A microelectromechanically tunable asymmetric Fabry-Perot quantum well modulator at 1.55 microm

Placing a quantum well modulator in an asymmetric Fabry- Perot cavity enables significantly higher contrast ratios than are possible in a conventional surface-normal quantum well modulator. However, fixed-cavity asymmetric Fabry-Perot quantum well modulators require extremely precise and uniform crystal growth and are sensitive to small fluctuations in temperature or angle of incidence. Here, we experimentally demonstrate an InP-based microelectromechanically tunable asymmetric Fabry-Perot quantum well modulator that operates in the optical C-band. By actuating a suspended InGaAlAs reflector, the cavity mode can be perfectly matched to the appropriate quantum well absorption wavelength. The devices exhibit contrast ratios over 30 (15 dB) at 8 volts quantum well bias and modulation speeds of 1 MHz.

Selective DNA-mediated assembly of gold nanoparticles on electroded substrates

Motivated by the technological possibilities of electronics and sensors based on gold nanoparticles (Au NPs), we investigate the selective assembly of such NPs on electrodes via DNA hybridization. Protocols are demonstrated for maximizing selectivity and coverage using 15mers as the active binding agents. Detailed studies of the dependences on time, ionic strength, and temperature are used to understand the underlying mechanisms and their limits. Under optimized conditions, coverage of Au NPs on Au electrodes patterned on silicon dioxide (SiO2) substrates was found to be approximately 25-35%. In all cases, Au NPs functionalized with non-complementary DNA show no attachment and essentially no nonspecific adsorption is observed by any Au NPs on the SiO2 surfaces of the patterned substrates. DNA-guided assembly of multilayers of NPs was also demonstrated and, as expected, found to further increase the coverage, with three deposition cycles resulting in a surface coverage of approximately 60%.

Low-loss suspended quantum well waveguides

We have used surface micromachining to fabricate suspended InGaAs/InGaAsP quantum well waveguides that are supported by lateral tethers. The average measured TE propagation loss in our samples is 4.1 dB/cm, and the average measured TE loss per tether pair is 0.21 dB. These measurements are performed at wavelengths in the optical L-band, just 125 nm below the quantum well band gap.

An optimization-based design procedure for asymmetric bidirectional associative memories

In this letter, we consider the problem of designing asymmetric bidirectional associative memories (ABAM). Based on a newly derived theorem for the ABAM model, we propose an optimization-based design procedure for obtaining an ABAM that can store given bipolar vector pairs with certain error correction properties. Our design procedure consists of generalized eigenvalue problems, which can be efficiently solved by recently developed interior point methods. The validity of the proposed method is illustrated by a design example.

Mechanisms of melanogenesis inhibition by 2,5-dimethyl-4-hydroxy-3(2H)-furanone

BACKGROUND

Increased production and accumulation of melanin is characteristic of a large number of skin diseases, including acquired hyperpigmentation such as melasma, postinflammatory melanoderma and solar lentigo. Thus, there is a increasing need for the development of depigmenting agents.

OBJECTIVES

To evaluate the depigmenting capacity of 2,5-dimethyl-4-hydroxy-3(2H)-furanone (DMHF) and to elucidate the mechanisms by which it inhibits alpha-melanocyte-stimulating hormone (alpha-MSH)-induced melanogenesis in B16 melanoma cells in vitro.

METHODS

Several experiments were performed in B16 melanoma cells. We studied melanin content, tyrosinase activity and cAMP production, and performed cAMP response element (CRE) luciferase reporter assay and Western blots for proteins involved in melanogenesis.

RESULTS

The melanin content and tyrosinase activity induced by alpha-MSH were inhibited significantly by DMHF. To clarify the mechanism of the depigmenting property of DMHF, we examined the involvement of DMHF in cAMP signalling induced by alpha-MSH. In CRE luciferase reporter assay, CRE reporter activation induced by alpha-MSH was inhibited by DMHF. Additionally, although DMHF did not inhibit cAMP production by alpha-MSH, both CRE binding protein (CREB) phosphorylation and the reduction of glycogen synthase kinase-3beta phosphorylation by alpha-MSH were blocked by DMHF. These data suggest that DMHF inhibits the downstream step of cAMP production induced by alpha-MSH, consequently inhibiting melanogenesis. This suggestion was further confirmed by the fact that the increased production levels of microphthalmia-associated transcription factor, tyrosinase and tyrosinase-related protein-1 induced by alpha-MSH were all reduced by DMHF in B16 melanoma cells.

CONCLUSIONS

Our study shows that DMHF inhibits alpha-MSH-induced melanogenesis by suppressing CREB phosphorylation, which is induced by protein kinase A, and suggests that DMHF may be an effective inhibitor of hyperpigmentation.

Intratumoral mRNA levels predict clinical outcome in patients with metastatic colorectal cancer treated in a prospective clinical trial with 5-FU and oxaliplatin

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Background: 5-flurouracil (5-FU) and Oxaliplatin-based therapy is one of the most frequently used combinations in the treatment of advanced colorectal cancer (CRC). There are no validated and established predictive factors for clinical outcome following 5-FU/Oxaliplatin treatment. We had shown an association between intratumoral mRNA levels of TS and ERCC1 involved in 5-FU metabolism and DNA repair, respectively, and survival to 5-FU/Oxaliplatin chemotherapy in advanced CRC in a retrospective study. Now we investigated whether intratumoral mRNA levels of these two genes and others involved in 5-FU metabolism (DPD, TP, dUTPase), DNA repair (ERCC2, XRCC1), angiogenesis (COX-2, EGFR, IL-8, PLA2), and drug detoxification (GSTP-1) predict the clinical outcome of patients with CRC in a prospectively designed biomarker study. Methods: 85 patients with metastatic CRC treated with second-line 5-FU/Oxaliplatin from the prospective trial were included. mRNA levels of 12 genes were assessed from paraffin- embedded tissue samples using laser capture microdissection and quantitative Real-time PCR. Overall survival (OS) was the primary endpoint. Progression-free survival (PFS), response, and toxicity were the secondary endpoints. Results: There were 40 women and 45 men (median age 60 years; range 29–87), median survival of 9.7 ms, median PFS of 4.2 ms, CR in 1 (1%) patient, PR in 15 (18%), SD in 36 (43%) and PD in 32 (38%) patients. High intratumoral mRNA levels of PLA2, TP, GSPTP-1 and low mRNA levels of COX-2 were each significantly associated with shorter OS (P≤0.05, log-rank test). There was a trend in the association between high mRNA levels of PLA2 and shorter PFS (P=0.08). In addition, high mRNA levels of XRCC1 and IL-8 were each significantly associated with high risk of cumulative grade 3+ toxicity (P≤0.05). No significant association was found between mRNA levels and response to 5-FU/Oxaliplatin. Conclusions: This study suggests that mRNA levels of PLA2, TP, GSTP-1, COX-2, XRCC1, and IL-8 may be useful to predict the outcome of patients with metastatic CRC with second-line 5-FU/Oxaliplatin chemotherapy. These findings should be validated with future basic sciences studies and prospective clinical trials.

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N-3 fatty acids inhibit vascular calcification via the p38-mitogen-activated protein kinase and peroxisome proliferator-activated receptor-gamma pathways

Fish oil supplementation is associated with lower risk of coronary artery disease in humans, and it has been shown to reduce ectopic calcification in an animal model. However, whether N-3 fatty acids, active ingredients of fish oil, have direct effects on calcification of vascular cells is not clear. In this report, we investigated the effects of eicosapentaenoic acid and docosahexaenoic acid (DHA) on osteoblastic differentiation and mineralization of calcifying vascular cells (CVCs), a subpopulation of bovine aortic medial cells that undergo osteoblastic differentiation and form calcified matrix in vitro. Results showed that N-3 fatty acids inhibited alkaline phosphatase (ALP) activity and mineralization of vascular cells, suggesting that they directly affect osteoblastic differentiation in vascular cells. By Western blot analysis, DHA activated p38-mitogen-activated protein kinase (MAPK) but not extracellular-regulated kinase (ERK) or Akt. An inhibitor of p38-MAPK partially reversed the inhibitory effects of DHA on osteoblastic differentiation and mineralization. Transient transfection experiments showed that DHA also activated peroxisome proliferator-activated receptor-gamma (PPAR-gamma). Both p38-MAPK activator and PPAR-gamma agonists reproduced the inhibitory effects of DHA on CVC mineralization. Pretreatment with DHA also inhibited interleukin-6-induced ALP activity and mineralization. Together, these results suggest that N-3 fatty acids directly inhibit vascular calcification, and that the inhibitory effects are mediated by the p38-MAPK and PPAR-gamma pathways.

Shape resonance omni-directional terahertz filters with near-unity transmittance

Terahertz transmission filters have been manufactured by perforating metal films with various geometric shapes using femtosecond laser machining. Two dimensional arrays of square, circular, rectangular, c-shaped, and epsilon-shaped holes all support over 99% transmission at specific frequencies determined by geometric shape, symmetry, polarization, and lattice constant. Our results show that plasmonic structures with different geometric shaped holes are extremely versatile, dependable, easy to control and easy to make terahertz filters.

Lemierre’s syndrome

We report a case of Lemierre’s syndrome complicated by an epidural abscess. This manifestation of Lemierre’s syndrome has not been described previously.

Neural prosthesis in the wake of nanotechnology: controlled growth of neurons using surface nanostructures

Neural prosthesis has been successfully applied to patients with motional or sensory disabilities for clinical purpose. To enhance the performance of the neural prosthetic device, the electrodes for the biosignal recording or electrical stimulation should be located in closer proximity to target neurons than they are now. Instead of revising the prior implanting surgery to improve the electrical contact of neurons, we propose a technique that can bring the neurons closer to the electrode sites. A new method is investigated that can control the direction of neural cell growth using surface nanostructures. We successfully guide the neurons to the position of the microelectrodes by providing a surface topographical cue presented by the surface nanostructure on a photoresponsive polymer material. Because the surface structure formed by laser holography is reversible and repeatable, the geometrical positioning of the neurons to microelectrodes can be adjusted by applying laser treatment during the surgery for the purpose of improving the performance of neural prosthetic device.

Optical pumping of the electronic and nuclear spin of single charge-tunable quantum dots

We present a comprehensive examination of optical pumping of spins in individual GaAs quantum dots as we change the net charge from positive to neutral to negative with a charge-tunable heterostructure. Negative photoluminescence polarization memory is enhanced by optical pumping of ground state electron spins, which we prove with the first measurements of the Hanle effect on an individual quantum dot. We use the Overhauser effect in a high longitudinal magnetic field to demonstrate efficient optical pumping of nuclear spins for all three charge states of the quantum dot.

Continuous biological ferrous iron oxidation in a submerged membrane bioreactor

Microbial oxidation of ferrous iron may be available alternative method of producing ferric iron, which is a reagent used for removal of H2S from biogas. In this study, a submerged membrane bioreactor (MBR) system was employed to oxidize ferrous iron to ferric iron. In the submerged MBR system, we could keep high concentration of iron-oxidizing bacteria and high oxidation rate of ferrous iron. There was membrane fouling caused by chemical precipitates such as K-jarosite and ferric phosphate. However, a strong acidity (pH 1.75) of solution and low ferrous iron concentration (below 3000 mg/I) significantly reduced the fouling of membrane module during the bioreactor operation. A fouled membrane module could be easily regenerated with a 1 M of sulfuric acid solution. In conclusion, the submerged MBR could be used for high-density culture of iron-oxidizing bacteria and for continuous ferrous iron oxidation. As far as our knowledge concerns, this is the first study on the application of a submerged MBR to high acidic conditions (below pH 2).