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We present a study of the basic optical properties of colloidal CdSe/ZnS core/shell quantum dots entrained in a microstructured optical fiber. Quantum dots suspended in heptane were pulled into the holes surrounding the solid core of a microstructured optical fiber of the holey fiber class via capillary action and are found to remain in the fiber. In this experiment, a laser coupled into the fiber photoexcited quantum dots along the length of the fiber. Quantum dot emission was observed to couple into the fiber core and propagate along the fiber. To investigate the use of such a system in fiber-based light generation or amplification, a second laser overlapping the low-energy portion of the quantum dot emission was simultaneously coupled into the fiber. We observed apparent amplification of this light when photoexciting the quantum dots well above their bandedge.

In this paper we present the results of research aimed at the development of a 'smart' bed to non-intrusively monitor patient respiration, heart rate and movement using spatially distributed integrating multimode fibre optic sensors. The research is focused upon allowing more automation of patient care, an especially important matter for the elder population, which is a rapidly growing fraction of much of the world population today. Two spatially integrating fibre optic sensors were investigated, one of which was based on inter-modal interference and the other on mode conversion. The sensing fibre was integrated into a bed and test subjects were monitored in different positions. The sensor outputs were then correlated with subject movement, respiration rate and heart rate. The results indicated that the inter-modal sensor could detect patient movement and respiration rate while the mode conversion sensor could detect patient movement, respiration rate and heart rate. Results and analysis of the research are presented and future research activities discussed.

Quantum dot-embedded microspheres offer a promising technology for the development of a fluid-based DNA microarray to replace current biochip microarray technology. The narrow emission and long lifetime from the quantum dots (QD's) is ideal for dense spectral multiplexing. Also, the QD's may all be excited by a single source. To implement this solution, we have fabricated CdSe quantum dots following published procedures and embedded them in polystyrene microspheres. As a first step in this development, we have investigated the use of a flow cytometer in analyzing the encoded microspheres. We demonstrate the use of a microsphere-based DNA detection system and investigate the readout of quantum dot-tagged microspheres. We also discuss some of the inherent limitations and difficulties of using such a system to address the need for a high-throughput readout for spectral multiplexing for fluid-based DNA microarrays.

The recombinant protein Ultrabithorax (Ubx), a Drosophila melanogaster Hox transcription factor, self-assembles into biocompatible materials in vitro that are remarkably extensible and strong. Here, we demonstrate that the strength of Ubx materials is due to intermolecular dityrosine bonds. Ubx materials auto-fluoresce blue, a characteristic of dityrosine, and bind dityrosine-specific antibodies. Monitoring the fluorescence of reduced Ubx fibers upon oxygen exposure reveals biphasic bond formation kinetics. Two dityrosine bonds in Ubx were identified by site-directed mutagenesis followed by measurements of fiber fluorescent intensity. One bond is located between the N-terminus and the homeodomain (Y4/Y296 or Y12/Y293), and another bond is formed by Y167 and Y240. Fiber fluorescence closely correlates with fiber strength, demonstrating that these bonds are intermolecular. To our knowledge, this is the first identification of specific residues that participate in dityrosine bonds in protein-based materials. The percentage of Ubx molecules harboring both bonds can be decreased or increased by mutagenesis, providing an additional mechanism to control the mechanical properties of Ubx materials. Duplication of tyrosine-containing motifs in Ubx increases dityrosine content in Ubx fibers, suggesting these motifs could be inserted in other self-assembling proteins to strengthen the corresponding materials.

The extensive use of nanomaterials in new products for the building envelope is expanding rapidly and continues to influence materials science and environmental health. However, there is still uncertainly around the safety of these novel materials to humans and the environment; therefore, more life cycle data is needed. One analytical technique to gather information critical to the development of safe nanomaterials is to characterize the physicochemical properties of the nano-enabled product along various stages of the product life cycle. This research investigates two different products fortified with nanoscale titania relevant to the building and construction industry: (1) a white paint and (2) a lacquer formulation. Three brands of commercially available titanium dioxide (TiO2) nanoparticles were incorporated into labformulated paint and lacquer mixtures. These fortified products were subjected to simulated degradation processes (a.k.a. “wear-and-tear” scenarios) to mimic the real world. Unincorporated TiO2, as well as TiO2 incorporated “wornand- torn” powders, were processed and analyzed for physical, chemical, and toxicological characteristics. Electron microscopy confirmed the presence of nanoscale TiO2 particles in the painted and lacquered matrices for all three nanoparticle-types. Cell viability and reactive oxygen species (ROS) generation was measured in immortalized human lung epithelial cells (A549). Results from bioassays showed that ROS generation between unincorporated TiO2 particles and TiO2 incorporated paint powders showed little difference, but, the TiO2 incorporated lacquered powders demonstrated significantly lower ROS generation and cell death. Thus, the polymer-based lacquer mitigated tissue damage. Our results show that using a life cycle approach may help provide data – and by extension, an understanding - of nanomaterial properties in the context of developed consumer products.

Summary This work describes a potexvirus obtained from patchouli, Pogostemon clabin, collected in Sao Paulo, Brazil in 1992. The plants showed mosaic and were infected by a potyvirus and a potexvirus. The potexvirus had a host range limited to Amaranthaceae, Solanaceae and Labiatae and was named Patchouli virus X (PatVX). PatVX was not transmitted by scissors pruning, in tobacco seeds or by Myzus nicotinae. The virus was purified and a specific antiserum with a titre great than 1:512 000 in dot-ELISA was produced. The virus was serologically related to Papaya mosaic virus, Potato virus X, Viola mottle virus, White clover mosaic virus and Lily virus X. It had a coat protein of 21 071 ± 1 010 Mr. as determined by SDS-PAGE. Immunolabelling tests demonstrated that fibrillar masses in the cytoplasm contain the coat protein. The presence of a dsRNA was detected in PatVX infected plants.

Erythrocyte abundance, mobility, and carrying capacity make them attractive as a platform for blood analyte sensing as well as for drug delivery. Sensor-loaded erythrocytes, dubbed erythrosensors, could be reinfused into the bloodstream, excited noninvasively through the skin, and used to provide measurement of analyte levels in the bloodstream. Several techniques to load erythrocytes, thus creating carrier erythrocytes, exist. However, their cellular characteristics remain largely unstudied. Changes in cellular characteristics lead to removal from the bloodstream. We hypothesize that erythrosensors need to maintain native erythrocytes’ (NEs) characteristics to serve as a long-term sensing platform. Here, we investigate two loading techniques and the properties of the resulting erythrosensors. For loading, hypotonic dilution requires a hypotonic solution while electroporation relies on electrical pulses to perforate the erythrocyte membrane. We analyze the resulting erythrosensor signal, size, morphology, and hemoglobin content. Although the resulting erythrosensors exhibit morphological changes, their size was comparable with NEs. The hypotonic dilution technique was found to load erythrosensors much more efficiently than electroporation, and the sensors were loaded throughout the volume of the erythrosensors. Finally, both techniques resulted in significant loss of hemoglobin. This study points to the need for continued development of loading techniques that better preserve NE characteristics.

Understanding the effect of variability in the interaction of individual cells with nanoparticles on the overall response of the cell population to a nanoagent is a fundamental challenge in bionanotechnology. Here, we show that the technique of time-resolved, high-throughput microscopy can be used in this endeavor. Mass measurement with single-cell resolution provides statistically robust assessments of cell heterogeneity, while the addition of a temporal element allows assessment of separate processes leading to deconvolution of the effects of particle supply and biological response. We provide a specific demonstration of the approach, in vitro, through time-resolved measurement of fibroblast cell (HFF-1) death caused by exposure to cationic nanoparticles. The results show that heterogeneity in cell area is the major source of variability with area-dependent nanoparticle capture rates determining the time of cell death and hence the form of the exposure–response characteristic. Moreover, due to the particulate nature of the nanoparticle suspension, there is a reduction in the particle concentration over the course of the experiment, eventually causing saturation in the level of measured biological outcome. A generalized mathematical description of the system is proposed, based on a simple model of particle depletion from a finite supply reservoir. This captures the essential aspects of the nanoparticle–cell interaction dynamics and accurately predicts the population exposure–response curves from individual cell heterogeneity distributions.

For diabetics, continuous glucose monitoring and the resulting tighter control of glucose levels ameliorate serious complications from hypoglycemia and hyperglycemia. Diabetics measure their blood glucose levels multiple times a day by finger pricks, or use implantable monitoring devices. Still, glucose and other analytes in the blood fluctuate throughout the day and the current monitoring methods are invasive, immunogenic, and/or present biodegradation problems. Using carrier erythrocytes loaded with a fluorescent sensor, we seek to develop a biodegradable, efficient, and potentially cost effective method to continuously sense blood analytes. We aim to reintroduce sensor-loaded erythrocytes to the bloodstream and conserve the erythrocytes lifetime of 120 days in the circulatory system. Here, we compare the efficiency of two loading techniques: hypotonic dilution and electroporation. Hypotonic dilution employs hypotonic buffer to create transient pores in the erythrocyte membrane, allowing dye entrance and a hypertonic buffer to restore tonicity. Electroporation relies on controlled electrical pulses that results in reversible pores formation to allow cargo entrance, follow by incubation at 37°C to reseal. As part of the cellular characterization of loaded erythrocytes, we focus on cell size, shape, and hemoglobin content. Cell recovery, loading efficiency and cargo release measurements render optimal loading conditions. The detected fluorescent signal from sensor-loaded erythrocytes can be translated into a direct measurement of analyte levels in the blood stream. The development of a suitable protocol to engineer carrier erythrocytes has profound and lasting implications in the erythrosensor’s lifespan and sensing capabilities.

Trials were conducted during four consecutive summers (1995–1998) in North Carolina apple orchards to compare the effects of mating disruption and conventional pesticide treatments on tufted apple bud moth, Platynota idaeusalis, populations with regard to number of males caught in pheromone traps, number of egg masses, number of leaf shelters, and feeding damage. Pheromone traps caught significantly fewer males in mating disruption than in non-disruption plots. For the first generation, the number of tufted apple bud moth egg masses was higher in the conventional treatment, but in the second-generation egg mass numbers did not differ among treatments. Neither the number of TABM leaf shelters found per hour, nor the percentage of fruit with TABM feeding damage was significantly different among treatments. However, when TABM populations were high, damage was generally greater in mating disruption plots. Because this insect is usually not of economic concern until populations reach high densities, this insect appears to be less amenable to control with mating disruption compared to other tortricids.

Small-plot (approximately 0.1 ha) studies were used to evaluate different pheromone dispensing systems, application rates, and point-source densities for mating disruption of the tufted apple bud moth, Platynota idaeusalis (Walker). Using polyvinyl chloride spirals impregnated with tufted apple bud moth pheromone (1:1 ratio of E11-tetradecenyl alcohol/E11-tetradecenyl acetate), pheromone rates ofor = 1,482 spirals per hectare (74.1 g pheromone per hectare) were superior to a rate of 988 spirals per hectare (49.4 g pheromone per hectare) in decreasing male response to pheromone traps in 1995, whereas no differences were detected among rates of 988, 1,482 and 1,975 spirals per hectare in 1996. Within a range of 370-988 pheromone dispensers per hectare, point source densities were equally effective in suppressing male response to pheromone traps. Pheromone-impregnated paraffin disks were equally effective at inhibiting male response to pheromone traps compared with polyvinyl chloride spirals. However, a paraffin emulsion formulation of pheromone applied with a hand-held grease gun provided longer residual communication disruption effects than polyvinyl chloride spirals. Dilution of paraffin emulsion pheromone formulations in water for application with a backpack sprayer and airblast sprayer rendered them ineffective in reducing male response to pheromone traps. The releases of pheromone from polyvinyl chloride spirals and paraffin disks aged in the field were described by a linear and negative logarithmic curve, respectively, indicating that dispenser life time should be longer for spirals. The ratio of acetate to alcohol components of pheromone released from spirals increased over time, whereas the release ratio remained more constant for paraffin disks. This suggests that the disruption efficacy of spirals may be prematurely reduced because of imbalance of the released components.

Die Entstehung von Atemnot ist wie die vom Schmerz bis heute nicht bekannt. Atemnot ist im Rettungsdienst ein haufiges Symptom z. B. bei Patienten mit kardiopulmonalen Erkrankungen. Dabei stellt die Atemnot sowohl in der Diagnostik als auch in der Einschatzung des Schweregrades ein groses Problem dar. Hilfsmittel wie Pulsoximetrie, Kapnometrie oder Fiberglasbronchoskopie erlauben nur eine bessere Einschatzung des Schweregrades, aber keine diagnostische Zuordnung. Die therapeutischen Basismasnahmen beinhalten das Freimachen und Freihalten der Atemwege sowie die maschinelle Beatmung. Spezielle Therapiemasnahmen sind in Abhangigkeit von der jeweiligen Verdachtsdiagnose zu treffen.

Zum Thema Die nicht-invasive Beatmung (NIV) über eine Maske ermöglicht bei vielen Patienten eine effiziente Beatmung unter Vermeidung der Risiken und Nebenwirkungen der endotrachealen Intubation. Für die chronisch-obstruktive Lungenerkrankung (COPD) sind die Vorteile der Maskenbeatmung im Hinblick auf Beatmungsdauer, Dauer der Intensivbehandlung, Prognose und Behandlungskosten inzwischen relativ gut durch Studien belegt. Bei anderen Indikationen –“Nicht-COPD-Patienten”– erlauben die verfügbaren Daten noch kein gesichertes Urteil, rechtfertigen aber einen Behandlungsversuch auch außerhalb von Studien in klinischer Routine. Nachteilig sind der initial höhere personelle Betreuungsaufwand bei NIV sowie die stark von der Erfahrung abhängige Erfolgsrate. Die wichtigste Voraussetzung für eine erfolgreiche nicht-invasive Beatmung in der Intensivmedizin ist die Bereitschaft von Ärzten und Pflegepersonal, eine ungewohnte Beatmungsphilosophie zu akzeptieren und die relativ einfache Technik der Maskenbeatmung zu erlernen. Bei Beherrschung der Technik kann die NIV aber eine wertvolle Hilfe vom Notarztwagen bis zur Intensivstation sein.

Die nichtinvasive Beatmung uber eine Maske ermoglicht bei vielen Patienten eine effiziente Beatmung unter Vermeidung der Risiken und Nebenwirkungen der endotrachealen Intubation. Fur die chronisch-obstruktive Lungenerkrankung sind die Vorteile der Maskenbeatmung im Hinblick auf Beatmungsdauer, Dauer der Intensivbehandlung, Prognose und Behandlungskosten inzwischen relativ gut durch Studien belegt. Bei anderen Indikationen erlauben die verfugbaren Daten noch kein gesichertes Urteil, rechtfertigen aber einen Behandlungsversuch auch auserhalb von Studien in der taglichen klinischen Routine. Nachteilig sind der tendenziell hohere personelle Betreuungsaufwand bei der nichtinvasiven Beatmung sowie die starke Erfahrungsabhangigkeit der Ergebnisse. Die wichtigste Voraussetzung fur eine erfolgreiche nichtinvasive Beatmung in der Intensivmedizin ist die Bereitschaft von Arzten und Pflegepersonal, eine ungewohnte Beatmungsphilosophie zu akzeptieren und die relativ einfache Technik der Maskenbeatmung zu erlernen.

Die Diagnose akuter Lungenarterienembolien (LE) bleibt trotz technischer Fortschritte schwierig. Beweisende anamnestische Angaben, Symptome oder klinische Untersuchungsbefunde gibt es nicht. Laborparameter, EKG und Rontgen-Thoraxaufnahme haben einzeln eine niedrige Sensitivitat und Spezifitat. Die Echokardiographie ist durch den Nachweis einer Rechtsherzbelastung hilfreich bei kritisch kranken Patienten. Die Sonographie des tiefen Venensystems ist ein weiterer Baustein der Diagnostik bei LE-Verdacht. Normale Befunde schliesen eine Lungenarterienembolie aber nicht aus. Die Spiral-CT – als Angio-CT mit Kontrastmittel – kann grosere Lungenarterienembolien nachweisen aber nicht generell ausschliesen. In Zweifelsfallen mus eine Pulmonalisangiographie zum sicheren Nachweis und Ausschlus– insbesondere kleinerer – Lungenarterienembolien durchgefuhrt werden. Therapeutisch mus zwischen hamodynamisch stabilen und kompromittierten Patienten unterschieden werden. Bei hamodynamisch stabilen Patienten ist die therapeutische Heparinisierung Therapie der Wahl. Die Thrombolyse bleibt hamodynamisch instabilen Patienten vorbehalten. In ihrer thrombolytischen Wirkung sind rt-PA sowie Urokinase und Streptokinase – in einem Kurzlyse-Protokoll – vergleichbar. Eine statistisch signifikante Senkung der Mortalitat durch die Thrombolyse-Therapie konnte bisher in keiner Studie bewiesen werden.

Trotz gewachsenem Wissen uber Pathophysiologie und Therapie des Asthmas wurde die Mortalitat bisher nicht reduziert. Bei Patienten im Asthmaanfall kommt es zur fortschreitenden Atemwegsobstruktion, die stunden- oder tagelang anhalten kann und Folge von Entzundung der Atemwege, Bronchospasmus oder Schleimansammlungen im Lumen ist. Die Atemwegsobstruktion fuhrt zu Ventilations-Perfusions-Inhomogenitaten, Hyperinflation und vermehrter Atemarbeit. Typisch fur schwere Falle ist die Unfahigkeit zu sprechen, Schwitzen, Pulsus paradoxus, Einsatz der Atemhilfsmuskulatur, eine niedrige maximale exspiratorische Atemflusrate und ein Anstieg des Kohlendioxidpartialdrucks. Inhalative β 2-Sympathomimetika, Theophyllin, systemisch Kortikosteroide und Sauerstoff sind die Therapie der Wahl. Anticholinergika spielen eine untergeordnete Rolle in der Therapie des Asthmaanfalls. Zu den Medikamenten mit umstrittener Wirksamkeit zahlen Ketamin, Magnesiumsulfat, Heliox und Antibiotika. Die Bronchoskopie mit bronchoalveolarer Lavage kann bisher nicht als Routinemethode in der Behandlung der Asthmatiker angesehen werden. Bei Patienten, die auf die medikamentose Therapie nicht ansprechen, sollte fruhzeitig an die nicht-invasive Beatmung oder Intubation und maschinelle Beatmung gedacht werden. Die nicht-invasive Beatmung gehort zu den vielversprechenden Methoden bei der Behandlung nicht intubierter Patienten. Als Beatmungsstrategie

Unfavourable cycling conditions may successively lead to a porous PbO 2 structure with poor mechanical and electrical connection between the particles of which the porous electrode is built. Increasing active material resistance of this skeleton will induce a more and more inhomogeneous current distribution over the active mass, with successive restriction of the discharge/recharge processes to the active material area near to the grid. This leads to excessive mass utilisation in this very region, which aggravates the situation from cycle to cycle. The results are active material softening and shedding. This change of PbO 2 structure can be reverted, when cycling is continued with modified regimes. By this and by other means, lost capacity may be recovered. This effect is called reversible capacity decay or reversible insufficient mass utilization (RIMU). The Aggregate-of-Spheres Model (AOS), based on the behaviour of sintered bodies, describes semi-quantitatively the phenomena at the connecting sites of the particles of the PbO 2 active material, explaining the experimental findings of reversible capacity decay. The main features of reversible capacity loss are discussed in terms of AOS explanations, in order to work out strategies and limits for the improvement of lead/acid battery performance.

This paper describes the Exotic Pest Information Collection and Analysis (EPICA) project, a cooperative effort of the United States Department of Agriculture's (USDA) Center for Plant Health Science and Technology (CPHST) and the National Science Foundation's Center for Integrated Pest Management (CIPM). The EPICA team identifies, archives, evaluates, and communicates relevant information about exotic plant pests from around the world that potentially threaten US agriculture and the environment. The goal of the EPICA project is to provide key groups within USDA's Plant Protection and Quarantine (PPQ) with regular updates of vital pest information to enable a proactive safeguarding approach.

We have developed a low-cost technique using a conventional microwave oven to grow layered basic zinc acetate (LBZA) nanosheets (NSs) from a zinc acetate, zinc nitrate and HMTA solution in only 2 min. The as-grown crystals and their pyrolytic decomposition into ZnO nanocrystalline NSs are characterized by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), atomic force microscopy (AFM), X-ray diffraction (XRD) and photoluminescence (PL). SEM and AFM measurements show that the LBZA NSs have typical lateral dimensions of 1 to 5 μm and thickness of 20 to 100 nm. Annealing in air from 200°C to 1,000°C results in the formation of ZnO nanocrystalline NSs, with a nanocrystallite size ranging from 16 nm at 200°C to 104 nm at 1,000°C, as determined by SEM. SEM shows evidence of sintering at 600°C. PL shows that the shape of the visible band is greatly affected by the annealing temperature and that the exciton band to defect band intensity ratio is maximum at 400°C and decreases by a factor of 15 after annealing at 600°C. The shape and thickness of the ZnO nanocrystalline NSs are the same as LBZA NSs. This structure provides a high surface-to-volume ratio of interconnected nanoparticles that is favorable for applications requiring high specific area and low resistivity such as gas sensing and dye-sensitized solar cells (DSCs). We show that resistive gas sensors fabricated with the ZnO NSs showed a response of 1.12 and 1.65 to 12.5 ppm and 200 ppm of CO at 350°C in dry air, respectively, and that DSCs also fabricated from the material had an overall efficiency of 1.3%. PACS 81.07.-b; 62.23.Kn; 61.82.Fk

Quantum Dot (QD)/microsphere structures supporting Whispering Gallery Modes (WGMs) are attached to Atomic Force Microscope (AFM) cantilevers for characterization of the evanescent field around the QD/microsphere and utilization of the evanescent field for sensing at the apical surface of live cells. Following laser excitation, QD emission couples to WGMs that circumnavigate the microsphere via total internal reflection at the internal surfaces of the microsphere. The resulting evanescent field is characterized utilizing the high spatial control of an AFM in approaching a dye monolayer on a test surface. The measured evanescent field extends approximately 50 nm from the microsphere surface, matching theoretical predictions. This system was then used to sense the accumulation of integrin and formation of focal adhesions at the apical surface of cells.

Measurement of blood analytes provides crucial information about a patient’s health. Some such analytes, such as glucose in the case of diabetes, require long-term or near-continuous monitoring for proper disease management. However, current monitoring techniques are far from ideal: multiple-per-day finger stick tests are inconvenient and painful for the patient; implantable sensors have short functional life spans (i.e., 3-7 days). Due to analyte transporters on red blood cell (RBC) membranes that equilibrate intracellular and extracellular analyte levels, RBCs serve as an attractive alternative for encapsulating analyte sensors. Once reintroduced to the blood stream, the functionalized RBCs may continue to live for the remainder of their life span (120 days for humans). They are biodegradable and biocompatible, thereby eliminating the immune system response common for many implanted devices. The proposed sensing system utilizes the ability of the RBCs to swell in response to a decrease in the osmolarity of the extracellular solution. Just before lysis, they develop small pores on the scale of tens of nanometers. While at low temperature, analyte-sensitive dyes in the extracellular solution diffuse into the perforated RBCs and become entrapped upon restoration of temperature and osmolarity. Since the fluorescent signal from the entrapped dye reports on changes in the analyte level of the extracellular solution via the RBC transporters, interactions between the RBCs and the dye are critical to the efficacy of this technique. In this work, we study the use of a near infrared pH sensitive dye encapsulated within RBCs and assess the ability to measure dye fluorescence in vivo .

The influence of the addition of phosphoric acid to the electrolyte on the performance of gelled lead/acid electric-vehiicle batteries is investigated. This additive reduces the reversible capacity decay of the positive electrode significantly which is observed upon extended cycling when recharge of the battery is performed at low initial rate. This is important when low-rate on-board chargers are used. Pulsed discharge, typical for electric-vehicle application, induces reversible capacity decay more than constant-current discharge at a same depth-of-discharge, as well with as without the addition of phosphoric acid. By contrast, hindrance in presence of H3PO4 for both the recharge and the discharge reaction helps to homogenize the state of many individual cells during cycling in long battery strings. Reversible capacity loss, which occurs after extended cycling and when pulsed discharge is applied, can be recovered by a single discharge at very low rate with batteries with and without the addition of phosphoric acid. The discharge-rate dependency of the capacity is significantly reduced when phosphoric acid is added. The pulse discharge behaviour may be better, even if the nominal capacity is reduced. The experimental findings of the influence of phosphoric acid addition is discussed in terms of the aggregate-of-spheres model of reversible capacity decay.

We present a novel method for colloidal synthesis of one-dimensional ZnO nanopods by heterogeneous nucleation on zero-dimensional ZnO nanoparticle ‘seeds’. Ultra-small ZnO nanopods, multi-legged structures with sub-20 nm individual leg diameters, can be synthesized by hydrolysis of a Zn2+ precursor growth solution in presence of ∼4 nm ZnO seeds under hydrothermal conditions via microwave-assisted heating in as little as 20 min of reaction time. One-dimensional ZnO nanorods are initially generated in the reaction mixture by heterogeneous nucleation and growth along the [0001] direction of the ZnO crystal. Growth of one-dimensional nanorods subsequently yields to an ‘attachment’ and size-focusing phase where individual nanorods fuse together to form multi-legged nanopods having diameters ∼15 nm. ZnO nanopods exhibit broad orange-red defect-related photoluminescence in addition to a near-band edge emission at 373 nm when excited above the band-gap at 350 nm. The defect-related photoluminescence of the ZnO nanopods has been applied towards reversible optical humidity sensing at room temperature. The sensors demonstrated a linear response between 22% and 70% relative humidity with a 0.4% increase in optical intensity per % change in relative humidity. Due to their ultra-small dimensions, ZnO nanopods exhibit a large dynamic range and enhanced sensitivity to changes in ambient humidity, thus showcasing their ability as a platform for optical environmental sensing.

In this report, a technique for rapid synthesis of ZnO microstructures by microwave-assisted heating of precursors at hydrothermal conditions is demonstrated. Further, the reaction mechanism for the growth of ZnO microstructures is analyzed. An accelerated rate of reaction obtained using microwaves enables a dissolution-recrystallization mechanism for generation of one dimensional (1D) rod-like structures, thereby showing that time of reaction can be used to dictate ZnO microstructure morphology.

The Amsterdam discrete dipole approximation (ADDA) is used to study the effects of an inhomogeneous refractive index in the surrounding medium of a microspherical resonator on the quality and position of the whispering gallery modes (WGMs). The model consists of a polystyrene microsphere with a refractive index, n, of 1.587 surrounded by water (n=1.333) and an inhomogeneity (n=1.5) on top of the microsphere. The effect of the area of the inhomogeneity on the WGMs is modeled using the ADDA code and compared with Lorenz–Mie code. WGMs of various quantum dot embedded microspheres mounted on atomic force microscope cantilevers are experimentally measured and shown to be consistent with the model.

In the previous paper we demonstrated novel multiexcitons in a neutral mixed‐stack charge‐transfer solid. The lowest multiexciton, the biexciton, has recently been of interest also in the context of quasi‐one‐dimensional organic materials that are different from the mixed‐stack solids. The nature and strength of the optical transition from the exciton to the two‐exciton states is of importance in understanding photoinduced absorption as well as two‐photon absorption. We show that within the diverse theoretical models that describe these different classes of materials, the excited state absorption from the optical exciton to the two‐exciton states changes in a fundamental way upon the formation of the biexciton. The identical nature of the exciton absorption within these models is a consequence of one dimensionality.

Evanescent Waves (EWs) and Forster Resonance Energy Transfer (FRET) concepts combined with Atomic Force Microscopy (AFM) have been used for imaging and sensing. For the proposed EW microscopy system, Quantum Dot (QD) embedded Polystyrene microspheres are mounted on AFM cantilevers. When excited by laser, QDs luminescence couples to the Whispering Gallery Modes (WGMs) in the periphery of the microsphere. The resultant EWs extend on the order of 100 nm from the surface of the microsphere. These EWs decay exponentially and are explored as a tool to excite fluorescent labeled trans-membrane and near-membrane proteins. For the FRET system, QD coated silica microspheres are conjugated with fibronectin and mounted on AFM cantilevers. Moving the sphere down to the surface of the RFP-αv integrin tagged cells, fibronectins on the microsphere surface bind to integrins on the cell surface and FRET is observed between the QDs (donor) and RFP (acceptor). The detected fluorescence for the imaging system and the FRET efficiency for the sensing system are both functions of cell surface protein density. These innovative nanoscale imaging and sensing systems can be used to obtain unique dynamic data from living cells to improve understanding of cell adhesion and mechanobiology in cells.

Measurement of blood analytes, such as pH and glucose, provide crucial information about a patient's health. Some such analytes, such as glucose in the case of diabetes, require long-term or near-continuous monitoring for proper disease management. However, current monitoring techniques are far from ideal: multiple-per-day finger stick tests are inconvenient and painful for the patient; implantable sensors have short functional life spans (i.e., 3-7 days). Red blood cells serve as an attractive alternative for carriers of analyte sensors. Once reintroduced to the blood stream, these carriers may continue to live for the remainder of their life span (120 days for humans). They are also biodegradable and biocompatible, thereby eliminating the immune system response common for many implanted devices. The proposed carrier system takes advantage of the ability of the red blood cells to swell in response to a decrease in the osmolarity of the extracellular solution. Just before the membranes lyse, they develop small pores on the scale of tens of nanometers. Analyte-sensitive dyes in the extracellular solution may then diffuse into the perforated red blood cells and become entrapped upon restoration of physiological temperature and osmolarity. Because the membranes contain various analyte transporters, intracellular analyte levels rapidly equilibrate to those of the extracellular solution. A fluorescent dye has been loaded inside of red blood cells using a preswelling technique. Alterations in preparation parameters have been shown to affect characteristics of the resulting dye-loaded red blood cells (e.g., intensity of fluorescence).

The pyrolytic decomposition of layered basic zinc acetate (LBZA) nanobelts (NBs) and nanosheets (NSs) into nanocrystalline ZnO NBs/NSs has been investigated using scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray diffraction (XRD) and Photoluminescence (PL). We also report on the gas sensing response of the resulting ZnO nanomaterials to CO. The LBZA NBs were grown at 65°C for 9h in an aqueous solution of zinc acetate dehydrate and the LBZA NSs were grown in 2min in a standard microwave oven. AFM, SEM and XRD showed as-grown products possess the characteristic layered structure of LBZA crystals. XRD results showed that annealing as-grown products a 400°C in air caused a transformation from zinc acetate to nanocrystalline ZnO via thermal decomposition and that the crystalline domain size increased with temperature. The thickness of the NBs and NSs, determined via AFM, ranged from 10 to 50 nm. PL shows a larger defect band for ZnO NBs, compared to NSs. Gas sensors fabricated from 400°C annealed NBs showed a response of 1.62 when exposed to 200ppm of CO in dry air at 400°C. The same response was observed at 325°C for the NSs, which also had better response at lower concentrations. Our results indicate that ZnO nanostructures obtained by thermal decomposition of LBZA NBs/NSs could provide a cost effective route to high sensitivity gas sensors.

Error-free demultiplexing of 40 Gbit/s channels out of a 160 Gbit/s optical time-division signal is demonstrated using four-wave mixing in a semiconductor optical amplifier.

Molecules can be loaded into mammalian erythrocytes through a reversible lysis pore that forms in the membrane when placed in hypotonic media, the result being resealed red cell ghosts. Many studies on the sidedness of transport processes have utilized this approach. In addition, red cell ghosts encapsulated with enzymes have been used in patients to treat specific enzyme deficiencies, particularly when the substrate can cross the red cell membrane. Our long-term goal is to put fluorescent sensors inside erythrocytes, return the loaded red cell ghosts to the animal or patient, and then monitor the fluorescence non-invasively to follow changes in plasma analyte concentration. In this paper, we present a novel dialysis method for making the red cell ghosts. In addition, we present a theoretical analysis showing that it is not necessary that every loaded red cell ghost has the same dye concentration. Finally we discuss the constraints on the optimal affinity for the sensor/analyte interaction.

When CdSe/ZnS-polyethyleneimine (PEI) quantum dots (QDs) are microencapsulated in polymeric microcapsules, human fibroblasts are protected from acute cytotoxic effects. Differences in cellular morphology, uptake, and viability were assessed after treatment with either microencapsulated or unencapsulated dots. Specifically, QDs contained in microcapsules terminated with polyethylene glycol (PEG) mitigate contact with and uptake by cells, thus providing a tool to retain particle luminescence for applications such as extracellular sensing and imaging. The microcapsule serves as the ‘‘first line of defense’’ for containing the QDs. This enables the individual QD coating to be designed primarily to enhance the function of the biosensor.

We investigate the use of energy delivery using microwave radiation for both synthesis of nanoparticles as well as a hybrid imaging technique known as thermoacoustic tomography (TAT). In each instance, the absorption of microwave radiation is converted into heat. In the case of nanoparticle synthesis, water is used as the solvent and heated to induce synthesis of the nanostructures. For this aqueous synthesis technique, we demonstrate the use of both pulsed and continuous wave (CW) microwave systems operating at 2.45 GHz. In this report, we concentrate on ZnO nanostructures including nanorods, nanowire arrays and nanobelts. These are compared with nanowire arrays and nanobelts grown by vapor transport through both electron microscopy and photo-excited luminescence. We also review the use of iron oxide (Fe3O4) nanoparticles as contrast agents in TAT as previously reported. Here, we measured the properties of the colloidal nanoparticles in the microwave regime and compared the absorption with the TAT signal produced by our thermoacoustic imaging system at 3 GHz. The nanoparticles directly absorb the microwave radiation and produce a thermo-acoustic signal. The results from nanoparticles are compared to the signal produced by deionized water. The results demonstrate that microwaves represent an efficient method for the delivery of energy for both synthesis and biomedical imaging.

Incorporation of nanoparticles during the hierarchical self-assembly of protein-based materials can impart function to the resulting composite materials. Herein we demonstrate that the structure and nanoparticle distribution of composite fibers are sensitive to the method of nanoparticle addition and the physicochemical properties of both the nanoparticle and the protein. Our model system consists of a recombinant enhanced green fluorescent protein-Ultrabithorax (EGFP-Ubx) fusion protein and luminescent CdSe-ZnS core-shell quantum dots (QDs), allowing us to optically assess the distribution of both the protein and nanoparticle components within the composite material. Although QDs favorably interact with EGFP-Ubx monomers, the relatively rough surface morphology of composite fibers suggests EGFP-Ubx-QD conjugates impact self-assembly. Indeed, QDs templated onto EGFP-Ubx film post-self-assembly can be subsequently drawn into smooth composite fibers. Additionally, the QD surface charge impacts QD distribution within the composite material, indicating that surface charge plays an important role in self-assembly. QDs with either positively or negatively charged coatings significantly enhance fiber extensibility. Conversely, QDs coated with hydrophobic moieties and suspended in toluene produce composite fibers with a heterogeneous distribution of QDs and severely altered fiber morphology, indicating that toluene severely disrupts Ubx self-assembly. Understanding factors that impact the protein-nanoparticle interaction enables manipulation of the structure and mechanical properties of composite materials. Since proteins interact with nanoparticle surface coatings, these results should be applicable to other types of nanoparticles with similar chemical groups on the surface.

The bound states of n Frenkel excitons ( n = 2,3,…), which are called excitonic n-strings, are theoretically shown to exist in contrast with a system of Wannier excitons. The electronic structure and nonlinear optical responses of these excitonic n-strings are clarified. The first evidence for the excitonic 2- and 3-strings is provided from comparison of the calculated and observed differential transmission spectrum of an Anthracene-PMDA crystal pumped by femtosecond laser pulses.

Highly sensitive, miniature biosensors are desired for the development of new techniques for biological and environmental analyte sensing. One potential approach uses the detection of optical resonances, known as Whispering Gallery Modes (WGMs), from quantum dot embedded polystyrene microspheres. These modes arise from the total internal reflection of the quantum dot emission light within the high index polystyrene microsphere, to produce narrow spectral peaks, which are sensitive to refractive changes in the immediate vicinity of the microsphere surface. The high refractometric sensitivity of the WGMs in these microspheres offers potential for remote detection of molecules adsorbed onto or bound to the microsphere surface without the need for direct coupling of the light via an optical fiber. The sensitivity of these modes has been shown to exceed the theoretical sensitivity of a homogeneous microsphere, using a Mie theory model. This enhancement is believed to be due to the embedded layer of quantum dots at the surface of the microspheres. A model was developed to demonstrate that the embedded QDs could be modeled as a high index outer layer to explain the observed WGM spectra and explore the sensitivity of the modes. In this work, we extend this idea to multiple layers to model the effects of protein adsorption or binding to the surface. The theoretical results are shown to provide a close fit to our previous experimental results.

Quasi-noncritical phase-matched and quasi-phase-matched 2-µm optical parametric oscillations have been demonstrated and characterized in adhesive-free bonded multilayer walk-off compensated KTP composites with low pulse energy 1.064-µm pump laser.

Maximum power of 18.6 W has been measured at pump power of 23.7 W in Tm:fiber laser pumped adhesive-free bonded YAG/Ho:YAG/YAG composite. The corresponding slope efficiency is over 81% for both cw and Q-switched operations.

Various organisms can sense light through a large family of signaling proteins known as photoreceptors. Upon absorption of a photon in the appropriate wavelength range, photoreceptors undergo structural changes in the chromophore, an organic pigment embedded in the photosensory module of the protein. Phytochromes are red-light photoreceptors originally discovered in plants and more recently in bacteria. They are unique in their ability to undergo reversible photoconversion between two photoisomerizable states, Pr (red light ∼ 700 nm) and Pfr (far-red light ∼ 750 nm). In the photosynthetic bacterium, Rhodopseudomonas palustris, a pair of bacteriophytochromes, RpBphP2 (P2) and RpBphP3 (P3) modulate synthesis of a light-harvesting complex. P2 and P3 have the same biliverdin chromophore (BV) and share 52% amino acid sequence identity, yet they have distinct photoconversion properties. P2, similar to classical bacteriophytochromes, alternates between Pr and Pfr states. P3 is unusual since it alternates between Pr and a unique Pnr (near-red light ∼ 650 nm) state. Our experimental goal is to identify amino acid residues that form specific interactions with BV during photoconversion and as such play key roles in forming distinct photoisomerizable states of P2 and P3. Through site-directed mutagenesis of conserved amino acids informed by structural and sequence analysis of bacteriophytochromes, we created a single-amino acid mutant variant of P3 T480P that undergoes classic reversible photoconversion between Pr and Pfr states. We also report on P2 and P3 mutants that show minimal absorption in the red region of visible light spectrum or are naturally more fluorescent than wild-type proteins. Currently, we are investigating chemical mechanisms that justify observed P2 and P3 mutant phenotypes.

Very recently, the concept of artificial intracorporeal oxygenation of blood for patients suffering from respiratory failure has been introduced into clinical practice through development of a totally implantable intravascular oxygenator (IVOX). We report on the use of such a device in a patient who developed severe respiratory insufficiency secondary to prolonged hypovolaemic shock and pneumonia following successful repair of a ruptured abdominal aortic aneurysm in September, 1990. Postoperatively, severe hypoxaemia occurred (AaDO2 548-602 torr) despite extensive mechanical ventilatory support. There was no obvious chance to overcome this situation by conventional therapeutic measures and the decision was made to institute IVOX therapy. Hypoxaemia was resolved immediately and both FiO2 and tidal volume could be reduced within hours. The patient's respiratory condition continued to improve over the next days leading to termination of IVOX therapy after 71 hours. However, the necessity of long-term ventilatory support secondary to recurrent pneumonia and sepsis, multiple abdominal reoperations for ischemic colitis and retroperitoneal abscess prolonged his recovery. He was discharged from the hospital after four months and is alive and well now 14 months after his operation. He is the first long-term survivor after IVOX therapy in Europe. IVOX may be successfully used in selected patients while the indications and it's potential role in the therapy of severe respiratory failure still need to be defined.

Optical DPSK at 565 Mb/s is performed by direct modulation of a narrow-linewidth 1.5- mu m SL-QW-DFB (strain layer-quantum well-distributed feedback) transmitter laser. The bipolar RZ drive signal has no DC component which allows penalty-free transmission of 2/sup 23/-1 bit patterns. The heterodyne receiver contains an endless polarization controller with 12 rad/s tracking speed, depending on the tolerable intensity loss. A loss span of 62.3 dB is achieved,without degradation due to stimulated Brillouin scattering. >

Resonant coherent lattice vibrations in the vicinity of the indirect absorption edge in a ${\mathrm{BiI}}_{3}$ layered crystal are observed in a femtosecond pump-probe experiment. Coherent optical phonons that are impulsively excited by femtosecond pump pulses modulate the phase of probe pulses, causing oscillation of the probe spectrum in time. This oscillation, which has a period given by the period of the oscillation, continues for more than 100 cycles. We speculate that the coherent phonon-assisted indirect exciton transitions also contribute to the data.

Femtosecond pump-and-probe spectroscopy was adopted to study the hot carrier distribution in a CdSe thin film. In the experiment, a nonthermalized hot carrier distribution was observed when the pump was turned on. The nonthermalized distribution was observed at the 200 meV broad energy range extending from the pump energy to the low energy side. The low energy tail of the nonthermalized distribution indicates that the carrier-LO phonon scattering competes with the carrier-carrier scattering in the thermalization process. In this sense, this observation is a unique example of the nonthermalized hot carrier distribution in semiconductors. From the ratio of the nonthermalized distribution to the total one, the thermalization time was estimated to be 16-40 fs. In the wake of the thermalization, cooling of photogenerated carriers was observed. With an increase of the excitation density up to 1019 cm-3, the carrier cooling rate was slower. The observed cooling rate was slower than the theoretical calculation, taking account of the screening of the carrier-phonon interaction. This is ascribed to the hot phonon effects of the LO phonon and the TO phonon.

Femtosecond pump-and-probe spectroscopy was utilized to study the optical nonlinearities of excitons in CdSe. Under resonant excitation of the A-exciton, a 42 meV energy broadening of the B-exciton structure was observed. This broadening is caused by collisions between the A-exciton and the B-exciton. This is a rather unique observation of the scattering process between different kinds of excitons. Analysis indicates that the A-exciton-B-exciton scattering time is 31 fs. This time is well explained by a simple theory. Under resonant excitation of the B-exciton, a fast recovery of the bleaching was observed at the B-exciton. The recovery time of 0.9 ps is explained as the transformation time of B-excitons into A-excitons emitting LO phonons. The observed time constant agrees with the calculated scattering time based on the Frohlich interaction within an order of magnitude.

This paper reports the direct femtosecond observation of the dynamical bandgap renormalization and optical gain formation in a highly excited CdSe crystal. Interband excitation with 60 fs pulses results in broadening of the exciton at 0 fs, exciton bleaching and bandgap renormalization at 80 fs, and development of optical gain below the exciton level after 80 fs with rise time of 100 fs. At 380 fs, the optical gain reaches its maximum value and subsequently decreases slowly. Stimulated plasma luminescence has a peak around the energy where maximum gain is observed. The data are discussed in terms of plasma cooling, screening, state filling, and band-gap renormalization.