Calcium hydroxide root canal sealers: Evaluation of pH, calcium ion concentration and conductivity

The calcium hydroxide ionization of four root canal sealers (Sealapex, CRCS, Sealer 26, and Apexit) was studied by measuring conductivity and pH and by conducting atomic absorption spectrophotometry. Samples 6 mm in diameter and 15 mm long were prepared from these sealers. After setting and 48 h storage in a desiccator, five samples of each material were placed in 50 mL distilled water and analysed after 0,1,2,4, 6 and 24 h and 5, 15 and 30 days. The results showed that Sealapex was the root canal sealer showing the highest pH, ionic calcium and total calcium values (P<0.05) throughout the experimental period, followed by CRCS, Apexit and Sealer 26.

Photosynthetic performance of freshwater Rhodophyta in response to temperature, irradiance, pH and diurnal rhythm

Responses of net photosynthetic rates to temperature, irradiance, pH/inorganic carbon and diurnal rhythm were analyzed in 15 populations of eight freshwater red algal species in culture and natural conditions. Photosynthetic rates were determined by oxygen concentration using the light and dark bottles technique. Parameters derived from the photosynthesis-irradiance curves indicated adaptation to low irradiance for all freshwater red algae tested, confirming that they tend to occur under low light regimes. Some degree of photoinhibition (β = -0.33-0.01 mg O2 g-1 DW h-1 (μmol photons m-2 s-1)-1) was found for all species/populations analyzed, whereas light compensation points (lc) were very low (≤ 2 μmol photons m- photons s-1) for most algae tested. Saturation points were low for all algae tested (lk = 6-54 μmol photons m-2 S-1; lS = 20-170 μmol photons m-2 s-1). Rates of net photosynthesis and dark respiration responded to the variation in temperature. Optimum temperature values for net photosynthesis were variable among species and populations so that best performances were observed under distinct temperature conditions (10, 15, 20 or 25°C). Rates of dark respiration exhibited an increasing trend with temperature, with highest values under 20-25°C. Results from pH experiments showed best photosynthetic performances under pH 8.5 or 6.5 for all but one species, indicating higher affinity for inorganic carbon as bicarbonate or indistinct use of bicarbonate and free carbon dioxide. Diurnal changes in photosynthetic rates revealed a general pattern for all algae tested, which was characterized by two relatively clear peaks, with some variations around it: a first (higher) during the morning (07.00-11.00 hours.) and a second (lower) in the afternoon (14.00-18.00 hours). Comparative data between the 'Chantransia' stage and the respective gametophyte for one Batrachospermum population revealed higher values (ca 2-times) in the latter, much lower than previously reported. The physiological role of the 'Chantransia' stage needs to be better analyzed.

Elevation of boiling point of coffee extract

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Participation of the deltoid (anterior portion) and pectoralis major (clavicular portion) muscles in different modalities of supine and frontal elevation exercises with different grips

The muscles deltoid-anterior portion (DA) and pectoralis major-clavicular portion (PMC) were analysed to establish the muscular behavior and intensity patterns, as well to evaluate the connected participation of these muscles during supine and frontal elevation exercises. Twenty-four male volunteers were examined using a 2-channel TECA TE4 electromyograph and Hewlett Packard surface electrodes. Our results showed low levels of activity to PMC in frontal elevation exercises, whereas to DA the levels were very high. In the supine exercise, the action potential levels developed by the PMC were always lower than those presented by DA, however, with action simultaneity. Some suggestions to the use of the tested exercises are presented.

Larval development of the giant river prawn Macrobrachium rosenbergii at different ammonia concentrations and pH values

The effect of ammonia and pH levels on giant river prawn Macrobrachium rosenbergii larvae were evaluated to provide science-based information on safe levels of ammonia and pH for larviculture. Survival rate, developmental stage, and larval weight gain were determined for larvae kept in water with total ammonia (NH4-N) concentrations of 0, 1, 2, 4, and 8 mg\L and pH 7, 8, and 9. The trials were conducted in two phases: phase 1, larvae from stages I through VIII and phase 2, larvae from stage VIII until metamorphose. Oxygen consumption was determined for larvae in stages I and VIII at total ammonia concentrations of 0, 4, and 8 mg/L and pH 8. Survival rate up to stage VIII varied from 86 to 98% and did not differ for total ammonia concentrations in pH 7 and 8 and for 0 mg/L NH4-N in pH 9. Survival rate was significantly lower (0-20%) for total ammonia concentrations from 1 to 8 mg/L (0.43-3.41 mg/L of unionized ammonia) in pH 9. Larval stage indexes (7.9-8.0 range) and weight gain (1.572-2.931 mg range) of larvae at the end of phase 1 of the experiment did not differ for the different ammonia concentration solutions, but were significantly lower in pH 9. In phase 2, no parameter differed among treatments for pH 7 and 8; however there was total mortality at pH 9 until 96h. Respiration rates diminished when larvae were exposed to total ammonia concentrations of 4 and 8 mg/L (0.28 and 0.55 mg/L of unionized ammonia), but development remained unaltered. Therefore, M. rosenbergii larvae tolerate high levels of total ammonia, while toxicity depends primarily on unionized ammonia concentrations. In addition, alkaline pH (9) acted directly on the larvae, curbing development and causing severe mortality. Larval tolerance to high ammonia and pH levels decreases for the last zoeal stages. © Copyright by the World Aquaculture Society 2005.

A new firefly luciferase with bimodal spectrum: Identification of structural determinants of spectral pH-sensitivity in firefly luciferases

Fireflies emit flashes in the green-yellow region of the spectrum for the purpose of sexual attraction. The bioluminescence color is determined by the luciferases. It is well known that the in vitro bioluminescence color of firefly luciferases can be shifted toward the red by lower pH and higher temperature; for this reason they are classified as pH-sensitive luciferases. However, the mechanism and structural origin of pH sensitivity in fireflies remains unknown. Here we report the cloning of a new luciferase from the Brazilian twilight active firefly Macrolampis sp2, which displays an unusual bimodal spectrum. The recombinant luciferase displays a sensitive spectrum with the peak at 569 nm and a shoulder in the red region. Comparison of the bioluminescence spectra of Macrolampis, Photinus and Cratomorphus firefly luciferases shows that the distinct colors are determined by the ratio between green and red emitters under luciferase influence. Comparison of Macrolampis luciferase with the highly similar North American Photinus pyralis luciferase (91%) showed few substitutions potentially involved with the higher spectral sensitivity in Macrolampis luciferase. Site-directed mutagenesis showed that the natural substitution E354N determines the appearance of the shoulder in the red region of Macrolampis luciferase bioluminescence spectrum, helping to identify important interactions and residues involved in the pH-sensing mechanism in firefly luciferases. © 2005 American Society for Photobiology.

Bone reformation and implant integration following maxillary sinus membrane elevation: An experimental study in primates

Background: Recent clinical studies have described maxillary sinus floor augmentation by simply elevating the maxillary sinus membrane without the use of adjunctive grafting materials. Purpose: This experimental study aimed at comparing the histologic outcomes of sinus membrane elevation and simultaneous placement of implants with and without adjunctive autogenous bone grafts. The purpose was also to investigate the role played by the implant surface in osseointegration under such circumstances. Materials and Methods: Four tufted capuchin primates had all upper premolars and the first molar extracted bilaterally. Four months later, the animals underwent maxillary sinus membrane elevation surgery using a replaceable bone window technique. The schneiderian membrane was kept elevated by insertion of two implants (turned and oxidized, Brånemark System®, Nobel Biocare AB, Göteborg, Sweden) in both sinuses. The right sinus was left with no additional treatment, whereas the left sinus was filled with autogenous bone graft. Implant stability was assessed through resonance frequency analysis (Osstell™, Integration Diagnostics AB, Göteborg, Sweden) at installation and at sacrifice. The pattern of bone formation in the experimental sites and related to the different implant surfaces was investigated using fluorochromes. The animals were sacrificed 6 months after the maxillary sinus floor augmentation procedure for histology and histomorphometry (bone-implant contact, bone area in threads, and bone area in rectangle). Results: The results showed no differences between membrane-elevated and grafted sites regarding implant stability, bone-implant contacts, and bone area within and outside implant threads. The oxidized implants exhibited improved integration compared with turned ones as higher values of bone-implant contact and bone area within threads were observed. Conclusions: The amount of augmented bone tissue in the maxillary sinus after sinus membrane elevation with or without adjunctive autogenous bone grafts does not differ after 6 months of healing. New bone is frequently deposited in contact with the schneiderian membrane in coagulum-alone sites, indicating the osteoinductive potential of the membrane. Oxidized implants show a stronger bone tissue response than turned implants in sinus floor augmentation procedures. © 2006 Blackwell Publishing, Inc.

Effect of fluoridated varnish and silver diamine fluoride solution on enamel demineralization: pH-cycling study

Objective: In the present investigation, the anticariogenic effect of fluoride released by two products commonly applied in infants was evaluated. Methods: Bovine sound enamel blocks were randomly allocated to each one of the treatment groups: control (C), varnish (V) and diamine silver fluoride solution (D). The blocks were submitted to pH cycles in an oven at 37°C. Next, surface and cross-sectional microhardness were assessed to calculate the percentage loss of surface microhardness (%SML) and the mineral loss (ΔZ). The fluoride present in enamel was also determined. Results: F/Px10 -3 (ANOVA, p<0.05) in the 1 st layer of enamel before pH-cycling were (C, V and D): 1.61 a; 21.59 b and 3.98 c. The %SMH (Kruskal-Wallis, p<0.05) were: -64.0 a, -45.2 b and -53.1 c. %ΔZ values (ANOVA, p<0.05) were: -18.7 a, -7.7 b and -17.3 a. Conclusion: The data suggested that the fluoride released by varnish showed greater interaction with sound enamel and provided less mineral loss when compared with silver diamine solution.

Agronomic effectiveness of cationic phosphate impurities present in superphosphate fertilizers as affected by soil pH

The general concept that low-water-soluble phosphorus (P) fertilizers should be more agronomically effective when applied to acidic soils was developed based on sources containing mainly calcium (Ca)-P compounds, but it may not hold true for sources with different chemical composition. To obtain information related to this issue, two important iron (Fe)-potassium (K)-P compounds present in superphosphates [Fe 3 KH 8 (PO 4 ) 6·6H 2 O, H8, and Fe 3 KH 14 (PO 4 ) 8·4H 2 O, H14] were prepared and characterized. These P sources were used to provide 30 and 60 mg P kg -1 as neutral ammonium citrate (NAC)+H 2 O-soluble P. Reagent-grade monocalcium phosphate (MCP) was used as a standard P source with high water solubility with an additional rate of 120 mg P kg -1 included. Also, mixtures of both Fe-K-P compounds and MCP were prepared to provide 0, 25, 50, 75, and 100% of the total P as MCP. All sources were applied to a clayey loamy acid soil (pH 5.3) classified as Rhodic Kanhapludult. The soil was incubated at two rates (0 and 10 g kg -1 ) of lime, which resulted in pH 5.4 and 6.8. Upland rice was cultivated to maturity. The H14 compound confirmed to be a highly effective source of P for the rice plants at both soil pH, as opposed to the H8, which was poorly effective when applied alone. When mixed with water-soluble P (WSP), the H8 was able to provide P to the plants with the maximum yield of upland rice reached with 54.8 and 80.5% of WSP for pH 5.4 and 6.8, respectively. The high agronomic performance of the H14 compound clearly indicates that this low-water-soluble P source cannot be deemed as ineffective at high soil pH. Copyright © Taylor & Francis Group, LLC.

The electronic detail of a digital pH-meter

This paperwork presents the complete circuitry used to build a microcontroller-based pH-meter. Key control software is also discussed. An industry-standard glass combination electrode has been employed for pH detection. Electrode parameter extraction procedure is presented. Good measurement results, with 1 % error, have been attained. Copyright© (2006) by the International Measurement Federation (IMEKO).

The effect of pH on horseradish peroxidase-catalyzed oxidation of melatonin: Production of N1-acetyl-N2-formyl-5- methoxykynuramine versus radical-mediated degradation

There is a growing body of evidence that melatonin and its oxidation product, N1-acetyl-N2-formyl-5-methoxykynuramine (AFMK), have anti-inflammatory properties. From a nutritional point of view, the discovery of melatonin in plant tissues emphasizes the importance of its relationship with plant peroxidases. Here we found that the pH of the reaction mixture has a profound influence in the reaction rate and products distribution when melatonin is oxidized by the plant enzyme horseradish peroxidase. At pH 5.5, 1 mm of melatonin was almost completely oxidized within 2 min, whereas only about 3% was consumed at pH 7.4. However, the relative yield of AFMK was higher in physiological pH. Radical-mediated oxidation products, including 2-hydroxymelatonin, a dimer of 2-hydroxymelatonin and O-demethylated dimer of melatonin account for the fast consumption of melatonin at pH 5.5. The higher production of AFMK at pH 7.4 was explained by the involvement of compound III of peroxidases as evidenced by spectral studies. On the other hand, the fast oxidative degradation at pH 5.5 was explained by the classic peroxidase cycle. © 2007 The Authors.

The influence of the loop between residues 223-235 in beetle luciferase bioluminescence spectra: A solvent gate for the active site of pH-sensitive luciferases

Beetle luciferases emit a wide range of bioluminescence colors, ranging from green to red. Firefly luciferases can shift the spectrum to red in response to pH and temperature changes, whereas click beetle and railroadworm luciferases do not. Despite many studies on firefly luciferases, the origin of pH-sensitivity is far from being understood. Through comparative site-directed mutagenesis and modeling studies, using the pH-sensitive luciferases (Macrolampis and Cratomorphus distinctus fireflies) and the pH-insensitive luciferases (Pyrearinus termitilluminans, Phrixotrix viviani and Phrixotrix hirtus) cloned by our group, here we show that substitutions dramatically affecting bioluminescence colors in both groups of luciferases are clustered in the loop between residues 223-235 (Photinus pyralis sequence). The substitutions at positions 227, 228 and 229 (P. pyralis sequence) cause dramatic redshift and temporal shift in both groups of luciferases, indicating their involvement in labile interactions. Modeling studies showed that the residues Y227 and N229 are buried in the protein core, fixing the loop to other structural elements participating at the bottom of the luciferin binding site. Changes in pH and temperature (in firefly luciferases), as well as point mutations in this loop, may disrupt the interactions of these structural elements exposing the active site and modulating bioluminescence colors. © 2007 The Authors.

The structural origin and biological function of pH-sensitivity in firefly luciferases

Firefly luciferases are called pH-sensitive because their bioluminescence spectra display a typical red-shift at acidic pH, higher temperatures, and in the presence of heavy metal cations, whereas other beetle luciferases (click beetles and railroadworms) do not, and for this reason they are called pH-insensitive. Despite many studies on firefly luciferases, the origin of pH-sensitivity is far from being understood. This subject is revised in view of recent results. Some substitutions of amino-acid residues influencing pH-sensitivity in firefly luciferases have been identified. Sequence comparison, site-directed mutagenesis and modeling studies have shown a set of residues differing between pH-sensitive and pH-insensitive luciferases which affect bioluminescence colors. Some substitutions dramatically affecting bioluminescence colors in both groups of luciferases are clustered in the loop between residues 223-235 (Photinus pyralis sequence). A network of hydrogen bonds and salt bridges involving the residues N229-S284-E311-R337 was found to be important for affecting bioluminescence colors. It is suggested that these structural elements may affect the benzothiazolyl side of the luciferin-binding site affecting bioluminescence colors. Experimental evidence suggest that the residual red light emission in pH-sensitive luciferases could be a vestige that may have biological importance in some firefly species. Furthermore, the potential utility of pH-sensitivity for intracellular biosensing applications is considered. © The Royal Society of Chemistry and Owner Societies.

Influência das superfícies geomórficas na distribuição espacial dos atributos do solo em área sob cultivo de cana-de-açúcar

Variations in soil attributes occur based on relief forms and parent material. The objective of this research was to study the influences of geomorphic surfaces on the spatial distribution of soil attributes in a sugarcane cultivation area. First, 530,67 hectares were mapped by using a Global Positioning System. Then, a Digital Elevation Model was developed and geomorphic surfaces were identified and delimited, according to topographic and stratigraphic criteria based on detailed field investigations. Soil samples were collected every 7 ha, at 0.0-0.25 m and 0.80-1.00 m depths, totalizing 134 samples. Texture, Ca, K, Mg, SB, CEC, V%, pH, and OMS analyses were carried out as well as descriptive statistics and geostatistics analysis. It was concluded that the geostatistic techniques and digital elevation model helped to notice that soil attributes presented limits close to the geomorphic surfaces ones.

Métodos de interpolação para estimar o ph em solo sob dois manejos de café Arábica

There are many methods used to estimate values in places no sampled for construction of contours maps. The aim of this study was to use the methods of interpolation kriging, inverse of the square of the distance and polynomial in the representation of the spatial variability of the pH of the soil in the organic and conventional management in the culture of the coffee plantation. For that, irregular meshes were built for soil sampling in the depth of 0-0,10 meters, totaling 40 points sampling in each area. For gauging of the interpolation methods they were solitary 10% of the total of points, for each area. Initially, the data were appraised through the classic statistics (descriptive and exploratory) and spatial analysis. The method inverse square of the distance and kriging has low error in estimating dados. The method of kriging presented low variation around the average in different managements.