Thermal Marangoni trapping driven by laser absorption in evaporating droplets for particle deposition.

Controlling the deposition of particles is of great importance in many applications. In this work, we study particle deposition driven by Marangoni flows, triggered by laser absorption inside an evaporating droplet. When the laser is turned on, thermal gradients are generated and produce a toroidal Marangoni flow that concentrates the particles around the laser beam and ultimately controls the final deposition. We experimentally characterize the radius of the Marangoni flows as a function of the laser parameters. Counter-intuitively, the radius of the Marangoni region appears to remain constant and is not proportional to the thickness of the drop which decreases due to evaporation. We develop a model to predict the size of the Marangoni region that combines evaporative flows and laser-induced Marangoni flows. The experimental data are in good agreement with the predictions, allowing us to estimate the particle overconcentration factor resulting from the laser heating effects. The addition of surfactants to the solution allows the coupling of solutal Marangoni flows with thermal ones to achieve a final micron-scale deposit located at the laser spot. These results pave the way for new methods with high tunability provided by spatio-temporal light control for surface patterning applications.

Conical Interfaces between Two Immiscible Fluids Induced by an Optical Laser Beam.

We demonstrate the existence of conical interface deformations induced by a laser beam that are similar to Taylor cones in the electrical regime. We show that the cone morphology can be manipulated by fluid and laser parameters. A theory is proposed to quantitatively describe these dependences in good agreement with experimental data obtained for different fluid systems with low interfacial tensions. Counterintuitively, the cone angle is proved to be independent of the refractive index contrast at leading order. These results open a new optofluidic route towards optical spraying technology-an analogue of electrospraying-and more generally for the optical shaping of interfaces.

Excitation of fountain and entrainment instabilities at the interface between two viscous fluids using a beam of laser light.

We report on two instabilities, called viscous fountain and viscous entrainment, triggered at the interface between two liquids by the action of bulk flows driven by a laser beam. These streaming flows are due to light scattering losses in turbid liquids, and can be directed either toward or forward the interface. We experimentally and numerically investigate these interface instabilities and show that the height and curvature of the interface deformation at the threshold and the jet radius after interface destabilization mainly depend on the waist of the laser beam. Analogies and differences between these two instabilities are characterized.

Acoustical spring effect in a compliant cavity.

We report on the first dynamic study of acoustical spring effect in a compliant cavity formed between a spherical ultrasonic transducer immersed in water and the free liquid surface located at its focus. As its optical analog, this effect is due to the mutual feedback between the cavity length L and the large acoustical power stored inside the cavity, here through acoustic radiation pressure. We use surface waves to investigate the acoustical spring effect. The amplitude of surface waves above the cavity is observed to vary with the slope of variation of the L -dependent acoustic radiation pressure exerted on the liquid surface, i.e. with the acoustic spring stiffness. The observed simultaneous back-scattering of these surface waves demonstrates that the surface response to the cavity length variations results mainly in an added stiffness, i.e., in an increase of the real part of the surface impedance above the cavity. Finally, when the liquid surface is located out of the focal plane, spontaneous surface oscillations are reproducibly observed, which may be due to a parametric instability.

Universal morphologies of fluid interfaces deformed by the radiation pressure of acoustic or electromagnetic waves.

We unveil the generation of universal morphologies of fluid interfaces by radiation pressure regardless of the nature of the wave, whether acoustic or optical. Experimental observations reveal interface deformations endowed with steplike features that are shown to result from the interplay between the wave propagation and the shape of the interface. The results are supported by numerical simulations and a quantitative interpretation based on the waveguiding properties of the field is provided.

Optohydrodynamics of soft fluid interfaces: optical and viscous nonlinear effects.

Recent experimental developments showed that the use of the radiation pressure, induced by a continuous laser wave, to control fluid-fluid interface deformations at the microscale, represents a very promising alternative to electric or magnetic actuation. In this article, we solve numerically the dynamics and steady state of the fluid interface under the effects of buoyancy, capillarity, optical radiation pressure and viscous stress. A precise quantitative validation is shown by comparison with experimental data. New results due to the nonlinear dependence of the optical pressure on the angle of incidence are presented, showing different morphologies of the deformed interface going from needle-like to finger-like shapes, depending on the refractive index contrast. In the transient regime, we show that the viscosity ratio influences the time taken for the deformation to reach steady state.

Bridging dielectric fluids by light: a ray optics approach.

Rayleigh-Plateau instability is known to impose a stability limit for the length of a liquid bridge in weightless conditions. This fundamental limit may be exceeded by using a light field to form and stabilize dielectric fluid bridges (A. Casner, J.P. Delville, Europhys. Lett. 65, 337 (2004)). Using both new experimental data as well as a new theoretical approach, we show that both the size and the stability of such light-sustained dielectric bridge can be qualitatively explained. We present a ray optics model that encompasses the competition between surface tension effects and optical radiation pressure arising from total internal reflection inside the bridge. A critical power below which a liquid bridge can no longer be sustained by light is predicted and confirmed experimentally. The observed power dependence of the bridge diameter also agrees with the proposed stabilization mechanism.

Biclonal low grade B-cell lymphoma confirmed by both flow cytometry and karyotypic analysis, in spite of a normal kappa/lambda Ig light chain ratio.

Composite low grade lymphoma with two subpopulations in a same site is uncommon. We herewith report the case of an 80-year-old woman who presented with isolated bilateral dacryoadenomegaly. Pathological examination of an incisional biopsy of her right lacrimal gland was consistent with a marginal zone lymphoma. Flow cytometry immunophenotyping showed two distinct clonal B-cell populations expressing sIg D lambda or sIg M kappa restriction in the lacrimal gland, blood, and bone marrow. Both B-cells populations were sorted from peripheral blood for molecular biology investigations and comparison with molecular data performed on tumor and bone marrow cells. IgH PCR performed on purified blood populations disclosed two monoclonal peaks: 98 bp-sized peak in the sIg M kappa and a 107 bp in the sIg D lambda clones, respectively. The lacrimal gland tumor expressed mainly sIg M kappa population, and showed a major 98 bp-sized peak coexisting with a very minor 107 bp peak. Cytogenetic studies showed a 46, XX,del (7) (q22q32) karyotype. Bone marrow examination at diagnosis revealed the same B-cell clones distribution than the one observed in blood with a dominant sIg D lambda population, a Genescan profile showing a major peak of 107 bp and a minor peak of 98 bp. Chromosomal analysis disclosed a 46,XX,del (10) (?p14) karyotype without detectable 7q deletion. To our knowledge, this observation represents the first reported case of biclonal low grade lymphoma hidden behind a normal classical kappa/lambda Ig light chain ratio in blood, but clearly demonstrated by the combination of three ancillary techniques (flow cytometry both analytical and cell sorting, molecular biology, and cytogenetics) and analysis of different tissues (i.e., in this case, lacrimal gland biopsy, blood, and bone marrow).

Smart control of monodisperse Stöber silica particles: effect of reactant addition rate on growth process.

Control over the synthesis of monodisperse silica particles up to mesoscopic scale is generally made difficult due to intrinsic limitation to submicrometric dimensions and secondary nucleation in seeded experiments. To investigate this issue and overcome these difficulties, we have implemented single step processing by quantifying the effects of the progressive addition of a diluted tetraethyl orthosilicate solution in ethanol on the size and monodispersity of silica particles. Contrary to particles grown in seeded polymerization, monodisperse particles with size up to 2 microm were synthesized. Moreover, the particles exhibit a final diameter (d(f)), which varies with V(-1/3) over more than 2 orders of magnitude in rate of addition (V). On the basis of a kinetic study in the presence of addition showing that particle growth is limited by the diffusion of monomer species, we developed a diffusion-limited growth model to theoretically explain the observed d(f)(V) behavior and quantitatively retrieve the measured amplitude and exponent. Using a single parameter procedure, we can therefore predict and generate in the room temperature range, monodisperse particles of a targeted size by simply adjusting the rate of addition.

Instability of a lamellar phase under shear flow: formation of multilamellar vesicles.

The formation of closed-compact multilamellar vesicles (referred to in the literature as the "onion texture") obtained upon shearing lamellar phases is studied using small-angle light scattering and cross-polarized microscopy. By varying the shear rate gamma;, the gap cell D, and the smectic distance d, we show that: (i) the formation of this structure occurs homogeneously in the cell at a well-defined wave vector q(i), via a strain-controlled process, and (ii) the value of q(i) varies as (dgamma;/D)(1/3). These results strongly suggest that formation of multilamellar vesicles may be monitored by an undulation (buckling) instability of the membranes, as expected from theory.

[The immunology-hematology-transfusion department]. / Le Service d'Immunologie-Hématologie-Transfusion.

New immunotherapies derived from biotechnology offer fascinating perspectives in different fields of medicine including anti-infectious vaccines, cancer, organ transplantation and autoimmune diseases. In this paper, we illustrate how the Department of Immunology can contribute to the development of these new treatments within a academic hospital such as the Erasme Hospital at the Université Libre de Bruxelles.

Gas spreading on a heated wall wetted by liquid.

This study deals with a simple pure fluid whose temperature is slightly below its critical temperature and whose density is nearly critical, so that the gas and liquid phases coexist. Under equilibrium conditions, such a liquid completely wets the container wall and the gas phase is always separated from the solid by a wetting film. We report a striking change in the shape of the gas-liquid interface influenced by heating under weightlessness where the gas phase spreads over a hot solid surface showing an apparent contact angle larger than 90 degrees. We show that the two-phase fluid is very sensitive to the differential vapor recoil force and give an explanation that uses this nonequilibrium effect. We also show how these experiments help to understand the boiling crisis, an important technological problem in high-power boiling heat exchange.

Giant deformations of a liquid-liquid interface induced by the optical radiation pressure.

Because of the small momentum of photons, very intense fields are generally required to bend a liquid interface with the optical radiation pressure. We explore this issue in a near-critical phase-separated liquid mixture to vary continuously the meniscus softness by tuning the temperature. Low power continuous laser waves become sufficient to induce huge stationary bulges. Using the beam size to build an "optical" Bond number, Bo, we investigate the crossover from low to large Bo. The whole set of data collapses onto a single master curve which illustrates the universality of the phenomenon.

Performances of holographic gratings monitored by laser-induced phase separation in liquid mixtures.

We theoretically describe and experimentally explore the kinetics of holographic grating formation resulting from different laser-induced phase separation mechanisms. Our method makes use of two interfering c.w. laser waves to quench binary mixtures in composition, and to optically trap the nucleated domains on the fringes. Essentially, two different processes can lead to these variations in concentration: electrostriction and thermodiffusion. The former originates from induced dipolar couplings in a field gradient; as photopolymerization, this is a local process which is essentially sensitive to the q=q(0) Fourier mode forced by the fringe modulation. The latter corresponds to a variation in composition driven by a small thermal gradient; as solvent evaporation and thermal heating techniques, it is nonlocal and behaves as 1/q(2) because of its dissipative origin. By making experiments in both cases, we show that this q dependence on excitation has a strong influence on the performance of holographic gratings. While in the first case reflectivity saturates because the phase transition is confined by the fringes which behave as separated optical boxes with "soft walls" which calibrate the droplet size, blurring is expected for fringe-trapped domains induced by a nonlocal phase transition because the transition is governed by the Gaussian shape of the pump beams, and nucleated domains can reach a much larger size than the fringe spacing. The good agreement observed with our general model clearly illustrates how to make the difference between local and nonlocal excitations, and offers a first step towards a unified description of holographic grating formation monitored by phase transitions.

Occurrence of the Asn45Ser mutation in the GPIX gene in a Belgian patient with Bernard Soulier syndrome.

Bernard Soulier Syndrome (BSS) is a rare inherited bleeding disorder caused by a defect in the glycoprotein (GP)Ib/IX/V complex. A patient with a bleeding problem was diagnosed as having BSS based on the prolonged bleeding time, the absence of ristocetin induced platelet aggregations, thrombocytopenia and the presence of giant platelets. Analysis of the platelets of the propositus, a 39-year-old Belgian female, by flow cytometry revealed a decreased expression of the GPIb/IX polypeptides. Western blotting confirmed these results and showed moreover that there was a decreased disulfide bridge formation between GPIb alpha and GPIb beta. After sequence analysis of the GPIb alpha, GPIb beta and GPIX genes, only a mutation in the GPIX gene at position 1826 (A-->G) was identified, changing Asn45-->Ser. Restriction analysis with Fnu4H1 demonstrated that the patient was homozygous for this mutation. As this Asn45-->Ser mutation in the GPIX gene was already found in four unrelated families, i.e. in a British, Austrian, Swedish and Finnish one, the occurrence of this mutation in a Belgian patient supports the hypothesis of Koskela et al. (1999) that the Asn45Ser mutation in GPIX appears to be an ancient mutation shared by northern and central European populations. Our present observation of a decreased disulfide bridge formation between GPIb alpha and GPIb beta shows that GPIX is not only needed for the correct assembly of the complex but might also be needed for the disulfide bridge formation between GPIb alpha and GPIb beta.

Adaptative lensing driven by the radiation pressure of a continuous-wave laser wave upon a near-critical liquid liquid interface.

The bending of a liquid interface by the radiation pressure of a cw laser wave is generally weak. To strongly enhance the coupling, we investigate lensing in a near-critical phase-separated liquid mixture. By continuously tuning the softness of the meniscus by varying the temperature, we observed huge stationary interface deformations at low beam power that led to an important variation of the resultant soft lensing. We also illustrate the crucial role played by temperature in this process to demonstrate its potential use in lens adaptation.

Early inflammatory response after elective abdominal aortic aneurysm repair: a comparison between endovascular procedure and conventional surgery.

OBJECTIVE: To determine the nature of and to compare the inflammatory responses induced by (1) endovascular and (2) conventional abdominal aortic aneurysm (AAA) repair. MATERIAL AND METHODS: Twelve consecutive patients undergoing elective infrarenal AAA repair were prospectively studied. Seven patients were selected for endovascular procedures (the EAAA group); five patients underwent open surgery (the OAAA group). Three control patients undergoing carotid thromboendarterectomy were also included. Serial peripheral venous blood samples were collected preoperatively, immediately after declamping or placement of the endograft, and at hours 1, 3, 6, 12, 24, 48, and 72. Acute phase response expression of peripheral T lymphocyte and monocyte activation markers and adhesion molecules (flow cytometry), soluble levels of cell adhesion molecules (enzyme-linked immunosorbent assay), cytokine (tumor necrosis factor alpha, interleukin-6, and interleukin-8) release (enzyme-linked immunosorbent assay), and liberation of complement products (nephelometry) were measured. RESULTS: Regarding acute phase response, the EAAA and OAAA groups showed significant increases in C-reactive protein (P <.001 and P =.001), body temperature (P =.035 and P =.048), and leukocyte count (P <.001 and P <.001). Similar time course patterns were observed with respect to body temperature (P =.372). Statistically significant different patterns were demonstrated for C-reactive protein (P =.032) and leukocyte count (P =.002). Regarding leukocyte activation, a significant upregulation of peripheral T lymphocyte CD38 expression was observed in the OAAA group only (P =.001). Analysis of markers such as CD69, CD40L, CD25, and CD54 revealed no perioperative fluctuations in any group. Regarding circulating cell adhesion molecules, the EAAA and OAAA groups displayed significant increases in soluble intercellular adhesion molecule-1 (P =.003 and P =.001); there was no intergroup difference (P =.193). All groups demonstrated high soluble von Willebrand factor levels (P =.018, P =. 007, and P =.027), there being no differences in the patterns (P =. 772). Otherwise, soluble vascular cell adhesion molecule-1, soluble E-selectin, and soluble P-selectin did not appear to vary in any group. Regarding cytokine release, although a tendency toward high tumor necrosis factor alpha and interleukin-8 levels was noticed in the EAAA group, global time course effects failed to reach statistical significance (P =.543 and P =.080). In contrast, interleukin-6 showed elevations in all groups (P =.058, P <.001, and P =.004). Time course patterns did not differ between the EAAA and OAAA groups (P =.840). Regarding complement activation, the C3d/C3 ratio disclosed significant postoperative elevations in the EAAA and OAAA groups (P =.013 and P =.009). This complement product release was reduced in the EAAA group (P <.001). CONCLUSIONS: The current study indicated that both endovascular and coventional AAA repair induced significant inflammatory responses. Our findings showed that there were no large differences between the procedures with respect to circulating cell adhesion molecule and cytokine release. Moreover, the endoluminal approach produced a limited response in terms of acute phase reaction, T lymphocyte activation, and complement product liberation. This might support the concept that endovascular AAA repair represents an attractive alternative to open surgery. Given the relatively small sample size, further larger studies are required for confirmation of our observations.

Efficacy of oral immunotherapy on respiratory infections in hemodialysis patients: a double-blind, placebo-controlled study.

BACKGROUND: Hemodialysis (HD) patients suffer from several immune defects that make them prone to develop bacterial infections, in particular respiratory tract infections (RTIs). PATIENTS AND METHODS: As previous studies have shown that oral immunotherapy with an immunomodulating bacterial extract (IBE) is effective against RTIs, we decided to test its efficacy and safety in HD patients during a double-blind placebo-controlled prospective study. 40 HD patients with a documented history of RTIs in the previous year were treated for 24 weeks of the endemic season with one capsule daily of IBE (n = 21) or placebo (PL, n = 19). Clinical examinations, measurements of Mac-1 and gp150.95 on circulating phagocytes and routine laboratory evaluations were performed at week 0, 4, 12 and 24. Patients were also examined at each dialysis session allowing an accurate recording of any infectious episode, its treatment and of any untoward effect. RESULTS: During the last period of the study (weeks 13-24), IBE significantly reduced the number of patients with RTIs and consequently of antibiotic treatment courses as compared to PL (p = 0.018), whereas no difference was detected between IBE and PL during periods I (weeks 0-4) and II (weeks 5-12). There was no difference between IBE and PL for other, non respiratory infections. IBE was associated at several time points with an increased expression on phagocytes of adhesion molecules involved in phagocytosis (Mac-1 and gp150.95). However, the expression of these molecules was not predictive for the occurrence of RTI. IBE was on the whole as well tolerated as PL, 7 patients presented side effects (5 IBE, 2 PL, NS) which led to drop-out in 4 cases (3 IBE, 1 PL). No serious side effect was recorded, gastrointestinal upset being the most prevalent type. CONCLUSION: The results of this study indicate that immunomodulation with selected bacterial extracts constitutes a promising approach for the prevention of bacterial airway infections in groups at risk, such as HD patients.

Late stage kinetics of a phase separation induced by a cw laser wave in binary liquid mixtures.

cw laser waves can be used to locally induce phase transitions. We investigate experimentally and theoretically a laser-driven liquid-liquid phase separation in a micellar phase of microemulsion and analyze its late stage kinetics. The medium is optically quenched in composition in the metastable region of the phase diagram. Two processes can lead to these concentration variations: electrostriction and thermodiffusion. The first originates from induced dipolar couplings in a field gradient. The second corresponds to a variation in concentration driven by a small thermal gradient. Since the nucleated droplets are optically trapped by the beam, we show that it becomes possible to experimentally analyze an academic situation, i.e., the diffusion-driven growth of a single droplet in compensated gravity. The late stage of this kinetics can be divided into two parts, a bulk behavior and a regime controlled by the finite transverse size of the beam. The bulk regime is totally analogous to that observed in classical situations (R proportional, variant t(1/3), where R is the droplet radius and t the time), and the scaling of the amplitudes in terms of reduced length and time scales is in total agreement with the expected behaviors for fluids belonging to the same Ising universality class. Moreover, the Gaussian beam behaves as an optical bottle with "soft walls" in which the absence of rigid boundaries, and thus of wetting couplings, allows an intrinsic description of the influence of finite-size effects on the kinetics. The beam size breaks the dynamic universality when the growing domains start to feel it. We experimentally investigate the resulting slowing down, and a diffusion-driven model of the growth inside a laser wave is built for comparison. The good agreement observed for the bulk regime and during its modification induced by finite-size effects opens a promising field for the development of this new application of laser waves to control out-of-equilibrium liquid mixtures.

Generation of immature autologous clinical grade dendritic cells for vaccination of cancer patients.

BACKGROUND: Dendritic cell (DC)-based vaccine is a promising approach for cancer therapy. Pioneer trials have been conducted using DC generated in research conditions. There is now a need for generating DC in clinical grade conditions, including the use of closed systems, avoidance of FCS and respect of good manufacturing practices (GMP). METHODS: DC were generated from 84 leukapheresis products of 27 cancer patients enrolled in two Phase I/II trials of vaccination of either MAGE+tumors (n = 24) or prostate cancer (n = 3). Monocytes were seeded in culture bags in a serum-free medium supplemented with IL-4 and GM-CSF. After a 7 day culture, DC were collected and most were pulsed with various MAGE-derived peptides. RESULTS: After a short leukapheresis (mean time: 66 min; mean processed blood: 5 L), a mean of 6 x 10(9) WBC were collected, from which 2.25 x 10(9) were seeded. The culture procedure yielded a large number of DC (mean: 62 x 10(6) DC) harboring the expected phenotype of immature DC (CD1a(+) CD14(-) HLA-DR(+) CD80(+) CD86(+) CD83(-)). This phenotype was not altered by peptide loading. These DC, either fresh or thawed, were functionally effective invitro. Their s.c. and i.v. injections were devoid of any short-term side effect and associated with the induction of immune responses in the patients. DISCUSSION: Large numbers of functional immature clinical grade DC can be generated in a closed system from leukapheresis products in cancer patients. These results provide the basis for large-scale studies of cancer immunotherapy under improved safety conditions.