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Experimental Variables (experimental + variable)
Selected AbstractsEffect of chlorhexidine mouth rinse on Streptococci counts of tooth-tissue-borne palatal expander biofilmORTHODONTICS & CRANIOFACIAL RESEARCH, Issue 3 2008IT Maruo Structured Abstract Authors,,, Maruo IT, Rosa EAR, Maruo H, Tanaka O, Guariza Filho O, Ignácio SA, Camargo ES Objectives,,, To assess total Streptococci (TS) counts and biofilm mass over tooth-tissue-borne palatal expander (TTBPE), as well as the effect of chlorhexidine (CHX) mouth rinse on these variables. Design,,, A cross-sectional study design employed clinical procedures and laboratorial techniques. Setting and Sample Population,,, Patients who had TTBPE removal indicated were divided into two groups: a CHX group (n = 26) in which three times a day of 0.2% CHX digluconate mouth rinses were prescribed 7 days before TTBPE removal; and a control (CON) group (n = 25) in which no antimicrobial treatment was applied. Experimental Variable,,, ,Gender', ,Age', and ,TTBPE wear time' were recorded. After TTBPE removal, biofilm mass was determined by the difference between (TTBPE + biofilm) and (TTBPE only) masses. TS counts were determined by biofilm suspension followed by progressive dilutions and culture on Mitis Salivarius agar with incubation at 37°C for 72 h. Outcome Measure,,, Biofilm mass (mg) and Colony Forming Units of TS,/,mg of biofilm (CFU-TS,/,mg) were calculated. Results,,, Total Streptococci mean values in CHX (6.77 × 106CFU-TS,/,mg) were statistically lower (p < 0.01) than those in CON (3.82 × 107CFU-TS,/,mg), but there was no statistical difference (p > 0.05) between CHX (168.88 mg) and CON (182.04 mg) masses nor statistical correlation (p > 0.05) between biofilm mass and CFU-TS,/,mg in the two groups. Conclusion,,, Chlorhexidine reduces the TS counts in TTBPE, but has no effect on biofilm mass. [source] Design and assessment of a tissue-engineered model of human phalanges and a small jointORTHODONTICS & CRANIOFACIAL RESEARCH, Issue 4 2005WJ Landis Structured Abstract Authors ,, Landis WJ, Jacquet R, Hillyer J, Lowder E, Yanke A, Siperko L, Asamura S, Kusuhara H, Enjo M, Chubinskaya S, Potter K, Isogai N. Objectives ,, To develop models of human phalanges and small joints by suturing different cell-polymer constructs that are then implanted in athymic (nude) mice. Design ,, Models consisted of bovine periosteum, cartilage, and/or tendon cells seeded onto biodegradable polymer scaffolds of either polyglycolic acid (PGA) or copolymers of PGA and poly-L-lactic acid (PLLA) or poly- , -caprolactone (PCL) and PLLA. Constructs were fabricated to produce a distal phalanx, middle phalanx, or distal interphalangeal joint. Setting and Sample Population ,, Studies of more than 250 harvested implants were conducted at the Northeastern Ohio Universities College of Medicine. Experimental Variable ,, Polymer scaffold, cell type, and implantation time were examined. Outcome Measure ,, Tissue-engineered specimens were characterized by histology, transmission electron microscopy, in situ hybridization, laser capture microdissection and qualitative and quantitative polymerase chain reaction analysis, magnetic resonance microscopy, and X-ray microtomography. Results ,, Over periods to 60 weeks of implantation, constructs developed through vascularity from host mice; formed new cartilage, bone, and/or tendon; expressed characteristic genes of bovine origin, including type I, II and X collagen, osteopontin, aggrecan, biglycan, and bone sialoprotein; secreted corresponding proteins; responded to applied mechanical stimuli; and maintained shapes of human phalanges with small joints. Conclusion ,, Results give insight into construct processes of tissue regeneration and development and suggest more complete tissue-engineered cartilage, bone, and tendon models. These should have significant future scientific and clinical applications in medicine, including their use in plastic surgery, orthopaedics, craniofacial reconstruction, and teratology. [source] Tissue reaction to orthodontic tooth movement in different bone turnover conditionsORTHODONTICS & CRANIOFACIAL RESEARCH, Issue 3 2003C. Verna Structured Abstract Authors , Verna C, Melsen B Objectives , To study the tissue reaction to orthodontic load in normal, high, and low bone turnover states. Design , ,Split mouth' design performing orthodontic tooth movement in 52, 6-month-old male rats with: normal (n = 19), high (n = 16), and low bone turnover (n = 17), the latter two being obtained by induction of hyperthyroidism and hypothyroidism, respectively. Performed at the Department of Orthodontics at Aarhus University. Experimental Variable , The upper left first molar was moved for 21 days. Bone markers were administered 7 and 2 days before killing. Histological sections were cut at the coronal and apical levels. Outcome Measure , Alveolar socket area, periodontal ligament width, the relative extension of alveolar wall with erosion surfaces, and the mineralizing surfaces were measured and compared in the three groups. Results , Alveolar socket, periodontal ligament width, and erosion surface were larger on the treated than on the control side in the three groups. The normal and hypothyroid groups showed a wider periodontal ligament at the bucco-distal site at the coronal level, while the hyperthyroid group showed a widening which was not spatially oriented. The normal and hyperthyroid groups showed higher erosion at the corono-mesial site. The mineralizing surfaces were larger on the treated than on the control side in the normal and hypothyroid groups, but not in the hyperthyroid group. Conclusion , In the hyperthyroid group, the widening of the periodontal ligament was not spatially oriented and the increased erosion was not accompanied by increased formation, as observed in the normal and hypothyroid groups. [source] Upregulation of immunoreactivity of endothelin-1 and ,-SMA in PDL microvasculature following acute tooth loading: an immunohistochemical study in the marmosetORTHODONTICS & CRANIOFACIAL RESEARCH, Issue 2 2003MR Sims Structured Abstract Authors , Sims MR, Ashworth JF, Sampson WJ Objectives , To test the hypothesis that a continuous mechanical tooth load would elevate immunoreactivity of endothelin-1 (ET-1) and alpha-smooth muscle actin (,-SMA) in the periodontal ligament (PDL) microvasculature. Design , A randomized control study employing 1.5 h of loading to first molars. Setting and Sample Population , Orthodontic Research Laboratory, Dental School, Adelaide University. Four young adult, male marmoset monkeys were consecutively anaesthetized and treated. Experimental Variable , An external telescoping frame applied a jaw closing load (120,200 g) transmitted occlusally, via a rubber pad, to randomly assigned mandibular left or right first molars. Contralateral molars were used as controls. Outcome Measure , Undemineralized, midsagittal, mandibular molar slices, ,150 ,m thick were immunolabelled with ET-1 and ,-SMA antibodies and examined in a confocal laser scanning microscope (CLSM) for vascular endothelium and smooth muscle immunolabelling. Results , Three categories of post-capillary-sized venule endothelial cell immunolabelling occurred: endothelium labelled solely with ET-1; endothelium labelled solely with ,-SMA; endothelium labelled with both ET-1 and ,-SMA. In endothelial cells, the ,-SMA showed a moderate cytoplasmic distribution with dense peripheral concentration. Loading increased arteriole ,-SMA actin labelling. Conclusion , Scattered expression of ET-1 is the default state in primate PDL endothelial cells. Increased antigenicity of endothelial cells to both ET-1 and ,-SMA, and of arteriolar smooth muscle to ,-SMA, is a response to shear and compression loads. [source] The acceptability of variations in smile arc and buccal corridor spaceORTHODONTICS & CRANIOFACIAL RESEARCH, Issue 1 2007S Parekh Structured Abstract Authors ,, Parekh S, Fields HW, Beck FM, Rosenstiel SF Objectives ,, To evaluate the esthetic acceptability range of computer-generated variations in smile arc and buccal corridor. Design ,, Web-based descriptive study using available subjects. Setting and Sample Population ,, The World Wide Web. Subjects for the main study included 115 lay and 131 orthodontist raters. Experimental Variables ,, Buccal corridors and smile arcs, each presented for a female and a male image. Buccal corridors were presented as none, ideal and excessive. The smile arc was presented as flat, ideal and excessive. The nine male and female variations, as combinations of the above variables, were each presented twice to evaluate reliability. Outcome Measure ,, Acceptability of buccal corridors and smile arcs using the web-based instrument. An arbitrary super majority threshold of acceptability was set at 67% approval. Results ,, Both laypersons and orthodontists showed good reliability (k , 0.70). There was a broad range of acceptability, but laypersons and orthodontists showed no significant differences on the two variables tested. While orthodontists and laypersons both found smiles with excessive buccal corridors to be significantly less acceptable than those with ideal or absent buccal corridors, they were still acceptable over 70% of the time. Flat smile arcs were only acceptable 50,60% of the time, while smiles with ideal and excessive smile arcs were significantly more acceptable 84,95% of the time. When examining buccal corridors and smile arcs together, excessive buccal corridors were significantly less acceptable than ideal or absent buccal corridors regardless of the smile arc. A flat smile arc significantly reduced the acceptability of any buccal corridor to below the threshold of acceptability. Conclusions ,, Laypersons and orthodontists have similar preferences when acceptability of buccal corridors and smile arcs are considered. Flat smile arcs are more detrimental to smile esthetics than variations in buccal corridors. Clinicians must realize that although attractiveness may be reduced by variations in buccal corridors and smile arcs, the result may still be acceptable to a majority of people. [source] Analysis of facial growth in subjects with syndromic ectodermal dysplasia: a longitudinal analysisORTHODONTICS & CRANIOFACIAL RESEARCH, Issue 2 2002N Bondarets Structured Abstract Authors, Bondarets N, Jones RM, McDonald F. Objective, To examine the craniofacial growth pattern of patients diagnosed with syndromic ectodermal dysplasia. >Design, Mixed longitudinal analysis of lateral cephalograms. Setting, The data were analysed using a multilevel modelling technique with the MLwiN application software and the results presented numerically and graphically. Sample Population, All 61 subjects had severe hypodontia with the number of absent teeth (excluding third molars) ranging from 6 to 28 (mean=15.4). At presentation the subjects had a mean age of 133 months and were followed longitudinally for between one and five subsequent occasions (mean 2.66 occasions; mean age at completion of observation 207 months). Outcome Measures, Lateral cephalograms taken at each visit. Experimental Variables, Analysis of four angular measurements and four linear measurements, together with one calculated ratio. Results, Growth curves are presented showing the trends of craniofacial growth. Conclusions, The most significant findings were for a universal tendency for the individuals to undergo a change in sagittal relationship of the jaws, becoming markedly more Class III with time. We have also demonstrated a significant difference in growth between the anterior and posterior face heights indicating that the subjects have a tendency to an anterior growth rotation. [source] Effect of mandibular distraction osteogenesis on developing molarsORTHODONTICS & CRANIOFACIAL RESEARCH, Issue 4 2007M Kleine-Hakala Structured Abstract Authors,,, Kleine-Hakala M, Hukki J, Hurmerinta K Objective,,, To observe the effect of mandibular distraction osteogenesis (DO) on developing molars. Design,,, Descriptive clinical study. Setting,,, University hospital setting. Seventeen children (mean age 7.6 years) with various syndromes (hemifacial/craniofacial microsomia, Goldenhar syndrome, Treacher Collins syndrome, Nager syndrome and Pyle,Bakwin,Krida syndrome) participated. Experimental variable,,, Severely retrognathic lower jaws were distracted (mean 30 days) with an extraoral bicortically fixed DO device. Outcome measure,,, Consecutive panoramic tomograms were analysed after a mean follow-up period of 3.6 years, range 1,6.9 years. Results,,, The mandibular molars were affected by DO in 13 of the 17 patients which included 18 of 63 mandibular molars studied. Structural changes included root malformations, hindered tooth development and the destruction of tooth follicles. Positional changes such as shifted and tilted teeth were also found. Three injured teeth failed to erupt. These changes were because of splitting of the tooth follicle during the osteotomy (22%), piercing of the tooth follicle by the pin (39%) or migration of tooth germ towards the newly created bone (39%). Fifteen per cent of first molars, 43% of second molars and 31% of third molars were affected during the distraction process. Of all dental injuries, 44% were noticed while the appliance was in place. A further 17% of injuries were noted between 3 months and 1 year postoperatively and 33% during the second postoperative year. Conclusions,,, Although dental injuries are a minor disadvantage compared with the vast benefits offered by DO, focusing on these drawbacks might lead to re-consideration of the type of the device as well as the timing of DO. [source] Pulsed Amperometric Detection of Histamine at Glassy Carbon Electrodes Modified with Gold NanoparticlesELECTROANALYSIS, Issue 4 2005V. Carralero Abstract Gold nanocrystal-modified glassy carbon electrodes (nAu-GCE) were prepared and used for the determination of histamine by flow injection and high performance liquid chromatography using pulsed amperometric detection (PAD) as the detection mode. Experimental variables involved in the electrodeposition process of gold from a HAuCl4 solution were optimized. A catalytic enhancement of the histamine voltammetric response was observed at the nAu-GCE when compared with that obtained at a conventional Au disk electrode, as a consequence of the microdispersion of gold nanocrystals on the GC substrate. The morphological and electrochemical characteristics of the nAu-GCE were evaluated by SEM and cyclic voltammetry. PAD using a very simple potential waveform consisting of an anodic potential (+700,mV for 500,ms) and a cathodic potential (,300,mV for 30,ms), was used to avoid the electrode surface fouling when histamine was detected under flowing conditions. Flow injection amperometric responses showed much higher Ip values and signal-to-noise ratios at the nAu-GCE than at a conventional gold disk electrode. A limit of detection of 6×10,7,mol L,1 histamine was obtained. HPLC-PAD at the nAu-GCE was used for the determination of histamine in the presence of other biogenic amines and indole. Histamine was determined in sardine samples spiked at a 50,,g g,1 concentration level, with good results. Furthermore, the chromatographic PAD method was also used for monitoring the formation of histamine during the decomposition process of sardine samples. [source] On the precision and accuracy of structural analysis of light-induced metastable statesJOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 6 2007Vincent Legrand Bragg diffraction data were collected on single crystals of the spin-crossover complex [Fe(phen)2(NCS)2] in its low-spin and light-induced metastable high-spin states. Experimental variables included the temperature (32 and 15,K), the X-ray source (sealed tube and synchrotron), and the time interval between laser light excitation of the sample (, = 647,nm). From a comparison of the structural parameters refined, it is shown that photo-crystallographic measurements suffer significantly and systematically from bias if the probed sample contains residual ground-state species, resulting from an incomplete photo-conversion or a significant metastable- to ground-state relaxation. It follows that a 4% population of species in a different spin state affects the Fe,N bond lengths by more than three standard deviations, and the FeN6 polyhedron volume by as much as seven standard deviations, while the mean atomic position misfit exceeds 0.005,Ĺ. [source] Anthropometric and cephalometric measurements in X-linked hypohidrotic ectodermal dysplasiaORTHODONTICS & CRANIOFACIAL RESEARCH, Issue 4 2007MO Lexner Structured Abstract Authors,,, Lexner MO, Bardow A, Bjorn-Jorgensen J, Hertz JM, Almer L, Kreiborg S. Objective,,, To describe the somatic development and craniofacial morphology in males affected with hypohidrotic ectodermal dysplasia (HED) and female carriers and to find clinical markers for early clinical diagnosis of possible female carriers. Design,,, A clinical and radiographic examination of the affected males and the female carriers. Setting and sample population,,, Twenty-four affected males and 43 female carriers with a known mutation in the ED1 gene were examined in a dental clinic in either Copenhagen or Aarhus, Denmark. Experimental variables,,, Height, body mass index (BMI) and head circumference. Cephalometric analysis of the craniofacial morphology. Outcome measure,,, Data on the somatic and craniofacial development in the affected males and female carriers. Results,,, No difference was observed regarding body height in the affected males and female carriers, BMI values were lower than the mean in most affected boys and adolescence and head circumference was somewhat decreased in both groups compared to normative data. The cephalometric analysis showed a reduced maxilla length and prognathism, a normal size and shape of the mandible and a reduced sagittal jaw relationship in both HED groups. Furthermore, affected males had a retroclined nasal bone and a more anteriorly inclined maxilla. A short nose, protruding lips, reduced facial convexity and facial height, characterized the soft tissue profile of the affected males. In female carriers, the lips were significantly retruded when compared with controls. Conclusion,,, No specific somatic or cephalometric markers could be observed, in the female carrier group. [source] Optimization of growth medium for the production of ,-amylase from Bacillus amyloliquefaciens using response surface methodologyJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 4 2006M Saban Tanyildizi Abstract The optimization of nutrient levels for the production of ,-amylase by Bacillus amyloliquefaciens was carried out using response surface methodology (RSM) based on the 23 factorial central composite design (CCD). This procedure limited the number of actual experiments performed while allowing for possible interactions between three components. RSM was adopted to derive a statistical model for the effect of starch, peptone and yeast extract (YE) on ,-amylase production. The P -value of the coefficient for linear effects of starch and YE concentration was <0.0001, suggesting that this was the principal experimental variable, having the greatest effect on the production of ,-amylase. The optimal combinations of media constituents for maximum ,-amylase production were determined as 12.61 g L,1 starch, 2.83 g L,1 peptone and 1.25 g L,1 YE. The optimization of the medium resulted not only in a 34% higher enzyme activity than unoptimized medium but also in a reduced amount of the required medium constituents. Copyright © 2006 Society of Chemical Industry [source] Entropy,enthalpy compensation: Fact or artifact?PROTEIN SCIENCE, Issue 3 2001Kim Sharp Abstract The phenomenon of entropy,enthalpy (S-H) compensation is widely invoked as an explanatory principle in thermodynamic analyses of proteins, ligands, and nucleic acids. It has been suggested that this compensation is an intrinsic property of either complex, fluctuating, or aqueous systems. The questions examined here are whether the observed compensation is extra-thermodynamic (i.e., reflects anything more than the well-known laws of statistical thermodynamics) and if so, what does it reveal about the system? Compensation is rather variably defined in the literature and different usages are discussed. The most precise and interesting one, which is considered here, is a linear relationship between ,H and ,S for some series of perturbations or changes in experimental variable. Some recent thermodynamic data on proteins purporting to show compensation is analyzed and shown to be better explained by other causes. A general statistical mechanical model of a complex system is analyzed to explore whether and under what conditions extra-thermodynamic compensation can occur and what it reveals about the system. This model shows that the most likely behavior to be seen is linear S-H compensation over a rather limited range of perturbations with a compensation temperature Tc = d,H/d,S within 20% of the experimental temperature. This behavior is insensitive to the details of the model, thus revealing little extra-thermodynamic or causal information about the system. In addition, it will likely be difficult to distinguish this from more trivial forms of compensation in real experimental systems. [source] Initial symptoms and reactions to trauma-related stimuli and the development of posttraumatic stress disorderDEPRESSION AND ANXIETY, Issue 2 2005Karin Elsesser Ph.D. Abstract We investigated laboratory and experimental variables as predictors of the development of posttraumatic stress disorder (PTSD). Evoked heart rate response to trauma-related pictures, attentional bias in the dot-probe task, and viewing time were assessed in 35 victims of a traumatic event and again after 3 months. Data was compared to 26 control participants. At first assessment trauma victims showed heart rate (HR) acceleration and controls showed HR deceleration to trauma-related material. The group of trauma victims improved clinically over time. Predictors of the number of PTSD symptoms after 3 months were re-experiencing (33% of the variance) and amplitude of the evoked HR reaction to trauma-related pictures (15%). The two variables were highly correlated. Trauma victims were also more anxious, viewed trauma-related pictures for a longer time, and had a longer reaction time in the dot-probe task (but no distinct attentional bias) than control participants. Results indicate that specific fear responses and re-experiencing contribute to the development of posttraumatic stress disorder. Depression and Anxiety 21:61,70, 2005. © 2005 Wiley-Liss, Inc. [source] Study of Electrochemical Processes with Coupled Homogeneous Chemical Reaction in Differential Pulse Voltammetry at Spherical Electrodes and MicrohemispheresELECTROANALYSIS, Issue 16 2010Eduardo Laborda Abstract Homogeneous chemical reactions coupled to oxidation-reduction processes at electrode surfaces are very common in electrochemistry. In this paper we cope with the application of Differential Pulse Voltammetry at spherical electrodes and microhemispheres for the study of this kind of systems. Analytical expressions are deduced from which the influence of the different experimental variables is examined. Several diagnostic criteria for elucidation of the reaction mechanism from DPV peak parameters are given, as well as working curves for extraction of the kinetic rate constants of the chemical reaction. [source] Comparison of operative procedure variables on pulpal viability in an ex vivo modelINTERNATIONAL ENDODONTIC JOURNAL, Issue 5 2008P. E. Murray Abstract Aim, To measure and compare the responses of pulp tissue to cavity preparation and restoration variables using a novel tooth slice culture model. Methodology, Experimental cavities (265) were continuously cut, under carefully controlled conditions, into the dentine of the labial aspect of 28-day-old Wistar rat incisors, and slices of these teeth maintained in organ culture for up to 2 weeks. The experimental variables examined were: the preparation method, remaining dentine thickness, coolant, drill speed, conditioning with EDTA and filling materials. The reactions of the dentine,pulp complex to the experimental variables were measured using pathohistometric analysis and the correlations between variables were determined using analysis of variance statistical tests. Results, In rank order of surgically induced restorative pulpal injury, from the most to the least injurious were: remaining dentine thickness, absence of coolant during cavity preparation, bur speed, cavity conditioning treatments and the filling material. Conclusions, To reduce pulp injury and to promote pulpal repair activity, the correct use of appropriate materials are important. However, of relatively greater importance is the operative technique adopted, the need to avoid the excess removal of dentine and to minimize trauma during preparation. [source] Reductive decolourization and total organic carbon reduction of the diazo dye CI Acid Black 24 by zero-valent iron powderJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 7 2006Ming-Chin Chang Abstract In this study, wastewater contaminated by colour and total organic carbon from the diazo dye CI Acid Black 24 was successfully removed by reductive decolourization with zero-valent iron powder. The effects on decolourization of experimental variables such as iron dosage, initial dye concentration, pH and dissolved oxygen level were evaluated. The best removal efficiencies for decolourization of 99.7% and total organic carbon of 57.4% were obtained with an initial dye concentration of 25.0 mg L,1 and iron dosage of 200.0 g L,1. Moreover, the decolourization rates followed pseudo-first-order kinetic equations with respect to dye concentration. The colour removal efficiency was simultaneously dependent on iron dosage and various initial dye concentrations, although the colour and total organic carbon removal efficiencies linearly increased with increased iron dosage, reaching a maximum at 100.0 g L,1. A contour plot was developed to illustrate the 3D relation of removal efficiencies with initial dye concentration and iron dosage. For wastewater with a concentration range from 25 to 100 mg L,1 CI Acid Black 24 the suggested ideal operation conditions are 100.0 g L,1 iron dosage, pH 2-4, normal oxygen concentration of 5-7 mg L,1 and reaction time of 30-60 min. Copyright © 2006 Society of Chemical Industry [source] Optimization of an industrial afterburnerJOURNAL OF CHEMOMETRICS, Issue 1 2003Tomas Öberg Abstract An industrial afterburner was optimized using statistical experimental design. A computer-generated optimal design was adapted to domain constraints and previous knowledge about the experimental variables. Carbon monoxide was used as a general indicator for the operating conditions, and a reduced response surface model was fitted to the experimental data. In a second phase the initial results were verified and investigated in more detail with regard to chlorinated aromatics. The empirical models obtained were further interpreted using results from laboratory investigations and more fundamental knowledge from combustion theory. Copyright © 2003 John Wiley & Sons, Ltd. [source] Machine Vision Analysis of Antibrowning Potency for Oxalic Acid: A Comparative Investigation on Banana and AppleJOURNAL OF FOOD SCIENCE, Issue 6 2004R. Yoruk ABSTRACT: Relative antibrowning potency of oxalic acid on banana and apple slices was investigated using a machine vision system. Degree of browning on fresh-cut surfaces was evaluated visually and quantitatively by observing changes of CIE L* values and evaluating temporal changes in color spectra based on experimental variables, oxalic acid concentration, and storage time. Browning inhibition was most prominent on banana and apple slices treated with oxalic acid solutions at concentrations of 60 and 5 mM, respectively. Oxalic acid was a more potent antibrowning agent compared with other structurally related acids. Average residual oxalic acid levels in the tissues for an effective antibrowning activity were measured. [source] Optimization of the ESI and APCI experimental variables for the LC/MS determination of s-triazines, methylcarbamates, organophosphorous, benzimidazoles, carboxamide and phenylurea compounds in orange samplesJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 10 2007Guilherme M. Titato Abstract In this work, ten selected pesticides of different chemical groups, indicated to orange culture, were extracted and determined by liquid chromatography,mass spectrometry using both electrospray ionization (ESI) and atmospheric pressure chemical ionization (APCI) operating in the positive ion detection mode. Applying a variables selection technique verified that cone voltage, source temperature and drying-gas flow-rate are the critical variables when the ESI was used, while cone voltage was found to be the only critical variable for the MS system, operating with the APCI ionization mode. After optimization of the most important parameters through the variables selection technique, the selected ion-recording (SIR) mode, monitoring the [M + H]+ species for all the compounds, was applied for the method validation of the pesticides, in both ionization modes. In orange samples, matrix effects did not interfere with the determination of the pesticides. Pesticides quantification limits ranged from 10 to 50 µg kg,1 for ESI and from 8.2 to 45 µg kg,1 for APCI. Linearity was studied from LOQ upto 200 times LOQ values (r > 0.98). Recoveries obtained were in the range of 70.2,100.5% (RSDs less than 10%). In order to guarantee that the identification and confirmation of the studied pesticides in real samples were unequivocal, characteristic fragment ions of the pesticides were obtained by varying the cone voltage (in-source CID). Copyright © 2007 John Wiley & Sons, Ltd. [source] Considerations in measuring the electrical potentials of metallic restorations in vivoJOURNAL OF ORAL REHABILITATION, Issue 11 2000E. J. Sutow Many variables are believed to affect the accurate measuring of metallic restoration electrical potentials. This study examined the effects of intra- versus extra-oral location of the reference electrode, the type of metallic probe used to make contact with the restoration, and scratching and brushing of the restoration surface. Dental amalgam restorations were measured in 40 human subjects. Results showed that only the location of the reference electrode affected the central tendency of the potential. The study discusses the significance of some experimental variables in the accurate measuring of metallic potentials and the need to consider individual subject differences when statistically analysing for the central tendency of a sample. [source] Measurement of gibbsian surface excessAICHE JOURNAL, Issue 5 2001S. Sircar The Gibbsian Surface Excesses (GSE) are the true experimental variables for measurement of equilibria and kinetics for pure and multicomponent gas-solid adsorption. The gravimetric and volumetric methods, which are the most commonly used experimental procedures, are revisited. The common practice of ignoring helium adsorption during measurement of adsorbent density by helium pycnometry and measurement of void volumes in adsorption apparatus by helium expansion can lead to large errors in estimating GSE at high pressures and for less selectivity adsorbed components of a gas mixture. Methods to overcome these problems are described. [source] Effect of solvent quality on kinetics of tethered layer formationJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 21 2004Heqing Huang Abstract We conducted a study of the effect of solvent quality on the kinetics of formation of a layer of polymer chains tethered to a solid substrate. In these experiments, tethering was accomplished by means of chemical bond formation between reactive sites on the surface and the end-functional groups of the polymer chains in solution. All experimental variables were held constant except for the ,-parameter between the polymer and solvent. Variation in the ,-parameter was achieved by use of a series of nonpolar, organic solvents. The distinct three-regime kinetics, typical of tethering reactions run in a good solvent and in the absence of segmental adsorption, was observed over the range of values for the ,-parameter. As expected, an increase in the ,-parameter (a decrease in solvent quality) did result in increased tethering density, but, contrary to expectation, no increase in tethering rate was observed. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 5530,5537, 2004 [source] Enantioseparation of nuarimol by affinity electrokinetic chromatography-partial filling technique using human serum albumin as chiral selectorJOURNAL OF SEPARATION SCIENCE, JSS, Issue 18 2008Maria Amparo Martínez-Gómez Abstract The present paper deals with the enantiomeric separation of nuarimol enantiomers by affinity EKC-partial filling technique using HSA as chiral selector. Firstly, a study of nuarimol interactions with HSA by CE-frontal analysis was performed. The binding parameters obtained for the first site of interaction were n1 = 0.84; K1 = 9.7 ± 0.3×103 M,1 and the protein binding percentage of nuarimol at physiological concentration of HSA was 75.2 ± 0.2%. Due to the moderate affinity of nuarimol towards HSA the possibility of using this protein as chiral selector for the separation of nuarimol using the partial filling technique was evaluated. A multivariate optimization approach of the most critical experimental variables in enantioresolution, running pH, HSA concentration and plug length was carried out. Separation of nuarimol enantiomers was obtained under the following selected conditions: electrophoretic buffer composed of 50 mM Tris at pH 7.3; 160 ,M HSA solution applied at 50 mbar for 156 s as chiral selector; nuarimol solutions in the range of 2,8×10,4 M injected hydrodynamically at 30 mbar for 2 s and the electrophoretic runs performed at 30°C applying 15 kV voltage. Resolution, accuracy, reproducibility speed and cost of the proposed method make it suitable for quality control of the enantiomeric composition of nuarimol in formulations and for further toxicological studies. The results showed a different affinity between nuarimol enantiomers towards HSA. [source] Analysis of time-resolved X-ray scattering data from solution-state systemsACTA CRYSTALLOGRAPHICA SECTION A, Issue 2 2010Kristoffer Haldrup As ultrafast time-resolved studies of liquid systems with the laser pump/X-ray scattering probe method have come of age over the past decade, several groups have developed methods for the analysis of such X-ray scattering data. The present article describes a method developed primarily with a focus on determining structural parameters in the excited states of medium-sized molecules (~30 atoms) in solution. The general methodology is set in a maximum-likelihood framework and is introduced through the analysis of the photoactive platinum compound PtPOP, in particular the structure of its lowest triplet excited state (3A2u). Emphasis is put on structure determination in terms of model comparisons and on the information content of difference scattering signals as well as the related experimental variables. Several suggestions for improving the accuracy of these types of measurements are presented. [source] An evaluation of an aggression management training program to cope with workplace violence in the healthcare sectorRESEARCH IN NURSING & HEALTH, Issue 4 2008Janneke K. Oostrom Abstract Workplace violence is a major occupational hazard for healthcare workers, generating a need for effective intervention programs. The purpose of this study was to evaluate the effectiveness of an aggression management training program. The evaluation design was based on the internal referencing strategy, an unobtrusive and applicable evaluation method that rules out some major threats to internal validity without the need for a control group. On three occasions, training participants completed a questionnaire containing experimental and control variables. As hypothesized, there was a significant improvement in the experimental variables that was larger than the non-significant change in the control variable. We conclude that aggression management training may be an effective instrument in the fight against workplace violence. © 2008 Wiley Periodicals, Inc. Res Nurs Health 31:320,328, 2008 [source] AN EPR AND ISOTOPIC STUDY OF THE MARBLES OF THE TRAJAN's ARCH AT ANCONA: AN EXAMPLE OF ALLEGED HYMETTIAN PROVENANCE,ARCHAEOMETRY, Issue 4 2003D. Attanasio The provenance of 20 marble samples drawn from the Trajan's arch at Ancona, which is supposed to be made of Greek, Hymettian marble, has been established on the basis of the independent use of EPR and isotopic data. The results of the two methods are in good agreement and unequivocally indicate a Proconnesian provenance. Sixteen samples are assigned to this site, whereas two are classified as untypical Proconnesian samples and the remaining two are assigned an unlikely Parian provenance. No indication exists for a possible Hymettian origin of the marbles. A multi-method approach, which employs all of the experimental variables simultaneously, demonstrates that the 18 samples identified as Proconnesian belong to several different quarrying areas within the site. This result is taken as an indication that the Proconnesian quarries were run following a highly organized, semi-industrial production model. The origin of the Hymettian/Proconnesian misunderstanding and the possible misclassification of other Roman monuments in Italy are briefly commented on. [source] The interdependence of wavelength, redundancy and dose in sulfur SAD experimentsACTA CRYSTALLOGRAPHICA SECTION D, Issue 12 2008Michele Cianci In the last decade, the popularity of sulfur SAD anomalous dispersion experiments has spread rapidly among synchrotron users as a quick and streamlined way of solving the phase problem in macromolecular crystallography. On beamline 10 at SRS (Daresbury Laboratory, UK), a versatile design has allowed test data sets to be collected at six wavelengths between 0.979 and 2.290,Ĺ in order to evaluate the importance and the interdependence of experimental variables such as the Bijvoet ratio, wavelength, resolution limit, data redundancy and absorbed X-ray dose in the sample per data set. All the samples used in the experiments were high-quality hen egg-white lysozyme crystals. X-radiation damage was found to affect disulfide bridges after the crystals had been given a total dose of 0.20 × 107,Gy. However, with such a total dose, it was still possible in all cases to find a strategy to collect data sets to determine the sulfur substructure and produce good-quality phases by choosing an optimum combination of wavelength, exposure time and redundancy. A ,|,ano|/,(,ano), greater than 1.5 for all resolution shells was a necessary requirement for successful sulfur SAD substructure location. Provided this is achieved, it seems possible to find an optimum compromise between wavelength, redundancy and dose to provide phasing information. The choice of the wavelength should then follow the sample composition and the diffracting properties of the crystal. For strongly diffracting crystals, wavelengths equal or shorter than 1.540,Ĺ can be selected to capture the available data (provided the Bijvoet ratio is reasonable), while a longer wavelength, to gain as high a Bijvoet ratio as possible, must be used for more weakly diffracting crystals. These results suggest that an approach to a sulfur SAD experiment based on a complete description of the crystal system and the instrument for data collection is useful. [source] Optimization of a novel headspace,solid-phase microextraction,gas chromatographic method by means of a Doehlert uniform shell design for the analysis of trace level ethylene oxide residuals in sterilized medical devicesBIOMEDICAL CHROMATOGRAPHY, Issue 6 2009Michael P. DiCicco Abstract Medical devices sterilized by ethylene oxide (EtO) retain trace quantities of EtO residuals, which may irritate patients' tissue. Reliably quantifying trace level EtO residuals in small medical devices requires an extremely sensitive analytical method. In this research, a Doehlert uniform shell design was utilized in obtaining a response surface to optimize a novel headspace,solid-phase microextraction,gas chromatographic (HS-SPME-GC) method developed for analyzing trace levels of EtO residuals in sterilized medical devices, by evaluating sterilized, polymer-coated, drug-eluting cardiovascular stents. The effects of four independent experimental variables (HS-SPME desorption time, extraction temperature, GC inlet temperature and extraction time) on GC peak area response of EtO were investigated simultaneously and the most influential experimental variables determined were extraction temperature and GC inlet temperature, with the fitted model showing no evidence of lack-of-fit. The optimized HS-SPME-GC method demonstrated overall good linearity/linear range, accuracy, repeatability, reproducibility, absolute recovery and high sensitivity. This novel method was successfully applied to analysis of trace levels of EtO residuals in sterilized/aerated cardiovascular stents of various lengths and internal diameter, where, upon heating, trace EtO residuals fully volatilized into HS for extraction, thereby nullifying matrix effects. As an alternative, this novel HS-SPME-GC method can offer higher sensitivity compared with conventional headspace analyzer-based sampling. Copyright © 2009 John Wiley & Sons, Ltd. [source] Oriented Ensembles in Ultrafast Electron DiffractionCHEMPHYSCHEM, Issue 7 2006J. Spencer Baskin Abstract Electron scattering expressions are presented which are applicable to very general conditions of implementation of anisotropic ultrafast electron diffraction (UED) experiments on the femto- and picosecond time scale. "Magic angle" methods for extracting from the experimental diffraction patterns both the isotropic scalar contribution (population dynamics) and the angular (orientation-dependent) contribution are described. To achieve this result, the molecular scattering intensity is given as an expansion in terms of the moments of the transition-dipole distribution created by the linearly polarized excitation laser pulse. The isotropic component (n=0 moment) depends only on population and scalar internuclear separations, and the higher moments reflect bond angles and evolve in time due to rotational motion of the molecules. This clear analytical separation facilitates assessment of the role of experimental variables in determining the influence of anisotropic orientational distributions of the molecular ensembles on the measured diffraction patterns. Practical procedures to separate the isotropic and anisotropic components of experimental data are evaluated and demonstrated with application to reactions. The influence of vectorial properties (bond angles and rotational dynamics) on the anisotropic component adds a new dimension to UED, arising through the imposition of spatial order on otherwise randomly oriented ensembles. [source] | |||||||||||||||||||||||||