Effects of anti-transpirants on transpiration and energy use in greenhouse cultivation

Greenhouse production in North-West Europe consumes a lot of energy. The energy is needed for heating the greenhouse and controlling air humidity. Transpiration of a crop increases the energy use. The aim of this study was to explore the possibilities for the application of anti-transpirants to save energy by reducing crop transpiration without reducing crop yield. Literature and model calculations were used to explore the effects of increased leaf resistances on transpiration, energy use and production in tomato, cucumber and sweet pepper. In literature a large number of compounds are described that act as anti-transpirant. A two to five fold increase in stomatal resistance can be expected from treatment with anti-transpirants. Model calculations for tomato showed that increasing the stomatal resistance (from 2 to 5 times) throughout the whole year leads to substantial yield reduction: crop growth was reduced by 6-19%, while transpiration by 15-42% and consequently energy use by 9-16%. However, in the winter period (beginning of October/end of March) the growth reduction was only 0.3-1.3%, as in this period light levels are low and CO2 concentrations in the greenhouse are relatively high. Raising the (maximum) set-point for CO2 concentration from 1000 ppm to 3000 ppm, increased the actual concentration during day-time from 892 to 1567 ppm (flue gases were the only source of CO2). When the application of anti-transpirants was combined with raising the set-point for CO2 concentration, the model showed no growth reduction due to the application of anti-transpirants, while the annual energy use was reduced by 5.5-10.4% in tomato. Similar results were obtained for sweet pepper (5-9% energy saving) and cucumber (2-5% energy saving). These model calculations show that increasing stomatal resistance by anti-transpirants during the winter period may potentially save a substantial amount of energy (2-10%), without affecting yield of vegetables such as tomato, cucumber and sweet pepper. It is concluded that increasing the stomatal resistance by anti-transpirants in wintertime may lead to substantial energy saving due to the reduced transpiration and need for humidity management, without yield reduction. Such model calculations are useful to analyse beforehand the chances of a good combination of energy saving and yield loss of a possible application. Experiments will be needed to verify the result

Anaerobic biodesulfurization of thiophenes

Distillates from crude oil such as diesel and fuel oil may contain significant amounts of dibenzothiophenes and their alkylated derivatives, containing organically bound sulfur. Combustion of those fossil fuels leads to the release of polluting sulfur dioxide into the atmosphere, where it causes 'acid rain'. Due to stricter environmental legislation and depletion of crude oil reserves with low organic sulfur contents, effective desulfurization processes are becoming increasingly important. For instance: beginning in 2005 the maximal allowable sulfur content in gas oil in the European Community will be 0.005 wt.%. Currently, the refining industry applies the energy intensive physico-chemical hydrodesulfurization (HDS) process in order to reduce the sulfur content. Due to the high costs and inherent chemical limitations associated with HDS, biodesulfurization of hydrocarbon streams might represent an attractive complementary method to obtain sufficiently low sulfur levels. Bacteria require relatively mild process conditions (pressure and temperature) and bacterial enzymes are very selective in converting target molecules.The objective of this thesis was to develop an anaerobic biodesulfurization process. The thesis is build up around the reductive desulfurization reaction presented below.Dibenzothiophene (DBT) is converted under anaerobic conditions to biphenyl and sulfide with the concomitant conversion of reduction equivalents. The caloric value of the fuel molecule is retained and the sulfur is removed specifically.Chapter 1 presents a general introduction on physico-chemical and microbiological methods to desulfurize organic sulfur compounds.In Chapter 2 the DBT mass transfer rate within hydrocarbon droplets is compared to aerobic DBT conversion rates. The apolar DBT must diffuse to the hydrocarbon/water interface where bacteria prevail. The calculated values for the DBT mass transfer rate were compared to those found for aerobic DBT conversion rates, as reported in the literature. Temperature dependent data (ranging from 20 up to 60°C) of viscosity, density, and interfacial tension of various hydrocarbon distillates were incorporated in the model. The model simulated the DBT diffusion in hydrocarbon droplets as obtained in a stirred tank reactor. Based on these calculations, we estimated that the mass transfer rate of DBT within the hydrocarbon droplet to the hydrocarbon/water interface is at least a factor 10 to 10 4higher than the specific DBT conversion rates. However, the presence of a high specific surface area is essential to enhance the surface contact between bacteria and the hydrocarbon phase.The availability of a suitable biomass is crucial to develop this new bioprocess. In Chapter 3 a screening method is described to enrich biomass from mixed bacterial populations obtained from oil-polluted environments. The enriched cultures were able to grow in the presence of thiophenes as the sole electron acceptor. A proof of principle was obtained; the formation of sulfide and biphenyl from dibenzothiophene was shown conclusively. Also thiophene and benzothiophene depletion with concomitant sulfide formation was observed. However, apart from sulfide no thiophene nor benzothiophene desulfurization products could be demonstrated. The main problem during consecutive enrichments was the loss of biological activity after transferring the desulfurizing biomass. A mixed population was present and the active desulfurizing biomass was easily overgrown by acetogenic bacteria. Therefore, it was attempted to isolate the desulfurizing bacteria. The isolation procedure resulted in the availability of highly enriched cultures able to desulfurize thiophenes when cultivated using a selective medium with H 2 as electron donor and limiting amounts of bicarbonate and acetate (1 mM each).Based on process considerations H 2 gas is the most suitable electron donor for the reductive desulfurization process. In Chapters 4 and 5 attention is paid to the mass transfer rate of H 2 in a gas/water/hydrocarbon three-phase system using n -dodecane as model solvent. Because vigorous foam formation occurs when H 2 gas is directly added to a n -dodecane in water dispersion, it was proposed to saturate the n -dodecane with H 2 gas prior to disperse it into the water phase. Experiments to determine the H 2 mass transfer coefficients involved using physical methods are described in Chapter 4. The H 2 mass transfer coefficients between the gas and the n -dodecane phase ( k d ) and between the gas and the water phase ( k w ) were determined using a dynamic method by following the pressure decline in time, whilst the overall H 2 mass transfer coefficient between n -dodecane and water ( k dw ) was determined using a steady state method. The value for k dw was assessed using tritium-hydride (T-H instead of H-H) as the tracer. The effects of the temperature (30, 40 and 50 oC) and salt concentrations (0-250 mM) were studied. The value for k w [(9.7 ± 0.2) x 10 -5ms -1at 30ºC] was found to be a factor 3.3 higher than for k d [(2.89 ± 0.12) x 10 -5ms -1at 30ºC] because of the lower viscosity of water. No effect was found for the presence of salts (up to 250 mM NaCl) on the k w -value. The k dw -value determined in the steady state experiments at 30ºC was (5 ± 0.6) x 10 -6ms -1which is 19.4 times smaller than the above-mentioned k w -value. The considerable smaller value for k dw must be attributed to the additional mass transfer resistance introduced by the second liquid phase. Calculations of the maximal attainable H 2 flux revealed values of 0.016 x 10 -3mol/m 2s and 3.9 x 10 -3mol/m 2s for a n -dodecane/water and gas/water system, respectively. Therefore, the specific surface area between n -dodecane and water is the determining parameter for sufficient H 2 mass transfer. In Chapter 5, the H 2 mass transfer is described further using a bioreactor equipped with a nozzle to create very fine n -dodecane droplets. The specific surface area is dependent on the maximum attainable hold-up of n -dodecane and the diameter of the droplets. These parameters were studied in a model system consisting of n -dodecane and water supplemented with NaCl. The use of the nozzle resulted in droplets with a Sauter mean diameter of only 10.3±0.9mm. The droplet size was found to be independent of the applied pressure drop over the nozzle. The hold-up of n -dodecane in the aqueous medium is clearly dependent on the sodium ion concentration. The hold-up decreases rapidly (from 0.14 to 0.04) with increasing sodium ion concentrations due to coagulation; from 94 mM onwards the hold-up becomes 0.04. The application of n -dodecane droplets as carrier phase for H 2 mass transfer was demonstrated in batch tests for biological sulfate reduction. During operation of the bioreactor, biomass attached to the rising n -dodecane droplets and eventually flotated from the system.In addition biological steady state experiments were performed with hydrogenotrophic sulfate reducing bacteria to determine the H 2 mass transfer coefficient for a n -dodecane/water system ( k dw ). A value of (4.0±0.24) x 10 -6ms -1was found, which is close to the values found in the experiments using tritium hydride. Final calculations showed that the volumetric H 2 mass transfer rate (mol/m 3s) from n -dodecane to water can be comparable to values found for gas lift reactors, thus the high specific surface area that can be created by applying a nozzle can overcome the lower value of the H 2 flux (mol/m 2s) to a large extent.Chapter 6 addresses the role of sulfide on anaerobic biodesulfurization. The presence of increased sulfide concentrations is undesirable because it is expected that sulfide will inhibit the DBT conversion. Therefore, insight in the partitioning of gaseous hydrogen sulfide (H 2 S) over a three-phase gas/water/hydrocarbon system is required. The partitioning of H 2 S over a gas/water/ n -dodecane system is described. Experimental results matched well with the model predictions. The effect of the presence of an extra hydrocarbon phase ( n -dodecane) notably decreased the total sulfide in the water phase and the H 2 S fraction in the gas phase. The hydrocarbon phase serves as a sink for H 2 S molecules and by scrubbing the H 2 S in a separate process step ( e.g. during H 2 saturation) the sulfide concentration can be lowered to favor the anaerobic biodesulfurization

New medical treatments for lower urinary tract symptoms due to benign prostatic hyperplasia and future perspectives

Background: Lower Urinary Tract Symptoms (LUTS) in men are a common clinical problem in urology and have been historically strictly linked to benign prostatic hyperplasia (BPH), which may lead to bladder outlet obstruction (BOO). New molecules have been approved and have entered the urologists' armamentarium, targeting new signaling pathways and tackling specific aspects of LUTS. Objective of this review is to summarize the evidence regarding the new medical therapies currently available for male non-neurogenic LUTS, including superselective α1-antagonists, PDE-5 inhibitors, anticholinergic drugs and intraprostatic onabotulinum toxin injections. Methods: The National Library of Medicine Database was searched for relevant articles published between January 2006 and December 2015, including the combination of "BPH", "LUTS", "medical" and "new". Each article's title, abstract and text were reviewed for their appropriateness and their relevance. One hundred forty eight articles were reviewed. Results: Of the 148 articles reviewed, 92 were excluded. Silodosin may be considered a valid alternative to non-selective α1-antagonists, especially in the older patients where blood pressure alterations may determine major clinical problems and ejaculatory alterations may be not truly bothersome. Tadalafil 5 mg causes a significant decrease of IPSS score with an amelioration of patients' QoL, although with no significant increase in Qmax. Antimuscarinic drugs are effective on storage symptoms but should be used with caution in patients with elevated post-void residual. Intraprostatic injections of botulinum toxin are well-tolerated and effective, with a low rate of adverse events; however profound ameliorations were seen also in the sham arms of RCTs evaluating intraprostatic injections. Conclusion: New drugs have been approved in the last years in the medical treatment of BPH-related LUTS. Practicing urologists should be familair with their pharmacodynamics and pharmacokinetics

The Connective Tissue Disorder Associated with Recessive Variants in the SLC39A13 Zinc Transporter Gene (Spondylo-Dysplastic Ehlers-Danlos Syndrome Type 3): Insights from Four Novel Patients and Follow-Up on Two Original Cases.

Recessive loss-of-function variants in SLC39A13, a putative zinc transporter gene, were first associated with a connective tissue disorder that is now called "Ehlers-Danlos syndrome, spondylodysplastic form type 3" (SCD-EDS, OMIM 612350) in 2008. Nine individuals have been described. We describe here four additional affected individuals from three consanguineous families and the follow up of two of the original cases. In our series, cardinal findings included thin and finely wrinkled skin of the hands and feet, characteristic facial features with downslanting palpebral fissures, mild hypertelorism, prominent eyes with a paucity of periorbital fat, blueish sclerae, microdontia, or oligodontia, and-in contrast to most types of Ehlers-Danlos syndrome-significant short stature of childhood onset. Mild radiographic changes were observed, among which platyspondyly is a useful diagnostic feature. Two of our patients developed severe keratoconus, and two suffered from cerebrovascular accidents in their twenties, suggesting that there may be a vascular component to this condition. All patients tested had a significantly reduced ratio of the two collagen-derived crosslink derivates, pyridinoline-to-deoxypyridinoline, in urine, suggesting that this simple test is diagnostically useful. Additionally, analysis of the facial features of affected individuals by DeepGestalt technology confirmed their specificity and may be sufficient to suggest the diagnosis directly. Given that the clinical presentation in childhood consists mainly of short stature and characteristic facial features, the differential diagnosis is not necessarily that of a connective tissue disorder and therefore, we propose that SLC39A13 is included in gene panels designed to address dysmorphism and short stature. This approach may result in more efficient diagnosis

Energiebesparing door bladplukken bij paprika: haalbaarheidsstudie op basis van modellen

Met behulp van simulatiemodellen werd een haalbaarheidsstudie uitgevoerd naar de effecten van bladplukken op energiebesparing en rendementsverbetering bij paprika. Deze studie leverde het volgende op: 蛮 Eenmalige bladpluk (van LAI=6 terug naar LAI=3) geeft een waterbesparing van 11%, een energiebesparing van 5% bij een opbrengststijging van 1%. Het netto financiële resultaat hangt sterk af van de prijzen voor gas, arbeid (voor bladplukken) en product. Voor de berekeningen die het meest overeenkomen met huidig prijspeil schatten wij dat het financiële resultaat ligt tussen € 1050, - winst per hectare (bij een uurloon van € 15,- ) en € 820,- verlies per hectare (bij een uurloon van € 20,-). 蛮 Het gunstigste moment voor bladplukken is in augustus. 蛮 Deze resultaten zijn gebaseerd op de klimaatinstellingen van een teler die nu reeds energiezuinig teelt. Een gemiddelde tuinder gebruikt 10% meer energie, maar de berekende resultaten van bladplukken zijn vergelijkbaar. 蛮 Wekelijks bladplukken lijkt minder perspectiefvol. Weliswaar is de energiebesparing dan groter (8%), maar het positieve effect op productie is kleiner. De kosten voor bladplukken zullen naar verwachting hoger zijn. De resultaten zijn op 11 december 2003 besproken met de tuinders in een vergadering van de Landelijke commissie paprika van LTO. Daarbij is gediscussieerd over de toepassingsmogelijkheden in de praktijk en hebben we de tuinders gevraagd of ze perspectief zien in een nadere toetsing in de praktijk. De tuinders ondersteunen een praktijktoetsing, waarbij ze enkele randvoorwaarden hebben aangegeven. De reacties van de tuinders zijn weergegeven in dit rapport

Modelling the effect of the position of cooling elements on the vertical profile of transpiration in a greenhouse tomato crop

Semi-closed greenhouse management may increase greenhouse productivity. However, it relies on the application of mechanical cooling. Cooling can be applied from above or below the canopy. The positioning of the cooling affects the vertical climate profile in the canopy. In order to determine how this affects the vertical profile of transpiration and crop temperature, in this work we used the energy balance of different crop layers to develop a modified “big leaf” model for its temperature and transpiration. The model was validated with data from a large greenhouse experiment (tomato) where the position of cooling elements and climate set-points ensured different vertical profiles of air properties. In particular, we had the combination of two positions of cooling elements (above and below the crop) and two temperature set-points; and a control (not cooled and naturally ventilated) compartment. For the validation we used measurements of crop temperature at different heights in the canopy and of transpiration of the whole crop. Finally we used the model to determine and discuss the effect of the various types of air conditioning on the vertical profile of transpiration within the crop. The compartment with natural ventilation had the highest simulated transpiration (which agreed with the measurements) and the largest uniformity of distribution of transpiration among layers. The least homogeneous distribution was with the cooling elements below, which had also the smallest total transpiration, which was 95% of the transpiration of the crop cooled from above

Efficiency of light energy used by leaves situated in different levels of a sweet pepper canopy

In order to make the most use of the available light in glasshouse crops, measurements of light penetration, leaf photosynthesis, respiration and transpiration were performed at five levels in a sweet paper canopy at two commercial farms, from July to November 2004. Light response curves of leaf photosynthesis showed that photosynthesis, transpiration respiration decreased from top to bottom in the canopy. These reductions in gas exchange lower in the canopy likely result from adaptation to lower ambient light conditions as well as leaf aging. At a low light intensity of 50 µmol m-2 s-1 above the canopy, the net photosynthesis in the top 25% of the leaves (2 m2 m-2 ) was positive, while at a higher light irradiance, 200 µmol m-2 s-1, the top 50% (4 m2 m-2) was positive. From the middle of August onwards, the net photosynthesis of the lower half of the crop was negative. Based on these measurements, the contribution of each leaf level to the net crop photosynthesis and transpiration was calculated. On an annual basis, the lower half of the crop made a 0.5% negative contribution to net photosynthesis, while making a 10% positive contribution to crop transpiration. Thus, removal of leaves from the lower levels might increase the efficiency of energy utilization. In this contribution, participation of leaves from different part of the canopy in crop photosynthesis and transpiration were quantified and discussed in relation to growth, production and energy utilizatio

Reductie van verdamping door verhoging van bladweerstand middels anti-transparanten

In deze verkennende studie is geïnventariseerd wat de perspectieven van antitransparanten zijn om energie te besparen in de glastuinbouw. Doelstelling was om na te gaan of een energiebesparing van 5-10% haalbaar is, bij tenminste gelijkblijvende opbrengst. Dit is gedaan voor de gewassen tomaat, paprika en komkomme

Delegating Clozapine Monitoring to Advanced Nurse Practitioners:An Exploratory, Randomized Study to Assess the Effect on Prescription and Its Safety

To test whether: (1) psychiatrists will prescribe clozapine more often if they can delegate the monitoring tasks to an advanced nurse practitioner (ANP), (2) clozapine monitoring by an ANP is at least as safe as monitoring by a psychiatrist. Patients from 23 Dutch outpatient teams were assessed for an indication for clozapine. ANPs affiliated to these teams were randomized to Condition A: clozapine monitoring by an ANP, or Condition B: monitoring by the psychiatrist. The safety of monitoring was evaluated by determining whether the weekly neutrophil measurements were performed. Staff and patients were blinded regarding the first hypothesis. Of the 173 patients with an indication for clozapine at baseline, only seven in Condition A and four in Condition B were prescribed clozapine (Odds Ratio = 2.24, 95% CI 0.61-8.21; p = 0.225). These low figures affected the power of this study. When we considered all patients who started with clozapine over the 15-month period (N = 49), the Odds Ratio was 1.90 (95% CI 0.93-3.87; p = 0.078). With regard to the safety of the monitoring of the latter group of patients, 71.2% of the required neutrophil measurements were performed in condition A and 67.3% in condition B (OR = 0.98; CI = 0.16-3.04; p = 0.98). Identifying patients with an indication for clozapine does not automatically lead to improved prescription rates, even when an ANP is available for the monitoring. Clozapine-monitoring performed by an ANP seemed as safe as that by a psychiatrist