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Aims: The aim of the SCIENCE trial was to investigate whether a single treatment with direct intramyocardial injections of adipose tissue‐derived mesenchymal stromal cells (CSCC_ASCs) was safe and improved cardiac function in patients with chronic ischaemic heart failure with reduced ejection fraction (HFrEF). Methods and results: The study was a European multicentre, double‐blind, placebo‐controlled phase II trial using allogeneic CSCC_ASCs from healthy donors or placebo (2:1 randomization). Main inclusion criteria were New York Heart Association (NYHA) class II–III, left ventricular ejection fraction (LVEF) <45%, and N‐terminal pro‐B‐type natriuretic peptide (NT‐proBNP) levels >300 pg/ml. CSCC_ASCs or placebo (isotonic saline) were injected directly into viable myocardium. The primary endpoint was change in left ventricular end‐systolic volume (LVESV) at 6‐month follow‐up measured by echocardiography. A total of 133 symptomatic HFrEF patients were included. The treatment was safe without any drug‐related severe adverse events or difference in cardiac‐related adverse events during a 3‐year follow‐up period. There were no significant differences between groups during follow‐up in LVESV (0.3 ± 5.0 ml, p = 0.945), nor in secondary endpoints of left ventricular end‐diastolic volume (−2.0 ± 6.0 ml, p = 0.736) and LVEF (−1.6 ± 1.0%, p = 0.119). The NYHA class improved slightly within the first year in both groups without any difference between groups. There were no changes in 6‐min walk test, NT‐proBNP, C‐reactive protein or quality of life the first year in any groups. Conclusion: The SCIENCE trial demonstrated safety of intramyocardial allogeneic CSCC_ASC therapy in patients with chronic HFrEF. However, it was not possible to improve the pre‐defined endpoints and induce restoration of cardiac function or clinical symptoms. [ABSTRACT FROM AUTHOR]

Aims: Patients suffering from chronic ischaemic heart failure with reduced left ventricular ejection fraction (HFrEF) have reduced quality‐of‐life, repetitive hospital admissions, and reduced life expectancy. Allogeneic cell therapy is currently investigated as a potential treatment option after initially encouraging results from clinical autologous and allogeneic trials in patients with HFrEF. We aimed to investigate the allogeneic Cardiology Stem Cell Centre Adipose tissue derived mesenchymal Stromal Cell product (CSCC_ASC) as an add‐on therapy in patients with chronic HFrEF. Methods and results: This is a Danish multi‐centre double‐blinded placebo‐controlled phase II study with direct intra‐myocardial injections of allogeneic CSCC_ASC. A total of 81 HFrEF patients were included and randomized 2:1 to CSCC_ASC or placebo injections. The inclusion criteria were reduced left ventricular ejection fraction (LVEF ≤ 45%), New York Heart Association (NYHA) class II‐III despite optimal anti‐congestive heart failure medication and no further revascularization options. Injections of 0.3 mL CSCC_ASC (total cell dose 100 × 106 ASCs) (n = 54) or isotonic saline (n = 27) were performed into the viable myocardium in the border zone of infarcted tissue using the NOGA Myostar® catheter (Biological Delivery System, Cordis, Johnson & Johnson, USA). The primary endpoint, left ventricular end systolic volume (LVESV), was evaluated at 6‐month follow‐up. The safety was measured during a 3‐years follow‐up period. Results: Mean age was 67.0 ± 9.0 years and 66.6 ± 8.1 years in the ASC and placebo groups, respectively. LVESV was unchanged from baseline to 6‐month follow‐up in the ASC (125.7 ± 68.8 mL and 126.3 ± 72.5 mL, P = 0.827) and placebo (134.6 ± 45.8 mL and 135.3 ± 49.6 mL, P = 0.855) group without any differences between the groups (0.0 mL (95% CI −9.1 to 9.0 mL, P = 0.992). Neither were there significant changes in left ventricular end diastolic volume or LVEF within the two groups or between groups −5.7 mL (95% CI −16.7 to 5.3 mL, P = 0.306) and −1.7% (95% CI −4.4. to 1.0, P = 0.212), respectively). NYHA classification and 6‐min walk test did not alter significantly in the two groups (P > 0.05). The quality‐of‐life, total symptom, and overall summary score improved significantly only in the ASC group but not between groups. There were 24 serious adverse events (SAEs) in the ASC group and 11 SAEs in the placebo group without any significant differences between the two groups at 1‐year follow‐up. Kaplan–Meier plot using log‐rank test of combined cardiac events showed an overall mean time to event of 30 ± 2 months in the ASC group and 29 ± 2 months in the placebo group without any differences between the groups during the 3 years follow‐up period (P = 0.994). Conclusions: Intramyocardial CSCC_ASC injections in patients with chronic HFrEF were safe but did not improve myocardial function or structure, nor clinical symptoms. [ABSTRACT FROM AUTHOR]

Background: There is increased interest in in vivo dosimetry for 192Ir brachytherapy (BT) treatments using high atomic number (Z) inorganic scintillators. Their high light output enables construction of small detectors with negligible stem effect and simple readout electronics. Experimental determination of absorbed‐dose energy dependence of detectors relative to water is prevalent, but it can be prone to high detector positioning uncertainties and does not allow for decoupling of absorbed‐dose energy dependence from other factors affecting detector response. Purpose: To investigate which measurement conditions and detector properties could affect their absorbed‐dose energy dependence in BT in vivo dosimetry. Methods: We used a general‐purpose Monte Carlo (MC) code PENELOPE for the characterization of high‐Z inorganic scintillators with the focus on ZnSe (Z¯=32$\bar{Z}=32$) Z. Two other promising media CsI (Z¯=54$\bar{Z}=54$) and Al2O3 (Z¯=11$\bar{Z}=11$) were included for comparison in selected scenarios. We determined absorbed‐dose energy dependence of crystals relative to water under different scatter conditions (calibration phantom 12 × 12 × 30 cm3, characterization phantoms 20 × 20 × 20 cm3, 30 × 30 × 30 cm3, 40 × 40 × 40 cm3, and patient‐like elliptic phantom 40 × 30 × 25 cm3). To mimic irradiation conditions during prostate treatments, we evaluated whether the presence of pelvic bones and calcifications affect ZnSe response. ZnSe detector design influence was also investigated. Results: In contrast to low‐Z organic and medium‐Z inorganic scintillators, ZnSe and CsI media have substantially greater absorbed‐dose energy dependence relative to water. The response was phantom‐size dependent and changed by 11% between limited‐ and full‐scatter conditions for ZnSe, but not for Al2O3. For a given phantom size, a part of the absorbed‐dose energy dependence of ZnSe is caused not due to in‐phantom scatter but due to source anisotropy. Thus, the absorbed‐dose energy dependence of high‐Z scintillators is a function of not only the radial distance but also the polar angle. Pelvic bones did not affect ZnSe response, whereas large and intermediate size calcifications reduced it by 9% and 5%, respectively, when placed midway between the source and the detector. Conclusions: Unlike currently prevalent low‐ and medium‐Z scintillators, high‐Z crystals are sensitive to characterization and in vivo measurement conditions. However, good agreement between MC data for ZnSe in the present study and experimental data for ZnSe:O by Jørgensen et al. (2021) suggests that detector signal is proportional to the average absorbed dose to the detector cavity. This enables an easy correction for non‐TG43‐like scenarios (e.g., patient sizes and calcifications) through MC simulations. Such information should be provided to the clinic by the detector vendors. [ABSTRACT FROM AUTHOR]

Purpose: High‐dose rate (HDR) and pulsed‐dose rate (PDR) brachytherapy would benefit from an independent treatment verification system to monitor treatment delivery and to detect errors in real time. This paper characterizes and provides an uncertainty budget for a detector based on a fiber‐coupled high‐Z inorganic scintillator capable of performing time‐resolved in vivo dosimetry during HDR and PDR brachytherapy. Method: The detector was composed of a detector probe and an optical reader. The detector probe consisted of either a 0.5 × 0.4 × 0.4 mm3 (HDR) or a 1.0 × 0.4 × 0.4 mm3 (PDR) cuboid ZnSe:O crystal glued onto an optical‐fiber cable. The outer diameter of the detector probes was 1 mm, and fit inside standard brachytherapy catheters. The signal from the detector probe was read out at 20 Hz by a photodiode and a data acquisition device inside the optical reader. In order to construct an uncertainty budget for the detector, six characteristics were determined: (1) temperature dependence of the detector probe, (2) energy dependence as a function of the probe‐to‐source position in 2D (determined with 2 mm resolution using a robotic arm), (3) the signal‐to‐noise ratio (SNR), (4) short‐term stability over 8 h, and (5) long‐term stability of three optical readers and four probes used for in vivo monitoring in HDR and PDR treatments over 21 months (196 treatments and 189 detector calibrations, and (6) dose‐rate dependence. Results: The total uncertainty of the detector at a 20 mm probe‐to‐source distance was < 5.1% and < 5.8% for the HDR and PDR versions, respectively. Regarding the above characteristics, (1) the sensitivity of the detector decreased by an average of 1.4%/°C for detector probe temperatures varying from 22 to 37°C; (2) the energy dependence of the detector was nonlinear and depended on both probe‐to‐source distance and the angle between the probe and the brachytherapy source; (3) the median SNRs were 187 and 34 at a 20 mm probe‐to‐source distance for the HDR and PDR versions, respectively (corresponding median source activities of 4.8 and 0.56 Ci, respectively); (4) the detector response varied by 0.6% in 11 identical irradiations over 8 h; (5) the sensitivity of the four detector probes decreased systematically by 0–1.2%/100 Gy of dose delivered to the probes, and random fluctuations of 4.8% in the sensitivity were observed for the three probes used in PDR and 1.9% for the probe used in HDR; and (6) the detector response was linear with dose rate. Conclusion: ZnSe:O detectors can be used effectively for in vivo dosimetry and with high accuracy for HDR and PDR brachytherapy applications. [ABSTRACT FROM AUTHOR]

A detailed kinetic model describing the consumption of key components and product distribution in the Fischer–Tropsch synthesis (FTS) over a 20%Co/0.5Re γ‐Al2O3 commercial catalyst is developed. The developed model incorporates the H2O‐assisted CO dissociation mechanism developed by Rytter and Holmen and a novel approach to product distribution modeling. The model parameters are optimized against an experimental dataset comprising a range of process conditions: total pressure 2.0–2.2 MPa, temperature 210–230°C, CO conversion range of 10%–75% and feed with and without added water. The quality of the model fit measured in terms of mean absolute relative residuals (MARR) value is 23.1%, which is comparable to literature reported values. The developed model can accurately describe both positive and negative effects of water on the rate kinetics, the positive effect of water on the growth factor, temperature and syngas composition on the kinetics and product distribution over a wide range of process conditions, which is critical for the design and optimization of the Fisher–Tropsch reactors. [ABSTRACT FROM AUTHOR]

Purpose: To report on the accuracy of an in vivo dosimetry (IVD)‐based source tracking (ST) method for high dose rate (HDR) prostate brachytherapy (BT). Methods: The ST was performed on a needle‐by‐needle basis. A least square fit of the expected to the measured dose rate was performed using the active dwell positions in the given needle. Two fitting parameters were used to determine the position of each needle relative to the IVD detector: radial (away or toward the detector) and longitudinal (along the axis of the treatment needle). The accuracy of the ST was assessed in a phantom where the geometries of five HDR prostate BT treatments previously treated at our clinic were reproduced. For each of the five treatment geometries, one irradiation was performed with the detector placed in the middle of the implant. Furthermore, four additional irradiations were performed for one of the geometries where the detector was retracted caudally in four steps of 10–15 mm and up to 12 mm inferior of the most inferior active dwell position, which represented the prostate apex. The time resolved dose measurements were retrieved at a rate of 20 Hz using a detector based on an Al2O3:C radioluminescence crystal, which was placed inside a standard BT needle. Individual calibrations of the detector were performed prior to each of the nine irradiations. Results: Source tracking could be applied in all needles across all nine irradiations. For irradiations with the detector located in the middle region of the implant (a total of 89 needles), the mean ± standard deviation (SD, k = 1) accuracy was −0.01 mm ± 0.38 mm and 0.30 mm ± 0.38 mm in the radial and longitudinal directions, respectively. Caudal retraction of the detector did not lead to reduced accuracy as long as the detector was located superior to the most inferior active dwell positions in all needles. However, reduced accuracy was observed for detector positions inferior to the most inferior active dwell positions which corresponded to detector positions in and inferior to the prostate apex region. Detector positions in the prostate apex and 12 mm inferior to the prostate resulted in mean ± SD (k = 1) ST accuracy of 0.7 mm ± 1 mm and 2.8 mm ± 1.6 mm, respectively, in radial direction, and −1.7 mm ± 1 mm and −2.1 mm ± 1.1 mm, respectively, in longitudinal direction. The largest deviations for the configurations with those detector positions were 2.6 and 5.4 mm, respectively, in the radial direction and −3.5 and −3.8 mm, respectively, in the longitudinal direction. Conclusion: This phantom study demonstrates that ST based on IVD during prostate BT is adequately accurate for clinical use. The ST yields submillimeter accuracy on needle positions as long as the IVD detector is positioned superior to at least one active dwell position in all needles. Locations of the detector inferior to the prostate apex result in decreased ST accuracy while detector locations in the apex region and above are advantageous for clinical applications. [ABSTRACT FROM AUTHOR]

Aims: The study assessed 4-year outcomes of intramyocardial injections of autologous bone marrow-derived mesenchymal stromal cells (MSCs) in patients with ischaemic heart failure.Methods and Results: The MSC-HF trial was a randomized, double-blind, placebo-controlled trial. Patients were randomized 2:1 to intramyocardial injections of MSCs or placebo. The primary endpoint was change in left ventricular end-systolic volume (LVESV), measured by magnetic resonance imaging or computed tomography. Sixty patients aged 30-80 years with ischaemic heart failure, New York Heart Association class II-III, left ventricular ejection fraction (LVEF) <45% and no further treatment options were randomized. Patients were followed clinically for 12 months and in addition 4-year data of hospitalizations and survival were retrieved. After 12 months, LVESV was significantly reduced in the MSC group and not in the placebo group, with difference between groups of 17.0 ± 16.2 mL (95% confidence interval 8.3-25.7, P = 0.0002). There were also significant improvements in LVEF of 6.2% (P < 0.0001), stroke volume of 16.1 mL (P < 0.0001) and myocardial mass (P = 0.009) between groups. A significant dose-response effect was also observed. Moreover, a significant reduction in the amount of scar tissue and quality of life score in the MSC group but not in the placebo group was observed. After 4 years, there were significantly fewer hospitalizations for angina in the MSC group and otherwise no differences in hospitalizations or survival. No side effects were identified.Conclusions: Intramyocardial injections of autologous bone marrow-derived MSCs improved myocardial function and myocardial mass in patients with ischaemic heart failure. [ABSTRACT FROM AUTHOR]

Background: Five to 10% of patients with acute myocardial infarction develop cardiogenic shock and the majority of these patients are expected to die within the first few weeks. In this study, we review our recent experience in the management of patients with cardiogenic shock complicating MI and examine the effect of early invasive revascularisation on mortality. Methods: Thirty-six consecutive patients who developed cardiogenic shock less than 48 h after MI were retrospectively evaluated and divided into two treatment groups. One group received early invasive revascularisation (n=24) and the other group had no early invasive revascularisation, but received similar conventional intensive care medical treatment (n=12). Results: Baseline characteristics and hemodynamic variables were similar in both groups. Apart from invasive revascularisation and the use of intra aortic balloon counterpulsation (IABP), treatment strategies did not differ between the two groups. Thirty-day mortality was 21% in the revascularised group of patients and 58% in the non-revascularised group (P<0.05). Conclusions: Our data support previous observations suggesting that an aggressive treatment strategy including early invasive revascularisation and IABP is associated with improved short and long-term survival in patients with cardiogenic shock. Since early revascularisation appears safe with a considerable treatment benefit, this approach must be considered in patients with short shock duration early after MI. [Copyright &y& Elsevier]

ABSTRACT An alternative parameter-free adaptive approach for the grouping of the basis function patterns in the multilevel fast multipole method is presented, yielding significant memory savings compared to the traditional Octree grouping for most discretizations, particularly when using higher-order basis functions. Results from both a uniformly and nonuniformly meshed scatterer are presented, showing how the technique is worthwhile even for regular meshes, and demonstrating that there is no loss of accuracy in spite of the large reduction in memory requirements and the relatively low computational cost. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:2451-2456, 2014 [ABSTRACT FROM AUTHOR]

The correct segmentation of a foreground object in video recordings is an important task for many surveillance systems. The development of an effective and practical algorithm to segment sows in grayscale video recordings captured under commercial production conditions is described. The segmentation algorithm combines a modified adaptive Gaussian mixture model for background subtraction with the boundaries of foreground objects, which is obtained by using dyadic wavelet transform. This algorithm can accurately extract the shapes of a sow under complex environments, such as dynamic background and illumination changes as well as motionless foreground objects. About 97% of the segmented binary images in the validation data sets can be used to track sow behaviours, such as position, orientation and movement. The experimental results demonstrate that the proposed algorithm is able to provide a basis to detect and classify the sow behaviours in farrowing pens. [ABSTRACT FROM AUTHOR]

The variation in Skeletonema cells grown at 3 klux continuous illumination and 20°C is reported. Four different types of lamps gave no difference in the photosynthetic characteristics. The average diameter of the cells decreased from 8-3.5 μ during their six months vegetative period. The ratio between the pigment content in the largest and the smallest cells was about 2:1. A good correlation between cell volume and chlorophyll a content was found for this species. The content of chlorophyll c generally varied between 4 and 17 per cent of the chlorophyll a content -- A distinct correlation between the chlorophyll a content and the rate of photosynthesis per unit of cells at low light intensity was found. The rate of photosynthesis, in mg C per mg chlorophyll a and hour at 1 klux, varied between 0.40 and 0.70 for all 60 experiments with an average value of 0.56. The corresponding value for cells deficient in phosphorus was 0.19 and for cells deficient in nitrogen 0.09. -- The material also showed a good correlation between the rate of photosynthesis per cell at 1 klux and the light-saturated rate of photosynthesis. Ik varied between 7 and 13 klux. [ABSTRACT FROM AUTHOR]

Two types with regard to adaptation to different light intensities are described: The Chlorella type and the Cyclotella type. The Chlorella type is mostly found among the green algae, the Cyclotella type among the diatoms. The Chlorella type adapts to a new light intensity mainly by changing the pigment content. Therefore the cells adapted to a high light intensity have a lower chlorophyll a content per cell than cells adapted to a low light intensity. Light saturation is mostly rather low for cells adapted to low light intensities. The light-saturated rate of photosynthesis ist mostly lower for cells adapted to a high light intensity than for cells adapted to a low light intensity. The actual photosynthesis is not much higher at a high light intensity than at a low one. The actual photosynthesis is the photosynthesis at the light intensity where the cells are grown. — The Cyclotella type adapts only by changing the light-saturated rate. The chlorophyll content is the same in cells grown at low and high light intensities. Light saturation for cells grown at a low light intensity is rather high. The light-saturated rate is much higher in the case examined at the high light intensity than at the low one. The actual photosynthesis is considerably higher for cells grown at high light intensities than for cells grown at low light intensities. — The two adaptation types are not sharply separated since transition types occur. [ABSTRACT FROM AUTHOR]

A survey of the adaptation of plankton algae in Nature to different light intensities and temperatures is given. The adaptation is always important for the plankton populations at all depths. However, the shade adaptation of the algae in the lower part of the photic zone is often of relatively little importance for the integral primary production per unit of surface, except on the by no means rare occasions when the hulk of the algae is found in this lower part. It is shown that the Ik of surface plankton during summer in the Arctic is high despite the low temperatures present. This is due to an increase of the enzyme quantities per cell. Daily fluctuations in Ik are due partly to photooxidation, partly to the fact that the periods for the production of chlorophyll and photosynthetic enzymes are mutually displaced. Despite the daily fluctuations in Ik the difference between "sun" phytoplankton and "shade" phytoplankton is distinct. [ABSTRACT FROM AUTHOR]

The theory that Skeletonema cells adapt to lower temperatures by increasing their enzyme concentration, is supported by various facts. While the rates of photo- synthesis are identical in cells adapted to different temperatures (7-20°C) the growth rate decreases with decreasing temperature and the production of organic matter increases with decreasing temperature. Further, the concentration of protein per cell and the height of the cells increase with decreasing temperature. [ABSTRACT FROM AUTHOR]

A culture of Skeletonema costatum grown at a light intensity of 3 klux and at 20°C was synchronized in diurnally intermittent illumination of 12 hour light and 12 hour dark. The culture was hardly fully synchronous as the cell division period lasted about 9 hours. The cell division started in the middle of the light period. The concentration of the pigments: chlorophyll a, chlorophyll c and fucoxanthin and the rate of light-saturated photosynthesis were followed every hour during the 24 hour period. Both the concentration of pigments and the photosynthetic activity showed a rhythmical variation. The concentration per cell of all three pigments examined increased during the development of the cells and decreased automatically during the period of cell division. An increase in the pigment concentration was found only in the light period. The rate of light-saturated photosynthesis calculated per unit of cell number increased during the cell development and decreased during (tie division period. The increase in the photosynthetic activity at light-saturation started about 4 hours after the end of cell division, which was 4 hours before the light was turned on while the increase in the concentration of chlorophyll a first started 1-2 hours after this moment. The variation in photosynthetic activity was compared with that found by other workers. The results found with Chlorella ellipsoidea by Japanese scientists (Nihei et al.) was explained as an inhibition phenomenon because the cells were not adapted to the experimental conditions. [ABSTRACT FROM AUTHOR]

In a culture of the fresh water diatom Cyclotella Meneghiniana the average cell volume decreased with time due to reduction of the diameter of the valves. The rate of photosynthesis as a function of light intensity was determined for cells with different average cell volume and the chlorophyll a concentration in the cells was measured at the same time. It was found that the concentration of chlorophyll a in the different cells was approximately constant and independent of the cell volume. The rate of photosynthesis per number of cells at a light intensity of 1 Klux was nearly constant and this was also the case for the rate of photosynthesis calculated per unit of chlorophyll a at 1 Klux. The light saturated rate of photosynthesis per number of cells decreased with decreasing cell volume, but only slightly compared to the reduction in cell volume. The rate of photosynthesis per chlorophyll a and hour at a light intensity of 1 Klux varied in the experiments with Cyclotella between 0.28 and 0.41 mg C. The values are in good agreement with the determinations in green leaves deficient in chlorophyll and with determinations on Chlorella vulgaris carried out by other authors. It is suggested that the invariability of the chlorophyll a content in the cells with varying cell volume is due to a decrease in the cell vacuole with decreasing cell volume while the volume of cytoplasma in the cells is nearly unchanged. [ABSTRACT FROM AUTHOR]

Light-photosynthesis curves for cells adapted to 3 Klux and 30 Klux respectively, were studied using the freshwater diatom Cyclotella Meneghiniana. The initial slope of the curves for the two light intensities was the same which is due to the same concentration of chlorophyll in cells grown at 3 and 30 Klux. The light saturated rate per cell was about 40 per cent higher in 30 Klux-cells than in 3 Klux-cells. The amplitude in light adaptation was found to be rather small in Cyclotella. Ik for the light-photosynthesis curves for 3 Klux- and for 30 Klux-cells was 9 Klux and 12 Klux, respectively. In Chlorella vulgaris a much wider amplitude is found. The corresponding IK-values are 4 Klux and 13 Klux. The light adaptation from one light intensity (3 Klux) to another (30 Klux) or back again was found to be a rather rapid process. Already after 24 hours the adaptation to the new light intensity was complete. Cells of Cyclotella were found to be able to withstand light of very high intensity. Cells adapted to 3 Klux and placed at 30 Klux for three hours did not exhibit any of the inhibition of the rate of photosynthesis shown by cells of Chlorella vulgaris. On the contrary the light saturated rate goes up to a level about 30 per cent higher than that for the 3 Klux and place at 30 Klux for three hours did not exhibit any of the inhibition of the rate of photosynthesis shown by cells of Chlorella vulgaris. On the contrary the light saturated rate goes up to a level about 30 per cent higher than that for the 3 Klux-cells. Towards light intensities of 60 or 100 Klux cells of Cyclotella react in a similar way. No inhibition of the rate of the photosynthesis was found at these very high light intensities either. [ABSTRACT FROM AUTHOR]

Paper chromatograms of ether and ethanol extracts of cells of the three algal species: Chlorella vulgaris, Scenedesmus quaddricauda and Chlamydomonas reinhardi were tested on agar plates with the bacteria Bacillus subtilis. Inhibition zones were found at the starting line of the paper chromatograms as well as at the solvent front. The inhibition zone at the starting line only occurred after illumination and was due to a light-induced transformation of chlorophyllides. The inhibition zones at the solvent front were caused by two different kinds of substances. The first substance was, like chlorophyllides, a derivative of chlorophylls and only showed inhibiting action after illumination. The second substance had no relation to plant pigments. In extracts from Chlamydomonas it acted only after illumination, but in extracts from Chlorella and Scenedesmus it produced inhibition zones both in the light and the dark. By extraction of culture solutions from the three algal species chlorophyllides were found in the extracts which produced substances inhibiting the growth of Bacillus subtilis both in dark and light. It is suggested that chlorophyllides play a part as an antibacterial substance in natural waters. [ABSTRACT FROM AUTHOR]

Curves showing the rate of photosynthesis as a function of light intensity are presented for Chlorella vulgaris growing at a constant light intensity of either 3 or 30 Klux. The rate is given a) per number of cells, b) per unit of weight of chlorophyll (a + b), and c) per unit of wet volume or unit of weight of dry matter. At an illumination of about 3 Klux the average cell size is at its maximum. At the same time the content of chlorophyll per cell is maximal and the content of enzymes active in photosynthesis is very nearly maximal. If we increase the illumination the cell size decreases. At the same time the content of active enzymes per cell increases slightly, but the content of chlorophyll per cell decreases. If we decrease the illumination (from 3 Klux) cells are produced with the maximum content of chlorophyll but decreasing content of enzymes active In photosynthesis. At the same time the cell size decreases. Growth rates at the two light intensities are computed by means of the measured rates of photosynthesis and respiration. They are identical with the growth rates measured by means of the increase in number of cells. After a shift from 3 Klux to 30 Klux it takes only 24 hours before the ratio chlorophyll a+b: dry weight has changed to that normally found at the high light intensity. The same is true concerning the cell size. When shifting from 30 Klux to 3 Klux it takes a little longer. However, a chlorophyll concentration nearly as high as that ordinarily found at 3 Klux was measured. About 36 hours after the shift from 30 Klux to 3 Klux, or vice versa, the shape of the curve giving the rate of photosynthesis as a function of light intensity approaches that characteristic of algae grown constantly at the new light intensity. If Chlorella grown constantly at 30 Klux are transferred to the dark for 22 hours the shape of the tight photosynthesis curve is only moderately changed. IK decreases from 13 to 9 Klux. If instead the algae are transferred to 3 Klux, IK is decreased to 5 Klux after 22 hours. The importance is stressed of using such dilute concentrations of algae in experiments of both growth and photosynthesis that no self shading takes place. [ABSTRACT FROM AUTHOR]

Filtered culture solutions from cultures of different unicellular algae, especially Chlorella vulgaris, were tested for content of growth affecting substances using the bacteria Staphylococcus aureus as test organism. Either a decrease or an increase of the growth of the bacteria could be found. It was observed that both growth accelerating and growth inhibiting substances were present simultaneously in the culture solution and that the concentration of the substances varies a great deal in cultures of the same algal species even if the cultures were grown under apparently identical conditions. In one of the experiments the inhibiting effect was decreased by heating the algal filtrate at 70°C for 20 min. In another experiment at least two inhibitors were found. One was inactivated by illumination of the algal filtrate, a second was absorbed to Norit. [ABSTRACT FROM AUTHOR]

The growth of Staphylococcus aureus together with some bacteria isolated from contaminated algal cultures was studied in daylight and in light from fluorescent and incandescent lamps and compared with the growth in the dark. Light from incandescent lamps was found to have no effect on the growth of the bacteria. Daylight and fluorescent light had a distinct inhibiting effect on the growth rate of the bacteria studied. It is suggested that the effect may be due to light in the violet region of the spectrum. [ABSTRACT FROM AUTHOR]

Experiments were carried out with algae in mixed cultures (two species cultures) or with algae cultured in filtrates from cultures of other algae or the same species. In experiments with Asterionella formosa and Nitzschia palea it was shown that both species formed substances which inhibited the growth of the other species and that the rate of inhibition was very dependant on the experimental circumstances. It was shown further that Nitzschia formed autotoxic substances and it was suggested that Asterionella formed substances which accelerated the growth of other Asterionella cells and of Nitzschia in some cases. In experiments where Nitzschia was cultured in filtrates from Scenedesmus quadricauda and Chlorella pyrenoidosa cultures, it was shown that Scenedesmus formed substances which considerably inhibited the growth of Nitzschia. The growth of Nitzschia was not inhibited in filtrates from a 4-8 days old Chlorella culture but was distinctly so in filtrates from a 13-17 days old Chlorella culture. When Chlorella was cultured for 3 days in filtrates from a 21 days old Scenedesmus culture a marked inhibition of the growth was found. During 3 days of culturing of Chlorella in filtrate from a 21 days old Nitzschia culture an acceleration of the growth of Chlorella took place. Similarly an inhibition of the growth was found when Scenedesmus was cultured for 3 days in filtrates from a 21 days old Scenedesmus culture. On the other band, an acceleration of the growth of Scenedesmus took place when it was cultured in filtrates from a 21 days old Chlorella and a 21 days old Nitzschia culture, respectively. [ABSTRACT FROM AUTHOR]

Investigations of the plankton diatoms in lakes and planktonic and epiphytic diatoms in cultures have shown that the silica content in the cells depends on the number of cells, and the silica content is inversely proportional to the number of cells. This is the case both in ordinary cultures where the Si-concentration and the concentration of other nutrient salts are decreasing when the number of cells increase and in cultures with a flowing culture solution. The decrease in the silica content is probably caused by diatoms giving off a substance to the water which inactivates the silica assimilation. [ABSTRACT FROM AUTHOR]

Experiments carried out with the diatoms Nitzschia linearis and Thalassiosira nana show that the silicon in the cell walls is soluble in water and that the rate of solubility depends on the pH of the solution. The rate increases with increasing pH. At pH 8 not much more than 5 per cent of the silicon in the cells was dissolved in both species during the experiments, at pH 10 Thalassiosira was dissolved completely. In the case of Nitzschia linearis 20 per cent of the silicon was dissolved at pH 10 during the experiment. Thus the silicon compounds are found in the diatom cells in forms which arc hydrolyzed at different rates. The silicon compounds in Thalassiosira are easy to hydrolyze at pH 10. In Nitzschia linearis some parts are easy to hydrolyze, others very difficult. [ABSTRACT FROM AUTHOR]

By cultivation on a red cabbage medium wood-rotting fungi are easily classified into those which produce polyphenol oxidase and those which do not, Polyphenol oxidase producing species change the original purple colour of the medium into yellow; the other species of wood-rotting fungi change the colour into red, A quick method for the differentiation of these two groups is described. The reaction of these fungi to red cabbage extract is more suitable for separating them than Bavendamm's polyphenol oxidase test. [ABSTRACT FROM AUTHOR]

Two experiments with Nitzschia palea and with Bacillaria paradoxa, respectively, are described. The diatoms were cultivated in plastic containers of polystyrene. In each experiment three series with different initial Si-concentrations were carried out (0.3, 1.8, and 5.3 mg Si and 0.8, 1.8, and 5.8 mg Si per liter). 24 containers in each series were used. The growth was determined by the increase in chlorophyll content, in some cases also by the number of cells. The Si-concentrations were determined during the experiments with the methods described. In both experiments the Si-concentration decreased rapidly to a level of 30- 40 μg Si per liter independently of the initial Si-concentration, and then further uptake took place only very slowly. In Experiment 1 concentrations down to 15-20 μg Si and in Experiment 2 down to 5(0)--10 μg Si per liter were found at the termination of the experiments. The growth of Nitzschia palea (increase of chlorophyll content and number of cells) stopped or nearly stopped when the Si-concentration of 30-40 ug Si per 1 was reached. The same was the case in Experiment 2 with Bacillaria paradoxa concerning the increase of number of cells, but in this experiment on the other hand the increase in chlorophyll content continued to the termination of the experiment. Through investigations in some Danish eutrophic lakes the author found that the Si-concentration decreases to a similar level as found in the experiments, 30-40 μg Si per liter during the diatom maxima. [ABSTRACT FROM AUTHOR]