Thermo-optic tuning of silicon nitride microring resonators with low loss non-volatile [Formula: see text] phase change material.

A new family of phase change material based on antimony has recently been explored for applications in near-IR tunable photonics due to its wide bandgap, manifested as broadband transparency from visible to NIR wavelengths. Here, we characterize [Formula: see text] optically and demonstrate the integration of this phase change material in a silicon nitride platform using a microring resonator that can be thermally tuned using the amorphous and crystalline states of the phase change material, achieving extinction ratios of up to 18 dB in the C-band. We extract the thermo-optic coefficient of the amorphous and crystalline states of the [Formula: see text] to be 3.4 x [Formula: see text] and 0.1 x 10[Formula: see text], respectively. Additionally, we detail the first observation of bi-directional shifting for permanent trimming of a non-volatile switch using continuous wave (CW) laser exposure ([Formula: see text] to 5.1 dBm) with a modulation in effective refractive index ranging from +5.23 x [Formula: see text] to [Formula: see text] x 10[Formula: see text]. This work experimentally verifies optical phase modifications and permanent trimming of [Formula: see text], enabling potential applications such as optically controlled memories and weights for neuromorphic architecture and high density switch matrix using a multi-layer PECVD based photonic integrated circuit.

Ultrahigh-Q photonic crystal cavities in silicon rich nitride.

Ultrahigh-Q Photonic Crystal cavities were realized in a suspended Silicon Rich Nitride (SiNx) platform for applications at telecom wavelengths. Using a line width modulated cavity design we achieved a simulated Q of 520,000 with a modal volume of 0.77(λ/n)3. The fabricated cavities were measured using the resonance scattering technique and we demonstrated a measured Q of 120,000. The experimental spectra at different input power also indicate that the non-linear losses are negligible in this material platform.

Experimental demonstration of an apodized-imaging chip-fiber grating coupler for Si3N4 waveguides.

A silicon nitride waveguide is a promising platform for integrated photonics, particularly due to its low propagation loss compared to other complementary metal-oxide-semiconductor compatible waveguides, including silicon-on-insulator. Input/output coupling in such thin optical waveguides is a key issue for practical implementations. Fiber-to-chip grating couplers in silicon nitride usually exhibit low coupling efficiency because the moderate index contrast leads to weak radiation strengths and poor directionality. Here, we present the first, to the best of our knowledge, experimental demonstration of a recently proposed apodized-imaging fiber-to-chip grating coupler in silicon nitride that images an in-plane waveguide mode to an optical fiber placed at a specific distance above the chip. By employing amplitude and phase apodization, the diffracted optical field of the grating is matched to the fiber mode. High grating directionality is achieved by using staircase grating teeth, which produce a blazing effect. Experimental results demonstrate an apodized-imaging grating coupler with a record coupling efficiency of -1.5 dB and a 3 dB bandwidth of 60 nm in the C-band.

In Vitro Activity of Rifampicin Combined with Daptomycin or Tigecycline on Staphylococcus haemolyticus Biofilms.

Staphylococcus haemolyticus is of increasing concern as a cause of several biofilm-associated infections, and today, it represents the second most common organism among clinical isolates of coagulase-negative staphylococci. However, little is known regarding the treatment of infections caused by these bacteria. In this study, we characterize the biofilm formed by S. haemolyticus strains isolated from bloodstream infections and assess in vitro the activity of rifampicin combined with daptomycin or tigecycline against bacteria growing in a biofilm. The results of our studies indicated that the majority (78 %) of methicillin-resistant Staphylococcus haemolyticus strains have the ability to form a biofilm in vitro. None of these strains carried icaADBC genes indicating that they form biofilm via ica-independent mechanisms. The molecular characterization of the biofilm showed that proteins are the predominant matrix component and play a major role in biofilm structure. Extracellular DNA and polysaccharides, other than polysaccharide intercellular adhesin, are also present in the biofilm matrix, but they play a minor role. The images obtained by confocal laser scanning microscopy showed that most S. haemolyticus strains formed a dense biofilm with a low number of dead cells. In vitro study demonstrated excellent activity of tigecycline in combination with rifampicin against cell growth in the proteinous biofilm. The BIC (biofilm inhibitory concentration) value for tigecycline/rifampicin ranged from 0.062 to 1 µg/ml, whereas for daptomycin/rifampicin from 0.125 to 2 µg/ml. These results indicated that the tigecycline/rifampicin combination was more effective against ica-independent biofilm, formed by S. haemolyticus strains, than the daptomycin/rifampicin combination.

Characterization of SCCmec types, antibiotic resistance, and toxin gene profiles of Staphylococcus aureus strains.

Methicillin-resistant Staphylococcus aureus (MRSA) causes serious nosocomial and community acquired infections. Resistance to methicillin is mediated by the mecA gene, which is inserted in a mobile genetic element called staphylococcal cassette chromosome mec (SCCmec). We determined the SCCmec types, the occurrence of genes encoding toxic shock syndrome toxin (tst), exfoliative toxin (eta, etb), Panton-Valentine leukocidin (pvl) as well as antibiotic susceptibility of these isolates. Among 65 hospital-acquired methicillin-resistant S. aureus (HA-MRSA) strains, SCCmec types II, III and IV were identified. Type III SCCmec was the most prevalent (62%), followed by mec types II (24%) and IV (14%). Four community acquired methicillin-resistant S. aureus (CA-MRSA) strains carried SCCmec type IV and were pvl-positive. The most prevalent gene among HA-MRSA was pvl. The toxic shock syndrome toxin and exfoliative toxin genes were found only in hospital-acquired methicillin-resistant S. aureus. The results of this study demonstrate that the SCCmec type III is predominant among strains recovered from hospitalized patients with infections and that these strains were resistant to many antibiotics used in the treatment of staphylococcal infections.

Prestroke antihypertensive therapy: effect on the outcome.

About 70% of stroke patients have a history of hypertension. Patients with hypertension prior to stroke onset have higher blood pressure in the acute phase of stroke than non-hypertensive individuals. High blood pressure in the acute stroke adversely affects outcome. We analyzed 30-days outcome in 1306 hypertensive patients with ischemic stroke, of which 1069 (81.8%) received antihypertensive treatment before stroke onset. Multivariate logistic regression revealed that prestroke use of antihypertensives is an independent predictor of better stroke outcome, in terms of dependency and death or dependency. We conclude that increased efforts toward optimizing hypertension diagnostics and control are needed.

Infections and ischemic stroke outcome.

Background. Infections increase the risk of ischemic stroke (IS) and may worsen IS prognosis. Adverse effects of in-hospital infections on stroke outcome were also reported. We aimed to study the prevalence of pre- and poststroke infections and their impact on IS outcome. Methods. We analysed clinical data of 2066 IS patients to assess the effect of pre-stroke and post-stroke infections on IS severity, as well as short-term (up to 30 days) and long-term (90 days) outcome. The independent impact of infections on poor outcome (death, death/dependency) was investigated by use of logistic regression analysis. The effect of antibiotic therapy during hospitalization on the outcome was also assessed. Results. Pre-stroke infections independently predicted worse short-term outcome. In-hospital infections were associated with worse short-term and long-term IS prognosis. Antibacterial treatment during hospitalization did not improve patients' outcome. Conclusions. Prevention of infections may improve IS prognosis. The role of antibiotic therapy after IS requires further investigations.

Pulse pressure--independent predictor of poor early outcome and mortality following ischemic stroke.

BACKGROUND: Pulse pressure (PP) in acute stroke may be related to the outcome. The link between PP in the first week following ischemic stroke and early outcome was assessed. METHODS: We calculated mean PPs during the first 7 days after stroke onset in 1,677 patients. Poor outcome at hospital discharge was defined as a modified Rankin scale score of 3 or more points or death. Logistic regression was developed to evaluate PP as an independent predictor of early outcome. RESULTS: For patients with poor outcomes the mean PP during the first week was higher than that for patients with non-poor outcomes. A logistic regression model confirmed that elevated mean PP was independently associated with poor outcome at discharge and 30-day mortality. CONCLUSION: Elevated PP during the acute phase of ischemic stroke is an independent predictor of poor early outcome at hospital discharge and 30-day mortality.

Efficacy of Nitric Oxide in Stroke - a randomized trial. Characteristics of patients recruited in Poland.

BACKGROUND AND PURPOSE: High blood pressure is frequent in patients with acute stroke. It frequently returns back to normal values within the first days after onset. It is not yet established whether it requires treatment or not. The Efficacy of Nitric Oxide in Stroke (ENOS) trial aims to assess the efficacy of transdermal glyceryl trinitrate (GTN) patches versus control and stopping or continuing antihypertensive treatments in stroke. The rationale for the study is presented and characteristics of patients recruited in Poland and elsewhere compared. MATERIAL AND METHODS: Patients were recruited to the ENOS study by 1 November, 2007. Baseline characteristics and outcome at 90 days were compared. RESULTS: Of 783 patients overall, 78 patients were recruited in Poland. The age of the patients was similar in the two groups (70.0 vs. 69.1 years). There were fewer males among Polish patients (46.8% vs. 58.3%) and fewer intracranial haemorrhages (3.8% vs. 16.7%). There were more patients with no lesions on CT (41.8% vs. 19.3%). Polish patients more frequently had hypertension (76.0% vs. 66.4%) and subsequently more frequently had antihypertensive treatment (60.8% vs. 45.3%) and nitrates (10.1% vs. 5.0%). The number of patients independent after 3 months was similar. CONCLUSIONS: Polish patients are slightly different from those treated in other countries, but at the moment the patient groups are too small to fully compare patient characteristics in different countries. The trial is ongoing and more centres are welcome to join.