Staphylococcus aureus is one of the most important human pathogens, causing more than 500,000 infections in the United States each year. Traditional methods for bacterial culture and identification take several days, wasting precious time for patients who are suffering severe bacterial infections. Numerous nucleic acid-based detection methods have been introduced to address this deficiency; however, the costs and requirement for expensive equipment may limit the widespread use of such technologies. Thus, there is an unmet demand of new platform technology to improve the bacterial detection and identification in clinical practice. In this study, we developed a rapid, ultra-sensitive, low cost, and non-polymerase chain reaction (PCR)-based method for bacterial identification. Using this method, which measures the resonance light-scattering signal of aptamer-conjugated gold nanoparticles, we successfully detected single S. aureus cell within 1.5 hours. This new platform technology may have potential to develop a rapid and sensitive bacterial testing at point-of-care.

The light-use efficiency (LUE) of a mature Canadian Douglas-fir forest (DF49) was studied using high-resolution in situ temporal, spatial, and spectral measurements in conjunction with fluxes acquired from an instrumented tower. We examined the photochemical reflectance index (PRI), a spectral index responsive to high light conditions that alters reflectance at 531 nm, in combination with several alternative reference bands at 551, 570, and 488 nm. These indices were derived from directional reflectance spectra acquired by a hyperspectral radiometer system mounted on the DF49 tower, viewing the canopy through almost 360°rotations multiple times an hour daily throughout the 2006 growing season. From canopy structure information, three foliage sectors within the canopy were delineated according to instantaneous illumination conditions (sunlit, shaded, and mixed shaded-sunlit). On sunny days, the PRI indices for the sunlit foliage sector captured high light-induced stress responses, expressed as significantly different PRI values for sunlit versus shaded foliage. This difference was not observed on highly diffuse or overcast days. PRIs on sunny days tracked the diurnal photoregulation responses throughout the growing season in concert with illumination intensity. We computed the effective instantaneous LUE for the three foliage groups (LUE foliage ) using modeled and measured information. We provide convincing evidence that LUE foliage can be well described and strongly related to all variations of the PRI within this coniferous forest under relatively clear skies (0.59 > r 2 > 0.80, P < 0.0001). LUE foliage varied through the growing season between 0.015 and 0.075 μmol C μmol -1 absorbed photosynthetically active radiation (APAR), and the lowest daily values were associated with the sunlit foliage group. The mixed sunlit-shaded foliage was the only group to exhibit monthly averages close to the maximum ecosystem LUE parameter (ε max ) used in LUE models for evergreen needle forests (0.0196 μmol C μmol -1 APAR). Implications for remote sensing of carbon uptake dynamics and the interaction of canopy structure and physiology are discussed. 188Résumé. L'efficacité d'utilisation de la lumière (LUE) d'une forêt mature canadienne de pins Douglas (DF49) a été étudiée en utilisant des mesures in situ temporelles, spatiales et spectrales à haute résolution conjointement avec des flux acquis à partir d'une tour d'instrumentation. Nous avons examiné l'indice de réflectance photochimique (PRI), un indice spectral sensible aux conditions de lumière intense qui modifie la réflectance à 531 nm, en combinaison avec plusieurs bandes de référence alternatives à 551, 570 et 488 nm. Ces indices ont été dérivés de spectres de réflectance directionnels acquis par un système radiométrique hyperspectral monté sur la tour DF49 et qui permet de visionner le couvert en effectuant des rotations de 360°plusieurs fois par heure de façon quotidienne tout au long de la saison de croissance de 2006. À partir de l'information sur la structure du cou...

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Abstract:The utilization of remotely sensed observations for light use efficiency (LUE) and tower-based gross primary production (GPP) estimates was studied in a USDA cornfield. Nadir hyperspectral reflectance measurements were acquired at canopy level during a collaborative field campaign conducted in four growing seasons. The Photochemical Reflectance Index (PRI) and solar induced chlorophyll fluorescence (SIF), were derived. SIF retrievals were accomplished in the two telluric atmospheric oxygen OPEN ACCESSRemote Sens. 2013, 5 6858 absorption features centered at 688 nm (O 2 -B) and 760 nm (O 2 -A). The PRI and SIF were examined in conjunction with GPP and LUE determined by flux tower-based measurements. All of these fluxes, environmental variables, and the PRI and SIF exhibited diurnal as well as day-to-day dynamics across the four growing seasons. Consistent with previous studies, the PRI was shown to be related to LUE (r 2 = 0.54 with a logarithm fit), but the relationship varied each year. By combining the PRI and SIF in a linear regression model, stronger performances for GPP estimation were obtained. The strongest relationship (r 2 = 0.80, RMSE = 0.186 mg CO 2 /m 2 /s) was achieved when using the PRI and SIF retrievals at 688 nm. Cross-validation approaches were utilized to demonstrate the robustness and consistency of the performance. This study highlights a GPP retrieval method based entirely on hyperspectral remote sensing observations.