Polarization scattering by intra-channel collisions.

We show that polarization modulated and polarization multiplexed transmission may be significantly impaired by the polarization scattering induced by intra-channel cross-phase modulation and four-wave mixing. In polarization multiplexed transmission, channel interleaving may be used to mitigate the effect when two-pulse collisions are dominant

Selective oxidation catalysis with Mn and H2O2:Conversion of alkenes to α-hydroxy ketones, C=C cleavage and mechanistic insights.

Oxidation is a term used to cover a wide range of processes that are central to life. Although we associate oxidation with ageing it is in fact central to living – from the uncontrolled radical chain reactions that drive combustion to the highly selective stepwise oxidations that your body uses to breakdown food (sugars and fats) to the bodies energy currencies, ATP, NADH etc., carbon dioxide and water. The selective stepwise oxidation of organic substrates is the central theme of this thesis in which a remarkably simple, in terms of usage and application, catalyst system is used together with hydrogen peroxide. The challenge is to carry out multistep oxidation of important organic building blocks to yield useful synthons for a wide range of fine chemical use. Critically, the catalyst system is based on an environmentally benign oxidant, hydrogen peroxide, which produces only water as a by-product, and a first row transition metal, manganese, which is readily available and non-toxic. The efficiency of the catalyst system furthermore is remarkable with turnover frequencies of over 30 s-1 and turn over numbers in excess of 300000 in some cases. The thesis examines several aspects of the chemistry of this system, beginning with selectivity – can we oxidize one compound selectively in the presence of another. The use of the catalyst system in multistep oxidations where the product of the first step becomes the starting material for the next is explored in depth and we show that we can provide a viable alternative to the hazardous use of ozone in organic synthesis. Finally we show that post-polymerization modification of rubbers is possible with this system using unusual solvent combinations, which opens up tremendous opportunities in expanding the scope of properties of these ubiquitous materials

Intra-channel nonlinearity in differentially phase-modulated transmission

The mechanisms responsible for nonlinear impairments in single-channel phase modulated system employing differential detection are investigated. The role of dispersion precompensation is discussed. It is shown that precompensation may be designed as to minimize the in-phase components of the fluctuations thus reducing nonlinear impairments. In differential-phase-shift-keying the effect of precompensation is stronger than in differential-quadrature-phase-shift-keying. The results of an analytic theory are compared with split-step based computer simulations using realistic system parameters

Off-line analysis in the manganese catalysed epoxidation of ethylene-propylene-diene rubber (EPDM) with hydrogen peroxide

The epoxidation of ethylene-propylene-diene rubber (EPDM) with 5-ethylidene-2-norbornene (ENB) as the diene to epoxidized EPDM (eEPDM) creates additional routes to cross-linking and reactive blending, as well as increasing the polarity and thereby the adhesion to polar materials, e.g., mineral fillers such as silica. The low solubility of apolar, high molecular weight polymers in the polar solvents constrains the catalytic method for epoxidation that can be applied. Here we have applied an in situ prepared catalyst comprising a manganese(ii) salt, sodium picolinate and a ketone to the epoxidation of EPDM rubber with hydrogen peroxide (H(2)O(2)) as the oxidant in a solvent mixture, that balances the need for polymer and catalyst/oxidant miscibility and solubility. Specifically, a mixture of cyclohexane and cyclohexanone is used, where cyclohexanone functions as a co-solvent as well as the ketone reagent. Reaction progress was monitored off-line through a combination of Raman and ATR-FTIR spectroscopies, which revealed that the reaction profile and the dependence on the composition of the catalyst are similar to those observed with low molar mass alkene substrates, under similar reaction conditions. The combination of spectroscopies offers a reliable method for off-line reaction monitoring of both the extent of the conversion of unsaturation (Raman) and the extent of epoxidation (FTIR) as well as determining side reactions, such as epoxide ring opening and further, aerobic oxidation. The epoxidation of EPDM described, in contrast to currently available methods, uses a non-scarce manganese catalyst and H(2)O(2), and avoids side reactions, such as those that can occur with peracids

Evaluation of patients treated for diabetic retinopathy: an analysis of the administrative databases of the Lazio Region

BACKGROUND: In Italy there are an estimated 4 million patients suffering from diabetes mellitus (DM). The most important ocular complication of DM is diabetic retinopathy (DR), which affects about one third of diabetic patients.AIMS: To identify, within the Lazio Region, the cohort of patients starting treatment for DME in the years 2010-2016 and calculating the annual cost of therapy; and to assess the appropriateness of the drugs prescribed.METHODS: From the Health Information System of the Lazio Region were identified all subjects who, in the 2010-2016 period, had received at least one prescription for dexamethasone intravitreal implant (i.i.) or intravitreal triamcinolone or ranibizumab or aflibercept or bevacizumab. For the cohort of users selected, the appropriateness of the treatment were evaluated calculating the number of administrations performed in the first four months of the index prescription and the number of administrations performed during the 12 months of treatment.RESULTS: In 2016, 7,265 patients in the Lazio Region received at least one prescription of ranibizumab (43.0%), aflibercept (37.5%) and dexamethasone i.i. (19.5%). Among the 3,416 patients naïve at 6 months, who started treatment in the 2013-2015 period and who did not switch to different drugs, 78.7% started treatment with ranibizumab, 16.0% with dexamethasone i.i. and 5.3% with aflibercept. The mean annual cost for the treatment of a patient with DME and naïve at 6 months was equal to € 2,388; a total cost for only the naïve patients selected in the 2013-2015 period is therefore estimated at approximately € 8.2 million. The average annual cost of dexamethasone i.i. treatment was € 1,497, lower than that of ranibizumab (€ 2,562) and aflibercept (€ 2,485). The expenditure for patients receiving less than 3 administrations of ranibizumab or aflibercept in the first 10 months of treatment was estimate equal to € 1.3 million.CONCLUSIONS: The administrations of dexamethasone i.i. are in line with what is indicated in the prescribing information, while for ranibizumab and aflibercept a potential under-use has been identified. A greater appropriateness of the drugs prescribed, accompanied by an optimal adherence to therapy, would strongly reduce the current waste of resources

Oxidation of Vicinal Diols to -Hydroxy Ketones with H2O2 and a Simple Manganese Catalyst

-Hydroxy ketones are valuable synthons in organic chemistry. Here we show that oxidation of vic-diols to -hydroxy ketones with H2O2 can be achieved with an in situ prepared catalyst based on manganese salts and pyridine-2-carboxylic acid. Furthermore the same catalyst is effective in alkene epoxidation, and it is shown that alkene oxidation with the Mn-II catalyst and H2O2 followed by Lewis acid ring opening of the epoxide and subsequent oxidation of the alkene to -hydroxy ketones can be achieved under mild (ambient) conditions

Plasmon-enhanced circular dichroism spectroscopy of chiral drug solutions

We investigate the potential of surface plasmon polaritons at noble metal interfaces for surface-enhanced chiroptical sensing of dilute chiral drug solutions with nano-litre volume. The high quality factor of surface plasmon resonances in both Otto and Kretschmann configurations enables the enhancement of circular dichroism thanks to the large near-field intensity of such plasmonic excitations. Furthermore, the subwavelength confinement of surface plasmon polaritons is key to attain chiroptical sensitivity to small amounts of drug volumes placed around $\simeq$ 100 nm by the metal surface. Our calculations focus on reparixin, a pharmaceutical molecule currently used in clinical studies for patients with community-acquired pneumonia, including COVID-19 and acute respiratory distress syndrome. Considering realistic dilute solutions of reparixin dissolved in water with concentration $\leq$ 5 mg/ml and nl volume, we find a circular-dichroism differential absorption enhancement factor of the order $\simeq$ 20 and chirality-induced polarization distortion upon surface plasmon polariton excitation. Our results are relevant for the development of innovative chiroptical sensors capable of measuring the enantiomeric imbalance of chiral drug solutions with nl volume

Screen Printed Electrode Based Detection Systems for the Antibiotic Amoxicillin in Aqueous Samples Utilising Molecularly Imprinted Polymers as Synthetic Receptors

Molecularly Imprinted Polymers (MIPs) were synthesised for the selective detection of amoxicillin in aqueous samples. Different functional monomers were tested to determine the optimal composition via batch rebinding experiments. Two different sensor platforms were tested using the same MIP solution; one being bulk synthesized and surface modified Screen Printed Electrodes (SPEs) via drop casting the microparticles onto the electrode surface and the other being UV polymerized directly onto the SPE surface in the form of a thin film. The sensors were used to measure amoxicillin in conjunction with the Heat-Transfer Method (HTM), a low-cost and simple thermal detection method that is based on differences in the thermal resistance at the solid–liquid interface. It was demonstrated that both sensor platforms could detect amoxicillin in the relevant concentration range with Limits of Detection (LOD) of 1.89 ± 1.03 nM and 0.54 ± 0.10 nM for the drop cast and direct polymerisation methods respectively. The sensor platform utilising direct UV polymerisation exhibited an enhanced response for amoxicillin detection, a reduced sensor preparation time and the selectivity of the platform was proven through the addition of nafcillin, a pharmacophore of similar shape and size. The use of MIP-modified SPEs combined with thermal detection provides sensors that can be used for fast and low-cost detection of analytes on-site, which holds great potential for contaminants in environmental aqueous samples. The platform and synthesis methods are generic and by adapting the MIP layer it is possible to expand this sensor platform to a variety of relevant targets