Cr Se Research Articles

Crystallization behavior and structural characteristics of Cr-doped Sb70Se30 thin films for phase change memory

In this study, we prepare Cr-doped Sb70Se30 (SS) thin films via the magnetron sputtering. The influence of Cr doping on the crystallization behavior and structure characteristics of the SS thin films is systematically studied using a combination of experimental analyzes and theoretical calculations. The results reveal that compared with SS thin films, Cr-doped SS thin films exhibit higher crystallization temperature, better data retention capability, larger crystallization activation energy, and reduced resistance drift coefficient. In addition, the incorporation of Cr effectively suppresses grain growth in the SS thin films and refines the grain size. The electrical transport properties of the Cr-doped SS thin films are analyzed using a Hall system. Both X-ray photoelectron spectroscopy and first-principles calculations indicate that Cr is more prone to occupy Sb atoms and form stronger Cr–Se bonds, consequently enhancing the stability of the SS thin films. Raman spectroscopy confirms that the introduction of Cr leads to a decrease in bond length and an increase in bond energy. Moreover, the Cr-doped SS thin film exhibits minimal volume fluctuations and a smoother surface morphology, resulting in enhanced interface performance and reliability. Taken together, these results indicate that the introduction of Cr is an effective strategy for optimizing the properties and modifying the structures of SS phase-change materials.

Out‐of‐Plane Superexchange Interaction Enhanced Ferromagnetism in Semiconducting Monolayer Cr2Se3

Abstract2D magnetic semiconductors exhibit great potential for next‐generation spintronics, but realizing their full capabilities has been hindered by the low Curie temperatures (Tc) below 50 K observed in current materials. Here, a new mechanism to substantially enhance the Tc of 2D semiconducting materials through incorporating both in‐plane and out‐of‐plane superexchange interactions enabled by structural design is demonstrated. Specifically, monolayer Cr2Se3 is synthesized with a five‐layer Se–Cr–Se–Cr–Se atomic structure using molecular beam epitaxy (MBE). This unique structure not only possesses optimized in‐plane superexchange interaction but also incorporates out‐of‐plane Cr–Se–Cr couplings. Scanning tunneling spectroscopy (STS) and angular‐resolved photoemission spectroscopy (ARPES) confirm its semiconducting nature. Remarkably, the ferromagnetic phase transition observed by ARPES and Magnetic Force Microscopy (MFM) indicated that its Tc is up to 230 K. This not only establishes a new record for Tc in 2D ferromagnetic semiconductor materials but also introduces a novel approach to modulating materials' properties by manipulating the vertical dimension in 2D materials.

Enhanced ferromagnetism, magnetic anisotropy, and spin polarization in Janus CrSeTe via strain and doping

Recently, experimental 2D magnetic CrSe2 and CrTe2 inspired the study on their Janus CrSeTe, which breaks the mirror symmetry of Cr–Se(Te)–Cr. However, the CrSeTe monolayer possesses a lower Curie temperature and the in-plane magnetic anisotropy, and few works concerned both its zigzag- and stripy-antiferromagnetic states, which are crucial to determine the magnetic ground state and magnetic transition temperature. In this Letter, using first-principles calculations and Monte Carlo simulations, we systematically explore the strain, carrier-doping, and electric field effects on magnetic and electronic properties of monolayer CrSeTe. We demonstrate that monolayer CrSeTe preserves ferromagnetism in a large range of whether strain or doping. The estimated Curie temperature can be increased from 167 K to the room-temperature by the combination of 4% tensile strain and 0.1 e doping due to the enhanced ferromagnetic Cr–Se(Te)–Cr super-exchange interaction. Interestingly, either a small tensile strain (1%) or a low hole doping (0.025 h) can induce the transition of the easy axis from in-plane to out-of-plane due to the increased out-of-plane magnetic anisotropy from hybridized pz and py orbitals of Te atoms. In addition, the spin polarization is improved by over 60% by the tensile strain. Our results suggest that small strain and low carrier-doping induced room-temperature ferromagnetism, large out-of-plane magnetic anisotropy, and high spin polarization make CrSeTe useful in 2D spintronic applications and will stimulate broad studies on the regulation of magnetic and electronic properties of this class of magnetic Janus monolayers.

Toward Extremely Fast Charging through Boosting Intercalative Redox Pseudocapacitance: A SbCrSe3 Anode for Large and Fast Sodium Storage

AbstractAlloying‐type metals with high theoretical capacity are promising anode materials for sodium ion batteries, but suffer from large volume expansion and sluggish reaction kinetics. Dispersing alloying‐type metal into a buffer matrix with interfacial anionic covalent bonding is an effective method to solve the above issues. Here, this bifunctional structural unit is designed by incorporating high‐capacity Sb metal into a rigid CrSe framework for fast‐charging applications. The high‐capacity and high‐rate sodium storage can be synergistically realized in the bifunctional SbCrSe system, where the rigid CrSe framework endows the SbCrSe3 anodes with superior structural stability and improved intercalative redox pseudocapacitance. Moreover, the volume expansion of Sb during discharge can be buffered by the CrSe chain‐like matrix. The novel SbCrSe3 anode delivers a high charge capacity of 472 mAh g−1 at a current density of 0.4 C and retains ≈100% capacity at 60 C over 10 000 cycles. Further in situ and ex situ characterization reveal the multistep reaction mechanism, and the breakage and formation of reversible SbSe bonds during (dis)charge. The proposed bifunctional structural unit that combines alloying type anodes and intercalative anodes is expected to pave a new road for the development of high capacity and high rate anode materials.

A follow-up study of mucociliary clearance and trace element and mineral status in children with chronic rhinosinusitis before and three months after endoscopic sinus surgery

BackgroundThe existing data demonstrate the potential role of trace elements in nasal mucociliary clearance, although the association between trace element and mineral status and ciliary function in children with chronic rhinosinusitis is insufficiently studied. Therefore, the objective of the present study is evaluation of trace element and mineral status and mucociliary function in pediatric CRS patients before and after functional endoscopic sinus surgery. MethodsThe present study involved 30 children with chronic rhinosinusitis without nasal polyps. During this follow-up the patients were examined preoperatively (point 0), underwent functional endoscopic sinus surgery, and were repeatedly examined at three months postoperatively (point 1). At both points the patients were subjected to quality-of-life assessment using SNOT-20 questionnaire; endoscopic and computer tomography examination of the nasal sinuses; evaluation of ciliary function and mucosal cytology using high-speed videomicroscopy; assessment of blood count and inflammatory markers; as well as analysis of trace element and mineral levels in whole blood, serum, and hair using inductively-coupled plasma mass-spectrometry. ResultsThe obtained data demonstrate that endoscopic sinus surgery significantly improved sinonasal pathology in children with chronic rhinosinusitis, as evidenced by significantly reduced Lund-Mackay, Lund-Kennedy, and SNOT-20 scores. At the same time, no significant improvement of ciliary functions or mucosal cytology was observed postoperatively. Trace element status assessment demonstrated that postoperative serum Zn, whole blood Mg and Cu were significantly lower as compared to preoperative values. In contrast, serum Mn and Cr, as well as whole blood Cr and hair Se were characterized by a significant increase at three months postoperatively. Multiple linear regression analysis demonstrated that serum Zn is significantly associated with the number of ciliated cells and cell viability, whereas serum Mn and whole blood Cu concentrations are inversely associated with cell viability and ciliary length, respectively. Hair Se was found to be associated with the number of neutrophils in the mucosa biopsy. ConclusionRedistribution of trace elements and minerals may at least partially mediate prolonged recovery of mucosal ciliary function in children with chronic rhinosinusitis in three months after functional sinus surgery, although the particular mechanisms of these alterations in trace element levels are to be discovered.

Crystal structure, properties and griffiths-like phase in niobium diselenide intercalated with chromium

Polycrystalline CrxNbSe2 samples intercalated with Cr atoms up to x = 0.5 have been synthesized and studied by means of X-ray diffraction, magnetization, 53Cr NMR spectra, electrical resistivity and specific heat measurements. Within the concentration range 0 < x < 0.25, the intercalated compounds are observed to exhibit the same crystal structure as the parent compound 2H–NbSe2 and a cluster-glass-like magnetic behavior; while above x = 0.25, the Cr atoms are ordered, and starting from x = 0.33 the CrxNbSe2 compounds show a soft ferromagnetic behavior with maximal Curie temperature TC ∼82 K. According to the 53Cr NMR data, the valence state of chromium atoms is close to Cr4+. A decrease in an average magnetic moment per Cr atom in saturation observed in CrxNbSe2 with increasing x above x = 0.33 is ascribed to the possible appearance of a magnetic moment on Nb atoms due to the redistribution of the electron density between the Nb–Se and Cr–Se bonds. The deviation of the reciprocal susceptibility from the Curie-Weiss law above TC implies the presence of a Griffiths-like phase in the nominally paramagnetic state, which affects the behavior of the electrical resistivity and specific heat.

Levels and sources of hourly PM2.5-related elements during the control period of the COVID-19 pandemic at a rural site between Beijing and Tianjin

To control the spread of the novel coronavirus disease 2019 (COVID-19) in China, many anthropogenic activities were reduced and even closed on the national scale. To study the impact of this reduction and closing down, hourly concentrations of PM2.5-related elements were measured at a rural site before (12–25 January 2020), during (26 January–9 February 2020) and after (22 March–2 April 2020) the control period when all people remained socially isolated in their homes and could not return to economic zones for work. Nine major sources were identified by the positive matrix factorization model, including fireworks burning, coal combustion, vehicle emissions, dust, Cr industry, oil combustion, Se industry, Zn smelter, and iron and steel industry. Before the control period, K, Fe, Ca, Zn, Ba and Cu were the main elements, and fireworks burning, Zn smelter and vehicle emissions provided the highest contributions to the total element mass with 55%, 12.1% and 10.3%, respectively. During the control period, K, Fe, Ba, Cu and Zn were the dominating elements, and fireworks burning and vehicle emissions contributed 55% and 27% of the total element mass. After the control period, Fe, K, Ca, Zn and Ba were the main elements, and dust and iron and steel industry were responsible for 56% and 21% of the total element mass. The increased contribution from vehicle emissions during the control period could be attributed to our sampling site being near a town hospital and the fact that the vehicle activities were not restricted. The source apportionment results were also related to air mass backward trajectories. The largest reductions of dust, coal combustion, and the industrial sources (Cr industry, Zn smelter, Se industry, iron and steel industry) were distinctly seen for northwest transport (Ulanqab) and were least significant for northeast transport (Tangshan and Tianjin).

Selenium induces changes of rhizosphere bacterial characteristics and enzyme activities affecting chromium/selenium uptake by pak choi (Brassica campestris L. ssp. Chinensis Makino) in chromium contaminated soil

Understanding the chemical response and characteristics of bacterial communities in soil is critical to evaluate the effects of selenium (Se) supplement on plant growth and chromium (Cr)/Se uptake in Cr contaminated soil. The rhizosphere soil characteristics of pak choi (Brassica campestris L. ssp. Chinensis Makino) were investigated in soil contaminated with different levels and forms of Cr when supplemented with Se. Although inhibition of plant growth caused by Cr stress was not completely alleviated by Se, Cr content in plant tissues decreased in Cr(VI)120Se5 treatment (Cr(VI): 120 mg kg−1 soil; Se: 5 mg kg−1 soil) and its bioavailability in soil decreased in Cr(III)200Se5 (Cr(III): 200 mg kg−1 soil; Se: 5 mg kg−1 soil) treatment. Moreover, antagonism of Cr and Se on soil enzyme activities and bacterial communities were revealed. Notably, results of Cr(VI) reduction and Se metabolism functional profiles confirmed that bacterial communities play a critical role in regulating Cr/Se bioavailability. Additionally, the increases of Se bioavailability in Cr contaminated soil were ascribed to oxidation of Cr(VI) and reduction of Se reductases proportions, as well as the enhancing of pH in soil. These findings reveal that Se has the potential capacity to sustain the stability of microdomain in Cr contaminated soil.

Investigations of the electronic and magnetic properties of newly (001) surface LiCrS and LiCrSe half-Heusler compounds

We analyzed the electronic and magnetic properties of newly (001) surface LiCrS and LiCrSe half-Heusler compounds with the C1b structure, based on calculations of the first principles. We examine the influences of (001) surface and correlation interactions on the structural properties and electricity and magnetism of the bulk and surface (001) LiCrS and LiCrSe half-Heusler compounds with two ideal terminations named Cr–S and li–li and Cr–Se and li-term terminated (001) surfaces, respectively. We noticed that the half-metallicity assured in the bulk is kept at the Cr–S and Cr–Se terminations, with a total spin polarization equal to 100%, with a wide range in the energy gap, and the magnetic moments calculated for both terminations were found to be equal to 29 µB/f.u., which have a great scientifics in varied application. For the li–li and li-term terminations, we noticed that the half-metallicity is destroy with a total spin polarization equal to 84 and 67%, respectively, with a magnetic moment of 25.5 µB/f.u. The calculated magnetic moment of all terminations was found of all the subsurface is close to that of the bulk system and this makes these compounds of maximum benefit in the pilot applications of spintronic systems.

Influence of local structural distortions on magnetism and spin-phonon coupling of multiferroic spinel chalcogenide

The direct Cr–Cr and Cr-Se-Cr exchange interactions and the associated spin-phonon coupling are crucial for the much envisaged multiferroicity in CdCr2Se4 spinel chalcogenide. The static chemical disorder created by the Sn4+ substitution at the Cd2+ site in CdCr2Se4 affects the local crystal structure around Cr-ions, and hence its magnetism. Although the spinel structure is maintained, the trends in lattice parameters are not a linear function of increasing Sn concentration. The magnetic properties are patterned after the trend in lattice parameters but in the opposite direction. Hence, a detailed investigation into the changing local crystal structure of Cd1−xSnxCr2Se4 for (0 ≤x≤ 0.1) using EXAFS and XRD was carried out. Variation in the Cr–Se and Cr–Cr bonding is traced across the changing Sn-content. Raman spectroscopy probes the thermal excitations coupled with spin waves across the magnetic ordering temperature. The synchrotron x-ray diffraction results further complement the inference drawn from Raman studies. Our results highlight the significance of an intricate balance between spin and lattice degrees of freedom in controlling the magnetoelasticity and, hence, the spin-phonon coupling in CdCr2Se4.

Crystal structure and magnetic property correlation in [formula omitted] (M=Sb, Sn, In)

CdCr2Se4 orders magnetically below TC ∼130K. The magnetic ordering is believed to result from strong competition between the direct Cr–Cr spin couplings and the Cr–Se–Cr exchange interactions. Partial substitution of Cd2+ by small percentage of non-magnetic In, Sb, or Sn is expected to bring about local lattice distortion and changes in the electronic charge redistribution that subtly affects the Cr–Cr and Cr–Se–Cr interactions. Our results on the measurement of magnetic properties of Cd1−xMxCr2Se4 (M=Sb, Sn, In) reflects this premise. We investigate compositions with up to 10% substitution of Cd2+ with Sb, In, and Sn ions so as to maintain the Fd3m symmetry of CdCr2Se4. The x-ray diffraction analysis using Rietveld refinement technique confirms the symmetry of the lattice and provide the various lattice parameters. Measurement of magnetic properties indicates change in the ordering temperatures and total magnetic moment. Formation of multiple Cr valence in the substituted compositions and changing lattice constant seem to effect the magnetic properties. Certain features in magnetic properties hint towards low-spin transition of Cr2+.

Relationship between weight, age and hatching success and the concentration of heavy metals in nestling blue macaw (Anodorhynchus hyacinthinus Latham, 1790) in the Pantanal,Mato Grosso do Sul

Abstract: The concentration of heavy metals (Cr, Fe, Al, As, Cd, Cu, Pb, Mo, Ni, Se and Zn) was evaluated in the blood of nestling blue macaws (Anodorhynchus hyacinthinus) captured in the Pantanal, Mato Grosso do Sul (n=26) in 2012; this was based on the hypothesis that these birds exhibit levels of these heavy metals in their organism and that these interfere in hatching success, weight and age of the chicks. Blood samples were digested with nitric acid and hydrochloric acid and the quantification of metals was performed by ICP-OES (Optical Emission Spectroscopy and Inductively Coupled Plasma). Blood samples of nestlings showed concentrations of Cr (0.10μg/g) Fe (3.06μg/g) Al (3.46μg/g), Cd (0.25μg/g) Cu (0.74μg/g), Mo (0.33μg/g), Ni (0.61μg/g), Se (0.98μg/g), and Zn (2.08μg/g). The levels of heavy metals found were not associated with weight, age and hatching success of the chicks.

Enhancing magnetic ordering in Cr-doped Bi2Se3 using high-TC ferrimagnetic insulator.

We report a study of enhancing the magnetic ordering in a model magnetically doped topological insulator (TI), Bi(2-x)Cr(x)Se(3), via the proximity effect using a high-TC ferrimagnetic insulator Y(3)Fe(5)O(12). The FMI provides the TI with a source of exchange interaction yet without removing the nontrivial surface state. By performing the elemental specific X-ray magnetic circular dichroism (XMCD) measurements, we have unequivocally observed an enhanced TC of 50 K in this magnetically doped TI/FMI heterostructure. We have also found a larger (6.6 nm at 30 K) but faster decreasing (by 80% from 30 to 50 K) penetration depth compared to that of diluted ferromagnetic semiconductors (DMSs), which could indicate a novel mechanism for the interaction between FMIs and the nontrivial TIs surface.

Surface half-metallicity and stability of zinc-blende CrSe: A comprehensive first-principles study

By means of the first-principles calculations, we explore comprehensively the structural, electronic, and magnetic properties of the (001) and (110) surfaces of half-metallic zinc-blende CrSe. It is found that all the surfaces of (110) and Cr- and Se-terminated (001) preserve the bulk half-metallicity of zinc-blende CrSe. The atomic magnetic moments at the (001) surface are increased greatly compared to those in the bulk due to the break of Cr–Se bond at the (001) surface, but the changes are very slight for the case of the (110) surface due to the keep of Cr–Se bond at the (110) surface. We also show for the first time from the calculated surface energy that the Se-terminated (001) surface is energetically more stable than the (110) surface and the Cr-terminated (001) surface. The present work would be useful for the realization of half-metallic zinc-blende CrSe thin films or multilayers.

Effects of competing magnetic interactions on the electronic transport properties of CuCrSe2

We have synthesized single-phase samples of the CuCrSe2 phase that exhibits hexagonal-rhombohedral layered crystal structure with space group R3m. Here we present a detailed study of electronic transport and magnetic properties of CuCrSe2. We moreover investigate the heat capacity of CuCrSe2 in comparison to that of CuCrS2. The electrical resistivity of CuCrSe2 shows metallic-like behavior down to 2K, while the thermoelectric power is large around 100μVK−1 at 300K. A weak anomaly in resistivity and a rounded maximum in magnetic susceptibility are observed around 55K. No sharp transition at 55K is observed in the heat capacity of CuCrSe2, rather a visible maximum is seen. At low temperatures from 2 to 14K, the magnetic heat capacity follows T2-dependence. We tentatively believe this behavior of CuCrSe2 to be due to competing magnetic interactions between intralayer Cr atoms. The ferromagnetic Cr–Se–Cr indirect exchange among intralayer Cr atoms is enhanced in the selenide compound (that is more metallic than the sulfide compound), and competes with the antiferromagnetic Cr–Cr direct interactions. The interlayer antiferromagnetic exchange through Cu atoms leads to magnetic ordering at low temperature at TN=55K.

Structural and magnetic properties of CuCr 2Se 4 single crystals diluted with Sb(III)

A series of single crystals based on CuCr 2Se 4 spinel diluted with Sb ions was prepared by chemical vapour transport. They were characterized by X-ray fluorescent spectroscopy (XRF), X-ray diffraction, X-ray photoelectron spectroscopy (XPS) and bulk magnetization measurements. The results revealed that nonmagnetic Sb 3+ ions substitute Cr 3+ ions at the octahedral sites. For the Sb 3+ content x = 0.06 the single crystals of (Cu)[Cr 2− x Sb x ]Se 4 were formed, while for larger Sb concentration ( x = 0.12 and x = 0.16) the crystals with cation vacancies at the octahedral sites were obtained. The XPS data evidenced the 3 d 3 electronic configuration of Cr ions with localized magnetic moments for the three compositions differing in the Sb content. Despite the unaltered valence state of Cr ions along the series, the low-temperature magnetic characteristics have changed considerably. With increasing content of Sb the saturation magnetic moment was found to radically decrease. This effect may be explained in terms of the perturbation in the ferromagnetic Cr–Se–Cr indirect exchange interactions caused by the presence of increasing number of dopant atoms and vacancies in the crystal lattice.

Nondestructive analysis of single crystals of selenide spinels by X-ray spectrometry techniques

The paper presents possibilities and difficulties in nondestructive analysis of small multielement single crystals performed by means of X-ray spectrometry techniques: micro-X-ray fluorescence spectrometry (μ-XRF), energy-dispersive electron probe microanalysis (ED-EPMA), and X-ray photoelectron spectroscopy (XPS). The capability of the X-ray spectroscopy techniques in elemental analysis is demonstrated with the single crystals of selenide spinels of the general formula MxNyCrzSe4 (M+2 and N+3 are, for example, Zn+2, V+3, Ga+3, Cd+2, In+3, and Sb+3). The results of the nondestructive analyses (μ-XRF, ED-EPMA, and XPS) are compared with those obtained by inductively coupled plasma optical emission spectrometry (ICP-OES) and wavelength-dispersive X-ray spectrometry (WDXRF) following sample digestion. The present study shows satisfactory agreement between the results of μ-XRF analysis performed using the standardless fundamental parameter method and the results obtained with the WDXRF and ICP-OES analyses. If the measured single crystal is precisely positioned, the difference between μ-XRF and wet analysis (WDXRF and ICP-OES) does not exceed 5% rel. The reliable results of ED-EPMA can be obtained only if the measured area is sufficiently large, i.e., of 200 × 300 μm. Even if this condition is fulfilled, the relative difference between the ED-EPMA and the wet analysis may reach 10% rel. In case of the XPS analysis, the accuracy of results depends on the proper preparation of the sample surface. It should be free of contamination that can be obtained by scraping in situ in ultrahigh vacuum. The ion etching, commonly used for cleaning the surface, leads to preferential sputtering; therefore, the reliable results cannot be obtained. FigureThe paper presents possibilities and difficulties in nondestructive analysis of small multielement single crystals performed by means of X-ray spectrometry techniques: micro-XRF, ED-EPMA and XPS.

Vancomycin dosing assessment in intensive care unit patients based on a population pharmacokinetic/pharmacodynamic simulation.

WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT * Despite the frequent use of vancomycin in intensive care unit (ICU) patients, few studies aimed at characterizing vancomycin population pharmacokinetics have been performed in this critical population. * Population pharmacokinetics coupled with pharmacodynamic analysis, in order to optimize drug exposure and hence antibacterial effectiveness, has been little applied in these specific patients. WHAT THIS STUDY ADDS * Our population model characterized the pharmacokinetic profile of vancomycin in adult ICU patients, higher distribution volume values (V) being observed when the patient's serum creatinine (Cr(Se)) was greater than 1 mg dl(-1). * Age and creatinine clearance (CL(cr)) were identified as the main covariates explaining the pharmacokinetic variability in vancomycin CL. * Our pharmacokinetic/pharmacodynamic (PK/PD) simulation should aid clinicians to select initial vancomycin doses that will maximize the rate of response in the ICU setting, taking into account the patient's age and renal function as well as the susceptibility of Staphylococcus aureus. AIM To estimate the vancomycin pharmacokinetic profile in adult ICU patients and to assess vancomycin dosages for increasing the likelihood of optimal exposure. METHODS Five hundred and sixty-nine concentration-time data from 191 patients were analysed using a population pharmacokinetic approach (NONMEN). External model evaluation was made in 46 additional patients. The 24 h area under the concentration-time curve (AUC(0,24 h)) was derived from the final model. Minimum inhibitory concentration (MIC) values for S. aureus were obtained from the EUCAST database. AUC(0,24 h) : MIC >/= 400 was considered as PK/PD efficacy index. The probability of different dosages attaining the target considering different strains of S. aureus and patient subgroups was estimated with Monte Carlo simulation. RESULTS Vancomycin CL showed a significant dependence on patient age and renal function whereas Cr(Se) > 1 mg dl(-1) increased V more than twofold. For our representative ICU patient, 61 years, 73 kg, Cr(Se)= 1.4 mg dl(-1), measured CL(Cr)= 74.7 ml min(-1), the estimated values were CL = 1.06 ml min(-1) kg(-1) and V= 2.04 l kg(-1). The cumulative fraction of response for a standard vancomycin dose (2 g day(-1)) was less than 25% for VISA strains, and 33% to 95% for susceptible S. aureus, depending on patient characteristics. CONCLUSIONS Simulations provide useful information regarding the initial assessment of vancomycin dosing, the conventional dosing regimen probably being suboptimal in adult ICU patients. A graphic approach provides the recommended dose for any selected probability of attaining the PK/PD efficacy target or to evaluate the cumulative fraction of response for any dosing regimen in this population.

Investigation of polarographic interference between Se(IV) and Cr(VI), its elimination and application to Gerede river water

Trace chromium(VI) determination plays an important role since it is carcinogenic agent and toxic pollutant. For this purpose a direct method is developed using differential pulse polarography, DPP. When selenite was added into solutions of some ions such as copper(II), lead(II), cadmium(II), zinc(II), and chromium(VI) their DP polarographic peak decreased. This kind of interference will cause large errors in the determinations, its elimination is very important. The interference between selenite and Cr(VI) ions could be eliminated in B-R (Britton-Robbinson) buffer at pH 8.5. In this work the effect of components present in buffer has been investigated and it was found that phosphate and borate eliminated the formation of Cr–Se intermetallic compound formation. While it was possible to determine 1 × 10 −5 M Cr(VI) in the presence of 100 times more selenite as (1.0 ± 0.1) × 10 −5 M, in borate medium, it was possible to determine (1.0 ± 0.05) × 10 −5 M in phosphate medium. In the presence of selenite detection limit ( S/ N = 3) was 9.0 × 10 −8 M Cr(VI) by using either phosphate or borate This method was applied to Gerede river water, after oxidation all Cr(III) present into Cr(VI).

Tuning the Magnetic Properties of LixCrTi0.25Se2 (0.03≤x≤0.7) by Directed Deintercalation of Lithium

X-ray diffraction (XRD), in situ energy-dispersive X-ray diffraction (EDXRD), X-ray absorption near-edge structure (XANES), extended X-ray absorption fine structure (EXAFS), and magnetic measurements were applied to investigate the effects of lithium deintercalation on pseudolayered Li(0.70)CrTi(0.25)Se(2). A detailed picture of structural changes during the deintercalation process was obtained by combining the results of EDXRD and EXAFS. Removal of Li from the host-guest complex leads to anisotropic contraction of the unit cell with stronger impact on the c axis, which is the stacking axis of the layers. The EDXRD experiments evidence that the shrinkage of the lattice parameters with decreasing x(Li) in Li(x)CrTi(0.25)Se(2) is nonlinear in the beginning and then becomes linear. Analysis of the EXAFS spectra clearly shows that the Cr/Ti-Se distances are affected in a different manner by Li removal. The Cr-Se bond lengths decrease, whereas the Ti-Se bonds lengthen when the Li content is reduced, which is consistent with XRD data. Magnetic measurements reveal a change from predominantly antiferromagnetic exchange (theta(p) = -300 K) interactions for the pristine material to ferromagnetic exchange interactions (theta = 25 K) for the fully intercalated material. Thus, the magnetic properties can be altered under ambient conditions by directed adjustment of the dominant magnetic exchange. The unusual magnetic behavior can be explained on the basis of the variation of the metal-metal distances and the Cr-Se-Cr angles with x, which were determined by Rietveld refinements. Owing to competing ferromagnetic and antiferromagnetic exchange interactions and disorder, the magnetic ground state of the intercalated materials is characterized by spin-glass or spin-glass-like behavior.