Performance relations in Capacitive Deionization systems

Capacitive Deionization (CDI) is a relatively new deionization technology based on the temporary storage of ions on an electrically charged surface. By directing a flow between two oppositely charged surfaces, negatively charged ions will adsorb onto the positively charged surface, and positively charged ions will adsorb onto the negatively charged surface. To optimize CDI design for various applications, performance relations in CDI systems have to be understood. CDI performance is determined by two factors, adsorption capacity and adsorption rate. The adsorption capacity is important for performance because only a limited amount of ions can be adsorbed onto an electrically charged surface; after the total adsorption capacity is reached the surface has to be discharged. The adsorption rate is important for performance because a higher adsorption rate results in faster removal of ions from a certain stream. The objective of this thesis is to relate the performance of a CDI unit to the specifications of the influent stream and the design aspects of the unit, such as the used electrode materials in the CDI unit. To obtain these relations, the focus in this thesis is on using electrochemical characterization techniques to obtain CDI performance in terms of charge transport, and furthermore linking this charge performance to desalination performance. By using this approach, we found that the total adsorption capacity of a CDI unit is determined by the double-layer area present in the used electrodes, where a higher double-layer area gives a higher adsorption capacity. The adsorption capacity of the double-layer area is in turn dependent on the applied potential and the chemical and physical properties of the treated water. This analysis can be used to screen for activated carbons with a high amount of double-layer area. We found that materials with a high amount of pores with a size around 1.6 nm have a high double-layer area. The adsorption rate of a CDI unit is mainly determined by the absolute conductivity of the influent stream. This relation can be used to optimize spacer and electrode thickness for various influent streams. The charge efficiency, i.e. the amount of ions adsorbed per amount of charge adsorbed, is limited by counter ion expulsion. It could be improved by placing ion-exchange membranes in front of the electrodes. By integrating all obtained relations in a mathematical model, deionization performance could be predicted for CDI systems with and without ion-exchange membranes. This model can be used to predict deionization performance for any operational condition, as well as to identify and resolve bottlenecks in the operation of the CDI system. <br/

Retrospective study in 1020 cases on the rate of surgical site infections after lacrimal surgery without prophylactic systemic antibiotics

Background/AimsData regarding the effectiveness of prophylactic systemic antibiotics (PSA) in lacrimal surgery is scarce. Therefore, we determined the postoperative surgical site infection (SSI) rate in lacrimal surgery without PSA.MethodsWe retrospectively analysed files of patients who underwent external (extDCR) or endoscopic endonasal dacryocystorhinostomy (endoDCR). We excluded patients with incomplete data (n = 68), acute a priori infection with the need for antibiotics (n = 15) and PSA post-operatively for other reasons (n = 28). Indications for surgery were canalicular stenosis (n = 51, 18.6% endoDCR vs n = 131, 19.5% extDCR), nasolacrimal duct obstruction (n = 118, 43.2% endoDCR vs n = 480, 64.3% extDCR) and mucocele/chronic dacryocystitis (n = 52, 19.0% endoDCR vs n = 187, 25.0% extDCR).ResultsIn this study, 1020 DCR surgeries were performed in 899 patients. Postoperative SSI was diagnosed in eight patients (0.8%); exclusively after extDCR (1.1% of all extDCR). No SSIs were found in endoDCR cases. The prevalence between SSI in extDCR versus endoDCR did not prove significant (n = 8/747 0.8% vs n = 0/273 0%, p = 0.13). All patients diagnosed with SSI were successfully treated with systemic oral antibiotics.ConclusionThe prevalence of SSI after DCR is low and was effectively treated with oral antibiotics. In our study, SSI occurred rarely after extDCR and was not observed after endoDCR. We conclude that lacrimal surgery is safe without the routine administration of PSA

Epigenetic alteration at the DLK1-GTL2 imprinted domain in human neoplasia: analysis of neuroblastoma, phaeochromocytoma and Wilms' tumour

Epigenetic alterations in the 11p15.5 imprinted gene cluster are frequent in human cancers and are associated with disordered imprinting of insulin-like growth factor (IGF)2 and H19. Recently, an imprinted gene cluster at 14q32 has been defined and includes two closely linked but reciprocally imprinted genes, DLK1 and GTL2, that have similarities to IGF2 and H19, respectively. Both GTL2 and H19 are maternally expressed RNAs with no protein product and display paternal allele promoter region methylation, and DLK1 and IGF2 are both paternally expressed. To determine whether methylation alterations within the 14q32 imprinted domain occur in human tumorigenesis, we investigated the status of the GTL2 promoter differentially methylated region (DMR) in 20 neuroblastoma tumours, 20 phaeochromocytomas and, 40 Wilms' tumours. Hypermethylation of the GTL2 promoter DMR was detected in 25% of neuroblastomas, 10% of phaeochromocytoma and 2.5% of Wilms' tumours. Tumours with GTL2 promoter DMR hypermethylation also demonstrated hypermethylation at an upstream intergenic DMR thought to represent a germline imprinting control element. Analysis of neuroblastoma cell lines revealed that GTL2 DMR hypermethylation was associated with transcriptional repression of GTL2. These epigenetic findings are similar to those reported in Wilms' tumours in which H19 repression and DMR hypermethylation is associated with loss of imprinting (LOI, biallelic expression) of IGF2. However, a neuroblastoma cell line with hypermethylation of the GTL2 promoter and intergenic DMR did not show LOI of DLK1 and although treatment with a demethylating agent restored GTL2 expression and reduced DLK1 expression. As described for IGF2/H19, epigenetic changes at DLK1/GTL2 occur in human cancers. However, these changes are not associated with DLK1 LOI highlighting differences in the imprinting control mechanisms operating in the IGF2-H19 and DLK1-GTL2 domains. GTL2 promoter and intergenic DMR hypermethylation is associated with the loss of GTL2 expression and this may contribute to tumorigenesis in a subset of human cancers

Results from recent detachment experiments in alternative divertor configurations on TCV

Divertor detachment is explored on the TCV tokamak in alternative magnetic geometries. Starting from typical TCV single-null shapes, the poloidal flux expansion at the outer strikepoint is varied by a factor of 10 to investigate the X-divertor characteristics, and the total flux expansion is varied by 70% to study the properties of the super-X divertor. The effect of an additional X-point near the target is investigated in X-point target divertors. Detachment of the outer target is studied in these plasmas during Ohmic density ramps and with the ion ∇B drift away from the primary X-point. The detachment threshold, depth of detachment, and the stability of the radiation location are investigated using target measurements from the wall-embedded Langmuir probes and two-dimensional CIII line emissivity profiles across the divertor region, obtained from inverted, toroidally-integrated camera data. It is found that increasing poloidal flux expansion results in a deeper detachment for a given line-averaged density and a reduction in the radiation location sensitivity to core density, while no large effect on the detachment threshold is observed. The total flux expansion, contrary to expectations, does not show a significant influence on any detachment characteristics in these experiments. In X-point target geometries, no evidence is found for a reduced detachment threshold despite a 2-3 fold increase in connection length. A reduced radiation location sensitivity to core plasma density in the vicinity of the target X-point is suggested by the measurements

CADM1 is a strong neuroblastoma candidate gene that maps within a 3.72 Mb critical region of loss on 11q23

<p>Abstract</p> <p>Background</p> <p>Recurrent loss of part of the long arm of chromosome 11 is a well established hallmark of a subtype of aggressive neuroblastomas. Despite intensive mapping efforts to localize the culprit 11q tumour suppressor gene, this search has been unsuccessful thus far as no sufficiently small critical region could be delineated for selection of candidate genes.</p> <p>Methods</p> <p>To refine the critical region of 11q loss, the chromosome 11 status of 100 primary neuroblastoma tumours and 29 cell lines was analyzed using a BAC array containing a chromosome 11 tiling path. For the genes mapping within our refined region of loss, meta-analysis on published neuroblastoma mRNA gene expression datasets was performed for candidate gene selection. The DNA methylation status of the resulting candidate gene was determined using re-expression experiments by treatment of neuroblastoma cells with the demethylating agent 5-aza-2'-deoxycytidine and bisulphite sequencing.</p> <p>Results</p> <p>Two small critical regions of loss within 11q23 at chromosomal band 11q23.1-q23.2 (1.79 Mb) and 11q23.2-q23.3 (3.72 Mb) were identified. In a first step towards further selection of candidate neuroblastoma tumour suppressor genes, we performed a meta-analysis on published expression profiles of 692 neuroblastoma tumours. Integration of the resulting candidate gene list with expression data of neuroblastoma progenitor cells pinpointed <it>CADM1 </it>as a compelling candidate gene. Meta-analysis indicated that <it>CADM1 </it>expression has prognostic significance and differential expression for the gene was noted in unfavourable neuroblastoma versus normal neuroblasts. Methylation analysis provided no evidence for a two-hit mechanism in 11q deleted cell lines.</p> <p>Conclusion</p> <p>Our study puts <it>CADM1 </it>forward as a strong candidate neuroblastoma suppressor gene. Further functional studies are warranted to elucidate the role of <it>CADM1 </it>in neuroblastoma development and to investigate the possibility of <it>CADM1 </it>haploinsufficiency in neuroblastoma.</p

DLK1 Is a Somato-Dendritic Protein Expressed in Hypothalamic Arginine-Vasopressin and Oxytocin Neurons

Delta-Like 1 Homolog, Dlk1, is a paternally imprinted gene encoding a transmembrane protein involved in the differentiation of several cell types. After birth, Dlk1 expression decreases substantially in all tissues except endocrine glands. Dlk1 deletion in mice results in pre-natal and post-natal growth deficiency, mild obesity, facial abnormalities, and abnormal skeletal development, suggesting involvement of Dlk1 in perinatal survival, normal growth and homeostasis of fat deposition. A neuroendocrine function has also been suggested for DLK1 but never characterised. To evaluate the neuroendocrine function of DLK1, we first characterised Dlk1 expression in mouse hypothalamus and then studied post-natal variations of the hypothalamic expression. Western Blot analysis of adult mouse hypothalamus protein extracts showed that Dlk1 was expressed almost exclusively as a soluble protein produced by cleavage of the extracellular domain. Immunohistochemistry showed neuronal DLK1 expression in the suprachiasmatic (SCN), supraoptic (SON), paraventricular (PVN), arcuate (ARC), dorsomedial (DMN) and lateral hypothalamic (LH) nuclei. DLK1 was expressed in the dendrites and perikarya of arginine-vasopressin neurons in PVN, SCN and SON and in oxytocin neurons in PVN and SON. These findings suggest a role for DLK1 in the post-natal development of hypothalamic functions, most notably those regulated by the arginine-vasopressin and oxytocin systems

Performance relations in Capacitive Deionization systems

Capacitive Deionization (CDI) is a relatively new deionization technology based on the temporary storage of ions on an electrically charged surface. By directing a flow between two oppositely charged surfaces, negatively charged ions will adsorb onto the positively charged surface, and positively charged ions will adsorb onto the negatively charged surface. To optimize CDI design for various applications, performance relations in CDI systems have to be understood. CDI performance is determined by two factors, adsorption capacity and adsorption rate. The adsorption capacity is important for performance because only a limited amount of ions can be adsorbed onto an electrically charged surface; after the total adsorption capacity is reached the surface has to be discharged. The adsorption rate is important for performance because a higher adsorption rate results in faster removal of ions from a certain stream. The objective of this thesis is to relate the performance of a CDI unit to the specifications of the influent stream and the design aspects of the unit, such as the used electrode materials in the CDI unit. To obtain these relations, the focus in this thesis is on using electrochemical characterization techniques to obtain CDI performance in terms of charge transport, and furthermore linking this charge performance to desalination performance. By using this approach, we found that the total adsorption capacity of a CDI unit is determined by the double-layer area present in the used electrodes, where a higher double-layer area gives a higher adsorption capacity. The adsorption capacity of the double-layer area is in turn dependent on the applied potential and the chemical and physical properties of the treated water. This analysis can be used to screen for activated carbons with a high amount of double-layer area. We found that materials with a high amount of pores with a size around 1.6 nm have a high double-layer area. The adsorption rate of a CDI unit is mainly determined by the absolute conductivity of the influent stream. This relation can be used to optimize spacer and electrode thickness for various influent streams. The charge efficiency, i.e. the amount of ions adsorbed per amount of charge adsorbed, is limited by counter ion expulsion. It could be improved by placing ion-exchange membranes in front of the electrodes. By integrating all obtained relations in a mathematical model, deionization performance could be predicted for CDI systems with and without ion-exchange membranes. This model can be used to predict deionization performance for any operational condition, as well as to identify and resolve bottlenecks in the operation of the CDI system

Dynamic Adsorption/Desorption Process Model of Capacitive Deionization

In capacitive deionization (CDI), an electrical potential difference is applied across oppositely placed electrodes, resulting in the adsorption of ions from aqueous solution and a partially ion-depleted product stream. CDI is a dynamic process which operates in a sequential mode; i.e., after a certain ion adsorption capacity has been reached, the applied voltage is reduced, and ions are released back into solution, resulting in a solution concentrated in ions. The energetic input of CDI is very small, while there are no ion-exchange materials involved that need to be replaced regularly. Here we present a dynamic process model for CDI which includes the storage and release of ions in/from the polarization layers of the electrodes. The charge and ion adsorption capacity of the polarization layers is described using the equilibrium Gouy¿Chapman¿Stern (GCS) model, while the charge transfer rate from bulk solution into the polarization layer is modeled according to Ohm¿s law, i.e., depends solely on an electric field term across a mass-transfer layer. An important element in the model is the differential charge efficiency: the effective salt removal rate relative to the electronic current, for which an analytical expression is derived based on the GCS model. We present results for the effluent salt concentration and electron current, both as function of time, based on a process model that assumes ideal mixing in the CDI unit cell. The theoretical results are in very good agreement with an example data set