PEMC sensor's mass change sensitivity is 20 pg/Hz under liquid immersion

To enhance the mass change sensitivity of the resonating piezoelectric-excited millimeter-sized cantilever (PEMC) sensors, we reduced its length and eliminated one layer of its composite structure. As a result the mass sensitivity of the second flexural mode increased by two orders of magnitude (from 10(-9) to 10(-11)g/Hz) and the resonant frequency increased by more than 5 kHz. We demonstrate the effects of modification by detecting a model pathogen Group A Streptococcus (GAS) at 700 cells/mL. The resonant frequency change of the second mode at concentrations of 700, 7 x 10(3), 7 x 10(5), 7 x 10(6), 7 x 10(7), and 7 x 10(9)cells/mL resulted in, respectively, 3.1+/-0.5, 11.6+/-1, 15.7+/-1, 25.7+/-0.15, 28.5+/-2, and 40.5+/-3 ng (n=3 for all) of pathogen attachment. A kinetic model for the binding is proposed and verified. The observed binding rate constant was found to be in the range of 0.051-0.166 min(-1). The significance of the results we report is that the modified PEMC sensors have high mass sensitivity that pathogens can be detected at very low concentration under liquid immersion conditions.     

Relationship between nutrient availability and content of nitrogen and phosphorus in tissues of the aquatic macrophyte,Eichornia Crassipes (Mart.) Solms

Summary Samples of Eichornia crassipes (MART.) SOLMS were collected from the New Braunfels to Gonzales reach of the Guadalupe River, Texas. Plants were also cultured in the laboratory in media containing varying amounts of nitrate and phosphate.The nitrogen and phosphorus content of the blades, floats, and roots of the plants was determined and the values were compared with the nitrogen and phosphorus content of the water in which they were growing.The data show a positive correlation between the nitrogen and phosphorus content of the waterhyacinth tissues and the nitrogen and phosphorus content of the environment. Values obtained on plants cultured in the laboratory suggest that luxury nitrogen and phosphorus may be stored in the floats.Results reported here support the suggestion that the technique of tissue analysis has considerable potential for assaying the nutrient status of lakes and streams.

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Zusammenfassung Eichornia crassipes (MART.) Solms wurde in dem Guadalupe in der Gegend von New Braunfels und Gonsalez gesammelt. Einige Pflanzen wurden auch im Labor in verschiedenen Nitrat- und Phosphatkonzentrationen gezogen.Der Nitrat- und Phosphatgehalt der Blatter, Schwimmblasen und Wurzeln wurde festgestellt und mit der Nitrat- und Phosphatkonzentration des Wassers verglichen.Die Ergebnisse weisen auf ein positives Korrelat zwischen dem Nitrat- und Phosphatgehalt der Wasserhyacinthe und dem des Wassers hin. Resultate von Laborpflanzen deuten auf eine mögliche Speicherung der überflüssigen Nitrate und Phosphate in den Schwimmblasen.Die Ergebnisse schlagen vor, Bass die Technik der Gewebeanalyse beträchtliche Möglichkeiten hat, die Nahrhaftigkeit von Seen und Flüssen zu untersuchen.

     

The genus Pyrus L. (Rosaceae) in south-west Europe and North Afkica

A multivariate morphometric study of the genus Pyrus in south-west Europe and North Africa shows that five species may be recognized in the area: P. bourgaeana Decne., P. communis L., P. cordata Dew., P. spinosa Forssk, and P. nivalis Jacq. Some valuable characters for identification of these species are proposed. In particular the width of fruit peduncle, petal size, leaf width and petiole length served to discriminate the taxa. Several names such as P. gharbiona Trab., P. cossonii Rehder (|M= P. longipes Balansa ex Coss. & Durieu) and P. boisseriana Buhse, are regarded as synonyms of P. cordata , while P. marnormis Trab. of P. bourgaeana. Consequently a check-list and a key to these species are provided.     

Modeling alkali consumption and digestibility improvement from alkaline treatment of wheat straw

The alkali consumption during alkaline treatment of wheat straw at ambient temperature was measured as a function of time, solids concentration, and alkali concentration. The maximum measured alkali consumption was 5.5 g NaOH/100 g TS over a period of 30 days of treatment. Chemical functional groups (e.g., acyl and carboxyl groups) were measured and compared with the observed alkali consumption. The kinetics of alkali consumption were studied and a model was developed which predicts alkali consumption reasonably well. Use of this model was made to predict biodegradability of alkali-treated wheat straw, since a strong correlation was found to exist between alkali consumption and observed biodegradability. The method of bioconversion used was anaerobic digestion for methane production.