Optical pumping of quantum dot micropillar lasers.

Arrays of quantum dot micropillar lasers are an attractive technology platform for various applications in the wider field of nanophotonics. Of particular interest is the potential efficiency enhancement as a consequence of cavity quantum electrodynamics effects, which makes them prime candidates for next generation photonic neurons in neural network hardware. However, particularly for optical pumping, their power-conversion efficiency can be very low. Here we perform an in-depth experimental analysis of quantum dot microlasers and investigate their input-output relationship over a wide range of optical pumping conditions. We find that the current energy efficiency limitation is caused by disadvantageous optical pumping concepts and by a low exciton conversion efficiency. Our results indicate that for non-resonant pumping into the GaAs matrix (wetting layer), 3.4% (0.6%) of the optical pump is converted into lasing-relevant excitons, and of those only 2% (0.75%) provide gain to the lasing transition. Based on our findings, we propose to improve the pumping efficiency by orders of magnitude by increasing the aluminium content of the AlGaAs/GaAs mirror pairs in the upper Bragg reflector.

Triggered high-purity telecom-wavelength single-photon generation from p-shell-driven InGaAs/GaAs quantum dot.

We report on the experimental demonstration of triggered single-photon emission at the telecom O-band from In(Ga)As/GaAs quantum dots (QDs) grown by metal-organic vapor-phase epitaxy. Micro-photoluminescence excitation experiments allowed us to identify the p-shell excitonic states in agreement with high excitation photoluminescence on the ensemble of QDs. Hereby we drive an O-band-emitting GaAs-based QD into the p-shell states to get a triggered single photon source of high purity. Applying pulsed p-shell resonant excitation results in strong suppression of multiphoton events evidenced by the as measured value of the second-order correlation function at zero delay of 0.03 (and ~0.005 after background correction).

Size analysis of nanoparticles extracted from W/O emulsions.

Nanosized particles are frequently used in many different applications, especially TiO2 nanoparticles as physical filters in sunscreens to protect the skin from UV radiation. However, concerns have arisen about possible health issues caused by nanoparticles and therefore, the assessment of the occurrence of nanoparticles is important in pharmaceutical and cosmetic formulations. In a previous work of our group, a method was presented to extract nanoparticles from O/W emulsions. But to respond to the needs of dry and sensitive skin, sunscreens of the water-in-oil emulsion type are available. In these, assessment of present nanoparticles is also an important issue, so the present study offers a method for extracting nanoparticles from W/O emulsions. Both methods emanate from the same starting point, which minimizes both effort and cost before the beginning of the assessment. By addition of NaOH pellets and centrifugation, particles were extracted from W/O emulsions and measured for their size and surface area by laser diffraction. With the simple equation Q=A/S a distinction between nanoparticles and microparticles was achieved in W/O emulsions, even in commercially available samples. The present method is quick and easy to implement, which makes it cost-effective.

Functional involvement of a deoxy-D-xylulose 5-phosphate reductoisomerase gene harboring locus of Synechococcus leopoliensis in isoprenoid biosynthesis.

The present work aimed to proof the functionality of the non-mevalonate pathway in cyanobacteria. It was intended to isolate the 1-deoxy-D-xylulose 5-phosphate (DXP) reductoisomerase gene (dxr), as this gene encodes the enzyme which catalyzes a pathway-specific, indicative step of this pathway. For this purpose, a segment of dxr was amplified from Synechococcus leopoliensis SAUG 1402-1 DNA via PCR using oligonucleotides for conserved regions. Subsequent hybridization screening of a genomic cosmid library of S. leopoliensis with the PCR segment led to the identification of a 26. 5 kbp locus on which a dxr homologous gene and two adjacent open reading frames organized in one operon were localized by DNA sequencing. The functionality of the gene was demonstrated expressing the gene in Escherichia coli and using the purified gene product in a photometrical NADPH dependent test based on the substrate DXP generating system. While the content of one of the central intermediates of the isoprenoid biosynthesis (dimethylallyl diphosphate=DMADP) was significantly (P

A Synechococcus leopoliensis SAUG 1402-1 operon harboring the 1-deoxyxylulose 5-phosphate synthase gene and two additional open reading frames is functionally involved in the dimethylallyl diphosphate synthesis.

Experiments have been performed to prove the existence and the functionality of the novel mevalonate independent 1-deoxyxylulose 5-phosphate isoprenoid biosynthesis pathway in cyanobacteria. For this purpose, a segment of the 1-deoxyxylulose 5-phosphate synthase gene (dxs) was amplified from Synechococcus leopoliensis SAUG 1402-1 DNA via PCR using oligonucleotides for conserved regions of dxs. Subsequent hybridization screening of a genomic cosmid library of S. leopoliensis with this segment has led to the identification of an 18.7 kbp segment of the S. leopoliensis genome on which a dxs homologous gene and two adjacent open reading frames organized in one operon could be localized by DNA sequencing. The three genes of the operon were separately expressed in Escherichia coli, proving that the identified cyanobacterial dxs is functionally involved in the formation of dimethylallyl diphosphate, one basic intermediate of isoprenoid biosynthesis.

Results of a standardized protocol for sentinel node imaging in breast cancer with Tc-99m labeled nanocolloidal albumin.

AIM: Of this study was to evaluate the results of a standardized protocol for sentinel node (SN) detection in breast cancer using Tc-99m labeled nanocolloidal albumin and a combined intra- and subdermal injection technique. METHODS: One hundred and fifty-five women with proven breast cancer (disease stages Tis-T2) were included. Four injections of 10 to 15 MBq of Tc-99m nanocolloid in 0.1 ml physiologic saline were administered intra- and subdermally at the 3, 6, 9 and 12 o'clock positions in the skin overlying the tumor. Planar scintigraphic images in lateral and anterior projections were obtained once between 2.5 and 18 hours after tracer administration. Guided by a gamma probe, all radioactive lymph nodes in the axilla were resected, then complete dissection followed. RESULTS: In 151 of the 155 women (97.4%), nodal tracer uptake (range 1-7 foci, average 2.2) was scintigraphically revealed. In one of these cases, drainage was only to the internal mammary lymphatic chain. Three of the 4 women with detection failure presented with histologically proven tumor infiltration of the lymphatics and axillary involvement. In 49 of the patients with visualized axillary lymph nodes (32.7%), at least one SN was metastatic. In 21 cases, this SN was the only positive node. The remaining 101 patients with negative SN included 4 cases with axillary involvement. The sensitivity of the SN with respect to the histological status of the entire axilla was thus 92.5%, the negative predictive value was 96.0%. The overall accuracy of the method was 97.3%. There was a significant difference between the number of totally detected radioactive nodes in the groups with and without nodal metastases (3.49 vs. 2.57, p < 0.01). CONCLUSION: The described protocol represents an easy reproducible and reliable method for SN detection in breast cancer that additionally allows flexible timing of surgery. Further, we found evidence that the number of scintigraphically visualized nodes also reflects the histological status of the axilla.

Lymphoscintigraphic sentinel node imaging and gamma probe detection in breast cancer with Tc-99m nanocolloidal albumin: results of an optimized protocol.

PURPOSE: The purpose of this study was to aid in the standardization of lymphoscintigraphy for detecting the sentinel node (SN) in breast cancer using Tc-99m-labeled nanocolloidal albumin. MATERIALS AND METHODS: One hundred twenty-three women with proved breast cancer were enrolled. Four injections of 10 to 15 MBq (0.27 to 0.41 mCi) Tc-99m nanocolloid in 0.1 ml physiologic saline were administered intra- and subdermally at the margin of the skin overlying the tumor. Planar scintigraphic images in the lateral and anterior projections were obtained 2.5 to 18 hours after tracer administration. With a gamma probe used as a guide, all radioactive lymph nodes in the axilla were resected. Complete dissection then followed. RESULTS: In 116 of the 123 (94%) women, axillary nodal tracer uptake was revealed. Six of the 7 women in whom detection failure occurred had histologically proved tumor infiltration of the lymphatics and axillary involvement. In 36 (31%) of the patients with visualized lymph nodes, the SN was metastatic. The remaining 80 patients with negative SN included three cases with axillary involvement. The sensitivity of the SN with respect to the histologic status of the entire axilla thus was 92.3%, and the negative predictive value was 96.3%. The overall accuracy of the method was 97.4%. The number of hot nodes in women with and without axillary involvement was significantly different. CONCLUSIONS: The described protocol represents an easily reproduced and reliable method for SN detection in breast cancer. Furthermore, the number of visualized axillary nodes reflects the histologic status of the axilla.

Impact of the axillary nodal status on sentinel node mapping in breast cancer and its relevance for technical proceeding.

OBJECTIVE: The aim of this study is to analyze whether the axillary status influences the lymphatic mapping procedure in malignant breast disease and whether clinically relevant consequences for the technique of Sentinel Node (SN) biopsy may be drawn from this information. MATERIALS AND METHODS: SN biopsy was performed in 150 consecutive patients using a combination of the radioguided and the blue-dye technique. Axillary status was compared with the number of detected nodes. In cases of numerous nodes with tracer uptake, the radioactivity of each radiolabeled node was measured separately in a dose calibrator. We analyzed whether an increased tracer uptake could possibly indicate a 'true' or 'dominant' SN. Blue dye uptake was registered and compared with radioactivity. The findings were related to the histologic results. RESULTS: In patients with a positive axillary status, significantly more radiolabeled nodes were detected than in node negative patients (median 3 vs. 2; p < 0.001). In 54/86 patients with numerous SNs a 'dominant' node with at least twice the radioactivity than other marked nodes could be identified (62.8%). From 26 cases with axillary involvement, 20 patients (76.9%) were identified by the 'dominant' and the remaining six women (23.1%) by others than the seemingly leading SN. CONCLUSION: Axillary lymph node involvement influences the drainage pattern in breast cancer. Patients with numerous SNs have an increased risk of axillary involvement. A high tracer uptake does not permit the identification of a 'true' SN. A lack of surgical accuracy may lead to pitfalls if the axilla is not screened carefully for all radioactive nodes.

Concurrent activation of a novel putative transforming gene, myeov, and cyclin D1 in a subset of multiple myeloma cell lines with t(11;14)(q13;q32).

Through the application of the NIH/3T3 tumorigenicity assay to DNA from a gastric carcinoma, we have identified a novel transforming gene, designated myeov (myeloma overexpressed gene in a subset of t[11;14]-positive multiple myelomas). Sequence analyses did not reveal any homology with sequences present in the GenBank, except the deduced protein structure predicts a transmembrane localization. Myeov was mapped to chromosome 11q13 and localized by DNA fiber fluorescence in situ hybridization (FISH) 360-kilobase (kb) centromeric of cyclin D1. In 3 of 7 multiple myeloma (MM) cell lines with a t(11;14)(q13;q32) and cyclin-D1 overexpression, Northern blot analysis revealed overexpression of myeov as well. In all 7 cell lines, the translocation breakpoint was mapped within the 360-kb region between myeov and cyclin D1. DNA fiber FISH with a contig of probes covering the constant region of the immunoglobulin heavy chain (IgH) revealed that exclusively in the 3 myeov-overexpressing cell lines (KMS-12, KMS-21, and XG-5), either the 5' E(mu) enhancer or the most telomeric 3' Ealpha enhancer was juxtaposed to myeov. Although cyclin D1 overexpression represents a characteristic feature of all MM cell lines with t(11;14), our results demonstrate aberrant expression of a second putative oncogene in a subset of these cases, due to juxtaposition to IgH enhancers. The clinical relevance of this dual activation remains to be elucidated. (Blood. 2000;95:2691-2698)