Lateral Ge Diffusion During Oxidation of Si/SiGe Fins.

This Letter reports on the unusual diffusion behavior of Ge during oxidation of a multilayer Si/SiGe fin. It is observed that oxidation surprisingly results in the formation of vertically stacked Si nanowires encapsulated in defect free epitaxial strained SixGe1-x. High angle annular dark field scanning transmission electron microscopy (HAADF-STEM) shows that extremely enhanced diffusion of Ge occurs along the vertical Si/SiO2 oxidizing interface and is responsible for the encapsulation process. Further oxidation fully encapsulates the Si layers in defect free single crystal SixGe1-x (x up to 0.53), which results in Si nanowires with up to -2% strain. Atom probe tomography reconstructions demonstrate that the resultant nanowires run the length of the fin. We found that the oxidation temperature plays a significant role in the formation of the Si nanowires. In the process range of 800-900 °C, pure strained and rounded Si nanowires down to 2 nm in diameter can be fabricated. At lower temperatures, the Ge diffusion along the oxidizing Si/SiO2 interface is slow, and rounding of the nanowire does not occur, while at higher temperatures, the diffusivity of Ge into Si is sufficient to result in dilution of the pure Si nanowire with Ge. The use of highly selective etchants to remove the SiGe could provide a new pathway for the creation of highly controlled vertically stacked nanowires for gate all around transistors.

Effects of thermal annealing on the structural and optical properties of carbon-implanted SiO2.

Amorphous carbon (a-C) nanoclusters were synthesized by the implantation of carbon ions (C-) into thermally grown silicon dioxide film (-500 nm thick) on a Si (100) wafer and processed by high temperature thermal annealing. The carbon ions were implanted with an energy of 70 keV at a fluence of 5 x 10(17) atoms/cm2. The implanted samples were annealed at 1100 degrees C for different time periods in a gas mixture of 96% Ar+4% H2. Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and High Resolution Transmission Electron Microscopy (HRTEM) were used to study the structural properties of both the as-implanted and annealed samples. HRTEM reveals the formation of nanostructures in the annealed samples. The Raman spectroscopy also confirms the formation of carbon nano-clusters in the samples annealed for 10 min, 30 min, 60 min and 90 min. No Raman features originating from the carbon-clusters are observed for the sample annealed further to 120 min, indicating a complete loss of implanted carbon from the SiO2 layer. The loss of the implanted carbon in the 120 min annealed sample from the SiO2 layer was also observed in the XPS depth profile measurements. Room temperature photoluminescence (PL) spectroscopy revealed visible emissions from the samples pointing to carbon ion induced defects as the origin of a broad 2.0-2.4 eV band, and the intrinsic defects in SiO2 as the possible origin of the -2.9 eV bands. In low temperature photoluminescence spectra, two sharp and intense photoluminescence lines at -3.31 eV and -3.34 eV appear for the samples annealed for 90 min and 120 min, whereas no such bands are observed in the samples annealed for 10 min, 30 min, and 60 min. The Si nano-clusters forming at the Si-SiO2 interface could be the origin of these intense peaks.

Comparison of convergent beam electron diffraction and geometric phase analysis for strain measurement in a strained silicon device.

Convergent beam electron diffraction and geometric phase analysis were used to measure strain in the gate channel of a p-type strained silicon metal-oxide-semiconductor field-effect transistor. These measurements were made on exactly the same transmission electron microscopy specimen allowing for direct comparison of the relative advantages of each technique. The trends in the strain values show good agreement in both the [110] and [001] directions, but the absolute strain values are offset from each other. This difference in the absolute strain measured using the two techniques is attributed to the way the reference strain is defined for each.

A high-entropy manganite in an ordered nanocomposite for long-term application in solid oxide cells.

The implementation of nano-engineered composite oxides opens up the way towards the development of a novel class of functional materials with enhanced electrochemical properties. Here we report on the realization of vertically aligned nanocomposites of lanthanum strontium manganite and doped ceria with straight applicability as functional layers in high-temperature energy conversion devices. By a detailed analysis using complementary state-of-the-art techniques, which include atom-probe tomography combined with oxygen isotopic exchange, we assess the local structural and electrochemical functionalities and we allow direct observation of local fast oxygen diffusion pathways. The resulting ordered mesostructure, which is characterized by a coherent, dense array of vertical interfaces, shows high electrochemically activity and suppressed dopant segregation. The latter is ascribed to spontaneous cationic intermixing enabling lattice stabilization, according to density functional theory calculations. This work highlights the relevance of local disorder and long-range arrangements for functional oxides nano-engineering and introduces an advanced method for the local analysis of mass transport phenomena.

Using a <670> zone axis for convergent beam electron diffraction measurements of lattice strain in strained silicon.

Convergent beam electron diffraction patterns of silicon from the gate channel region of a complementary metal-oxide-semiconductor transistor with recessed Si(.82)Ge(.18) stressors were analysed using three zone axes: <230>, <340> and <670>. Values measured using these axes were compared with each other with regards to strain along the [110] and the [001] directions. It was demonstrated that strain measurements made using all three axes showed reasonable agreement with each other: an increase in the [110] compressive strain and a switch from compressive to tensile strain in the [001] with decreasing distance below the gate. It was also observed that the strain calculations using the <230> axis had the lowest uncertainty whereas the <670> axis allowed for measurements closest to the gate due to the improved lateral resolution at that tilt angle.

Morphine and outcomes in acute decompensated heart failure: an ADHERE analysis.

OBJECTIVE: Morphine is a long-standing therapy in acute decompensated heart failure (ADHF), despite few supporting data. A study was undertaken to compare the outcomes of patients who did and did not receive morphine for ADHF. METHODS: The study was a retrospective analysis of the Acute Decompensated Heart Failure National Registry (ADHERE) which enrols hospitalised patients with treatment for, or a primary discharge diagnosis of, ADHF. Patients were stratified into cohorts based on whether or not they received intravenous morphine. ANOVA, Wilcoxon and chi(2) tests were used in univariate analysis, followed by multivariate analysis controlling for parameters previously associated with mortality. Analyses were repeated for ejection fraction subgroups and in patients not on mechanical ventilation. RESULTS: There were 147 362 hospitalisations in ADHERE at December 2004, 20 782 of whom (14.1%) received morphine and 126 580 (85.9%) did not. There were no clinically relevant differences between the groups in the initial age, heart rate, blood pressure, blood urea nitrogen, creatinine, haemoglobin, ejection fraction or atrial fibrillation. A higher prevalence of rest dyspnoea, congestion on chest radiography, rales and raised troponin occurred in the morphine group. Patients on morphine received more inotropes and vasodilators, were more likely to require mechanical ventilation (15.4% vs 2.8%), had a longer median hospitalisation (5.6 vs 4.2 days), more ICU admissions (38.7% vs 14.4%), and had greater mortality (13.0% vs 2.4%) (all p<0.001). Even after risk adjustment and exclusion of ventilated patients, morphine was an independent predictor of mortality (OR 4.84 (95% CI 4.52 to 5.18), p<0.001). CONCLUSIONS: Morphine is associated with increased adverse events in ADHF which includes a greater frequency of mechanical ventilation, prolonged hospitalisation, more ICU admissions and higher mortality.

Initial risk stratification and presenting characteristics of patients with evolving myocardial infarctions.

OBJECTIVES: To describe the presenting characteristics and risk stratification of patients presenting to the emergency department with chest pain who have a normal initial troponin level followed by a raised troponin level within 12 h (evolving myocardial infarction (EMI)). METHODS: Data from the Internet Tracking Registry for Acute Coronary Syndromes (i*trACS), a registry of patients presenting with undifferentiated chest pain, were used. This analysis included patients without ST segment elevation with at least two troponin assay results < or = 12 h apart. Patients were stratified into three groups: EMI (initial troponin assay negative, second troponin assay positive), non-ST elevation myocardial infarction (NSTEMI) (initial troponin assay positive) and no MI (all troponin assays negative). RESULTS: Of 4136 eligible patients, 5% had EMI, 8% had NSTEMI and 87% had no MI. Patients with EMI were more similar to those with NSTEMI than those with no MI with respect to demographic characteristics, presentation, admission patterns and revascularisation. The initial ECG in patients with EMI was most commonly non-diagnostic (51%), but physicians' initial impressions commonly reflected MI, unstable angina or high-risk chest pain (76%). This risk assessment was followed by a high rate of critical care admissions (32%) and revascularisation (percutaneous coronary intervention 17%) among patients with EMI. CONCLUSION: Patients with EMI appear similar at presentation to those with NSTEMI. Patients with EMI are perceived as being at high risk, evidenced by similar diagnostic impressions, admission practices and revascularisation rates to patients with NSTEMI.

Laser-assisted atom probe tomography of Ti/TiN films deposited on Si.

Laser-assisted atom probe tomography (L-APT) was used to examine superconducting TiN/Ti/TiN trilayer films with nominal respective thicknesses of 5/5/5 (nm). Such materials are of interest for applications that require large arrays of microwave kinetic inductance detectors. The trilayers were deposited on Si substrates by reactive sputtering. Electron energy loss microscopy performed in a scanning transmission electron microscope (STEM/EELS) was used to corroborate the L-APT results and establish the overall thicknesses of the trilayers. Three separate batches were studied where the first (bottom) TiN layer was deposited at 500°C (for all batches) and the subsequent TiN/Ti bilayer was deposited at ambient temperature, 250°C, and 500°C, respectively. L-APT rendered an approximately planar TiN/Si interface by making use of plausible mass-spectral assignments to N31+, SiN1+, and SiO1+. This was necessary since ambiguities associated with the likely simultaneous occurrence of Si1+ and N21+ prevented their use in rendering the TiN/Si interface upon reconstruction. The non-superconducting Ti2N phase was also revealed by L-APT. Neither L-APT nor STEM/EELS rendered sharp Ti/TiN interfaces and the contrast between these layers diminished with increased film deposition temperature. L-APT also revealed that hydrogen was present in varying degrees in all samples including control samples that were composed of single layers of Ti or TiN.

Evaluation of chest pain suspicious for acute coronary syndrome: use of an accelerated diagnostic protocol in a chest pain evaluation unit.

Management of patients presenting to the emergency department with chest pain suggestive of acute myocardial infarction (AMI) remains a continuing challenge. A low threshold for admission has been traditional because of concern for patient welfare and the litigation potential associated with the inadvertent discharge of patients with ischemic events. Because of this approach, < 30% of patients admitted for chest pain ultimately are found to have an acute coronary syndrome. To reduce unnecessary admissions, maintain patient safety, and enhance cost-effectiveness, innovative strategies have been applied to the management of patients with chest pain. It is now recognized that a low-risk group can be identified by the clinical presentation and initial electrocardiogram. Chest-pain centers have been developed to provide further risk stratification and systematic management of these patients. We employ an accelerated diagnostic protocol based on immediate exercise treadmill testing to evaluate low-risk patients. Moderate-risk patients are assessed over a 6-hour observation period with serial electrocardiograms and evaluation of cardiac-injury markers. Patients with positive evaluations are admitted. Those with negative results undergo either exercise echocardiography or rest myocardial perfusion imaging utilizing technetium-99m sestamibi. Patients with positive functional tests are admitted. Those with negative studies are discharged with outpatient follow-up. These strategies have provided a safe and accurate means of patient disposition from the emergency department with the potential for vital cost savings.

Identification of patients at risk by graded exercise testing in an emergency department chest pain center.

The study applied a retrospective follow-up design to determine the prognostic effect of graded exercise testing (GXT) in patients with low- to moderate-risk chest pain evaluated in an emergency department 9-hour protocol chest pain center (CPC) from January 1, 1993 to August 1, 1996. The cohort of 1,209 patients were followed to the date of death or first adverse cardiac event up to 1 year after CPC admission. Cardiac events were defined as coronary artery bypass graft, percutaneous transluminal coronary angioplasty, cardiogenic shock, cardiac-related death, congestive heart failure admission, ventricular tachycardia/ventricular fibrillation arrest, and myocardial infarction. Patients with acute ST-segment elevation or depression of >1 mm, positive enzyme (creatine kinase myocardial band) testing, or unstable angina during their CPC evaluation were admitted without GXT testing. Statistical analysis included chi-square test for complication rates and Cox proportional-hazards modeling. Nine hundred fifty-eight of 1,209 patients underwent GXT testing. Patients with positive, inconclusive, and normal GXTs had complication rates of 36.8% (7 of 19), 3.4% (9 of 267), and 1.1% (5 of 456), respectively. After adjusting for age, sex, and race, the relative risk of complication was 38.9 (95% confidence interval 11.7 to 129.6) with a positive GXT, and 3.6 (95% confidence interval 1.2 to 10.7) with an inconclusive GXT compared with a normal GXT. The GXT is a good prognostic indicator of adverse cardiac events in low- to moderate-risk chest pain in patients evaluated in an emergency department CPC.

Treatment of submassive pulmonary embolism with tenecteplase or placebo: cardiopulmonary outcomes at 3 months: multicenter double-blind, placebo-controlled randomized trial.

BACKGROUND: Acute pulmonary embolism (PE) can worsen quality of life due to persistent dyspnea or exercise intolerance. OBJECTIVE: Test if tenecteplase increases the probability of a favorable composite patient-oriented outcome after submassive PE. METHODS: Normotensive patients with PE and right ventricular (RV) strain (by echocardiography or biomarkers) were enrolled from eight hospitals. All patients received low-molecular-weight heparin followed by random assignment to either a single weight-based bolus of tenecteplase or placebo, administered in a double-blinded fashion. The primary composite outcome included: (i) death, circulatory shock, intubation or major bleeding within 5 days or (ii) recurrent PE, poor functional capacity (RV dysfunction with either dyspnea at rest or exercise intolerance) or an SF36(®) Physical Component Summary (PCS) score < 30 at 90-day follow-up. RESULTS: Eighty-three patients were randomized; 40 to tenecteplase and 43 to placebo. The trial was terminated prematurely. Within 5 days, adverse outcomes occurred in three placebo-treated patients (death in one and intubation in two) and one tenecteplase-treated patient (fatal intracranial hemorrhage). At 90 days, adverse outcomes occurred in 13 unique placebo-treated patients and five unique tenecteplase-treated patients Thus, 16 (37%) placebo-treated and six (15%) tenecteplase-treated patients had at least one adverse outcome (exact two-sided P = 0.017). CONCLUSIONS: Treatment of patients with submassive pulmonary embolism with tenecteplase was associated with increased probability of a favorable composite outcome.

Polymorphisms in CYP2D6 may predict methamphetamine related heart failure.

BACKGROUND: Methamphetamine (METH) has been associated with a dilated cardiomyopathy. The first and rate-limiting step of metabolism is dependent on the polymorphic enzyme CYP2D6. OBJECTIVES: To evaluate if polymorphisms in CYP2D6 can be associated with the development of a methamphetamine-induced cardiomyopathy. METHODS: We performed a prospective case-control pilot study. Cases were defined by a urinary drug screen positive for amphetamine and evidence of heart failure by beta natriuretic peptide (BNP) greater than 300 pg/ml and symptoms of heart failure. Controls were defined with urinary drug screens positive for amphetamines but without evidence of heart failure defined by a BNP lesser than 300 pg/ml or symptoms of heart failure. Exclusion criteria were less than 18 years or greater than 60 years of age, urinary toxicology screen positive for additional stimulants, known coronary artery disease (CAD) defined by greater than 50% stenosis on catheterization or previous myocardial infarction, known cardiomyopathy of alternative etiology or inability to provide consent. Patients underwent gas chromatography confirmation-mass spectroscopy for methamphetamine, genotyping of CYP2D6, limited echocardiography, and participated in a modified 2007 National Survey of Drug Use and Health Stimulant Survey. Genotype results were analyzed with traditional classifications and "Activity Scores". RESULTS: Fifty-six patients completed the study with 19 cases and 37 controls. There was no statistically significant difference in days of use in a month, age, gender, or ethnicity between cases and controls. While not statistically significant, age and days of use did trend higher in cases. CYP2D6 genotype demonstrated that the lower the activity score/poor metabolizer group had less heart failure than extensive metabolizers/higher activity score. However, it did not reach statistical significance. When adjusting for higher days of use, extensive metabolizers had the highest odds of developing a dilated cardiomyopathy. (OR: 2.33, 95% CI: 0.54-10.13). Echo findings in all cases showed reduced ejection fractions with a mean of 18.6% (range: 10-35%) and 70% had a dilated cardiomyopathy. No cardiomyopathies were seen in the controls. Mean ejection fraction was 56.75% (range: 45-70%). The odds ratio of having a dilated cardiomyopathy in extensive metabolizers was 1.62 (95% CI: 0.47-5.5). CONCLUSION: Our study demonstrates a trend that individuals with decreased metabolic activity were less likely to develop heart failure. While not statistically significant, a signal is present that extensive metabolizers may be at increased risk for the development of a cardiomyopathy.

Interpretation of immediate exercise treadmill test: interreader reliability between cardiologist and noncardiologist in a chest pain evaluation unit.

STUDY OBJECTIVE: To determine whether attending physicians in a chest pain evaluation unit (CPEU) can perform and interpret exercise testing with the same accuracy as cardiologists. METHODS: Between January 1996 and November 1998, immediate exercise tests were performed and interpreted by internists with additional training in exercise testing who serve as attending physicians in a CPEU at a large university medical center. For quality assurance, all tests were overread by a cardiologist. Test results were compared for each reader, and all tests with discrepant readings were reinterpreted by an independent cardiologist who was blinded to the previous results. Patients' clinical course was monitored for at least 30 days after exercise testing. RESULTS: The study group consisted of 645 patients (347 men, 298 women). Discrepant interpretations were found in 11 (1. 7%) patients. The agreement was 98.4% (kappa value 0.9618). The majority of discrepancies were insignificant and were based on subtle differences in the definition of a nondiagnostic test or the degree of ST-segment shift. Of the 11 discordant readings, the blinded cardiologist concurred with 5 (45%) of the CPEU interpretations and 4 (36%) of the cardiologist interpretations. In 2 cases, there was disagreement by all 3 interpreters. There was no cardiac morbidity or mortality of any patient with a discrepant reading. CONCLUSION: Our results suggest that noncardiologists serving as attending physicians in a CPEU can accurately interpret exercise tests and overreading by cardiologists for quality assurance is unnecessary.

Measurement of cardiac troponin T is an effective method for predicting complications among emergency department patients with chest pain.

STUDY OBJECTIVES: To determine the test performance characteristics of serum cardiac troponin T (cTnT) measurement for diagnosis of acute myocardial infarction (AMI), and to determine the ability of cTnT to stratify emergency department patients with chest pain into high- and low-risk groups for cardiac complications. METHODS: We conducted a prospective observational cohort study with convenience sampling in a tertiary care, urban ED. The study sample comprised 667 patients presenting to the ED with a complaint of chest pain or other symptoms suggesting acute ischemic coronary syndrome (AICS). Patients were assigned to different blood sampling protocols for cTnT therapy on the basis of their ECG at presentation: nondiagnostic for AMI at 0, 3, 6, 9, 12, and 24 hours after ED presentation; or ECG diagnostic for AMI at 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 12, 18, and 24 hours after ED presentation. RESULTS: Of 667 patients, 34 had AMI diagnosed within 24 hours of ED arrival. Using a .2 microgram/L discrimination level for cTnT, sensitivity for AMI within 24 hours of ED arrival was 97% (95% confidence interval, 91.4% to 99.9%), and specificity was 92% (89.8%-94.1%). When the effects of age, race, sex, and creatine kinase-MB isoenzyme subunit test results were controlled, a patient with cTnT of .2 microgram/L or greater was 3.5 (1.4 to 9.1) times more likely to have a cardiac complication within 60 days of ED arrival than a patient with a cTnT value below .2 microgram/L. CONCLUSION: Measurement of cTnT will accurately identify myocardial necrosis in patients presenting to the ED with possible AICS. Elevated cTnT values identify patients at increased risk of cardiac complications.