Optical transmission through double-layer, laterally shifted metallic subwavelength hole arrays.

We measure the transmission of IR radiation through double-layer metal films with periodic arrays of subwavelength holes. When the two metal films are placed in sufficiently close proximity, two types of transmission resonances emerge. For the surface plasmon mode, the electromagnetic field is concentrated on the outer surface of the entire metallic layer stack. In contrast, for the guided mode, the field is confined to the gap between the two metal layers. Our measurements indicate that, as the two layers are laterally shifted from perfect alignment, the peak transmission frequency of the guided mode decreases significantly, while that of the surface plasmon mode remains largely unchanged, in agreement with numerical calculations.

Casimir force on a surface with shallow nanoscale corrugations: geometry and finite conductivity effects.

We measure the Casimir force between a gold sphere and a silicon plate with nanoscale, rectangular corrugations with a depth comparable to the separation between the surfaces. In the proximity force approximation (PFA), both the top and bottom surfaces of the corrugations contribute to the force, leading to a distance dependence that is distinct from a flat surface. The measured Casimir force is found to deviate from the PFA by up to 10%, in good agreement with calculations based on scattering theory that includes both geometry effects and the optical properties of the material.

Measurement of the Casimir force between a gold sphere and a silicon surface with nanoscale trench arrays.

We report measurements of the Casimir force between a gold sphere and a silicon surface with an array of nanoscale, rectangular corrugations using a micromechanical torsional oscillator. At distances between 150 and 500 nm, the measured force shows significant deviations from the pairwise additive formulism, demonstrating the strong dependence of the Casimir force on the shape of the interacting bodies. The observed deviation, however, is smaller than the calculated values for perfectly conducting surfaces, possibly due to the interplay between finite conductivity and geometry effects.

Controlling the phase delay of light transmitted through double-layer metallic subwavelength slit arrays.

We demonstrate that the phase of light transmitted through double-layer subwavelength metallic slit arrays can be controlled through lateral shift of the two layers. Our samples consist of two aluminum layers, each of which contains an array of subwavelength slits. The two layers are placed in sufficient proximity to allow coupling of the evanescent fields at resonance. By changing the lateral shift between the layers from zero to half the period, the phase of the transmitted electromagnetic field is increased by pi, while the transmitted intensity remains high. Such a controllable phase delay could open new capabilities for nanophotonic devices that cannot be achieved with single-layer structures.

Chemical modification of the electronic conducting states in polymer nanodevices.

Organic materials offer new electronic functionality not available in inorganic devices. However, the integration of organic compounds within nanoscale electronic circuitry poses new challenges for materials physics and chemistry. Typically, the electronic states in organic materials are energetically misaligned with the Fermi level of metal contacts. Here, we study the voltage-induced change in conductivity in nanoscale devices comprising a monolayer of polyelectrolyte macromolecules. The devices are fabricated using integrated shadow masks. Reversible switching is observed between conducting (ON) and non-conducting (OFF) states in the devices. The open design of our devices easily permits chemical modification of the polyelectrolyte, which we show has a pronounced effect on the ON-OFF switching. We suggest that the switching voltage ionizes the polymers, creating a conducting channel of electronic levels aligned with the contact Fermi level.

Optical transmission through double-layer metallic subwavelength slit arrays.

We present measurements of transmission of infrared radiation through double-layer metallic grating structures. Each metal layer contains an array of subwavelength slits and supports transmission resonance in the absence of the other layer. The two metal layers are fabricated in close proximity to allow coupling of the evanescent field on individual layers. The transmission of the double layer is found to be surprisingly large at particular wavelengths, even when no direct line of sight exists through the structure as a result of the lateral shifts between the two layers. We perform numerical simulations using rigorous coupled wave analysis to explain the strong dependence of the peak transmission on the lateral shift between the metal layers.

Kinetics of the development and recovery of the lung from IgE-mediated inflammation: dissociation of pulmonary eosinophilia, lung injury, and eosinophil-active cytokines.

Events occurring up to 16 d after antigen challenge were characterized using a novel protocol employing four bronchoscopies, two segmental antigen challenge (SAC) procedures (on Days 1 and 2), and six bronchoalveolar lavages (BALs) (on Days 1, 2, 9, and 16) in three groups: ragweed allergic asthmatics with dual phase airway reactions (AA-D), allergic asthmatics with a single early airway reaction (AA-S), and nonallergic nonasthmatic control subjects. In AA-D subjects, SAC produced a marked eosinophilic inflammatory response at 24 h associated with eosinophil degranulation (eosinophil cationic protein [ECP] in BAL fluid) and lung injury, which largely resolved by Day 16. When the second antigen-challenged segment (SAC performed on Day 2) was lavaged 7 d after challenge (Day 9), a persistent pulmonary eosinophilia was noted accompanied by minimal elevations in ECP and albumin. Eosinophil-active cytokines showed unique patterns: interleukin-5 (IL-5) increased in the antigen segment on Day 2 then returned to baseline after 7 d; granulocyte-macrophage colony-stimulating factor (GM-CSF) peaked at Day 2 but was persistently elevated throughout Day 16 in antigen segments, and increased in control segments at late time points; IL-3 levels were constant and similar in antigen and control segments. Changes were specific to AA-D subjects in comparison with control subjects. Elements of the IgE-mediated pulmonary inflammatory response differ markedly in their development and resolution.

Neutrophil recruitment as a factor limiting injury or promoting recovery from acute lung injury.

We studied 1) neutrophil mobilization in sheep given endotoxin (10 ng.kg-1.min-1, n = 5) for 4 h, 2) surviving (n = 17) and nonsurviving sheep (n = 8) during a 12-h infusion of endotoxin, and 3) adult sheep (n = 8) or lambs (n = 8) infused with endotoxin for 12 h. Bone marrow cells of sheep declined from a baseline value of 10,533 +/- 1,784 to 5,966 +/- 1,980 cells/microliter (P < 0.05) 4 h after endotoxin. After 12 h of endotoxin infusion, circulating neutrophils remained reduced from baseline values of 2,000-4,000 cells/microliter to 343 +/- 70 in lambs and 484 +/- 236 in nonsurviving sheep, while beginning to recover in surviving sheep to 1,838 +/- 467 cells/microliter. In lambs and nonsurviving sheep, a 12-h infusion of endotoxin increased lung lymph protein clearance tenfold compared with a fivefold increase in surviving sheep. Neutrophils cultured from sheep bone marrow exposed to lamb postendotoxin plasma failed to increase in cell number (609 +/- 229 to 610 +/- 182 cells/microliter), whereas similar cells exposed to adult sheep postendotoxic plasma showed a significant increase in cell number (1,069 +/- 101 to 2,293 +/- 448 cells/microliter, P < 0.05). Our results are consistent with the hypothesis that the ability to recruit neutrophils to the circulation during periods of inflammation is important in limiting the severity of acute lung injury.

Endotoxin infusion in anesthetized sheep is associated with intrapulmonary sequestration of leukocytes that immunohistochemically express tumor necrosis factor-alpha.

Plasma levels of tumor necrosis factor-alpha (TNF-alpha) peak between 2 and 4 h during a 12-h continuous infusion of endotoxin in awake sheep. We hypothesized that a source of this TNF-alpha is the pool of leukocytes that accumulate in the pulmonary circulation. To test this hypothesis, we physiologically monitored six anesthetized sheep during baseline and 4-h endotoxin infusion periods (10 ng/kg x min). We obtained open-lung biopsies at baseline and at 20 min and 2 and 4 h during the endotoxin infusion period for immunohistochemical localization of TNF-alpha. The plasma concentration of TNF-alpha increased from an average baseline concentration of 0.06 +/- 0.03 ng/ml (mean +/- SD) to a peak of 1.40 +/- 0.28 ng/ml at 2 h of the endotoxin infusion. We observed increased cytoplasmic TNF-alpha immunoreactivity in situ among neutrophils and intravascular mononuclear phagocytes during the endotoxin infusion compared with baseline. Also, the number of immunopositive leukocytes increased in the pulmonary circulation during the continuous infusion of endotoxin. We conclude that TNF-alpha-producing leukocytes accumulate in the pulmonary circulation during endotoxemia. These cells probably contribute to both the rise in the circulating levels of TNF-alpha and the development of acute lung injury.

sVCAM-1 levels after segmental antigen challenge correlate with eosinophil influx, IL-4 and IL-5 production, and the late phase response.

Evidence from in vitro studies suggests a potential role for vascular cell adhesion molecule-1 (VCAM-1) in eosinophil trafficking. We hypothesized that induction of VCAM-1 occurs in the lung during IgE-mediated airway inflammation in humans. The technique of segmental antigen provocation followed by bronchoalveolar lavage (BAL) at 24 h was used to study 27 ragweed-allergic asthmatics (AA) and 18 atopic nonasthmatics (ANA). Total and differential cell counts were performed, and IL-4, IL-5, and soluble (VCAM) (sVCAM) levels in concentrated BAL fluid were measured by ELISA. A large increase in sVCAM levels after segmental challenge in both AA and ANA (1.79 +/- 0.31 to 139.39 +/- 68.58 ng/ml, p < 0.0005 and 2.85 +/- 0.80 to 98.25 +/- 77.35 ng/ml, p < 0.05, respectively) was observed. BAL IL-4 and IL-5 also increased after challenge (IL-4: 51.7 +/- 17.72 to 150.1 +/- 58.82 pg/ml, 0.05 < p < 0.10, n = 20 for AA, and 36.6 +/- 9.05 to 116.8 +/- 51.5 pg/ml, 0.05 < p < 0.10, n = 15 for ANA; IL-5: 0 to 2.67 +/- 1.62 ng/ml, p < 0.01, n = 16 for AA, and 0 to 2.87 +/- 2.16 ng/ml, 0.05 < p < 0.10, n = 10 for ANA). In both groups, the majority of the increase in sVCAM, IL-4, and IL-5 was accounted for by subjects who displayed a dual phase response after whole-lung antigen inhalation. This fact, plus the strong correlation observed between postchallenge sVCAM, IL-4, and IL-5 levels and eosinophil influx, suggests that VCAM, IL-4, and IL-5 play important roles in the recruitment of eosinophils to the lung of humans after antigen challenge.

In vitro release of salicylic acid from lanolin alcohols-ethylcellulose films.

Lanolin alcohols-ethylcellulose films were investigated as a potential drug delivery system for the controlled release of salicylic acid. The effects of changes in film composition, drug concentration, drug solubility, and stirrer speed on the in vitro release of salicylic acid have been examined. The drug release has been found to obey a diffusion-controlled matrix model and square root of time release profile both in the suspension and solution cases.