No abstract

The transport of colloids in geochemically heterogeneous porous media is investigated. A model describing the transport and deposition of colloids onto heterogeneously charged mineral grains is developed and applied to column experiments. The model characterizes mineral grain surfaces according to a patchwise charge distribution, with individual patches being either favorable or unfavorable for deposition depending on their electrostatic charge. Separate rate expressions are used in the model to depict favorable and unfavorable deposition kinetics. Declining deposition kinetics that are produced when previously retained particles block subsequent attachment of colloids are quantified in the model by dynamic blocking functions. Column experiments involving colloid transport in geochemically heterogeneous porous media were performed using silica colloids and quartz sand. Surface charge heterogeneity was introduced into the porous medium by coating a fraction of the quartz sand with iron oxyhydroxide. Theoretical breakthrough curves generated by the model using experimentally determined parameters compared quite well to the experimental results, demonstrating the importance of geochemically heterogeneous surfaces in determining the transport behavior of colloidal particles in heterogeneous aquatic environments.

This paper examines an exchange economy with heterogeneous indivisible objects that can be substitutable or complementary. We show that a competitive equilibrium exists in such economies, provided that all the objects can be partitioned into two groups, and from the viewpoint of each agent, objects in the same group are substitutes and objects across the two groups are complements. This condition generalizes the well-known Kelso-Crawford gross substitutes condition and is called gross substitutes and complements. We also provide practical and typical examples from which substitutes and complements are both jointly observed. Copyright The Econometric Society 2006.

A prospective study of hemostatic abnormalities in 108 cancer patients was undertken at an oncology clinic in a university teaching hospital. Tests included Quick prothrombin time, activated partial thromboplastin time, thrombin time, platelet count, modified Ivy bleeding time, fibrinogen, fibrin degradation products (FDP), euglobulin lysis time, protamine sulfate test, and factor V, VII, VIII and X assays. Ninety-eight per cent of the patients had one or more abnormal coagulation tests. The commonest abnormalities were elevated fibrin degradation products and prolonged thrombin time. Thrombocytosis occurred in 57% of patients, hyperfibrinogenemia in 46%, thrombocytopenia in 11%, and non had hypofibrinogenmia. It is suggested that platelet count, fibrinogen concentration, and serum FDP assay are the most useful tests in assessing the hemostatic abnormalities in cancer patients, although thrombin time, factor V assay, and bleeding time may also be helpful. The peripheral blood smears of 53 patients were reviewed, and only one showed microangiopathic hemolytic anemia. The data illustrate that subclinical coagulopathy is relatively frequent in patients with malignancy.

Sinonasal natural killer (NK)/T-cell lymphomas are common in Asia and areas of South and Central America but are rarely seen in the United States, where they have not been as well characterized. Fifteen cases diagnosed in Southern California were studied with respect to histologic features, immunophenotype, Epstein-Barr virus EBER in-situ hybridization (EBV EBER-ISH), and T-cell receptor gamma chain (TCR-gamma) gene rearrangement. Although ethnic background was available for only seven patients, six were of Asian or Hispanic descent with only one non-Hispanic white known. Twelve presented as sinonasal lesions, but three were limited to the oropharynx. Most cases (11 of 15) demonstrated both necrosis and an angiodestructive pattern. All cases demonstrated cytoplasmic CD3 positivity (15 of 15), and were positive for both TIA-1 and granzyme B (14 of 14). Perforin was positive in 5 of 14. CD56 was expressed in 10 of 15 and CD8 in 3 of 15. EBV EBER-ISH was positive in 14 of 14 and TCR-gamma gene rearrangement was detected in 1 of 14 cases. None (0 of 14) were positive for CD16 or CD57. Although CD16-positive histiocytes were abundant, double-label EBER-ISH/IHC failed to identify CD16 expression on EBV-positive tumor cells. Three cases with pleomorphic large cell morphology showed focal CD30 positivity, raising the differential diagnosis of anaplastic large cell lymphoma, but all were ALK-1-negative and otherwise similar to the other cases of NK/T-cell lymphoma. Sinonasal NK/T-cell lymphomas in the United States most often occur in ethnic groups from areas of reported high frequency (Asia, Central and South America), although less commonly than in endemic populations, and are otherwise similar phenotypically. A combined approach, including immunohistochemistry, EBV EBER-ISH, and TCR gene rearrangement studies, is most helpful to arrive at the correct diagnosis.