Electrospun magnetic carbon composite fibers: Synthesis and electromagnetic wave absorption characteristics

Electrospun polyacrylonitrile (PAN)‐based carbon composite fibers embedded with magnetic nanoparticles have been developed as materials for electromagnetic wave absorption. The nanocomposite fibers were prepared by electrospinning from a dispersion of magnetite (Fe₃O₄) nanoparticles stabilized by L ‐glutamic acid in a solution of PAN and N, N‐dimethyl formamide. The Fe₃O₄‐embedded PAN nanofibers were stabilized at 270°C in air and carbonized at 800°C in nitrogen. The Fe₃O₄ nanoparticles were crystalline with a particle size of about 7 nm, most of which was reduced to Fe₃C with agglomerates of up to 50 nm diameter in the carbon fibers. The carbon morphology was mostly disordered, but exhibited a layered graphitic structure in the vicinity of the nanoparticles. The carbon composite fiber exhibited ferromagnetic behavior, and the induced magnetic saturation per unit mass of fibers increased with increasing Fe₃O₄ content in the precursor. The complex relative dielectric permittivity was tuned by adjusting the amount of Fe₃O₄ in the carbon fiber precursor. With increasing Fe₃O₄ content, good electromagnetic wave absorption characteristics were observed below 6 GHz, even for samples with fiber loadings as low as 5 wt %. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Functionalized nanoporous silica for the removal of heavy metals from biological systems: adsorption and application

Surface-functionalized nanoporous silica, often referred to as self-assembled monolayers on mesoporous supports (SAMMS), has previously demonstrated the ability to serve as very effective heavy metal sorbents in a range of aquatic and environmental systems, suggesting that they may be advantageously utilized for biomedical applications such as chelation therapy. Herein we evaluate surface chemistries for heavy metal capture from biological fluids, various facets of the materials' biocompatibility, and the suitability of these materials as potential therapeutics. Of the materials tested, thiol-functionalized SAMMS proved most capable of removing selected heavy metals from biological solutions (i.e., blood, urine, etc.) Consequentially, thiol-functionalized SAMMS was further analyzed to assess the material's performance under a number of different biologically relevant conditions (i.e., variable pH and ionic strength) to gauge any potentially negative effects resulting from interaction with the sorbent, such as cellular toxicity or the removal of essential minerals. Additionally, cellular uptake studies demonstrated no cell membrane permeation by the silica-based materials generally highlighting their ability to remain cellularly inert and thus nontoxic. The results show that organic ligand functionalized nanoporous silica could be a valuable material for a range of detoxification therapies and potentially other biomedical applications.     

Monitoring hydrogenation in the margarine industry by low resolution pulsed NMR

An N M R method has been developed to monitor the hydrogenation of various oils used as raw materials in the margarine industry. The method is based on the determination of a monoexponential approximation of the longitudinal relaxation time, T1, which is shown to be highly correlated with the iodine number.     

Oral manifestations of severe short-limb dwarfism resembling Grebe chondrodysplasia: report of a case

The oral and dental abnormalities associated with a distinct variety of severe short-limb dwarfism are described. The patient, a 9-year-old Arab boy, had delayed development and eruption of teeth, severe oligodontia of permanent dentition, hypodontia, microdontia, supplemental incisor, enamel hypoplasia of primary teeth, doubled and abnormal frenal attachments, bifid uvula, hypoplastic maxilla, and malocclusion. Clinical and radiographic examinations revealed asymmetric dysplasia and anaplasia of long bones, craniofacial dysmorphia, prominent forehead, budlike fingers and bulbous toes, dysplastic nails, severe hearing loss, and reduced joint mobility. These features resemble, in general, those characteristic of Grebe chondrodysplasia, an extremely rare ill-defined syndrome that is inherited as an autosomal-recessive disorder.     

Polymorphism of the angiotensin I converting enzyme gene in essential hypertensive patients

In order to study the relationship between plasma and platelet von Willebrand factor (vWF), we used an experimental model of crossed bone marrow transplantation (BMT) between SLA immunocompatible normal and homozygous von Willebrand (vWD) pigs. A normal pig received bone marrow from a vWD pig and a second pig with vWD was engrafted with marrow from a normal pig. Each recipient, after total irradiation of 10 Grays, received by a central catheter 10(10) monocellular bone marrow cells without immunosuppression. The animals were followed for 50 d and no graft rejection or graft-versus-host disease was observed. After aplasia occurring 3 weeks after BMT, white blood cells and platelets returned to normal. Before transplantation, in the vWD pig, vWFAg and vWF activity were not detected in plasma and in platelet and megakaryocyte alpha-granules. After transplantation with normal marrow, platelet vWFAg and platelet vWF activity wer normal and high molecular weight multimers and numerous tubular structures were present in alpha-granules. Before transplantation, the normal pig had normal plasma and platelet vWFAg-vWF activity, normal multimeric pattern, and the platelet and megakaryocyte alpha-granules displayed many tubular structures, eccentrically located in one of their poles, coinciding with immunogold staining vWFAg. After transplantation with homozygous vWD marrow, platelet and megakaryocyte alpha-granules lacked tubular structures. Alpha-granule immunogold staining for vWF was consistently negative, although plasma vWF was at a normal level. In conclusion, this study shows that, unlike other plasma proteins such as fibrinogen. vWF endocytosis does not occur from plasma to the platelet alpha-granules. Platelet and megakaryocyte vWF solely originates from megakaryocyte endogenous synthesis and is independent of plasma vWF.     

Clinical quiz. Differential diagnosis of a patient with Wegener''s granulomatosis

STUDY OBJECTIVE: To describe a case series of emergency medical technician-basic (EMT-B)-administered epinephrine for anaphylaxis in a wilderness setting. DESIGN: Case series of patients in anaphylaxis who received epinephrine subcutaneously from EMT-Bs. SETTING: National park rural/wilderness emergency medical service system covering 863,000 acres and serving approximately 2 million annual visitors. PARTICIPANTS: Prehospital care providers were National Park Service rangers with EMT-B training. Patients in the series were visitors to Sequoia and Kings Canyon National Parks with anaphylaxis resulting from insect stings. INTERVENTION: Subcutaneous administration of epinephrine by EMT-Bs trained in recognition, understanding, and treatment of anaphylaxis. RESULTS: Eight patients with anaphylaxis resulting from Hymenoptera stings, from June 1992 through September 1993, received EMT-B-administered epinephrine. All patients improved clinically after treatment with epinephrine within 25 minutes. No major side effects occurred. CONCLUSION: Our data suggest that EMT-B-administered epinephrine is safe when used by EMT-Bs in the rural/wilderness setting, with appropriate physician supervision. Further study in large trials will be required to demonstrate safety and efficacy.     

Phenylselenenyl- and phenylthio-substituted pyrimidines as inhibitors of dihydrouracil dehydrogenase and uridine phosphorylase

Lithiation of 5-bromo-2,4-bis(benzyloxy)pyrimidine (3) with n-BuLi at -80 degrees C followed by the addition of diphenyl diselenide or diphenyl disulfide as an electrophile furnished the corresponding 5-(phenylhetera)-2,4-bis(benzyloxy)pyrimidine, which on exposure to trimethylsilyl iodide in CH2-Cl2 at room temperature yielded the 5-(phenylhetera)uracils in 70-75% yield. Similarly, the 6-(phenylhetera)uracils were prepared from 6-bromo-2,4-bis(benzyloxy)pyrimidine (10). 1-[(2-Hydroxyethoxy)methyl]-5-(phenylselenenyl)uracil (PSAU, 18) and 1-(ethoxymethyl)-5-(phenylselenenyl)uracil (17) were synthesized by the electrophilic addition of benzeneselenenyl chloride to the acyclic uracils under basic conditions. These compounds were evaluated for their ability to inhibit dihydrouracil dehydrogenase (DHUDase, E.C. 1.3.1.2), orotate phosphoribosyltransferase (OPRTase, E.C. 2.4.2.10), uridine phosphorylase (UrdPase, E.C. 2.4.2.3), and thymidine phosphorylase (dThdPase, E.C. 2.4.2.4). 5-(Phenylselenenyl)uracil (PSU, 6) and 5-(phenylthio)uracil (PTU, 7) inhibited DHUDase with apparent K(i) values of 4.8 and 5.4 microM, respectively. The corresponding 6-analogues, compounds 13 and 14, demonstrated inhibitory activity against OPRTase. PTU as well as PSU and its riboside, 2'-deoxyriboside, and acyclonucleosides were inhibitors of UrdPase, with PSAU (18) being the most potent with an apparent K(i) value of 3.8 microM. None of the compounds evaluated had any effect on dThdPase. Interestingly, most of the compounds showed modest selective anti-human-immunodeficiency-virus activity in acutely infected primary human lymphocytes.     

The sensitivity of transbronchial biopsy for the diagnosis of acute lung rejection

Transbronchial biopsy has become the procedure of choice for the diagnosis of acute lung rejection after transplantation, but the sensitivity of the technique in this setting remains unknown. In this study, 14 mongrel dogs underwent left lung transplantation, after which triple-drug immunosuppression was given for 5 days and then all immunosuppression was stopped. All animals had clear chest radiographs at this time. Transbronchial biopsy was performed in nine lung regions (two to six pieces of lung tissue were obtained per region, with a mean of 4.3 pieces per region) before the animals were killed 2 to 4 days later, at which time varying degrees of rejection had occurred. Rejection was graded histologically on a scale of 0 to 3 (0 = no rejection, 1 = mild rejection, 2 = moderate rejection, 3 = severe rejection) in each piece of lung tissue obtained at transbronchial biopsy. After the dogs were put to death, the true state of lung rejection was determined by histologic examination of the entire lung. We calculated the sensitivity of transbronchial biopsy with 95% confidence intervals. Five pieces of lung tissue were needed to yield a sensitivity of 92% (82%, 100%) to identify mild rejection in the entire lung with transbronchial biopsy. Three pieces of lung tissue were needed to yield a sensitivity of 92% (84%, 100%) to identify the presence of moderate to severe rejection in the entire lung (that is, rejection that requires pulse therapy) on transbronchial biopsy. These results indicate that three to five pieces of lung tissue that are suitable for diagnostic purposes obtained at transbronchial biopsy are adequate for the diagnosis of acute pulmonary rejection after lung transplantation.     

Bow-tie antennas on a dielectric half-space: Theory and experiment

A new formulation is discussed for the rigorous calculation of the radiation pattern of a bow-tie antenna of finite length and infinitesimal thickness, placed on a lossless dielectric substrate. The analysis is based on a representation of the current density on the metal surface of the antenna as a sum of an imposed (quasistatic) term and a set of current modes with unknown amplitudes. Free-space fields that are expressed in terms of continuous spectra of symmetrized plane waves are matched to the current modes using the method of moments. The resulting set of equations are solved for the unknown current amplitudes. The calculations show that for increasing bow length the antenna impedance spirals rapidly to a value predicted by transmission line theory. The theory also shows that theE-plane pattern of a two wavelength,60degbow-tie antenna is dominated by low-loss current modes propagating at the dielectric wavenumber. As the bow tie narrows, the loss of the modes increases, and the dominant wavenumber tends to the quasistatic value. Pattern measurements made at 94 GHz are shown to agree well with theoretical predictions. Measurements for a long-wire antenna, a linear array of bow-tie elements, and a log-periodic antenna are also presented.