Radiometric correction of multi-temporal Landsat data for characterization of early successional forest patterns in western Oregon

Detecting and characterizing continuous changes in early forest succession using multi-temporal satellite imagery requires atmospheric correction procedures that are both operationally reliable, and that result in comparable units (e.g., surface reflectance). This paper presents a comparison of five atmospheric correction methods (2 relative, 3 absolute) used to correct a nearly continuous 20-year Landsat TM/ETM+ image data set (19-images) covering western Oregon (path/row 46/29). In theory, full absolute correction of individual images in a time-series should effectively minimize atmospheric effects resulting in a series of images that appears more similar in spectral response than the same set of uncorrected images. Contradicting this theory, evidence is presented that demonstrates how absolute correction methods such as Second Simulation of the Satellite Signal in the Solar Spectrum (6 s), Modified Dense Dark Vegetation (MDDV), and Dark Object Subtraction (DOS) actually make images in a time-series somewhat less spectrally similar to one another. Since the development of meaningful spectral reflectance trajectories is more dependant on consistent measurement of surface reflectance rather than on accurate estimation of true surface reflectance, correction using image pairs is also tested. The relative methods tested are variants of an approach referred to as “absolute-normalization”, which matches images in a time-series to an atmospherically corrected reference image using pseudo-invariant features and reduced major axis (RMA) regression. An advantage of “absolute-normalization” is that all images in the time-series are converted to units of surface reflectance while simultaneously being corrected for atmospheric effects. Of the two relative correction methods used for “absolute-normalization”, the first employed an automated ordination algorithm called multivariate alteration detection (MAD) to statistically locate pseudo-invariant pixels between each subject and reference image, while the second used analyst selected pseudo-invariant features (PIF) common to the entire image set. Overall, relative correction employed in the “absolute-normalization” context produced the most consistent temporal reflectance response, with the automated MAD algorithm performing equally as well as the handpicked PIFs. Although both relative methods performed nearly equally in terms of observed errors, several reasons emerged for preferring the MAD algorithm. The paper concludes by demonstrating how “absolute-normalization” improves (i.e., reduces scatter in) spectral reflectance trajectory models used for characterizing patterns of early forest succession.     

Arguments and Misunderstandings: Fuzzy Unification for Negotiating Agents

In this paper, we develop the notion of fuzzy unification and incorporate it into a novel fuzzy argumentation framework for extended logic programming. We make the following contributions: The argumentation framework is defined by a declarative bottom-up fixpoint semantics and an equivalent goal-directed top-down proofprocedure for extended logic programming. Our framework allows one to represent positive and explicitly negative knowledge, as well as uncertainty. Both concepts are used in agent communication languages such as KQML and FIPA ACL. One source of uncertainty in open systems stems from mismatches in parameter and predicate names and missing parameters. To this end, we conservatively extend classical unification and develop fuzzy unification based on normalised edit distance over trees.     

Liver and intestinal fatty acid-binding protein expression increases phospholipid content and alters phospholipid fatty acid composition in L-cell fibroblasts

Although fatty acid-binding proteins (FABP) differentially affect fatty acid uptake, nothing is known regarding their role(s) in determining cellular phospholipid levels and phospholipid fatty acid composition. The effects of liver (L)- and intestinal (I)-FABP expression on these parameters were determined using stably transfected L-cells. Expression of L- and I-FABP increased cellular total phospholipid mass (nmol/mg protein) 1.7- and 1.3-fold relative to controls, respectively. L-FABP expression increased the masses of choline glycerophospholipids (ChoGpl) 1.5-fold, phosphatidylserine (PtdSer) 5.6-fold, ethanolamine glycerophospholipids 1.4-fold, sphingomyelin 1.7-fold, and phosphatidylinositol 2.6-fold. In contrast, I-FABP expression only increased the masses of ChoGpl and PtdSer, 1.2- and 3.1-fold, respectively. Surprisingly, both L- and I-FABP expression increased ethanolamine plasmalogen mass 1.6- and 1.1-fold, respectively, while choline plasmalogen mass was increased 2.3- and 1.7-fold, respectively. The increase in phospholipid levels resulted in dramatic 48 and 33% decreases in the cholesterol-to-phospholipid ratio in L- and I-FABP expressing cells, respectively. L-FABP expression generally increased polyunsaturated fatty acids, primarily by increasing 20∶4n−6 and 22∶6n−3, while decreasing 18∶1n−9 and 16∶1n−7. I-FABP expression generally increased only 20∶4n−6 proportions. Hence, expression of both I- and L-FABP differentially affected phospholipid mass, class composition, and acyl chain composition. Although both proteins enhanced phospholipid synthesis, the effect of L-FABP was much greater, consistent with previous work suggesting that these two FABP differentially affect lipid metabolism.     

Recent advances in brain cholesterol dynamics: Transport, domains, and Alzheimer's disease

Major advances in understanding cholesterol dynamics and the role that cholesterol plays in vascular disease have recently been made. The brain is an organ that is highly enriched in cholesterol, but progress toward understanding brain cholesterol dynamics has been relatively limited. This review examines recent contributions to the understanding of brain cholesterol dynamics, focusing on extracellular and intracellular lipid carrier proteins, membrane cholesterol domains, and emerging evidence linking an association between cholesterol dynamics and Alzheimer's disease.     

Autonet: a high-speed, self-configuring local area network usingpoint-to-point links

Autonet is a self-configuring local area network composed of switches interconnected by 100 Mb/s, full-duplex, point-to-point links. The switches contain 12 ports that are internally connected by a full crossbar. Switches use cut-through to achieve a packet forwarding latency as low as 2 ms/switch. Any switch port can be cabled to any other switch port or to a host network controller. A processor in each switch monitors the network's physical configuration. A distributed algorithm running on the switch processor computes the routes packets are to follow and fills in the packet forwarding table in each switch. With Autonet, distinct paths through the set of network links can carry packets in parallel, allowing many pairs of hosts to communicate simultaneously at full link bandwidth. A 30-switch network with more than 100 hosts has been the service network for Digital's Systems Research Center since February 1990     

Contrast media-enhanced magnetic resonance imaging visualizes myocardial changes in the course of viral myocarditis

BACKGROUND: The course of tissue changes in acute myocarditis in humans is not well understood. Diagnostic tools currently available are unsatisfactory. We tested the hypothesis that inflammation is reflected by signal changes in contrast-enhanced magnetic resonance imaging (MRI). METHODS AND RESULTS: We assessed 44 consecutive patients with symptoms of acute myocarditis. Nineteen patients met the inclusion criteria revealing ECG changes, reduced myocardial function, elevated creatine kinase, positive troponin T, serological evidence for acute viral infection, exclusion of coronary heart disease, and positive antimyosin scintigraphy. We studied these patients on days 2, 7, 14, 28, and 84 after the onset of symptoms. We obtained ECG-triggered, T1-weighted images before and after application of 0.1 mmol/kg gadolinium. We measured the global relative signal enhancement of the left ventricular myocardium related to skeletal muscle and compared it with measurements in 18 volunteers. The global relative enhancement was higher in patients on days 2 (4.8+/-0.3 [mean+/-SE] versus 2.5+/-0.2; P<.0001); 7 (4.7+/-0.5, P<.0001); 14 (4.6+/-0.5, P<.0002); and 28 (3.9+/-0.4, P=.009) but not on day 84 (3.1+/-0.3; P=NS). On day 2, the enhancement was focal, whereas at later time points, the enhancement was diffuse. In patients with evidence of ongoing disease, the values remained elevated. CONCLUSIONS: Acute myocarditis evolves from a focal to a disseminated process during the first 2 weeks after onset of symptoms. Contrast media-enhanced MRI visualizes the localization, activity, and extent of inflammation and may serve as a powerful noninvasive diagnostic tool in acute myocarditis.     

Anterior-posterior patterning within the Caenorhabditis elegans endoderm

The endoderm of higher organisms is extensively patterned along the anterior/posterior axis. Although the endoderm (gut or E lineage) of the nematode Caenorhabditis elegans appears to be a simple uniform tube, cells in the anterior gut show several molecular and anatomical differences from cells in the posterior gut. In particular, the gut esterase ges-1 gene, which is normally expressed in all cells of the endoderm, is expressed only in the anterior-most gut cells when certain sequences in the ges-1 promoter are deleted. Using such a deleted ges-1 transgene as a biochemical marker of differentiation, we have investigated the basis of anterior-posterior gut patterning in C. elegans. Although homeotic genes are involved in endoderm patterning in other organisms, we show that anterior gut markers are expressed normally in C. elegans embryos lacking genes of the homeotic cluster. Although signalling from the mesoderm is involved in endoderm patterning in other organisms, we show that ablation of all non-gut blastomeres from the C. elegans embryo does not affect anterior gut marker expression; furthermore, ectopic guts produced by genetic transformation express anterior gut markers generally in the expected location and in the expected number of cells. We conclude that anterior gut fate requires no specific cell-cell contact but rather is produced autonomously within the E lineage. Cytochalasin D blocking experiments fully support this conclusion. Finally, the HMG protein POP-1, a downstream component of the Wnt signalling pathway, has recently been shown to be important in many anterior/posterior fate decisions during C. elegans embryogenesis (Lin, R., Hill, R. J. and Priess, J. R. (1998) Cell 92, 229-239). When RNA-mediated interference is used to eliminate pop-1 function from the embryo, gut is still produced but anterior gut marker expression is abolished. We suggest that the C. elegans endoderm is patterned by elements of the Wnt/pop-1 signalling pathway acting autonomously within the E lineage.     

Exploring the potential of problem-based learning in nurse education

Despite the increased attention that problem-based learning has received as an appropriate pedagogical technique for educating adults for professional practice, reports that evaluate the process are rare and usually relate to professions other than nursing. A study was undertaken in order to discover the graduates' own perceptions of a problem-based learning programme and its effectiveness in preparing them for the reality of their chosen profession. Twelve practising graduate nurses who had completed the programme were interviewed according to the ethnographic method. Three categories were identified from the data: 'and all of a sudden...', which describes the transition from PBL student to staff nurse; 'not an unthinking assistant', where the characteristics that the PBL graduates believe make them different from traditionally trained nurses are described; and 'the buck stops here', which describes the sense of personal responsibility that the graduates experience in terms of their learning and actions.     

Transduction of normal and malignant oral epithelium by particle bombardment

Considerable basic research, mostly in the past 20 years, has elicited greatly increased knowledge concerning the structure and function of cell adhesion molecules. Scores of individual adhesion molecules have been identified and categorized as to major structural features, ligands recognized, and pattern of expression. Recent attention has been focused on the interaction of cell adhesion molecules with intracellular components, and the role of cell adhesion molecules in mediating cell signal transduction. Ongoing efforts to develop specific pharmacological agonists and antagonists for adhesion molecules holds great promise in clinical medicine. Abciximab (Reopro), a monoclonal antibody inhibitor of the platelet integrin alpha IIb beta 3, is currently approved and available to improve vessel patency in patients undergoing angioplasty. Similar approaches to develop adhesion-based therapies to block angiogenesis, tumor progression, and/or metastasis are under development and hold promise for patients with cancer.