Mapping the stability diagram of a quadrupole mass spectrometer with a static transverse magnetic field applied.

Previous experimental and theoretical work identified that the application of a static magnetic (B) field can improve the resolution of a quadrupole mass spectrometer (QMS) and this simple method of performance enhancement offers advantages for field deployment. Presented here are further data showing the effect of the transverse magnetic field upon the QMS performance. For the first time, the asymmetry in QMS operation with B x and B y is considered and explained in terms of operation in the fourth quadrant of the stability diagram. The results may be explained by considering the additional Lorentz force (v x B) experienced by the ion trajectories in each case. Using our numerical approach, we model not only the individual ion trajectories for a transverse B field applied in x and y but also the mass spectra and the effect of the magnetic field upon the stability diagram. Our theoretical findings, confirmed by experiment, show an improvement in resolution and ion transmission by application of magnetic field for certain operating conditions.

A method of computing accurate 3D fields of a quadrupole mass filter and their use for prediction of filter behavior.

A method is described that enables the three-dimensional fields of a simple quadrupole mass filter (QMF) to be determined to a high accuracy. The technique produces accurate field values in the fringe field region as well as in the center of the filter. Using fields obtained typical filter performance is determined and shown to differ from that predicted when fringe fields are ignored. The computed performance shows features obtained experimentally and displays more complex variation with ion mass and other parameters than when fringe fields are ignored.

Effect of an axial magnetic field on the performance of a quadrupole mass spectrometer.

We consider the case of a quadrupole mass spectrometer (QMS) in which a static magnetic field is applied axially in the z-direction along the length of the mass filter. The theoretical approach assumed in the model is that the QMS contains hyperbolic rods as electrodes and that the magnetic field acts over the full length of the mass filter assembly. Initial experimental results with argon and helium for a low-resolution instrument confirm the predicted theoretical trends. The analysis also predicts for which values of operating parameters an enhancement of the instrument resolution is achieved when an axial magnetic field is applied. The model predicts instrument resolution R >3000 for a QMS with a 200 mm long mass filter via application of an axial magnetic field.

Prediction of the effects of imperfect construction of a QMS filter.

Modelling techniques have previously predicted the observed behaviour of perfectly manufactured QMS mass filters. These methods are extended to examination of the behaviour of imperfect QMS filters; this examination considers the behaviour of QMS filters with one rod displaced radially inward as this is a simple manufacturing defect that arises when a rod does not fit correctly into the mounting. The results demonstrate the well known, but poorly documented property, that exchanging the connections of a poorly performing QMS device sometimes improves performance. This is shown to arise because only a displacement of a y-rod produces a large effect. The results also show that displacement of a y-rod may produce a spurious additional peak known as a precursor. More detailed investigation suggests that precursors are not separate peaks but are formed because a section of the main peak is removed causing an apparent double peak. Finally results confirm that adjustment of the voltage applied to a displaced rod can be used to significantly improve the QMS behaviour. A small change by a fraction alpha in the position of a single rod may be compensated by a change of 2 x alpha in the voltage applied to that rod.

A multicenter, randomized, double-blind trial of tazarotene 0.1% cream in the treatment of photodamage.

BACKGROUND: Previous studies indicate that tazarotene is efficacious in reducing signs of photodamage. Objective We sought to confirm the efficacy and tolerability of tazarotene 0.1% cream in the treatment of facial photodamage. METHODS: A total of 568 patients with at least moderate fine wrinkling or mottled hyperpigmentation applied tazarotene 0.1% cream or vehicle cream to their face once daily for 24 weeks. RESULTS: Tazarotene cream was significantly more effective than vehicle in reducing fine wrinkles, mottled hyperpigmentation, lentigines, irregular depigmentation, apparent pore size, elastosis, tactile roughness, and an overall integrated assessment of photodamage. Significance was achieved as early as week 2 for some parameters and had not plateaued by week 24. The majority of patients reported improvements in their photodamage as early as week 4. Adverse events were predominantly mild or moderate signs or symptoms of skin irritation. CONCLUSION: Once-daily tazarotene 0.1% cream is effective in ameliorating multiple signs of facial photodamage.

Effects of tazarotene 0.1 % cream in the treatment of facial acne vulgaris: pooled results from two multicenter, double-blind, randomized, vehicle-controlled, parallel-group trials.

BACKGROUND: Topical retinoids are one of the most effective classes of topical drugs used to treat acne vulgaris. The effects of the gel formulation of the topical retinoid tazarotene have been widely reported, but few data on the cream formulation are available. OBJECTIVE: The primary aim of the 2 studies reported in this article was to determine the effects of tazarotene 0.1 % cream in patients with facial acne vulgaris. METHODS: Two randomized, double-blind, parallel-group studies were performed. The first was conducted at 14 investigational sites across the United States, and the second took place at 15 sites, with 5 of these providing blood samples for analysis of tazarotenic acid. In both studies, patients aged > or =12 years with facial acne vulgaris were randomized to receive tazarotene or vehicle cream QD for 12 weeks. Lesion counts (noninflammatory, inflammatory, and total) and overall clinical and global assessments were made at weeks 0 (baseline), 4, 8, and 12. Adverse events (AEs) were monitored throughout the study In one of the studies, therapeutic drug monitoring was performed at weeks 4 and 8 in members of the study population who gave consent for blood withdrawal. RESULTS: Eight hundred forty-seven patients were enrolled in the 2 studies (430 males, 417 females; mean age,19 years; age range, 11-52 years [1 patient was entered into the study at age 11 years, in violation of the protocol]). At 12 weeks, the median percentage changes from baseline in all 3 lesion counts were significantly lower with tazarotene than with vehicle (all, P < 0.001), as were the overall clinical and global responses (both, P < 0.001). Treatment-related AEs whose incidence was higher with tazarotene than with vehicle included desquamation, dry skin, erythema, a burning sensation on the skin, and skin irritation (all, P < 0.001) and pruritus (P < 0.01); most (83%-98%) were mild or moderate. Systemic exposure to tazarotenic acid was limited (mean, <0.1 ng/mL) and did not increase with time. CONCLUSIONS: In these 2 studies in adolescent and adult patients with facial acne vulgaris, tazarotene 0.1%cream QD for 12 weeks was effective and well tolerated. Systemic exposure to tazarotenic acid was limited.

Tazarotene cream in the treatment of psoriasis: Two multicenter, double-blind, randomized, vehicle-controlled studies of the safety and efficacy of tazarotene creams 0.05% and 0.1% applied once daily for 12 weeks.

BACKGROUND: Tazarotene in a gel formulation is widely used in the treatment of psoriasis. OBJECTIVE: To determine the efficacy and safety of tazarotene 0.1% and 0.05% creams in the treatment of psoriasis. METHODS: A total of 1303 patients participated in 2 clinical trials. Patients applied tazarotene creams 0.1% and 0.05% or vehicle once daily to all psoriatic lesions for 12 weeks followed by a 12-week posttreatment period. RESULTS: Both creams were significantly more effective than vehicle on the basis of an overall assessment of psoriasis, a global response to treatment, and reduction in plaque elevation and scaling. Therapeutic effect was maintained during the posttreatment period. Common adverse events included signs and symptoms of skin irritation. CONCLUSION: Tazarotene creams were associated with significant reductions in the severity of the clinical signs of psoriasis and were found to be safe with acceptable tolerability. Tazarotene cream 0.1% was generally more effective, although slightly less well tolerated, than the 0.05% cream.

Efficacy of 0.1% tazarotene cream for the treatment of photodamage: a 12-month multicenter, randomized trial.

OBJECTIVE: To determine the efficacy and safety of 0.1% tazarotene cream for the treatment of photodamage. DESIGN: A 24-week multicenter, double-blind, randomized, vehicle-controlled intervention study followed by a 28-week open-label extension. SETTING: Ambulatory patients in private and institutional practice. PATIENTS: Of 563 patients with facial photodamage, 91% and 86% completed the double-blind and open-label phases, respectively. In the double-blind phase, 20 of 283 tazarotene-treated patients and 1 of 280 vehicle-treated patients discontinued treatment owing to adverse events. INTERVENTION: Once-daily application of 0.1% tazarotene cream or nonmedicated vehicle cream to the face for 24 weeks. Then, all continuing patients received treatment with 0.1% tazarotene cream for another 28 weeks. MAIN OUTCOME MEASURES: Primarily, fine wrinkling and mottled hyperpigmentation. Also, lentigines, elastosis, pore size, irregular depigmentation, tactile roughness, coarse wrinkling, telangiectasia, actinic keratoses, overall integrated assessment of photodamage, global response to treatment, patients' overall assessment of photodamage, and plasma levels of tazarotenic acid. RESULTS: Compared with the vehicle, at week 24 tazarotene resulted in a significantly greater incidence of patients achieving treatment success (>or=50% global improvement) and at least a 1-grade improvement in fine wrinkling, mottled hyperpigmentation, lentigines, elastosis, pore size, irregular depigmentation, tactile roughness, coarse wrinkling, and the overall integrated assessment of photodamage (P<.01). Additional clinical improvement occurred with continued tazarotene treatment and had not plateaued by week 52. Plasma tazarotenic acid concentrations did not exceed 0.71 ng/mL. CONCLUSIONS: Once-daily applications of 0.1% tazarotene cream significantly reduced multiple signs of photodamage. Plasma levels of tazarotenic acid remained below those of endogenous retinoids.

Efeitos da loçäo de lactato de amônio a 12 por cento versus nenhum tratamento para a terapia da xerodermia plantar / The effects of ammonium lactate 12 per cents lotion versus no therapy in the treatment of dry skin of the heels

Sessenta indivíduos participaram de uma comparaçäo randomizada aberta, uni-cega (mascaramento do avaliador), bilateral e pareada. Alocou-se aleatoriamente uma formulaçäo de loçäo de lactato de amônio a 12 por cento ou nenhum tratameno à regiäo plantar direita ou esquerda. A loçäo foi aplicada duas vezes ao dia durante oito semanas no pé alocado, seguindo-se uma fase de regressäo de quatro semanas, na qual näo se aplicou o tratamento em nenhum dos pés. Os indivíduos apresentavam xerodermia plantar pelo menos moderada, igual em ambos os pés. Os que haviam aplicado medicaçöes com ou sem prescriçäo ou que haviam sido submetidos a debridamento mecânico nas duas semanas anteriores foram excluídos, bem como os que utilizaram retinóides orais no mês anterior ao início do estudo. A eficácia do tratamento näo pôde ser avaliada nos pacientes que utilizaram, durante o estudo, produtos tópicos nos pés que näo a medicaçäo pesquisada. Avaliou-se o efeito do lactato de amônio na pele da regiäo plantar, comparando-se sua eficácia à da ausência de tratamento através do "Overall Dryness Severity Score" (Escore de gravidade da xerodermia), "Physician Global Assessment of Improvement/Worsening" (avaliaçäo geral dos médicos de melhora/piora) e "Physician Preference" (preferência dos médicos). As avaliaçöes foram feitas na semana 0 (antes do tratamento) e nas semanas 1, 2, 4, 8, 10 e 12. O "escore de gravidade de xerodermia" foi avaliado em uma escala de 9 pontos, de 0 (pele normal, sem sinais de xerodermia) a 8 (xerodermia grave). A "avaliaçäo geral dos médicos de melhora/piora" foi feita em todas as consultas, exceto na inicial (Tabela 1). Em todas as consultas, com exceçäo da inicial, o pesquisador avaliou se havia alguma diferença entre os dois tipos de abordagem. Se houvesse diferença, o lado tratado era considerado:ligeiramente melhor, moderadamente melhor ou acentuadamente melhor. Também foram documentados os efeitos adversos e feitos "slides" dos locais avaliados nas semanas 0 (antes do tratamento), na semana 8 (final do tratamento) e 12 (final da regressäo)