Emission dynamics of hybrid plasmonic gold/organic GaN nanorods.

We studied the emission of bare and aluminum quinoline (Alq3)/gold coated wurtzite GaN nanorods by temperature- and intensity-dependent time-integrated and time-resolved photoluminescence (PL). The GaN nanorods of ∼1.5 µm length and ∼250 nm diameter were grown by plasma-assisted molecular beam epitaxy. Gold/Alq3 coated GaN nanorods were synthesized by organic molecular beam deposition. The near band-edge and donor-acceptor pair luminescence was investigated in bare GaN nanorods and compared with multilevel model calculations providing the dynamical parameters for electron-hole pairs, excitons, impurity bound excitons, donors and acceptors. Subsequently, the influence of a 10 nm gold coating without and with an Alq3 spacer layer was studied and the experimental results were analyzed with the multilevel model. Without a spacer layer, a significant PL quenching and lifetime reduction of the near band-edge emission is found. The behavior is attributed to surface band-bending and Förster energy transfer from excitons to surface plasmons in the gold layer. Inserting a 5 nm Alq3 spacer layer reduces the PL quenching and lifetime reduction which is consistent with a reduced band-bending and Förster energy transfer. Increasing the spacer layer to 30 nm results in lifetimes which are similar to uncoated structures, showing a significantly decreased influence of the gold coating on the excitonic dynamics.

Controlling the exciton emission of gold coated GaAs-AlGaAs core-shell nanowires with an organic spacer layer.

Excitons are the most prominent optical excitations and controlling their emission is an important step towards new optical devices. We have investigated the exciton emission from uncoated and gold/aluminum quinoline (Alq3) coated GaAs-AlGaAs-GaAs core-shell nanowires (NWs) using temperature-, intensity- and polarization dependent photoluminescence (PL). Plasmonic GaAs-AlGaAs-GaAs NWs with a ∼10 nm thick Au coating but without an Alq3 spacer layer reveal a significant reduction of the PL intensity of the exciton emission compared with the uncoated NW sample. Plasmonic NW samples with the same nominal Au coverage and an additional Alq3 interlayer of 3 or 6 nm thickness show a clearly stronger PL intensity which increases with rising Alq3 spacer thickness. Time-resolved (TR) PL measurements reveal an increase of the exciton decay rate by a factor of up to two with decreasing Alq3 spacer thickness suggesting the presence of Förster energy transfer from NW excitons to plasmon oscillations in the gold film. The weak change of the decay time, however, indicates that Förster energy-transfer is only partially responsible for the PL quenching in the gold coated NWs. The main reason for the reduction of the PL emission is attributed to a gold induced band-bending in the GaAs NW core which causes exciton dissociation. With increasing Alq3 spacer thickness the band-bending decreases leading to a reduction of the exciton dissociation and PL quenching. Our interpretation is supported by electron energy loss spectroscopy measurements which show a signal reduction and blue shift of defect (possibly EL2) transitions when gold particles are deposited on NWs compared with bare or Alq3 coated NWs.

Real-time contrast-enhanced holographic imaging using phase coherent photorefractive quantum wells.

We demonstrate wide-field real-time and depth-resolved contrast enhanced holographic imaging (CEHI) using the all-optical phase coherent photorefractive effect in ZnSe quantum wells. Moving objects are imaged at large depth-of-field by the local enhancement of a static reference hologram. The high refresh rate of the holographic films enables direct-to-video monitoring of floating glass beads and of living Paramecium and Euglena cells moving in water. Depth resolution is achieved by tilting the incident laser beam with respect to the normal of the cuvette. This creates double images of the objects, which are analyzed geometrically and with Fresnel diffraction theory. A two-color CEHI set-up further enables the visualization of a concealed 95 µm thick wire behind a thin layer of chicken skin.

Eliminating thermal effects in z-scan measurements of thin PTCDA films.

We investigate the two-photon absorption (TPA) and nonlinear refraction of a micrometer thick 3,4,9,10-perylentetracarboxyl-dianhydride (PTCDA) film using z-scans with tightly focused 100 fs laser pulses. The PTCDA film was grown by organic molecular beam deposition on a Pyrex substrate. To study the influence of sample heating, the pulse repetition rate was varied between 4 MHz and 50 kHz with an acousto-optic pulse selector. We find that thermal effects diminish for pulse repetition times longer than 5 and 0.75 µs when using a 10x or 20x microscope lens, respectively, resulting in a TPA coefficient of 6 cm/GW and a nonlinear refractive index of 1.2 x 10⁻¹³ cm²/W at a wavelength of 820 nm.

Differential passive and active biaxial mechanical behaviors of muscular and elastic arteries: basilar versus common carotid.

Cerebrovascular disease continues to be responsible for significant morbidity and mortality. There is, therefore, a pressing need to understand better the biomechanics of both intracranial arteries and the extracranial arteries that feed these vessels. We used a validated four-fiber family constitutive relation to model passive biaxial stress-stretch behaviors of basilar and common carotid arteries and we developed a new relation to model their active biaxial responses. These data and constitutive relations allow the first full comparison of circumferential and axial biomechanical behaviors between a muscular (basilar) and an elastic (carotid) artery from the same species. Our active model describes the responses by both types of vessels to four doses of the vasoconstrictor endothelin-1 (10(-10)M, 10(-9)M, 10(-8)M, and 10(-7)M) and predicts levels of smooth muscle cell activation associated with basal tone under specific in vitro testing conditions. These results advance our understanding of the biomechanics of intracranial and extracranial arteries, which is needed to understand better their differential responses to similar perturbations in hemodynamic loading.

Index matching in multilayered organic waveguides.

Index matching of guided modes in birefringent multilayered organic waveguides opens new prospects for the design of mode coupling and mode switching devices. We demonstrate index matching of guided modes in two multilayered structures, in (a) a PTCDA-Alq3-PTCDA three-layer and (b) a PTCDA-Alq3 effective medium multilayer waveguide. The optical waveguides were grown on a Pyrex substrate by organic molecular beam deposition. The occurrence of index matching was investigated both experimentally by measuring the effective refractive index dispersion of transverse electric and magnetic modes using the m-line technique and theoretically by modelling the index dispersion with a transfer matrix algorithm.

Reactivity of acute lymphoblastic leukemia and normal bone marrow cells with the monoclonal anti-B-lymphocyte antibody, anti-Y 29/55.

Malignant lymphocyte populations in peripheral blood of patients with B-cell chronic lymphocytic leukemia, leukemic variant of B-cell non-Hodgkin's lymphoma, and hairy cell leukemia can be characterized by the use of a monoclonal murine antibody (anti-Y 29/55) which is directed against a cell membrane component normally confined to the sessile nonrecirculating cells of the B-lymphocyte population in lymphoid tissues. The present report describes the reactivity of the anti-Y 29/55 antibody with bone marrow cells obtained from children with acute lymphoblastic leukemia using an indirect immunofluorescence method in combination with morphological and cytokinetic studies. In 25 patients (acute lymphoblastic leukemia subtype: 14 common; 4 pre-B-cell; 4 null; and 3 T-cell), a maximum of 2% of cells (small lymphocytes) were stained. One patient presented with blasts exhibiting cytoplasmic and surface immunoglobulin M (IgM) (pre-B-B-cell acute lymphoblastic leukemia). About 11% of this patient's blast cells showed a positive reaction with anti-Y 29/55. They could not be differentiated by morphological criteria from the anti-Y 29/55-negative blast cell population. In another patient with pre-B-B-cell acute lymphoblastic leukemia, only 1% of anti-Y 29/55-positive cells was found. In bone marrow of children with relative lymphocytosis, 1.4 to 8.7% of mononuclear cells reacted with anti-Y 29/55. Morphologically, these cells were small lymphocytes and predominantly expressed surface IgM. In two of these children, a further subdivision of bone marrow cells could be achieved by combining anti-Y 29/55 and cytoplasmic IgM reactivity with [3H]thymidine pulse labeling. These studies revealed that the actively proliferating, normal pre-B-cell population was anti-Y 29/55-nonreactive, whereas a nonproliferating population of anti-Y 29/55-reactive, cytoplasmic IgM-positive cells probably represented B-cells with surface immunoglobulin M reacting when cytoplasmic IgM was assessed. We conclude that the reactivity of the monoclonal anti-B-cell antibody (anti-Y 29/55) is restricted to surface immunoglobulin-positive bone marrow cells and that neither leukemic or normal pre-B-cells nor common, null-cell, or T-cell acute lymphoblastic leukemia blasts react.

Nuclear lamin expression reveals a surprisingly high growth fraction in childhood acute lymphoblastic leukemia cells.

In an attempt to better characterize leukemic bone marrow cells of children with ALL in G0/G1, we studied the variation of the nuclear projection area (NPA) during the cell cycle. Approximately half of the increase of the nuclear volume during the cell cycle occurred before DNA synthesis. Next, we assessed by in situ hybridization (ISH) the expression of nuclear envelope type A/C and type B lamins in leukemic lymphoblast and unstimulated as well as stimulated normal peripheral blood mononuclear cells (PBMC). It was found that 82.0 +/- 16.0% of the ALL cells expressed B-type and 5.8 +/- 3.1% A/C-type lamins. The in vitro 3HdT pulse-labeling index (3HdT LI) of ALL cells varied from 1.3 to 16.8%. Of unstimulated PBMC 2.9 and 1.2% expressed lamin type B and A/C, respectively. The 3HdT LI was 0.8%. In conA-stimulated PBMC, the corresponding values were 95.3 and 74.8% and 31.0%, respectively. In view of the current concepts regarding G1 events and regulation of cell proliferation, we considered B-type lamin expression an early marker for the commitment to proliferation and used it for growth fraction (GF) determinations. By this method, a surprisingly high GF was found in ALL cell populations; there was no correlation between GF and the 3HdT LI, as seen in normal cells.

Proliferation of lymphoid precursor cells in the bone marrow of patients with various disorders of the immune system.

In the human bone marrow the nuclear enzyme terminal deoxynucleotidyl transferase (TdT) is expressed by cells during early stages of lymphocyte differentiation. In order to investigate a possible regulation of lymphopoiesis at this level of differentiation, the relative frequency and the in vitro 3H-thymidine labeling index (3HdT-LI) of TdT-positive bone marrow cells were assessed in patients with different functional activities of the immune system. TdT-positive lymphoid precursor cells could be detected in the bone marrow of all children investigated, including six patients with various forms of immunodeficiency. Neither a transient hyperfunction of the immune system during the immunological rebound after cessation of long-term chemotherapy for acute lymphoblastic leukemia, nor a congenital or acquired hypofunction of the immune system had any detectable influence on the invariably high in vitro 3HdT-LI of TdT-positive bone marrow cells, a phenomenon possibly related to an autonomous and high turnover of this precursor cell compartment in the human bone marrow.

Recovery of megakaryocytopoiesis in vitro in children with acute lymphoblastic leukemia during induction of remission.

In children with acute lymphoblastic leukemia (ALL), megakaryocytopoiesis was investigated in vitro by the semisolid agar culture technique. In untreated ALL the median number of committed megakaryocyte progenitor cells (CFU-Mk) in the bone marrow was 2 (range less than 0.1-8) per 10(5) bone marrow cells instead of 30 (range 14-93) in controls, the impairment being dependent on the degree of leukemic bone marrow infiltration. However, if the number of CFU-Mk was related to residual nonleukemic bone marrow cells only, two-thirds of the children investigated had a frequency of CFU-Mk within the normal range. After 2 weeks of induction therapy the majority of the children had a low number of CFU-Mk in the bone marrow (median 6, range 0.5-40), a fact that could no longer be explained by a dilution of CFU-Mk by leukemic cells. After 4 weeks of chemotherapy (day 29) the frequency of CFU-Mk had risen to 18 (range 3-67) per 10(5) bone marrow cells, a value still significantly (p less than 0.01) below the normal range. In contrast to the changes in the number of CFU-Mk the median cell number per megakaryocyte colony remained constant during induction of remission. After cessation of long-term chemotherapy all children investigated had a normal number of CFU-Mk, suggesting that no permanent chemotherapy-related damage to committed megakaryocyte progenitor cells was induced.

Intellectual outcome in children and adolescents with acute lymphoblastic leukaemia treated with chemotherapy alone: age- and sex-related differences.

One of the most relevant concerns in long-term survivors of paediatric acute lymphoblastic leukaemia (ALL) is the development of neuropsychological sequelae. The majority of the published studies report on patients treated with chemotherapy and prophylactic central nervous system (CNS) irradiation, little is known about the outcome of patients treated with chemotherapy-only regimens. Using the standardised clinical and neuropsychological instruments of the SPOG Late Effects Study, the intellectual performance of 132 paediatric ALL patients treated with chemotherapy only was compared to that of 100 control patients surviving from diverse non-CNS solid tumours. As a group, ALL and solid tumour survivors showed normal and comparable intellectual performances (mean global IQ 104.6 in both groups). The percentage of patients in the borderline range (global IQ between 70 and 85) was comparable and not higher as expected (10% cases and 13% controls, expected 16%). Only 2 (2%) of the former ALL and 1 (1%) of the solid tumour patients were in the range of mental retardation (global IQ<70). Former known risk factors described in children treated with prophylactic CNS irradiation, like a younger age at diagnosis of ALL and female gender, remained valid in chemotherapy-only treated patients. The abandonment of prophylactic CNS irradiation and its replacement by a more intensive systemic and intrathecal chemotherapy led to a reduction, but not the disappearance of late neuropsychological sequelae.

Immunofluorimetric and combined immunofluorimetric cytophotometric and autoradiographic investigations on human myeloma cells.

Bone marrow cells from patients with myeloma were reacted with FITC- and/or TRITC-conjugated anti-heavy chain sera and/or TRITC-conjugated anti-light chain sera. A fluorimeter with electronic setter control and short-term excitation was used for quantitative determination of FITC- and TRITC-fluorescence.

Proliferation of normal and leukemic TdT+ bone marrow cells in man.

Proliferative characteristics of lymphoid cells with detectable amounts of nuclear terminal deoxynucleotidyl transferase (TdT) in normal or regenerating non-leukemic bone marrow of children were assessed by sequential immunological and cytokinetic studies on single cells and compared to those of TdT+ cells in the bone marrow of children with non-T, non-B acute lymphoid leukemia (ALL) at diagnosis or in remission. The median labelling index (LI) of non-leukemic TdT+ cells was 21.3% (range 13.2 to 29.7%). The LI of non-leukemic TdT+Ia+ cells (range 18.2 to 32.6%) was always higher than that of non-leukemic TdT+Ia- cells (range 0 to 5.3%). Leukemic TdT+ bone marrow cells of children with previously untreated non-T, non-B ALL had a LI significantly (p less than 0.001) lower (median 6.1%; range 1.4 to 19.7%) than the LI of non-leukemic TdT+ cells. In patients with non-T, non-B ALL in remission neither the percentage of TdT+ cells nor the LI of TdT+ cells appeared to be useful for detecting early relapse.

Repression of nuclear lamin A and C gene expression in human acute lymphoblastic leukemia and non-Hodgkin's lymphoma cells.

The lamins A, B and C which are differentially expressed during ontogenesis and differentiation are karyoskeletal proteins forming a polymeric meshwork at the inner nuclear membrane. Using Northern blot analyses we investigated the steady state levels of the three lamin specific RNA transcripts in neoplastic cells derived from 16 untreated patients with acute lymphoblastic leukemia (ALL) or non-Hodgkin's lymphoma (NHL) and in ALL and NHL established cell lines. Whereas lamin B mRNA was present in all, lamin A and C transcripts were observed in none of the malignant cell samples except one of a common-ALL patient (precursor B-ALL, cytoplasmic mu chain negative). All three lamin mRNAs were detected in normal peripheral blood lymphocytes, however, only after mitogenic stimulation with concanavalin A. Our results provide evidence that expression of lamin A and C is repressed in neoplastic blast cells derived from patients with ALL or NHL and suggest that lamin A and C gene repression is not related to cell proliferation but might be relevant to the differentiated stages of the lymphoid cells in vivo.

Differential phosphorylation of lamin B2 in normal and leukemic cells.

Lamins constitute the nuclear lamina, which underlie the inner membrane of the cell nucleus. Phosphorylation of lamins is a key factor in the regulation of nuclear structure during the cell cycle and of gene transcription. Since an uncontrolled cell cycle and altered gene transcription are major characteristics of neoplasms, we looked for differences in lamin B2 phosphorylation between PBMC, ALL and AML cells. Using different lamin B2-specific antibodies, we detected two different lamin B2 species termed lamin B2 and B2A. Although phosphorylation of lamin B2 in leukemic cells was reminiscent of resting cells, the majority of ALL and AML samples showed significantly higher and more altered lamin B2A phosphorylation compared to PBMC. It remains to be elucidated which mechanism leads to these alterations and whether it could explain the extended G1-phase frequently observed in ALL cells.

The number of circulating CD34+ blood cells predicts the colony-forming capacity of leukapheresis products in children.

In children, only a few guidelines are available for optimizing peripheral blood progenitor cell (PBPC) harvesting. We analyzed by means of flow cytometry and clonogenic assays 60 harvest products obtained from 20 children by standardized leukapheresis after treatment with chemotherapy and CSF. In addition, 27 fresh blood samples obtained prospectively during the mobilization phase were studied. CFU-GM/kg significantly correlated with MNC/kg, CD34+ cells/kg and CD34+33- cells/kg in apheresis products (P < 0.001). In fresh blood samples, CFU-GM/ml significantly correlated with MNC/ml, CD34+ cells/ml and CD34+33- cells/ml (P < 0.001). The numbers of CD34+ cells/ml, CD34+33- cells/ml and MNC/ml in 19 blood samples taken prior to leukapheresis were compared with CFU-GM/kg harvested and thawed after cryopreservation applying multiple regression analysis with stepwise variable selection. The number of circulating CD34+ cells/ml prior to leukapheresis highly correlated with and was predictive for the number of collected CFU-GM/kg (P < 0.001). In addition, a significant correlation (P < 0.05) between the number of progenitor cells/kg reinfused and the time to myeloid and platelet recovery was found in children undergoing high-dose therapy. Our data indicate that a single leukapheresis will be sufficient to obtain a minimum number of 5 x 10(4) CFU-GM/kg if the pre-harvest number of circulating CD34+ cells is > or = 10(5)/ml. Thus, our results will help to optimize PBPC transplantation in children.

The problem of pediatric malignancies in the developing world.

In industralized countries, 70 to 80% of children with cancer can be cured by expensive interdisciplinary teamwork and by cooperation on the national or international level. As a result of poor socio-economic conditions, worldwide, less than 20% of the approximately 185,000 children developing cancer each year get adequate treatment. This is also true for 14 to 15 million children dying each year of diarrhea and infections, but while this number is decreasing, the number of children with cancer is increasing. In "middle income" developing countries, cancer is now a leading cause of death for children between 5 and 15 years of age. The "geography" of pediatric cancer reveals complex interactions between environment, lifestyle, and carcinogenesis. The "mapping" of pediatric cancer is far from complete, and the investigation of carcinogenetic interactions has barely started. A great challenge is the planning of pediatric oncology in developing countries. The goals are to improve the access to treatment and treatment results. Even if pediatric oncology has a low priority, the institution, in each country or large province, of at least one pediatric cancer unit may improve not only cancer treatment but medical care in general. By promoting education, organizing meetings, and setting minimum standards for training and care, international organizations can contribute to the development of pediatric oncology worldwide.

Sentinel practices in evaluating longer periods of care: quality of life and drug therapy of terminally ill persons in Lower Saxony (Germany).

STUDY OBJECTIVES: (1) To study the feasibility of using sentinel practice networks to evaluate longer periods of care. (2) To assess the quality of life and drug therapy of community dwelling terminally ill persons. DESIGN: Prospective longitudinal design with GPs in an existing sentinel practice network identifying "terminally ill" persons and recording the following data: age, sex, diagnoses, and ongoing drug therapy initially, time, place, duration, services, and drug changes for every contact, quality of life (HRCA-QL Index, Spitzer Index, uniscale), pain intensity and frequency on a weekly basis, and time and circumstances of death. SETTING: 26 GP practices in Lower Saxony, Germany. PATIENTS: 47 patients (age: mean 76 years, range 31 to 98; sex: 21 male, 26 female; diagnosis: 35 with cancer) with 582 contacts. Mean of recorded time before death was 70 days (median 50). MAIN RESULTS: Average number of physician-patient contacts increased from 0.7 a week three months before death to 2.4 in the final week. Quality of life decreased during that period (HRCA-QL Index: 5.1 to 0.8; Spitzer: 4.4 to 0.8; uniscale: 37 to 9). In the last week of life, no person was free of pain; analgetic therapy was "successful" in 57% of cases. CONCLUSIONS: (1) The sentinel practice approach is feasible for evaluating longer periods of care. The generalisibility, however, may be limited to certain subgroups. (2) The observed trends in quality of life, pain, and analgetic treatment should be compared with those in other settings and countries to identify the scope of care improvement.

Review of the methods of the US Environmental Protection Agency for bromate determination and validation of method 317.0 for disinfection by-product anions and low-level bromate.

In recent years several methods have been published by the United States Environmental Protection Agency (EPA) which specify bromate as a target analyte. The first of these was EPA Method 300.0. As technological improvements in ion chromatographic hardware have evolved and new detection techniques have been designed, method detection limits for bromate have been reduced and additional procedures have been written, including EPA Method 300.1, 321.8 and, most recently, EPA Method 317.0. An overview of the evolution of these bromate methods since 1989 is presented. The focus is specific to each of these respective procedures, highlighting method strengths, weaknesses, and addressing how these methods fit into EPA's regulatory agenda. In addition, performance data are presented detailing the joint EPA/American Society for Testing and Materials multilaboratory validation of EPA Method 317.0 for disinfection by-product anions and low-level bromate.

Performance evaluation of a method for the determination of bromate in drinking water by ion chromatography (EPA method 317.0) and validation of EPA method 324.0.

The potential carcinogenic nature of bromate has prompted global regulatory agencies, and industrial and academic institutions to publish several methods for the analysis of bromate in both drinking and bottled waters. The United States Environmental Protection Agency (EPA) has reported two methods capable of detecting bromate at or below the promulgated maximum contaminant level of 10.0 microg/l. These methods are EPA Method 300.1 and 317.0. Method 300.1 has been promulgated by EPA for compliance monitoring of bromate under Stage 1 of the Disinfectants/Disinfection By-Products Rule. Due to its sensitivity, selectivity and simplicity, Method 317.0 has been drafted and evaluated for potential use as a future compliance monitoring method. This manuscript describes the performance evaluation work with Method 317.0 and efforts completed at EPA's Technical Support Center that improved the sensitivity of Method 317.0, leading to the development of EPA Method 324.0