328,867 research outputs found
Physiological adaptation of two unicellular green algae to pH stress.
Full text linkTwo marine algae, Dunaliella parva and Chlorococcum submarinum were selected to study the effect of pH stress on single celled algae. D. parva has been well characterised physiologically, but not with regards to pH stress. C submarinum has not been so extensively studied, but is known to grow over a wide pH range from pH 4.5 to 10.5. It was of prime importance that the algal cells were grown at the desired extreme values of external pH. Problems were encountered at high levels of pH but were overcome by growing the algae in a fermenter set up as a batch culture. This method of growth was used for both algae at extreme values of external pH and it allowed the accurate control of the media pH by the automatic addition of acid or alkali. pH 7.5 cells were grown in normal flask batch culture. The cell number, cell volume, and chlorophyll content of both algae were determined over a wide range of pH values, showing that differences in external pH had significant effects on individual cells. Protein concentrations were measured and were shown to increase in pH 9.0 grown cells. Determination of cell volume, internal pH and membrane potential have been carried out using radiolabelled isotopes for algae grown over a wide pH range. Cell volume was shown to increase at both acid and alkaline pH values. The internal pH of both algae was found to be at a more neutral pH than the external pH. For both D. parva and C submarinum, the membrane potential increased with increasing external pH. Enzyme activities in crude extracts were measured to establish the effects of external pH changes on metabolic pathways. The activity of these enzymes, taken from different organelles in the cell, was used to investigate the uniformity of internal pH
Measurement of the D+/- production asymmetry in 7 TeV pp collisions
Full text linkThe asymmetry in the production cross-section \sigma of D+/- mesons, A_P = (\sigma(D+) - \sigma(D-))/(\sigma(D+) + \sigma(D-)), is measured in bins of pseudorapidity \eta and transverse momentum p_T within the acceptance of the LHCb detector. The result is obtained with a sample of D+ -> K_S pi+ decays corresponding to an integrated luminosity of 1.0 fb^-1, collected in pp collisions at a centre of mass energy of 7 TeV at the Large Hadron Collider. When integrated over the kinematic range 2.0 K_S pi+ decay is negligible. No significant dependence on \eta or p_T is observed
Ageing of PLS glass: study of the alteration phenomena
No full textThe wood based glass (PLS, Potash-Lime-Silica), employed for medieval cathedral windows in Northern Europe since 1000 A.D., in particularly sensitive to the alteration phenomena. Three PLS medieval-like glasses were produced with different K2O contents and characterized by Ft-IR and Raman spectroscopy. Ageing experiments were carried out by sulfuric acid and water, checking, in this last case, the pH over time. The woight loss and the alteration layer thickenss were measured and the interacting solutions were analyzed through AAS. Raman maps were recorded on the altered glass cross sections. Changes in the glass network structure were observed and the presence of neo-formation products was determined
Panorama vom Bodensee : von Lindau bis Rorschach : gezeichnet auf dem Hoyerberg bei Lindau
No full textN. d. Nat. gez. von Ph. Poeppel ; [Jean] Jacottet lith.KreidelithographiePanorama, unten, rechts: "Lindau bei J. Th. Stettner
Photonic porous silicon as a pH sensor
Full text linkChronic wounds do not heal within 3 months, and during the lengthy healing process, the wound is invariably exposed to bacteria, which can colonize the wound bed and form biofilms. This alters the wound metabolism and brings about a change of pH. In this work, porous silicon photonic films were coated with the pH-responsive polymer poly(2-diethylaminoethyl acrylate). We demonstrated that the pH-responsive polymer deposited on the surface of the photonic film acts as a barrier to prevent water from penetrating inside the porous matrix at neutral pH. Moreover, the device demonstrated optical pH sensing capability visible by the unaided eye
MMP2 and Aquaporin, Whole Saliva pH and Treatment Needs
Full text linkObjectives: Salivary pH ranges from 6.2 to 7.4 and is kept near neutrality. We hypothesized that within the normal physiological limits of the saliva some people tend to show more susceptibility/ resistance towards dental conditions. We also hypothesized that genetics play a role in controlling the saliva pH of the mouth and individuals within a certain range of this pH variation may show more extensive and customized dental treatment needs due to difference in their oral environment pertaining to differences in the genetic makeup of all individuals. This can be the explanation of why some individuals are more or less susceptible to dental diseases. We investigated the potential association between saliva pH and various treatment needs with MMP2 and the aquaporin locus.
Methods: Clinical data and saliva samples were obtained from the University of Pittsburgh Dental Registry and DNA Repository project. Analysis was performed by querying the medical and dental records of more than 6000 patients. A total of 189 patients were selected with almost equal number of males and females and assessed for their saliva pH values. pH was determined by the use of commercial strips. Some patients required stimulation to provide a saliva sample and it was done by the use of gum or candy to stimulate salivary secretion. Sex and ethnicity were also considered. Subjects were divided in two groups based on the pH of their saliva (above or below the mean pH of all subjects). Information was retrieved on positive/negative history for
hypertension, oral surgery treatment (as a surrogate for tooth loss), periodontitis, restorative treatment, and root canal therapy. Genetic association studies were also performed and the markers rs2241145, rs243865, rs243832, rs2285053, rs1163960 in MMP2 and the marker rs461872 in the aquaporin locus were genotyped using TaqMan chemistry and end-point analysis. Chi-square and Fisher’s exact tests were used in all comparisons with an alpha of 0.05.
Results: Out of the 189 subjects, 95 patients provided a saliva sample without the need for stimulation, 97 subjects were females, and 23 were African descendants. The mean pH of the saliva in all study participants was 7.16. We observed statistically significant differences in the distribution of saliva pH for the following genetic markers and phenotypes:
a. Periodontitis associated with rs11639960 and rs2285053.
b. Restorative treatment associated with rs243865, rs11639960, and rs2285053
c. Oral surgery treatment associated with rs11639960, rs2285053, rs243832, and rs461872
d. Root canal therapy associated with rs243865, rs11639960, rs11639960 and rs461872
e. Hypertension associated with rs243865 rs11639960, rs11639960, rs2285053, rs2241145 and rs461872
Conclusion: Our findings suggest that markers in MMP2 and the aquaporin locus associate with specific dental and systemic conditions within a particular range of the expected normal salivary pH. These findings could help us predict dental treatment needs of individuals considering genotyping of markers in MMP2 and the aquaporin locus
D-, L- and D,L-Tryptophan-Based Polyamidoamino Acids: pH-Dependent Structuring and Fluorescent Properties
Full text linkChiral polyamidoamino acids were obtained by polyaddition of N,N’methylenebisacrylamide with D-, D,L- and L-tryptophan (M-D-Trp, M-D,L-Trp and M-L-Trp). L-tryptophan/glycine copolymers, M-G-L-Trp5, M-G-L-Trp10, M-G-L-Trp20 and M-G-L-Trp40, were prepared from L-tryptophan/glycine mixtures. These polymers were amphoteric, with acid-base properties similar to those of the parent amino acids. The L-tryptophan/glycine copolymers with high glycine content were water soluble in the
pH range 2-12. M-G-L-Trp40 showed a solubility gap centred at pH 4.5 and all tryptophan homopolymers were soluble only at pH > 7. Dynamic light scattering measurements performed in their solubility ranges, namely 2-11 M-G-L-Trp5, M-G-L-Trp10 and M-G-L-Trp20 and 7-11 for M-G-L-Trp40, M-D-Trp, M-L-Trp and M-D,L-Trp, showed that the size of all samples did not significantly vary with pH. Both M-L-Trp and M-G-L-Trp copolymers showed pH-dependent circular dichroism spectra in the wavelength interval 200–280 nm, revealing structuring. All samples were fluorescent. Their emission spectra were unstructured and, if normalized for their tryptophan content, almost superimposable at the same pH, providing evidence that only tryptophan governed the photoluminescence properties. Changing pH induced in all cases a slight shift of the emission wavelength maximum ascribed to the modification of the microenvironment surrounding the indole ring induced by different protonation degrees
Concept and development of an autonomous wearable micro-fluidic platform for real time pH sweat analysis
Full text linkIn this work the development of an autonomous, robust and wearable micro-fluidic platform capable of performing on-line analysis of pH in sweat is discussed. Through the means of an optical detection system based on a surface mount light emitting diode (SMD LED) and a light photo sensor as a detector, a wearable system was achieved in which real-time monitoring of sweat pH was performed during 55 minutes of cycling activity. We have shown how through systems engineering, integrating miniaturised electrical components, and by improving the micro-fluidic chip characteristics, the wearability, reliability and performance of the micro-fluidic platform was significantly improved
Control of mineral scaling in power plant recirculating cooling systems using treated municipal wastewater
Full text linkThe global energy demand is projected to increase by 77% from 2006 to 2030 along with a projected 38% increase in freshwater withdrawal for cooling in power industry. Finding alternative sources of water for cooling has become essential for future energy generation in thermoelectric power plants because of water scarcity in many parts of the US. Treated municipal wastewater is considered as one of the most promising alternative water sources because of its geographic distribution and abundant quantity. However, its impaired water quality makes the cooling tower management more challenging. Therefore, effective approaches are required to prevent scaling, corrosion, and biological growth to promote the reuse of treated municipal wastewater as cooling water in power plants.
This study focuses on understanding mineral scale formation and developing effective mitigation methods when using tertiary treated municipal wastewater as power plant cooling makeup. Two types of tertiary-treated municipal wastewater that were evaluated included secondary-treated water with pH adjustment (MWW_pH) and water from secondary-treatment followed by nitrification and sand filtration (MWW_NF). Laboratory-scale studies and pilot-scale cooling systems were used to evaluate mineral scaling formation and inhibition on non-heated surfaces (e.g., pipelines, tower packing, etc.) under conditions relevant to full-scale cooling systems. Results showed that pH adjustment to 7.8 plus the addition of 5 ppm polymaleic acid (PMA) could reduce the scaling significantly with MWW_pH. MWW_NF exhibited little scaling potential, which is related in part to the lower pH and alkalinity in this water. Amorphous calcium phosphate (ACP) was the primary form of mineral scale on non-heated surface with the above two-types of tertiary-treated municipal wastewater.
A bench-scale experimental system was designed to simulate the condenser surface to study the impacts of mineral scaling on the heated surfaces and the effectiveness of proposed scaling control strategies under these conditions. Heated surface favored the formation of hydroxyapatite (HAP), the most thermodynamically stable calcium phosphate, was the main reason for the crystalline fouling with MWW_pH at pH 7.8. 10 ppm PMA addition could suppress the crystalline fouling of MWW_pH at 7.8 to a low level by inhibiting the transformation of amorphous calcium phosphate to hydroxyapatite during the test period. Significant crystalline fouling was identified with MWW_NF at pH 7.2 while pH adjustment to 7.8 resulted in negligible fouling.
The impact of flow velocity on particle deposition was analyzed in a quantitative model, showing positive deposition potential for bulk precipitates at flow velocity of 0.5 and 0.4 m/s while little particulate fouling was theoretically predicted at 0.6 m/s in the test situation. Bench-scale studies were consistent the model prediction, confirming that the model could be used to identify optimal hydrodynamic conditions to control depositions of bulk precipitates.
The mechanism of calcium phosphate scale control by common antiscalants included PMA and 1-hydroxyethane 1,1-diphosphonic acid (HEDP) was elucidated to provide scientific background for the effective scaling mitigation when treated municipal wastewater is used as make-up in thermoelectric power plant cooling systems. Both PMA and HEDP inhibited the transformation of ACP to HAP by preventing the aggregation of ACP particles. However, PMA dispersed the ACP particles mainly through electrostatic repulsive force while hydration force was hypothesized to be the reason for the function of HEDP in dispersion.
The key findings of this study indicate that it is possible to control mineral scaling through direct chemical addition at proper operating conditions when treated municipal wastewater is used as makeup water in the recirculating cooling system. This study not only evaluated scaling control methods in cooling systems, but also revealed the fundamentals of scaling formation and inhibition
Metal ion and pH Sensors based on Carbon Nanotubes
Full text linkThe sensitive and selective detection of metal ions and pH levels is important in environmental and biomedical applications. Conventional methods are limited in their potential due to high cost, big size, and lack of portability. A new system incorporating single-walled carbon nanotubes (SWNTs) modified with polymers or proteins has been developed to create a cost-effective, easy-to-use metal ion/pH sensing platform. This system utilized SWNTs modified with metal ion/pH sensitive materials because pristine SWNTs are only sensitive to high concentrations of metal ions (> 1 mM), and strong base (pH > 12) or acid (pH < 2), and lack selectivity as well.
This work uses noncovalent functionalization approaches to chemically modify SWNTs because noncovalent modifications do not disrupt SWNT electronic properties. When the modified-SWNT system encounters metal ions or pH solutions, the alteration in modified layers, such as conformational change or charge transfer, initiates signal transduction processes, thus changing the electrical and optical properties of the underlying SWNTs. The properties of modified SWNTs were characterized by a variety of techniques including optical spectroscopy, and electrical transport measurements in solid state or liquid state, through which the transduction mechanism of the system was investigated.
The modified SWNT-based metal ion/pH sensors offer promise in applications and provide a platform for fundamental understanding of the transduction mechanism that help us to develop better chemical sensors in the future
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