An inviscid model for calculating the roll up of wing-generated, vortical wakes has been developed. The model is shown to be an efficient means of studying the dynamics of the wake in the region from Just behind the wing to the previscous-dissipation far field. The model is based on a modified discrete-vortex method that includes the near-wing effects of the wing-bound vorticity and the fact that the wake originates at the wing, rather than at minus infinity. Three-dimensional wakes are produced by connecting the two dimensional wake contours at successive Trefftz planes. The inclusion of the near-wing effects is shown to have a relatively large influence on the wake's dynamics and final disposition The inclusion of rotational cores is shown to aid in smoothing the wake roll up, but appears to have little effect on the wake's final dispersion radii.

Xenotransplantation of porcine tissue to human recipients promises to alleviate the organ shortage. Human antibody-mediated and cell-mediated immune responses against porcine grafts, however, represent barriers to successful xenotransplantation. We compared neonatal porcine islet cells (NPICs) and neonatal porcine splenocytes for the ability to stimulate proliferation of human peripheral blood lymphocytes (PBLs), and for their susceptibility to human natural killer (NK) and cytotoxic T-lymphocyte (CTL)-mediated lysis. Human peripheral blood CD4+ lymphocytes showed strong proliferation in response to NPICs, likely because of occasional swine leukocyte antigen (SLA) class II+ cells in the NPIC preparations. In contrast, human peripheral blood CD8+ lymphocytes did not proliferate in response to NPICs, although they showed clear responses to both porcine splenocytes and endothelial cells. Both human CTL-raised-against-porcine splenocytes and endogenous NK cells lysed porcine splenocytes, but the same cells showed little or no lytic activity against NPICs. Lysis of porcine splenocyte targets was completely abrogated by pretreatment of the human NK or CTL populations with concana-mycin A, suggesting a perforin-dependent effector mechanism. Pretreatment of the NPIC targets with proinflammatory porcine cytokines to upregulate SLA class I expression failed to enhance human CTL-mediated lysis. However, lysis of NPICs by human CTLs could be elicited when a lectin was added to form stable effector:target cell conjugates. It appears that NPICs do not express sufficiently high levels of co-stimulatory and/or adhesion molecules to either activate human CD8+ T-cells or to be effective targets for activated human CTLs. These data suggest that NPICs may not be destroyed by NK- or CTL-mediated lytic mechanisms after transplantation into humans.

In vivo, MHC class I-restricted injury of allogeneic tissue or cells infected by intracellular pathogens occurs in the absence of classical cytolytic effector mechanisms and Ab. Modulation of the target cell adhesion to matrix may be an additional mechanism used to injure vascular or epithelial cells in inflammation. We studied the mechanisms of human umbilical vein endothelial cell (EC) detachment from matrix-coated plastic following contact by concanamycin A-treated lymphocytes as an in vitro model of perforin-independent modulation of EC basement membrane adhesion. Human PBL were depleted of monocytes, stimulated, then added to an EC monolayer plated on either fibronectin or type I collagen matrices. Activated, but not resting, PBL induced progressive EC detachment from the underlying matrix. Injury of the EC monolayer required direct cell contact with the activated lymphocytes because no detachment was seen when the PBL were placed above a Transwell membrane. Moreover plasma membranes prepared from activated but not resting PBL induced EC detachment. Adherent EC stimulated with activated PBL did not show evidence of apoptosis using TUNEL and annexin V staining at time points before EC detachment was observed. Finally, neither the matrix metalloproteinase inhibitors o-phenanthroline and BB-94 nor aprotinin blocked EC detachment. However, activation of EC beta1 integrin using mAb TS2/16 or Mg2+ decreased EC detachment. These data indicate that cell-cell contact between activated PBL and EC reduces adhesion of EC to the underlying matrix, at least in part by inducing changes in the affinity of the endothelial beta 1 integrin.

287 Transient focal loosening of an endothelial cell's (EC) basement membrane attachment may be an important event in endothelial invasion in acute rejection (endothelialitis). We studied the mechanisms of endothelial cell detachment from matrix-coated plastic following contact by lymphocytes as an in vitro model of modulation of EC basement membrane adhesion. 3H-methyl thymidine labeled human umbilical vein endothelial cells were plated on either fibronectin or type I collagen matrices. Human PBL were depleted of monocytes, stimulated with PHA, then added to the EC monolayer. Specifically detached EC were quantitated as the fraction of the total less spontaneously detached EC. Co-culture of lectin-activated, but not resting PBL, with monolayers of EC induced progressive endothelial cell detachment from the underlying matrix. Injury of the EC monolayer required direct cell contact with the activated lymphocytes since no detachment was seen when the PBL were placed above a transwell membrane. Moreover plasma membranes prepared from activated but not resting PBL induced EC detachment. Neither inhibition of perforin function using concanamycin A, nor fas-ligand or TNF/LT signalling using blocking antibodies abrogated EC detachment. Adherent EC stimulated with activated PBL did not show evidence of apoptosis using TUNEL and annexin V staining at timepoints before EC detachment was observed. Neither the matrix metalloproteinase inhibitors o-phenanthroline or BB-94, nor aprotinin blocked EC detachment. EC detachment was largely inhibited when the EC β1 integrin was frozen in the high-affinity conformation using mAb or Mg+2. Activation of endothelial cell β1 integrin inhibited transendothelial migration of lymphocytes in vitro. Thus contact of activated PBL with the endothelial cell induces changes in the EC attachment to the underlying matrix which involves changes in the EC β1 integrin conformation. Decreased endothelial β1 integrin affinity for matrix may be a central event in lymphocyte-mediated vascular injury and leukocyte migration into sites of the mechanisms of inflammation.

Kraemer, W. J. FACSM; Triplett, N. T.; Bauer, J.; Koziris, L. P.; Fry, A. C.; Lynch, J. M.; Knuttgen, H. G. FACSM; Nelson, R. C. FACSM Author Information

To the Editor.— The recent article by Khoury et al1provides death certificate data that show a dramatic increase in the reported rates of sudden infant death syndrome (SIDS) for both blacks and whites, beginning in the 1960s. The authors postulate that all or part of this reported increase may be due to changes in theInternational Classification of Diseases, Adaptedcoding schema and/or artifacts of registration. Two population-based studies of SIDS have been conducted by investigators at the Mayo Clinic, Rochester, Minn (R.C.N., unpublished data, January 1966 to December 1981 ).2In both studies, for all cases of infant neonatal and postneonatal mortality, death certificates were linked to medical records and autopsy protocols (the overall autopsy rate was 83%). Case ascertainment was complete and diagnoses were verified by exclusion. The annual incidence rate of SIDS for Olmsted County, Minnesota, for the time frame 1946 to 1965 was 1.2

References 1 Schlichting, H., Boundary Layer Theory, 6th Ed., McGraw-Hill Book Co., New York, 1968, pp. 369-370. Waston, E. J., A Solution of the Navier-Stokes Equation Illustrating the Response of the Laminar Boundary Layer to a Given Change in the External Stream Velocity, Quarterly Journal of Mechanics and Applied Mathematics, Vol. 11, April 1958, pp. 302325. Liu, C. Y., Note on the Unsteady Suction Solutions to the Boundary Layer Equations, Proceedings of the Astronautical Society of the Republic of China, Vol. 4, Dec. 1971, pp. 96-99. Liu, C. Y., Asymptotic Suction Flow of Power Law Fluid, Journal of Aircraft, Vol. 7, July 1973, pp. 135-136. Zierep, J., Das Rayleigh-Stokes-Problem fur die Ecke, Acta Mechanica, Vol. 34, July 1979, pp. 161-165. Liu, C. Y. and Ismail, K.A.R., Asymptotic Solution of Free Convection Near a Corner of Two Vertical Porous Plates Embedded in Porous Medium, Heat and Mass Transfer, Vol. 7, Nov. -Dec. 1980, pp. 457-463.

The band structures for an excess electron and an excess hole in the metal-free phthalocyanine crystal were calculated in the tight binding approximation. The LCAO wave functions for the cation and anion radicals were calculated by the unrestricted SCF method. The Goeppert-Mayer-Sklar type potential was used as an average potential. Simplified formulas were derived for the calculation of the resonance penetration integrals between carbon and nitrogen atoms. The calculated band width was of the order of 10-2 ev for an electron and 10-3 ev for a hole. The calculation predicted the large anisotropy of the mobility tensor of an excess electron.

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTMinority Carrier Trapping and Dye Sensitization1a,bR. C. NelsonCite this: J. Phys. Chem. 1965, 69, 3, 714–718Publication Date (Print):March 1, 1965Publication History Published online1 May 2002Published inissue 1 March 1965https://doi.org/10.1021/j100887a002Request reuse permissionsArticle Views243Altmetric-Citations23LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (609 KB) Get e-Alerts

The work function, or ionization energy, for eight solid dyes has been measured. In each case it was found that this energy was equal to the sum of the electron affinity of the dye, as previously measured by the writer, and the energy required to produce a charge carrier in the solid dye. The data confirm the point of view that electron-transfer processes in dye sensitization are energetically possible.

Get PDF Email Share Share with Facebook Tweet This Post on reddit Share with LinkedIn Add to CiteULike Add to Mendeley Add to BibSonomy Get Citation Copy Citation Text R. C. Nelson, "Sensitization of Photoconductivity in Glass by Dyes*," J. Opt. Soc. Am. 50, 1029-1029 (1960) Export Citation BibTex Endnote (RIS) HTML Plain Text Citation alert Save article

The effect of density of sensitizer molecules adsorbed on a cadmium sulfide surface on the efficiency of sensitization by them has been studied for malachite green, pinacyanole, erythrosin, and 3,3′ diethylthiacarbocyanine. The losses in the case of the first two are drastic and can be accounted for directly in terms of the properties of the solid dyes. The detailed process of electron transfer from a dye molecule or aggregate to a crystal substrate is considered briefly. It is concluded that there should in general be a loss of efficiency in passing from the state in which molecules are adsorbed singly and broadside, to that in which they are adsorbed as a close-packed aggregate.

The problems arising in the use of the lead sulfide cell for direct recording of spectra have been investigated using a spectrograph designed especially for this work. The inhomogeneity of the surface of these cells, as compared with photo-multipliers, makes for important differences in their use. Using a sharply tuned amplifier, the sensitivity of the cells at room temperature is adequate to permit a resolving power of the order of 40,000 at 1.4μ. Wave-lengths may be determined to about 0.1A, using overlapping orders.