Lithium chemistry of lithium doped magnesium oxide catalysts used in the oxidative coupling of methane

Active sites are created on the surface of a Li/MgO catalyst used for the selective oxidation of methane by the gradual loss of carbon dioxide from surface carbonate species in the presence of oxygen. Decomposition of the carbonate species in the absence of oxygen is detrimental to the activity of the catalyst. The active sites created are not stable but disappear either as a result of reaction with SiO2 to form Li2SiO3 or by the formation and subsequent loss of the volatile compound LiOH. In general the addition of water to the gas feed is detrimental to the stability of the catalyst. In the case of Li2CO3 strongly bonded on the surface of Li/MgO catalyst, the decomposition of the carbonate and thus the initial activity, can be enhanced by the addition of water to the gas feed. The addition of carbon dioxide to the gas feed results in a poisoning of the catalyst, the degree of this poisoning depending on the activity of the catalyst. The deactivation of the catalyst can be retarded if low concentration of carbon dioxide are added to the reaction mixture. It is possible to improve the stability of the catalyst by periodic reversal of the direction of flow of the gas steam

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On the design of an image compression scheme based upon a priori knowledge about imaging system and image statistics

This contribution is about the design of an image compression scheme for near loss-less image compression of a restricted class of images and a specific application. The images are digital diagnostic X-ray images of the coronary vessels of the human heart. This paper proposes a novel compression scheme with a compression ratio of 8-10 with preservation of the diagnostic image quality. Central in our approach is the amount of information a trained and highly skilled observer i.e. the cardiologist is able discern at a given exposure and thus quantum noise level. The physics of the image detection process together with the a priori knowledge of the imaging system are the basis of the image statistics. Relevant elements of the human visual system complete the stochastic characterization of imaging process whereon the compression scheme is based. 1

Objective Acoustic-Phonetic Speech Analysis in Patients Treated for Oral or Oropharyngeal Cancer

Objective: Speech impairment often occurs in patients after treatment for head and neck cancer. New treatment modalities such as surgical reconstruction or (chemo) radiation techniques aim at sparing anatomical structures that are correlated with speech and swallowing. In randomized trials investigating efficacy of various treatment modalities or speech rehabilitation, objective speech analysis techniques may add to improve speech outcome assessment. The goal of the present study is to investigate the role of objective acoustic-phonetic analyses in a multidimensional speech assessment protocol. Patients and Methods: Speech recordings of 51 patients (6 months after reconstructive surgery and postoperative radiotherapy for oral or oropharyngeal cancer) and of 18 control speakers were subjectively evaluated regarding intelligibility, nasal resonance, articulation, and patient-reported speech outcome (speech subscale of the European Organization for Research and Treatment of Cancer Quality of Life Questionnaire-Head and Neck 35 module). Acoustic-phonetic analyses were performed to calculate formant values of the vowels /a, i, u/, vowel space, air pressure release of /k/ and spectral slope of /x/. Results: Intelligibility, articulation, and nasal resonance were best predicted by vowel space and /k/. Within patients, /k/ and /x/ differentiated tumor site and stage. Various objective speech parameters were related to speech problems as reported by patients. Conclusion: Objective acoustic-phonetic analysis of speech of patients is feasible and contributes to further development of a speech assessment protocol. Copyright (C) 2009 S. Karger AG, Base

A new in vivo screening model for posterior spinal bone formation: comparison of ten calcium phosphate ceramic material treatments

This study presents a new screening model for evaluating the influence of multiple conditions on the initial process of bone formation in the posterior lumbar spine of a large animal. This model uses cages designed for placement on the decorticated transverse process of the goat lumbar spine. Five conduction channels per cage, each be defined by a different material treatment, are open to both the underlying bone and overlying soft tissue. The model was validated in ten adult Dutch milk goats, with each animal implanted with two cages containing a total of ten calcium phosphate material treatments according to a randomized complete block design. The ten calcium phosphate ceramic materials were created through a combination of material chemistry (BCP, TCP, HA), sintering temperature (low, medium, high), calcination and surface roughness treatments. To monitor the bone formation over time, fluorochrome markers were administered at 3, 5 and 7 weeks and the animals were sacrificed at 9 weeks after implantation. Bone formation in the conduction channels was investigated by histology and histomorphometry of non-decalcified sections using traditional light and epifluorescent microscopy. According to both observed and measured bone formation parameters, materials were ranked in order of increasing magnitude as follows: low sintering temperature BCP (rough and smooth)≈medium sintering temperature BCP≈TCP>calcined low sintering temperature HA>non-calcined low sintering temperature HA>high sintering temperature BCP (rough and smooth)>high sintering temperature HA (calcined and non-calcined). These results agree closely with those obtained in previous studies of osteoconduction and bioactivity of ceramics thereby validating the screening model presented in this study

Treatment with subcutaneous and transdermal fentanyl: Results from a population pharmacokinetic study in cancer patients

Purpose: Transdermal fentanyl is effective for the treatment of moderate to severe cancer-related pain but is unsuitable for fast titration. In this setting, continuous subcutaneous fentanyl may be used. As data on the pharmacokinetics of continuous subcutaneous fentanyl are lacking, we studied the pharmacokinetics of subcutaneous and transdermal fentanyl. Furthermore, we evaluated rotations from the subcutaneous to the transdermal route. Methods: Fifty-two patients treated with subcutaneous and/or transdermal fentanyl for moderate to severe cancer-related pain participated. A population pharmacokinetic model was developed and evaluated using non-linear mixed-effects modelling. For rotations from subcutaneous to transdermal fentanyl, a 1:1 dose conversion ratio was used while the subcutaneous infusion was continued for 12 h (with a 50 % tapering after 6 h). A 6-h scheme with 50 % tapering after 3 h was simulated using the final model. Results: A one-compartment model with first-order elimination and separate first-order absorption processes for each route adequately described the data. The estimated apparent clearance of fentanyl was 49.6 L/h; the absorption rate constant for subcutaneous and transdermal fentanyl was 0.0358 and 0.0135 h-1, respectively. Moderate to large inter-individual and inter-occasion variability was found. Around rotation from subcutaneous to transdermal fentanyl, measured and simulated plasma fentanyl concentrations rose and increasing side effects were observed. Conclusions: We describe the pharmacokinetics of subcutaneous and transdermal fentanyl in one patient cohort and report several findings that are relevant for clinical practice. Further research is warranted to study the optimal scheme for rotations from the subcutaneous to the transdermal route

A Prospective Population Pharmacokinetic Study on Morphine Metabolism in Cancer Patients

Background: Oral and subcutaneous morphine is widely used for the treatment of cancer-related pain; however, solid pharmacokinetic data on this practice are lacking. Furthermore, it is largely unknown which factors contribute to the variability in clearances of morphine and its metabolites and whether morphine clearance is related to treatment outcome. Methods: Blood samples from 49 cancer patients treated with oral and/or subcutaneous morphine were prospectively collected and were used to develop a population pharmacokinetic model for morphine, morphine-3-glucuronide (M3G) and morphine-6-glucuronide (M6G). The influence of age, gender, renal function and several polymorphisms possibly related to the pharmacokinetics of the three compounds was investigated. In addition, the relation between treatment failure and morphine and metabolite clearances was explored. Results: A one-compartment model including an extensive first-pass effect adequately described the data of morphine and its metabolites. Estimated mean area under the plasma concentration–time curve (AUC) ratios following oral versus subcutaneous administration were: M3G/morphine 29.7:1 vs. 11.1:1; M6G/morphine 5.26:1 vs. 1.95:1; and M3G/M6G 5.65:1 vs. 5.70:1. Renal function was significantly correlated with clearance of the metabolites, which increased 0.602 L/h per every 10 mL/min/1.73 m2 increase of estimated glomerular filtr

A double blind, fixed blood-level study comparing mirtazapine with imipramine in depressed in-patients

Antidepressant effects of mirtazapine and imipramine were compared in a randomized, double blind, fixed blood-level study with in-patients in a single centre. Patients with a DSM-III-R diagnosis of major depression and a Hamilton (17-item) score of ≤ 18 were selected. After a drug-free and a placebo-washout period of 7 days in total, 107 patients still fulfilling the HRSD criterion of ≤ 18, started on active treatment. The dose was adjusted to a predefined fixed blood level to avoid suboptimal dosing of imipramine. Concomitant psychotropic medication was administered only in a few cases because of intolerable anxiety or intolerable psychotic symptoms. Eight patients dropped out and two were excluded from analyses because of non-compliance; 97 completed the study. According to the main response criterion (50% or more reduction on the HRSD score) 11/51 (21.6%) patients responded on mirtazapine and 23/46 (50%) on imipramine after 4 weeks' treatment on the predefined blood level. Such a dramatic difference in efficacy between antidepressants has not often been reported before. The selection of (severely ill) in-patients, including those with suicidal or psychotic features, may have significance in this respect. Optimization of treatment with the reference drug imipramine through blood level control, exclusion of non-compliance for both drugs, exclusion of most concomitant medication and a low drop-out rate may also have contributed. It is concluded that imipramine is superior to mirtazapine in the patient population studied