Encapsulation method for atom probe tomography analysis of nanoparticles.

Open-space nanomaterials are a widespread class of technologically important materials that are generally incompatible with analysis by atom probe tomography (APT) due to issues with specimen preparation, field evaporation and data reconstruction. The feasibility of encapsulating such non-compact matter in a matrix to enable APT measurements is investigated using nanoparticles as an example. Simulations of field evaporation of a void, and the resulting artifacts in ion trajectory, underpin the requirement that no voids remain after encapsulation. The approach is demonstrated by encapsulating Pt nanoparticles in an ZnO:Al matrix created by atomic layer deposition, a growth technique which offers very high surface coverage and conformality. APT measurements of the Pt nanoparticles are correlated with transmission electron microscopy images and numerical simulations in order to evaluate the accuracy of the APT reconstruction.

Focused ion beam fabrication of solidified ferritin into nanoscale volumes for compositional analysis using atom probe tomography.

The purpose of this investigation was to conduct atom probe tomography (APT) analyses on ferritin specimens prepared with focused ion beam (FIB) to assess whether this approach can be used to effectively characterize biomaterials. Soft matter is particularly sensitive to ion beam exposure which can induce physical and chemical changes. We employ protective metal films and low-energy ion fluence to mitigate potential problems that may be introduced by FIB. This study had two major objectives: (1) to qualitatively assess the viability of the specimens when subjected to the unique physical conditions of APT analysis, namely ultrahigh vacuum, high electric field, and thermal pulsing using a laser and (2) to quantitatively assess the data from such specimens under various experimental parameters and compare the results with appropriate control specimens. For the first objective, a range of experimental parameters were determined that met the basic criteria necessary to validate that ferritin-based specimens prepared with FIB can retain structural integrity during APT analysis. Initial field evaporation time-of-flight mass spectrometry (TOF-MS) data show that the specimens fabricated with FIB are capable of emitting ions under various laser pulsing conditions with a high electric field applied. For the second objective, the experimental parameter space was narrowed to a range that yielded data quality sufficient to produce meaningful comparison between the ferritin-based specimens and the salt-only controls.

Improvements in planar feature reconstructions in atom probe tomography.

Standard atom probe tomography spatial reconstruction techniques have been reasonably successful in reproducing single crystal datasets. However, artefacts persist in the reconstructions that can be attributed to the incorrect assumption of a spherical evaporation surface. Using simulated and experimental field evaporation, we examine the expected shape of the evaporating surface and propose the use of a variable point projection position to mitigate to some degree these reconstruction artefacts. We show initial results from an implementation of a variable projection position, illustrating the effect on simulated and experimental data, while still maintaining a spherical projection surface. Specimen shapes during evaporation of model structures with interfaces between regions of low- and high-evaporation-field material are presented. Use of two-and three-dimensional projection-point maps in the reconstruction of more complicated datasets is discussed.

Atom probe tomography analysis of poly(3-alkylthiophene)s.

Pulsed-laser atom-probe tomography is used to compare the field-evaporation mass spectrum and spatial distribution of molecular fragments from various poly(3-alkylthiophene) films deposited on sharpened aluminium specimen carriers using two different deposition methods. Films deposited via a modified solution-cast methodology yield small fragments with a uniform structural morphology whereas films deposited via an electrospray ionization methodology yield a wide range of fragments with a very non-uniform structural morphology. The main field-evaporated chemical species identified for both deposition types were, in order of typical relative abundance, C(2)H(5) (+), CH(3) (+), C(2)H(4) (+), followed by C(3)H(7,8) (+)/SC(+) and SCH(+). Thick electrospray depositions allowed investigation of the influence of laser-pulse energy on the analysis. Evidence is presented supporting the presence of a critical laser-pulse energy whereby changes in film morphology are signalled by the appearance of a new mass fragment at 190 Da.

In situ site-specific specimen preparation for atom probe tomography.

Techniques for the rapid preparation of atom-probe samples extracted directly from a Si wafer are presented and discussed. A systematic mounting process to a standardized microtip array allows approximately 12 samples to be extracted from a near-surface region and mounted for subsequent focused-ion-beam sharpening in a short period of time, about 2h. In addition, site-specific annular mill extraction techniques are demonstrated that allow specific devices or structures to be removed from a Si wafer and analyzed in the atom-probe. The challenges presented by Ga-induced implantation and damage, particularly at a standard ion-beam accelerating voltage of 30 keV, are shown and discussed. A significant reduction in the extent of the damaged regions through the application of a low-energy "clean-up" ion beam is confirmed by atom-probe analysis of the damaged regions. The Ga+ penetration depth into {100} Si at 30 keV is approximately 40 nm. Clean-up with either a 5 or 2 keV beam reduces the depth of damaged Si to approximately 5 nm and <1 nm, respectively. Finally, a NiSi sample was extracted from a Si wafer, mounted to a microtip array, sharpened, cleaned up with a 5 keV beam and analyzed in the atom probe. The current results demonstrate that specific regions of interest can be accessed and preserved throughout the sample-preparation process and that this preparation method leads to high-quality atom probe analysis of such nano-structures.

Stabilization of carbon-fiber cold field-emission cathodes with a dielectric coating.

A comprehensive investigation has been carried out to determine the source of an inherent temporal instability in the spatial distribution and the electron emission current obtained from field-emitting carbon fiber tips. These instability effects were successfully overcome by coating the tip with a sub-micron layer of dielectric epoxy resin coating. The influence of the coating thickness was studied and an optimum thickness of 0.2-0.3 microm that produced high emission stability was found. A large reduction in the intensity fluctuations of the emission image, at this coating thickness is demonstrated by using chart recorder traces in addition to slow scans of an optically monitored screen signal. The current-voltage (I-V) characteristics were obtained at a threshold field that is a few times lower than that of the uncoated tip. At low emission current levels linear F-N plots were obtained with a slope value lower than that of the uncoated emitter. The spatial distribution consisted of a very bright spot without any internal structure. The total energy distribution of the emitted electrons demonstrated a non-metallic behavior. The spectra obtained consisted of a single peak for low currents and a double peak for higher currents. The electron energy was measured relative to the Fermi level of tungsten and a spectral shift was shown to be a function of the current. Experiments have shown that the coated tips are not affected by the variations of pressure conditions down to 10(-6) mbar. These results suggest that a resin coated fiber tip offers superior performance to tungsten as a cold field emission electron source. Numerous improvements in the performance are underway. This includes a variety of polymeric coatings and more emissive carbon fibers.

The single umbilical artery in a high-risk patient population: what should be offered?

OBJECTIVE: To determine whether fetal echocardiography is warranted in cases of single umbilical artery in a population at risk for aneuploidy. METHODS: All cases of fetal single umbilical artery identified over a 2-year period were reviewed for other sonographically detected abnormalities, fetal echocardiographic results, and karyotype. RESULTS: Sixty-five cases of single umbilical artery were diagnosed on the basis of initial sonograms. Five were subsequently shown to have 3-vessel cords (8% false-positive diagnosis; incidence, 1.2%). Excluding 3 from twin gestations, 57 cases formed the study population. Thirty-one fetuses (54%) were initially thought to have isolated single umbilical arteries, and 26 (46%) had nonisolated single umbilical arteries. Fetal echocardiography was performed in 29 cases (51%), 24 (83%) with normal findings and 5 (17%) with abnormal findings. Four (50%) of 8 nonisolated single umbilical arteries had abnormal echocardiographic findings versus 1 (5%) of 21 apparently isolated single umbilical arteries (P < .05; odds ratio, 20). Karyotypes in 36 cases (63%) showed 25 (69%) euploid and 11 (31%) aneuploid fetuses. An apparently isolated single umbilical artery was never associated with an abnormal karyotype. Eleven (50%) of 22 fetuses with nonisolated single umbilical arteries had aneuploidy (P < .005). The side of the missing umbilical artery did not correlate with other sonographically detected abnormalities, abnormal fetal echocardiographic findings, or aneuploidy. CONCLUSIONS: The rate of cardiac malformations seen with apparently isolated single umbilical arteries is significant, and fetal echocardiography should be performed.

Advances in Atom Probe Specimen Fabrication from Planar Multilayer Thin Film Structures.

A sample preparation method has been developed whereby sharp needle-shaped specimens for atom probe analysis are fabricated from multilayer thin films deposited onto silicon substrates. The specimens are fabricated in an orientation such that atom probe composition profiles across the layer interfaces can be determined with atomic-layer spatial resolution, i.e., the layer normals are parallel to the needle axis. The method uses standard silicon etching techniques and focused ion-beam milling. The feasibility and utility of this technique are shown through its application to a NiFe/CoFe/Cu/CoFe-based thin film structure.

Fabrication of specimens of metamorphic magnetite crystals for field ion microscopy and atom probe microanalysis.

Field ion specimens have been successfully fabricated from samples of metamorphic magnetite crystals (Fe3O4) extracted from a polymetamorphosed, granulite-facies marble with the use of a focused ion beam. These magnetite crystals contain nanometer-scale, disk-shaped inclusions making this magnetite particularly attractive for investigating the capabilities of atom probe field ion microscopy (APFIM) for geological materials. Field ion microscope images of these magnetite crystals were obtained in which the observed size and morphology of the precipitates agree with previous results. Samples were analyzed in the energy compensated optical position-sensitive atom probe. Mass spectra were obtained in which peaks for singly ionized 16O, 56Fe and 56FeO and doubly ionized 54Fe, 56Fe and 57Fe peaks were fully resolved. Manganese and aluminum were observed in a limited analysis of a precipitate in an energy compensated position sensitive atom probe.

Evaluation of chicken infectious anemia virus and associated risk factors with disease and production losses in broilers.

A case-control study was performed to determine the significance of chicken infectious anemia virus (CIAV) as a risk factor associated with secondary disease in commercial broilers and to identify the significance of production losses associated with CIAV. The study also examined the relationship between bursal and thymic atrophy and the presence of CIAV. Cases were defined as submissions to the Alabama Veterinary Diagnostic Laboratories with a history of clinical disease and with a diagnosis of coccidiosis, gangrenous dermatitis, or respiratory disease. Controls were selected from submissions with neither a history of disease nor evidence of disease on necropsy. CIAV was detected in fresh tissues by polymerase chain reaction. Both thymic atrophy and the detection of CIAV were significantly associated with a disease case (P < 0.05). Bursal atrophy was a significant risk factor associated with the detection of CIAV in a submission (P < 0.05). Whereas CIAV was associated with disease cases that showed production losses in both percentage of livability and percentage of condemnations (P < 0.05), detection of CIAV alone was not associated with detectable losses in production or flock performance.

Endoscopic coronary artery bypass graft (ECABG) procedure with robotic assistance.

BACKGROUND: Technical details of the Robotically assisted endoscopic coronary artery bypass graft (ECABG) procedure on the cadaver model are reported. Moreover, this study will provide essential techniques, steps, and procedural development concepts necessary to introduce the ZEUS Robotic Surgical System (Computer Motion, Inc., Goleta, CA) into the human operating room. METHODS: Between August 1998 and March 1999, an ECABG procedure was performed on 10 cadaver torsos. The cadaver torso was placed in the left anterior oblique (LAO) position. The left and right internal mammary arteries (IMA) were taken down endoscopically. The ends of the IMA's were intracorporeally prepared. An upper partial sternotomy was demonstrated for perfusion cannulation and proximal anastomoses for multiple vessel revascularization. An arteriotomy was created with an endoscopic scalpel. The IMA was anastomosed to a chosen coronary using robotic assistance. The patency was verified by probing and injecting of methylene blue. RESULTS: Templates were developed to determine the placement of the robotic arms. Port templates were developed to both harvest the IMA's and perform the desired anastomoses. The following vessels were accessed through the developed port templates and retraction of the heart: left anterior descending (LAD), right coronary artery (RCA), diagonal (D(1)), obtuse marginal (OM(1) and OM(2)), and posterior descending artery (PDA). CONCLUSIONS: The use of robotic assistance during an ECABG procedure on a cadaver model is feasible. This study is a necessary and useful progression from the use of robotics in the animal lab to the use of robotics in the human operating room.

Maternal characteristics and risk of severe neonatal thrombocytopenia and intracranial hemorrhage in pregnancies complicated by autoimmune thrombocytopenia.

OBJECTIVE: The antenatal and intrapartum management of women with autoimmune thrombocytopenia is controversial. The current approach emphasizes an effort to identify maternal characteristics predictive of severe neonatal thrombocytopenia or to measure fetal platelet counts and perform cesarean section in patients considered to be at risk for neonatal intracranial hemorrhage. In the current study we review our experience with maternal autoimmune thrombocytopenia and neonatal outcome. STUDY DESIGN: Fifty-five pregnancies with autoimmune thrombocytopenia over a 10-year period in three major medical centers in San Diego, California, were evaluated. Maternal characteristics and neonatal outcomes were assessed and compared with those in other recent reports. Data were submitted to Fisher's exact (two-tailed), chi2, and Student t tests, with linear regression performed to analyze the association between variables. RESULTS: Maternal characteristics including platelet count, presence of antiplatelet antibody, antecedent history of autoimmune thrombocytopenia, and corticosteroid therapy were not predictive of severe neonatal thrombocytopenia. Maternal history of splenectomy was significantly correlated with fetal platelet counts <50 x 10(9)/L (odds ratio 5.63; 95% confidence interval 2.2 to 14.3). There were four neonates with severe neonatal thrombocytopenia (8%), and one who was delivered by cesarean section had intracranial hemorrhage. CONCLUSIONS: These findings, combined with others in the literature, confirm that severe neonatal thrombocytopenia is an infrequent complication of maternal autoimmune thrombocytopenia and is not reliably predicted by maternal characteristics. Intracranial hemorrhage is also a rare event and is not related to mode of delivery. Cesarean section should be reserved for obstetric indications only.

Hepatocyte nuclear factor 3/fork head homolog 11 is expressed in proliferating epithelial and mesenchymal cells of embryonic and adult tissues.

The hepatocyte nuclear factor 3alpha (HNF-3alpha) and 3beta proteins have homology in the winged helix/fork head DNA binding domain and regulate cell-specific transcription in hepatocytes and in respiratory and intestinal epithelia. In this study, we describe two novel isoforms of the winged helix transcription factor family, HNF-3/fork head homolog 11A (HFH-11A) and HFH-11B, isolated from the human colon carcinoma HT-29 cell line. We show that these isoforms arise via differential splicing and are expressed in a number of epithelial cell lines derived from tumors (HT-29, Caco-2, HepG2, HeLa, A549, and H441). We demonstrate that differentiation of Caco-2 cells toward the enterocyte lineage results in decreased HFH-11 expression and reciprocal increases in HNF-3alpha and HNF-3beta mRNA levels. In situ hybridization of 16 day postcoitus mouse embryos demonstrates that HFH-11 expression is found in the mesenchymal and epithelial cells of the liver, lung, intestine, renal cortex, and urinary tract. Although HFH-11 exhibits a wide cellular expression pattern in the embryo, its adult expression pattern is restricted to epithelial cells of Lieberkühn's crypts of the intestine, the spermatocytes and spermatids of the testis, and the thymus and colon. HFH-11 expression is absent in adult hepatocytes, but its expression is reactivated in proliferating hepatocytes at 4, 24, and 48 h after partial hepatectomy. Consistent with these findings, we demonstrate that HFH-11 mRNA levels are stimulated by intratracheal administration of keratinocyte growth factor in adult lung and its expression in an adult endothelial cell line is reactivated in response to oxidative stress. These experiments show that the HFH-11 transcription factor is expressed in embryonic mesenchymal and epithelial cells and its expression is reactivated in these adult cell types by proliferative signals or oxidative stress.

On the many advantages of local-electrode atom probes.

Local extraction electrodes offer several crucial advantages for operation of atom probes. Because of the proximity of the local extraction electrode to the specimen, the electric field produced at the specimen apex by a given voltage is enhanced and the voltage required for field evaporation is reduced. In a voltage-pulsed atom probe, the absolute magnitude of the energy uncertainty is correspondingly reduced. High mass resolution (m/deltam > 1000) may therefore be obtained by accelerating the evaporated ions to a greater total potential after the local extraction electrode. The low extraction voltage may also be pulsed rapidly (100 ps rise time) and at high repetition rates (up to 10(5) pulses per second) using currently available solid-state pulsers. Furthermore, a local electrode and intermediate electrodes may be used as optical elements to control the image magnification. All of these benefits may be applied to any type of atom probe. Local-electrode atom probes (LEAP) should be especially advantageous for developing three-dimensional atom probes with high mass resolution and a large field of view. A sample has been developed that consists of many microtips formed on a planar sample using ion beam mask etching. Microtip samples are especially suited to LEAP. Analysis of electrically insulating samples may also be possible with microtip samples in a LEAP. This combination of features suggests flexible, high speed, high mass resolution atom probes that can work with either conventional needle-shaped specimens or the new style of planar microtip specimens.

Hemodynamic and fluid responses to furosemide infusion in the ovine fetus.

OBJECTIVES: The direct effects of furosemide infusion have not been systematically examined in the fetus. Our objective was to explore the hemodynamic and urinary responses to a 4-hour infusion of furosemide into fetal sheep. STUDY DESIGN: Furosemide (0, 1, 5, or 10 mg/hr) was infused into the fetal inferior vena cava for 4 hours in 15 chronically catheterized near-term sheep. RESULTS: Relative to vehicle infusion, furosemide produced dose-dependent increases in fetal arterial pressure (analysis of variance, p < 0.05 when comparing groups), fetal heart rate (p < 0.0001), urine flow (p < 0.0001), and urine osmolality, sodium, and chloride, concentrations (p < 0.0001). Concomitantly, there were dose-dependent decreases in fetoplacental blood volume, fetal plasma chloride (p < 0.0001) and fetal venous pressure (p < 0.05). The changes in urine flow rate and fetal arterial pressure were positively correlated (r = 0.46, p < 0.01), suggesting that the diuresis was mediated in part by fetal arterial pressure. The four-quadrant amniotic fluid index increased during the furosemide infusions but not during vehicle infusions (p = 0.022). CONCLUSIONS: Furosemide infusion caused a marked dose-dependent diuresis in the ovine fetus that appears to be partly mediated by increases in vascular pressure. Although amniotic fluid volume increases and fetal blood volume decreases, the reduction in blood volume was small compared with the urine volume excreted.

Bullous systemic lupus erythematosus.

Two patients with established systemic lupus erythematosus developed bullous dermatoses clinically suggestive of bullous pemphigoid (BP). Direct immunofluorescence demonstrated linear staining at the dermoepidermal junction for IgG and C3 in a pattern typical for BP. However, immunoelectron microscopy demonstrated deposits of IgG largely below the basal lamina, with little if any deposit present within the lamina lucida. These findings are consistent with systemic lupus erythematosus (SLE) and effectively rule out BP. In addition, the leukocyte attachment assay, an in vitro assay of the functional activity of tissue-deposited immune complexes, demonstrated strong attachment of leukocytes to the dermoepidermal junction of patients' skin, suggesting that the immune reactants were functional immune complexes of possible importance to the pathogenesis of the bullous lesions. To our knowledge, this is the first time that immunoelectron microscopy has been performed on skin from patients suspected of manifesting concurrent SLE and BP. Our findings cast doubt on previous such reports by demonstrating the existence of a bullous form of SLE resembling BP both clinically and by direct immunofluorescence.

Technique and value of operative arteriography in coronary artery bypass operations.

In an attempt to make evaluation of coronary artery bypass more meaningful, operative coronary arteriography has been used to aid in defining more precisely the technical aspects of the operation at a time when corrective measures can be carried out. Arteriography is performed following the completion of distal bypass graft anastomoses, whether saphenous vein or internal mammary artery (IMA) bypasses are used. Cut films are exposed at the rate of 2 to 4 frames per second and are evaluated for showing (1) status of anastomosis, (2) status of runoff, (3) lesions undetected preoperatively, and (4) any problems with the bypass conduit. A total of 934 vessels (including 107 IMA grafts) have been visualized in 535 patients. Some form of technical revision was necessary in nine instances. The use of this technique during intraoperative balloon dilatation, in conjunction with and to extend the benefits of conventional bypass, is currently being evaluated.

Arterial fibromuscular disease. Observations on pathogenesis and surgical management.

Fibromuscular dysplasia is being recognized more often as a significant pathologic vascular disease separate from atherosclerosis. The pathogenesis and pathology are still being investigated. This disease involves mainly three areas--renal, carotid and iliac arteries--with the renal area being the most common. Surgery has been used almost exclusively for symptomatic lesions, and the indications and procedures have been refined since the original procedures of resection and grafting. In patients with renal involvement, we first attempt to treat hypertension medically, followed by surgery if this is unsuccessful. In those with carotid involvement, we are very aggressive with symptomatic lesions since there is a 22 percent incidence of a significant preceding event in the patients operated on. In patients with iliac involvement, we treat according to symptoms. Graduated internal dilatation has been used very successfully alone and in combination with other methods. Postoperative follow-up and arteriography have shown the effects of surgery to be lasting and rewarding, with minimal morbidity and mortality and no recurrence.