Particle Detection Algorithms for Complex Plasmas

In complex plasmas, the behavior of freely floating micrometer sized particles is studied. The particles can be directly visualized and recorded by digital video cameras. To analyze the dynamics of single particles, reliable algorithms are required to accurately determine their positions to sub-pixel accuracy from the recorded images. Typically, straightforward algorithms are used for this task. Here, we combine the algorithms with common techniques for image processing. We study several algorithms and pre- and post-processing methods, and we investigate the impact of the choice of threshold parameters, including an automatic threshold detection. The results quantitatively show that each algorithm and method has its own advantage, often depending on the problem at hand. This knowledge is applicable not only to complex plasmas, but useful for any kind of comparable image-based particle tracking, e.g. in the field of colloids or granular matter

Anisotropic Acoustic Plasmons in Black Phosphorus

Recently, it was demonstrated that a graphene/dielectric/metal configuration can support acoustic plasmons, which exhibit extreme plasmon confinement an order of magnitude higher than that of conventional graphene plasmons. Here, we investigate acoustic plasmons supported in a monolayer and multilayers of black phosphorus (BP) placed just a few nanometers above a conducting plate. In the presence of a conducting plate, the acoustic plasmon dispersion for the armchair direction is found to exhibit the characteristic linear scaling in the mid- and far-infrared regime while it largely deviates from that in the long wavelength limit and near-infrared regime. For the zigzag direction, such scaling behavior is not evident due to relatively tighter plasmon confinement. Further, we demonstrate a new design for an acoustic plasmon resonator that exhibits higher plasmon confinement and resonance efficiency than BP ribbon resonators in the mid-infrared and longer wavelength regime. Theoretical framework and new resonator design studied here provide a practical route toward the experimental verification of the acoustic plasmons in BP and open up the possibility to develop novel plasmonic and optoelectronic devices that can leverage its strong in-plane anisotropy and thickness-dependent band gap

Calculation of the Electron Self Energy for Low Nuclear Charge

We present a nonperturbative numerical evaluation of the one-photon electron self energy for hydrogenlike ions with low nuclear charge numbers Z=1 to 5. Our calculation for the 1S state has a numerical uncertainty of 0.8 Hz for hydrogen and 13 Hz for singly-ionized helium. Resummation and convergence acceleration techniques that reduce the computer time by about three orders of magnitude were employed in the calculation. The numerical results are compared to results based on known terms in the expansion of the self energy in powers of (Z alpha).Comment: 10 pages, RevTeX, 2 figure

The Stroke Data Bank: Design, Methods, and Baseline Characteristics

The National Institute of Neurological and Communicative Disorders and Stroke Initiated the Stroke Data Bank, which is a Multicenter Project to Prospectively Collect Data on the Clinical Course and Sequelae of Stroke. Additional Objectives Were to Provide Information that Would Enable a Standard Diagnostic Clinical Evaluation, to Identify Prognostic Factors, and to Provide Planning Data for Future Studies. a Brief Description of the Structure and Methods Precede the Baseline Characterization of 1,805 Patients Enrolled in the Stroke Data Bank between July 1983 and June 1986. Two Thirds of These Patients Were Admitted within 24 Hours after Stroke Onset. Medical History, Neurologic History, and Hospitalization Summaries Are Presented Separately for the Following Stroke Subtypes: Infarction, Unknown Cause; Embolism from Cardiac Source; Infarction Due to Atherosclerosis; Lacune; Parenchy-Matous or Intracerebral Hemorrhage; Subarachnoid Hemorrhage; and Other. the Utility and Limitations of These Data Are Discussed. © 1988 American Heart Association, Inc

Gender and Aphasia in the Stroke Data Bank

Aphasia Was Present in 19.4% of the Men and 22.5% of the Women in the Stroke Data Bank. There Were No Gender Differences in Aphasia Incidence among the Intracerebral Hemorrhages. Aphasia Was More Frequent among Women with Infarcts (37.0%) Than Men (28.3%). When Stroke Mechanism Was Controlled For, There Was an Excess of Aphasia among the Women with Stroke Due to Cardiac Embolism. When Stroke Site Was Controlled For, There Were No Gender Differences in Aphasia Frequency. Wernicke′s, Global, and Anomic Aphasias Were More Common in Women Than Men; Broca′s Aphasia Was Somewhat More Common in Men. Although There Were No Gender Differences in Infarct Size overall, Men with Aphasia Had Larger Infarcts Than Women with Aphasia. Although Gender Differences Were Small, the Infarct Lesions Producing Aphasia in Men Were More Posteriorly Placed and the Infarct Lesions in Women Were More Anteriorly Placed, Suggesting Possible Gender Differences in the Positioning of the Language Zone in the Brain. © 1994 Academic Press, Inc

Determinants of Early Recurrence of Cerebral Infarction: The Stroke Data Bank

We Studied 1,273 Patients with Ischemic Cerebral Infarction Who Were Entered into the Stroke Data Bank, a Prospective, Observational Study Involving Four University Hospitals and the Biometry and Field Studies Branch of the National Institute of Neurological Disorders and Stroke. Forty Patients Had Non-Iatrogenic Recurrent Stroke within 30 Days after the Index Cerebral Infarction. using Life Tables, the 30-Day Cumulative± SE Risk of Early Recurrence for All Infarctions Was 3.3±0.4%. the Risk of Early Recurrence Was Greatest for Atherothrombotic Infarction (7.9±2.2%, Eight of 113 Patients) and Least for Lacunar Infarction (2.2±1.2%, Eight of 337 Patients). Both Cardioembolic Infarction (4.3±0.9%, 10 of 246 Patients) and Infarction of Undetermined Cause (3.0±0.5%, 14 of 508 Patients) Had Intermediate Risks. History of Hypertension and Diabetes Mellitus, as Well as Diastolic Hypertension and Elevated Blood Sugar Concentration at Admission, Were Associated with Early Recurrence. Logistic Regression Analysis Estimated the Risk of Early Recurrence to Be 8.56% in Those with Coexisting Hypertension and a Glucose Concentration of 300 Mg/dl Versus 0.77% in the Absence of These Two Abnormalities. Early Recurrence Was Associated with Longer Median Duration of Initial Hospital Stay (27 vs.. 14 Days) and a Higher 30-Day Case—fatality Rate (20% vs.. 7.4%). Increased Weakness Scores Were Associated with Early Recurrent Stroke. Identification of the Determinants of Early Recurrent Stroke May Lead to Better Secondary Prevention and May Help Select High-Risk Patients for Further Study. © 1989 American Heart Association, Inc