Bulk Absorption Research Articles

Moisture Sorption Isotherms of Polydextrose and Its Gelling Efficiency in Inhibiting the Retrogradation of Rice Starch.

As an anti-staling agent in bread, the desorption isotherm of polydextrose has not been studied due to a very long equilibrium time. The adsorption and desorption isotherms of five Chinese polydextrose products were measured in the range of 0.1-0.9 aw and 20-35 °C by a dynamic moisture sorption analyzer. The results show that the shape of adsorption and desorption isotherms was similar to that of amorphous lactose. In the range of 0.1-0.8 aw, the hysteresis between desorption and adsorption of polydextrose was significant. The sorption isotherms of polydextrose can be fitted by seven commonly used models, and our developed seven-parameter polynomial, the adsorption equations of generalized D'Arcy and Watt (GDW) and Ferro-Fontan, and desorption equations of polynomial and Peleg, performed well in the range of 0.1-0.9 aw. The hysteresis curves of polydextrose at four temperatures quickly decreased with aw increase at aw ˂ 0.5, andthereafter slowly decreased when aw ≥ 0.5. The polynomial fitting hysteresis curves of polydextrose were divided into three regions: ˂0.2, 0.2-0.7, and 0.71-0.9 aw. The addition of 0-10% polydextrose to rice starch decreased the surface adsorption and bulk absorption during the adsorption and desorption of rice starch, while it increased the water adsorption value at aw ≥ 0.7 due to polydextrose dissolution. DSC analysis showed that polydextrose as a gelling agent inhibited the retrogradation of rice starch, which could be used to maintain the quality of cooked rice.

Biocompatibility and osteogenic capacity of additively manufactured biodegradable porous WE43 scaffolds: An in vivo study in a canine model

Magnesium is the most promising absorbable metallic implant material for bone regeneration and alloy WE43 is already FDA approved for cardiovascular applications. This study investigates the cyto- and biocompatibility of novel additively manufactured (AM) porous WE43 scaffolds as well as their osteogenic potential and degradation characteristics in an orthotopic canine bone defect model. The cytocompatibility was demonstrated using modified ISO 10993-conform extract-based indirect and direct assays, respectively. Additionally, degradation rates of WE43 scaffolds were quantified in vitro prior to absorption tests in vivo. Complete blood cell counts, blood biomarker analyses, blood trace element analyses as well as multi-organ histopathology demonstrated excellent biocompatibility of porous y WE43 scaffolds for bone defect repair. Micro-CT analyses further showed a relatively higher absorption rate during the initial four weeks upon implantation (i.e., 36 % ± 19 %) than between four and 12 weeks (41 % ± 14 %), respectively. Of note, the porous WE43 implants were surrounded by newly formed bony tissue as early as four weeks after implantation when unmineralized trabecular ingrowth was detected. After 12 weeks, a substantial amount of mineralized bone was detected inside and around the gradually disappearing implants. This first study on AM porous WE43 implants in canine bone defects demonstrates the potential of this alloy for in vivo applications in humans. Our data further underscore the need to control initial bulk absorption kinetics through surface modifications.

Kinetic simulations of capacitively coupled plasmas driven by tailored voltage waveforms with multi-frequency matching

Impedance matching is crucial for optimizing plasma generation and reducing power reflection in capacitively coupled plasmas (CCP). Designing these matchings is challenging due to the varying and typically unknown impedance of the plasma, especially in the presence of multiple driving frequencies. Here, a computational design method for impedance matching networks (IMNs) for CCPs is proposed and applied to discharges driven by tailored voltage waveforms (TVW). This method is based on a self-consistent combination of particle in cell/Monte Carlo collision simulations of the plasma with Kirchhoff’s equations to describe the external electrical circuit. Two Foster second-form networks with the same structure are used to constitute an L-type matching network, and the matching capability is optimized by iteratively updating the values of variable capacitors inside the IMN. The results show that the plasma density and the power absorbed by the plasma continuously increase in the frame of this iterative process of adjusting the matching parameters until an excellent impedance matching capability is finally achieved. Impedance matching is found to affect the DC self-bias voltage, whose absolute value is maximized when the best matching is achieved. Additionally, a change in the quality of the impedance matching is found to cause an electron heating mode transition. Poor impedance matching results in a heating mode where electron power absorption in the plasma bulk by drift electric fields plays an important role, while good matching results in the classical α-mode operation, where electron power absorption by ambipolar electric fields at the sheath edges dominates. The method proposed in this work is expected to be of great significance in promoting TVW plasma sources from theory to industrial application, since it allows designing the required complex multi-frequency IMNs.

Physical and mechanical properties of meta-halloysite-based geopolymer mortars

Geopolymers are amorphous materials produced by the polymerisation reaction between an aluminosilicate precursor and an alkaline reagent or by activation with phosphoric acid. The aluminosilicate raw material used in the manufacture of geopolymers an be industrial waste, such as fly ash or volcanic ash, blastfurnace slag, or it can be obtained from natural raw materials, such as metakaolin and meta-halloysite. The work aimed to select the composition of an activator for the production of meta-halloysite geopolymers with optimum physico-mechanical properties such as specific and bulk density, porosity, weight, and bulk absorption, as well as flexural and compressive strength. A two-factor experimental design was employed to determine the composition of the alkaline activator for geopolymer mortars, with sodium hydroxide solution molar concentration and sodium silicate to NaOH ratio as variables. Research has shown that increasing the amount of sodium silicate relative to the mass of a 12M NaOH solution in the activator solution improves the compressive strength of geopolymers by 36.8%, while an increase in flexural strength of 14.2% was achieved. As the molar concentration of caustic soda in the activator solution increases from 19.0 to 24.5%, the porosity of geopolymer mortars decreases. The reduction in the ratio of water glass to sodium hydroxide and the reduction in the molar concentration of NaOH increases the mass and volume water absorption of the mortar. Further studies is necessary to determine the optimal mixture of metahalloysite geopolymer, taking into account its functional properties and durability.

New combined absorption/1H NMR method for qualitative and quantitative analysis of PET degradation products

Poly(ethylene terephthalate) (PET) is a very valuable and beneficial material for industrial purposes, with various different applications. Due to the high annual production volume of over 50 million tons worldwide and the indiscriminate disposal by consumers, the polymers accumulate in the environment, causing negative effects on various ecosystems. Biodegradation via suitable enzymes represents a promising approach to combat the plastic waste issue so validated methods are required to measure the efficiency and efficacy of these enzymes. PETase and MHETase from Ideonella sakaiensis are suitable enzymes needed in combination to completely degrade PET into its environmentally friendly monomers. In this project, we compare and combine a previously described bulk absorbance measurement method with a newly established 1H NMR analysis method of the PET degradation products mono(2-hydroxyethyl) terephthalic acid, bis(2-hydroxyethyl) terephthalic acid and terephthalic acid. Both were optimized regarding different solvents, pH values and drying processes. The accuracy of the measurements can be confirmed with sensitivity limits of 2.5–5 µM for the absorption method and 5–10 µM for the 1H NMR analysis. The combination of the described methods therefore allows a quantitative analysis by using bulk absorption coupled with a qualitative analysis through 1H NMR. The methods established in our work can potentially contribute to the development of suitable recycling strategies of PET using recombinant enzymes.

Physiological and interspecific factors determine diel changes in phytoplankton bio‐optical properties

AbstractBio‐optical properties of marine phytoplankton retrieved through satellite remote sensing are used to estimate ocean productivity and carbon cycling. Daily activity of phytoplankton is attuned to the predictable light fluctuations of the diel cycle. Field and laboratory studies have documented diel changes in phytoplankton growth, division, and respiration, carbon and pigment content, cell size, photosynthetic efficiency and rate, and DNA replication and transcription. Many of these physiological changes can alter cellular optical properties and contribute to diel variations in bulk absorption and scattering properties. Consequently, understanding phytoplankton contributions to diel optical cycles is essential for improving algorithms that convert remote sensing data to biological rates and stocks. Here, we describe time‐resolved cellular, photophysiological, and bio‐optical properties for three cultured phytoplankton ranging in cell size from ~ 1 to 6 μm: Ostreococcus lucimarinus, Synechococcus (WH8102), and Thalassiosira pseudonana, all of which can significantly contribute to phytoplankton abundance and/or biomass in the open and coastal ocean. This work is the first to characterize complete diel cycles in absorption and attenuation for O. lucimarinus and backscattering for all these species. Results show that the percent increase from the minimum to maximum values over the diel cycle ranged between ~ 24–121%, ~ 31–235%, and ~ 25–198% for particulate absorption, attenuation, and backscattering, respectively. Diel changes in bio‐optical properties also differed in both timing and magnitude across phytoplankton species, demonstrating the importance of contextualizing remote sensing observations with phytoplankton community composition.

Characterization of Khaya Senegalensis Gum: Effects of Drying Methods on the Physicochemical Properties

The study was aimed to assess the effect of drying methods on physicochemical properties of Khaya senegalensis gum. Gum exudates obtained from the bark of Khaya senegalensis plant was extracted and subjected to freeze drying and vacuum oven drying. Gel permeation chromatography, Elemental analysis, attenuated total reflectance Fourier transforms Infra red spectroscopy were used to characterize the gum. The effect of drying methods on the gum samples were assessed based on Differential scanning calorimetry, Scanning electron microscopy, Dynamic vapour sorption, particle size analysis via laser diffraction techniques, colour and density measurements. An average molecular weight of 60 KDa expressed as the Dextran equivalent and a polydispersity of 2.17 with a retention time of 18,485 min was recorded for the vacuum dried gum. The vacuum dried gum occurred as irregular discreet coarse particles, containing both amorphous and crystalline portions due to a glass transition of 65◦ and melting temperature of 182.35◦C. It also displayed excellent flow and compressibility properties whereas the freeze-dried gum appeared flaky, porous with large surface area. The mechanism of water sorption was found to be initial surface adsorption and subsequently bulk absorption for both freeze dried and vacuum dried gum samples. The coarseness, water sorption and retention ability of the vacuum dried gum provides a potential for its use as a disintegrant in solid dosage formulations whereas the freeze-dried gum will be suitable for use as a binding agent due to its smaller particle sizes that enhanced solubility. Furthermore, the presence of nitrogen in Khaya senegalensis gum structure explains its partial solubility and the azo aromatic group suggests biodegradability and candidature for drug delivery to the colon. Keywords: Khaya senegalensis Gum; Average Molecular Weight; Amorphous; Crystalline; Direct Compression Excipient; Disintegrant 2 Freeze and vacuum dried Khaya senegalensis gum characterization

Measurement report: Size-resolved mass concentration of equivalent black carbon-containing particles larger than 700 nm and their role in radiation

Abstract. Black carbon (BC) mass size distribution (BCMSD) is crucial in both the environment and the climate system due to BC's intense size-dependent absorption of solar radiation. BC-containing particles larger than 700 nm (BC>700) could contribute to more than half of bulk BC mass concentration. Unfortunately, previous methods concentrated on BC-containing particles of less than 700 nm because of technical limitations. The contribution of BC to absorption and the radiative effect might be underestimated without consideration of BC>700. In this study, equivalent BCMSD (eBCMSD) from 150 nm up to 1.5 µm was measured at high time resolution of 1 h for the first time by an aerodynamic aerosol classifier in tandem with an aethalometer in two field campaigns over eastern China, namely Changzhou located in the Yangtze River Delta and Beijing located in the North China Plain. The results revealed that the pattern of eBCMSD in Changzhou (Beijing) was mostly bimodal (unimodal) peaking at 240 and 1249 nm (427 nm). The peak diameter of eBCMSD in Changzhou did not shift significantly with increasing pollution (240 to 289 nm). In contrast, the peak diameter of eBCMSD in Beijing shifted towards larger sizes, from 347 to 527 nm, with increasing pollution, indicating that the aging process at the urban site was different from that at the regional background site. eBCMSD in both Changzhou and Beijing had a significant diurnal cycle with a smaller (larger) value of eBCMSD during daytime (nighttime). Equivalent BC>700 (eBC>700) was ubiquitous and varied significantly with different locations and pollution levels. The campaign-averaged contribution of eBC>700 to bulk eBC mass concentration (meBC,bulk), bulk absorption coefficient (σab,bulk) and estimated direct radiative forcing of eBC (DRFeBC) in Changzhou and Beijing were 27.8 % (20.9 %–36.5 %) and 24.1 % (17.5 %–34.2 %), 19.6 % (15.8 %–24.6 %) and 25.9 % (19.6 %–33.7 %) and 20.5 % (18.4 %–22.2 %) and 21.0 % (16.3 %–26.1 %), respectively. meBC,bulk, σab,bulk and DRFeBC of eBC>700 in Changzhou (Beijing) increased by a factor of 3.6 (5.1) from 0.11 (0.07) to 0.40 (0.36) µg m−3, by a factor of 3.2 (5.5) from 0.54 (0.63) to 1.75 (3.45) Mm−1 and by a factor of 2.4 (4.7) from 0.1 (0.1) to 0.24 (0.47) W m−2, respectively, with the aggravation of pollution. The contribution of eBC>700 to meBC,bulk and σab,bulk had a significant diurnal cycle with a higher (lower) fraction during daytime (nighttime) in both Changzhou and Beijing. A case study indicated that the contribution of eBC>700 to meBC,bulk, σab,bulk and DRFeBC could reach up to 50 %, 50 % and 40 %, respectively. It was highly recommended to consider the whole size range of BC-containing particles in model estimation of the BC radiative effect.

Temperature profiles of field-aged photovoltaic modules affected by optical degradation

Moisture ingress into PV module in the presence of ultraviolet radiation, high temperature, and other environmental stressors can affect the optical integrity of the PV module. Optical degradation can take the form of delamination, discolouration of encapsulant, metal grids corrosion, and trapped moisture or chemical species. This can influence the photon absorption and current transport properties in the PV module bulk, which can affect the module operating temperature. In the present work, the relationship between optical degradation and temperature sensitivity of 20-year-old multicrystalline silicon field-aged PV modules have been investigated. The selected PV modules were characterized using visual inspection, current-voltage (I–V) characterization, temperature coefficients profiling, current resistivity profiling, infrared (IR) thermal, ultraviolet fluorescence (UV–F), and electroluminescence (EL) imaging. PV modules affected by optical degradation show weak fluorescence and luminescence signal intensities. The average difference in cell temperature (ΔT) between the warmest and coldest cell for the PV modules investigated was found to be around 10 ± 2 °C and the average power degradation rate was approximately 0.8% per year. The underlying factor for the observed degradation is attributed to the degradation in the temperature coefficients of open circuit voltage (βVoc) and maximum power point voltage (βVmpp). The average temperature coefficient of efficiency (βηm) of the modules was found to be around −0.5%/°C. Finally, a temperature dependent resistivity method for extracting temperature coefficients from IR thermal data of PV modules has been proposed.

고령토 광물을 활용한 저 열팽창 코디어라이트 세라믹스 합성에 관한 연구

Cordierite (2MgO·2Al2O3·5SiO2) in the MgO·Al2O3·SiO2 system exhibits a low thermal expansion coefficient, high thermal shock resistance, low dielectric constant, and excellent electrical insulation properties. However, the material has a narrow sintering-temperature range. If the sintering temperature is too low, the crystal structure of cordierite does not form sufficiently; conversely, if it is slightly higher than ideal, the material decomposes into postelite, spinel, and mullite, leading to a significant increase in its thermal expansion coefficient. To overcome this problem, we adjusted the composition of cordierite by mixing it with predetermined amounts of kaolin minerals. After sintering at 1340℃, the resulting ceramic showed satisfactory physical properties, such as bulk density, absorption rate, and porosity. The optimal mixing conditions included a MgO/Al2O3 molar ratio of 1.006 and SiO2/Al2O3 molar ratio of 2.4277. Given its low thermal expansion coefficient(2.20 × 10−6/℃ at 800℃ and 2.57 × 10−6/℃ at 1000℃) and favorable physical and shrinkage properties, the cordierite prepared in this work may have potential applications in the development of kiln furniture materials for sintering next-generation secondary battery cathode materials.

Probing lithium mobility at a solid electrolyte surface

Solid-state electrolytes overcome many challenges of present-day lithium ion batteries, such as safety hazards and dendrite formation1,2. However, detailed understanding of the involved lithium dynamics is missing due to a lack of in operando measurements with chemical and interfacial specificity. Here we investigate a prototypical solid-state electrolyte using linear and nonlinear extreme-ultraviolet spectroscopies. Leveraging the surface sensitivity of extreme-ultraviolet-second-harmonic-generation spectroscopy, we obtained a direct spectral signature of surface lithium ions, showing a distinct blueshift relative to bulk absorption spectra. First-principles simulations attributed the shift to transitions from the lithium 1 s state to hybridized Li-s/Ti-d orbitals at the surface. Our calculations further suggest a reduction in lithium interfacial mobility due to suppressed low-frequency rattling modes, which is the fundamental origin of the large interfacial resistance in this material. Our findings pave the way for new optimization strategies to develop these electrochemical devices via interfacial engineering of lithium ions.

Optical properties of quasi-two-dimensional objects from time-dependent density functional theory: Longitudinal versus transverse dielectric functions

Comprehension of the electronic properties of nano-objects is a key to defining dedicated properties, which can be adjusted by changing their size. Beyond confinement effects, the presence of interfaces, i.e., places where there is an abrupt change of electronic density, should also play a role. Time-dependent density functional theory (TD-DFT) is a state-of-the-art ab initio formalism in which this effect is accounted for through the so-called local field effects. In an earlier paper [S. Mazzei and C. Giorgetti, Phys. Rev. B 106, 035431 (2022)], we showed that the framework inherited from three-dimensional crystals could not provide reliable absorption spectra. In the present paper, we propose to calculate the macroscopic average of the dielectric tensor of a quasi-two-dimensional (2D) object from the response function of the density to the total macroscopic potential in order to avoid use of the so-called Adler and Wiser formula. We evidence that the inclusion of interfaces in the thickness of the slab causes the response function for the out-of-plane component to move sharply from the bulk absorption resonance to the plasmon one. This shows that the longitudinal-longitudinal contraction of the dielectric tensor is no longer equal to the transverse-transverse one in a quasi-2D object for out-of-plane perturbation. Nevertheless, we also show that the macroscopic average of the dielectric tensor of an ultrathin slab calculated within the longitudinal formalism of TD-DFT depicts the properties of the transverse reflectance and transmittance spectra of a thin slab.

Electronic spectroscopy studies of Cu(100) following atomic hydrogen exposure

Using electron energy loss spectroscopy (EELS), we show that the surface plasmon loss intensity is highly sensitive to surface contamination. We exploit this property to develop a new variation of temperature programmed desorption (TPD),which we term virtual TPD (VTPD), that is uniquely sensitive to the sample surface. We apply this to a long standing puzzle in the behavior of atomic hydrogen adsorbed on Cu(100). We suggest that bulk absorption of hydrogen under ultra-high vacuum conditions is responsible for observed anomalies in this system. We show additional examples of VTPD to related systems.

Characterization of bulk optical properties of pear tissues in the 500 to 1000 nm range as input for simulation-based optimization of laser spectroscopy in diffuse transmittance mode

Insight in the transmission of light through intact fruit is important to optimize and interpret the signals acquired with spectroscopy methods such as tunable diode laser absorption spectroscopy (TDLAS). To this end, we quantified the bulk optical properties (BOP) of skin, outer cortex, inner cortex, and core tissue of three pear ( Pyrus communis ) cultivars ( Thimo , Cepuna , and Conference ) using double integrating spheres measurements in combination with the inverse adding doubling method. Similar trends and values were observed for the bulk optical properties of the three cultivars. A clear chlorophyll-a absorption feature was present in the bulk absorption coefficient ( μ a ) at 690 nm for the skin samples. At 761 nm, the bulk scattering coefficient ( μ s ) decreased from the skin towards the core region, for example from 256 ± 34 cm −1 to 146 ± 22 cm −1 for Conference pears. The observed anisotropy factor ( g ) of the skin was lower than these of the other tissue layers (0.87 ± 0.026 vs. 0.94 ± 0.08 for Conference ). Next, Monte Carlo voxelized media (MCVM) simulations were performed based on these BOP values and validated against measurements with a TDLAS setup for gas in scattering media absorption spectroscopy (GASMAS) at 761 nm. In these experiments, the sample thickness was reduced by sequentially slicing the pear from the skin towards the center. Light transmittance through an intact pear at the height of the core region was found to be very low (1.9 × 10 −4 ± 8.5 × 10 −5 %) and exponentially increased around 100-fold when the sample thickness decreased from 64 mm to 24 mm. The simulated transmittance profiles based on the measured BOP values at 761 nm followed the same trend as the measured GASMAS transmittance as a function of the fruit thickness. This shows that simulations based on these measured BOP values can be used to optimize the measurement configuration for O 2 monitoring in intact pear fruit with GASMAS. • The bulk optical properties of pear tissue layers: skin, outer cortex, inner cortex, and core. • 3D Monte Carlo simulation of diffuse transmittance through an intact pear. • Comparison of simulated and measured diffuse transmittance vs pear sample thicknesses. • Simulations provided a valuable tool for optimizing the amplification of GASMAS detectors in diffuse transmittance mode.

Optical bulk-boundary dichotomy in a quantum spin Hall insulator

The bulk-boundary correspondence is a critical concept in topological quantum materials. For instance, a quantum spin Hall insulator features a bulk insulating gap with gapless helical boundary states protected by the underlying Z2 topology. However, the bulk-boundary dichotomy and distinction are rarely explored in optical experiments, which can provide unique information about topological charge carriers beyond transport and electronic spectroscopy techniques. Here, we utilize mid-infrared absorption micro-spectroscopy and pump–probe micro-spectroscopy to elucidate the bulk-boundary optical responses of Bi4Br4, a recently discovered room-temperature quantum spin Hall insulator. Benefiting from the low energy of infrared photons and the high spatial resolution, we unambiguously resolve a strong absorption from the boundary states while the bulk absorption is suppressed by its insulating gap. Moreover, the boundary absorption exhibits strong polarization anisotropy, consistent with the one-dimensional nature of the topological boundary states. Our infrared pump–probe microscopy further measures a substantially increased carrier lifetime for the boundary states, which reaches one nanosecond scale. The nanosecond lifetime is about one to two orders longer than that of most topological materials and can be attributed to the linear dispersion nature of the helical boundary states. Our findings demonstrate the optical bulk-boundary dichotomy in a topological material and provide a proof-of-principal methodology for studying topological optoelectronics.

Tuning ferroelectric photovoltaic performance in R3c-CuNbO3 through compressive strain engineering: a first-principles study.

Most ferroelectric oxides exhibit relatively wide bandgaps, which pose limitations on their suitability for photovoltaics application. CuNbO3 possesses potential ferroelectric properties with an R3c polar structure that facilitate the separation of charge carriers under illumination, promoting the generation of photovoltaic effects. The optical and ferroelectric properties of R3c-CuNbO3, as well as the effect of strain on the properties are investigated by first-principles calculation in this paper. The calculated results indicate that R3c-CuNbO3 possesses a moderate band gap to absorb visible light. The interaction of Cu-O and Nb-O bonds is considered to have a crucial role in the photovoltaic properties of CuNbO3, contributing to the efficient absorption of visible light. The bandgap of CuNbO3 becomes smaller and the density of states near the conduction and valence bands becomes relatively uniform in distribution under compressive conditions, which improves the photoelectric conversion efficiency to 29.9% under conditions of bulk absorption saturation. The ferroelectric properties of CuNbO3 are driven by the Nb-O bond interactions, which are not significantly weakened by the compressive strain. CuNbO3 is expected to be an excellent ferroelectric photovoltaic material by modulation of compressive strain due to the stronger visible light absorption and excellent ferroelectric behavior.

Internal quality assessment of kiwifruit by bulk optical properties and online transmission spectra

The purpose of this study was to compare the accuracy and robustness of the detection models based on bulk optical properties (BOP) with that based on conventional spectroscopy in kiwifruit quality evaluation. 81 kiwifruit were selected as experimental samples in this study. A single integrating sphere system was built to estimate the bulk absorption coefficient (μa) and bulk reduced scattering coefficient (μs′) of samples and a self-designed online system was used to obtain transmission spectra. The relationship of μa and μs′ with SSC and flesh firmness was analyzed, and detection models were established using partial least squares regression (PLSR). Competitive adaptive reweighted sampling (CARS) was also used to eliminate the variables in the original spectra that do not contribute to the improvement of the model performance. Results showed that μa at 670 nm decreased with the increase of SSC, μa at 720–900 nm and 950–1000 nm increased with the increase of SSC, and spectra of μs′ decreased with the decreasing firmness. CARS-PLSR models were developed, based on μa, μs′, μa×μs′, μeff, μt′, and transmission spectra. The accuracy of the model based on BOP in predicting internal quality was better than that based on transmission spectra. The model based on μa was the best for SSC (Rp2 = 0.97, RMSEP = 0.25%), and the model based on μa×μs′ was the best for flesh firmness (Rp2 = 0.97, RMSEP = 0.02 N). 20 kiwifruit that differed from the experimental samples in planting orchard and harvest time were used to compare the robustness and portability of the models. Results showed that all SSC models and the firmness model based on μa×μs′ had good robustness and portability. However, the model based on transmission spectra had a poor performance in predicting the firmness of samples from the external validation set. This study provides an effective reference for the prediction of firmness and SSC based on BOP and transmission spectra of kiwifruit.

Morphogen gradient formation in partially absorbing media

Morphogen gradients play an essential role in the spatial regulation of cell patterning during early development. The classical mechanism of morphogen gradient formation involves the diffusion of morphogens away from a localized source combined with some form of bulk absorption. Morphogen gradient formation plays a crucial role during early development, whereby a spatially varying concentration of morphogen protein drives a corresponding spatial variation in gene expression during embryogenesis. In most models, the absorption rate is taken to be a constant multiple of the local concentration. In this paper, we explore a more general class of diffusion-based model in which absorption is formulated probabilistically in terms of a stopping time condition. Absorption of each particle occurs when its time spent within the bulk domain (occupation time) exceeds a randomly distributed threshold a; the classical model with a constant rate of absorption is recovered by taking the threshold distribution . We explore how the choice of Ψ(a) affects the steady-state concentration gradient, and the relaxation to steady-state as determined by the accumulation time. In particular, we show that the more general model can generate similar concentration profiles to the classical case, while significantly reducing the accumulation time.

Optical properties of low background PEN structural components for the Legend-200 experiment

Polyethylene Naphthalate (PEN) plastic scintillator has been identified as potential self-vetoing structural material in low-background physics experiments. Radio-pure scintillating components have been produced from PEN using injection compression molding technology. These low-background PEN components will be used as optically active holders to mount the Germanium detectors in the Legend-200 neutrinoless double beta decay experiment. In this paper, we present the measurement of the optical properties of these PEN components. The scintillation light emission spectrum, time constant, attenuation and bulk absorption length as well as light output and light yield are reported. In addition, the surface of these PEN components has been characterized and an estimation of the surface roughness is presented. The light output of the final Legend-200 detector holders has been measured and is reported. These measurements were used to estimate the self-vetoing efficiency of these holders.

The effect of structural disorder on the hydrogen loading into the graphene/nickel interface

Hybrid materials composed by porous Ni foams coated by graphene appear appealing architectures to be applied in the field of hydrogen storage, where, due to the high surface-to-volume ratio of both components, are expected to be much more performant than their flat counterparts. In order to explore this possibility, in this study we have grown single layer graphene on nickel foams by chemical vapour deposition in ultra-high vacuum and have investigated the interaction with H atoms as a function of the temperature. By using high resolution C1s core level spectroscopy we found that nearly half of the graphene layer interacts with the support almost as strongly as with the flat ordered Ni substrate, whereas the other half is nearly free standing. Such dual electronic and structural coupling drives the hydrogenation of the graphene/foam interface. By using thermal programmed desorption combined with x-ray photoelectron spectroscopy we found that in the weakly interacting graphene regions, even at very low temperatures, H atoms easily intercalate below graphene, and enter in the bulk of the foam, from where they start to desorb around 180 K. This behaviour mimics what happens when dosing H atoms on the bare Ni foam. On the contrary, H intercalation below the strongly interacting graphene regions occurs only for temperatures around and above 200 K. The thermal desorption curves demonstrated that the presence of the graphene layer does not reduce the effectiveness of H loading in the bulk of the foam. On the other hand, it does not even increase significantly the stored amount with respect to the uncoated support, but contributes to stabilizing the stored hydrogen. Although the fundamental aspects of graphene/foam hydrogenation were here investigated in a regime far below the saturation of the bulk absorption, these measurements can be the starting point for further investigations aimed at establishing the ultimate storage capability of these hybrid nanostructured tanks.