High-efficiency grating coupler for an ultralow-loss Si3N4-based platform.

Integrated silicon nitride waveguides of 100 nm height can achieve ultralow propagation losses below 0.1 dB/cm at the 1550 nm wavelength band but lack the scattering strength to form efficient grating couplers. An enhanced grating coupler design based on an amorphous silicon layer on top of silicon nitride is proposed and demonstrated to improve the directionality of the coupler. The fabrication process is optimized for a self-alignment process between the amorphous silicon and silicon nitride layers without increasing waveguide losses. Experimental coupling losses of 5 dB and a 3 dB bandwidth of 75 nm are achieved with both regular and focusing designs.

Ultra-sensitive refractive index sensor using CMOS plasmonic transducers on silicon photonic interferometric platform.

Optical refractive-index sensors exploiting selective co-integration of plasmonics with silicon photonics has emerged as an attractive technology for biosensing applications that can unleash unprecedented performance breakthroughs that reaps the benefits of both technologies. However, towards this direction, a major challenge remains their integration using exclusively CMOS-compatible materials. In this context, herein, we demonstrate, for the first time to our knowledge, a CMOS-compatible plasmo-photonic Mach-Zehnder-interferometer (MZI) based on aluminum and Si3N4 waveguides, exhibiting record-high bulk sensitivity of 4764 nm/RIU with clear potential to scale up the bulk sensitivity values by properly engineering the design parameters of the MZI. The proposed sensor is composed of Si3N4 waveguides butt-coupled with an aluminum stripe in one branch to realize the sensing transducer. The reference arm is built by Si3N4 waveguides, incorporating a thermo-optic phase shifter followed by an MZI-based variable optical attenuation stage to maximize extinction ratio up to 38 dB, hence optimizing the overall sensing performance. The proposed sensor exhibits the highest bulk sensitivity among all plasmo-photonic counterparts, while complying with CMOS manufacturing standards, enabling volume manufacturing.

Four-Frequency Solution in a Magnetohydrodynamic Couette Flow as a Consequence of Azimuthal Symmetry Breaking.

The occurrence of magnetohydrodynamic quasiperiodic flows with four fundamental frequencies in differentially rotating spherical geometry is understood in terms of a sequence of bifurcations breaking the azimuthal symmetry of the flow as the applied magnetic field strength is varied. These flows originate from unstable periodic and quasiperiodic states with broken equatorial symmetry, but having fourfold azimuthal symmetry. A posterior bifurcation gives rise to twofold symmetric quasiperiodic states, with three fundamental frequencies, and a further bifurcation to a four-frequency quasiperiodic state which has lost all the spatial symmetries. This bifurcation scenario may be favored when differential rotation is increased and periodic flows with m-fold azimuthal symmetry, m being a product of several prime numbers, emerge at sufficiently large magnetic field.

Plasmonics co-integrated with silicon nitride photonics for high-sensitivity interferometric biosensing.

We demonstrate a photonic integrated Mach-Zehnder interferometric sensor, utilizing a plasmonic stripe waveguide in the sensing branch and a photonic variable optical attenuator and a phase shifter in the reference arm to optimize the interferometer operation. The plasmonic sensor is used to detect changes in the refractive index of the surrounding medium exploiting the accumulated phase change of the propagating Surface-Plasmon-Polariton (SPP) mode that is fully exposed in an aqueous buffer solution. The variable optical attenuation stage is incorporated in the reference Si3N4 branch, as the means to counter-balance the optical losses introduced by the plasmonic branch and optimize interference at the sensor output. Bulk sensitivity values of 1930 nm/RIU were experimentally measured for a Mach Zehnder Interferometer (MZI) with a Free Spectral Range of 24.8 nm, along with extinction ratio of more than 35 dB, demonstrating the functional benefits of the co-integration of plasmonic and photonic waveguides.

CMOS plasmonics in WDM data transmission: 200 Gb/s (8 × 25Gb/s) transmission over aluminum plasmonic waveguides.

We demonstrate wavelength-division-multiplexed (WDM) 200 Gb/s (8 × 25 Gb/s) data transmission over 100 µm long aluminum (Al) surface-plasmon-polariton (SPP) waveguides on a Si3N4 waveguide platform at telecom wavelengths. The Al SPP waveguide was evaluated in terms of signal integrity by performing bit-error-rate (BER) measurements that revealed error-free operation for all eight 25 Gb/s non-return-to-zero (NRZ) modulated data channels with power penalties not exceeding 0.2 dB at 10-9. To the best of our knowledge, this is the first demonstration of WDM enabled data transmission over complementary-metal-oxide-semiconductor (CMOS) SPP waveguides fueling future development of CMOS compatible plasmo-photonic devices for on-chip optical interconnections.

Characterization of CMOS metal based dielectric loaded surface plasmon waveguides at telecom wavelengths.

Dielectric loaded surface plasmon waveguides (DLSPPWs) comprised of polymer ridges deposited on top of CMOS compatible metal thin films are investigated at telecom wavelengths. We perform a direct comparison of the properties of copper (Cu), aluminum (Al), titanium nitride (TiN) and gold (Au) based waveguides by implementing the same plasmonic waveguiding configuration for each metal. The DLSPPWs are characterized by leakage radiation microscopy and a fiber-to-fiber configuration mimicking the cut-back method. We introduce the ohmic loss rate (OLR) to analyze quantitatively the properties of the CMOS metal based DLSPPWs relative to the corresponding Au based waveguides. We show that the Cu, Al and TiN based waveguides feature extra ohmic loss compared to Au of 0.027 dB/µm, 0.18 dB/µm and 0.52 dB/µm at 1550nm respectively. The dielectric function of each metal extracted from ellipsometric spectroscopic measurements is used to model the properties of the DLSP-PWs. We find a fairly good agreement between experimental and modeled DLSPPWs properties except for Al featuring a large surface roughness. Finally, we conclude that TiN based waveguides sustaining intermediate effective index (in the range 1.05-1.25) plasmon modes propagate over very short distances restricting the the use of those modes in practical situations.

Generation of 64 GBd 4ASK signals using a silicon-organic hybrid modulator at 80°C.

We demonstrate a silicon-organic hybrid (SOH) Mach-Zehnder modulator (MZM) generating four-level amplitude shift keying (4ASK) signals at symbol rates of up to 64 GBd both at room temperature and at an elevated temperature of 80°C. The measured line rate of 128 Gbit/s corresponds to the highest value demonstrated for silicon-based MZM so far. We report bit error ratios of 10-10 (64 GBd BPSK), 10-5 (36 GBd 4ASK), and 4 × 10-3 (64 GBd 4ASK) at room temperature. At 80 °C, the respective bit error ratios are 10-10, 10-4, and 1.3 × 10-2. The high-temperature experiments were performed in regular oxygen-rich ambient atmosphere.

Mean-field model of the von Kármán sodium dynamo experiment using soft iron impellers.

It has been observed that dynamo action occurs in the von-Kármán-Sodium (VKS) experiment only when the rotating disks and the blades are made of soft iron. The purpose of this paper is to numerically investigate the role of soft iron in the VKS dynamo scenario. This is done by using a mean-field model based on an axisymmetric mean flow, a localized permeability distribution, and a localized α effect modeling the action of the small velocity scales between the blades. The action of the rotating blades is modeled by an axisymmetric effective permeability field. Key properties of the flow giving to the numerical magnetic field a geometric structure similar to that observed experimentally are identified. Depending on the permeability of the disks and the effective permeability of the blades, the dynamo that is obtained is either oscillatory or stationary. Our numerical results confirm the leading role played by the ferromagnetic impellers. A scenario for the VKS dynamo is proposed.

Generation of laser-driven higher harmonics from grating targets.

The first experimental evidence of the higher-order harmonic radiation generated by periodically modulated targets (gratings) irradiated by relativistic, ultrashort (<30 fs), high intensity [Iλ(2)=10(20) (W/cm(2)) µm(2)] laser pulse is presented. The interference effects on the grating surface lead to the emission of high harmonics up to 45th order along the target surface when the laser beam is focused onto a grating target close to normal incidence (5°). By means of numerical simulations we demonstrate the possibility of controlling the composition of the higher harmonic spectrum and we prove the influence of the laser pulse parameters in the interaction area (laser focusing and wavefront curvature) on the emission angle of a certain high harmonic order.

Time-resolved characterization of the formation of a collisionless shock.

We report on the temporally and spatially resolved detection of the precursory stages that lead to the formation of an unmagnetized, supercritical collisionless shock in a laser-driven laboratory experiment. The measured evolution of the electrostatic potential associated with the shock unveils the transition from a current free double layer into a symmetric shock structure, stabilized by ion reflection at the shock front. Supported by a matching particle-in-cell simulation and theoretical considerations, we suggest that this process is analogous to ion reflection at supercritical collisionless shocks in supernova remnants.

Health-related quality of life in adult survivors after paediatric allo-SCT.

Fifty-three adults who had received SCT as children responded to questionnaires on health-related quality of life (HRQoL) (Swedish HRQoL survey (SWED-QUAL)), sense of coherence (SOC), anxiety and depression (HAD) and a health and symptom inventory. Late effects were classified following the Common Terminology Criteria for Adverse Events (CTCAE) v. 3.0. HRQoL was below norm in 9 of 13 SWED-QUAL domains. Poorest domains (P<0.001) were satisfaction with physical health, general health, partner relations and sexual function, whereas emotional wellbeing and satisfaction with family life were on par with the norm. Older age, time elapsed post-SCT and fewer self-reported symptoms correlated with better HRQoL. Unfavourable late effect scores had no or limited impact, whereas age at SCT or TBI did not adversely affect HRQoL. Most subjects were well subjectively and objectively, whereas 24% had more complicated late effects. The median Karnofsky score was 90, 13% of subjects having scores below 80. In total, 53% reported pain, whereas 42.5% had memory and concentration problems. Anxiety and/or depression, reported by 35%, were associated with lower HRQoL and SOC ratings. Overall, 55% reported infertility and expressed difficulty with this. To conclude, childhood SCT did not negatively affect overall health for most of these adult long-term survivors, although poorer HRQoL with psychological and cognitive problems are common.

Norman R. James F.F.A.R.A.C.S., a pioneer of high quality anaesthesia in Australia.

Dr Norman R. James was a multi-talented, highly accomplished clinician, teacher and innovator broadly recognized on three continents. In the United Kingdom, he served in London's Emergency Medical Service during World War II and was dubbed "England's foremost exponent of regional anaesthesia". In his native land, he was the first Director of Anaesthetics at The Royal Melbourne Hospital with many innovations to his credit including a serious effort to reform anaesthetic practice in Australia. Dr M. T. "Pepper" Jenkins, the charismatic founder of anesthesiology at the University of Texas Southwestern Medical School, recruited him to Dallas in 1960, where he taught the art and science of anesthesiology at Parkland Memorial Hospital until his retirement in 1974. He died in 1987 and is buried in Winnsboro, Texas. A brief story of his life and career follows.

Ketamine suppresses endotoxin-induced NF-kappaB expression.

PURPOSE: Ketamine reduces endotoxin-induced production of proinflammatory cytokines, including tumour necrosis factor-alpha (TNF), in several types of inflammatory cells, including monocytes and macrophages. Transcription of the genes that encode production of these proinflammatory cytokines is regulated by nuclear factor-kappa B (NF-kappaB). Cytoplasmic B protein is activated by endotoxin (LPS) as well as by TNF, allowing B protein to migrate into the cell nucleus to activate gene transcription for these inflammatory mediators. Because NF-kappaB is likely involved in brain injury and inflammatory neurodegenerative disease, such as multiple sclerosis, we examined whether ketamine inhibits LPS-induced activation of NF-kappaB in human glioma cells in vitro and intact mouse brain cells in vivo. METHODS: Endotoxin-induced NF-kappaB expression in both the human glioma cells in vitro and the intact mouse brain cells in vivo was determined by electrophoretic mobility shift assays (EMSA) of nuclear extracts and measurement of NF-kappaB expression by densitometry. Endotoxin was injected intracerebroventricularly in vivo and intact brain was harvested. Klenow fragment labeling was used to identify NF-kappaB protein for both the in vivo and vitro experiments. RESULTS: Endotoxin treatment increased NF-kappaB expression (P < 0.05) both in vivo and vitro compared with control (untreated) cells. Ketamine suppressed endotoxin-induced neuronal NF-kappaB activation in a dose-dependent manner (P < 0.05, except for the 10(-5) M concentration in vitro) both in vivo and vitro. CONCLUSION: Ketamine inhibits endotoxin-induced NF-kappaB expression in brain cells in vivo and vitro and it is suggested that this may have implications in the neuroprotective effects of ketamine reported by other investigators.

Use of an EEG-bispectral closed-loop delivery system for administering propofol.

Closed-loop control of propofol delivery was instituted in three patients who received a propofol infusion as part of: (Case 1) general "balanced" anesthesia, (Case 2) total intravenous anesthesia, and (Case 3) monitored anesthesia care. The bispectral index was the input variable used in a proportioned, integral and differential controller to determine the infusion rate of propofol required to maintain a stable level of hypnosis (Cases 1 and 2) or sedation (Case 3). This feedback control system provided intraoperative hemodynamic stability and a prompt recovery from the sedative-hypnotic effects of propofol.

Induction of tumor peptide-specific cytotoxic T cells under serum-free conditions by mature human dendritic cells.

Tumor vaccination strategies using antigen-pulsed dendritic cells (DC) are currently under development. We established an in vitro system using cultured DC from HLA-typed volunteers for the induction of tumor peptide-specific CD8+ T cells. The strength and specificity of the resulting CTL responses were investigated. For stimulation of syngeneic CD8+ T cells two well-defined DC populations were generated: CD1a+ immature DC cultured in the presence of GM-CSF and IL-4 and mature CD83+ DC generated by additional stimulation with a cytokine cocktail. Stimulations were performed under serum-free conditions and in the absence of exogenous cytokines. Analysis of T cell responses showed that mature DC, but not immature DC, were able to induce the expansion of syngeneic tumor peptide-specific CD8+ T cells. Priming of CD8+ T cells with peptide-pulsed mature DC rapidly increased the frequency of antigen-specific T cells (ELISPOT technique). T cells induced by mature DC showed strong antigen-specific cytotoxicity in 51Cr-release assays whereas no antigen-specific cytotoxicity was detectable in CTL generated by immature DC. These data show that terminally differentiated mature DC are necessary for the induction of tumor antigen-specific CTL responses.

Efficient transduction of mature CD83+ dendritic cells using recombinant adenovirus suppressed T cell stimulatory capacity.

We have developed a culture method for the foreign serum-free generation of highly immunostimulatory, CD83+ human dendritic cells (DC). In this study, we evaluated the feasibility and consequences of endogenously expressing antigens in mature DC using adenoviral vectors. Transduction of DC with Ad-EGFP demonstrated endogenous fluorescence in 50-85% of CD83+ DC. Ad-transduced DC stimulated the proliferation of allogeneic CD8+ and CD4+ T cells at low DC: T cell ratios. However, at high DC: T cell ratios the stimulatory capacity of Ad-transduced DC was suppressed. This immunosuppressive effect was confirmed by demonstrating that the stimulatory function of untreated DC could be suppressed in a dose-dependent manner by addition of Ad-transduced DC. Furthermore, transwell experiments suggested that direct cell contact was required. Taken together, our results demonstrate the feasibility of efficiently expressing antigens in CD83+ DC using adenoviruses. However, immunosuppressive effects must be considered and carefully studied before Ad-transduced DC are employed for clinical trials. Gene Therapy (2000) 7, 249-254.