Browsing by Subject "SPAD"

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  • Khazaei, Hamid; Wach, Damian; Pecio, Alicja; Vandenberg, Albert; Stoddard, Frederick L. (2019)
    Increasing productivity through improvement of photosynthesis in faba bean breeding programmes requires understanding of the genetic control of photosynthesis-related traits. Hence, we investigated the gene action of leaf area, gas exchange traits, canopy temperature, chlorophyll content, chlorophyll fluorescence parameters and biomass. We chose inbred lines derived from cultivars 'Aurora' (Sweden) and 'Melodie' (France) along with an Andean accession, ILB 938, crossed them (Aurora/2 x Melodie/2, ILB 938/2 x Aurora/2 and Melodie/2 x ILB 938/2), and prepared the six standard generations for quantitative analysis (P-1, P-2, F-1, F-2, B-1, and B-2). Gene action was complex for each trait, involving additive and dominance gene actions and interactions. Additive gene action was important for SPAD, photosynthetic rate, stomatal conductance and F-v/F-m. Dominance effect was important for biomass production. It is suggested that breeders selecting for productivity can maximize genetic gain by selecting early generations for canopy temperature, SPAD and F-v/F-m, then later generations for biomass. The information on genetics of various contributing traits of photosynthesis will assist plant breeders in choosing an appropriate breeding strategy for enhancing productivity in faba bean.
  • Kymäläinen, Anni (Helsingfors universitet, 2013)
    In Finland, potato is cultivated on more than 22 000 hectares, which makes it one of the most important crops. Potato is considered drought sensitivive because of it´s shallow roots. Thus, irrigation is recommended to improve not only the yield but to ensure good tuber quality. However irrigation is increases production costs. Nitrogen fertilization also affects yield and tuber quality but excess nitrogen can increase costs, nutrient leaching and reduce tuber quality. Thus, the equipment that can be used to estimate nutrient deficiencies have become more common. The effect of irrigation and nitrogen fertilization on growth and tuber yield of potato was investigated during 2001 – 2003 at Potato Research Institute in Lammi, Finland. Irrigation methods were surface irrigation and subsurface drip irrigation. Nitrogen was applied as a single dose when planting or as sidedress. Further interest was to find out whether SPAD values could be used to evaluate both the demand and timing of potato nitrogen fertilization. Irrigation did not affect potato development, tuber yield or starch content. Irrigation methods had no effect on tuber yield either. However, irrigation reduced the yield of marketable tuber yield. The benefit of drip irrigation was the possibility of combined irrigation and fertilizer application. Nitrogen increased tuber yield. The potato stand that received nitrogen as a single dose produced the greatest yield. However, even the potato stand which did not receive nitrogen produced quite large yield, over 30 tn/ha. In 2003, the stands which were given sidedress nitrogen with drip irrigation produced even greater yield than the ones that had been given nitrogen as a single dose. The stands which did not receive nitrogen had highest starch content. The SPAD values were used when estimating the demand of nitrogen fertilization with drip irrigation. SPAD measurements are easily conducted and non-destructive. SPAD values can be used to estimate the demand and timing of fertilization, even though there seems to be slight delay until the values indicate the nutrient deficiency.
  • Rojalin, Tatu (Helsingfors universitet, 2015)
    Raman spectroscopy is based on vibrations that occur between the atoms of a compound. The overall structural energy is derived from the electronical energy as well as vibrational, rotational and translational energy. In Raman spectroscopy the vibrational and rotational energies are essential. Usually the excitation energy used in Raman spectroscopy can be either in the region of visible light or NIR. The sample absorbs the energy and energy is also scattered back to all possible directions. Elastic scattering is called the Rayleigh scattering. In that case the back-scattered photons have an equal energy as the original excitation energy. However, some of the scattering happens inelastically and it forms the basis of Raman-phenomena. If the detected photons have smaller energy than the original, it is called the Stokes scattering. If the energy is bigger, it is anti-Stokes scattering. Raman is typically very rare and weak phenomenon. The spectral features in Raman spectra consist of the intensities and energies of the back scattered photons. Raman spectroscopy provides very accurate and detailed structural information on the molecule. It is basically a label-free technique with minimal need for sample preparation and the measurements can also be carried out e.g. through container walls. Further, Raman is quite insensitive to hydrous samples and it is suitable to solutions and biological assessments. However, there are some drawbacks that are formed by the luminescence phenomena i.e. fluorescence. Strong fluorescent backgrounds can mask the relevant Raman features in spectra because Raman and fluorescence are competetive processes. For instance many drug molecules have such structures that they cause strong fluorescence. It is also one of the reasons that pharmaceutical applications and measurements have been partly limited due to this problem. There are applications to improve and enhance a Raman signal. For example resonance phenomena and SERS are favored. To solve the fluorescence-related problems there are also means; one can change the laser wavelenght, photobleach the sample or apply different kinds of data manipulation techniques to the spectral data achieved. There are drawbacks with these methods. They can be slow, complex, damage the samples and still insufficient fluorescence suppression is a problem. In this study a novel time-gated CMOS-SPAD detection technique is applied to non-fluorescent and fluorescent drug measurements. The new detection system has a programmable on-chip delay time and it is synchronized with a picosecond pulsed laser. The scattered photons can be measured in the time scale when they are simultaneously measured in traditional energy and intensity wise. Raman scattering occurs in the timescale of sub-picoseconds while the fluorescence phenomena happen typically in the order of nanoseconds. This time difference can be exploited effectively to suppress the fluorescence. In the literature review of this study the basis of vibrational spectroscopy is introduced - especially Raman spectroscopy. The techniques related, as well as the novel time-resolved technique are covered. Further, different kinds of applications in the field of Raman spectroscopy are reviewed, mainly pharmaceutics-related and biologically relevant applications. In the experimental work the focus was to compare a continuous-wave 785 nm laser setup coupled with the CCD-detector to the pulsed picosecond 523 nm laser coupled with the CMOS-SPAD-detector. The measurements were performed on different kinds of drugs, both non-fluorescent and fluorescent. The aim was to obtain information on the effectiveness of CMOS-SPAD-technique on fluorescence suppression for solid drugs and solutions. Secondary goals were to collect knowledge on the similarities and differences between the Raman setups used for solution measurements, to optimize and discuss the key elements of setups for solids and solutions and to show preliminarily the applicability of the CMOS-SPAD-system on fluorescent drug's solutions as well as find out the requirements related to quantitative assessments using Raman spectroscopy. In drug research there is also constant need for reliable in vitro cell assays. The assessments made in this study may prove useful to the future applications e.g. measurements with living cells. An effective fluorescence suppression was achieved to strong fluorescent backgrounds using the novel time-resolved CMOS-SPAD-detection system coupled with the pulsed picosecond 532 nm laser. The setup is potentially a convenient tool to overcome many fluorescence-related limitations of Raman spectroscopy for laboratory and process analytical technology (PAT) use in the pharmaceutical setting. The results achieved encourage to consider that with careful calibration and method validation there is potential for quantitative analysis, biopharmaceutical and biological applications e.g. in vitro cell studies where most Raman techniques suffer from strong fluorescence backgrounds. Other potential fields for future applications can be also considered.
  • Lipiäinen, Tiina; Pessi, Jenni; Movahedi, Parisa; Koivistoinen, Juha; Kurki, Lauri; Tenhunen, Mari; Yliruusi, Jouko; Juppo, Anne M.; Heikkonen, Jukka; Pahikkala, Tapio; Strachan, Clare J. (2018)
    Raman spectroscopy is widely used for quantitative pharmaceutical analysis, but a common obstacle to its use is sample fluorescence masking the Raman signal. Time-gating provides an instrument-based method for rejecting fluorescence through temporal resolution of the spectral signal and allows Raman spectra of fluorescent materials to be obtained. An additional practical advantage is that analysis is possible in ambient lighting. This study assesses the efficacy of time-gated Raman spectroscopy for the quantitative measurement of fluorescent pharmaceuticals. Time-gated Raman spectroscopy with a 128 X (2) X 4 CMOS SPAD detector was applied for quantitative analysis of ternary mixtures of solid-state forms of the model drug, piroxicam (PRX). Partial least-squares (PLS) regression allowed quantification, with Raman-active time domain selection (based on visual inspection) improving performance. Model performance was further improved by using kernel-based regularized least-squares (RLS) regression with greedy feature selection in which the data use in both the Raman shift and time dimensions was statistically optimized. Overall, time-gated Raman spectroscopy, especially with optimized data analysis in both the spectral and time dimensions, shows potential for sensitive and relatively routine quantitative analysis of photoluminescent pharmaceuticals during drug development and manufacturing.