного замещения железа на элементы IV группы на структуру и сверхпроводящие свойства соединения Fe(Se-=SUB=-0.2-=/SUB=-Te-=SUB=-0.8-=/SUB=-)-=SUB=-0.82-=/SUB=-

The structure and superconducting properties of the Fe1 – x(A)x(Se0.2Te0.8)0.82 (x = 0.1, 0.2) compound, where A is Cu, Zn, Bi or Group IV elements (Pb, Sn, Ge), were studied. It was shown that the effect of substitution of some iron atoms on the structure and superconducting properties of the Fe(Se,Te) compound depends on whether a solid solution with a substituting element was formed. If complete dissolution of the replacement element occured (Cu, Zn), then a significant degradation of the superconducting properties was observed. If a separate chalcogenide phase was formed (substitution by Pb, Sn, Ge), then a slight change in the superconducting properties was observed. Such a slight change and even improvement in the superconducting properties upon precipitation of the chalcogenide phase can be associated with both the positive effect of an increase in the relative content of iron and a decrease in the number of iron atoms in the interstitial sites of the β phase. The preservation of the superconducting properties of the Fe(Se,Te) compound with a small substitution of iron for group IV elements can be used to create wires based on Fe(Se,Te), since impurity chalcogenide particles can act as effective pinning centers.

Detailed Chemical Analysis of Unusually Weathered Rocks

Objectives: This study aimed to conduct a detailed chemical analysis of the Samanalawewa dam to provide information on its weathering conditions. Method: The mineralogical composition of the dam was analyzed by powder Xray diffraction (PXRD), atomic absorption spectroscopy (AAS), gravimetric, and X-ray fluorescence (XRF) analysis in order to identify chemical changes that have taken place. Findings: Widespread discoloured (brick red) and crushable areas in the dam and the quarry site indicate weathering of the compositional rocks. Each weathered rock sample showed a similar compositional pattern to each other as well as charnockite (CHA) rather than the other structural rocks of the dam; biotite gneiss (BIO), garnet biotite sillimanite gneiss (GAR), and limestone (LIM) indicating that only CHA has been weathered rapidly. Since LIM is not affected and the contact water (pH; reservoir 6.79 - 7.12 and holes in the quarry site 6.43-6.78) is almost neutral, this rapid weathering has not been governed by general chemical weathering processes like acid rains or stormwater. The relative contents of aluminium and magnesium have decreased during the weathering process while increasing the relative content of iron as well as sodium, which is a mobile element. The potassium content also has not decreased significantly. Moreover, chemical weathering indices like chemical index of alteration (CIA) and chemical index of weathering (CIW) values for completely weathered rocks were less than 50 revealing their unsuitability to assess the degree of weathering of the Samanalawewa dam. Novelty: Charnockite in the Samanalawewa dam has been weathered rapidly and chemical weathering indices; CIA and CIW are not valid to assess its degree of weathering. Keywords: Metamorphic; Charnockite; Rock weathering; Rock composition; Chemical weathering indices

Feasibility study of Mössbauer spectroscopy as a tool to explore PVC-plasticized potentiometric sensor membranes

There is a serious lack of instrumental studies of polymeric membrane ion sensors that would give reliable information on the chemistry behind the sensor response. These types of studies are quite challenging due to the low content of species of interest in the membrane material and due to specific features of plasticized polymeric sensor membranes. Mössbauer spectroscopy is a powerful tool for studying local chemical environment of the probe atom. In this research we explored the forms of iron existence in different PVC-plasticized membranes containing Fe-binding ligand and cation-exchanger. In order to be able to observe Mössbauer effect we employed 57Fe-enriched sample solutions to soak the membranes and performed the measurements at 80 K to increase the recoil-free factor. It was found that the chemical forms of iron are different in membranes containing the ion-exchanger and those containing both ion-exchanger and the ligand. The relative content of iron in various forms was estimated. It was also observed that iron ions enter into the «dummy» membranes with no ligand and ion-exchanger, however in very small amounts.

Synthesis, Structure and Electromagnetic Properties of Nanocomposites with Three-component FeCoNi Nanoparticles

Infrared heating was used to synthesize FeCoNi/С nanocomposites, where nanoparticles of FeCoNi ternary alloy are stabilized and uniformly distributed in the carbon matrix volume. The authors studied the impact of synthesis temperature and percentage ratio of metals upon the structure, composition and electromagnetic properties. X-ray phase analysis and Mossbauer spectroscopy showed that ternary alloy nanoparticles with different compositions and crystalline lattice types can be formed with the rise in synthesis temperature and iron concentration. Resonator method was used to examine frequency dependencies of relative complex dielectric and magnetic permeabilities of nanocomposites in the range of 3–12 GHz. Calculation of reflection coefficient based on experimental permeability data showed that by varying synthesis temperature and percentage ratio of metals one can control the frequency range of effective absorption of electromagnetic waves. It was established that increase in relative iron content from 33 to 50 rel.% leads to the shift of minimal electromagnetic wave reflection coefficient band from f ~ 12+ GHz to frequency f ~ 6 GHz at identical absorber thickness.

The Iron State in Spleen and Liver Tissues from Patients with Hematological Malignancies Studied Using Magnetization Measurements and Mössbauer Spectroscopy

In this overview, we present the results of the study of spleen and liver tissues taken from healthy donors in comparison with those from patients with (i) non-Hodgkin B-cell lymphomas, namely, mantle cell lymphoma and marginal zone B-cell lymphoma, (ii) acute myeloid leukemia, and (iii) primary myelofibrosis. The study was carried out using Mössbauer spectroscopy and magnetization measurements for the analysis of ferritin-like iron in spleen and liver tissues. Magnetization measurements demonstrated small differences in the saturation magnetic moments and revealed additional paramagnetic components. Two liver samples demonstrated unusual behavior of the magnetic moment when the zero-field-cooled curve was over the field-cooled curve in the temperature range between ~40 and ~70 K. Relative iron content variations in the tissue cells as well as small variations in the 57Fe hyperfine parameters were demonstrated for healthy and patients' spleen and liver tissues on the base of measured Mössbauer spectra. The results obtained permit us to suggest small differences in the ferritin iron core structure in spleen and liver tissues from healthy donors and patients with hematological malignancies.

Synthesis and Magnetic Properties of Fe–Co–Ni/С Nanocomposites

Nanoparticles of the Fe–Co–Ni ternary alloy, encapsulated in the carbon matrix of nanocomposites, have been synthesized, The structure, phase composition, and magnetic properties of the obtained materials have been determined with the help of diffractometry and magnetometry. It has been established that nanoparticles of the ternary alloy are formed due to solution of cobalt in the Fe–Ni alloy. The composition of the nanoparticles of the alloy depends on the mass percent ratio of the metas in the precursor. With growth of the iron content, nanoparticles of the ternary alloy with various composition are formed with FCC and BCC crystal lattice structure. As the synthesis temperature and relative iron content are increased, the magnetization of the Fe–Co–Ni/C nanocomposites increases from 26 to 157 A·m2/kg. The coercive force is determined by the synthesis temperature, the size of the nanoparticles, and the composition of the alloy, and its value varies from 330 to 43 Oe.

Incident risk and progression of cerebral microbleeds in healthy adults: a multi-occasion longitudinal study

Decline in cerebrovascular health complicates brain aging, and development of cerebral microbleeds (CMBs) is one of its prominent indicators. In a large sample of healthy adults (N = 251, age 18–78 years at baseline, 70% women), the contributions of chronological age and vascular health indicators to the risk of developing a CMB, as well as the change in CMB size and iron content, were examined in a prospective 8-year longitudinal study using susceptibility weighted imaging. Twenty-six persons (10.4%), most of whom were 40 years of age or older, had at least 1 CMB during the study. Older age was associated with greater risk for developing a CMB (odds ratio 1.03). Elevation of combined metabolic syndrome indicators (b = 0.15, p = 0.001) conferred additional risk (odds ratio 1.02). High body mass index exacerbated the risk associated with poor vascular health (b = 0.75, p < 0.001) and frequent exercise mitigated it (b = −0.46, p = 0.03). CMBs persisted over time, yet their volume decreased (mean change = −0.32, p < 0.05), whereas their relative iron content remained stable (mean change = −0.14, p = 0.05). We conclude that although developing a CMB is unlikely during normal aging, risk increases with declining vascular health, which is modifiable via behavioral and pharmaceutical intervention.

Comparison of microstructure changes and irradiation induced growth of E635 alloy under neutron irradiation influence

Model samples of zirconium E635 alloy after rolling, annealing, quenching were subjected to reactor irradiation in BOR 60 up to a fluence ∼ 1026 m-2. The Mössbauer studies data on the state of iron in the original samples previously subjected to rolling, annealing and quenching, and on the irradiated alloy samples are given. It is revealed that in the initial samples iron is in different intermetallic compounds, and also partly in the solid solution. During irradiation the iron atoms move from one type of intermetallic compounds to another one and in to the solid solution. Data on the relative content of iron in different phases and compounds are compared with the results of irradiation-induced growth strain measurements. The correlation between irradiation-induced grows and iron atoms redistribution in alloys is found.

On the heterogeneous nucleation of mesospheric ice on meteoric smoke particles: Microphysical modeling

Meteor smoke particles (MSP), which are thought to be the nucleation germs for mesospheric ice, are currently discussed to consist of highly absorbing materials such as magnesiowüstite, hematite or magnesium–iron-silicates and may therefore be warmer than the ambient atmosphere. In order to quantify the temperature difference between MSP and the atmosphere we developed a model to calculate the MSP equilibrium temperature in radiational and collisional balance. The temperature difference between MSP and the surrounding atmosphere strongly depends on the composition of the MSP, especially on the relative iron content, where a higher iron content leads to warmer MSP. We then derive an expression of the nucleation rate of mesospheric ice particles which explicitly accounts for this temperature difference. We find that the nucleation rate is strongly reduced by several orders of magnitude if the germ temperature is increased by only a few Kelvin. Implementing this nucleation rate depending on the germ temperature into CARMA, the Community Aerosol and Radiation Model for Atmospheres, we find that fewer but larger ice particles are formed compared to a reference scenario with no temperature difference between MSP and ambient atmosphere. This may indicate that iron-rich MSP are not ideal ice nuclei and that either other MSP-types or other nucleation pathways (e.g. wave induced heterogeneous nucleation or even homogeneous nucleation) are responsible for ice formation at the mesopause.

Grasp force matching and brain iron content estimated in vivo in older women

Increased brain iron content has been linked to neural degeneration and to age-related decline of cognitive and motor functions. The basal ganglia (BG), which contain significant amount of iron, play an important role in establishing and modulating force requirements in hand grasp to meet specific task demands. However, it is unclear if increased BG iron content contributes to age differences in hand grasp performance. To investigate the relationship between BG iron content and hand grasp force matching in older (65.0 ± 8.9 years) healthy women, participants generated a 20% maximum voluntary exertion reference force that was matched with the opposite hand in the Contralateral Remembered (CR) and Contralateral Concurrent (CC) conditions and with the same hand in the Ipsilateral Remembered (IR) condition. T2* relaxation times calculated from MRI scans served to estimate iron content in the caudate nucleus (Cd), globus pallidus (GP), and putamen (Pt). Greater iron content in all BG was associated with relatively greater number of errors committed when matching force with the opposite hand in the CR and CC conditions than with the same hand in the IR condition. Younger women with greater estimated iron content committed more errors than their older counterparts with lesser estimated iron content in Cd and Pt. Greater iron content in the BG may contribute to sensorimotor declines in healthy women, and relative iron content quantified by MRI may be a promising biomarker of such.

Automated detection and characterization of SPIO‐labeled cells and capsules using magnetic field perturbations

Understanding how individual cells behave inside living systems will help enable new diagnostic tools and cellular therapies. Superparamagnetic iron oxide particles can be used to label cells and theranostic capsules for noninvasive tracking using MRI. Contrast changes from superparamagnetic iron oxide are often subtle relative to intrinsic sources of contrast, presenting a detection challenge. Here, we describe a versatile postprocessing method, called Phase map cross-correlation Detection and Quantification (PDQ), that automatically identifies localized deposits of superparamagnetic iron oxide, estimating their volume magnetic susceptibility and magnetic moment. To demonstrate applicability, PDQ was used to detect and characterize superparamagnetic iron oxide-labeled magnetocapsules implanted in porcine liver and suspended in agarose gel. PDQ was also applied to mouse brains infiltrated by MPIO-labeled macrophages following traumatic brain injury; longitudinal, in vivo studies tracked individual MPIO clusters over 3 days, and tracked clusters were corroborated in ex vivo brain scans. Additionally, we applied PDQ to rat hearts infiltrated by MPIO-labeled macrophages in a transplant model of organ rejection. PDQ magnetic measurements were signal-to-noise ratio invariant for images with signal-to-noise ratio > 11. PDQ can be used with conventional gradient-echo pulse sequences, requiring no extra scan time. The method is useful for visualizing biodistribution of cells and theranostic magnetocapsules and for measuring their relative iron content.

Structure-Phase State, Corrosion and Irradiation Properties of Zr-Nb-Fe-Sn System Alloys

Abstract In the search for more optimal core materials for a water cooled reactor at extended burnup, much attention is paid to alloys of the Zr-Nb and Zr-Nb-Fe-Sn systems. E110 and E635 alloys are two such. In the current VVER fuel cycle, the E110 alloy is used as fuel cladding and in SG components. The E635 alloy is under development as a fuel cladding and for fuel assembly structural elements for water cooled reactors of the VVER and RBMK types. E110, while having a unique corrosion resistance in pressurized water reactors, is subject to noticeable disadvantages in terms of corrosion resistance under conditions of boiling and higher coolant oxygen contents as well as in deformation stability under stresses and irradiation. Currently, the E635 alloy has passed the most important steps of qualification and is being introduced into cores as a material for guide thimbles, central tubes, and stiff frame angles in VVER-1000 FAA and FA-2. Properties of alloys are governed by their compositions and microstructure and even small changes in composition (Nb, Fe, Sn) and processing (heating in the α or the α+β regions) lead to substantial changes in properties as a result of changes in second phase precipitates and matrix composition. ATEM was used to study structure—phase states of a series of alloys Zr-(0.6–1.2) Nb-(0–0.6) Fe-(0–1.5) Sn (% weight), to determine the microstructural characteristics of recrystallized cladding tubes and the temperature stability regions of β-Nb, β-Zr, Zr(Nb,Fe)2, and (Zr,Nb)2Fe second phase precipitates. An increase in the relative content of iron R=Fe/(Fe+Nb) results in a larger volume fraction of (Zr,Nb)2 Fe precipitates. β-Nb and Zr(Nb,Fe)2 particles are completely dissolved at ⩽750°C, the (Zr,Nb)2Fe phase at ⩽800°C. Autoclave corrosion tests revealed that the corrosion resistance of the materials depends on alloy composition. The content of tin lowered down to 0.8 % reduces weight gains in water, water containing Li, and particularly in steam. The content of Nb reduced to 0.6 % results in lower weight gains in water and steam and higher weight gains in Li containing water. The optimal content of iron in Zr-Nb-Fe-Sn alloys for corrosion resistance depends on the R ratio and makes up 0.2–0.4 %. Tests of samples produced from tubes of the above alloys and irradiated in BOR-60 at 315–345°C show that alloying Zr-Nb alloys with iron and tin improves their resistance to irradiation growth and creep. Sn and a higher Fe content in solid solution effected by transfer of Fe from the Laves phase precipitates to the matrix under irradiation strengthens the alloys. The influence of irradiation on phase compositions was established using irradiated samples (gas filled and unstressed) of cladding tubes: β-Nb (85-90 % Nb) precipitates become depleted in niobium (or enriched in zirconium) to 50-60 % Nb and finely dispersed irradiation induced second particles (IIPs) enriched in niobium are formed. The Laves phase becomes depleted in iron and alters its crystal structure from hcp to bcc of the β-Nb type. The fcc (Zr,Nb)2Fe precipitates retain on the whole their composition and structure, but the peripheries of particles reveal structural features, possibly related to niobium redistribution. No amorphization of any of the precipitates was identified. Alloy composition and applied stress under irradiation influence density and distribution of dislocation loops and IIP precipitates. Proceeding from results of out-of-pile and from post-irradiation examinations of the structure and properties of E110 and E635 type cladding tubes, compositions of alloys having improved corrosion and irradiation resistances are proposed. E110 type (Zr-1Nb-0.1Fe-0.1O) alloy features enhanced strength characteristics as a result of iron transfer from Laves phase precipitates to the matrix under irradiation, lower irradiation induced growth strain, and irradiation-thermal creep. An E635 type alloy (tin and niobium content lowered down to &amp;lt;0.8 %) has a higher corrosion resistance and comparable creep and growth resistance as compared to the standard E635 alloy.

Sources and formation conditions of Early Proterozoic granitoids from the southwestern margin of the Siberian craton

Three stages of Early Proterozoic granitoid magmatism were distinguished in the southwestern margin of the Siberian craton: (1) syncollisional, including the formation of migmatites and granites in the border zone of the Tarak massif; (2) postorogenic, postcollisional, comprising numerous granitoid plutons of diverse composition; and (3) intraplate, corresponding to the development of potassic granitoids in the Podporog massif. Rocks of three petrological and geochemical types (S, I, and A) were found in the granitoid massifs. The S-type granites are characterized by the presence of aluminous minerals (garnet and cordierite), and their trace element distribution patterns and Nd isotopic parameters are similar to those of the country paragneisses and migmatites. Their formation was related to melting under varying H2O activity of aluminous and garnet—biotite gneisses at P ≥ 5 kbar and T 10 and P < 10 kbar, respectively. According to isotopic data, their formation was related to melting of a Late Archean crustal (tonalite-diorite-gneiss) source with a contribution of juvenile material ranging from 25–55% (tonalites of the Podporog massif) to 50–70% (dioritoids of the Uda pluton). The most common A-type granitoids show high relative iron content; high concentration of high-field-strength elements, Th, and light and heavy REE; and a distinct negative Eu anomaly. Their primary melts were derived at low H2O activity and T ≥ 950°C. The Nd isotopic composition of the granitoids suggests contributions to the magma formation processes from ancient (Early and Late Archean) crustal (tonalite-diorite-gneiss) sources and a juvenile mantle material. The contribution of the latter increases from 0–35% in the granites of the Podporog and Tarak massifs to 40–50% for the rocks of the Uda and Shumikha plutons. The main factors responsible for the diversity of petrological and geochemical types of granitoids in collisional environments are the existence of various fertile sources in the section of the thickened crust of the collisional orogen, variations in magma generation conditions $$(\alpha _{H_2 O} , T, and P)$$ during sequential stages of granite formation, and the varying fraction of juvenile mantle material in the source region of granitoid melts.

Iron accumulation in the striatum predicts aging-related decline in motor function in rhesus monkeys

Changes in the nigrostriatal system may be involved with the motor abnormalities seen in aging. These perturbations include alterations in dopamine (DA) release, regulation and transport in the striatum and substantia nigra, striatal atrophy and elevated iron levels in the basal ganglia. However, the relative contribution of these changes to the motor deficits seen in aging is unclear. Thus, using the rhesus monkey as a model, the present study was designed to examine several of these key alterations in the basal ganglia in order to help elucidate the mechanisms contributing to age-related motor decline. First, 32 female rhesus monkeys ranging from 4 to 32 years old were evaluated for their motor capabilities using an automated hand-retrieval task. Second, non-invasive MRI methods were used to estimate brain composition and to indirectly measure relative iron content in the striatum and substantia nigra. Third, in vivo microdialysis was used to evaluate basal and stimulus-evoked levels of DA and its metabolites in the striatum and substantia nigra of the same monkeys. Our results demonstrated significant decreases in motor performance, decreases in striatal DA release, and increases in striatal iron levels in rhesus monkeys as they age from young adulthood. A comprehensive statistical analysis relating age, motor performance, DA release, and iron content indicated that the best predictor of decreases in motor ability, above and beyond levels of performance that could be explained by age alone, was iron accumulation in the striatum. This suggests that striatal iron levels may be a biomarker of motor dysfunction in aging; and as such, can be monitored non-invasively by longitudinal brain MRI scans. The results also suggest that treatments aimed at reducing accumulation of excess iron in the striatum during normal aging may have beneficial effects on age-related deterioration of motor performance.

Melanin in human irides of different color and age of donors

Melanin is the main chromophore of the human iris. This pigment is considered to be the most important factor that determines the color of the irides. Previous studies based mainly on chemical degradation methods showed that brown irides contain more melanin than blue ones. In our study, we used electron spin resonance (ESR) spectroscopy to detect and characterize melanin free radical centers and associated iron in human irides. Based on this method, we determined the amount of melanin in the irides and the relative content of iron in iridial melanin as a function of their color, shade, and the age of their donors. Chemical degradation of iridial homogenates enabled us to characterize the structure of eumelanin and determine the content of pheomelanin present in human and bovine irides. The ESR amplitude, the normalized intensity obtained by double integration of the ESR signal of melanin, and the content of the pigment in the irides depended on color and shade of the eyes being 40% higher in the brown group of the irides compared with all other groups. On the other hand, the relative iron content normalized to the melanin content in light blue irides showed a small decrease with age of donors. Melanin in human and bovine irides was mostly composed of eumelanin, and pheomelanin content was of the order of a few percent. Although some differences in the structure of eumelanin present in the human and bovine irides are possible, the results obtained in this study suggest that human irides contain eumelanin with very similar chemical properties.

Successful Reduction of Hepatocellular Hemosiderin Content by Dietary Modification in Toco Toucans (Ramphastos toco) With Iron-Storage Disease

Abstract The purpose of this study was to determine whether a reduction in dietary iron concentration can result in significant decreases in hepatocellular hemosiderin content in toucans with iron-storage disease. We studied 2 adult toco toucans (Ramphastos toco) previously diagnosed with iron-storage disease. Liver biopsy specimens were taken before lowering dietary iron levels to <100 mg/kg on a dry-matter basis and taken again 8 months later. One bird died from airsacculitis at 12 months, and a postmortem specimen was also analyzed. Computerized image analysis of the specimens showed significant reductions (P < .001) in hepatocellular hemosiderin content over this period. Computerized image analysis is a valid means of quantifying relative iron content in serial liver biopsy specimens and can be used to monitor response to dietary iron reductions in birds with iron-storage disease. The significant relative reduction in hepatocellular iron content in these 2 toucans with iron-storage disease, in respons...

Charge Compensation Mechanism Decreases Dielectric Loss in Manganese-Doped Pb(Fe1/2Nb1/2)O3 Ceramics

Mn-doped Pb(Fe1/2Nb1/2)O3 (PFN) ceramics are synthesized by the conventional solid-state reaction method via a B-site oxide mixing route. The pure perovskite phase of Mn-doped PFN is obtained up to 0.75 mol% of manganese doping. Due to manganese doping, dielectric loss of the obtained ceramics decreases continuously up to 3 mol% of manganese, although pyrochlore phase appears. The decrease of dielectric loss can be explained by the charge compensation effect caused by the substitution of Mn4+ for Fe3+ in the octahedral cage of the perovskite structure, which is confirmed by X-ray photoelectron spectrometry (XPS). That is, due to the substitution of Mn4+ for Fe3+ ions, the relative content of iron in different valence states changes, i.e., the relative content of Fe2+ ions increases with the amount of doped manganese. Therefore, the hole-conduction mechanism caused by the partial reduction of Fe3+ to Fe2+ in the PFN system weakens, which leads to the decrease of dielectric loss. The effect of manganese doping on the depression of mechanical vibration loss also provides some contribution to the decrease of total dielectric loss through pinning down the rotation of spontaneous polarization induced by combining Mn2+ (reduced of doped Mn4+ ions during sintering) with the oxygen vacancy (produced by the compensation effect) and standing near the domain boundary. The relative dielectric constant of the Mn-doped PFN ceramics also decreases continuously with the increase of manganese content, which is believed to be related to the reduction of space-charge polarization.