Background: A lack of standardized assays and consensus of cell definition has lead to a wide variation in the reported range of circulating endothelial cells (CECs). Methods: An automated rare cell analysis system was used to enumerate nucleated, CD146+/CD105+/CD45− CECs in 4 mL of blood. Results: Recoveries of spiked HUVECs were linear over a range of 0–1,241 cells (R2 ≥ 0.99) with recoveries of ≥70% at each spike level. Correlation coefficient values for interoperator variability and duplicate sample variation were (R2 = 0.99 and 0.90), respectively. Correlation of CEC counts between tubes 1–2 and 2–3 drawn from the same subject in sequence differed (R2 = 0.48 and 0.63, respectively). The normal CEC reference range established in 249 healthy donors was 1–20 CECs/mL blood. CEC counts were significantly higher in the 206 metastatic carcinoma patients (P < 0.0001). Conclusion: CECs can be accurately and reproducibly enumerated in blood and are elevated in metastatic carcinomas compared with healthy donors. Phlebotomy procedures can affect endothelial cell counts. © 2007 International Society for Analytical Cytology

Using coherent x-ray speckle metrology, we have measured the influence of disorder on major loop return point memory (RPM) and complementary point memory (CPM) for a series of perpendicular anisotropy Co/Pt multilayer films. In the low disorder limit, the domain structures show no memory with field cycling--no RPM and no CPM. With increasing disorder, we observe the onset and the saturation of both the RPM and the CPM. These results provide the first direct ensemble-sensitive experimental study of the effects of varying disorder on microscopic magnetic memory and are compared against the predictions of existing theories.

Beautiful theories of magnetic hysteresis based on random microscopic disorder have been developed over the past ten years. Our goal was to directly compare these theories with precise experiments. We first developed and then applied coherent x-ray speckle metrology to a series of thin multilayer perpendicular magnetic materials. To directly observe the effects of disorder, we deliberately introduced increasing degrees of disorder into our films. We used coherent x-rays to generate highly speckled magnetic scattering patterns. The apparently random arrangement of the speckles is due to the exact configuration of the magnetic domains in the sample. In effect, each speckle pattern acts as a unique fingerprint for the magnetic domain configuration. Small changes in the domain structure change the speckles, and comparison of the different speckle patterns provides a quantitative determination of how much the domain structure has changed. How is the magnetic domain configuration at one point on the major hysteresis loop related to the configurations at the same point on the loop during subsequent cycles? The microscopic return-point memory(RPM) is partial and imperfect in the disordered samples, and completely absent when the disorder was not present. We found the complementary-point memory(CPM) is also partial and imperfect in the disordered samples and completely absent when the disorder was not present. We found that the RPM is always a little larger than the CPM. We also studied the correlations between the domains within a single ascending or descending loop. We developed new theoretical models that do fit our experiments.Comment: 26 pages, 25 figures, Accepted by Physical Review B 01/25/0

We have used coherent, resonant, x-ray magnetic speckle patterns to measure the statistical evolution of the microscopic magnetic domains in perpendicular magnetic films as a function of the applied magnetic field. Our work constitutes the first direct, ensemble-averaged study of microscopic magnetic return point memory, and demonstrates the profound impact of interfacial roughness on this phenomenon. At low fields, the microscopic magnetic domains forget their past history with an exponential field dependence.PACS numbers: 07.85.+n, 78.70.Dm, 78.70.Cr The invention of the laser revolutionized visible optics. We are on the verge of a similar revolution in x-ray optics. Fully-coherent, quasicontinuous beams of x-rays are now available from the third-generation synchrotron sources, and extremely intense, fully-coherent, pulsed beams from fourth-generation synchrotron sources are on the horizon. One of the most exciting applications is to use these coherent beams to do the x-ray analog of laser light scattering to study the spacetime correlations in materials at the nanoscopic and atomic length scales. Such coherent x-ray studies have achieved time resolutions from microseconds to nanoseconds at a length scale of a few nanometers [1]. Another promising application is to use the fourth-generation sources to do holographic or speckle x-ray imaging to determine the complete structure of the sample with atomic resolution using a single femtosecond duration beam pulse. Such "lenseless speckle reconstruction" has recently been demonstrated for x-ray charge scattering [2], and it is just beginning to be explored for x-ray magnetic scattering [3].In this letter, we describe a new form of reconstructionless x-ray speckle metrolology using coherent, resonant, magnetic x-ray scattering. We show that the speckle patterns act as a fingerprint of the specific domain configuration and allow the ensemble of microscopic magnetic domains to be monitored versus the applied field history. By comparing speckle patterns, we obtain a quantitative measure of the domain evolution during the reversal process and directly probe the microscopic mechanisms of hysteresis. Magnetic hysteresis is fundamental to all magnetic storage technology, and this technology is one cornerstone of the present information age. Yet, despite decades of intense study [4] and significant recent advances[5], we still do not have a fully satisfactory microscopic understanding of magnetic hysteresis.In his 1905 dissertation at Gottingen, Madelung defined macroscopic return point memory (RPM) as follows: Suppose a magnetic system on the major hysteresis loop is subject to a change in the applied field that causes an excursion along a minor hysteresis loop inside the major loop; if the applied field is readjusted back to its original value and the sample returns to its initial magnetization, then macroscopic RPM is said to exist. Madelung's macroscopic characterization immediately raises the question of how the ferromagnetic domains behave on a microscopic level. Do...