High-concentration Mixtures Research Articles

Backfire control and power enhancement of a hydrogen internal combustion engine

Frequent backfire can occur in inlet port fuel injection hydrogen internal combustion engines (HICEs) when the equivalence fuel–air ratio is larger than 0.56, thus limiting further enhancement of engine power. Thus, to control backfire, an inlet port fuel injection HICE test system and a computational fluid dynamics model are established to explore the factors that cause backfire under high loads. The temperature and the concentration of the gas mixture near the intake valves are among the essential factors that result in backfire. Optimizing the timing and pressure of hydrogen injection reduces the concentration distribution of the intake mixture and the temperature of the high-concentration mixture through the inlet valve, thus allowing control of backfire. Controlling backfire enables a HICE to work normally at high equivalence fuel–air ratio (even beyond 1.0). A HICE with optimized hydrogen injection timing and pressure demonstrates significant enhancement of the power output.

Modeling and analysis of personal exposures to VOC mixtures using copulas

Environmental exposures typically involve mixtures of pollutants, which must be understood to evaluate cumulative risks, that is, the likelihood of adverse health effects arising from two or more chemicals. This study uses several powerful techniques to characterize dependency structures of mixture components in personal exposure measurements of volatile organic compounds (VOCs) with aims of advancing the understanding of environmental mixtures, improving the ability to model mixture components in a statistically valid manner, and demonstrating broadly applicable techniques. We first describe characteristics of mixtures and introduce several terms, including the mixture fraction which represents a mixture component's share of the total concentration of the mixture. Next, using VOC exposure data collected in the Relationship of Indoor Outdoor and Personal Air (RIOPA) study, mixtures are identified using positive matrix factorization (PMF) and by toxicological mode of action. Dependency structures of mixture components are examined using mixture fractions and modeled using copulas, which address dependencies of multiple variables across the entire distribution. Five candidate copulas (Gaussian, t, Gumbel, Clayton, and Frank) are evaluated, and the performance of fitted models was evaluated using simulation and mixture fractions. Cumulative cancer risks are calculated for mixtures, and results from copulas and multivariate lognormal models are compared to risks calculated using the observed data. Results obtained using the RIOPA dataset showed four VOC mixtures, representing gasoline vapor, vehicle exhaust, chlorinated solvents and disinfection by-products, and cleaning products and odorants. Often, a single compound dominated the mixture, however, mixture fractions were generally heterogeneous in that the VOC composition of the mixture changed with concentration. Three mixtures were identified by mode of action, representing VOCs associated with hematopoietic, liver and renal tumors. Estimated lifetime cumulative cancer risks exceeded 10−3 for about 10% of RIOPA participants. Factors affecting the likelihood of high concentration mixtures included city, participant ethnicity, and house air exchange rates. The dependency structures of the VOC mixtures fitted Gumbel (two mixtures) and t (four mixtures) copulas, types that emphasize tail dependencies. Significantly, the copulas reproduced both risk predictions and exposure fractions with a high degree of accuracy, and performed better than multivariate lognormal distributions. Copulas may be the method of choice for VOC mixtures, particularly for the highest exposures or extreme events, cases that poorly fit lognormal distributions and that represent the greatest risks.

Morphological Characterization of DMPC/CHAPSO Bicellar Mixtures: A Combined SANS and NMR Study

Spontaneously forming structures of a system composed of dimyristoyl phosphatidylcholine (DMPC) and 3-[(3-cholamidopropyl)dimethylammonio]-2-hydroxy-1-propanesulfonate (CHAPSO) were studied by small-angle neutron scattering (SANS), (31)P NMR, and stimulated echo (STE) pulsed field gradient (PFG) (1)H NMR diffusion measurements. Charged lipid dimyristoyl phosphatidylglycerol (DMPG) was used to induce different surface charge densities. The structures adopted were investigated as a function of temperature and lipid concentration for samples with a constant molar ratio of long-chain to short-chain lipids (= 3). In the absence of DMPG, zwitterionic bicellar mixtures exhibited a phase transition from discoidal bicelles, or ribbons, to multilamellar vesicles either upon dilution or with increased temperature. CHAPSO-containing mixtures showed a higher thermal stability in morphology than DHPC-containing mixtures at the corresponding lipid concentrations. In the presence of DMPG, discoidal bicelles (or ribbons) were also found at low temperature and lower lipid concentration mixtures. At high temperature, perforated lamellae were observed in high-concentration mixtures (≥7.5 wt %) whereas uniform unilamellar vesicles and bicelles formed in low-concentration mixtures (≤2.5 wt %), respectively, when the mixtures were moderately and highly charged. From the results, spontaneous structural diagrams of the zwitterionic and charged systems were constructed.

Acute respiratory distress syndrome due to exposure to high-concentration mixture of ethenone and crotonaldehyde

Acute inhalational exposure leads to rapidly progressive acute respiratory distress syndrome (ARDS). This report is the first one to present a patient with ARDS in relation to long-standing exposure to a high-concentration mixture of ethenone and crotonaldehyde. A male worker in a chemical plant was accidentally exposed to the mixture of high-concentrated ethenone and crotonaldehyde for 5min in an open space and worked continuously in the polluted area for approximately 12h. On admission, he was conscious with the following vital parameters: blood pressure, 151/91mmHg; pulse rate, 107beats/min; respiratory rate, 30breaths/min; temperature, 37.6°C; oxygen saturation, 92% supported by mask saturation 10L/min; arterial blood gases showed P/F oxygen ratio of less than 200. Physical examination disclosed decreased bilateral vesicular sounds. A chest computed tomography revealed bilateral nonsegmental ground-glass opacities. The patient was mechanically ventilated and treated with corticosteroid. The patient was discharged without any symptoms. Exposure to mixtures of ethenone and crotonaldehyde can cause severe pulmonary injury leading to delayed ARDS.

Effect of high manganese substitution at ZnO host lattice using solvothermal method: Structural characterization and properties

We studied the effect of high manganese substitution at ZnO host lattice and report the optical and magnetic properties of Zn1−xMnxO (at x = 0.31, 0.50 and 0.62) nanoparticles (2–10 nm) prepared by the modified solvothermal method for the first time. Composition of these solid solutions was measured by ICP analysis. Solid solution of Zn0.69Mn0.31O (2 nm) was successfully synthesized, however at high dopant concentration (50% and 62% Mn) mixture of phases appeared instead of forming solid solution. UV–visible studies show the absorption edge at 385 nm for x = 0.31 and 0.50 which is slightly red shifted compared to pure ZnO, however Zn0.38Mn0.62O shows the presence of hausmannite phase of Mn3O4. Specific surface area of these nanoparticles was found to be 48, 100, and 47 m2 g−1. Magnetization measurements reveal that Zn0.69Mn0.31O and Zn0.50Mn0.50O show paramagnetic behaviour with antiferromagnetic coupling, however Zn0.38Mn0.62O shows ferrimagnetism.

Bi-level optimizing control of a simulated moving bed process with nonlinear adsorption isotherms

Abstract A bi-level optimizing control scheme originally proposed for a simulated moving bed (SMB) with linear isotherms has been extended to an SMB with nonlinear isotherms. Cyclic steady state optimization is performed in the upper level to determine the optimum switching period and time-varying feed/desorbent flow rates, and repetitive model predictive control is run in the lower level for purity regulation, taking the decision variables from the upper level as feed-forward information. Experimental as well as numerical study for an SMB process separating a high-concentration mixture of aqueous l-ribose and l-arabinose solutions showed that the proposed scheme performs satisfactorily against various disturbances. In contrast, an alternative scheme based on an SMB model with linear isotherms showed a limitation in the control performance; this scheme was apt to fail in purity regulation.

Copulas and Other Multivariate Models of Personal Exposures to VOC Mixtures

ABSTRACT While exposures to most pollutants occur in mixtures with other pollutants, joint distributions of pollutants have not been characterized, even for pollutants that frequently occur together. This study investigates exposures to volatile organic compounds (VOCs), and presents and evaluates innovative ways of modeling mixtures. Personal exposures to ten VOCs for 655 individuals were evaluated using a semi-parametric framework that estimates probabilities of mixtures containing components greater than specified levels. Common mixtures were identified using positive matrix factorization. Copulas were tested for their ability to model inter-pollutant dependencies, focusing on the most exposed individuals. For highly correlated VOCs, Gumbel and Gaussian copulas best described the joint probability. For VOCs with low correlations, distributions could be described by the product copula, among other approaches. High concentration mixtures usually resulted from strong sources (e.g., residence with attached garage), certain behaviors (e.g., cigarette smoking), and sometimes from multiple but unrelated sources (e.g., mothballs, solvents). This is the first article to characterize exposures to VOC mixtures measured using personal monitoring and a population-based sample, and it appears to be the first to apply the copula technique, which allows accurate modeling of joint distributions with only one additional parameter beyond those needed to represent the marginal distributions.

Slope debris flows in the Wenchuan Earthquake area

Avalanches and landslides, induced by the Wenchuan Earthquake on May 12, 2008, resulted in a lot of disaggregated, solid material on slopes that could be readily mobilized as source material for debris flows. Rainstorms triggered numerous slope debris flows with great damage to highways and rivers over the subsequent two years. Slope debris flows (as opposed to channelized debris flows) are defined as phenomena in which high-concentration mixtures of debris and water flow down slopes for short distances to highways and river banks. Based on field investigations and measurements of 19 slope debris flows, their main characteristics and potential mitigation strategies were studied. High rainfall intensity is the main triggering factor. Critical rainfall intensities for simultaneous occurrence of single, several and numerous slope debris flow events were 20 mm/day, 30mm/day, and 90 mm/day, respectively. Field investigations also revealed that slope debris flows consist of high concentrations of cobbles, boulders and gravel. They are two-phase debris flows. The liquid phase plays the role of lubrication instead of transporting medium. Solid particles collide with each other and consume a lot of energy. The velocities of slope debris flows are very low, and their transport distances are only several tens of meters. Slope debris flows may be controlled by construction of drainage systems and by reforestation.

Probiotic Therapy for Ulcerative Colitis

In 2009, 2 manuscripts were added to the literature that demonstrated the effectiveness of probiotics in inducing remission in patients with ulcerative colitis. The first manuscript was published by Miele and colleagues. Twenty-nine newly diagnosed ulcerative colitis patients were randomized to receive either VSL#3 on a weight-based dose or a placebo in conjunction with concomitant steroid induction and mesalamine maintenance treatment. The subjects were children with a mean age of 9.8 years ranging from 1.7 to 16.1 years. There were 13 females and 16 males. The subjects were thoroughly evaluated at 1 month, 2 months, 6 months, and 1 year after the diagnosis or at the time of relapse. All 29 patients responded at the induction of therapy, and remission was achieved in 13 patients (92.8%) treated with VSL#3 and inflammatory bowel disease therapy and in 4 patients treated with placebo and inflammatory bowel disease therapy. This gave a clear statistical result of effectiveness of the probiotics with a P level of less than 0.001. At 1 year, 3 of the 14 patients treated with the probiotics relapsed, whereas 11 of 15 on the placebo relapsed, again giving a significant P value of less than 0.014. The authors concluded that their randomized, placebo-controlled trial suggested the efficacy and safety of a high concentrated mixture of probiotic bacteria, VSL#3, in active ulcerative colitis and demonstrated its role in maintenance of remission. The study carried out in Italy included both endoscopic and histologic evaluations. The second study was carried out in India by Sood and colleagues and again revealed that VSL#3 was safe and effective in achieving clinical responses and remissions in patients with mild-to-moderately active ulcerative colitis. They had randomized adult patients to groups that were given VSL#3 (n=77) or placebo (n=70) twice daily for 12 weeks. Their end point was a 50% decrease in the ulcerative colitis disease activity index at 6 weeks, and a secondary end point included remission at 12 weeks and reduction in total individual Ulcerative Colitis Disease Activity Index parameters. Comparing the probiotic treatment group to the placebo gave a clear P value of less than 0.001, and at 12 weeks there were 33 patients on the probiotics which achieved remission, whereas only 11 patients given placebo had a remission, again with a P value of less than 0.0001. These 2 reports seem to tip the scale in favor of recommending probiotic therapy for ulcerative colitis. The dose in the first article was weight-related, but in the second article it was 3.6! 10 colony forming units twice daily (4 sachets). By definition, probiotics are live human bacteria when fed in either pills, tablets, or foods that benefit the host. The first clinical study on the use of a probiotic in ulcerative colitis was reported by Rembacken and colleagues in 1999. They randomized patients with active ulcerative colitis to either mesalamine 800mL three times daily or Escherichia coli Nissle 1917 strain for up to 3 months of therapy. Remission had been induced with the use of corticosteroids. Remission was obtained in 75% of patients treated with the mesalamine and 68% treated with the probiotics. There is difficulty in interpreting this study because of the small differences in the time to remission, 42 days for the probiotics patients and 44 days for the mesalamine. Some interpreted this as meaning that they both work but, in contrast, the use of the mesalamine was at a very low dose. Nevertheless, this was the first study that gave some indication that probiotics may work. In 2007, a Yale University Workshop was held to review the medical literature on the use of probiotics in ulcerative colitis. This review was carried out by Fedorak and Dieleman which revealed that there were 15 controlled studies reported since 1980, and induction of remission was noted in 7 studies evaluating 350 patients. It seemed that induction of remission did occur but that the results varied. The most effective probiotics used were E. coli Nissle strain and VSL#3. A detailed review on maintenance of remission by these same authors revealed that there were 8 studies using 775 patients. Four showed clear maintenance remission and 4 did not. Again, the most effective organisms were E. coli Nissle and VSL#3. In the most recent review of the literature by Kroeker and Dieleman, their recommendation for probiotic use in ulcerative colitis, quoting an update in the Yale review,

Update on the role of probiotics in the therapy of pediatric inflammatory bowel disease

Probiotics have had many applications in the past few years, and inflammatory conditions of the GI tract – including chronic disorders such as inflammatory bowel disease (IBD) – have received the most attention by investigators. In fact, the experimental basis to expect clinical efficacy of probiotics in IBD is quite robust. In spite of this however, only minimal evidence of benefit by any probiotic is currently available in Crohn’s disease, either in adult or in pediatric populations. In ulcerative colitis, on the other hand, several probiotic formulations and especially the proprietary preparation VSL#3 (a high-concentration mixture) have been found effective as adjuvant therapy, both in inducing and maintaining remission.

High-Frequency Oscillations in the Belousov−Zhabotinsky Reaction

Chemical oscillations in the classic Belousov-Zhabotinsky (BZ) system typically have a period of a few minutes, which can be increased significantly by changing the organic substrate. Here we show that by changing the temperature and concentrations, an increase of 3-4 orders of magnitude in the frequency of BZ oscillations can be obtained. At elevated temperatures, in high concentration mixtures, the cerium-catalyzed reaction exhibits sinusoidal oscillations with frequencies of 10 Hz or greater. We report the effect of temperature on the frequency and shape of oscillations in experiments under batch conditions and in a four-variable model. We show that our simple model accurately captures the complex temporal behavior of the system and suggests paths toward even higher frequencies.

Electro-optic and dielectric behavior of a FLC material having doped with a non-mesogenic polar molecules

Abstract Liquid crystal mixtures of non-mesogenic polar molecule with a commercial ferroelectric liquid crystal (FLC) mixture were prepared. Two mixtures were prepared by mixing 0.5% (w/w) and 1% (w/w) of polar molecules with commercial FLC mixture. Comprehensive studies of dielectric and electro-optic properties of the commercial FLC mixture and the polar molecules doped FLC mixtures have been made as a function of temperatures. Our studies reveal a higher tilt angle in lower concentration (0.5%) mixture but in case of 1% mixture tilt angle is decreased in comparison to 0.5% mixture. The spontaneous polarization of the commercial FLC mixture and other two mixtures is almost equal in magnitude at all temperatures. At the lower temperature region of SmC ∗ phase, Goldstone mode (GM) dielectric strength of the commercial FLC mixture and low concentration (0.5%) mixture is found almost equal but it is slightly higher in case of high concentration (1%) mixture. With the increase of temperature GM dielectric strength of both the doped mixtures rapidly converges at different temperatures which are much lower than the temperature of transition ( T C ) from SmC ∗ – SmA phase. The results have been discussed.

Effects of Atrazine and Metolachlor on the Survivorship and Infectivity of Echinostoma trivolvis Trematode Cercariae

Parasites play important roles in ecosystems and can be impacted by chemical inputs. In a series of experiments, we examined the impact of two common herbicides, metolachlor and atrazine, on a host-parasite system consisting of the trematode, Echinostoma trivolvis and its two intermediate hosts, the snail Planorbella trivolvis and larval Rana spp. tadpoles. Metolachlor and atrazine are two widely used agricultural herbicides that inhibit the growth of pre-emergent vegetation. Residues of these pesticides are commonly found in water bodies near agricultural areas. In our first experiment in the laboratory, we examined changes in survivorship when free-living trematode cercariae were exposed to a low concentration (10 ppb: 15 ppb) and high concentration (85 ppb: 100 ppb) mixture of metolachlor and atrazine, respectively. These exposure levels were chosen to represent the higher end of levels that have been documented in aquatic systems. There was a significant decline in cercarial survivorship in the high concentration treatment at 14 hours. In our second experiment, we exposed the parasites, the second intermediate host tadpoles, or both the parasites and the tadpoles, to the pesticide mixtures for a maximum of 10 hours prior to infection and examined subsequent tadpole infection levels. The atrazine and metolachlor mixtures had no significant effects on parasite load, although newly shed cercariae were more likely than 10-hour-old cercariae to infect tadpoles. In our final experiment, we utilized outdoor mesocosms to expose parasites, infected snail hosts, and Rana sylvatica tadpoles to the pesticide mixtures for two weeks and examined differences in tadpole parasite loads. The pesticides had no significant effect on tadpole parasite loads in the mesocosms. Overall, our findings suggest that atrazine and metolachlor mixtures at the doses we examined do not significantly alter the short-term dynamics of Echinostoma trivolvis infection in aquatic systems.

Direct and indirect effects of the herbicides Glyphosate, Bentazone and MCPA on eelgrass ( Zostera marina)

Eelgrass beds are important habitats for many organisms, but there has been a decline in the area covered by eelgrass during the last decades due to increased eutrophication resulting in increased shading from phytoplankton. The use of herbicides in terrestrial agriculture has also increased over the last century, and while the effects of herbicides on non-target organisms have been well studied in freshwater they are overlooked in coastal waters. It is not known if herbicides have any effect on the distribution of eelgrass ( Zostera marina), or how natural phytoplankton communities respond to the same herbicides. Direct and indirect effects of the herbicides Glyphosate, Bentazone and MCPA both as single toxicants and as mixtures, on the eelgrass plants were investigated in this study. The direct effects on eelgrass were examined by measuring the four different endpoints; the relatively growth rate as length and weight, the chlorophyll a and b ratio, as well as the RNA–DNA ratio, at the end of a 3 days exposure period. The indirect effect was investigated by measuring the effect on a natural phytoplankton production from Roskilde Fjord six times during 1 year. The results showed that the chlorophyll a– b and RNA–DNA ratios were the most sensitive endpoints in single herbicide experiments. The effects of herbicide mixtures on eelgrass were much larger compared to the single substances. Nearly a halving was found for both the relatively growth rate in length and weight, and the RNA–DNA as well as the chlorophyll a– b ratios were also significant reduced. This indicates a possible synergistic effect, and calculations based on the concentration addition model indicate that the low concentrations mixture has a synergistic effect, whereas the high concentration mixture has an antagonistic effect on eelgrass ( Z. marina). The low concentrations mixture is the one with the highest relevance for coastal areas. The effect on phytoplankton showed some variation over the year but mainly in a stimulation in primary production. This means that herbicides affect eelgrass both directly and indirectly.

Hydrogen bonding and the cryoprotective properties of glycerol/water mixtures.

Molecular dynamics simulations and infrared spectroscopy were used to determine the hydrogen bond patterns of glycerol and its mixtures with water. The ability of glycerol/water mixtures to inhibit ice crystallization is linked to the concentration of glycerol and the hydrogen bonding patterns formed by these solutions. At low glycerol concentrations, sufficient amounts of bulk-like water exist, and at low temperature, these solutions demonstrate crystallization. As the glycerol concentration is increased, the bulk-like water pool is eventually depleted. Water in the first hydration shell becomes concentrated around the polar groups of glycerol, and the alkyl groups of glycerol self-associate. Glycerol-glycerol hydrogen bonds become the dominant interaction in the first hydration shell, and the percolation nature of the water network is disturbed. At glycerol concentrations beyond this point, glycerol/water mixtures remain glassy at low temperatures and the glycerol-water hydrogen bond favors a more linear arrangement. High glycerol concentration mixtures mimic the strong hydrogen bonding pattern seen in ice, yet crystallization does not occur. Hydrogen bond patterns are discussed in terms of hydrogen bond angle distributions and average hydrogen bond number. Shift in infrared frequency of related stretch and bend modes is also reviewed.

Separation of isomaltose from high sugar concentrated enzyme reaction mixture by dealuminated β-zeolite

The adsorption of isomaltose from high sugar concentrated reaction mixture was systematically investigated using static experiments. The isotherm data for the single-components glucose, fructose, and isomaltose fit the Langmuir adsorption model well. The product isomaltose has much more affinity for the zeolite than the other carbohydrates, which allows in situ separation process. Isomaltose is separated in situ from the enzyme reaction mixture by dealuminated β-zeolites (Si/Al=75) to avoid further reactions involving it.

Toxicity of Chemical Components of Fine Particles Inhaled by Aged Rats: Effects of Concentration

This study tested the hypothesis that exposure to mixtures containing fine particles and ozone (O3) would cause pulmonary injury and decrements in functions of immunological cells in exposed rats (22–24 months old) in a dose-dependent manner. Rats were exposed to high and low concentrations of ammonium bisulfate and elemental carbon and to 0.2 ppm O3. Control groups were exposed to purified air or O3 alone. The biological end points measured included histopathological markers of lung injury, bronchoalveolar lung fluid proteins, and measures of the function of the lung’s innate immuno-logical defenses (macrophage antigen-directed phagocytosis and respiratory burst activity). Exposure to O3 alone at 0.2 ppm did not result in significant changes in any of the measured end points. Exposures to the particle mixtures plus O3 produced statistically significant changes consistent with adverse effects. The low-concentration mixture produced effects that were statistically significant compared to purified air but, with the exception of macrophage Fc receptor binding, exposure to the high-concentration mixture did not. The effects of the low- and high-concentration mixtures were not significantly different. The study supports previous work that indicated that particle + O3 mixtures were more toxic than O3 alone.

High Concentration Aqueous Mixtures of Single Walled Nanotubes

AbstractGum arabic (GA) and polyvinylpyrrolidone (PVP) were used to stabilize relatively high concentration mixtures of single walled carbon nanotubes (SWNTs) in water. Viscosity and electrical conductivity data, along with electron microscopy, suggest that PVP interacts much more strongly with nanotubes than GA does. This strong PVP-SWNT relationship results in better dispersion of the nanotubes, resulting in lower electrical conductivity, but may enhance mechanical behavior in polymer-matrix composites.

Origin of widespread, exceptionally thick basaltic phreatomagmatic tuff breccia in the Middle Jurassic Prebble and Mawson Formations, Antarctica

Eruption of the Middle Jurassic Kirkpatrick Basalt flood lavas of Antarctica was preceded by a significant episode of basaltic pyroclastic activity. The resulting deposits include minor tuff and lapilli tuff of base-surge and fall origin, but consist dominantly of massive, poorly sorted tuff breccia in beds up to 170m thick, which form unbroken successions as much as 370m thick. Tuff breccia consists of clasts of igneous and sedimentary rock up to several meters long plus basaltic bombs and spatter (≤1m) dispersed in an ash-and lapilli-size matrix of basaltic pyroclasts and abundant, disaggregated sedimentary debris. Pyroclast characteristics indicate production by phreatomagmatic processes. Sedimentary particles were produced by explosive disruption of underlying strata; some clasts were derived from depths >1km. Tuff-breccia deposits are attributed to eruption as high concentration mixtures of basaltic tephra, accidental sedimentary debris and water; the ensuing lahars filled valleys and low-standing areas within a tectono-magmatic rift zone associated with Gondwana break-up.

INTERACTION OF ASTRINGENCY AND TASTE CHARACTERISTICS1

ABSTRACTThe perception of astringency and basic taste in mixtures and their interaction effects were investigated by two procedures. In Experiment 1, focused and nonfocused testing procedures were compared using mixtures of low and high concentrations of alum and basic taste solutions. Both procedures yielded taste and astringency intensities that were modality‐dependent. Nonfocused testing was used in Experiment 2 to investigate the interactions of astringent phenolic (tannic acid) and nonphenolic (alum) compounds with each basic taste. Sweetness of sucrose increased with increased concentration with or without alum or tannin present. Changes in salty, bitter, and sour taste intensities were modality‐dependent. Astringency either remained unchanged or decreased with the addition of sucrose, sodium chloride, citric acid, or caffeine depending upon the taste concentration. Bitterness of tannin and alum at high concentrations was suppressed by the addition of sucrose, sodium chloride, or citric acid; sourness also decreased in the presence of sucrose or sodium chloride as well as a high level of caffeine.