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Impact of string connection and contact defects on electrical current distribution in solar cells and modules: a model validated by magnetic field imaging
No full textModeling of solar modules and their components is essential to quantify geometrical, optical, and electrical losses and to improve the designs and technologies in terms of performance. In most loss analysis models, the current share among the busbars of the solar cell is assumed to be equal since a symmetrical distribution of the metallization is given. The impact of string terminal connection on the current distribution among the ribbons and the resulting changes in ohmic losses has not been studied yet. In this study, a MATLAB model is developed to consider the impact of the string connector terminal position on the current distribution and the ohmic losses in the ribbons and in string connector. The model allows for the analysis of the impact of contact defects scenarios in ribbons and string connectors on the current distribution. Results show that the highest current flows at the closest busbar to the string connector terminal while the current decreases at the busbars farther away from the terminal due to higher ohmic resistance of the current path. The higher the ohmic resistance of the string connector, the more inhomogeneous the current share at busbars. Simulating a 9 busbar M6 half-cell with 1 × 0.08 mm2 string connector, positioning the string connector terminal at the leftmost or rightmost ribbon results in 0.4 W less power compared to center connection configuration, where the string connector terminal is positioned at the center ribbon. Furthermore, simulation results show that inhomogeneity of current causes about 2.1% reduction in module power compared to the case of evenly distributed cell current, considering a 120-haf-cell module with the same string connector. Regarding contact defect analysis, exemplary simulations show the impact of the position of detached ribbons on the power or efficiency loss. Considering left or right connection configuration, detaching the leftmost or rightmost ribbon results in higher power loss compared to other ribbons. Detaching one cell ribbon completely from the string connector results in about 0.2%abs decrease in cell efficiency, while detaching the outer ribbon along all strings of a 120-half-cell module results in power loss of about 0.8%. The developed model is validated by performing magnetic field imaging (MFI) measurements, in which the magnetic flux density induced by the current carried by the ribbons is measured
Measuring psychotherapist functioning with the Therapist Work Involvement Scales (TWIS): reliability, factor structure, and measurement invariance
No full textObjectivesThe Therapist Work Involvement Scales (TWIS) is a self-report research instrument that enables a multilayered description of psychotherapists’ experiences when treating clients. The TWIS was created in a comprehensive study of close to 5,000 psychotherapists, and has been used in multiple studies. The aim of the current paper is to clarify the organization and statistical characteristics of the TWIS, and to present an updated version for longitudinal and cross-sectional research.MethodsCollection of a large sample of psychotherapy trainees made possible the use of confirmatory factor analysis (CFA) to evaluate the dimensions and structure of therapists’ process experiences, assessing reliabilities, measurement invariance over gender, item statistics, and correlations with other measures to show concurrent and predictive validity.ResultsThe CFAs largely confirmed the factor structure of four of the five facets, and of the global super-factors. The global factors of Healing Involvement and Stressful Involvement each showed substantial correlations with therapists’ attachment style and professional growth, and were used to describe four practice patterns that typify the experiences of therapists.ConclusionThe results have shown the TWIS to be a statistically sound, multidimensional research instrument enabling therapists to describe their experience in current therapeutic work
C-reactive protein orchestrates acute allograft rejection in vascularized composite allotransplantation via subset-selective monocyte activation
No full textIntroductionDespite advancements in transplant immunology and vascularized composite allotransplantation (VCA), the longevity of allografts remains hindered by the challenge of allograft rejection. The acute-phase response, an immune-inflammatory reaction to ischemia/reperfusion that occurs directly after allogeneic transplantation, serves as a catalyst for graft rejection. This immune response is orchestrated by acute-phase reactants through intricate crosstalk with the mononuclear phagocyte system.ObjectiveC-reactive protein (CRP), a well-known marker of inflammation, possesses pro-inflammatory properties and exacerbates ischemia/reperfusion injury. Thus, we investigated how CRP impacts acute allograft rejection.MethodsPrompted by clinical observations in facial VCAs, we employed a complex hindlimb transplantation model in rats to investigate the direct impact of CRP on transplant rejection.ResultsOur findings demonstrate that CRP expedites allograft rejection and diminishes allograft survival by selectively activating non-classical monocytes. Therapeutic stabilization of CRP abrogates this activating effect on monocytes, thereby attenuating acute allograft rejection. Intravital imagining of graft-infiltrating, recipient-derived monocytes during the early phase of acute rejection corroborated their differential regulation by CRP and their pivotal role in driving the initial stages of graft rejection.ConclusionThe differential activation of recipient-derived monocytes by CRP exacerbates the innate immune response and accelerates clinical allograft rejection. Thus, therapeutic targeting of CRP represents a novel and promising strategy for preventing acute allograft rejection and potentially mitigating chronic allograft rejection
Close-to-nature management of tropical timber plantations is economically viable and provides biodiversity benefits
No full textThree‐dimensional radial echo‐planar spectroscopic imaging for hyperpolarized 13C MRSI in vivo
No full textPurposeTo demonstrate the feasibility of 3D echo-planar spectroscopic imaging (EPSI) technique with rapid volumetric radial k-space sampling for hyperpolarized (HP) 13C magnetic resonance spectroscopic imaging (MRSI) in vivo.MethodsA radial EPSI (rEPSI) was implemented on a 3 T clinical PET/MR system. To enable volumetric coverage, the sinusoidal shaped readout gradients per k-t-spoke were rotated along the three spatial dimensions in a golden-angle like manner. A distance-weighted, density-compensated gridding reconstruction was used, also in cases with undersampling of spokes in k-space. Measurements without and with HP 13C-labeled substances were performed in phantoms and rats using a double-resonant 13C/1H volume resonator with 72 mm inner diameter.ResultsPhantom measurements demonstrated the feasibility of the implemented rEPSI sequence, as well as the robustness to undersampling in k-space up to a factor of 5 without advanced reconstruction techniques. Applied to measurements with HP [1-13C]pyruvate in a tumor-bearing rat, we obtained well-resolved MRSI datasets with a large matrix size of 123 voxels covering the whole imaging FOV of (180 mm)3 within 6.3 s, enabling to observe metabolism in dynamic acquisitions.ConclusionAfter further optimization, the proposed rEPSI method may be useful in applications of HP 13C-tracers where unknown or varying metabolite resonances are expected, and the acquisition of dynamic, volumetric MRSI datasets with an adequate temporal resolution is a challenge
Ultraschallschweißen von Al/Cu-Verbindungen: Bindungsbildung, Sonotrodenverschleiß und ihre Wechselwirkungen
No full textDas Metall-Ultraschallschweißen (USMW) ist eine gängige Fügetechnologie zur elektrischen Kontaktierung von Lithium-Ionen-Zellen aufgrund seiner Vorteile beim Fügen artfremder, leitfähiger und dünnwandiger Materialien im festen Zustand. Im Rahmen dieser Arbeit wurde dieses Schweißverfahren anwendungsnah jedoch grundlagenorientiert zur Herstellung der Al/Cu-Mischverbindung untersucht. Anhand von licht- und rasterelektronenmikroskopischen Untersuchungen wurde die Bindungsbildung sowie die durch den Schweißprozess bedingten mikrostrukturellen Veränderungen umfassend charakterisiert. Die hochauflösende Prozesscharakterisierung erfolgte durch zeitgleiche Ermittlung kinematischer und thermischer Prozessgrößen. Auf diesen Grundlagen wurde ein Prozessphasenmodell für das USMW abgeleitet. Für die Verschleißuntersuchung wurde anschließend ein neuartiges HochfrequenzPrüfsystem auf Basis eines Schweißsystems umgebaut und eingesetzt. Die quantitative Beschreibung des Verschleißzustandes erfolgte anhand von lichtmikroskopischen Aufnahmen und moderner Bildverarbeitungstechnik. Die Auswirkungen des Sonotrodenverschleißes auf den Schweißprozess und auf die Verbindungsqualität wurden mit einer „künstlich“ verschlissenen Sonotrode untersucht. Durch die Verwendung alternativer Sonotrodenwerkstoffe und die Anpassung von Prozessparametern kann die Standzeit der Sonotrode mit identischer Verbindungsqualität prinzipiell verlängert werden
Theoretical studies investigating the mechanism of methanol formation over Cu/ZnO based catalysts - raw data
No full textIn this work, the full mechanism of methanol formation on model Cu8 cluster supported on reconstructed ZnO is analysed using periodic plane wave DFT techniques. Activation barriers, stabilities, adsorption sites, reaction energies and vibrations are reported and provide key insights into MeOH complex formation, investigating primarily the interfacial Cu/ZnO site, expected to be the active site for MeOH synthesis. On Cu/ZnO (CZ), enhanced CO2 adsorption and activation are found at the active Cu/ZnO interfacial site – resembling a VO vacancy – compared to sites on other Cu-based systems. The results indicate that MeOH formation follows the formate mechanism: CO2*→ HCOO*→ H2COO*→ H2COOH*→ H2CO*→ H3CO*→ H3COH. Several formate adsorbates, some of which are highly stable and therefore act as spectators observed spectroscopically, were reported, thus formate on the interfacial site is depicted as an intermediate that can further react to form MeOH. Methoxy's high stability is key to its role as an intermediate seen in experiments, thus its destabilization is key to enhance methanol formation, or its stabilization leads to other paths like H2COH* hydrogenation helping MeOH formation. On CZ, the most energy-demanding elementary process is the hydrogenation of MeO* to MeOH (Ea = 1.20 eV). Furthermore, the role of CO and H2CO* as scavengers of surface O*, which poisons the active site, is analysed. Finally, water is expected to form from O* on a pure Cu site only, independently of the interfacial site Cu/ZnO, the site for MeOH production.The introduction of Al on the CZ system (= CZA), approximated by substituting a single bulk-like Zn atom with Al, is investigated with focus on its electronic repercussion. Due to Al, CO2 adsorption and activation are enhanced at the active Cu/ZnO interfacial site, in comparison to Cu-based systems and the CZ system. Al changes the MeOH formation mechanism therefore following CO2*→ HCOO*→ H2COO*→ H2COOH*→ H2CO*→ H2COH*→ H3COH. MeO* bonds more strongly to the interfacial site, making it a dead-end, compared to its intermediate nature on CZ. Aluminium seems to help selectivity by destabilizing formate on the active site (reducing poisoning character), thus stabilizing other sites as seen experimentally. The most energy demanding step is the hydrogenation of HCOO* to H2COO* (Ea = 1.13 eV) on CZA, in contrast to methoxy hydrogenation on CZ. Multiple species can scavenge O* from the interfacial site leading to a regenerative active site. Even though, OH* can poison the active site, its formation is difficult in general, making the catalyst more selective to MeOH synthesis on CZA than on CZ. Water seems to form on the Cu site as in the CZ system, though Zn sites become important to stabilize water, mimicking the experimental behaviour of the CZA systems. Al shows particular features to enhance selectivity of methanol formation, by specifically stabilizing some intermediates (formate, methoxy, water)
Outer retina micro-inflammation is driven by T cell responses prior to retinal degeneration in early age-related macular degeneration
No full textIntroduction: Age-related macular degeneration (AMD) is a leading cause of blindness with limited treatment options. Dysfunction of the retinal pigment epithelium (RPE) is a unifying salient feature of the pathology and a primary end-point damage leading to complications such as geographic atrophy (GA), which represents the most common end-stage of AMD.Methods: Human and murine ocular tissues were used for histological examinations. Furthermore, flow cytometry and gene expression analysis were used on ocular and splenic tissues of Cx3cr1GFP/GFP and C57BL/6J mice at 8 and 12 months of age to characterize the dynamics of local and systemic T cell populations.Results: We show the presence of memory T cells such as CD45RO+ cells in the choroid and retina of patients with AMD with a peak of abundance in early stages of AMD. As further evidence for the contribution of the adaptive immune system to GA we identified an increased frequency of CD44+ CD69+ KLRG1+ T cells and para-inflammation of the retina in a mouse model that mimics features of GA. Importantly, the activation of T cells found at early AMD-like stages prior to degeneration possessed long-lasting cytotoxic properties and adopted typical features of senescent immune cells. T cells were intimately associated with the RPE, suggesting transmigration and participating in local micro-inflammation.Discussion: Our data support that activation and accumulation of memory T cells can be considered as a hallmark of early AMD, and that adaptive immunosenescence likely to contribute to the chronic inflammation associated with RPE damage and the progression to large lesions as seen in GA
