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Permanent Changes (permanent + change)
Selected AbstractsElectrochemical Impedance Characterization of Nafion-Coated Carbon Film Resistor Electrodes for ElectroanalysisELECTROANALYSIS, Issue 7 2005Carla Gouveia-Caridade Abstract Carbon film disk electrodes with Nafion coatings have been characterized by electrochemical impedance spectroscopy (EIS) with a view to a better understanding of their advantages and limitations in electroanalysis, particularly in anodic stripping voltammetry of metal ions. After initial examination by cyclic voltammetry, spectra were recorded over the full potential range in acetate buffer solution at the bare electrodes, electrodes electrochemically pretreated in acid solution, and Nafion-coated pretreated electrodes in the presence and absence of dissolved oxygen. EIS equivalent circuit analysis clearly demonstrated the changes between these electrode assemblies. In order to simulate anodic stripping voltammetry conditions, spectra were also obtained in the presence of cadmium and lead ions in solution at Nafion-coated electrodes, both after metal ion deposition and following re-oxidation. Permanent changes to the structure of the Nafion film occurred, which has implications for use of these electrode assemblies in anodic stripping voltammetry at relatively high trace metal ion concentrations. [source] Dynamic coating of SU-8 microfluidic chips with phospholipid disksELECTROPHORESIS, Issue 15 2010Tiina Sikanen Abstract In this work, PEG-stabilized phosphatidylcholine lipid aggregates (disks), mimicking mammalian cell membranes, were introduced as a new biofouling resistant coating for SU-8 polymer microchannels. A rapid and simple method was developed for immobilization of PEGylated phosphatidylcholine disks in microchannels. Microfluidic chips made from SU-8, PDMS, or glass were dynamically coated with the PEGylated disks followed by characterization of their surface chemistry before and after coating. On the basis of the observed changes in EOF and nonspecific protein adsorption, the affinity of the PEGylated disks was shown to be particularly strong toward SU-8. The PEG-lipid coating enabled permanent change in EOF in SU-8 microchannels with an initial value of 4.5×10,8,m2,V,1,s,1, decreasing to 2.1×10,8,m2,V,1,s,1 (immediately after modification), and, eventually, to 1.5×10,8,m2,V,1,s,1 (7 days after modification) for 9,mM sodium borate (pH 10.5) as BGE. As determined by the Wilhelmy plate measurements and microchip-CE analysis of BSA, the PEG-lipid coating also enabled efficient biofouling shield against protein adsorption, similar to that of low amounts of SDS (3.5,mM) or Tween-20 (80,,M) as buffer additives. These results suggest that dynamically attached PEG-lipid aggregates provide stable, biomimicking surface modification that efficiently reduces biofouling on SU-8. [source] Structural Changes in Silica Glass by Continuous-Wave Laser Backside IrradiationJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 6 2010Hirofumi Hidai We report on a permanent change in the physical properties inside silica glass by rapid heating and quenching using a continuous-wave laser beam. The absorption of the glass was enhanced by laser heating, and the heated spot moved as a result of thermal radiation and conduction. To trigger heating, an absorbent material was placed on the backside of a glass plate and irradiated through the glass. Laser illumination with a power of 11 W focused on the absorbent material induced a cylindrical modified zone along the laser beam with a length of up to 5.5 mm that was modified at a rate of ,130 mm/s. The characteristics of the modified silica glass were studied. The modified area consists of two layers, and the diameters of the inner and outer zones are ,40 and ,55 ,m, respectively. The inner zone was modified by laser heating. The fictive temperature is estimated to be ,1900 K. The etch rate and hardness of the modified glass increased owing to the increment of the fictive temperature. The outer zone was modified by tensile stress due to the densification of the inner zone. In the outer zone, the etch rate is increased and hardness is decreased. [source] Xerostomia: 12-Month changes in saliva production and its relationship to perception and performance of swallow function, oral intake, and diet after chemoradiationHEAD & NECK: JOURNAL FOR THE SCIENCES & SPECIALTIES OF THE HEAD AND NECK, Issue 6 2003Jeri A. Logemann PhD Abstract Background. Previous investigators have found permanent changes in saliva production after chemoradiation but have not examined these in relation to swallowing measures, diet changes, and patient comfort over time. Methods. Thirty patients with advanced stage cancer of the oropharynx treated with chemoradiation were followed with videofluoroscopic swallow studies, a measure of stimulated total saliva production, a questionnaire of their perception of dry mouth, and a questionnaire on the nature of their oral intake at pretreatment until 12 months after treatment. Results. Saliva declined significantly from pretreatment to 12 months. Swallowing-related complaints increased significantly over the 12 months, especially in patients with lower saliva weights. Diet choices increased over time after treatment, except crunchy foods. Swallow measures did not relate to saliva weight. Conclusions. Reduced saliva weight does not correlate with slowed or inefficient swallow. Instead, reduced saliva weight seems to change patients' perceptions of their swallowing ability and, on that basis, their diet choices. © 2003 Wiley Periodicals, Inc. Head Neck 25: 432,437, 2003 [source] Steroid-induced sexual differentiation of the developing brain: multiple pathways, one goalJOURNAL OF NEUROCHEMISTRY, Issue 5 2008Jaclyn M. Schwarz Abstract Hormone exposure, including testosterone and its metabolite estradiol, induces a myriad of effects during a critical period of brain development that are necessary for brain sexual differentiation. Nuclear volume, neuronal morphology, and astrocyte complexity are examples of the wide range of effects by which testosterone and estradiol can induce permanent changes in the function of neurons for the purpose of reproduction in adulthood. This review will examine the multitude of mechanisms by which steroid hormones induce these permanent changes in brain structure and function. Elucidating how steroids alter brain development sheds light on how individual variation in neuronal phenotype is established during a critical period. [source] Altered Mesencephalic Dopaminergic Populations in Adulthood as a Consequence of Brief Perinatal Glucocorticoid ExposureJOURNAL OF NEUROENDOCRINOLOGY, Issue 8 2005S. McArthur Abstract Early exposure to stressors is strongly associated with enduring effects on central nervous system function, but the mechanisms and neural substrates involved in this biological ,programming' are unclear. This study tested the hypothesis that inappropriate exposure to glucocorticoid stress hormones (GCs) during critical periods of development permanently alters the mesencephalic dopaminergic populations in the ventral tegmental area (VTA) and substantia nigra pars compacta (SNc). Using a rat model, the synthetic GC dexamethasone was added to the maternal drinking water during gestational days 16,19 or over the first week of postnatal life. In adulthood, the effects upon tyrosine hydroxylase immunopositive (TH+) cell numbers in the midbrain, and monoamine levels in the forebrain, of the adult offspring were assessed and compared with control offspring whose dams received normal drinking water. In the VTA, both prenatal and postnatal dexamethasone treatment increased TH+ cell numbers by approximately 50% in males and females. Although prenatal dexamethasone treatment also increased TH+ cell numbers in the SNc by 40,50% in males and females, postnatal treatment affected females only by increasing TH+ cell numbers by approximately 30%. In comparison, similar changes were not detected in the monoamine levels of the dorsolateral striatum, nucleus accumbens or infralimbic cortex of either males or females, which is a feature likely to reflect adaptive changes in these pathways. These studies demonstrate that the survival or phenotypic expression of VTA and SNc dopaminergic neurones is profoundly influenced by brief perinatal exposure to GCs at times when endogenous levels are normally low. These findings are the first to demonstrate permanent changes in the cytoarchitecture within midbrain dopamine nuclei after perinatal exposure to stress hormones and implicate altered functionality. Thus, they have significance for the increasing use of GCs in perinatal medicine and indicate potential mechanisms whereby perinatal distress may predispose to the development of a range of psychiatric conditions in later life. [source] Fetal programming: link between early nutrition, DNA methylation, and complex diseasesNUTRITION REVIEWS, Issue 2 2010Agata Chmurzynska Complex traits, including those involved in diet-related diseases, are determined by multiple genes and environmental influences. Factors influencing the development of complex traits should be expanded to include epigenetic factors, such as DNA methylation, which occurs in utero. Epigenetic factors regulate gene expression and thereby cell differentiation and organogenesis. The process of epigenotype establishment is sensitive to environmental conditions, with nutrition being one of the most important related factors. For example, DNA methylation depends on the availability of several nutrients including methionine and vitamins B6, B12, and folate. Epidemiological studies show that undernutrition during fetal life is associated with increased susceptibility to complex diseases. Numerous studies have been conducted on prenatal caloric and protein undernutrition. A reduction in the number of cells and changes in the structure and functioning of organs, as well as permanent changes in DNA methylation and gene expression, have been considered the molecular mechanisms responsible for metabolism programming. [source] Induced leukemia and antineoplastic agent carmustine cause permanent changes in craniofacial growth of immature ratsORTHODONTICS & CRANIOFACIAL RESEARCH, Issue 3 2002S Karsila-Tenovuo Structured Abstract Authors , Karsila-Tenovuo S, Jahnukainen K, Peltomäki T, Salmi TT, Rönning O Objectives , The purpose of the present study was to investigate the possible effects of untreated terminal leukemia on craniofacial growth (Study I), and also the effects of the antineoplastic agent carmustine on craniofacial growth in both leukemic and healthy rats (Study II). Material , A total of 367 inbred Piebald variegated rats was used. Method , Transmission of leukemic cells was carried out intraperitoneally at 30 days of age, and without treatment (Study I), the rats reached the terminal phase within 17 ± 1 days. Rats with induced leukemia was cured with 10 mg/kg carmustine (BCNU) given on days 6 and 13 following cell transmission (Study II), the rats remaining in remission until they were killed at 100 days of age. Final weight was recorded and 12 craniofacial dimensions and tibial length were measured with a digital sliding caliper. Results , The results showed that the effect of untreated terminal rat leukemia (Study I) on craniofacial growth differed between the genders. Male rats showed clearly reduced dimensions of facial structures and also retarded general body growth, whereas females showed differences mainly in general body growth. The effect of cured leukemia (Study II) as such was minor, while BCNU had a strong and permanent reducing effect on both craniofacial and general body growth in both genders. Conclusion , We suggest that the results in Study I came both from a direct effect of leukemia and an indirect effect of untreated terminal leukemia through malnutrition. The alkylating agent BCNU seemed to be the main cause of permanent craniofacial and general growth retardation in Study II. [source] Implementing the lead user method in a high technology firm: A longitudinal study of intentions versus actionsTHE JOURNAL OF PRODUCT INNOVATION MANAGEMENT, Issue 6 2001Erik L. Olson The customer or user's role in the new product development process is limited or nonexistent in many high technology firms, despite evidence that suggests customers are frequently an excellent source for new product ideas with great market potential. This article examines the implementation of the Lead User method for gathering new product ideas from leading edge customers by an IT firm that had not previously done much customer research during their new product development efforts. This case study follows the decision-makers of the firm through the process, where the end result is the generation of a number of useful product concepts. Besides the ideas generated, management at the firm is also impressed with the way the method makes their new product development process more cross-functional and they plan to make it a part of their future new product development practices. Approximately one year later the firm is revisited to find out if the Lead User method has become a permanent part of their new product development process. The authors find, however, that the firm has abandoned research on the customer despite the fact that several of the lead-user derived product concepts had been successfully implemented. Management explanations for their return to a technology push process for developing new products include personnel turnover and lack of time. Using organizational learning theory to examine the case, the authors suggest that the nontechnology specific product concepts generated by the lead users were seen as ambiguous and hence overly simplistic and less valuable by the new product development personnel. The technical language spoken by the new product personnel also increased the inertia of old technology push development process by making it more prestigious and comfortable to plan new products with their technology suppliers. The fact that the firm was doing well throughout this process also decreased the pressure to change from their established new product development routine. The implications for these finding are that: 1) it is necessary to pressure or reward personnel in order to make permanent changes to established routines, and 2) researchers should be careful at taking managers at their word when asking them about their future intentions. [source] | |||||||||||||