Evaluation of the technical performance of three different commercial digital breast tomosynthesis systems in the clinical environment

The aim of this work was to research and evaluate the performance of three different digital breast tomosynthesis (DBT) systems in the clinical environment (Siemens Mammomat Inspiration, Hologic Selenia Dimensions, and Fujifilm Amulet Innovality). The characterization included the study of the detector, the automatic exposure control, and the resolution of DBT projections and reconstructed planes.The modulation transfer function (MTF) of the DBT projections was measured with a 1 mm thick steel edge, showing a strong anisotropy (30–40% lower MTF_0.5 frequencies in the tube travel direction). The in-plane MTF_0.5, measured with a 25 μm tungsten wire, ranges from 1.3 to 1.8 lp/mm in the tube-travel direction and between 2.4 and 3.7 lp/mm in the chest wall–nipple. In the latter direction, the MTF peak shift is more emphasized for large angular range systems (2.0 versus 1.0 lp/mm). In-depth resolution of the planes, via the full width at half maximum (FWHM) from the point spread function of a 25 μm tungsten wire, is not only influenced by angular range and yields 1.3–4.6 mm among systems. The artifact spread function from 1 mm diameter tungsten beads depends mainly on angular range, yielding two tendencies whether large (FWHM is 4.5 mm) or small (FWHM is 10 mm) angular range is used. DBT delivers per scan a mean glandular dose between 1.4 and 2.7 mGy for a 45 mm thick polymethyl methacrylate (PMMA) block.In conclusion, we have identified and analysed specific metrics that can be used for quality assurance of DBT systems.     

Optimal photon energy comparison between digital breast tomosynthesis and mammography: A case study

A comparison, in terms of the optimal energy that maximizes the image quality between digital breast tomosynthesis (DBT) and digital mammography (DM) was performed in a MAMMOMAT Inspiration system (Siemens) based on amorphous selenium flat panel detector. In this paper we measured the image quality by the signal difference-to-noise ratio (SDNR), and the patient risk by the mean glandular dose (MGD). Using these quantities we compared the optimal voltage that maximizes the image quality both in breast tomosynthesis and standard mammography acquisition mode. The comparison for the two acquisition modes was performed for a W/Rh anode filter combinations by using a 4.5 cm tissue equivalent mammography phantom. Moreover, in order to check if the used equipment was quantum noise limited, the relation of the relative noise with respect to the detector dose was evaluated. Results showed that in the tomosynthesis acquisition mode the optimal voltage is 28 kV, whereas in standard mammography the optimal voltage is 30 kV. The automatic exposure control (AEC) of the system selects 28 kV as optimal voltage both for DBT and DM. Monte Carlo simulations showed a qualitative agreement with the AEC selection system, since an optimal monochromatic energy of 20 keV was found both for DBT and DM. Moreover, the check about the noise showed that the system is not completely quantum noise limited, and this issue could explain the experimental slight difference in terms of optimal voltage between DBT and DM. According to these results, the use of higher voltage settings is not justified for the improvement of the image quality during a DBT examination.     

Desulfurization of dibenzothiophene by lyophilized cells of Pseudomonas delafieldii R-8 in the presence of dodecane

Several parameters that influence the dibenzothiophene (DBT) desulfurization by lyophilized cells of Pseudomonas delafieldii R-8 were studied in the presence of dodecane. The aqueous media tested with pH range in 4.6–8.5 made no obvious difference on the desulfurization activity. The rate and extent of desulfurization were strongly dependent on the volume ratio of oil-to-water, DBT concentration and the cell concentration. The specific desulfurization rate of DBT and 4,6-dimethyl DBT (4,6-DMDBT) could reach 11.4 and 9.4 mmol sulfur kg⁻¹ dry cells (DCW) h⁻¹, respectively. The desulfurization pattern of DBT was represented by the Michaelis–Menten equation. The kinetic parameters, the limiting maximal velocity (V_max) and Michaelis constant (K_m), for desulfurization of DBT were calculated.     

Garlic extract as a novel strategy to hasten dormancy release in buds of ‘Anna’ apple trees

A 2-season orchard trial was carried out to verify the effects of garlic extract (GE), as a novel dormancy-breaking substance, at different concentrations; 0, 50, 100, 150 and 200 ml l^− 1 on bud break dormancy and the metabolic alterations in buds of ‘Anna’ apple trees. Water content, total carbohydrates, reducing and total sugars, anthocyanins, total free amino acids, free proline, total indoles and free phenols were analyzed after the application of GE. The obtained results showed that, GE treatments hastened date of floral bud break and increased percentage of bud break, fruit set, total number of fruits and fruit yield per tree. Except for free phenols, GE also increased the abovementioned chemical components in buds. The best results were obtained from the treatment of 150 ml l^− 1 GE. Therefore, it is concluded that the use of GE at 150 ml l^− 1 could be recommended for improving the bud break, growth and yield of apple trees cv. “Anna”.     

Preventive effect of rikkunshito on gastric motor function inhibited by l-dopa in rats

We previously reported that ghrelin prevented l-dopa (LD)-induced inhibition of gastric emptying (GE) of a non-nutrient solution in rats. Parkinson's disease treatment involves the combined administration of l-dopa with the enzyme l-amino acid decarboxylase inhibitor, carbidopa (CD) to reduce peripheral formation of dopamine. We investigated the effect LD/CD given orogastrically (og) on GE of a non-nutrient or nutrient meal and whether og pretreatment with rikkunshito, a kampo medicine clinically used to treat gastroparesis, influenced LD/CD effect on GE and postprandial antral and duodenal motility in conscious rats. LD/CD (20/2 mg kg⁻¹) decreased significantly GE to 26.3 ± 6.0% compared to 61.2 ± 3.2% in og vehicle monitored 20-min after a non-nutrient meal and to 41.9 ± 5.8% compared to 72.9 ± 5.2% in og vehicle monitored 60 min after a nutrient meal. Rikkunshito (0.5 or 1.0 g kg⁻¹) reduced the LD/CD (20/2 mg kg⁻¹) inhibition of GE of non-nutrient meal (36.9 ± 7.4% and 46.6 ± 4.8% respectively vs. 12.1 ± 7.4% in og vehicle plus LD/CD) while having no effect alone (56.6 ± 8.5%). The ghrelin antagonist, [d-Lys³]-GHRP-6 (1 mg kg⁻¹) injected intraperitoneally partially reversed rikkunshito preventive effect on LD/CD-inhibited GE. Rikkunshito (1.0 g kg⁻¹) blocked LD/CD (20/2 mg kg⁻¹)-induced delayed GE of a nutrient meal and the reduction of postprandial antral motility. In 6-hydroxydopamine-induced Parkinson's disease rat model, rikkunshito (1.0 g kg⁻¹, og) also prevented LD/CD-inhibited gastric emptying of a nutrient meal and enhanced fasting plasma levels of acylated ghrelin. These data indicate that oral rikkunshito alleviates the delayed GE induced by LD/CD in naïve and PD rat model in part through ghrelin-related mechanisms.     

Optimization of the exposure parameters in digital mammography using contrast-detail metrics

PurposeOptimization studies in digital mammography aid to assure the image quality and radiological protection of the patient. The aim of this work is to test effectiveness and applicability of a method based on a Figure of Merit (FOM = (IQF_inv)²/AGD) to improve all the exposure parameters (Target/Filter combination, kVp and mAs) in order to improve the image acquisition technique that will provide the best compromise between image quality and the average glandular dose (AGD).MethodsA contrast-detail analysis, employing the test object CDMAM, was carried out for the digital mammography unit manufactured by Lorad Hologic – model Selenia. We simulated two breast thicknesses using phantoms and a Figure of Merit as optimization tool, which includes an indicator of image quality, the IQF_inv and the average glandular dose. Images of the ACR and TORMAM phantoms were obtained with both, automatic and optimized exposure parameters. In order to compare the image quality, the SNR (Signal to Noise Ratio) was measured in each image.ResultsIn the two phantoms, for both 4.5 and 7.5 cm thicknesses, the AGDs obtained with the optimized parameters show a reduction. In addition, the images obtained with the optimized exposure parameters, had the same or a better image quality when compared to the images obtained using the automatic mode.ConclusionsThe proposed optimization methodology proved to be an effective tool to improve the digital mammography unit, due to the use of objective metrics for evaluation and validation of the results.     

Sensitivity of ACL volume and T21 relaxation time to magnetic resonance imaging scan conditions

Anterior cruciate ligament (ACL) volume and T₂¹ relaxation times from magnetic resonance (MR) images have been previously shown to predict the structural properties of healing ligaments. We investigated whether MR imaging scan resolution and condition (in vivo, in situ, or ex vivo) affected ACL volume and T₂¹ relaxation times in intact ligaments. ACLs of 14 pigs were imaged using a 3 T scanner and a six-channel flexcoil using at least two of four possible scan conditions: (1) in vivo moderate resolution (n = 14); (2) in vivo high resolution (n = 7); (3) in situ high resolution acquired within 60 minutes of euthanasia (n = 6); and (4) ex vivo high resolution following hind limb disarticulation and one freeze-thaw cycle (n = 7). T₂¹ relaxation times were mapped to the ACL voxels. The total ACL volume was then divided into four sub-volumes (Vol_1–4) based on predetermined increasing ranges of T₂¹ times. ACL T₂¹ statistics (first quartile, median, and standard deviation (SD)) were computed. Scan resolution had no effect on the total ACL volume, but Vol₁ and first quartile T₂¹ times decreased with high resolution and in situ/ex vivo scan conditions. The most dramatic differences in T₂¹ summary statistics were between in vivo moderate and ex vivo high resolution scan conditions that included a freeze-thaw cycle: ACL T₂¹ SD increased by over 50% in 9 animals, and more than 90% in 4 animals. Our results indicated that T₂¹-based prediction models to quantify in vivo structural properties of healing ligaments should be based on high resolution in vivo MR scan conditions.     

Faisabilité et intérêt d’un nouvel algorithme de reconstruction des images TEP-18FDG (AW OSEM DR) pour la délimitation des volumes cibles en radiothérapie. À propos d’un cas de néoplasie ORL

ObjectiveWe compared two reconstruction methods for 18fluorodeoxyglucose (¹⁸F-FDG) positron emission tomography (PET) images with “attenuation weighted ordered subset expectation maximization” using either the manufacturer-provided (AW-OSEM) or a “Detector response” (AW-OSEM DR) tomographic operator. We looked at the feasibility of using the latter reconstruction for radiotherapy target volumes definition in cancers of the superior aero-digestive tract (VADS). In this preliminary study, we first assessed the spatial resolution of images obtained with AW-OSEM and AW-OSEM DR on a Biograph™ 6, and secondly target volumes of radiotherapy “Gross Tumor Volume” (GTV), “Clinical Target Volume” (CTV) and “Planning Target Volume” (PTV) obtained with each of these reconstruction methods.Material and methodsThe spatial resolution was measured on a test object containing 4 radioactive point sources. Furthermore, radiotherapy target volumes have been defined with the software Eclipse™ on injected scanner (CT IV) and PET/CT (PET AW-OSEM and PET AW-OSEM DR) images.ResultsSpatial resolution was improved with AW-OSEM DR algorithm reconstruction compared to images obtained with AW-OSEM reconstruction (from 7.5 mm down to 5.4 mm for the highest reduction). GTV from AW-OSEM DR reconstruction with 42 and 50% of the “Standard uptake value maximum” (SUVmax) semi-automatic threshold (1.2 and 0.7 cm³ respectively) were lower than those obtained with AW-OSEM (3.6 and 2.2 cm³ respectively). They were also lower than GTV defined with CT IV (5.5 cm³). It was the same for CTV and PTV.ConclusionThis study showed that AW-OSEM DR reconstruction method allows less impaired spatial resolution than AW-OSEM. In the case of radiotherapy target volumes delineation, AW-OSEM DR may decrease the GTV, CTV and PTV and therefore the risk of side effects associated with organs at risk.     

Evaluation of digital tomosynthesis reconstruction algorithms used to reduce metal artifacts for arthroplasty: A phantom study

To investigate methods to reduce metal artifacts during digital tomosynthesis for arthroplasty, we evaluated five algorithms with and without metal artifact reduction (MAR)-processing tested under different radiation doses (0.54, 0.47, and 0.33 mSv): adaptive steepest descent projection onto convex sets (ASD-POCS), simultaneous algebraic reconstruction technique total variation (SART-TV), filtered back projection (FBP), maximum likelihood expectation maximization (MLEM), and SART. The algorithms were assessed by determining the artifact index (AI) and artifact spread function (ASF) on a prosthesis phantom. The AI data were statistically analyzed by two-way analysis of variance. Without MAR-processing, the greatest degree of effectiveness of the MLEM algorithm for reducing prosthetic phantom-related metal artifacts was achieved by quantification using the AI (MLEM vs. ASD-POCS, SART-TV, SART, and FBP; all P < 0.05). With MAR-processing, the greatest degree of effectiveness of the MLEM, ASD-POCS, SART-TV, and SART algorithms for reducing prosthetic phantom-related metal artifacts was achieved by quantification using the AI (MLEM, ASD-POCS, SART-TV, and SART vs. FBP; all P < 0.05). When assessed by ASF, metal artifact reduction was largest for the MLEM algorithm without MAR-processing and ASD-POCS, SART-TV, and SART algorithm with MAR-processing. In ASF, the effect of metal artifact reduction was always greater at reduced radiation doses, regardless of which reconstruction algorithm with and without MAR-processing was used. In this phantom study, the MLEM algorithm without MAR-processing and ASD-POCS, SART-TV, and SART algorithm with MAR-processing gave improved metal artifact reduction.     

Object shape dependency of in-plane resolution for iterative reconstruction of computed tomography

The present study aimed to investigate whether the in-plane resolution property of iterative reconstruction (IR) of computed tomography (CT) data is object shape-dependent by testing columnar shapes with diameters of 3, 7, and 10 cm (circular edge method) and a cubic shape with 5-cm side lengths (linear edge method). For each shape, objects were constructed of acrylic (contrast in Hounsfield units [ΔHU] = 120) as well as a soft tissue equivalent material (ΔHU = 50). For each shape, we measured the modulation transfer functions (MTFs) of IR and filtered back projection (FBP) using two multi-slice CT scanners at scan doses of 5 and 10 mGy. In addition, we evaluated a thin metal wire using the conventional method at 10 mGy. For FBP images, the MTF results of the tested objects and the wire method showed substantial agreement, thus demonstrating the validity of our analysis technique. For IR images, the MTF results of different shapes were nearly identical for each object contrast and dose combination, and we did not observe shape-dependent effects of the resolution properties of either tested IR. We conclude that both the circular edge method and linear edge method are equally useful for evaluating the resolution properties of IRs.     

Comparison between new-generation SiPM-based and conventional PMT-based TOF-PET/CT

PurposeThis study aimed to determine whether the SiPM-PET/CT, Discovery MI (DMI) performs better than the PMT-PET/CT system, Discovery 710 (D710).MethodsThe physical performance of both systems was evaluated using NEMA NU 2 standards. Contrast (%), uniformity and image noise (%) are criteria proposed by the Japanese Society of Nuclear Medicine (JSNM) for phantom tests and were determined in images acquired from Hoffman and uniform phantoms using the DMI and D710. Brain and whole-body [¹⁸F]FDG images were also acquired from a healthy male using the DMI and D710.ResultsThe spatial resolution at 1.0 cm off-center in the DMI and D710 was 3.91 and 4.52 mm, respectively. The sensitivity of the DMI and D710 was 12.62 and 7.50 cps/kBq, respectively. The observed peak noise-equivalent count rates were 185.6 kcps at 22.5 kBq/mL and 137.0 kcps at 29.0 kBq/mL, and the scatter fractions were 42.1% and 37.9% in the DMI and D710, respectively. The D710 had better contrast recovery and lower background variability. Contrast, uniformity and image noise in the DMI were 61.0%, 0.0225, and 7.85%, respectively. These outcomes were better than those derived from the D710 and satisfied the JSNM criteria. Brain images acquired by the DMI had better grey-to-white matter contrast and lower image noise at the edge of axial field of view.ConclusionsThe DMI offers better sensitivity, performance under conditions of high count rates and image quality than the conventional PMT-PET/CT system, D710.     

Validation of a free software for unsupervised assessment of abdominal fat in MRI

PurposeTo demonstrate the accuracy of an unsupervised (fully automated) software for fat segmentation in magnetic resonance imaging. The proposed software is a freeware solution developed in ImageJ that enables the quantification of metabolically different adipose tissues in large cohort studies.MethodsThe lumbar part of the abdomen (19 cm in craniocaudal direction, centered in L3) of eleven healthy volunteers (age range: 21–46 years, BMI range: 21.7–31.6 kg/m²) was examined in a breath hold on expiration with a GE T1 Dixon sequence. Single-slice and volumetric data were considered for each subject. The results of the visceral and subcutaneous adipose tissue assessments obtained by the unsupervised software were compared to supervised segmentations of reference. The associated statistical analysis included Pearson correlations, Bland-Altman plots and volumetric differences (VD_%).ResultsValues calculated by the unsupervised software significantly correlated with corresponding supervised segmentations of reference for both subcutaneous adipose tissue – SAT (R = 0.9996, p < 0.001) and visceral adipose tissue – VAT (R = 0.995, p < 0.001). Bland-Altman plots showed the absence of systematic errors and a limited spread of the differences. In the single-slice analysis, VD_% were (1.6 ± 2.9)% for SAT and (4.9 ± 6.9)% for VAT. In the volumetric analysis, VD_% were (1.3 ± 0.9)% for SAT and (2.9 ± 2.7)% for VAT.ConclusionsThe developed software is capable of segmenting the metabolically different adipose tissues with a high degree of accuracy. This free add-on software for ImageJ can easily have a widespread and enable large-scale population studies regarding the adipose tissue and its related diseases.     

Objective assessment of low-contrast computed tomography images with iterative reconstruction

ObjectiveThis study aims to assess low-contrast image quality using a low-contrast object specific contrast-to-noise ratio (CNR_LO) analysis for iterative reconstruction (IR) computed tomography (CT) images.MethodsA phantom composed of low-contrast rods placed in a uniform material was used in this study. Images were reconstructed using filtered back projection (FBP) and IR (Adaptive Iterative Dose Reduction 3D). Scans were performed at six dose levels: 1.0, 1.8, 3.1, 4.6, 7.1 and 13.3 mGy. Objective image quality was assessed by comparing CNR_LO with CNR using a human observer test.ResultsCompared with FBP, IR yielded increased CNR at the same dose levels. The results of CNR_LO and observer tests showed similarities or only marginal differences between FBP and IR at the same dose levels. The coefficient of determination for CNR_LO was significantly better (R² = 0.86) than that of CNR (R² = 0.47).ConclusionFor IR, CNR_LO could potentially serve as an objective index reflective of a human observer assessment. The results of CNR_LO test indicated that the IR algorithm was not superior to FBP in terms of low-contrast detectability at the same radiation doses.     

Comparison of neoadjuvant oral chemotherapy with UFT plus Folinic acid or Capecitabine concomitant with radiotherapy on locally advanced rectal cancer

AimTo evaluate the differences in treatment response and the impact on survival with both oral agents (UFT and Capecitabine) as neoadjuvant chemotherapy administered concomitantly with radiotherapy.BackgroundThere are still no studies comparing the use of neoadjuvant oral chemotherapy either with UFT plus Folinic acid or Capecitabine concomitant with radiotherapy in locally advanced rectal cancer (LARC).Materials and methodsA set of 112 patients with LARC were treated preoperatively. GROUP 1 – 61 patients underwent concomitant oral chemotherapy with Capecitabine (825 mg/m² twice daily). GROUP 2 – 51 patients submitted to concomitant oral chemotherapy with UFT (300 mg/m²/d) + Folinic acid (90 mg/d) and radiotherapy. 57.1% of patients were submitted to adjuvant chemotherapy.ResultsGROUP 1: acute toxicity – 80.3%; pathological complete response (pCR) – 10.5%; tumor downstaging (TD) – 49.1%; nodal downstaging (ND) – 76.5%; loco-regional response (LRR) – 71.9%; toxicity to adjuvant chemotherapy – 75%. GROUP 2: acute toxicity – 80.4%; pCR – 28%; TD – 62%; ND – 75.6%; LRR – 78%; toxicity to adjuvant chemotherapy – 56%. There was no difference in survival nor loco-regional control between the groups.ConclusionsPatients treated with neoadjuvant oral UFT + Folinic acid had a higher rate of pathologic complete response than patients treated with Capecitabine concomitant with radiotherapy. There were no differences in downstaging, LRR, toxicity, survival or loco-regional control between both groups. There was a trend to a higher rate of toxicity to adjuvant chemotherapy in the Capecitabine group.     

Influence of temperature and exercise on growth performance,muscle, and adipose tissue in pacus (Piaractus mesopotamicus)

The aim of this study was to evaluate the effects of temperature and swimming exercise on fish growth in pacus (Piaractus mesopotamicus). Pacus weighing 0.9 – 1.9 g and 2.7 – 4.2 cm in standard length were cultivated at an initial density of 120 fish m⁻³ in 3 recirculation systems containing 6 water tanks at a volume of 0.5 m³ each at temperatures of 24, 28 and 32 °C. At each temperature, three tanks were modified to generate exercise activity in the specimens and force the fish to swim under a current speed of 27.5 cm s⁻¹. At the end of the experiment, the following metrics were evaluated: fish performance, morphometry (length, width, height and perimeter in different body positions), and the diameter and density of muscle and subcutaneous ventral adipose tissues. At 28 °C, pacus were both heavier and had greater weight gain after 240 days of cultivation. Additionally, exercise improved the feed conversion. An increase of 4 °C (30 °C) did not provide any improvement in the performance of the fish. However, swimming exercise improved the performance of pacus, providing increases of 38% and a 15% improvement in feed conversion. Both temperature and exercise influenced the body morphology (especially in the caudal region) and the cellularity of white and red muscle fibers and adipocytes.     

Novel 6 MV X-ray photoneutron detection and dosimetry of medical accelerators

PurposeDosimetry of fast, epithermal and thermal photoneutrons in 6 MV X-ray beams of two medical accelerators were studied by novel dosimetry methods.MethodsA Siemens ONCOR and an Elekta COMPACT medical accelerators were used. Fast, epithermal and thermal photoneutron dose equivalents in 10 cm × 10 cm 6 MV X-rays fields were determined in air and on surface of a polyethylene phantom in X and Y directions. Polycarbonate dosimeters as bare or with enriched ¹⁰B convertors (with or without cadmium covers) were used applying a 50 Hz-HV electrochemical etching method.ResultsFast, epithermal and thermal photoneutron dose equivalents were efficiently determined respectively as ∼1145.8, ∼45.3 and ∼170.6 μSv in air and ∼1888.5, ∼96.1 and ∼640.6 μSv on phantom per 100 Gy X-rays at the isocenter of Siemens ONCOR accelerator in air. The dose equivalent is maximum at the isocenter which decreases as distance from it increases reaching a constant level. Tissue-to-air ratios are constants up to 15 cm from the isocenter. No photoneutrons was detected in the Elekta COMPACT accelerator.ConclusionsFast, epithermal and thermal photoneutron dosimetry of 6 MV X-rays were made by novel dosimetry methods in a Siemens ONCOR accelerator with sum dose equivalent per Gy of ∼0.0014% μSv with ∼0.21 MeV mean energy at the isocenter; i.e. ∼150 times smaller than that of 18 MV X-rays. This observation assures clinical safety of 6 MV X-rays in particular in single-mode machines like Elekta COMPACT producing no photoneutrons due to no “beryllium exit window” in the head structure.     

Electrochemical studies of biocatalytic anode of sulfonated graphene/ferritin/glucose oxidase layer-by-layer biocomposite films for mediated electron transfer

In this study, a bioanode was developed by using layer-by-layer (LBL) assembly of sulfonated graphene (SG)/ferritin (Frt)/glucose oxidase (GOx). The SG/Frt biocomposite was used as an electron transfer elevator and mediator, respectively. Glucose oxidase (GOx) from Aspergillus niger was applied as a glucose oxidation biocatalyst. The electrocatalytic oxidation of glucose using GOx modified electrode increases with an increase in the concentration of glucose in the range of 10–50 mM. The electrochemical measurements of the electrode was carried out by using cyclic voltammetry (CV) at different scan rates (20–100 mV s⁻¹) in 30 mM of glucose solution prepared in 0.3 M potassium ferrocyanide (K₄Fe(CN)₆) and linear sweep voltammetry (LSV). A saturation current density of 50 ± 2 mA cm⁻² at a scan rate of 100 mV s⁻¹ for the oxidation of 30 Mm glucose is achieved.     

Thermoimaging as a tool for studying light-induced heating of leaves: Correlation of heat dissipation with the efficiency of photosystem II photochemistry and non-photochemical quenching

Thermoimaging – a highly sensitive and non-invasive method of temperature measurement – was applied to explore the role of changing photosynthetic efficiency in light-induced heating of tobacco (Nicotiana tabacum cv. Samsun) leaves. In the absence of evaporative cooling through the stomata, which was achieved by covering leaves with Vaseline, illumination with 50–1400 μM photons m^?2 s^?1 intensity of photosynthetically active radiation resulted in ≈1–5 °C leaf temperature increase in about 2 min. The heating effect showed a non-linear correlation with the extent of non-photochemical quenching (NPQ) resulting in higher leaf temperatures at higher NPQ values. When leaves were adapted to excessive irradiance (1300 μM photons m^?2 s^?1 for 6 h), which resulted in reduction of photosynthetic efficiency and amplification of NPQ the light-induced heating effect was enhanced. The experimental results have been explained on the basis of a simple theoretical model characterizing the balance of energy fluxes in leaves in relation to the efficiency of photosystem II photochemistry and non-photochemical quenching. The role of alternative energy dissipation pathways outside of PSII in the phenomenon of light-induced leaf heating is also discussed.     

Influence of the Włocławek Reservoir on hydrochemistry and plankton of a large,lowland river (the Lower Vistula River,Poland)

The research on the W?oc?awek Reservoir (WR), situated on the Lower Vistula River (Poland), was carried out during two periods: between 1986 and 2002, hydrochemistry was studied, and between 1994 and 2000 – plankton. WR is 70 km² in area, its capacity is 370 × 10⁶ m³ and the retention time with the average flow rate (Q) amounts to 930 m³ s^?1 – only 5 days (!). Until 2002, due to cyclic work of a hydroelectric power plant, considerable variability in the daily flow rate was recorded (from 600 to 1800 m³ s^?1). Its specific hydrology and fluvial character mean that WR functions in a completely different way compared to dam reservoirs described in textbooks, with significantly longer retention time.WR significantly improves most of the water quality variables in the river. It reduces the concentration of suspended matter (on average by more than 50%), P_tot (by 16%), BOD₅ (by 40%) and chlorophyll “a” (by 50–60%) (unpublished data).Phytoplankton is rich in species – altogether 441 taxa, with the count of 7.4 × 10⁶ individuals per dm^?3 and biomass of 16 mg dm^?3. Throughout the research period, a significant reduction in the abundance of phytoplankton was recorded in WR, sometimes more than 60%. The total number of zooplankton taxa at the site upstream from WR and in the reservoir was almost identical (68 and 67), however in the reservoir itself, a small decrease in the number of Rotifera species and an increase in the number of Crustacea species was observed, as well as a significant, fourfold increase in the total zooplankton biomass. The aforementioned reduction of phytoplankton and enrichment of the river with Crustacea are one of the major biocenotic consequences of the functioning of the W?oc?awek Reservoir.     

Effects of vegetation,limestone and aeration on nitritation,anammox and denitrification in wetland treatment systems

Integration of partial nitrification (nitritation) and anaerobic ammonium oxidation (anammox) in constructed wetlands creates a sustainable design for nitrogen removal. Three wetland treatment systems were operated with synthetic wastewater (60 mg NH₃–N L^?1) in a batch mode of fill – 1-week reaction – drain. Each treatment system had a surface flow wetland (unplanted, planted, and planted plus aerated, respectively) with a rooting substrate of sandy loam and limestone pellets, followed by an unplanted subsurface flow wetland. Meanwhile, three surface flow wetlands with a substrate of sandy loam and pavestone were operated in parallel to the former surface flow wetlands. Influent and effluent were monitored weekly for five cycles. Aeration reduced nitrogen removal due to hindered nitrate reduction. Vegetation maintained pH near neutral and moderate dissolved oxygen, significantly improved ammonia removal by anammox, and had higher TN removal due to coexistence of anammox and denitrification in anaerobic biofilm layers. Nitrite production was at a peak at the residence time of 4–5 d. Relative to pavestone, limestone increased the nitrite mass production peak by 97%. The subsurface flow wetlands removed nitrogen via nitritation and anammox, having an anammox activity of up to 2.4 g N m^?3 d^?1 over a startup operation of two months.