Control over connectivity and magnetism of tetrahedral FeSe2 chains through coordination Fe–amine complexes

Magnetic interactions in compounds containing tetrahedral _∞¹(FeSe₂) chains separated by Fe–amine complexes are controlled by the denticity of the amine.

High-Temperature Magnetism as a Probe for Structural and Compositional Uniformity in Ligand-Capped Magnetite Nanoparticles

To investigate magnetostructural relationships in colloidal magnetite (Fe₃O₄) nanoparticles (NPs) at high temperature (300-900 K), we measured the temperature dependence of magnetization (M) of oleate-capped magnetite NPs ca. 20 nm in size. Magnetometry revealed an unusual irreversible high-temperature dependence of M for these NPs, with dip and loop features observed during heating-cooling cycles. Detailed characterizations of as-synthesized and annealed Fe₃O₄ NPs as well as reference ligand-free Fe₃O₄ NPs indicate that both types of features in M(T) are related to thermal decomposition of the capping ligands. The ligand decomposition upon the initial heating induces a reduction of Fe³⁺ to Fe²⁺ and the associated dip in M, leading to more structurally and compositionally uniform magnetite NPs. Having lost the protective ligands, the NPs continually sinter during subsequent heating cycles, resulting in divergent M curves featuring loops. The increase in M with sintering proceeds not only through elimination of a magnetically dead layer on the particle surface, as a result of a decrease in specific surface area with increasing size, but also through an uncommonly invoked effect resulting from a significant change in Fe³⁺/Fe²⁺ ratio with heat treatment. The interpretation of irreversible features in M(T) indicates that reversible M(T) behavior, conversely, can be expected only for ligand-free, structurally and compositionally uniform magnetite NPs, suggesting a general applicability of high-temperature M(T) measurements as an analytical method for probing the structure and composition of magnetic nanomaterials.

Use of ductoscopy as an additional diagnostic method and its applications in nipple discharge

AIM

About 1/10 of the patients apply to breast clinics with the complaint of nipple discharge (ND). Surgery is the most frequently preferred treatment method in case of suspicious ND. The contribution of ductoscopy to identify the patients who are candidates for surgery was evaluated and its role to limit the surgery was assessed.

METHODS

From November 2005 to December 2010 430 patients with ND were assessed by 456 ductoscopic investigations and the results were analyzed. Complete ductoscopic evaluation was achieved in 84% of cases and 28 patients were offered surgery but did not accept (N.=355). Patients with bloody or serous discharges from a single duct were investigated by ductoscopy under local anesthesia as an office procedure. The patients were grouped according to discharge characteristics and the ductoscopic diagnoses.

RESULTS

A total of 223 patients had all three criteria of pathologic ND (PND: single duct, spontaneous and bloody/serous discharge). Twenty-two potential neoplastic or malignant lesion (PNML) and 79 papillomatous lesion (solitary or multiple papilloma) were identified. In 132 patients with just two of the PND criteria, 5 PNML and 18 papillomatous lesions were identified. Twenty-three patients with solitary papilloma that were removed by ductoscopic papillomectomy (DP) are followed up without surgery.

CONCLUSION

Ductoscopy helped to identify the patients who required surgical treatment and decreased the number of operations. DP was successfully performed in select group of patients who otherwise would have required surgical resection. Patients with normal ductoscopy findings and patients who were treated with DP successfully can be followed up without the need of surgery.

NH4FeCl2(HCOO): synthesis, structure, and magnetism of a novel low-dimensional magnetic material

Solvothermal synthesis was used to create a low-dimensional iron(II) chloride formate compound, NH4FeCl2(HCOO), that exhibits interesting magnetic properties. NH4FeCl2(HCOO) crystallizes in the monoclinic space group C2/c (No. 15) with a = 7.888(1) Å, b = 11.156(2) Å, c = 6.920(2) Å, and β = 108.066(2)°. The crystal structure consists of infinite zigzag chains of distorted Fe(2+)-centered octahedra linked by μ2-Cl and syn-syn formate bridges, with interchain hydrogen bonding through NH4(+) cations holding the chains together. The unique Fe(2+) site is coordinated by four equatorial chlorides at a distance of 2.50 Å and two axial oxygens at a distance of 2.08 Å. Magnetic measurements performed on powder and oriented single-crystal samples show complex anisotropic magnetic behavior dominated by antiferromagnetic interactions (TN = 6 K) with a small ferromagnetic component in the direction of chain propagation. An anisotropic metamagnetic transition was observed in the ordered state at 2 K in an applied magnetic field of 0.85-3 T. (57)Fe Mössbauer spectroscopy reveals mixed hyperfine interactions below the ordering temperature, with strong electric field gradients and complex noncollinear arrangement of the magnetic moments.

Oxidation states and quality of upper interfaces in magnetic tunnel junctions: oxygen effect on crystallization of interfaces

In this study, we have deposited an 57Fe sensor layer at the upper interface, i.e. the interface between the oxide barrier and the upper electrode in selected magnetic tunnel junctions (MTJs), in order to perform nuclear resonant scattering with the aim of obtaining direct information on the magnetic properties and quality of this interface. This is a unique approach as it makes use of this powerful technique to give information at the atomic level, and specifically from the interface where the sensor layer is deposited. By varying sample tunnel barrier thicknesses and oxidation times in the preparation of this barrier, we have observed that longer oxidation time results in not only an increase of the magnetic hyperfine fields, but also causes an interesting crystallization and smoothing of the interface. We also observed that boron atoms diffuse away from the lower part of the upper FeCoB electrode toward the capping layer. An important observation, which has a crucial effect in tunnel magnetoresistance values, is the absence of any magnetically dead FeO layer at the interface. Another finding is that the deposition of Fe on MgO is much smoother than the deposition of MgO on Fe.

Frequency of Celiac Disease in Children with Beta Thalassemia major

BACKGROUND

We aimed to investigate the frequency of celiac disease in children with β-thalassemia major (B-TM) in Shiraz, southern Iran.

MATERIALS AND METHODS

In this study, the prevalence of celiac disease in children with B-TM was evaluated. Children with B-TM were screened for celiac disease by ant-tissue transglutaminase (anti-tTG) IgA antibody, IgA level and anti-tTG IgG. A total of 1500 school healthy children in Shiraz with age/sex matched were selected as control group.

RESULTS

A total of 215 B-TM patients with mean age of 12.7 ± 4.4 years, were included into the study (52.1% was male). None of the patients were positive for anti-tTG IgA. Eight cases were IgA deficient in whom anti-tTG IgG was investigated but none of them were positive for anti-tTG IgG. The finding in control group has a seroprevalence of 2% and biopsy proven disease of 0.6%.

CONCLUSION

Many patients with thalassemia major have multiple non specific symptom that are not justifiable with underlying disease and might be due to atypical celiac disease. We didn't find any case of celiac disease among more than 200 children with β-thalassemia major in Shiraz, southern Iran. So it seems reasonable to screen only those who have features, even not classical, of celiac disease.

Chemical excision of tetrahedral FeSe(2) chains from the superconductor FeSe: synthesis, crystal structure, and magnetism of Fe(3)Se(4)(en)(2)

Fragments of the superconducting FeSe layer, FeSe2 tetrahedral chains, were stabilized in the crystal structure of a new mixed-valent compound Fe3Se4(en)2 (en = ethylenediamine) synthesized from elemental Fe and Se. The FeSe2 chains are separated from each other by means of Fe(en)2 linkers. Mössbauer spectroscopy and magnetometry reveal strong magnetic interactions within the FeSe2 chains which result in antiferromagnetic ordering below 170 K. According to DFT calculations, anisotropic transport and magnetic properties are expected for Fe3Se4(en)2. This compound offers a unique way to manipulate the properties of the Fe-Se infinite fragments by varying the topology and charge of the Fe-amino linkers.

Oxidation states and the quality of lower interfaces in magnetic tunnel junctions: oxygen effect on crystallization of interfaces

Lower interfaces in magnetic tunnel junctions (MTJs), which are the basic components in many spintronic devices such as magnetoresistive random access memories, have crucial effects on the performance of these devices. To obtain more insight into such interfaces, we have introduced an ultrathin sensor layer of (57)Fe at the interface between the lower electrode and the oxide barrier in selected MTJs. This allowed us to perform nuclear resonant scattering measurements, which provide direct information on the magnetic properties and quality of the interfaces. The application of nuclear resonant scattering to study interfaces in MTJs is a unique approach in the sense that it gives information at the atomic level, and specifically from the interface where the sensor layer is deposited. Samples with different tunnel barrier thicknesses and varied oxidation times in the preparation of this barrier have been studied. These show that oxidation can not only increase the magnetic hyperfine fields but also cause an interesting smoothing and crystallizing of the interface. Another interesting finding is the observation of boron diffusion into the lower part of the FeCoB lower electrode towards the Ta seed layer.

Characterization of [4Fe-4S] cluster vibrations and structure in nitrogenase Fe protein at three oxidation levels via combined NRVS, EXAFS, and DFT analyses

Azotobacter vinelandii nitrogenase Fe protein (Av2) provides a rare opportunity to investigate a [4Fe-4S] cluster at three oxidation levels in the same protein environment. Here, we report the structural and vibrational changes of this cluster upon reduction using a combination of NRVS and EXAFS spectroscopies and DFT calculations. Key to this work is the synergy between these three techniques as each generates highly complementary information and their analytical methodologies are interdependent. Importantly, the spectroscopic samples contained no glassing agents. NRVS and DFT reveal a systematic 10-30 cm(-1) decrease in Fe-S stretching frequencies with each added electron. The "oxidized" [4Fe-4S](2+) state spectrum is consistent with and extends previous resonance Raman spectra. For the "reduced" [4Fe-4S](1+) state in Fe protein, and for any "all-ferrous" [4Fe-4S](0) cluster, these NRVS spectra are the first available vibrational data. NRVS simulations also allow estimation of the vibrational disorder for Fe-S and Fe-Fe distances, constraining the EXAFS analysis and allowing structural disorder to be estimated. For oxidized Av2, EXAFS and DFT indicate nearly equal Fe-Fe distances, while addition of one electron decreases the cluster symmetry. However, addition of the second electron to form the all-ferrous state induces significant structural change. EXAFS data recorded to k = 21 Å(-1) indicates a 1:1 ratio of Fe-Fe interactions at 2.56 Å and 2.75 Å, a result consistent with DFT. Broken symmetry (BS) DFT rationalizes the interplay between redox state and the Fe-S and Fe-Fe distances as predominantly spin-dependent behavior inherent to the [4Fe-4S] cluster and perturbed by the Av2 protein environment.

Observation of the Fe-CN and Fe-CO vibrations in the active site of [NiFe] hydrogenase by nuclear resonance vibrational spectroscopy

Nuclear inelastic scattering of (57)Fe labeled [NiFe] hydrogenase is shown to give information on different states of the enzyme. It was thus possible to detect and assign Fe-CO and Fe-CN bending and stretching vibrations of the active site outside the spectral range of the Fe-S cluster normal modes.

Development of iron-doped silicon nanoparticles as bimodal imaging agents

We demonstrate the synthesis of water-soluble allylamine-terminated Fe-doped Si (Si(xFe)) nanoparticles as bimodal agents for optical and magnetic imaging. The preparation involves the synthesis of a single-source iron-containing precursor, Na(4)Si(4) with x% Fe (x = 1, 5, 10), and its subsequent reaction with NH(4)Br to produce hydrogen-terminated Si(xFe) nanoparticles. The hydrogen-capped nanoparticles are further terminated with allylamine via thermal hydrosilylation. Transmission electron microscopy indicates that the average particle diameter is ∼3.0 ± 1.0 nm. The Si(5Fe) nanoparticles show strong photoluminescence quantum yield in water (∼10%) with significant T(2) contrast (r(2)/r(1) value of 4.31). Electron paramagnetic resonance and Mössbauer spectroscopies indicate that iron in the nanoparticles is in the +3 oxidation state. Analysis of cytotoxicity using the resazurin assay on HepG2 liver cells indicates that the particles have minimal toxicity.

A randomized, placebo controlled study: EMLA in minor breast surgery

AIM

Patients undergoing excision for breast lumps prefer general anesthesia or local anesthesia plus sedation, because of the fear of pain for local anesthesia alone. The aim of this study is to show the efficacy of an eutectic mixture of local anesthetic lignocaine and prilocaine (EMLA®) in these patients.

METHODS

This study has been designed randomized, placebo-controlled. Forty five patients undergoing excision for breast lumps were divided into three groups. The first group was administered local EMLA cream preoperatively (Group I, N.=15), the second group (Group II, N.=15) had no preoperative preparation and the third group was placebo group (Group III, N.=15). All groups underwent the operation under local anesthesia. Pain during the local anesthesia and three hours after the operation were assessed using the visual analog scale. The amount of local anesthetic used during the operation and the anesthetic need of patients after the operation were assessed.

RESULTS

When the three groups were compared, it was found that the intensity of pain in the group with EMLA was considerably lower during and after the operation (P<0.05). The amount of local anesthetic used during the operation was lower (P<0.05) and the need for post-operative analgesic was also less than the usual (P<0.05).

CONCLUSION

Topical EMLA use decreases the pain, provides per-operative and postoperative patient and physician comfort, improved patient's compliance, and simplifies the surgical procedure. This is the first study demonstrating that a topical anesthetic provides a non-invasive analgesia during benign breast mass excision.

Real sample temperature: a critical issue in the experiments of nuclear resonant vibrational spectroscopy on biological samples

There are several practical and intertangled issues which make the experiments of nuclear resonant vibrational spectroscopy (NRVS) on biological samples difficult to perform. The sample temperature is one of the most important issues. In NRVS the real sample temperatures can be very different from the readings on the temperature sensors. In this study the following have been performed: (i) citing and analyzing various existing NRVS data to assess the real sample temperatures during the NRVS measurements and to understand their trends with the samples' loading conditions; (ii) designing several NRVS measurements with (Et(4)N)[FeCl(4)] to verify these trends; and (iii) proposing a new sample-loading procedure to achieve significantly lower real sample temperatures and to balance among the intertangled experimental issues in biological NRVS measurements.

Shape induced symmetry in self-assembled mesocrystals of iron oxide nanocubes

Grazing incidence small-angle scattering and electron microscopy have been used to show for the first time that nonspherical nanoparticles can assemble into highly ordered body-centered tetragonal mesocrystals. Energy models accounting for the directionality and magnitude of the van der Waals and dipolar interactions as a function of the degree of truncation of the nanocubes illustrated the importance of the directional dipolar forces for the formation of the initial nanocube clusters and the dominance of the van der Waals multibody interactions in the dense packed arrays.