Reduction of low temperature engine pollutants by understanding the exhaust species interactions in a diesel oxidation catalyst.

The interactions between exhaust gas species and their effect (promotion or inhibition) on the light-off and activity of a diesel oxidation catalyst (DOC) for the removal of pollutants are studied, using actual engine exhaust gases from the combustion of diesel, alternative fuels (rapeseed methyl ester and gas-to-liquid fuel) and diesel/propane dual fuel combustion. The activity of the catalyst was recorded during a heating temperature ramp where carbon monoxide (CO) and hydrocarbon (HC) light-off curves were obtained. From the catalyst activity tests, it was found that the presence of species including CO, medium-heavy HC, alkenes, alkanes, and NOx and their concentration influence the catalyst ability to reduce CO and total HC emissions before release to the atmosphere. CO could inhibit itself and other species oxidation (e.g., light and medium-heavy hydrocarbons) while suffering from competitive adsorption with NO. Hydrocarbon species were also found to inhibit their own oxidation as well as CO through adsorption competition. On the other hand, NO2 was found to promote low temperature HC oxidation through its partial reduction, forming NO. The understanding of these exhaust species interactions within the DOC could aid the design of an efficient aftertreatment system for the removal of diesel exhaust pollutants.

Finding synergies in fuels properties for the design of renewable fuels--hydroxylated biodiesel effects on butanol-diesel blends.

This article describes the effects of hydroxylated biodiesel (castor oil methyl ester - COME) on the properties, combustion, and emissions of butanol-diesel blends used within compression ignition engines. The study was conducted to investigate the influence of COME as a means of increasing the butanol concentration in a stable butanol-diesel blend. Tests were compared with baseline experiments using rapeseed methyl esters (RME). A clear benefit in terms of the trade-off between NOX and soot emissions with respect to ULSD and biodiesel-diesel blends with the same oxygen content was obtained from the combination of biodiesel and butanol, while there was no penalty in regulated gaseous carbonaceous emissions. From the comparison between the biodiesel fuels used in this work, COME improved some of the properties (for example lubricity, density and viscosity) of butanol-diesel blends with respect to RME. The existence of hydroxyl group in COME also reduced further soot emissions and decreased soot activation energy.

Controlling soot formation with filtered EGR for diesel and biodiesel fuelled engines.

Although exhaust gas recirculation (EGR) is an effective strategy for controlling the levels of nitrogen oxides (NO(X)) emitted from a diesel engine, the full potential of EGR in NO(X)/PM trade-off and engine performance (i.e., fuel economy) has not fully been exploited. Significant work into the cause and control of particulate matter (PM) has been made over the past decade with new cleaner fuels and after-treatment devices emerging to comply with the current and forthcoming emission regulations. In earlier work, we demonstrated that engine operation with oxygenated fuels (e.g., biodiesel) reduces the PM emissions and extends the engine tolerance to EGR before it reaches smoke-limited conditions. The same result has also been reported when high cetane number fuels such as gas-to-liquid (GTL) are used. To further our understanding of the relationship between EGR and PM formation, a diesel particulate filter (DPF) was integrated into the EGR loop to filter the recirculated soot particulates. The control of the soot recirculation penalty through filtered EGR (FEGR) resulted in a 50% engine-out soot reduction, thus showing the possibility of extending the maximum EGR limit or being able to run at the same level of EGR with an improved NO(X)/soot trade-off.

Unusual complication of a pancreatic neuroendocrine tumor presenting with malignant hypercalcemia.

CONTEXT: Hypersecretion of PTHrP is a relatively common cause of malignancy-related hypercalcemia but has only been described in a few cases of neuroendocrine tumors (NET). OBJECTIVE: The aim of this case report is to describe the clinical syndrome, complex therapeutic interventions, and unusual complications caused by persistent PTHrP hypersecretion in a patient with a pancreatic NET. CASE ILLUSTRATION: A 58-yr-old male patient presented with nonspecific abdominal pain and was found to have severe hypercalcemia secondary to a well-differentiated NET of the pancreas associated with extensive liver metastases. Elevated ionized calcium levels accompanied by low serum PTH and remarkably elevated PTHrP concentrations were consistent with PTHrP-related hypercalcemia that proved to be resistant to various chemotherapeutic regimens and supportive therapy. Partial control of the humoral syndrome was obtained only after the application of cytoreductive interventions and the introduction of various molecular targeted therapies. Due to persistent PTHrP action, bone disease emerged in the form of brown tumors. DISCUSSION: The manifestation of paraneoplastic syndrome due to PTHrP hypersecretion, despite its rareness in NET, should be considered in the differential diagnosis of hypercalcemia in such tumors. Moreover, the appearance of bone lesions in this setting may be in the context of metabolic bone disease and could be misdiagnosed as bone metastases.

Cortical bone response adjacent to applied light orthodontic forces in ovariectomized rats.

Cortical bone response to experimental orthodontic forces has not been adequately described in the available literature. The aim of this study was to investigate the application of light orthodontic forces on the cortical bone adjacent to the point of their application, in normal and ovariectomized rats. At the age of eight months, twenty-four female rats were divided equally into two groups: normal (group A) and ovariectomized (group B). A 20 gr* orthodontic force was applied to the maxillary right first molars in all animals for 14 days. Histological examination of the maxillary cortical bone, at the level of the first molar of the upper jaw, was performed on both sides of all animals. It was found that light orthodontic forces applied to the upper right first molars of normal rats result in thinner cortical bone with increased osteoblastic activity, normal lamellar orientation and normal distribution of osteocytes compared to the non-affected contralateral side. In ovariectomized rats it was found that light orthodontic forces applied to the upper right first molars result in thickening of the cortex, in comparison to the respective area of the opposite side where no orthodontic forces were applied. It seems that experimental light orthodontic forces, in rats, affect cortical bone remodeling differently, according to their hormonal status, in areas adjacent to the applied forces.

Subclinical hyperthyroidism in dementia and correlation of the metabolic index in FDG-PET.

AIM: Thyroid hormone status and thyroid antibodies were evaluated in patients suffering from dementia for further study of an association of hyperthyroidism with AD and vascular dementia (VD), respectively. PATIENTS: In 77 patients with dementia, and 42 controls, thyrotropin (TSH) and thyroid antibodies were correlated with the different types of dementia and the metabolic index (MI) based on imaging with F-18-2-fluoro-2-deoxy-D-glucose positron emission tomography (FDG-PET). RESULTS: Twenty-two of all patients with dementia (29%) had borderline (TSH 0.3-0.5 mU/l) or decreased TSH levels (TSH < 0.3 mU/L). TSH values were significantly lower in patients suffering from AD (median: 1.1 mU/l) and VD (0.5 mU/l) than in the control group (1.5 mU/l) (p < 0.01). Decreased or borderline TSH levels were present in 52% of the patients with VD, but in only 10% of the controls, and in 23% of the patients with AD. Antibodies to thyroid peroxidase were positive in 16% of all patients with dementia. The MI in patients suffering from AD with borderline TSH levels was 0.81 (0.70, 0.94). In contrast, patients suffering from AD with normal TSH values showed a slightly higher MI of 0.84 (0.76, 0.89) (p = n.s.). CONCLUSION: Decreased or borderline TSH values are associated with an increased probability of having dementia, especially VD.

Effects of experimental unilateral condylectomy followed by altered mandibular function on the maxilla and zygoma.

The effect of protruded mandibular function on the maxilla and zygoma was studied in young unilaterally condylectomized growing rats. Forty-eight-4-week-old rats were divided into two experimental and two control groups as follows: group A, 12 animals unilaterally condylectomized on the right side; the mandible was allowed to function normally; group B, 12 animals unilaterally condylectomized on the right side; the mandible was protracted forwards immediately by means of an appliance; group C, 12 animals sham-operated on the right side; no condylectomy or mandibular protraction; and group d, 12 control animals not subjected to any operation or mandibular protraction. The mandibular protraction was achieved by an appliance consisting of an acrylic collar brace fitted to the animal's neck and supporting rubber bands pulling on an intraoral part cemented on the animal's lower incisors. Twenty-five grams of pulling force and protrusion to a clinically and radiographically testes anterior crossbite was exercised for 12 hours per day. The experimental period was 30 days. Lateral and dorsoventral radiographs were taken on days 1 and 30 following condylectomies and mandibular protraction. Cephalometric analysis was performed for each animal with measurements evaluating the maxilla and zygoma. Statistical analysis and comparison of the findings in the four groups of animals can be summarized as follows: (i) condylectomy and altered mandibular function may produce remote skeletal reactions in other parts of the cranial complex; and (ii) the ipsilateral maxilla is affected by condylectomy of the mandible, but altered mandibular function by protraction compensates for the results of condylectomy.

Altered mandibular function and prevention of skeletal asymmetries after unilateral condylectomy in rats.

Unilateral condylar injury is known to be a frequent cause of mandibular asymmetry. Whether this is due to the trauma itself or to the disturbed function that follows the injury is a very important question with ramifications for clinical complications related to facial asymmetries. The aim of this study was to test the hypothesis that mandibular function in a protruded position can compensate for the absence of one condyle and prevent potential growth asymmetries. Forty-eight 4-week-old rats were divided into two experimental and two control groups consisting of 12 animals each, as follows: (A) unilateral condylectomy was performed on the right side and the mandible was left to function normally; (B) after unilateral condylectomy on the right side, the mandible was forced to function in a protruded position; (C) a sham operation was performed in the condylar area of the right side but no appliance was used; and (D) 12 animals were used as controls without any operation or appliance. Mandibular protraction was achieved by means of a specific appliance, acting via rubber bands, pulling the mandible in a straight, forward direction with a force of 25 g for 12 hours per day. The experimental period was 30 days. Dorsoventral radiographs were taken and vital dyes were administered at three time intervals, i.e. on days 1, 15 and 30, for all animals. Cephalometric analysis included 14 measurements. Findings resulting from statistical analysis and comparisons of measurements obtained in the four groups can be summarized as follows: (i) when comparing group A with groups C and D, less growth was found in the right mandibular sides in group A; (ii) when comparing group B and groups C and D, less growth was found in the right mandibular sides in group B; (iii) when comparing groups A and B, more growth was found in the right mandibular sides in group B; (iv) when comparing the right and left mandibular sides in group A, less growth was found in the right side; and (v) when comparing the right and left mandibular sides in group B, no significant growth differences were found. These findings support the hypothesis that altered mandibular function in a protruded position can compensate for the effects of unilateral condylectomy and prevent the appearance of skeletal mandibular asymmetries in growing rats.

An appliance designed for experimental mandibular hyperpropulsion in rats.

Many animal experiments dealing with function-form interaction and mandibular condylar growth have utilized hyperpropulsion of the animal's mandible. Numerous hyperpropulsive appliances have been described in the literature. However, there are significant discrepancies between reported results which are most likely due to the use of appliances that do not secure true mandibular hyperpropulsion. The specific rat craniofacial anatomy as well as the masticatory physiology of this animal requires the design of a specific appliance that would meet the species' functional characteristics. The aim of this paper is to describe a new type of appliance that can produce a controlled, stable and reproducible anterior displacement of the mandible in rats. After reviewing and evaluating the appliances used by other researchers, a totally new appliance for experimental mandibular hyperpropulsion in rats is presented. Its advantages are: (i) it produces a secure, measurable and reproducible anterior displacement of the mandible; (ii) it does not permit any retrusive or lateral mandibular movements. Avoidance of this variable can increase reliability of results and minimize involvement of other confusing parameters; and (iii) it allows the animals to be fed sufficiently for a number of hours every day. The appliance consists of an acrylic collar brace fitted to the animal's neck and carrying wire extensions that support rubber bands pulling on a band cemented to the animal's lower incisors. The pulling force depends on the thickness of the applied elastics.

Effects of altered mandibular function on mandibular growth after condylectomy.

The purpose of this study was to investigate the effect of protruded mandibular function on bilaterally condylectomized mandibles of growing rats. Sixty 4-week-old rats were divided into three experimental and two control groups each consisting of 12 animals as follows: (A) bilateral condylectomy was performed and the mandible was left to function normally; (B) the mandible was protracted forward without any condylectomy; (C) after bilateral condylectomy, the mandible was forced to function in a protruded position; (D) the animals were used as controls without any operation or appliance; and (E) a sham operation was performed in the condylar area but no appliance was used. Mandibular protraction was achieved by means of a specific appliance acting via rubber bands pulling the mandible in a straight, forward direction with a force of 25 g for 12 hours/day. The experimental period was 30 days. Lateral and dorsoventral radiographs were taken and vital dyes were administered on days 1 and 30 for all animals. Cephalometric analysis included 10 measurements. Findings resulting from statistical analysis of measurements in the five groups are summarized as follows: (i) between group A and groups D and E, less growth was found in group A; (ii) between group B and groups D and E, more growth was found in group B; (iii) between group A and group B, more growth was found in group B; (iv) between group A and group C, more growth was found in group C; and (v) between group B and group C, more growth was found in group B. These findings support the conclusion that although mandibular propulsion enhances growth even after condylectomy, the condyle seems to be an essential element for normal growth and development.