Enhancing Liquid-Phase Olefin-Paraffin Separations Using Novel Silver-Based Ionic Liquids

This paper describes the extraction of C5-C8 linear α-olefins from olefin/paraffin mixtures of the same carbon number using silver(I)/N,N-dimethylbenzamide bis(trifluoromethylsulfonyl)imide ([Ag(DMBA)₂][Tf₂N]) or silver(I)/propylamine bis(trifluoromethylsulfonyl)imide ([Ag(PrNH₂)₂][Tf₂N]) as the extracting agent. The separation performance of the system increased with increasing chain length. [Ag(DMBA)₂][Tf₂N] appeared to outperform [Ag(PrNH₂)₂][Tf₂N] in terms of both selectivity and distribution coefficient. The [Ag(DMBA)₂][Tf₂N] system was successfully modeled using the universal quasi-chemical activity coefficient (UNIQUAC) model. These results support the potential future development of amine/amide-based ligands for producing soluble silver complexes useful for the separation of olefins from paraffins.

Ataluren for the treatment of nonsense-mutation cystic fibrosis: a randomised, double-blind, placebo-controlled phase 3 trial

Background: Ataluren was developed to restore functional protein production in genetic disorders caused by nonsense mutations, which are the cause of cystic fibrosis in 10% of patients. This trial was designed to assess the efficacy and safety of ataluren in patients with nonsense-mutation cystic fibrosis. 

Methods: This randomised, double-blind, placebo-controlled, phase 3 study enrolled patients from 36 sites in 11 countries in North America and Europe. Eligible patients with nonsense-mutation cystic fibrosis (aged ≥6 years; abnormal nasal potential difference; sweat chloride >40 mmol/L; forced expiratory volume in 1 s [FEV₁] ≥40% and ≤90%) were randomly assigned by interactive response technology to receive oral ataluren (10 mg/kg in morning, 10 mg/kg midday, and 20 mg/kg in evening) or matching placebo for 48 weeks. Randomisation used a block size of four, stratified by age, chronic inhaled antibiotic use, and percent-predicted FEV₁. The primary endpoint was relative change in percent-predicted FEV₁ from baseline to week 48, analysed in all patients with a post-baseline spirometry measurement. This study is registered with ClinicalTrials.gov, number NCT00803205. 

Findings: Between Sept 8, 2009, and Nov 30, 2010, 238 patients were randomly assigned, of whom 116 in each treatment group had a valid post-baseline spirometry measurement. Relative change from baseline in percent-predicted FEV₁ did not differ significantly between ataluren and placebo at week 48 (-2·5% vs -5·5%; difference 3·0% [95% CI -0·8 to 6·3]; p=0·12). The number of pulmonary exacerbations did not differ significantly between treatment groups (rate ratio 0·77 [95% CI 0·57-1·05]; p=0·0992). However, post-hoc analysis of the subgroup of patients not using chronic inhaled tobramycin showed a 5·7% difference (95% CI 1·5-10·1) in relative change from baseline in percent-predicted FEV₁ between the ataluren and placebo groups at week 48 (-0·7% [-4·0 to 2·1] vs -6·4% [-9·8 to -3·7]; nominal p=0·0082), and fewer pulmonary exacerbations in the ataluern group (1·42 events [0·9-1·9] vs 2·18 events [1·6-2·7]; rate ratio 0·60 [0·42-0·86]; nominal p=0·0061). Safety profiles were generally similar for ataluren and placebo, except for the occurrence of increased creatinine concentrations (ie, acute kidney injury), which occurred in 18 (15%) of 118 patients in the ataluren group compared with one (<1%) of 120 patients in the placebo group. No life-threatening adverse events or deaths were reported in either group. I

nterpretation: Although ataluren did not improve lung function in the overall population of nonsense-mutation cystic fibrosis patients who received this treatment, it might be beneficial for patients not taking chronic inhaled tobramycin. 

Funding: PTC Therapeutics, Cystic Fibrosis Foundation, US Food and Drug Administration's Office of Orphan Products Development, and the National Institutes of Health. 

Effect of radium-223 dichloride on symptomatic skeletal events in patients with castration-resistant prostate cancer and bone metastases: results from a phase 3, double-blind, randomised trial

BACKGROUND: Bone metastases frequently cause skeletal events in patients with metastatic castration-resistant prostate cancer. Radium-223 dichloride (radium-223) selectively targets bone metastases with high-energy, short-range α-particles. We assessed the effect of radium-223 compared with placebo in patients with castration-resistant prostate cancer and bone metastases.

METHODS: In this phase 3, double-blind, randomised ALSYMPCA trial, we enrolled patients who had symptomatic castration-resistant prostate cancer with two or more bone metastases and no known visceral metastases, who were receiving best standard of care, and had previously either received or were unsuitable for docetaxel. Patients were stratified by previous docetaxel use, baseline total alkaline phosphatase level, and current bisphosphonate use, then randomly assigned (2:1) to receive either six intravenous injections of radium-223 (50 kBq/kg) or matching placebo; one injection was given every 4 weeks. Randomisation was done with an interactive voice response system, taking into account trial stratification factors. Participants and investigators were masked to treatment assignment. The primary endpoint was overall survival, which has been reported previously. Here we report on time to first symptomatic skeletal event, defined as the use of external beam radiation to relieve bone pain, or occurrence of a new symptomatic pathological fracture (vertebral or non-verterbal), or occurence of spinal cord compression, or tumour-related orthopeadic surgical intervention. All events were required to be clinically apparent and were not assessed by periodic radiological review. Statistical analyses of symptomatic skeletal events were based on the intention-to-treat population. The study has been completed and is registered with ClinicalTrials.gov, number NCT00699751.

FINDINGS: Between June 12, 2008, and Feb 1, 2011, 921 patients were enrolled, of whom 614 (67%) were randomly assigned to receive radium-223 and 307 (33%) placebo. Symptomatic skeletal events occurred in 202 (33%) of 614 patients in the radium-223 group and 116 (38%) of 307 patients in the placebo group. Time to first symptomatic skeletal event was longer with radium-223 than with placebo (median 15·6 months [95% CI 13·5-18·0] vs 9·8 months [7·3-23·7]; hazard ratio [HR]=0·66, 95% CI 0·52-0·83; p=0·00037). The risks of external beam radiation therapy for bone pain (HR 0·67, 95% CI 0·53-0·85) and spinal cord compression (HR=0·52, 95% CI 0·29-0·93) were reduced with radium-233 compared with placebo. Radium-223 treatment did not seem to significantly reduce the risk of symptomatic pathological bone fracture (HR 0·62, 95% CI 0·35-1·09), or the need for tumour-related orthopaedic surgical intervention (HR 0·72, 95% CI 0·28-1·82).

INTERPRETATION: Radium-223 should be considered as a treatment option for patients with castration-resistant prostate cancer and symptomatic bone metastases.

FUNDING: Algeta and Bayer HealthCare Pharmaceuticals.

Pre-Processing Power Traces with a Phase-Sensitive Detector

As cryptographic implementations are increasingly subsumed as functional blocks within larger systems on chip, it becomes more difficult to identify the power consumption signatures of cryptographic operations amongst other unrelated processing activities. In addition, at higher clock frequencies, the current decay between successive processing rounds is only partial, making it more difficult to apply existing pattern matching techniques in side-channel analysis. We show however, through the use of a phase-sensitive detector, that power traces can be pre-processed to generate a filtered output which exhibits an enhanced round pattern, enabling the identification of locations on a device where encryption operations are occurring and also assisting with the re-alignment of power traces for side-channel attacks.

Quasi steady state and dynamic hygrothermal performance of fibrous Hemp and Stone Wool insulations: Two innovative laboratory based investigations

Moisture and heat management properties of Hemp and Stone Wool insulations were studied by mounting them between a hot and a cold climate chamber. Both insulations were exposed to identical hygrothermal boundary conditions. Quasi steady state and dynamic tests were carried out at a range of relative humidity exposures. The likelihood of interstitial condensation was assessed and equivalent thermal conductivity values of the insulations were determined. The adsorption-desorption isotherms of the insulations were also determined in a dynamic vapour sorption (DVS) instrument. It was observed that the likelihood of condensation was higher in Stone Wool insulation than in Hemp insulation. Hemp insulation performed better in managing moisture due to its high hygric inertia and water absorption capacity. It was observed that the equivalent thermal conductivity of Stone Wool insulation was dependent on enthalpy flow and phase change of moisture. The equivalent thermal conductivity of Hemp insulation was close to its declared thermal conductivity in dynamic conditions when high relative humidity exposures were transient. In quasi steady state boundary conditions, when the insulation was allowed to reach the equilibrium moisture content at ranges of relative humidity, there was a moisture dependent increase of thermal conductivity in Hemp insulation.

Wireless GPS-based phase-locked synchronization system for outdoor environment.

Synchronization of data coming from different sources is of high importance in biomechanics to ensure reliable analyses. This synchronization can either be performed through hardware to obtain perfect matching of data, or post-processed digitally. Hardware synchronization can be achieved using trigger cables connecting different devices in many situations; however, this is often impractical, and sometimes impossible in outdoors situations. The aim of this paper is to describe a wireless system for outdoor use, allowing synchronization of different types of - potentially embedded and moving - devices. In this system, each synchronization device is composed of: (i) a GPS receiver (used as time reference), (ii) a radio transmitter, and (iii) a microcontroller. These components are used to provide synchronized trigger signals at the desired frequency to the measurement device connected. The synchronization devices communicate wirelessly, are very lightweight, battery-operated and thus very easy to set up. They are adaptable to every measurement device equipped with either trigger input or recording channel. The accuracy of the system was validated using an oscilloscope. The mean synchronization error was found to be 0.39 μs and pulses are generated with an accuracy of <2 μs. The system provides synchronization accuracy about two orders of magnitude better than commonly used post-processing methods, and does not suffer from any drift in trigger generation.

Monte Carlo study of the XY-model on quasi-periodic lattices

Monte Carlo Simulations were carried out using a nearest neighbour ferromagnetic XYmodel, on both 2-D and 3-D quasi-periodic lattices. In the case of 2-D, both the unfrustrated and frustrated XV-model were studied. For the unfrustrated 2-D XV-model, we have examined the magnetization, specific heat, linear susceptibility, helicity modulus and the derivative of the helicity modulus with respect to inverse temperature. The behaviour of all these quatities point to a Kosterlitz-Thouless transition occuring in temperature range Te == (1.0 -1.05) JlkB and with critical exponents that are consistent with previous results (obtained for crystalline lattices) . However, in the frustrated case, analysis of the spin glass susceptibility and EdwardsAnderson order parameter, in addition to the magnetization, specific heat and linear susceptibility, support a spin glass transition. In the case where the 'thin' rhombus is fully frustrated, a freezing transition occurs at Tf == 0.137 JlkB , which contradicts previous work suggesting the critical dimension of spin glasses to be de > 2 . In the 3-D systems, examination of the magnetization, specific heat and linear susceptibility reveal a conventional second order phase transition. Through a cumulant analysis and finite size scaling, a critical temperature of Te == (2.292 ± 0.003) JI kB and critical exponents of 0:' == 0.03 ± 0.03, f3 == 0.30 ± 0.01 and I == 1.31 ± 0.02 have been obtained.

Investigation of Frustrated Quasi-One-Dimensional Quantum Spin-Chain Materials

Copper arsenite CuAs2O4 and Copper antimonite CuSb2O4 are S=1/2 (Cu2+ 3d9 electronic configuration) quasi-one-dimensional quantum spin-chain compounds. Both compounds crystallize with tetragonal structures containing edge sharing CuO6 octahedra chains which experience Jahn-Teller distortions. The basal planes of the octahedra link together to form CuO2 ribbon-chains which harbor Cu2+ spin-chains. These compounds are magnetically frustrated with competing nearest-neighbour and next-nearest-neighbour intrachain spin-exchange interactions. Despite the similarities between CuAs2O4 and CuSb2O4, they exhibit very different magnetic properties. In this thesis work, the physical properties of CuAs2O4 and CuSb2O4 are investigated using a variety of experimental techniques which include x-ray diffraction, magnetic susceptibility measurements, heat capacity measurements, Raman spectroscopy, electron paramagnetic resonance, neutron diffraction, and dielectric capacitance measurements. CuAs2O4 exhibits dominant ferromagnetic nearest-neighbour and weaker antiferromagnetic next-nearest-neighbour intrachain spin-exchange interactions. The ratio of the intrachain interactions amounts to Jnn/Jnnn = -4.1. CuAs2O4 was found to order with a ferromagnetic groundstate below TC = 7.4 K. An extensive physical characterization of the magnetic and structural properties of CuAs2O4 was carried out. Under the effect of hydrostatic pressure, CuAs2O4 was found to undergo a structural phase transition at 9 GPa to a new spin-chain structure. The structural phase transition is accompanied by a severe alteration of the magnetic properties. The high-pressure phase exhibits dominant ferromagnetic next-nearest-neighbour spin-exchange interactions and weaker ferromagnetic nearest-neighbour interactions. The ratio of the intrachain interactions in the high-pressure phase was found to be Jnn/Jnnn = 0.3. Structural and magnetic characterizations under hydrostatic pressure are reported and a relationship between the structural and magnetic properties was established. CuSb2O4 orders antiferromagnetically below TN = 1.8 K with an incommensurate helicoidal magnetic structure. CuSb2O4 is characterized by ferromagnetic nearest-neighbour and antiferromagnetic next-nearest-neighbour spin-exchange interactions with Jnn/Jnnn = -1.8. A (H, T) magnetic phase diagram was constructed using low-temperature magnetization and heat capacity measurements. The resulting phase diagram contains multiple phases as a consequence of the strong intrachain magnetic frustration. Indications of ferroelectricity were observed in the incommensurate antiferromagnetic phase.

Caractérisation cytogénétique et moléculaire des translocations chromosomiques dans la phase blastique de la leucémie myéloïde chronique

La leucémie myéloïde chronique (LMC) est un modèle d’évolution tumorale dans les cancers humains. Le processus d’évolution de la LMC de la phase chronique (PC) à la phase blastique (PB) est caractérisé par un arrêt de différenciation et l’acquisition de la capacité d’autorenouvellement incontrôlé d’une cellule souche ou d’un progéniteur hématopoïétique. La LMC en PB est associée à la présence d’anomalies génétiques additionnelles à la fusion BCR-ABL1 qui résulte de la translocation chromosomique t(9;22). Contrairement aux patients en PC, les patients en PB de la LMC n’obtiennent pas une réponse moléculaire complète à long terme avec 1’Imatinib mesylate, un inhibiteur de la tyrosine kinase (ITK) BCR-ABL1. De plus, les ITKs de deuxième et troisième générations sont moins efficaces en PB de la LMC lorsque les cellules leucémiques ont acquis une résistance au traitement indépendante des mutations de BCR-ABL1. Les mécanismes moléculaires des voies de signalisation impliquées dans la progression de la LMC en PB ne sont pas entièrement élucidés. Le but de notre travail est de caractériser de nouvelles anomalies génétiques dans la PB de la LMC. Nous avons identifié en cytogénétique, quatre nouvelles translocations chromosomiques : t(1;21)(p36;q22), t(7;17)(p15;q22), t(8;17)(q11;q22) et t(2;12)(q31;p13) dans les cellules leucémiques de patients en PB de la LMC résistants au traitement. En utilisant des techniques d'hybridation in situ en fluorescence, de RT-PCR et de séquençage, nous avons délimité les régions à investiguer au niveau des points de cassure et identifié un réarrangement de plusieurs gènes codant pour des facteurs de transcription importants lors de l’hématopoïèse tels que RUNX1, ETV6, PRDM16 et HOXA. L’altération de ces gènes pourrait expliquer l’arrêt de différenciation et/ou l’acquisition de la capacité d’autorenouvellement caractéristiques de la LMC en PB. Nous avons identifié les fusions RUNX1-PRDM16, MSI2-HOXA, MSI2-SOX17 et ETV6-HOXD11, respectivement associées aux translocations chromosomiques t(1;21), t(7;17), t(8;17) et t(2;12). Ces fusions génèrent différents transcrits alternatifs qui maintiennent et altèrent le cadre ouvert de lecture. L’analyse des séquences des transcrits chimériques identifiés dans ce projet, incluant RUNX1-PRDM16, MSI2-HOXA9, MSI2-HOXA10, MSI2-HOXA11 et ETV6-HOXD11, nous a permis de prédire les domaines fonctionnels potentiellement présents au niveau des protéines chimériques prédites. Les transcrits de fusion qui respectent le cadre ouvert de lecture peuvent générer des domaines fonctionnels des deux partenaires. C’est le cas des deux transcrits identifiés pour la fusion RUNX1-PRDM16 où le domaine de liaison à l’ADN RHD (Runt homology domain) de RUNX1 est fusionné avec la quasi-totalité des domaines de PRDM16. Les transcrits de fusion qui ne respectent pas le cadre ouvert de lecture donnent des formes tronquées des transcrits RUNX1, MSI2 et ETV6. La juxtaposition des régions promotrices de ces derniers en 5’ de leurs partenaires entraîne l’activation de la forme courte oncogénique de PRDM16 dans la t(1;21) ou de différents gènes HOXA/D dans les t(7;17) et t(2;12), ainsi que l’expression aberrante d’un nouveau transcrit alternatif de SOX17 dans la t(8;17). Notre étude nous a permis d’identifier de nouveaux gènes de fusion et/ou une activation de gènes qui pourraient coopérer avec la fusion BCR-ABL1 dans la progression de la LMC et être impliqués dans la résistance au traitement de la LMC en phase avancée. La caractérisation des événements génétiques associés à la transformation blastique de la LMC est essentielle pour l’investigation des voies moléculaires impliquées dans cette phase de la maladie. Investiguer la résistance au traitement de ces patients pourrait aussi contribuer à identifier de nouvelles cibles thérapeutiques dans cette leucémie.

Étude du contrôle postural quasi-statique et dynamique en position debout des personnes ayant une lésion médullaire incomplète.

L’atteinte sensorimotrice découlant d’une lésion médullaire traumatique affecte la capacité à se tenir debout de façon sécuritaire. Chez les individus ayant une lésion médullaire incomplète, les chutes lors des tâches locomotrices sont fréquentes après la réadaptation, entraînant des blessures qui affectent la participation sociale et la qualité de vie. Une meilleure compréhension du contrôle postural en clinique aiderait à cibler des interventions efficaces à ce niveau. L’objectif général de cette thèse était donc d’étudier le contrôle postural debout lors de tâches variées chez les personnes avec lésion médullaire traumatique en utilisant une approche biomécanique. Les objectifs spécifiques étaient d’étudier divers aspects du contrôle postural en lien avec chacune des tâches et d’identifier les variables prédictives de la stabilité. Vingt-cinq (25) personnes ayant une lésion médullaire traumatique incomplète ont été recrutées. Elles ont été évaluées au laboratoire d’analyse de mouvement lors du maintien de la station debout quasi-statique yeux ouverts et fermés, de l’exécution d’un test des limites de stabilité multidirectionnelles, de la marche naturelle et de l’initiation et l’arrêt de la marche. Des mesures biomécaniques caractérisant le déplacement du centre de pression (COP) ainsi que le modèle du contrôle postural dynamique des forces stabilisantes et déstabilisantes ont été utilisés pour comparer le contrôle postural des patients à celui d’un groupe formé de 33 personnes en santé. Les résultats ont montré une diminution du contrôle postural quasi-statique et dynamique chez les personnes ayant une lésion médullaire comparativement aux personnes en santé. Cette diminution s’accompagnait d’une contribution élevée des informations visuelles à la station debout quasi-statique qui était associée au score du mini BESTest. Le déplacement du COP lors du test des limites de stabilité multidirectionnelle se caractérisait par une difficulté à suivre la direction indiquée. Ce manque de précision causait une augmentation du trajet nécessaire pour atteindre la distance maximale dans chacune des directions. Les résultats au maintien de la station debout quasi-statique et au test des limites de stabilité multidirectionnelle n’étaient pas corrélés. La phase unipodale de la marche des personnes ayant une lésion médullaire différait de celle des personnes en santé par une force stabilisante maximale moindre et une force déstabilisante plus grande alors que l’arrêt de la marche se révélait plus instable que l’initiation de la marche chez les personnes ayant une lésion médullaire. Pour l’ensemble des tâches de marche, la vitesse du COM et la distance entre le COP et la base de support étaient les facteurs explicatifs principaux des forces stabilisantes et déstabilisantes. En somme, les résultats confirment l’impression clinique d’une atteinte générale du contrôle postural debout des personnes ayant une lésion médullaire; ils en précisent les caractéristiques et ciblent les paramètres à considérer dans la rééducation.

Immersive Projection for biochemical pattern matching

In all biological processes, protein molecules and other small molecules interact to function and form transient macromolecular complexes. This interaction of two or more molecules can be described by a docking event. Docking is an important phase for structure-based drug design strategies, as it can be used as a method to simulate protein-ligand interactions. Various docking programs exist that allow automated docking, but most of them have limited visualization and user interaction. It would be advantageous if scientists could visualize the molecules participating in the docking process, manipulate their structures and manually dock them before submitting the new conformations to an automated docking process in an immersive environment, which can help stimulate the design/docking process. This also could greatly reduce docking time and resources. To achieve this, we propose a new virtual modelling/docking program, whereby the advantages of virtual modelling programs and the efficiency of the algorithms in existing docking programs will be merged.

The quasi-nondispersive regimes of long extratropical baroclinic rossby waves over (slowly varying) topography

Actual energy paths of long, extratropical baroclinic Rossby waves in the ocean are difficult to describe simply because they depend on the meridional-wavenumber-to-zonal-wavenumber ratio tau, a quantity that is difficult to estimate both observationally and theoretically. This paper shows, however, that this dependence is actually weak over any interval in which the zonal phase speed varies approximately linearly with tau, in which case the propagation becomes quasi-nondispersive (QND) and describable at leading order in terms of environmental conditions (i.e., topography and stratification) alone. As an example, the purely topographic case is shown to possess three main kinds of QND ray paths. The first is a topographic regime in which the rays follow approximately the contours f/h(alpha c) = a constant (alpha(c) is a near constant fixed by the strength of the stratification, f is the Coriolis parameter, and h is the ocean depth). The second and third are, respectively, "fast" and "slow" westward regimes little affected by topography and associated with the first and second bottom-pressure-compensated normal modes studied in previous work by Tailleux and McWilliams. Idealized examples show that actual rays can often be reproduced with reasonable accuracy by replacing the actual dispersion relation by its QND approximation. The topographic regime provides an upper bound ( in general a large overestimate) of the maximum latitudinal excursions of actual rays. The method presented in this paper is interesting for enabling an optimal classification of purely azimuthally dispersive wave systems into simpler idealized QND wave regimes, which helps to rationalize previous empirical findings that the ray paths of long Rossby waves in the presence of mean flow and topography often seem to be independent of the wavenumber orientation. Two important side results are to establish that the baroclinic string function regime of Tyler and K se is only valid over a tiny range of the topographic parameter and that long baroclinic Rossby waves propagating over topography do not obey any two-dimensional potential vorticity conservation principle. Given the importance of the latter principle in geophysical fluid dynamics, the lack of it in this case makes the concept of the QND regimes all the more important, for they are probably the only alternative to provide a simple and economical description of general purely azimuthally dispersive wave systems.

Quasi-biennial oscillation and tracer distributions in a coupled chemistry-climate model

[ 1] We have used a fully coupled chemistry-climate model (CCM), which generates its own wind and temperature quasi-biennial oscillation (QBO), to study the effect of coupling on the QBO and to examine the QBO signals in stratospheric trace gases, particularly ozone. Radiative coupling of the interactive chemistry to the underlying general circulation model tends to prolong the QBO period and to increase the QBO amplitude in the equatorial zonal wind in the lower and middle stratosphere. The model ozone QBO agrees well with Stratospheric Aerosol and Gas Experiment II and Total Ozone Mapping Spectrometer satellite observations in terms of vertical and latitudinal structure. The model captures the ozone QBO phase change near 28 km over the equator and the column phase change near +/- 15 degrees latitude. Diagnosis of the model chemical terms shows that variations in NOx are the main chemical driver of the O-3 QBO around 35 km, i.e., above the O-3 phase change.

Precision of quasi-optical null-balanced bridge techniques for transmission and reflection coefficient measurements

The precision of quasioptical null-balanced bridge instruments for transmission and reflection coefficient measurements at millimeter and submillimeter wavelengths is analyzed. A Jones matrix analysis is used to describe the amount of power reaching the detector as a function of grid angle orientation, sample transmittance/reflectance and phase delay. An analysis is performed of the errors involved in determining the complex transmission and reflection coefficient after taking into account the quantization error in the grid angle and micrometer readings, the transmission or reflection coefficient of the sample, the noise equivalent power of the detector, the source power and the post-detection bandwidth. For a system fitted with a rotating grid with resolution of 0.017 rad and a micrometer quantization error of 1 μm, a 1 mW source, and a detector with a noise equivalent power 5×10−9 W Hz−1/2, the maximum errors at an amplitude transmission or reflection coefficient of 0.5 are below ±0.025.

Response of the northern stratospheric polar vortex to the seasonal alignment of QBO phase transitions

This study considers the strength of the Northern Hemisphere Holton-Tan effect (HTE) in terms of the phase alignment of the quasi-biennial oscillation (QBO) with respect to the annual cycle. Using the ERA-40 Reanalysis, it is found that the early winter (Nov–Dec) and late winter (Feb–Mar) relation between QBO phase and the strength of the stratospheric polar vortex is optimized for subsets of the 44-year record that are chosen on the basis of the seasonality of QBO phase transitions at the 30 hPa level. The timing of phase transitions serves as a proxy for changes in the vertical structure of the QBO over the whole depth of the tropical stratosphere. The statistical significance of the Nov–Dec (Feb–Mar) HTE is greatest when 30 hPa QBO phase transitions occur 9–14 (4–9) months prior to the January of the NH winter in question. This suggests that there exists for both early and late winter a vertical structure of tropical stratospheric winds that is most effective at influencing the interannual variability of the polar vortex, and that an early (late) winter HTE is associated with an early (late) progression of QBO phase towards that structure. It is also shown that the seasonality of QBO phase transitions at 30 hPa varies on a decadal timescale, with transitions during the first half of the calendar year being relatively more common during the first half of the tropical radiosonde wind record. Combining these two results suggests that decadal changes in HTE strength could result from the changing seasonality of QBO phase transitions. Citation: Anstey, J. A., and T. G. Shepherd (2008), Response of the northern stratospheric polar vortex to the seasonal alignment of QBO phase transitions, Geophys. Res. Lett., 35, L22810, doi:10.1029/2008GL035721.