Reported Threshold Values Research Articles

Stainability and translucency of potassium aluminum sulfate applied computer-aided design and computer-aided manufacturing materials after coffee thermocycling.

The purpose of this in vitro study was to evaluate the effect of potassium aluminum sulfate (alum) application on the stainability and translucency of computer-aided design and computer-aided manufacturing (CAD-CAM) materials after coffee thermocycling (CTC). Disk-shaped specimens (Ø10 × 1 mm; N = 200) were fabricated by using additively (Crowntec [CT] and Varseo Smile Crown Plus [VS]) and subtractively manufactured (Brilliant Crios [RCR], CEREC Block [FC], and Vita Enamic [VE]) CAD-CAM materials and polished. All specimens were randomly divided into two groups as alum applied and control (n = 10). All specimens were then subjected to CTC (10,000 cycles at 5-55°C) and color coordinates were measured at each time interval. Color differences (ΔE00 ) and relative translucency parameters (RTPs) were calculated and the data were statistically analyzed (a = 0.05). Among tested time intervals, alum applied specimens had their lowest ΔE00 after alum application (p ≤ 0.006), except for FC (p = 0.177). In addition, alum applied RCR had lower ΔE00 values than its control specimens (p = 0.029). Alum applied specimens had their lowest RTP after CTC (p < 0.001) and alum application decreased the RTP of CT (p = 0.010). CTC reduced the RTP of all materials in control groups (p < 0.001). Alum applied CT had higher RTP than its control specimens (p = 0.049). Alum application's effect on color change varied depending on the material and alum mostly resulted in clinically acceptable changes in translucency. CTC led to unacceptable color and translucency changes based on previously reported threshold values. Optical properties of CAD-CAM materials and the sustainability of these properties over time is critical for longevity. Alum may improve the color stability of reinforced composite resin when subjected to long-term coffee consumption.

Effect of coffee thermocycling on the surface roughness and stainability of denture base materials with different chemical compositions manufactured with additive and subtractive technologies.

To evaluate the effect of coffee thermocycling (CTC) on the surface roughness (Ra ) and stainability of denture base materials with different chemical compositions fabricated by using additive and subtractive manufacturing. Disk-shaped specimens were additively (FREEPRINT denture, AM) or subtractively (G-CAM, GSM and M-PM, SM) fabricated from three pink denture base materials in different chemical compositions (n = 10). Ra was measured before and after polishing, while color coordinates were measured after polishing. Specimens were subjected to CTC (5000 cycles) and measurements were repeated. Color differences (ΔE00 ) after CTC were calculated. Ra among different time intervals within materials was evaluated by using repeated measures analysis of variance (ANOVA), while 1-way ANOVA was used to evaluate the Ra of different materials within each time interval and the ΔE00 values. Color coordinates within each material were compared by using paired samples t-tests (α = 0.05). Ra before polishing was the highest for all materials (p < 0.001), while SM had its lowest Ra after CTC and AM had its lowest Ra after polishing (p ≤ 0.008). Before polishing, AM had the highest Ra among the materials (p < 0.001). After polishing, SM had higher Ra than AM (p < 0.001). After CTC, GSM had the lowest Ra (p ≤ 0.048). SM had the lowest (p ≤ 0.031) and AM had the highest (p < 0.001) ΔE00 . CTC decreased the a* and b* values of SM and AM (p ≤ 0.017), and increased the L* values of AM (p < 0.001). Polishing significantly reduced the surface roughness of all materials. CTC did not increase the surface roughness of materials above the clinically acceptable threshold. Only AM had perceptible color change when previously reported threshold values for denture base materials were considered. Tested denture base materials may have similar surface stability after coffee thermocycling. However, subtractively manufactured denture base materials may have improved color stability when subjected to long-term coffee consumption.

Influence of polishing technique and coffee thermal cycling on the surface roughness and color stability of additively and subtractively manufactured resins used for definitive restorations.

To evaluate how different polishing techniques and coffee thermal cycling affect the surface roughness and stainability of additively and subtractively manufactured resins used for definitive prostheses. Two additively manufactured composite resins (Crowntec, CT and VarseoSmile Crown Plus, VS) and a subtractively manufactured resin nanoceramic (Cerasmart, CS) were used to fabricate 90 rectangular-shaped specimens (14 × 12 × 1mm) (n= 30). After baseline surface roughness (Ra) measurements, specimens were divided into three groups based on the polishing technique; conventional polishing with a 2-stage polishing kit (CP) and surface sealant application (Optiglaze, OG or Vita Akzent LC, VA) (n= 10). After polishing, specimens were subjected to 10,000 cycles of coffee thermal cycling. Ra and color coordinate measurements were performed after polishing and after coffee thermal cycling. Color difference (ΔE00) was calculated. Scanning electron microscope images were taken at each time interval. Kruskal-Wallis or 1-way analysis of variance (ANOVA) were used to evaluate Ra of materials within each polishing-time interval pair and different polishing techniques within each material-time interval pair, while Friedman or repeated measures ANOVA were used to evaluate Ra at different time intervals within each material-polishing pair. ΔE00 was assessed with 2-way ANOVA (α= 0.05). Other than VA-after polishing (p= 0.055), tested materials had significantly different Ra within each polishing-time interval pair (p ≤ 0.038). When Ra differences among different polishing techniques within each material-time interval pair were considered, CS had differences after coffee thermal cycling, CT had differences before polishing and after coffee thermal cycling, and VS had differences within each time interval (p ≤ 0.038). When Ra differences among different time intervals within each material-polishing pair were considered, significant differences were observed among all pairs (p ≤ 0.016), except for CS-VA (p= 0.695) and VS-VA (p= 0.300). ΔE00 values were affected by material and polishing technique interaction (p= 0.007). Ra of CS was similar to or lower than the Ra of other materials, regardless of the time interval or polishing technique. CP mostly led to lower Ra than other polishing techniques, whereas VA resulted in a high Ra regardless of the material-time interval pair. Polishing reduced the Ra, while coffee thermal cycling was found to have a small effect. Among tested material-polishing pairs, only CS-VA had moderately unacceptable color change when previously reported threshold values were considered.

Optical properties, biaxial flexural strength, and reliability of new-generation lithium disilicate glass-ceramics after thermal cycling.

To investigate the color stability, translucency, biaxial flexural strength (BFS), and reliability of nano-lithium disilicate and fully crystallized lithium disilicate after thermal cycling and to compare with those of a commonly used lithium disilicate. Three lithium disilicate glass-ceramics were used to prepare disk-shaped specimens (ø:12 mm, thickness: 1.2 mm) from A2 shaded HT blocks (Amber Mill, AM; Initial LiSi Block, IN; IPS e.max CAD, EX). AM and EX specimens were crystallized, and all specimens were polished with a polishing paste (Diamond Polish Mint). A spectrophotometer (CM-26d) was used to measure color coordinates before and after thermal cycling. BFS test was performed after thermal cycling. Color differences (ΔE00 ) and relative translucency parameter (RTP) values were calculated. One-way analysis of variance (ANOVA) (ΔE00 and BFS), two-way ANOVA followed by Tukey's HSD tests (RTP), and chi-square tests (Weibull modulus and characteristic strength) were used for the statistical analyses (α=0.05). No significant differences were observed among the ΔE00 values of tested materials (df=2, F=2.933, p=0.070). RTP values were only affected by material type (p<0.001) as AM had the highest RTP (p<0.001), whereas IN and EX had similar values (p≥0.165). BFS values varied among tested materials (df=2, F=21.341, p<0.001). AM and EX had similar BFS values (p=0.067) that were higher than that of IN (p≤0.001). Weibull moduli of the materials were similar (p=0.305), whereas EX had the highest and IN had the lowest characteristic strength values (p<0.001) CONCLUSIONS: Although nano-lithium disilicate had the highest translucency, all materials had imperceptible color and translucency changes after thermal cycling when reported threshold values were considered. Newly introduced lithium disilicate glass-ceramics had adequate flexural strength as compared to the precursor material.

Effect of sonication - cooking on the immunoreactivity of soy slurry from germinated soybeans

Soy proteins are globular in nature and are resistant to denaturation with lower intensity thermal treatments like cooking. Likewise, germination can also alter the protein structure through the activity of various enzymes and sonication can disrupt the molecular structure through cavitation and other ultrasound effects, and contribute to some reduction in immunoreactivity (IR) of allergens. This study evaluated the effects of germination and sonication pretreatment in combination with common cooking on lowering the soy allergen IR. Germination was carried out for up to 120 h and ultrasound sonication treatments were given for 20, 40 and 60 min at room temperature. Cooking at 100 ^oC was carried out for 10 to 60 min. The soy allergen IR was evaluated using a commercial sandwich ELISA kit. The combined action of germination, sonication and cooking helped to reduce the soy allergen IR to single digit mg/L levels from the nearly 400 mg/L initial level in the 5% soy slurry (&gt; 99% reduction). These levels are lower than the reported threshold values of soy allergens in foods. In addition, the germination and ultrasound process was shown to reduce the anti-nutritional properties and enhance the phenolic and radical scavenging activity by over 50%.

Global prevalence of gingival recession: A systematic review and meta-analysis.

This systematic review and meta-analysis aimed to estimate the global prevalence of gingival recession (GR) in the general population. Population-based observational studies reporting the prevalence of GR and published from 1991 to 2021 were identified from five electronic databases and manual searches. Risk of bias was assessed using the Joanna Briggs Institute's Critical Appraisal Checklist for Prevalence Studies. The pooled prevalence of GR was calculated by using a random-effect model. Grading of Recommendations, Assessment, Development and Evaluation (GRADE) approach was used to summarize the overall certainty of evidence. A total of 15 studies involving 37,460 participants were included. The overall pooled prevalence was 78.16% at the minimal reported threshold values and 84.92% at ≥1 mm "cut-off" with high heterogeneity among studies. A separate analysis for the buccal GR revealed a pooled prevalence of 75.42%. The risk of bias was found to be high for 10 and low for 5 studies. The overall certainty of the evidence was assessed to be very low. More than two-thirds of the population worldwide was found to be affected by GR. Studies with standard case definition and less heterogeneity are required to accurately estimate the prevalence of GR.

Pressure wave propagation effects in the eye after photoablation

A transient pressure wave created in photoablation-based laser corneal refractive surgery propagates along the optical axis of the eye from the cornea toward the fundus. Along its path, it is attenuated, reflected several times at tissue interfaces, focused due to the spherical shape of the cornea, and partially phase-converted to a tensile wave after passing the acoustic focus. Employing the numerical acoustic eye model, the dynamics of the acoustic focusing is described in detail. The simulated pressure waveforms are first validated against the existing measurements. Then, the calculated full pressure fields are used to obtain the extreme values of the pressure amplitude at every point within the eye over the whole timespan of interest. Over these pressure maps, various threshold contours obtained from the existing literature are superimposed to help ophthalmologists investigate the consequences of acoustic focusing within the human eye during laser keratorefractive surgery. The comparison indicates that the simulated negative peak pressure values used in the contemporary broad beam and flying spot laser-assisted in situ keratomileusis/photorefractive keratectomy treatments exceed some of the reported threshold values. The critical volume where the thresholds are surpassed is located near the lens-vitreous boundary and extends to the retina for wide beams. The photoablation-induced pressure wave focusing is, therefore, a mechanism that needs to be researched carefully and included in the list of potential risks accompanying refractive laser surgery.

Early stage periarticular injection during total knee arthroplasty may provide a better postoperative pain relief than late-stage periarticular injection: a randomized-controlled trial

PurposeThis study was performed to determine whether periarticular injection performed in the early stage of total knee arthroplasty (TKA) could provide a better postoperative pain relief than periarticular injection performed in the late stage of TKA. The hypothesis was based on the concept that analgesic intervention before the onset of noxious stimuli would be associated with less postoperative pain.MethodsA total of 105 participants were randomly assigned to receive superficial injection just prior to arthrotomy (early stage periarticular injection group) or superficial injection after implanting the prosthesis (late-stage periarticular injection group) in patients undergoing unilateral TKA with 1:1 treatment allocation. In both groups, deep injection was performed according to the same schedule (just prior to implanting prosthesis). The solution consisted of 300 mg of ropivacaine, 8 mg of morphine, 40 mg of methylprednisolone, 50 mg of ketoprofen, and 0.3 mg of epinephrine mixed with normal saline to a final volume of 60 mL. All surgeries were managed under general anesthesia without any regional blocks. Registry-specified primary outcome was postoperative pain score at rest measured at the recovery room using a 100-mm visual analog scale (VAS). The VAS score was compared between two groups and assessed to reach the reported threshold values for the minimal clinically important difference (MCID) of 10 mm for the postoperative VAS score.ResultsThe VAS score at the recovery room was significantly lower in the early stage periarticular injection group than the late-stage periarticular injection group (23 ± 25 mm versus 39 ± 34 mm, respectively; 95% confidence interval 4–28 mm; p = 0.0078). The mean difference in the primary outcome fulfilled the MCID value.ConclusionsBringing forward the timing of periarticular injection may provide significant and clinically meaningful improvement in pain following TKA under general anesthesia.Level of evidenceI.

Survival associated with cerebrospinal fluid analysis in downer adult dairy cows: A retrospective study (2006‐2014)

BackgroundThreshold values for total nucleated cell count (TNCC) and protein concentration in cerebrospinal fluid (CSF) of downer dairy cows suggestive of a spinal cord lesion were recently published.ObjectivesDetermine short‐ and long‐term survival of downer cows that underwent CSF analysis using the reported threshold values. Evaluate the prognostic value of these threshold values to predict short‐ and long‐term survival.AnimalsTwo hundred and fourteen downer adult dairy cows that underwent CSF analysis during hospitalization at the Centre Hospitalier Universitaire Vétérinaire (CHUV) of the Université de Montréal.MethodsRetrospective study. Medical records of downer adult dairy cows presented to the hospital between January 2006 and October 2014 for which CSF analysis results were available were studied. Short‐term (discharge from hospital) and long‐term (completion of lactation) survival were determined and compared in accordance with CSF TNCC and protein concentration, using a Chi‐square test.ResultsCows with CSF TNCC and/or protein concentration above the threshold values had a significantly lower short‐term survival rate (P = .02). The odds of nonsurvival of cows with one or both CSF values above the threshold values was 2.16 times higher than the odds for cows with values under the threshold values. CSF TNCC >4.5 cells/μL had sensitivity and specificity of 17.3% (95% CI: 10.7%‐25.7%) and 92.3% (95% CI: 85.4%‐96.6%), respectively, for predicting short‐term nonsurvival. CSF protein concentration >0.39 g/L had sensitivity and specificity of 20.9% (95% CI: 13.7%‐29.7%) and 91.4% (95% CI: 84.2%‐96.0%), respectively.ConclusionsCSF analysis above threshold values used in this study is associated with increased odds of short‐term nonsurvival.

No Clinically Important Difference in Pain Scores After THA Between Periarticular Analgesic Injection and Placebo: A Randomized Trial.

Periarticular analgesic injection (PAI) is being used more commonly for pain relief after orthopaedic surgeries. However, there is conflicting evidence regarding the effectiveness of PAI for post-THA pain relief. In a double-blind, randomized, controlled trial among patients undergoing same-day bilateral THA, with each patient serving as his or her own control, we asked: (1) Did the pain score as measured on a 100-mm VAS differ between the hips that received PAI versus placebo? (2) Were there differences in complications between the treatment and control hips in these patients? Over a 1-year period at one center, 45 patients underwent same-day bilateral THA; three were excluded for prespecified reasons, and two declined participation in this randomized, controlled trial, leaving 40 patients (80 THAs) in the study. Patients randomly received PAI in one hip and placebo in the contralateral hip; patients, surgeons, and nurses were blinded in terms of which hip received the PAI and which hip received a placebo saline injection. The PAI solution included ropivacaine, morphine hydrochloride hydrate, methylprednisolone, ketoprofen, and epinephrine. The primary outcome was the VAS for pain at rest 24 hours after THA, measured using a 100-mm horizontal VAS. The VAS score was compared between two groups and assessed to reach the reported threshold values for the minimum clinically important difference (MCID) of 20 mm for the postoperative VAS score. No patients were lost to followup, and there were no missing data for the primary outcome. Complications that occurred during the trial were recorded prospectively with emphasis on infection, wound complications, nerve palsy and allergic reactions to the injections. There were no clinically important differences between hips treated with the PAI and those treated with the placebo injection at any point. The hips that received PAI had less pain than those receiving placebo 24 hours after THA (16 ± 17 mm versus 22 ± 20 mm; mean difference, 6 mm; 95% confidence interval [CI], 2-9 mm; p = 0.006), but this effect size was below the MCID of 20 mm and thus is unlikely to be clinically important. The hips that received PAI also had better VAS scores in the recovery room (38 ± 29 mm versus 52 ± 33 mm; mean difference 14 mm; 95% CI, 5-23 mm; p = 0.004) and 3 hours after THA than placebo controls (28 ± 22 mm versus 37 ± 24 mm; mean difference 9 mm; 95% CI, 2-16 mm; p = 0.010). Neither of these differences exceeded the MCID and likewise were unlikely to be clinically important. No complications, including surgical site infections, were observed in either group. Periarticular analgesic injection for pain control after THA did not result in a clinically important reduction in pain at any point examined. Given the expense associated with this PAI mixture and the lack of effectiveness outside this timeframe, we cannot recommend its use. Other mixtures or concentrations of drugs may be helpful in short-stay admissions for THA, but this will require further research. Level I, therapeutic study.

Threshold for permanent refractive index change in crystalline silicon by femtosecond laser irradiation

An optical damage threshold for crystalline silicon from single femtosecond laser pulses was determined by detecting a permanent change in the refractive index of the material. This index change could be detected with unprecedented sensitivity by measuring the resonant wavelength shift of silicon integrated optics microring resonators irradiated with femtosecond laser pulses at 400 nm and 800 nm wavelengths. The threshold for permanent index change at 400 nm wavelength was determined to be 0.053 ± 0.007 J/cm2, which agrees with previously reported threshold values for femtosecond laser modification of crystalline silicon. However, the threshold for index change at 800 nm wavelength was found to be 0.044 ± 0.005 J/cm2, which is five times lower than the previously reported threshold values for visual change on the silicon surface. The discrepancy is attributed to possible modification of the crystallinity of silicon below the melting temperature that has not been detected before.

Volatile sulfur compounds in pasteurised and UHT milk during storage

Cooked or sulfurous off-flavour caused by volatile sulfur compounds (VSCs) limits acceptance of ultra-high temperature (UHT) milk in some parts of the world. Therefore, the concentrations of VSCs in UHT milk over 16 weeks of storage were studied and compared with those in pasteurised milk. The major VSCs contributing to the cooked flavour were identified using solid-phase microextraction and gas chromatography with pulsed flame photometric detection. Nine VSCs were detected in commercial indirectly processed UHT skim and whole milk. These were hydrogen sulfide, carbonyl sulfide, methanethiol, dimethyl sulfide, carbon disulfide, dimethyl disulfide, dimethyl sulfoxide, dimethyl sulfone and dimethyl trisulfide. An additional VSC was detected but not identified. The concentrations of hydrogen sulfide, methanthiol, dimethyl sulfide and dimethyl trisulfide were initially higher than their reported threshold values indicating their importance in milk flavour, especially cooked flavour. However, they decreased slowly during storage to levels below their threshold values. This decrease corresponded to a decrease in dissolved oxygen level. Four VSCs, carbon disulfide, dimethyl sulfide, dimethyl sulfoxide and dimethyl disulfide, were detected in pasteurised milk; however, their concentrations were lower than their reported threshold values. This paper puts into perspective the significance of VSCs in the flavour of UHT and pasteurised milk, both initially and during storage, and indicates the period of storage for minimisation of cooked flavour in UHT milk.

The Increased Contribution of Atmospheric Nitrogen Deposition to Nitrogen Cycling in a Rural Forested Area of Kyushu, Japan

Japan has been receiving increasing levels of atmospheric nitrogenous pollutants from the East Asian continent over the last few decades, so it is critical to evaluate the impact of this increased atmospheric nitro- gen (N) deposition on N cycling even in rural forests. Thisstudyevaluatedthecontributionofthecurrent level of atmospheric N deposition to N cycling in a rural forested area. Bulk precipitation and stream water were collected during 2007-2011 at the Shiiba Research Forest (SRF) located in the central Kyushu mountain range of southern Japan. Litterfall was also collected to investigate thecontributionofatmospheric N deposition to total N input (litterfall N+atmospheric N deposition). The results showed that atmospheric depositions of both nitrate (NO3 � ) and ammonium (NH4 + )w ere af ew times higher during 2009-2011 than in 1991. This could be the result of additional N deposition from the increased long-range transport of nitrogenous pollutants from the East Asian continent. The current level of annual N deposition (9.7 kg N ha �1 year �1 ) at the SRF was com- parable with that at many urban sites and was close to the reported threshold values causing N saturation in forest ecosystems. Although current atmospheric N deposition was an important component (23 %) of total N input (43 kg N ha �1 year �1 ) at the SRF, the concentrations of NO3 � in stream water were consistently low (<10 μmol L �1 ). These results indicate that atmospheric N deposition is currently largely incorporated into forest ecosystems without excess N export from forested watersheds.

Two-Dimensional Tomography from Noisy Projections Taken at Unknown Random Directions.

Computerized tomography is a standard method for obtaining internal structure of objects from their projection images. While CT reconstruction requires the knowledge of the imaging directions, there are some situations in which the imaging directions are unknown, for example, when imaging a moving object. It is therefore desirable to design a reconstruction method from projection images taken at unknown directions. Another difficulty arises from the fact that the projections are often contaminated by noise, practically limiting all current methods, including the recently proposed diffusion map approach. In this paper, we introduce two denoising steps that allow reconstructions at much lower signal-to-noise ratios (SNRs) when combined with the diffusion map framework. In the first denoising step we use principal component analysis (PCA) together with classical Wiener filtering to derive an asymptotically optimal linear filter. In the second step, we denoise the graph of similarities between the filtered projections using a network analysis measure such as the Jaccard index. Using this combination of PCA, Wiener filtering, graph denoising, and diffusion maps, we are able to reconstruct the two-dimensional (2-D) Shepp-Logan phantom from simulative noisy projections at SNRs well below their currently reported threshold values. We also report the results of a numerical experiment corresponding to an abdominal CT. Although the focus of this paper is the 2-D CT reconstruction problem, we believe that the combination of PCA, Wiener filtering, graph denoising, and diffusion maps is potentially useful in other signal processing and image analysis applications.

Effect of Henry's law constant and operating parameters on vacuum-assisted headspace solid phase microextraction

Nonequilibrium headspace solid-phase microextraction (HSSPME) sampling under vacuum conditions may dramatically improve extraction kinetics compared to regular HSSPME at room temperature. This paper investigates the effects of organic analyte properties and sampling parameters (headspace volume and sample agitation) on vacuum-assisted HSSPME (Vac-HSSPME). It was found that at room temperature, acceleration effects on extraction rates induced by reducing the total pressure of the sample container are important for those compounds where the Henry's law constant, KH, is close or below the reported threshold values for low KH solutes. For these compounds evaporation rate is controlled by mass transfer resistance in the thin gas-film adjacent to the gas/sample interface and reducing the total pressure will increase evaporation rates and result in a faster overall extraction process. Conversely, for analytes with an intermediate KH value, Vac-HSSPME is not expected to improve extraction rates compared to regular HSSPME given that mass transfer resistance in the liquid-film becomes important. In accordance with the theory, at equilibrium, the amount of analyte extracted by the SPME fiber is not affected by the pressure conditions inside the sample container. Furthermore, Vac-HSSPME extraction kinetics for low KH analytes were marginally affected by the tested change in headspace volume as evaporation rates dramatically increase under reduced pressure conditions and the sample responds much faster to the concentration drops in the headspace when compared to regular HSSPME. At equilibrium however, increasing the headspace volume may result in a loss of sensitivity for Vac-HSSPME similar to that observed for regular HSSPME. As expected, stirring the liquid sample was found to improve Vac-HSSPME. Finally, the method yielded a linearity of 0.998 and detection limits in the ppt level. The precision varied between 1.8% and 8.4%.

Use of a Calibration Gas Generator for Irritation Threshold Assessment and As Supplement of Dynamic Dilution Olfactometry

Human odor and mucosal membrane irritation thresholds are used as criteria for assessing air quality in occupational and environmental settings. Unfortunately, reported threshold values still differ by several orders of magnitude rendering most standard compilations of little practical utility. Thus, in view of the need to repeat odor threshold measurements with a reliable methodology, a new technical approach based on original equipment manufacturer integrated solutions is presented. To test applicability, a calibration gas generator was used to continuously generate a fixed odor vapor concentration. Different dilution steps were realized by coupling to a purchasable olfactometer. Comparison with the "standard," that is, odor stimulus supply via sample bags revealed good correspondence. As a second step, the calibration gas generator was used to generate rapid changes in stimulus concentration between consecutive trials. Irritation thresholds were measured with an ascending series of ammonia concentrations generated from an aqueous solution. The obtained thresholds lay within the range previously reported. The introduced technology enables quick and reliable odor stimulus generation and provides flexibility in choosing the optimal start concentration, the step-size between dilutions, and the range of stimulus concentrations. Errors from usage of rotameters or sample bags can be avoided.

The importance of setting the right genetic distance threshold for identification of clones using amplified fragment length polymorphism: a case study with five species in the tropical plant genus Piper

Amplified fragment length polymorphism (AFLP) has been widely used for clone identification, but numerous studies have shown that clonemates do not always present identical AFLP fingerprints. Pairwise AFLP distances that distinguish known clones from nonclones have been used to identify a threshold genetic dissimilarity distance below which samples are considered to represent a single clone. Most studies to date have reported threshold values between 2% and 4%. Here, I determine the consistency of the clonal threshold across five species in the tropical plant genus Piper, and evaluate the sensitivity of genetic diversity indices and estimates of frequency of clonal reproduction to the threshold value selected. I sampled multiple ramets per individual from widely distributed plants for each of the five Piper species to set a threshold at the point where the error rate of clonal assignments was lowest. I then sampled all individuals of each shade-tolerant species in a 1-ha plot, and of each light-demanding species in 25×35-m plot, to estimate the frequency of asexual recruitment in natural populations using a series of different thresholds including the threshold set with the preliminary sampling. Clonal threshold values for the different species ranged from 0% to 5% AFLP genetic dissimilarity distance. To determine the sensitivity of estimates of clonal reproduction, I calculated several clonal diversity indexes for the natural populations of each of the five species guided by the range in clonal threshold values observed across the five Piper species. I show that small changes in the value of the clonal threshold can lead to very different conclusions regarding the level of clonal reproduction in natural populations.

Field Experiences with RDD and Overlay Tester for Concrete Pavement Rehabilitation

Since reflective cracking is related to both the existing pavement condition and the overlay material, appropriate tools are needed to characterize both properties. The rolling dynamic deflectometer (RDD) was employed to measure the continuous deflection profiles that relate to vertical movements of the underlying joints and cracks. An overlay tester (OT) was utilized to characterize the asphalt mix’s ability to resist reflective cracking. The reported threshold values were employed in the study that include: (1) W1–W3=6.5 mils for composite pavement with old asphalt concrete (AC) overlay; (2) W1–W3=5.5 mils for exposed concrete pavement; and (3) 700 cycles of the OT were employed to evaluate six field rehabilitation projects (SH12, IH20, US96, SH73, SH225, and IH44). It was found that although there were severe transverse cracks and spalling on US96, all W1–W3 deflections were less than 5.5 mils , indicating low risk for reflective cracking. A stone-mastic asphalt (SMA) layer was placed 3 years ago and t...

An Electrospray Ionization Source for Thermochemical Investigation with the Guided Ion Beam Mass Spectrometer

An electrospray ionization (ESI) source developed for use with the guided ion beam tandem mass spectrometer (GIBMS) is described. For accurate determination of thermochemistry using threshold collision-induced dissociation (TCID), it is essential that any source produces ions with four exacting characteristics: (1) high intensity, (2) stable signal, and well-defined energies both (3) kinetic, and (4) internal. To accomplish these objectives, the ions generated by the electrospray are collected using a radio frequency electrodynamic ion funnel and are then transferred into a hexapole ion guide where they are thermalized and subsequently passed into higher-vacuum regions for analysis. The resulting ion intensities using this source can exceed 10(6) ions/s. Stable beams (<10% variation in signal) can be generated over multiple hours. The kinetic energy distribution of ions emerging from this source has been shown to be well described by a Gaussian distribution with a full width half maximum (FWHM) of about 0.1-0.2 eV in the laboratory frame of reference. Finally, TCID results for ions generated with this source show excellent agreement with previously reported threshold values for ions generated using a variety of sources and experimental methodologies. This confirms that internal energies of the ions are well described by a Maxwell-Boltzmann distribution at room temperature.

COMPARISON OF BLOOD DAMAGE PREDICTIONS FROM FLUID MEASUREMENTS AND COMPUTATIONS TO IN VITRO AND IN VIVO OBSERVATIONS IN A CENTRIFUGAL BLOOD PUMP

The accurate prediction of the blood damage caused by fluid shearing is necessary for the design of blood contacting devices. It has been shown that fluid dynamics can be used to predict both hemolysis and thrombosis. Numerous studies of the fluid dynamic conditions for hemolysis and activation of the clotting cascade exist and have been used to estimate the damage potential of devices. Still, these predictions are not generally accurate and reliable because of 1) the high variability of reported threshold values, 2) the fact that estimates of turbulent stresses (Reynolds stresses) are often compared to threshold values of viscous stress and 3) the lack of studies that have shown that relations developed for simple flows are effective in damage predictions of complicated flows. A graphical summary of available data is presented. Estimates of damage based on measurement and numerical simulation of the flow within a centrifugal blood pump are compared to levels of damage from animal implant experiments. The effectiveness of prediction based on comparing shear and velocity fields to published relations is evaluated. Results: While the application of commonly used relations between shear stress, exposure time, and blood damage would predict extensive damage in this pump, actual measured damage is negligible. It is suggested that revised empirical fits to the available data be used along with consideration of turbulent length scales in the flow and that the distinction between viscous and Reynolds stresses must be maintained.