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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2019

Measurement of band offsets and shunt resistance in CdTe solar cells through temperature and intensity dependence of open circuit voltage and photoluminescence

Band offsets at the back contact and front window layer in CdTe-based solar cells affect photovoltaic performance and challenge standard characterization methods. By analyzing the temperature and excitation dependence of both open circuit voltage and absolute photoluminescence intensity, we show that the effects band offsets can be separated from the effects of recombination and shunting. Solar cells were grown with MgZnO window layers and compared to cells with CdS window layers containing varying amounts of oxygen. It was demonstrated that band alignment rather than reduced recombination velocity is the reason for the success of MgZnO as a front interface contact. An assortment of thin back contact interlayers were also deposited, and a PbTe interlayer showed some promise as an Ohmic contact to the CdTe, though it appears to induce a photoconductive shunt. Finally, we show that the shunting resistance given by a standard current-voltage curve technique generally does not represent a physically meaningful quantity unless it is well below one kiloOhm square cm.

14 SOLAR ENERGY↗
DOE OSTI2015

High-Flow Arterio-Hepatic Venous Shunt in Hepatocellular Carcinoma: Use of Multi-Electrode Radiofrequency for Shunt Obliteration

Intra-tumoral arterio-hepatic venous shunting (AHVS) poses an impediment to transarterial chemoembolization of liver tumors. Not only does it present a potential hazard for systemic shunting and embolization, but also the altered flow dynamics may also result in poor delivery of drug/embolics to the target tumor bed. Current available techniques to overcome AVHS include arterial embolization (particles, coils, glue, etc.) or temporary venous occlusion using balloons. We hereby illustrate the use of radiofrequency ablation to obliterate a complex AHVS consisting of a varix-like venous aneurysm.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2018

Investigating PID shunting in polycrystalline silicon modules via multiscale, multitechnique characterization

We investigated the potential-induced degradation (PID) shunting mechanism in multicrystalline-silicon photovoltaic modules by using a multiscale, multitechnique characterization approach. Both field-stressed modules and laboratory-stressed mini modules were studied. We used photoluminescence, electroluminescence, and dark lock-in thermography imaging to identify degraded areas at the module scale. Small samples were then removed from degraded areas, laser marked, and imaged by scanning electron microscopy. We used simultaneous electron-beam induced current imaging and focused ion beam milling to mark around PID shunts for chemical analysis by time-of-flight secondary-ion mass spectrometry or to isolate individual shunt defects for transmission electron microscopy and atom-probe tomography analysis. By spanning a range of 10 orders of magnitude in size, this approach enabled us to investigate the root-cause mechanisms for PID shunting. We observed a direct correlation between recombination active shunts and sodium content. The sodium content in shunted areas peaks at the SiNX/Si interface and is consistently observed at a concentration of 0.1% to 2% in shunted areas. Analysis of samples subjected to PID recovery, either activated by electron beam or thermal effects only, reveals that recovery of isolated shunts correlates with diffusion of sodium out of the structural defects to the silicon surface. We observed the role of oxygen and chlorine in PID shunting and found that those species - although sometimes present in structural defects where PID shunting was observed - do not play a consistent role in PID shunting.

14 SOLAR ENERGY↗
DOE OSTI2019

Short-Term Oral Sorafenib for Therapy of Intratumoral Shunts of Hepatocellular Carcinoma to Enable Intraarterial Treatment

Introduction: Significant intratumoral shunts between tumor-supplying arteries and portal or liver veins are a contraindication for transarterial therapy of HCC because interventional treatment of these shunts is frequently insufficient. Sorafenib has anti-angiogenic effects and is indicated for palliative treatment of patients with HCC. Here, we report our experience with the use of sorafenib for the closure of intratumoral shunts in patients scheduled for transarterial therapy of HCC. Materials and Methods: Three patients with HCC, aged 65, 82 and 79 years, exhibited a significant intratumoral shunting from tumor artery to portal (n = 1) or liver veins (n = 2). In all cases, intratumoral shunting had already been suspected based on pre-interventional CT angiography, and DSA confirmed the shunt. Oral sorafenib (800 mg/day) was administered for at least four weeks, only and specifically to occlude the shunt. Hereafter, patients were re-evaluated by CT and DSA. Results: All patients tolerated the full prescribed dose for at least 4 weeks. In one case, therapy was prolonged with an adapted dose (400 mg/day) due to sorafenib-related hand–foot syndrome. After sorafenib treatment, CT and DSA confirmed a complete closure of intratumoral shunts for all patients. No tumor progression was observed. All three patients hereafter underwent successful transarterial treatment by TACE (n = 2) or TARE (n = 1) without complications. Progression-free survival according to mRECIST was 501, 397 and 599 days, respectively. Conclusion: Even short-term oral sorafenib seems to effectively close intratumoral shunts in patients with HCC and thus might enable transarterial treatment of these patients.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2016

Sodium accumulation at potential-induced degradation shunted areas in polycrystalline silicon modules

Here, we investigated potential-induced degradation (PID) in silicon mini-modules that were subjected to accelerated stressing to induce PID conditions. Shunted areas on the cells were identified with photoluminescence and dark lock-in thermography (DLIT) imaging. The identical shunted areas were then analyzed via time-of-flight secondary-ion mass spectrometry (TOFSIMS) imaging, 3-D tomography, and high-resolution transmission electron microscopy. The TOF-SIMS imaging indicates a high concentration of sodium in the shunted areas, and 3-D tomography reveals that the sodium extends more than 2 um from the surface below shunted regions. Transmission electron microscopy investigation reveals that a stacking fault is present at an area identified as shunted by DLIT imaging. After the removal of surface sodium, tomography reveals persistent sodium present around the junction depth of 300 nm and a drastic difference in sodium content at the junction when comparing shunted and nonshunted regions.

14 SOLAR ENERGY↗
DOE OSTI2017

The Relationship between Shunt Currents and Edge Corrosion in Flow Batteries

Shunt currents occur in electrochemical reactors like flow batteries, electrolyzers, and fuel cells where many bipolar cells that are connected in series electrically contact a mobile electrolyte through one or more common fluid distribution manifolds. Shunt currents reduce energy efficiency, and can cause unwanted side reactions including corrosion and gas generation. Equivalent-circuit models have been widely used to examine shunt currents in multi-cell electrochemical reactors. However, a detailed investigation of the interesting electrochemical processes occurring at the edges of the active areas has not been presented. In this work, the generation of shunt currents and their tendency to drive corrosion at the edges of positive electrodes in the most positive cells in a reactor stack are investigated with a comprehensive numerical model. An analytical model based on the penetration of current into a semi-infinite electrode, that can be used in conjunction with traditional equivalent-circuit models to assess the tendency for shunt currents to drive corrosion, is developed and compared to the numerical model. The models provided here can be used to set requirements on maximum allowable port currents in order to achieve a particular durability goal.

25 ENERGY STORAGE↗
DOE OSTI2016

An Approach to Endovascular and Percutaneous Management of Transjugular Intrahepatic Portosystemic Shunt (TIPS) Dysfunction: A Pictorial Essay and Clinical Practice Algorithm

Transjugular intrahepatic portosystemic shunts (TIPS) have evolved as an effective and durable nonsurgical option in the treatment of portal hypertension (PH). It has been shown to improve survival in decompensated cirrhosis and may also serve as a bridge to liver transplantation. In spite of the technical improvements in the procedure, problems occur with the shunt which jeopardizes effective treatment of the PH. Appropriate management is vital to ensure the longevity of the conduit. Shunt revision techniques include endovascular revision techniques and new shunt creation or, in the appropriate patients, alternative/rescue therapies. The ability of interventional radiologists to restore adequate TIPS function has enormous implications for quality of life with palliation, morbidity/mortality related to variceal bleeding and survival if transplant candidates can live long enough to receive a new liver. As such, it is imperative that these treatment strategies are understood and employed when these patients are encountered. In this review, the restoration of appropriate shunt function using various techniques will be discussed as they apply to a variety of clinical scenarios, based on literature. In addition, illustrative case examples highlighting our experience at an academic tertiary medical center will be included. It is the intent to have this document serve as a concise and informative reference to be used by those who may encounter patients with suboptimal functioning TIPS.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2016

Use of C-Arm Cone Beam CT During Hepatic Radioembolization: Protocol Optimization for Extrahepatic Shunting and Parenchymal Enhancement

PurposeTo optimize a C-arm computed tomography (CT) protocol for radioembolization (RE), specifically for extrahepatic shunting and parenchymal enhancement.Materials and MethodsA prospective development study was performed per IDEAL recommendations. A literature-based protocol was applied in patients with unresectable and chemorefractory liver malignancies undergoing an angiography before radioembolization. Contrast and scan settings were adjusted stepwise and repeatedly reviewed in a consensus meeting. Afterwards, two independent raters analyzed all scans. A third rater evaluated the SPECT/CT scans as a reference standard for extrahepatic shunting and lack of target segment perfusion.ResultsFifty scans were obtained in 29 procedures. The first protocol, using a 6 s delay and 10 s scan, showed insufficient parenchymal enhancement. In the second protocol, the delay was determined by timing parenchymal enhancement on DSA power injection (median 8 s, range 4–10 s): enhancement improved, but breathing artifacts increased (from 0 to 27 %). Since the third protocol with a 5 s scan decremented subjective image quality, the second protocol was deemed optimal. Median CNR (range) was 1.7 (0.6–3.2), 2.2 (−1.4–4.0), and 2.1 (−0.3–3.0) for protocol 1, 2, and 3 (p = 0.80). Delineation of perfused segments was possible in 57, 73, and 44 % of scans (p = 0.13). In all C-arm CTs combined, the negative predictive value was 95 % for extrahepatic shunting and 83 % for lack of target segment perfusion.ConclusionAn optimized C-arm CT protocol was developed that can be used to detect extrahepatic shunts and non-perfusion of target segments during RE.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2017

Balloon-Assisted Chemoembolization Using a Micro-Balloon Catheter Alongside a Microcatheter for a Hepatocellular Carcinoma with a Prominent Arterioportal Shunt: A Case Report

Although transcatheter arterial chemoembolization is one of the established treatments for hepatocellular carcinoma (HCC), it is difficult to treat HCCs with prominent arterioportal (AP) shunts because anticancer drugs and embolic materials migrate into the non-tumorous liver through the AP shunts and may cause liver infarction. We developed a novel method of balloon-assisted chemoembolization using a micro-balloon catheter alongside a microcatheter simultaneously inserted through a single 4.5-Fr guiding sheath, comprising proximal chemoembolization with distal arterial balloon occlusion. We applied this method to treat an HCC with a prominent distal AP shunt induced by previous proton beam therapy and achieved successful chemoembolization without non-tumorous liver infarction under temporal balloon occlusion of a distal AP shunt.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2022

RFB Side Effects - Shunt Currents

The various models related to fluid flow, electrochemistry and shunt current, and their interactions are reviewed, and gaps identified in the development of flow battery holistic models. In a flow battery stack, the cells are electrically connected through the manifolds via the electrolyte. This results in shunt current through the electrolyte, which is a source of loss in the battery stack. This issue is examined in depth with a mathematical method of calculating shunt current distribution, the associated losses, and strategies to mitigate shunt current losses, along with the trade-offs.

Crawford, Aladsair J.↗
DOE OSTI2014

Semi-shunt field emission in electronic devices

We introduce a concept of semi-shunts representing needle shaped metallic protrusions shorter than the distance between a device electrodes. Due to the lightening rod type of field enhancement, they induce strong electron emission. We consider the corresponding signature effects in photovoltaic applications; they are: low open circuit voltages and exponentially strong random device leakiness. Comparing the proposed theory with our data for CdTe based solar cells, we conclude that stress can stimulate semi-shunts' growth making them shunting failure precursors. In the meantime, controllable semi-shunts can play a positive role mitigating the back field effects in photovoltaics.

14 SOLAR ENERGY↗
DOE OSTI2023

Evaluation of ITER divertor shunts as a synthetic diagnostic for detachment control

Reliable diagnostics that measure the detached state of the ITER divertor plasma will be necessary to control heat flux to the divertor targets during steady state, burning plasma operation. This paper conducts an initial exploration into the feasibility of the divertor shunt diagnostic as a lightweight, robust, and real-time detachment sensor. This diagnostic is a set of shunt lead pairs that measure the voltage drop along the divertor cassette body, from which the plasma scrape-off layer (SOL) current is calculated. Using SOLPS-ITER simulations for control-relevant ITER plasma scenarios, the thermoelectric current magnitude along the SOL is shown to decrease significantly with the onset of partial detachment at the outer divertor target. Electromagnetic modelling of a simplified divertor cassette is used to develop a control-oriented inductance-resistance circuit model, from which SOL currents can be calculated from shunt pair voltage measurements. The sensitivity and frequency-response of the resulting system indicates that the diagnostic will accurately measure SOL thermoelectric currents during ITER operation. These currents will be a good measure of the detached state of the divertor plasma, making the divertor shunt diagnostic a potentially extremely valuable and physically robust sensor for real-time detachment control.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2020

Comparison of PID Shunting in Polycrystalline and Single-Crystal Silicon Modules via Multi-Scale, Multi-Technique Characterization

We used the methods we reported last year to investigate potential-induced degradation (PID). We have now applied these methods to single-crystalline silicon modules that have degraded during field deployment, as well as in minimodules stressed in the laboratory. We will compare these results to the polycrystalline results presented last year. Small cores have been removed from the modules and subjected to analysis. We use a combination of photoluminescence and dark lock-in thermography imaging, laser marking, electron-beam induced current measurements, and subsequent focused ion-beam marking to allow analysis of individual defects via time-of-flight secondary-ion mass spectrometry (TOF-SIMS) to investigate the root-cause mechanism for PID shunting. We see a direct correlation between recombination active shunts and sodium content. The sodium content in shunted areas peaks at the SiN/Si interface and is consistently observed at a concentration of 0.1%-1% in shunted areas. TOF-SIMS data taken on degraded and non-degraded single-crystalline sample areas show a similar trend as in the polycrystalline samples: more sodium is seen in the degraded areas.

14 SOLAR ENERGY↗
DOE OSTI2014

The gamma-aminobutyric acid shunt contributes to closing the tricarboxylic acid cycle in Synechocystis sp PCC 6803

A traditional 2-oxoglutarate dehydrogenase complex is missing in the cyanobacterial tricarboxylic acid cycle. To determine pathways that convert 2-oxoglutarate into succinate in the cyanobacterium Synechocystis sp. PCC 6803, a series of mutant strains, Delta sll1981, Delta slr0370, Delta slr1022 and combinations thereof, deficient in 2-oxoglutarate decarboxylase (Sll1981), succinate semialdehyde dehydrogenase (Slr0370), and/or in gamma-aminobutyrate metabolism (Slr1022) were constructed. Like in Pseudomonas aeruginosa, N-acetylornithine aminotransferase, encoded by slr1022, was shown to also function as gamma-aminobutyrate aminotransferase, catalysing gamma-aminobutyrate conversion to succinic semialdehyde. As succinic semialdehyde dehydrogenase converts succinic semialdehyde to succinate, an intact gamma-aminobutyrate shunt is present in Synechocystis. The Delta sll1981 strain, lacking 2-oxoglutarate decarboxylase, exhibited a succinate level that was 60% of that in wild type. However, the succinate level in the Delta slr1022 and Delta slr0370 strains and the Delta sll1981/Delta slr1022 and Delta sll1981/Delta slr0370 double mutants was reduced to 20-40% of that in wild type, suggesting that the gamma-aminobutyrate shunt has a larger impact on metabolite flux to succinate than the pathway via 2-oxoglutarate decarboxylase. C-13-stable isotope analysis indicated that the gamma-aminobutyrate shunt catalysed conversion of glutamate to succinate. Independent of the 2-oxoglutarate decarboxylase bypass, the gamma-aminobutyrate shunt is a major contributor to flux from 2-oxoglutarate and glutamate to succinate in Synechocystis sp. PCC 6803.

Xiong, W↗
DOE OSTI2016

Endovascular Management of Refractory Hepatic Encephalopathy Complication of Transjugular Intrahepatic Portosystemic Shunt (TIPS): Comprehensive Review and Clinical Practice Algorithm

Transjugular intrahepatic portosystemic shunt (TIPS) has evolved as an effective intervention for treatment of complications of portal hypertension. The use of polytetrafluoroethylene-covered stents have improved the patency of the shunts and diminished the incidence of TIPS dysfunction. However, TIPS-related refractory hepatic encephalopathy (rHE) poses a significant challenge. Approximately 3–7 % of patients with TIPS develop rHE. Refractory hepatic encephalopathy is defined as a recurrent or persistent encephalopathy despite appropriate medical treatment. Hepatic encephalopathy can be an extremely debilitating complication that profoundly affects quality of life. The approach to management of patients with rHE is complex and typically requires collaboration between different specialties. Liver transplantation is the ultimate treatment for rHE; however, the ongoing shortage of organ donation markedly limits this treatment option. Alternative therapies such as shunt occlusion or reduction can control symptoms and serve as a ‘bridge’ therapy to liver transplantation. Therefore, interventional radiologists play a key role in the management of these patients by offering a variety of endovascular techniques. The purpose of this review is to highlight some of these endovascular techniques and to develop a therapeutic algorithm that can be applied in clinical practice for the management of rHE.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2016

Double-Balloon-Assisted n-Butyl-2-Cyanoacrylate Embolization of Intrahepatic Arterioportal Shunt Prior to Chemoembolization of Hepatocellular Carcinoma

A case of multiple hepatocellular carcinomas with a severe intrahepatic arterioportal shunt that was successfully embolized with n-butyl-2-cyanoacrylate with coaxial double-balloon occlusion prior to transcatheter arterial chemoembolization is presented. A proximal balloon positioned at the proper hepatic artery was used for flow control, and a coaxial microballoon, positioned in the closest of three arterial feeding branches to the arterioportal shunt, was used to control the delivery of n-butyl-2-cyanoacrylate. This coaxial double-balloon technique can prevent proximal embolization and distal migration of n-butyl-2-cyanoacrylate and enable precise control of the distribution of n-butyl-2-cyanoacrylate. It could also be applicable to n-butyl-2-cyanoacrylate embolization for other than intrahepatic arterioportal shunt.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2016

Minilaparotomy-Assisted Transmesenteric-Transjugular Intrahepatic Portosystemic Shunt: Comparison with Conventional Transjugular Approach

PurposeThis study was performed to compare the intrahepatic shunt function outcome and procedural complications of minilaparotomy-assisted transmesenteric (MAT)-transjugular intrahepatic portosystemic shunt (TIPS) placement with the conventional transjugular method.MethodsThis is a retrospective review of all patients who had a MAT or conventional TIPS procedure over a 6-year period at our institute. The primary patency rate, fluoroscopy time, technical success, major procedure-related complications, and mortality data were compared between two treatment groups.ResultsWe included 49 patients with MAT-TIPS, and 63 with conventional TIPS, with an average follow-up of 21.43 months. The primary patency rates at 6 and 12 months were 82.9 and 66.7 % in the conventional TIPS group, and 81.0 and 76.5 % in the MAT-TIPS group (p = 1.000, and 0.529), respectively. There was no significant difference in technical success rate, post-procedure portosystemic pressure gradient, fluoroscopy time, and peri-procedural mortality rate between treatment groups. Major procedural-related complications were seen more frequently among MAT-TIPS patients (p = 0.012). In the MAT-TIPS group, 5 (10.2 %) patients developed post-procedure minilaparotomy, wound-related complications, and 5 (10.2 %) developed bacterial peritonitis; whereas, none of patients with conventional TIPS had either of these complications (p = 0.014).ConclusionWhile both MAT-TIPS and conventional TIPS had similar shunt primary patency rate and technical success rate, the MAT approach was associated with a significantly higher rate of minilaparotomy-related wound complications or infectious complications. These complications maybe prevented by a change in post-procedure monitoring and therapy.

62 RADIOLOGY AND NUCLEAR MEDICINE↗