Hasil untuk "physics.comp-ph"

Xiaoxin Zou, Xiaoxi Huang, A. Goswami et al.

Bradley A. Webb, Michael S. Chimenti, M. Jacobson et al.

D. Neri, C. Supuran

Niels Holten-Andersen, Matthew J. Harrington, H. Birkedal et al.

J. Casey, S. Grinstein, J. Orlowski

Congcong Shen, J. Xiong, Huayong Zhang et al.

J. Rousk, P. Brookes, E. Bååth

Jungmin Lee, R. Durst, R. Wrolstad

D. Schmaljohann

A. Görg, C. Obermaier, G. Boguth et al.

G. W. Thomas

Soil pH is probably the single most informative measurement that can be made to determine soil characteristics. At a single glance, pH tells much more about a soil than merely indicating whether it is acidic or basic. For example, availability of essential nutrients and toxicity of other elements can be estimated because of their known relationship with pH. The term pH was "invented" by the Swedish scientist Sorensen (1909) in order to obtain more convenient numbers and the idea quickly caught on. Gillespie and Hurst (1918) seem to have been among the earliest to determine pH (or PH, as it was then called) electrometrically using a platinum-palladium blackhydrogen gas electrode, a calomel reference electrode and a fairly cumbersome potentiometer and galvanometer system. At that period, it was still much more common to use colorimetric methods with indicator dyes than the electrometric method. This changed rapidly, however. Sharp and Hoagland (1919) used a similar but less involved method than Gillespie and Hurst (1918) and Healy and Karraker (1922) used a commercially available platinum-hydrogen gas electrode, potentiometer and galvanometer which had been designed by Clark (1920). The decade of the 1920s saw the development of the quinhydrone electrode which was less fragile and much less expensive than the hydrogen-platinum electrode. But, it was the development of the glass electrode in the 1930s that brought the determination of pH very rapidly to its present importance and convenience. The Beckman Model G pH meter (circa 1931) was practically indestructible and could be used as a portable as well as a laboratory instrument. Although it was cumbersome by today's standards, it was virtually foolproof (except for the constantly failing batteries) and many are still capable of operating if not actually operating today. As recently as two decades ago, the use of the small, handheld portable pH meters then available to determine pH in the field was a very imprecise and hazardous undertaking because both electrodes and meters were subject to sudden failures but this has changed rather abruptly in the last few years. Microcircuitry and plastic have contributed to rugged pH meters and electrodes that withstand

K. Caldeira, M. Wickett, P. Duffy et al.

N. Tanner, Yinhua Zhang, T. C. Evans

Nucleic acid amplification is the basis for many molecular diagnostic assays. In these cases, the amplification product must be detected and analyzed, typically requiring extended workflow time, sophisticated equipment, or both. Here we present a novel method of amplification detection that harnesses the pH change resulting from amplification reactions performed with minimal buffering capacity. In loop-mediated isothermal amplification (LAMP) reactions, we achieved rapid (<30 min) and sensitive (<10 copies) visual detection using pH-sensitive dyes. Additionally, the detection can be performed in real time, enabling high-throughput or quantitative applications. We also demonstrate this visual detection for another isothermal amplification method (strand-displacement amplification), PCR, and reverse transcription LAMP (RT-LAMP) detection of RNA. The colorimetric detection of amplification presented here represents a generally applicable approach for visual detection of nucleic acid amplification, enabling molecular diagnostic tests to be analyzed immediately without the need for specialized and expensive instrumentation.

Xin Pang, Yue Jiang, Qicai Xiao et al.

A. Behnood, K. Tittelboom, N. Belie

A. Tamayol, M. Akbari, Y. Zilberman et al.

Yang Zhao, Wei Ren, Ting Zhong et al.

Randeep Singh, P. Mondal, M. Purkait

Mostafa M. S. Ismaiel, Y. El-Ayouty, M. Piercey-Normore

Algae can tolerate a broad range of growing conditions but extreme conditions may lead to the generation of highly dangerous reactive oxygen species (ROS), which may cause the deterioration of cell metabolism and damage cellular components. The antioxidants produced by algae alleviate the harmful effects of ROS. While the enhancement of antioxidant production in blue green algae under stress has been reported, the antioxidant response to changes in pH levels requires further investigation. This study presents the effect of pH changes on the antioxidant activity and productivity of the blue green alga Spirulina (Arthrospira) platensis. The algal dry weight (DW) was greatly enhanced at pH 9.0. The highest content of chlorophyll a and carotenoids (10.6 and 2.4 mg/g DW, respectively) was recorded at pH 8.5. The highest phenolic content (12.1 mg gallic acid equivalent (GAE)/g DW) was recorded at pH 9.5. The maximum production of total phycobiliprotein (159 mg/g DW) was obtained at pH 9.0. The antioxidant activities of radical scavenging activity, reducing power and chelating activity were highest at pH 9.0 with an increase of 567, 250 and 206% compared to the positive control, respectively. Variation in the activity of the antioxidant enzymes superoxide dismutase (SOD), catalase (CAT) and peroxidase (POD) was also reported. While the high alkaline pH may favor the overproduction of antioxidants, normal cell metabolism and membrane function is unaffected, as shown by growth and chlorophyll content, which suggests that these conditions are suitable for further studies on the harvest of antioxidants from S. platensis.

S. Oshunsanya

Soil pH is a master variable in soils because it controls many chemical and biochemical processes operating within the soil. It is a measure of the acidity or alkalinity of a soil. The study of soil pH is very important in agriculture due to the fact that soil pH regulates plant nutrient availability by controlling the chemical forms of the different nutrients and also influences their chemical reactions. As a result, soil and crop productivities are linked to soil pH value. Though soil pH generally ranges from 1 to 14, the optimum range for most agricultural crops is between 5.5 and 7.5. However, some crops have adapted to thrive at soil pH values outside this optimum range. The United States Department of Agricultural National Resources Conservation Service groups soil pH values as follows: ultra acidic (9.0) [1].