INFLUENCE OF LIGHT ABSORPTION PROFILE ON THE PERFORMANCE OF ORGANIC PHOTOVOLTAICS

We investigate how an enhanced light absorption at a specific position inside the active layer affects the performance of organic photovoltaic cells (OPVs), namely the short-circuit current density ( ), the open-circuit voltage ( ), the fill factor (FF), and the power conversion efficiency (PCE). The performance is calculated using an updated version of a previously published analytical current-voltage model for OPVs, where the updated model allows the light absorption profile to be described by any functions provided that analytical solutions can be produced. We find that the light absorption profile affects the performance through the drift current. When the mobility imbalance is not very high (when the ratio of the mobility of the faster carrier type to the mobility of the slower carrier type is less than about ), the PCE is maximized when the light absorption is concentrated at the center of the active layer. When the mobility imbalance is very high (when the ratio of the mobility of the faster carrier type to the mobility of the slower carrier type is more than approximately ), the PCE is maximized when the light absorption is concentrated near the electrode collecting the slower carrier type. Therefore, it is important to ensure that the light absorption profile is properly tuned so that the performance of OPVs is maximized. Moreover, any efforts that we make to improve the performance should not lead to a light absorption profile that would actually impair the overall performance. ABSTRAK: Kajian ini menilai bagaimana penyerapan cahaya yang tinggi pada bahagian tertentu lapisan aktif mempengaruhi prestasi sel fotovoltaik organik (OPV), iaitu ketumpatan arus litar pintas (Jsc), voltan litar terbuka (Voc), faktor pengisian (FF), dan kecekapan penukaran kuasa (PCE). Prestasi dikira mengguna pakai model terkini yang diperbaharui dari model asal analitikal OPV voltan-arus, di mana model ini membenarkan mana-mana profil penyerapan cahaya digunakan asalkan penyelesaian analitikal terhasil. Dapatan kajian mendapati profil penyerapan cahaya mempengaruhi prestasi berdasarkan arus hanyut. Apabila ketidakseimbangan pergerakan caj tidak begitu tinggi (di mana nisbah pergerakan pembawa caj laju kepada perlahan adalah kurang daripada 103), PCE menjadi maksimum jika penyerapan cahaya bertumpu pada tengah lapisan aktif. Apabila ketidakseimbangan pergerakan caj sangat tinggi (di mana nisbah pergerakan pembawa caj laju kepada perlahan adalah lebih daripada 104), PCE menjadi maksimum jika penyerapan cahaya bertumpu pada elektrod yang mengutip pembawa caj perlahan. Oleh itu, kedudukan talaan profil penyerapan cahaya yang tepat adalah sangat penting bagi menentukan prestasi OPV dimaksimumkan. Tambahan, apa sahaja usaha penambahbaikan prestasi seharusnya tidak menyebabkan pengurangan keseluruhan prestasi profil penyerapan cahaya.

Kinetics of Iron Absorption From Ferrous Fumarate With Galacto-oligosaccharides Measured by Stable-isotope Appearance Curves in Iron Depleted Women in Switzerland

Objectives Prebiotic galacto-oligosaccharides (GOS) have shown promising results in enhancing the absorption of oral supplemental iron in form of ferrous fumarate (FeFum) in iron depleted adults. The mechanism behind this effect is unknown. We aimed to assess the absorption profile of FeFum given with and without GOS using stable isotope appearance curves (SIACs). Methods We conducted a controlled, single-center, prospective cross-over trial in iron depleted women between Sept and Nov 2019 at the Laboratory of Human Nutrition, ETH Zurich, Switzerland. All women (n = 11; median SF = 15.2 µg/L) received two supplemental iron doses of 14 mg in form of FeFum containing 6 mg of isotopic tracers (57Fe or 58Fe). The supplemental iron doses were administered in random order on d 1 and 15 after an overnight fast. The supplement combinations were: 1) 57FeFum + 300 ml water; and 2) 58FeFum + 15 g GOS + 300 ml water. Eleven blood samples were collected up to 24 h after administration of the iron supplements to determine serum iron appearance. Fractional iron absorption (FIA) of the isotopic tracers was calculated in whole blood collected 14 days after administration of each of the supplemental iron doses on the basis of the shift in iron isotope ratios according to the principle of isotope dilution. Results There was a trend towards increased FIA and total absolute AUC of the SIAC from FeFum given with 15 g GOS compared to without (P = 0.064; P = 0.080 respectively). Estimated timepoints of the peak serum isotope concentration were not different (P = 0.096). Relative SF and relative bioavailability correlated significantly (P = 0.037). In subjects with a lower SF the increase in bioavailability of iron when given with GOS was more pronounced compared to participants with higher SF. Conclusions Adding 15 g GOS to FeFum did not result in a different absorption profile compared to without GOS. The enhancing effect of GOS seems to depend on iron status, even though overall the improvement of iron absorption when given with 15 g GOS did not reach significance, probably due to the small sample size. Since women with a low iron status can benefit the most from an increase in iron bioavailability, the use of GOS for the improvement of iron bioavailability from FeFum in women with very low iron stores is promising. Funding Sources Innosuisse, Swiss Innovation Agency, in collaboration with Antistress AG - Burgerstein Vitamine.

Supermassive primordial black holes at high redshifts

We consider some properties and possible observational manifestations of the very heavy primordial black holes (PBHs), with masses [Formula: see text]. These black holes should be surrounded by the dense dark matter and baryonic halos even at early cosmological epochs. There are mechanisms as for radiation emission in the centers due to accretion and for deep absorption of relic radiation at the periphery of the halos. We calculate the absorption profile in the 21[Formula: see text]cm line of atomic hydrogen by solving the equations of radiation transfer through the baryonic halo around a PBH. The calculations show that a spherical absorbing layer appears around the object, which can be observed with radio telescopes. Also, at some epochs, shock waves may form at the periphery of the objects. The accelerated charged particles can radiate in radio frequency band, so it is possible that these objects can explain the recently discovered radio circles.

Self-Nanoemulsifying System Loaded with Sildenafil Citrate and Incorporated within Oral Lyophilized Flash Tablets: Preparation, Optimization, and In Vivo Evaluation

Sildenafil citrate is a drug used throughout the world primarily to treat erectile dysfunction. Several problems with the commercially available product decrease its efficacy, such as limited solubility, delayed onset of action, and low bioavailability with a large variability in the absorption profile. This study aimed to develop an optimized self-nanoemulsifying lyophilized tablet for the drug to conquer the foresaid problems. Sildenafil solubility in various surfactants, oils, and cosurfactants was attempted. An optimized formulation of a loaded self-nanoemulsion with a small droplet size was developed by applying a special cubic model of the mixture design. Sixteen formulations were prepared and characterized for droplet size. On the basis of solubility studies, a clove oil/oleic acid mixture, polysorbate 20 (Tween 20), and propylene glycol were selected as the proposed oil, surfactant, and cosurfactant, respectively. On the basis of desirability, an optimized sildenafil citrate-loaded self-nanoemulsifying delivery system containing 10% of the oil mixture, 60% of the surfactant, and 30% of the cosurfactant had a droplet size of 65 nm. Subsequently, the tablet form was fabricated with optimum ratios of 0.4% fumed silica, 0.1% hydroxypropyl methylcellulose, and 0.4% sodium starch glycolate. This formula showed satisfactory results in both disintegration and dissolution studies. In vivo pharmacokinetic studies indicated a higher bioavailability (1.44 times) and rapid absorption profile for the study’s tablets compared with commercially available tablets. In conclusion, highly bioavailable oral lyophilized flash tablets of sildenafil were successfully prepared. They will be a good alternative to the conventional solid-dosage form.

simba: the average properties of the circumgalactic medium of 2 ≤ z ≤ 3 quasars are determined primarily by stellar feedback

ABSTRACT We use the simba cosmological hydrodynamic simulation suite to explore the impact of feedback on the circumgalactic medium (CGM) and intergalactic medium (IGM) around 2 ≤ z ≤ 3 quasars. We identify quasars in simba as the most rapidly accreting black holes, and show that they are well matched in bolometric luminosity and correlation strength to real quasars. We extract Lyα absorption in spectra passing at different transverse distances ($10 \, \mathrm{kpc} \lesssim b \lesssim 10 \, \rm Mpc$) around those quasars, and compare to observations of the mean Lyα absorption profile. The observations are well reproduced, except within $100 \, \, \rm kpc$ from the foreground quasar, where simba overproduces absorption; this could potentially be mitigated by including ionization from the quasar itself. By comparing runs with different feedback modules activated, we find that (mechanical) AGN feedback has little impact on the surrounding CGM even around these most highly luminous black holes, while stellar feedback has a significant impact. By further investigating thermodynamic and kinematic properties of CGM gas, we find that stellar feedback, and not AGN feedback, is the primary physical driver in determining the average properties of the CGM around z ∼ 2–3 quasars. We also compare our results with previous works, and find that simba predicts much more absorption within $100 \, \rm kpc$ than the nyx and illustris simulations, showing that the Lyα absorption profile can be a powerful constraint on simulations. Instruments such as VLT-MUSE and upcoming surveys (e.g. WEAVE and DESI) promise to further improve such constraints.

Inference of chromospheric plasma parameters on the Sun

The solar chromosphere can be observed well through strong absorption lines. We infer the physical parameters of chromospheric plasmas from these lines using a multilayer spectral inversion. This is a new technique of spectral inversion. We assume that the atmosphere consists of a finite number of layers. In each layer the absorption profile is constant and the source function varies with optical depth with a constant gradient. Specifically, we consider a three-layer model of radiative transfer where the lowest layer is identified with the photosphere and the two upper layers are identified with the chromosphere. The absorption profile in the photosphere is described by a Voigt function, and the profile in the chromosphere by a Gaussian function. This three-layer model is fully specified by 13 parameters. Four parameters can be fixed to prescribed values, and one parameter can be determined from the analysis of a satellite photospheric line. The remaining 8 parameters are determined from a constrained least-squares fitting. We applied the multilayer spectral inversion to the spectral data of the Hα and the Ca II 854.21 nm lines taken in a quiet region by the Fast Imaging Solar Spectrograph (FISS) of the Goode Solar Telescope (GST). We find that our model successfully fits most of the observed profiles and produces regular maps of the model parameters. The combination of the inferred Doppler widths of the two lines yields reasonable estimates of temperature and nonthermal speed in the chromosphere. We conclude that our multilayer inversion is useful to infer chromospheric plasma parameters on the Sun.

GASP XXV: neutral hydrogen gas in the striking jellyfish galaxy JO204

ABSTRACT We present JVLA-C observations of the H i gas in JO204, one of the most striking jellyfish galaxies from the GASP survey. JO204 is a massive galaxy in the low-mass cluster A957 at z = 0.04243. The H i map reveals an extended 90 kpc long ram-pressure stripped tail of neutral gas, stretching beyond the 30 kpc long ionized gas tail and pointing away from the cluster centre. The H i mass seen in emission is $(1.32\pm 0.13) \times 10^{9} \, \rm M_{\odot }$, mostly located in the tail. The northern part of the galaxy disc has retained some H i gas, while the southern part has already been completely stripped and displaced into an extended unilateral tail. Comparing the distribution and kinematics of the neutral and ionized gas in the tail indicates a highly turbulent medium. Moreover, we observe associated H i absorption against the 11 mJy central radio continuum source with an estimated H i absorption column density of 3.2 × 1020 cm−2. The absorption profile is significantly asymmetric with a wing towards higher velocities. We modelled the H i absorption by assuming that the H i and ionized gas discs have the same kinematics in front of the central continuum source, and deduced a wider absorption profile than observed. The observed asymmetric absorption profile can therefore be explained by a clumpy, rotating H i gas disc seen partially in front of the central continuum source, or by ram pressure pushing the neutral gas towards the centre of the continuum source, triggering the AGN activity.