Tailoring single-mode random lasing of tin halide perovskites integrated in a vertical cavity

The development of random lasing (RL) with predictable and controlled properties is an important step to make these cheap optical sources stable and reliable. However, the design of tailored RL characteristics (emission energy, threshold, number of modes) has been only obtained with complex photonic structures, while the simplest optical configurations able to tune the RL is still a challenge. This work demonstrates the tuning of the RL characteristics in spin-coated and inkjet-printed tin-based perovskites integrated into a vertical cavity with low quality factor. When the cavity mode is resonant with the photoluminescence (PL) peak energy, standard vertical lasing is observed. More important, single mode RL operation with the lowest threshold and a quality factor as high as 1000 (twenty times the quality factor of the resonator) is obtained if the cavity mode lies above the PL peak energy due to higher gain. These results can have important technological implications towards the development of low-cost RL sources without chaotic behavior. This article is protected by copyright. All rights reserved.

Unusual Spectrally Reproducible and High Q-Factor Random Lasing in Polycrystalline Tin Perovskite Films

An unusual spectrally reproducible near-IR random lasing (RL) with no fluctuation of lasing peak wavelength is disclosed in polycrystalline films of formamidinium tin triiodide perovskite, which have been chemically stabilized against Sn²⁺ to Sn⁴⁺ oxidation. Remarkably, a quality Q-factor as high as ≈10⁴ with an amplified spontaneous emission (ASE) threshold as low as 2 µJ cm^-2 (both at 20 K) are achieved. The observed spectral reproducibility is unprecedented for semiconductor thin film RL systems and cannot be explained by the strong spatial localization of lasing modes. Instead, it is suggested that the spectral stability is a result of such an unique property of Sn-based perovskites as a large inhomogeneous broadening of the emitting centers, which is a consequence of an intrinsic structural inhomogeneity of the material. Due to this, lasing can occur simultaneously in modes that are spatially strongly overlapped, as long as the spectral separation between the modes is larger than the homogeneous linewidth of the emitting centers. The discovered mechanism of RL spectral stability in semiconductor materials, possessing inhomogeneous broadening, opens up prospects for their practical use as cheap sources of narrow laser lines.

Enhanced Spontaneous Emission of CsPbI3 Perovskite Nanocrystals Using a Hyperbolic Metamaterial Modified by Dielectric Nanoantenna

In this work, we demonstrate, theoretically and experimentally, a hybrid dielectric-plasmonic multifunctional structure able to provide full control of the emission properties of CsPbI₃ perovskite nanocrystals (PNCs). The device consists of a hyperbolic metamaterial (HMM) composed of alternating thin metal (Ag) and dielectric (LiF) layers, covered by TiO₂ spherical MIE nanoresonators (i.e., the nanoantenna). An optimum HMM leads to a certain Purcell effect, i.e., an increase in the exciton radiative rate, but the emission intensity is reduced due to the presence of metal in the HMM. The incorporation of TiO₂ nanoresonators deposited on the top of the HMM is able to counteract such an undesirable intensity reduction by the coupling between the exciton and the MIE modes of the dielectric nanoantenna. More importantly, MIE nanoresonators result in a preferential light emission towards the normal direction to the HMM plane, increasing the collected signal by more than one order of magnitude together with a further increase in the Purcell factor. These results will be useful in quantum information applications involving single emitters based on PNCs together with a high exciton emission rate and intensity.

Outbreak of Pseudomonas aeruginosa infections after CT-guided spinal injections

BACKGROUND

Meningitis and spinal infections with Gram-negative bacteria after local injections for treatment of chronic back pain are rare. This study investigated an outbreak of Pseudomonas aeruginosa infections following computed tomography (CT)-guided spinal injections (SI).

METHODS

A case was defined as a spinal infection or meningitis with P. aeruginosa after SI between 10^th January and 1^st March 2019 in the same outpatient clinic. Patients without microbiological evidence of P. aeruginosa but with a favourable response to antimicrobial therapy active against P. aeruginosa were defined as probable cases.

FINDINGS

Twenty-eight of 297 patients receiving CT-guided SI during the study period developed meningitis or spinal infections. Medical records were available for 19 patients. In 15 patients, there was microbiological evidence of P. aeruginosa, and four patients were defined as probable cases. Two of 19 patients developed meningitis, while the remaining 17 patients developed spinal infections. The median time from SI to hospital admission was 8 days (interquartile range 2-23 days). Patients mainly presented with back pain (N=18; 95%), and rarely developed fever (N=3; 16%). Most patients required surgery (N=16; 84%). Seven patients (37%) relapsed and one patient died. Although the source of infection was not identified microbiologically, documented failures in asepsis when performing SI probably contributed to these infections.

CONCLUSIONS

SI is generally considered safe, but non-adherence to asepsis can lead to deleterious effects. Spinal infections caused by P. aeruginosa are difficult to treat and have a high relapse rate.

Inhomogeneous Broadening of Photoluminescence Spectra and Kinetics of Nanometer-Thick (Phenethylammonium)2PbI4 Perovskite Thin Films: Implications for Optoelectronics

An outstanding potentiality of layered two-dimensional (2D) organic-inorganic hybrid perovskites (2DHPs) is in the development of solar cells, photodetectors, and light-emitting diodes. In 2DHPs, an exciton is localized in an atomically thin lead(II) halide inorganic layer of sub-nanometer thickness as in a quantum well sandwiched between organic layers as energetic and dielectric barriers. In previous years, versatile optical characterization of 2DHPs has been carried out mainly for thin flakes of single crystals and ultrathin (of the order of 20 nm) polycrystalline films, whereas there is a lack of optical characterization of thick (hundreds of nanometers) polycrystalline films, fundamentals for fabrication of devices. Here, with the use of photoluminescence (PL) and absorption spectroscopies, we studied the exciton behavior in ∼200 nm polycrystalline thin films of 2D perovskite (PEA)₂PbI₄, where PEA is phenethylammonium. Contrary to the case of ultrathin films, we have found that peak energies and line width of the excitonic bands in our films demonstrate unusual extremely weak sensitivity to temperature in 20-300 K diapason. The excitonic PL band is characterized by a significant (∼30 meV) Stokes shift with respect to the corresponding absorption band as well as by a full absence of the exciton fine structure at cryogenic temperatures. We suggest that the observed effects are due to the large inhomogeneous broadening of the excitonic PL and absorption bands resulting from the (PEA)₂PbI₄ band gap energy dependence on the number of lead(II) halide layers of individual crystallites. The characteristic time of the exciton energy funneling from higher- to lower-energy crystallites within (PEA)₂PbI₄ polycrystalline thin films is about 100 ps.

HIV DNA reservoir and elevated PD-1 expression of CD4 T-cell subsets particularly persist in the terminal ileum of HIV-positive patients despite cART

OBJECTIVES

Despite its importance as an HIV anatomic sanctuary, little is known about the characteristics of the HIV reservoir in the terminal ileum (TI). In blood, the immune checkpoint inhibitor programmed-death-1 (PD-1) has been linked to the HIV reservoir and T-cell immune dysfunction. We thus evaluated PD-1 expression and cell-associated HIV DNA in memory CD4 T-cell subsets from TI, peripheral blood (PB) and rectum (RE) of untreated and treated HIV-positive patients to identify associations between PD-1 and HIV reservoir in other sites.

METHODS

Using mononuclear cells from PB, TI and RE of untreated HIV-positive (N = 6), treated (n = 18) HIV-positive and uninfected individuals (n = 16), we identified and sorted distinct memory CD4 T-cell subsets by flow cytometry, quantified their cell-associated HIV DNA using quantitative PCR and assessed PD-1 expression levels using geometric mean fluorescence intensity. Combined HIV-1 RNA in situ hybridization and immunohistochemistry was performed on ileal biopsy sections.

RESULTS

Combined antiretroviral therapy (cART)-treated patients with undetectable HIV RNA and significantly lower levels of HIV DNA in PB showed particularly high PD-1 expression in PB and TI, and high HIV DNA levels in TI, irrespective of clinical characteristics. By contrast, in treatment-naïve patients HIV DNA levels in memory CD4 T-cell subsets were high in PB and TI.

CONCLUSION

Elevated PD-1 expression on memory CD4 T-cells in PB and TI despite treatment points to continuous immune dysfunction and underlines the importance of evaluating immunotherapy in reversing HIV latency and T-cell reconstitution. As HIV DNA particularly persists in TI despite cART, investigating samples from TI is crucial in understanding HIV immunopathogenesis.

Purcell Enhancement and Wavelength Shift of Emitted Light by CsPbI3 Perovskite Nanocrystals Coupled to Hyperbolic Metamaterials

Manipulation of the exciton emission rate in nanocrystals of lead halide perovskites (LHPs) was demonstrated by means of coupling of excitons with a hyperbolic metamaterial (HMM) consisting of alternating thin metal (Ag) and dielectric (LiF) layers. Such a coupling is found to induce an increase of the exciton radiative recombination rate by more than a factor of three due to the Purcell effect when the distance between the quantum emitter and HMM is nominally as small as 10 nm, which coincides well with the results of our theoretical analysis. Besides, an effect of the coupling-induced long wavelength shift of the exciton emission spectrum is detected and modeled. These results can be of interest for quantum information applications of single emitters on the basis of perovskite nanocrystals with high photon emission rates.

Enhanced Nonlinear Optical Coefficients of MAPbI3 Thin Films by Bismuth Doping

The poor photostability under ambient conditions of hybrid halide perovskites has hindered their recently explored promising nonlinear optical properties. Here, we show how Bi³⁺ can partially substitute Pb²⁺ homogeneously in the commonly studied MAPbI₃, improving both environmental stability and photostability under high laser irradiation. Bi content around 2 atom % produces thin films where the nonlinear refractive (n₂) and absorptive coefficients (β), which modify the refractive index (Δn) of the material with light fluence (I), increase up to factors of 4 and 3.5, respectively, compared to undoped MAPbI₃. Higher doping inhibits the nonlinear parameters; however, the samples show higher fluence damage thresholds. Thus, these results provide a road map on how MAPbI₃ can be engineered for practical cost-effective nonlinear applications by means of Bi doping, including optical limiting devices and multiple-harmonic generation into optoelectronics devices.

Single-Exciton Amplified Spontaneous Emission in Thin Films of CsPbX3 (X = Br, I) Perovskite Nanocrystals

CsPbX₃ perovskite nanocrystals (PNCs) have emerged as an excellent material for stimulated emission purposes, with even more prospective applications than conventional colloidal quantum dots. However, a better understanding of the physical mechanisms responsible for amplified spontaneous emission (ASE) is required to achieve more ambitious targets (lasing under continuous wave optical or electrical excitation). Here, we establish the intrinsic mechanisms underlying ASE in PNCs of three different band gaps (CsPbBr₃, CsPbBr_1.5I_1.5, and CsPbI₃). Our characterization at cryogenic temperatures does not reveal any evidence of the biexciton mechanism in the formation of ASE. Instead, the measured shift toward long wavelengths of the ASE band is easily explained by the reabsorption in the PNC layer, which becomes stronger for thicker layers. In this way, the threshold of ASE is determined only by optical losses at a given geometry, which is the single-exciton mechanism responsible for ASE. Experimental results are properly reproduced by a physical model.

Single-Exciton Amplified Spontaneous Emission in Thin Films of CsPbX3 (X = Br, I) Perovskite Nanocrystals

CsPbX₃ perovskite nanocrystals (PNCs) have emerged as an excellent material for stimulated emission purposes, with even more prospective applications than conventional colloidal quantum dots. However, a better understanding of the physical mechanisms responsible for amplified spontaneous emission (ASE) is required to achieve more ambitious targets (lasing under continuous wave optical or electrical excitation). Here, we establish the intrinsic mechanisms underlying ASE in PNCs of three different band gaps (CsPbBr₃, CsPbBr_1.5I_1.5, and CsPbI₃). Our characterization at cryogenic temperatures does not reveal any evidence of the biexciton mechanism in the formation of ASE. Instead, the measured shift toward long wavelengths of the ASE band is easily explained by the reabsorption in the PNC layer, which becomes stronger for thicker layers. In this way, the threshold of ASE is determined only by optical losses at a given geometry, which is the single-exciton mechanism responsible for ASE. Experimental results are properly reproduced by a physical model.

[Modern HIV treatment]

Human immunodeficiency virus (HIV) infection has become a chronic disease with a favourable prognosis if adequate antiretroviral therapy (ART) is applied. Therefore, each patient with HIV infection should be treated irrespectively of clinical symptoms or of immunological status. A combination of three active drugs that have to be taken life-long has been standard for many years. The regimen contains two nucleoside reverse transcriptase inhibitors plus either an integrase inhibitor, a boosted protease inhibitor, or a non-nucleoside reverse transcriptase inhibitor. Integrase inhibitors are recommended as the third partner of choice by recent guidelines due to their high efficacy and their favourable safety profile. Many combination drugs are now available which allow a simple treatment with few tablets and in many instances a one-pill combination per day is an option. Potential interactions with drugs given for other diseases have to be taken into account, especially if a pharmacological booster is part of the regimen. Combination therapy should be changed if either virological failure (HIV RNA >200 copies/ml) or drug-related adverse events occur. In special situations (e. g. pregnancy) highly experienced experts in the field should be consulted. Novel approaches for HIV therapy include dual therapy as well as treatment with long-acting substances. Beside therapy, antiretroviral drugs are used for prevention either as post-exposure prophylaxis or as pre-exposure prophylaxis.

Optical Amplification in Hollow-Core Negative-Curvature Fibers Doped with Perovskite CsPbBr3 Nanocrystals

We report a hollow-core negative-curvature fiber (HC-NCF) optical signal amplifier fabricated by the filling of the air microchannels of the fiber with all-inorganic CsPbBr3 perovskite nanocrystals (PNCs). The optimum fabrication conditions were found to enhance the optical gain, up to +3 dB in the best device. Experimental results were approximately reproduced by a gain assisted mechanism based on the nonlinear optical properties of the PNCs, indicating that signal regeneration can be achieved under low pump powers, much below the threshold of stimulated emission. The results can pave the road of new functionalities of the HC-NCF with PNCs, such as optical amplification, nonlinear frequency conversion and gas sensors.

Structural characterization of bulk and nanoparticle lead halide perovskite thin films by (S)TEM techniques

Lead halide (APbX₃) perovskites, in polycrystalline thin films but also perovskite nanoparticles (NPs) has demonstrated excellent performance to implement a new generation of photovoltaic and photonic devices. The structural characterization of APbX₃ thin films using (scanning) transmission electron microscopy ((S)TEM) techniques can provide valuable information that can be used to understand and model their optoelectronic performance and device properties. However, since APbX₃ perovskites are soft materials, their characterization using (S)TEM is challenging. Here, we study and compare the structural properties of two different metal halide APbX₃ perovskite thin films: bulk CH₃NH₃PbI₃ prepared by spin-coating of the precursors in solution and CsPbBr₃ colloidal NPs synthetized and deposited by doctor blading. Both specimen preparation methods and working conditions for analysis by (S)TEM are properly optimized. We show that CH₃NH₃PbI₃ thin films grown by a one-step method are composed of independent grains with random orientations. The growth method results in the formation of tetragonal perovskite thin films with good adherence to an underlying TiO₂ layer, which is characterized by a photoluminescence (PL) emission band centered at 775 nm. The perovskite thin films based on CsPbBr₃ colloidal NPs, which are used as the building blocks of the film, are preserved by the deposition process, even if small gaps are observed between adjacent NPs. The crystal structure of CsPbBr₃ NPs is cubic, which is beneficial for optical properties due to its optimal band gap. The absorption and PL spectra measured in both the thin film and the colloidal solution of CsPbBr₃ NPs are very similar, indicating a good homogeneity of the thin films and the absence of aggregation of NPs. However, a particular care was required to avoid long electron irradiation times during our structural studies, even at a low voltage of 80 kV, as the material was observed to decompose through Pb segregation.

Toward Metal Halide Perovskite Nonlinear Photonics

The possibility of controlling light using the nonlinear optical properties of photonic devices opens new points of view in information and communications technology applications. In this Perspective, we review and analyze the potential role of metal halide perovskites in a framework different from their usual one in photovoltaic and light-emitting devices, namely, the one where they can play as nonlinear photonic materials. We contextualize this new role by comparing the few extant results on their nonlinear optical properties to those of other known nonlinear materials. As a result of this analysis, we provide a vision of future developments in photonics that can be expected from this new perspective on metal halide perovskites.

To prescribe, or not to prescribe: decision making in HIV-1 post-exposure prophylaxis

OBJECTIVES

We investigated the trend in usage of post-exposure prophylaxis (PEP) after HIV-1 risk exposure and evaluated PEP prescription decision making of physicians according to guidelines.

METHODS

All PEP consultations from January 2014 to December 2016 in patients presenting at the University Hospital of Cologne (Germany) were retrospectively analysed. HIV risk contacts included sexual and occupational exposure. The European AIDS Clinical Society (EACS) Guidelines for HIV PEP (version 9.0, 2017) were used for assessment.

RESULTS

A total of 649 patients presented at the emergency department (ED) or the clinic for infectious diseases (IDC) for PEP consultations. A continuous increase in the number of PEP requests was recorded: 189 in 2014, 208 in 2015 and 252 in 2016. PEP consultations in men who have sex with men (MSM) showed a remarkable increase in 2016 (2014, n = 96; 2015, n = 101; 2016, n = 152). Decisions taken by physicians with a specialization in infectious diseases (n = 547) included 61 (11%) guideline-discordant prescriptions [2014: 14% (n = 22); 2015: 9% (n = 16); 2016: 11% (n = 23)]. Among these, sexual exposure accounted for 45 (74%) cases, including 15 cases of nonconsensual sex, while occupational exposure accounted for 14 (23%) cases and other exposure two cases (3%). The main reason for guideline-discordant PEP prescriptions was emotional stress of the patient (n = 37/61).

CONCLUSIONS

PEP prescriptions are increasing and decision making is influenced by patients' emotional stress, but PEP prescriptions should be strictly administered according to risk assessment.

Time to culture conversion in smokers with pulmonary tuberculosis

Background and objective. It has been reported that tobacco smoking slows the sterilisation of sputum culture in pulmonary tuberculosis, but the factors that could delay culture conversion in patients who smoke are not known. Our aim is to identify the factors influencing sputum culture conversion in smokers with pulmonary tuberculosis. Methods. Ninety-nine patients with a smoking history and diagnosed with pulmonary tuberculosis were analysed retrospectively. The relationship between sputum culture status at the second month and the following variables: age, gender, pack-years index, comorbid diseases, number acid-fast bacilli (AFB) in sputum smear examination, radiological findings (cavitary, extensive or limited disease), drug susceptibility pattern and initial treatment, was analysed. The Student t-test, chi-square test and logistic regression model with forward stepwise conditional methods were used for statistical analysis. A p value of <0.05 was considered to be statistically significant. Results. Twenty six patients (26.2%): 18 males (22.2%) and 8 females (44%) were sputum culture positive at the end of the second month of treatment. In univariate analysis, culture conversion time was significantly associated with female gender and extensive disease, but in a logistic regression analysis was only correlated with female gender (OR=5.63 95% CI 1.21-20.64-p=0.02). Conclusion. In current smokers with pulmonary tuberculosis, the ‘time to culture’ conversion relates only to the female gender.

Polymer waveguide couplers based on metal nanoparticle-polymer nanocomposites

In this work Au nanoparticles (AuNPs) are incorporated into poly(methyl methacrylate) (PMMA) waveguides to develop optical couplers that are compatible with planar organic polymer photonics. A method for growing AuNPs (of 10 to 100 nm in size) inside the commercially available Novolak resist is proposed with the intention of tuning the plasmon resonance and the absorption/scattering efficiencies inside the patterned structures. The refractive index of the MNP-Novolak nanocomposite (MNPs: noble metal nanoparticles) is carefully analysed both experimentally and numerically in order to find the appropriate fabrication conditions (filling factor and growth time) to optimize the scattering cross section at a desired wavelength. Then the nanocomposite is patterned inside a PMMA waveguide to exploit its scattering properties to couple and guide a normal incident laser light beam along the polymer. In this way, light coupling is experimentally demonstrated in a broad wavelength range (404-780 nm). Due to the elliptical shape of the MNPs the nanocomposite demonstrates a birefringence, which enhances the coupling to the TE mode up to efficiencies of around 1%.

Polymer/Perovskite Amplifying Waveguides for Active Hybrid Silicon Photonics

The emission properties of hybrid halide perovskites are exploited to implement a stable and very low power operation waveguide optical amplifier integrated in a silicon platform. By optimizing its design with a poly(methyl methacrylate) (PMMA) encapsulation, this novel photonic device presents a net gain of around 10 dB cm(-1) and 3-4 nm linewidth with an energy threshold as low as 2 nJ pulse(-1) and exhibiting no degradation after one year.

MWP phase shifters integrated in PbS-SU8 waveguides

We present new kind of microwave phase shifters (MPS) based on dispersion of PbS colloidal quantum dots (QDs) in commercially available photoresist SU8 after a ligand exchange process. Ridge PbS-SU8 waveguides are implemented by integration of the nanocomposite in a silicon platform. When these waveguides are pumped at wavelengths below the band-gap of the PbS QDs, a phase shift in an optically conveyed (at 1550 nm) microwave signal is produced. The strong light confinement produced in the ridge waveguides allows an improvement of the phase shift as compared to the case of planar structures. Moreover, a novel ridge bilayer waveguide composed by a PbS-SU8 nanocomposite and a SU8 passive layer is proposed to decrease the propagation losses of the pump beam and in consequence to improve the microwave phase shift up to 36.5° at 25 GHz. Experimental results are reproduced by a theoretical model based on the slow light effect produced in a semiconductor waveguide due to the coherent population oscillations. The resulting device shows potential benefits respect to the current MPS technologies since it allows a fast tunability of the phase shift and a high level of integration due to its small size.

UV-patternable nanocomposite containing CdSe and PbS quantum dots as miniaturized luminescent chemo-sensors

We have developed a patternable nanocomposite sensor based on luminescent CdSe QDs and a polyisoprene-based photoresist (PIP) as host matrix that showed chemosensing response against MET and EDA in vapour with a LOD around 0.1 pg and 15 ng, respectively.

Efficient excitation of photoluminescence in a two-dimensional waveguide consisting of a quantum dot-polymer sandwich-type structure

In this Letter, we study a new kind of organic polymer waveguide numerically and experimentally by combining an ultrathin (10-50 nm) layer of compactly packed CdSe/ZnS core/shell colloidal quantum dots (QDs) sandwiched between two cladding poly(methyl methacrylate) (PMMA) layers. When a pumping laser beam is coupled into the waveguide edge, light is mostly confined around the QD layer, improving the efficiency of excitation. Moreover, the absence of losses in the claddings allows the propagation of the pumping laser beam along the entire waveguide length; hence, a high-intensity photoluminescence (PL) is produced. Furthermore, a novel fabrication technology is developed to pattern the PMMA into ridge structures by UV lithography in order to provide additional light confinement. The sandwich-type waveguide is analyzed in comparison to a similar one formed by a PMMA film homogeneously doped by the same QDs. A 100-fold enhancement in the waveguided PL is found for the sandwich-type case due to the higher concentration of QDs inside the waveguide.

[Morbidity and mortality conferences in internal medicine--experience at the University Hospital of Cologne]

Morbidity and mortality (M&M) conferences serve as a forum for the discussion of adverse events and errors in the treatment of patients. In the United States M&M conferences are an established part of medical training programs. While being state of the art in specialities like surgery and anesthesiology, they were established later on in internal medicine. To date, no reports have been published on M&M conferences in departments of internal medicine in Germany. Since August 2010 a morbidity and mortality conference takes place once per month in the Department I of Internal Medicine of the university hospital of Cologne. Cases with unexpected death, unexpected complications or medical errors are discussed. The primary goal is to create an open and confidential forum for doctors, where errors can be discussed without any assignment of guilt. The uncovering of structural problems frequently leads to direct improvements in patient care. Furthermore, the conference can play an important role in medical education.

Birefringent porous silicon membranes for optical sensing

In this work anisotropic porous silicon is investigated as a material for optical sensing. Birefringence and sensitivity of the anisotropic porous silicon membranes are thoroughly studied in the framework of Bruggeman model which is extended to incorporate the influence of environment effects, such as silicon oxidation. The membranes were also characterized optically demonstrating sensitivity as high as 1245 nm/RIU at 1500 nm. This experimental value only agrees with the theory when it takes into consideration the effect of silicon oxidation. Furthermore we demonstrate that oxidized porous silicon membranes have optical parameters with long term stability. Finally, we developed a new model to determine the contribution of the main depolarization sources to the overall depolarization process, and how it influences the measured spectra and the resolution of birefringence measurements.

Photoluminescence waveguiding in CdSe and CdTe QDs-PMMA nanocomposite films

In this paper, active planar waveguides based on the incorporation of CdSe and CdTe nanocrystal quantum dots in a polymer matrix are demonstrated. In the case of doping the polymer with both types of quantum dots, the nanocomposite film guides both emitted colors, green (550 nm, CdTe) and orange (600 nm, CdSe). The optical pumping laser can be coupled not only with a standard end-fire coupling system, but also directing the beam to the surface of the sample, indicating a good absorption cross-section and waveguide properties. To achieve these results, a study of the nanocomposite optical properties as a function of the nanocrystal concentration is presented and the optimum conditions are found for waveguiding.

Role of emphysema and airway obstruction in prognosis of lung cancer

BACKGROUND AND OBJECTIVE

It has been reported that the presence of COPD and emphysema is associated with an increased risk of lung cancer, but the prognosis significance of these two conditions is not well known. The aim of our study was to analyze the influence of COPD and emphysema in the prognosis of non-small cell lung cancer (NSCLC).

METHODS

Three hundred and fifty-three patients with cytohistologic diagnosis of NSCLC were prospectively collected. The relationship between survival at two years and the following variables: age, sex, smoking habit, comorbid diseases (cardiovascular diseases, previous tumour and COPD), weight loss, presence of emphysema on CT scan, performance status (PS) and treatment, was analyzed. The Kaplan-Meier method and log-rank test were used for survival analysis. A multivariate Cox proportional hazard model, stratified by TNM stage, was used to evaluate prognostic factors.

RESULTS

Emphysema was present in 110 patients, associated with COPD in 78 (70.9%). In univariate analysis, survival decreased with age>70 years (p=0.01), presence of emphysema (p=0.02), weight loss (p=0.00001), PS≥2 (p=0.00001) and symptomatic treatment (p=0.0001). Multivariate analyses identified emphysema (HR=1.49 (95% CI 1.11-2.01)), PS≥2 (HR=2.12 (95% CI 1.31-3.38)) and treatment: surgery (HR=0.3 (95% CI 0.15-0.56)) and chemotherapy (HR=0.34 (95% CI 0.31-0.57)) as independent prognostic factors.

CONCLUSION

The presence of emphysema affects the prognostic outcome of patients with non-small cell lung cancer. Emphysema should therefore be considered for prognostic studies on comorbidity.

Upregulation of alpha-synuclein expression in the rat cerebellum in experimental hepatic encephalopathy

AIMS

The overexpression of alpha-synuclein has been associated with neurodegenerative diseases, especially when the protein aggregates to form insoluble structures. The present study examined the effect of chronic hyperammonaemia on alpha-synuclein expression in the rat cerebellum following portacaval anastomosis (PCA).

METHODS

Immunohistochemical and western blot determinations were performed 1 month and 6 months after the PCA procedure.

RESULTS

A time-dependent increase in alpha-synuclein expression was seen in the cerebellar grey matter compared with the controls. At 1 month post PCA, alpha-synuclein-immunopositive material was observed in the molecular layer, while the Purkinje cells showed weak alpha-synuclein expression, and alpha-synuclein aggregates were observed throughout the granular layer. At 6 months post PCA, alpha-synuclein expression was significantly increased compared with the controls. alpha-synuclein-immunostained astroglial cells were also found; the Bergmann glial cells showed alpha-synuclein-positive processes in the molecular layer of PCA-exposed rats, and in the granular layer, perivascular astrocytes showed intense alpha-synuclein immunoreactivity, as indicated by colocalization of alpha-synuclein with glial fibrillary acidic protein (GFAP). In addition, ubiquitin-immunoreactive inclusions were present in PCA-exposed rats, although they did not colocalize with alpha-synuclein. Western blotting performed at 6 months post PCA showed a reduction in the level of soluble alpha-synuclein compared with 1 month post PCA and the controls; this reduction was concomitant with an increase in the insoluble form of alpha-synuclein.

CONCLUSIONS

Although the precise mechanism by which alpha-synuclein aggregates in PCA-treated rats remains unknown, the present data suggest an important role for this protein in the onset and progression of hepatic encephalopathy, probably via its expression in astroglial cells.

Effect of ammonia on ciliary neurotrophic factor mRNA and protein expression and its upstream signalling pathway in cultured rat astroglial cells: possible implication of c-fos, Sp1 and p38MAPK

Ciliary neurotrophic factor (CNTF) may be implicated in the pathogenetic mechanisms of hepatic encephalopathy. We tested this hypothesis by treating confluent primary cultures of rat astroglial cells with ammonium chloride for various periods and analysing the effect of ammonia on the signalling pathway that regulates CNTF mRNA and protein expression. Ammonia treatment induced a dose- and time-dependent reduction in CNTF mRNA and protein expression. Surface-enhanced laser desorption/ionization-time-of-flight mass spectrometry analysis of CNTF in the culture medium demonstrated that ammonia also induced a significant decrease in CNTF release. In addition, ammonia affected Sp1 and c-fos, transcription factors that regulate CNTF mRNA and protein expression, which showed partial dephosphorylation and significantly lower mRNA and protein levels. Total content of p38MAPK (for which Sp1 and c-fos are substrates) was unaffected by ammonia, although the diphosphorylated (active) form was significantly reduced after ammonia exposure.

The expression of nNOS, iNOS and nitrotyrosine is increased in the rat cerebral cortex in experimental hepatic encephalopathy

The changes in the distribution and amount of nitric oxide (NO) synthases (nNOS and iNOS) and the appearance of nitrotyrosine (NT) in the rat cerebral cortex were investigated following portacaval anastomosis (PCA), an experimental hepatic encephalopathy (HE) model. One month after PCA, rats showed more neurones immunoreactive to nNOS than did control animals. At 6 months post PCA, the number of neurones expressing nNOS had again increased and the intensity of the immunoreactions was stronger. Immunohistochemical analysis also showed that iNOS was increasingly expressed in pyramidal-like cortical neurones and in perivascular astrocytes from 1 to 6 months post PCA. In addition, a significant increase in cerebral iNOS concentration, at both post-PCA periods, was determined by Western blotting. The iNOS induction appears to be correlated with the length of the post-PCA period. PCA also induced the expression of NT, a nitration product of peroxynitrite. NT immunoreactivity was found in pyramidal-like cortical neurones. At 6 months, NT immunoreactivity was also evident in perivascular astrocytes, which was concomitant with a significant increase in NT protein level. PCA therefore not only increases the expression of nNOS but also induces the expression of iNOS and NT in both neurones and astrocytes. Taken together, these findings indicate that the induction of iNOS in pyramidal neurones and cortical astrocytes 6 months after PCA contributes to the generation of NT, and demonstrate the clear participation of NO in the pathogenic process of HE in this model.

Acute and chronic effects of exposure to a 1-mT magnetic field on the cytoskeleton, stress proteins, and proliferation of astroglial cells in culture

This paper reports the effects of exposure to static, sinusoidal (50 Hz), and combined static/sinusoidal magnetic fields on cultured astroglial cells. Confluent primary cultures of astroglial cells were exposed to a 1-mT sinusoidal, static, or combined magnetic field for 1h. In another experiment, cells were exposed to the combined magnetic field for 1, 2, and 4h. The hsp25, hsp60, hsp70, actin, and glial fibrillary acidic protein contents of the astroglial cells were determined by immunoblotting 24h after exposure. No significant differences were seen between control and exposed cells with respect to their contents of these proteins, neither were any changes in cell morphology observed. In a third experiment to determine the effect of a chronic (11-day) exposure to a combined 1-mT static/sinusoidal magnetic field on the proliferation of cultured astroglial cells, no significant differences were seen between control, sham-exposed, or exposed cells. These results suggest that exposure to 1-mT sinusoidal, static, or combined magnetic fields has no significant effects on the stress, cytoskeletal protein levels in, or proliferation of cultured astroglial cells.

Neuronal and inducible nitric oxide synthase expression in the rat cerebellum following portacaval anastomosis

In order to determine the role of neuronal nitric oxide synthase (nNOS) and inducible nitric oxide synthase (iNOS) in the pathogenesis of experimental hepatic encephalopathy (HE), the expression of both was analyzed in the cerebellum of rats 1 month and 6 months after performing portacaval anastomosis (PCA). In control cerebella, nNOS immunoreactivity was mainly observed in the molecular layer (ML), whereas the Purkinje cells did not express nNOS. However, nNOS expression was detected in the Purkinje cells at 1 month after PCA, correlating with a decrease in nNOS expression in the ML--part of an overall reduction in cerebellar nNOS concentrations (as determined by Western blotting). At 6 months post-PCA, a significant increase in nNOS expression was observed in the ML, as well as increased nNOS immunoreactivity in the Purkinje cells. nNOS immunoreactivity was also observed in the Bergmann glial cells of PCA-treated rats. While no immunoreactivity for iNOS was seen in the cerebella of control rats, iNOS immunoreactivity was significantly induced in the cerebellum 1 month after PCA. In addition, the expression of iNOS was greater at 6 months than at 1 month post-PCA. Immunohistochemical analysis revealed this iNOS to be localized in the Purkinje cells and Bergmann glial cells. The induction of iNOS in astroglial cells has been associated with pathological conditions. Therefore, the iNOS expression observed in the Bergmann glial cells might play a role in the pathogenesis of HE, the harmful effects of PCA being caused by them via the production of excess nitric oxide. These results show that nNOS and iNOS are produced in the Purkinje cells and Bergmann glial cells following PCA, implicating nitric oxide in the pathology of HE.

Down-regulation of astroglial proteins in the rat cerebellum after portacaval anastomosis

The effect of short-term portacaval anastomosis (PCA) on the expression of specific astroglial markers [glial fibrillary acidic protein (GFAP) and glutamine synthetase (GS)] in the rat cerebellum was examined to determine the influences of PCA on astroglial cells. The results suggest that PCA directly interferes with astroglial cytoskeleton, as indicated by the irregular distribution and reduced expression of GFAP observed after 1 month. PCA also decreased GS immunoreactivity in the Bergmann glial processes of the molecular layer, as well as in astrocytes of the granule cell layer. It might also modulate glutamatergic nervous activity as GS expression was reduced in 1 month post-PCA brains. Moreover, the GFAP and GS levels in PCA-exposed rats were lower than in control rats. This might contribute to the appearance of encephalopathy by increasing extracellular glutamate and/or ammonia concentrations. These results show that short-term PCA interferes with astroglial protein expression, with both GFAP and GS levels falling in astroglial cells.

Prenatal cannabinoid exposure down- regulates glutamate transporter expressions (GLAST and EAAC1) in the rat cerebellum

Efficient reuptake of synaptically released glutamate is essential for preventing glutamate receptor overstimulation and neuronal death. Glutamate transporters play a vital role in removing extracellular glutamate from the synaptic cleft. This study analyzed the expression of the glial (GLAST) and neuronal (EAAC1) subtypes of glutamate transporter in the cerebellum of male and female offspring exposed pre- and postnatally to Delta9-tetrahydrocannabinol (THC, the main component of marijuana). Pregnant rats were administered saline or THC from gestational day 5 to postnatal day 20 (PD20). The expression of glutamate transporters was examined at PD20, PD30 and PD70 (10 and 50 days after THC withdrawal) to analyze the short- and long-term effects of prenatal THC exposure. The expression of the glutamate transporter GLAST in astroglial cells and EAAC1 in Purkinje neurons decreased in THC-exposed offspring compared to controls. This reduction was observed at all ages but mainly in males. Moreover, the glial glutamate transporter level in THC-exposed rats (quantified by Western blot) was lower than in control rats. These results suggest that THC exposure during cerebellar development may alter the glutamatergic system not only during the period of drug exposure but in the postnatal stage following withdrawal. The down-regulation reported here might reflect an abnormal maturation of the glutamatergic neuron-glia circuitry.

The Fang population of Equatorial Guinea characterised by 15 STR-PCR polymorphisms

Allele frequencies for 15 STR loci (D8S1179, D21S11, D7S820, CSF1PO, D19S433, HUMVWA31A, HUMTPOX, D18S51, D3S1358, HUMTHO1, D13S317, D16S539, D2S1338, D5S818 and HUMFGA) were analysed in the Fang population of Bioko Island, Equatorial Guinea. No deviation from Hardy-Weinberg equilibrium was found for all loci. Statistical parameters demonstrated the forensic utility of the analysed systems.

[Transbronchial needle aspiration in bronchogenic carcinoma with visible lesions: diagnostic yield and cost]

BACKGROUND

Transbronchial needle aspiration (TBNA) is a bronchoscopic technique whose usefulness in diagnosing endobronchial lesions has not yet been clearly established.

OBJECTIVE

We aimed to determine whether the diagnostic yield of fiberoptic bronchoscopy could be increased, without a negative impact on diagnostic costs, if TBNA were used in combination with conventional diagnostic techniques (bronchial washings and bronchial brushings and forceps biopsy).

PATIENTS AND METHODS

The cases of 130 patients diagnosed with bronchogenic carcinoma with endoscopically visible lesions were analyzed retrospectively. All had undergone conventional diagnostic procedures; TBNA was also performed if the bronchoscopist considered it was indicated. The final cost was calculated in euros for each diagnosis as the sum of the cost of the procedures needed to reach the diagnosis, including both endoscopic procedures and others (transthoracic needle aspiration, lymph node biopsy). Diagnostic yield and costs in cases diagnosed using only conventional techniques were compared to the yield and costs in cases in which both conventional techniques and TBNA were used.

RESULTS

TBNA was performed in 49 patients and provided the diagnosis in 85.7%. Conventional techniques led to cytological and histological diagnosis in 80.2% of the cases, and the combination of conventional techniques and TBNA gave a diagnosis in 89.7% (P=.01). Significant differences were observed in extrinsic compression (conventional 37.5%; conventional+TBNA 100%; P=.01), submucosal infiltration (conventional 54.6%; conventional+TBNA 85%; P=.03), and exophytic mass with necrosis (conventional 80%; conventional+TBNA 100%; P=.01). The mean (SD) cost of diagnosis was euros 381.60 (euros 156.53) using conventional techniques and euros 413.25 (euros 112.91) for conventional techniques in combination with TBNA. By adding TBNA, costs decreased for diagnoses of submucosal infiltration, exophytic mass with necrosis and extrinsic compression, although the saving was significant only for extrinsic compression.

CONCLUSION

The diagnostic yield of TBNA is high for endoscopically visible bronchial anomalies suggesting neoplasm, particularly when the lesion is due to extrinsic compression, submucosal infiltration, or exophytic mass with necrosis.

Achromobacter xylosoxidans bacteremia: a 10-year analysis of 54 cases

Fifty-four cases of Achromobacter xylosoxidans bacteremia diagnosed over a 10-year period in patients from 2 months to 87 years of age were reviewed. Fifty-two episodes were nosocomial. The most frequent underlying condition was neoplasm (solid or hematological). The source of infection was a contaminated intravenous catheter in 35 patients (60%) and pneumonia in 6 patients. Eight (15%) patients died. The only risk factors significantly associated with mortality were age over 65 years and neutropenia. The results of in vitro susceptibility studies of the isolates showed that antibiotic therapy with antipseudomonal penicillins or carbapenems would be a reasonable choice. An epidemiological study conducted in the hemodialysis unit showed Achromobacter xylosoxidans in tap water and on the hands of two healthcare workers but not in the hemodialysis systems. Patients were probably contaminated when healthcare workers manipulated the intravenous catheters without wearing gloves.

Reduced glial fibrillary acidic protein and glutamine synthetase expression in astrocytes and Bergmann glial cells in the rat cerebellum caused by delta(9)-tetrahydrocannabinol administration during development

In this study we analyzed the responses of cerebellar astroglial cells to pre- and perinatal delta(9)-tetrahydrocannabinol (THC) exposure in three postnatal ages and both sexes. To determine whether THC during development directly modifies astroglial growth, this study investigated the effects of THC on astroglial morphological changes and on the expression of specific astroglial markers (glial fibrillary acidic protein: GFAP and glutamine synthetase: GS). Our results demonstrated that the administration of THC during development has deleterious effects on astroglial maturation in the cerebellum. These results also indicate that THC might interfere with astroglial differentiation in a way dependent on sex. The effect of cannabinoids on the development of cerebellar astroglial cells (astrocytes and Bergmann glial cells) is to reduce protein synthesis, since both GFAP and GS decreased in astroglial cells, not only during THC exposure but also in adult ages. Our data suggest that pre- and perinatal THC exposure directly interferes with astroglial maturation by disrupting normal cytoskeletal formation, as indicated by the irregular disposition of GFAP and the lower GFAP expression observed at all the ages studied. THC exposure during development may also modulate glutamatergic nervous activity since GS expression is reduced in THC-exposed brains. GS expression increased progressively after THC withdrawal, but GS expression had still not reached control values two months after THC withdrawal. This indicates that glutamate uptake is lower in glial cells exposed to THC, since GS expression is lower than in older controls. Consequently, glutamatergic neurotransmission may be affected by cannabinoid exposure during gestation. Therefore, cannabinoids exert developmental toxicity, at least on astroglial cells, which could contribute to fetal brain growth retardation.

Pancreatic ascites: study of therapeutic options by analysis of case reports and case series between the years 1975 and 2000

OBJECTIVE

Because of the low incidence of pancreatic ascites, only case reports and case series have been published, and no randomized controlled trials have been performed to find out which is the best therapeutic approach. The aim of this study was to evaluate the utility of the different treatments for pancreatic ascites by a thorough review of all case reports described in the literature in which an independent analysis of the efficacy of the treatment administered to each patient is possible.

METHODS

We conducted an analysis of all case reports and case series of pancreatic ascites published between 1975 and 2000 in which clinical data of every patient could be identified individually. A total of 139 cases were studied. Clinical characteristics, treatments administered, and response to therapy of every patient were registered. Conservative therapy included drainage of ascitic fluid, total parenteral nutrition and diet, and somatostatin analogues. Interventional therapy was either endoscopic or surgical.

RESULTS

After multivariate analysis, the only treatments related to success were surgery (adjusted OR = 8.2, 95% CI = 3.0-22.9) and transpapillary stent (adjusted OR = 7.3, 95% CI = 0.8-62.9). No significant relationship was found between failure or death and the use of other treatments, age, sex, year of publication, underlying disease, site of leakage, or serum amylase levels. The apparent lack of effect of somatostatin analogues could be attributed to the small number of cases and the heterogeneity of the dosages.

CONCLUSIONS

Conservative therapy is not advisable for pancreatic ascites because of the high proportion of failures. Interventional therapy with surgery or transpapillary stent has a positive effect in the clinical outcome.

Pancreatic ascites: study of therapeutic options by analysis of case reports and case series between the years 1975 and 2000

OBJECTIVE

Because of the low incidence of pancreatic ascites, only case reports and case series have been published, and no randomized controlled trials have been performed to find out which is the best therapeutic approach. The aim of this study was to evaluate the utility of the different treatments for pancreatic ascites by a thorough review of all case reports described in the literature in which an independent analysis of the efficacy of the treatment administered to each patient is possible.

METHODS

We conducted an analysis of all case reports and case series of pancreatic ascites published between 1975 and 2000 in which clinical data of every patient could be identified individually. A total of 139 cases were studied. Clinical characteristics, treatments administered, and response to therapy of every patient were registered. Conservative therapy included drainage of ascitic fluid, total parenteral nutrition and diet, and somatostatin analogues. Interventional therapy was either endoscopic or surgical.

RESULTS

After multivariate analysis, the only treatments related to success were surgery (adjusted OR = 8.2, 95% CI = 3.0-22.9) and transpapillary stent (adjusted OR = 7.3, 95% CI = 0.8-62.9). No significant relationship was found between failure or death and the use of other treatments, age, sex, year of publication, underlying disease, site of leakage, or serum amylase levels. The apparent lack of effect of somatostatin analogues could be attributed to the small number of cases and the heterogeneity of the dosages.

CONCLUSIONS

Conservative therapy is not advisable for pancreatic ascites because of the high proportion of failures. Interventional therapy with surgery or transpapillary stent has a positive effect in the clinical outcome.