Torsion estimation of particle paths through porous media observed by in-situ time-resolved microtomography.

The torsion distribution of cell paths in two-phase flow of a cell suspension through a porous medium is an important quantity for chromatographic processes. It can be estimated from cell tracking in sequences of three-dimensional images of a suspension pumped through the medium, where the images are acquired by in-situ time-resolved microtomography using synchrotron radiation and inline phase contrast modus. This contribution presents a new method for estimating path torsion from discrete positions, where the estimation is based on an appropriate discretization of the differential-geometric formula of the torsion of a space curve. Investigations performed for an alcoholic suspension of silica gel particles pumped through a partially open polyurethane foam show that the shape of the inner surface of the foam has a considerable impact on the particle paths. It turns out that the variance of the torsion for slow particle moving close to the surface is a half order of magnitude smaller than that of fast particles, which underlines the importance of torsion for filter efficiency.

Human immunodeficiency virus infection in hemophiliac patients. A three-year prospective evaluation.

Thirty-seven heterosexual hemophiliac patients underwent prospective evaluation with clinical examinations, serologic studies for antibody to human immunodeficiency virus (HIV), and tests of immune function for an average of 37 months. At the time of entry into the study in 1982 to 1983, 18 subjects (49 percent) were already seropositive for HIV and 11 (30 percent) had persistent generalized lymphadenopathy. Seventy percent of the total population were clinically asymptomatic. In nine subjects, seroconversion occurred during the study such that 81 percent of the population was seropositive at the conclusion. During the same period, lymphadenopathy developed in six subjects, there was progression to AIDS-related complex (ARC) in four, and acquired immunodeficiency syndrome (AIDS) developed in one patient. Thus, at the end of the study, 54 percent were clinically asymptomatic, 32 percent had persistent lymphadenopathy, and 11 percent had ARC. Subjects who remained seronegative had received less factor concentrate than seropositive subjects, remained asymptomatic, and had normal results on tests of immune function. In those who had experienced seroconversion, there were decreased absolute numbers of CD4+ lymphocytes prior to seroconversion, and abnormalities of lymphocyte function developed after seroconversion. The development of persistent generalized lymphadenopathy was associated temporally with seroconversion. The presence of persistent generalized lymphadenopathy did not appear to be associated with an increased risk for AIDS in seropositive persons, since the condition of most hemophiliac patients with persistent generalized lymphadenopathy at the time of initial evaluation remained clinically and immunologically stable. In contrast to patients with persistent generalized lymphadenopathy, asymptomatic seropositive subjects had progressive abnormalities of lymphocyte function over time that were independent of the numbers of CD4+ cells in the peripheral blood.

Charge-Transfer Spectra and Bonding in Tetrahedral Mn(VI), Cr(V), and V(IV) and Mn(VII), Cr(VI), and V(V) Oxo Anions.

Density functional theory (DFT) calculations on the tetrahedral Mn(VI), Cr(V), and V(IV)(d(1)) oxo anions in their ground and lowest excited d-d and O --> M charge transfer (CT) states are reported and used to assign the electronic absorption spectra by reference to the spectra of the isoelectronic Mn(VII), Cr(VI), and V(V) (d(0)) and the Mn(V) and Cr(IV) (d(2)) anions. Calculated geometrical shifts along the totally symmetric metal-ligand vibration (alpha(1)) for electronic excitations are in agreement with data deduced from experimental vibronic fine structures, supporting the proposed assignments. Using a CT model including (as different from DFT) configuration interaction (CICT), it is shown that the CT excited states of MnO(4)(2)(-) at 17 000, 23 300, and 28 200 cm(-)(1) are due to d(2) (3)A(2)(2e(2)), (1)E(2e(2)), and (3)A(2)(2e(2)) final states combining with a single hole (L) on the ligand 1t(1) and 4t(2) orbitals, respectively. The higher 10Dq and smaller B values for the d(2)L(d(1)) states compared to those of the d(2) systems correlate with the shortening of the metal-ligand bond accompanying the removal of electrons from the antibonding d orbitals, leading to an increase in covalency and a change in the ordering of CT states for Cr(V) with (3)T(2)(2e(1)5t(2)(1))L (10Dq) at a higher energy than (1)E(2e(2))L (8B + 2C) as compared to Cr(IV) with nearly degenerate (3)T(2)(2e(1)5t(2)(1)) and (1)E(2e(2)) terms. This allows one to estimate the energy of the (3)A(2)(2e(2))L --> (1)E(2e(2))L transition from the CT (d(2)L) spectrum of Cr(V)(d(1)), which could not be observed for Cr(IV). From a comparison of calculated and experimental oscillator strengths and Huang-Rhys factors (S) for the lowest CT band in the V(V), Cr(VI), and Mn(VII) (d(0)) and the V(IV), Cr(V), and Mn(VI) (d(1)) oxo anions, it is shown that the increase in covalency from left to right in this series is accompanied by a reduction in band intensity and S for the progression in the alpha(1) vibration. An explanation of this result in terms of ionic contributions to the metal-ligand bond increasing from Mn(VI) to Cr(V) and V(IV) is proposed. Intensities of "d-d" transitions display the opposite trend; increasing covalency leads to stronger mixing between d --> d and CT excited states and thus an increase in intensity.

IgE and monoclonal antibody reactivities to the major shrimp allergen Pen a 1 (tropomyosin) and vertebrate tropomyosins.

Pen a 1, the major shrimp allergen from brown shrimp Penaeus aztecus has been identified as the muscle protein tropomyosin. To identify Pen a 1 IgE binding sites, the reactivities of Pen a 1-specific monoclonal antibodies (mAbs) and shrimp-allergic subjects' IgE to shrimp and homologous mammalian tropomyosins were analyzed. Pen a 1, purified by preparative SDS-PAGE and commercially obtained porcine, bovine and rabbit tropomyosin were cleaved by CNBr or digested by endoproteinases Lys-C, Glu-C, trypsin, Arg-C and chymotrypsin. Reactivities of Pen a 1-specific mAbs and IgE to the resulting peptides were analyzed by dot blot and immunoblotting. The dot blot analysis showed that mAbs and IgE antibodies did not react with any of the mammalian tropomyosins. The immunoblot analysis showed that all Pen a 1 digests bound IgE or mAbs. However, not all peptides in each digest possessed an IgE binding site. IgE binding intensity and frequency varied by subject and peptide digest. IgE and mAb reactivity patterns were similar but no mAb reproduced the IgE binding patterns indicating that subject' IgE bound some epitopes that were not recognized by the Pen a 1-specific mAbs. These studies suggest that IgE-binding epitopes are restricted to certain parts of the Pen a 1 molecule, Pen a 1 may have several similar epitopes, and that Pen a 1 epitopes do not appear to be located in the highly homologous parts of the tropomyosin molecule.

Acquired immune deficiency syndrome (AIDS). Medical challenge of the 80's.

Although the pathophysiology of acquired immune deficiency syndrome (AIDS) is not completely understood, we know a great deal about its epidemiology, risk factors, clinical manifestations, course, and immunologic features. Clinicians caring for high-risk individuals, particularly those in endemic urban areas, should remain alert for signs and symptoms of opportunistic infections or neoplasms associated with immunosuppression. It is clear that research on AIDS has increased exponentially; both physicians and patients should be encouraged by the fact that the apparent cause of this syndrome has been identified (human T-lymphotropic retrovirus HTLV-III) and that this breakthrough should result in effective therapeutic strategies in the near future.

[3D reconstruction of microcalcification clusters]. / Reconstruction 3D des foyers de microcalcifications.

PURPOSE: A characterization of the geometrical or morphological aspect of microcalcifications is not sufficient to confirm a diagnosis of cancer. On the other hand, it seems that the shape of the cluster is a pertinent and helpful criterion for diagnosis. The aim of our study is to work out a method for 3D reconstructions of clusters of microcalcifications. MATERIALS AND METHODS: After having tested different algorithms for extracting microcalcifications, we have developed a method of 3D reconstructions of the shape of the cluster from three radiographs. The technique, available using a standard mammography unit, consists of three principal steps RESULTS: The technique has been tested with two simple tridimensional phantoms and has given results with sufficient precision for possible clinical use. CONCLUSION: We plan now to apply the method in vivo with adaptation on a dedicated mammographic stereotactic unit with digital acquisition.

Fast construction of panoramic images for cystoscopic exploration.

Cystoscopy is used as a reference clinical examination in the detection and visualization of pathological bladder lesions. Evolution observation and analysis of these lesions is easier when panoramic images from internal bladder walls are used instead of video sequences. This work describes a fast and automatic mosaicing algorithm applied to cystoscopic video sequences, where perspective geometric transformations link successive image pairs. This mosaicing algorithm begins with a fast initialization of translation parameters computed by a cross-correlation of images, followed by an iterative optimization of transformation parameters. Finally, registered images are projected onto a global common coordinate system. A quantifying test protocol applied over a phantom yielded a mosaicing mean error lower than 4 pixels for a 1947 x 1187 pixels panoramic image. Qualitative evaluation of 10 panoramic images resulting from videos of clinical cystoscopies was performed. An analysis performed over translation values from these clinical sequences (in vivo) is used to modify the mosaicing algorithm to be able to do a dynamic selection of image pairs. Construction time of panoramic images takes some minutes. At last, algorithm limits are discussed.

Ground states, excited states, and metal-ligand bonding in rare earth hexachloro complexes: a DFT-based ligand field study.

Metal (4f)-ligand (Cl 3p) bonding in LnCl(6)(3-) (Ln = Ce to Yb) complexes has been studied on the basis of 4f-->4f and Cl,3p-->4f charge-transfer spectra and on the analysis of these spectra within the valence bond configuration interaction model to show that mixing of Cl 3p into the Ln 4f ligand field orbitals does not exceed 1%. Contrary to this, Kohn-Sham formalism of density functional theory using currently available approximations to the exchange-correlation functional tends to strongly overestimate 4f-3p covalency, yielding, for YbCl(6)(3-), a much larger mixing of Cl 3p-->4f charge transfer into the f(13) ionic ground-state wave function. Thus, ligand field density functional theory, which was recently developed and applied with success to complexes of 3d metals in our group, yields anomalously large ligand field splittings for Ln, the discrepancy with experiment increasing from left to the right of the Ln 4f series. It is shown that eliminating artificial ligand-to-metal charge transfer in Kohn-Sham calculations by a procedure described in this work leads to energies of 4f-4f transitions in good agreement with experiment. We recall an earlier concept of Ballhausen and Dahl which describes ligand field in terms of a pseudopotential and give a thorough analysis of the contributions to the ligand field from electrostatics (crystal field) and exchange (Pauli) repulsion. The close relation of the present results with those obtained using the first-principles based and electron density dependent effective embedding potential is pointed out along with implications for applications to other systems.

Pi* level tuning in a series of diimine ligands based on density functional theory: application to photonic devices.

Energy- and electron-transfer processes are very important for artificial photosynthesis and a variety of other applications. [(bpy)2Ru(PAP)Os(bpy)2]4+ and its oxidized form [(bpy)2Ru(PAP)Os(bpy)2]5+ perform efficient photoinduced energy- and electron-transfer processes, respectively (k(en) = 5.2 x 10(7) s(-1), k(el) = 7.2 x 10(6) s(-1)). The introduction of appropriate donor and acceptor units on the Ru2+ center can improve the lifetime of the excited state, resulting in a much longer and efficient storage of energy. Nonempirical (density functional) calculations and experimental data are used to predict the best donor and acceptor ligands for improving electron- and energy-transfer processes. Such a result can be extended to all polynuclear complexes where electronic coupling between the metal centers is very weak.

Acquired immune deficiency syndrome: an update and interpretation.

It is clear that there is a distinct new clinical entity of acquired immune deficiency which manifests itself by opportunistic infections and KS. It occurs in selected groups of the population but with an ever increasing spectrum. The clinical presentation is extremely varied and the spectrum of disease runs a wide gamut. Health professionals should be aware that there is a large pool of individuals at risk for AIDS; also AIDS may manifest itself in the limited forms with mild initial signs which continue for months before serious disease becomes apparent. There is at present no specific diagnostic laboratory test to identify these patients or those at greatest risk. Present evidence indicates that once life-threatening opportunistic infections or KS have become obvious, although the disease process may wax and wane, most patients follow an inexorable downhill course. That process has not been reversed by presently applied therapies. In view of the failure of conventional and experimental therapies, the only treatment appears to be prevention of disease by avoiding risk factors. With the ever increasing number of possible risk factors identified, such avoidance becomes continually more difficult. The most pressing problem is to delineate the pathogenesis of AIDS. Until then optimal preventive and therapeutic interventions can not be instituted fully. There are a number of major unanswered questions, foremost of which is the nature of the transmittable agent. Moreover, it is not entirely clear who is susceptible to this agent. With the vast numbers at risk and growing numbers of AIDS cases, it is imperative to uncover the initial events responsible for this syndrome. From the public health point of view, it is also crucial to determine whether those individuals in the high risk groups which exhibit immunological abnormalities will, given a long enough latent period, eventually progress to AIDS/KS or whether the majority are merely a forme fruste of AIDS. Because of the major public health impact of AIDS, all physicians should be aware of and knowledgeable about this new disease process.

The natural history of shrimp hypersensitivity.

Sera collected sequentially during a 24-month interval from 11 individuals with shrimp hypersensitivity and 10 nonhypersensitive control subjects were evaluated for shrimp-specific IgE, IgG, IgM, and IgA reactivity. Shrimp-hypersensitive subjects underwent double-blind, placebo-controlled shrimp challenges; seven exhibited positive challenges, and four subjects reported the subjective symptom of oropharyngeal pruritus. Shrimp-specific IgE levels in all subjects were relatively constant during the 24 months of this study and not affected by shrimp challenge, although some fluctuation in the shrimp-specific IgG, IgM, and IgA reactivity were noted, apparently unrelated to shrimp challenge. Shrimp-specific IgE and IgG, but not IgM and IgA, were significantly higher in the group with shrimp hypersensitivity as compared to the control subjects. Moreover, the challenge-positive subjects had higher levels of both shrimp-specific IgE and IgG than subjects reporting pruritus. The levels of shrimp-specific IgG correlated directly with shrimp-specific IgE reactivity. These studies indicate that serum levels of shrimp-specific IgE are significantly elevated in shrimp-hypersensitive subjects who exhibit positive food challenges, and these baseline levels did not appear to be altered long term by isolated shrimp challenge. Furthermore, baseline shrimp-specific antibody (IgG, IgM, and IgA) levels noted in normal subjects were not markedly affected by frequent ingestion of shrimp.

The relationships among shrimp-specific IgG subclass antibodies and immediate adverse reactions to shrimp challenge.

High levels of shrimp-specific IgE, in association with a positive prick test, are not always predictive of a positive, immediate response to double-blind, placebo-controlled, food challenge (DBPCFC) with shrimp. The observation that shrimp-sensitive individuals in general have increased levels of circulating shrimp-specific IgG is of interest because antigen/allergen-specific IgG subclasses have been associated with adverse reactions to foods. Therefore, this current study measured shrimp-specific IgG subclass and IgE antibodies in 31 individuals with histories of immediate, adverse reactions to shrimp immediately before DBPCFC and 20 shrimp-tolerant subjects. Individuals with a history of shrimp sensitivity had significantly raised shrimp-specific IgG2 and IgG4 compared to shrimp-tolerant individuals. Challenge-positive subjects were distinguished from subjects with negative or equivocal responses by an increased IgG2 (p less than or equal to 0.001). Specific IgG4 was not raised (p less than or equal to 0.065). These studies indicate that some shrimp-specific IgG subclass levels are increased in shrimp-sensitive subjects. However, none of the subclass responses were significantly predictive of a positive response to DBPCFC and therefore were not diagnostic of shrimp intolerance.

Antigenic analysis (IgE and monoclonal antibodies) of the major shrimp allergen Pen a 1 (Tropomyosin) from Penaeus aztecus.

Pen a 1, the major shrimp allergen from the brown shrimp Penaeus aztecus was purified by preparative SDS-PAGE. Peptides were generated from Pen a 1 by CNBr cleavage and endoproteinase (Lys-C, Glu-C, trypsin, alkaline protease, Arg-C, chymotrypsin) digestion. The molecular weights of the resulting CNBr cleavage and enzymatic digestion products, separated by peptide SDS-PAGE, ranged from 1.5 to 20 kD. Following SDS-PAGE and semidry blotting, the analysis of monoclonal antibody (mAb) and subjects' IgE reactivities demonstrated that with the exception of alkaline protease, all cleavage procedures yielded IgE-binding peptides. However, since not all peptides of every digest bind IgE, it appears that IgE-binding epitopes are restricted to certain parts of the Pen a 1 molecule. mAbs bound to CNBr, Lys-C, trypsin, Glu-C and Arg-C peptides. Since mAbs reacted to several peptides from the same digest, Pen a 1 may have several similar epitopes. The comparison of IgE and mAb reactivities demonstrated similar but not identical binding patterns.

Seroconversion to human immunodeficiency virus (HIV) in hemophiliacs. Relation to lymphadenopathy.

The authors studied the natural history of human immunodeficiency virus (HIV) exposure in 187 hemophiliacs followed for an average of 45 months. Overall, 55 percent developed antibody specific for HIV and 21 percent developed persistent generalized lymphadenopathy. Most patients seroconverted sometime between early 1982 and the end of 1984. Four patients developed acquired immune deficiency syndrome (AIDS) and four seropositive patients developed idiopathic thrombocytopenia (ITP). One of the four patients who developed AIDS and three of the four with ITP had preexisting lymphadenopathy. None of the 10 patients with lymphadenopathy or the 20 asymptomatic patients was seropositive for human T-lymphotropic virus, type I. Although seropositivity and lymphadenopathy have been found in many of the authors' patients, few have developed clinical disease that can be related to HIV infection.

The modelling of nucleophilic and electrophilic additions to organometallic complexes using molecular graphics techniques.

A new formalism has been developed in order to evaluate intermolecular interaction energies for inorganic and organometallic complexes in the framework of the extended Hückel method. In order to provide the shortest possible response time on an interactive computer graphics facility, this model should require the minimum amount of computer time, which explains why approximate procedures are used to evaluate electrostatic, charge transfer and exchange repulsion components. When applying this model to typical examples of electrophilic addition reactions to organometallic complexes, it is found that it is essential to take account of charge transfer interactions, the electrostatic component alone being not sufficient, even qualitatively, for a proper description of the reaction mechanism. The results, presented as color-coded dot molecular surfaces, show a very good agreement with experiment as to the site of attack, namely (i) on metal for the electrophilic attack on Fe(cp)2, Fe(CO)5 and X(cp)(CO)2, X = Co, Rh; (ii) on the cp ligand for the nucleophilic attack on Co(cp)2+ and Rh(cp)2+; (iii) on bz for the nucleophilic attack on Fe(cp)(bz)+. Finally, modellizations of the nucleophilic attack on a coordinated olefin and of the relation between structure and acidic properties of zeolites are presented and discussed.