Equal Density Research Articles

Analyzing Carrier Density and Hall Mobility in Impurity‐Free Silicon Virtually Doped by External Defect Placement

AbstractImpurity doping at the nanoscale for silicon is becoming less efficient with conventional techniques. Here, an alternative virtual doping method is presented for silicon that can achieve an equivalent carrier density while addressing the primary limitations of traditional doping methods. The doping for silicon is carried out by placing aluminum‐induced acceptor states externally in a silicon dioxide dielectric shell. This technique can be referred to as direct modulation doping. The resistivity, carrier density, and mobility are investigated by Hall effect measurements to characterize the carrier transport using the new doping method. The results thereof are compared with carrier transport analysis of conventionally doped silicon at room‐temperature, demonstrating a 100% increase in carrier mobility at equal carrier density. The sheet density of hole carriers in silicon due to modulation doping remains nearly constant, ≈4.7 × 1012 cm−2 over a wide temperature range from 300 down to 2 K, proving that modulation‐doped devices do not undergo carrier freeze‐out at cryogenic temperatures. In addition, a mobility enhancement is demonstrated with an increase from 89 cm2 Vs−1 at 300 K to 227 cm2 Vs−1 at 10 K, highlighting the benefits of the new method for creating emerging nanoscale electronic devices or peripheral cryo‐electronics to quantum computing.

Efficiency of coronavirus testing from a spatial perspective: the Israeli case

ABSTRACT A prominent characteristic of. COVID-19 is the long incubation period, the lack of symptoms during that period, and significant geographic variation in prevalence and testing. This article investigates the relationship between testing and infection based on an Israeli sample of 193 municipalities and a report from 11 May 2020. Results support an exponential rise in the fraction of positive. COVID-19 outcomes with the fraction of tests. Finally, under conditions of equal socioeconomic ranking, population density and income inequality, the projected efficiency of tests rises with population density and the Gini index and drops with socioeconomic ranking.

Size Effects of Gold Nanoparticles on Surface Plasmon Resonance Assays for DNA Hybridization.

Recent advancements in signal amplifiers, such as biofunctionalized gold nanoparticles (AuNPs) have improved the surface plasmon resonance (SPR) performance. However, the correlation between the sizes of DNA-Au conjugates and the SPR chips remains elusive. We investigated how the size of AuNPs functioned with DNA detection probes (D-AuNPs) affect SPR signals in sandwich DNA hybridization assays. The effects of three sizes (5, 13, and 29 nm) of D-AuNPs with an equal surface probe density were systematically compared to delineate the relationship between signal amplification and steric hindrance. Sporadically adsorbed target DNA on sparse capture probe-coated chips led to a growth of signal amplification with larger D-AuNPs. In contrast, on dense capture probe-coated SPR chips, when the target DNA concentration was above 1.5 nM, the medium-sized 13-nm AuNPs displayed 1.7- and 1.3-fold enhancement factors than 5-nm and 29-nm ones, respectively. Our results indicate the steric hindrance disturbs the capture of D-AuNPs on dense target DNA-modified chips, rendering the surface density of captured D-AuNPs a determining factor of the sensor response. Alternatively, the sensor sensitivity to D-AuNP surface density is crucial on chips with sparse target DNA. These insights should stimulate and guide future research on surface functionalization toward SPR sensors and AuNPs.

De-etiolation is Almost Colour Blind: the Study of Photosynthesis Awakening Under Blue and Red Light.

The synthesis and assembly of functioning photosynthetic complexes in chloroplasts developing from etioplasts during the de-etiolation of angiosperm seedlings are imperative for the plant's autotrophic lifestyle. This study compared de-etiolation process under monochromatic red or blue light of equal photon flux density during a 24-hour illumination period of etiolated Arabidopsis seedlings. The aim was to elucidate the impact of these light wavelength on the etioplast-to-chloroplast transformation and the initiation of light-dependent photosynthetic reactions. Both treatments lead to the formation of functional young chloroplasts; however, the etioplast-to-chloroplast transition and the assembly of photosynthetic complexes occurred unevenly, with individual steps tuned by red or blue light. Ultrastructural analysis suggested faster prolamellar bodies disassembly under blue light, while low temperature fluorescence studies indicated a slower transformation of protochlorophyllide to chlorophyllide, and chlorophyll a, under these conditions. Red light further promoted the synthesis of chlorophyll b and LHCII antenna proteins. However, the efficiency of antennae in dissipating excess absorbed energy was higher for seedlings de-etiolated under blue light; the maximum quantum yield of the photosystem II reached 0.81 after 24-hour de-etiolation, equivalent to mature plants. Blue light seemed to enhance the development of well-functioning photosystems (I and II) and antennae. These findings are important for gaining a deeper understanding of photoreceptor regulation of de-etiolation and for utilizing selected light regimes to improve crop yield.

Enabling Low Iridium Loadings and Reduced Catalyst Material Cost for PEM Water Electrolyzers Via Composite Anode Design with Conductive Additive

Herein, we present the successful implementation of a composite anode using a conductive additive to enable low iridium (Ir) loadings for PEMWE while maintaining high-performance operation. We use platinum (Pt) black as the conductive additive given its high electrical conductivity, high stability, and a price currently one-fifth that of Ir. Using a high loading of Pt black conductive additive allowed for retained electrode thickness, good dispersion of Ir particles, and drastically decreased sheet resistance at low Ir loadings of 0.10 mgIr cm-2. Compared to a standard Ir oxide anode with high, commercially relevant Ir loading, a composite anode with a low loading of 0.10 mgIr cm-2 achieved an equal current density performance at 1.8 V, translating to a 95% reduction in loading and 80% cost reduction of the anode catalyst materials.

Enabling Low Iridium Loadings and Reduced Catalyst Material Cost for PEM Water Electrolyzers Via Composite Anode Design with Conductive Additive

Herein, we present the successful implementation of a composite anode using a conductive additive to enable low iridium (Ir) loadings for PEMWE while maintaining high-performance operation. We use platinum (Pt) black as the conductive additive given its high electrical conductivity, high stability, and a price currently one-fifth that of Ir. Using a high loading of Pt black conductive additive allowed for retained electrode thickness, good dispersion of Ir particles, and drastically decreased sheet resistance at low Ir loadings of 0.10 mgIr cm-2. Compared to a standard Ir oxide anode with high, commercially relevant Ir loading, a composite anode with a low loading of 0.10 mgIr cm-2 achieved an equal current density performance at 1.8 V, translating to a 95% reduction in loading and 80% cost reduction of the anode catalyst materials.

Acellular Dermal Matrix: Imaging Features With Histopathology Correlation.

Acellular dermal matrix (ADM) is an immunologically inert graft, typically from cadaveric skin, often used in postmastectomy breast reconstruction. Created from decellularized dermal tissues that have been treated to remove DNA and antigenic donor cells (leaving extracellular matrix), ADM is often used as a structural scaffold or sling to reinforce and support the structure and position of a breast implant during postoperative integration in implant-based breast reconstruction; ADM can also be used to fill cosmetic defects. Advantages of ADM use include improved cosmesis and reduced capsular contracture rates. On US, ADM can be seen as a subtle band with variable echogenicity adjacent to the implant. When folded on itself or redundant, ADM may present as a palpable oval mass with indistinct or circumscribed margins and variable echogenicity. On mammography, ADM can be seen as a circumscribed oval equal density mass when redundant and folded on itself; a layered appearance may be evident on tomosynthesis. On MRI, presence and absence of enhancement have been documented. Imaging findings likely vary depending on the degree of host tissue remodeling and incorporation, and when biopsied, histopathologically, ADM may be difficult to distinguish from scarring. Successful imaging diagnosis of ADM is aided by clinical knowledge of the intraoperative use and configuration of ADM, which may help differentiate ADM from new or recurrent malignancy and avoid unnecessary biopsy.

Composite Anode for PEM Water Electrolyzers: Lowering Iridium Loadings and Reducing Material Costs with a Conductive Additive.

To enable the greater installed capacity of proton exchange membrane water electrolysis (PEMWE) for clean hydrogen production, associated costs must be lowered while achieving high current density performance and durability. Scarce and expensive iridium (Ir) required for the oxygen evolution reaction (OER) is a large contributor to the overall cost, yet high loadings of Ir (1-2 mgIr cm-2) are currently needed in commercial systems to maintain sufficient activity, conductivity, and durability. To meet the aggressive targets for low Ir loadings, we introduce a composite anode approach using a conductive additive that is less expensive than Ir to facilitate robust, high-performance operation with low Ir loading by retaining electrode thickness and in-plane electrical conductivity. In this demonstration, we use platinum (Pt) black as the conductive additive given its high electrical conductivity, acid stability, and current price one-fifth that of Ir. Using a high-activity commercial Ir oxide (IrO x ) catalyst, we present a 95% Ir loading reduction and 80% cost reduction of the anode catalyst materials while maintaining equal current density performance at a cell voltage of 1.8 V. Furthermore, we show enhanced stability of a composite anode compared to an IrO x anode with loadings of 0.10 mgIr cm-2 via accelerated stress test (AST) and postmortem imaging. With this approach, we show promising results toward lowering Ir loadings and material costs, addressing a significant barrier to the widespread adoption of PEMWE for clean hydrogen production.

Optimization design and interface characteristics research of high damping NiTi - Nickel-Aluminum Bronze functional gradient composite coating additively manufactured by high-speed laser-directed energy deposition

The near-equatomic NiTi shape memory alloy demonstrates exceptional damping performance due to its distinctive low-temperature self-cooperative martensitic internal friction. This study successfully fabricated NiTi-NAB (Nickel-Aluminium bronze shape memory alloy) functionally graded composite coatings with excellent metallurgical bonding between layers on Q235 steel substrates by designing an appropriate interlayer structure and employing the high-speed laser-directed energy deposition (LDED). Through comprehensive evaluation of the composite coating's performance and the numerical simulations of heat transfer within the molten pool, we elucidated the impact of process parameter levels on the microstructure and phase transformation characteristics of the NiTi alloy coating (NTC). The phase composition and phase interface characteristics of the NTC surface and bonding interface were analyzed using an electron probe microanalyzer and transmission electron microscopy, while dynamic thermomechanical analysis was employed to evaluate the damping performance of the NTC. The results indicate that an optimal parameter combination area still exists within the NTC-LDED process parameter window, even with equal laser energy density. Insufficient parameter levels can lead to an increase of micro-defects within the NTC, consequently causing a deterioration in both the cohesion and deformation resistance of the coating. Excessively high parameter levels can lead to significant element loss and residual stress, which in turn contributes to an increase in microcracks within the coating. A considerable quantity of reaction product mixture phases was formed at the interface between NTC and NAB, tending to align coherently with the NAB phase interface. The NTC, prepared with optimal process parameters, exhibits exceptional damping performance with a damping ratio of 0.498 at internal friction equilibrium, rendering it highly promising for applications in surface erosion protection for fluid machinery.

Scaling of turbulence-forced capillary waves

We simulate the propagation of capillary waves at the interface between two liquid layers of equal density, viscosity and thickness, which flow in stratified conditions inside a turbulent Poiseuille channel. This setup gives us the possibility to single out the effect of inertia and surface tension – in isolation from gravity – on the propagation of interfacial capillary waves. Numerical simulations, which are based on a combined pseudo spectral/phase field method, are run keeping the shear Reynolds number constant, Reτ=300, and considering four different values of the Weber number: We=0.5, We=1.0, We=1.5 and We=2.0. In the present case, waves are naturally forced by turbulence over a broad range of scales, from the larger ones, whose size is of order of the channel height h, down to the smaller dissipative scales. We show that, by increasing the Weber number, the interface is deformed more vigorously, and is prone to sustain the propagation of waves over a broader range of scales. Upon computation of the power spectra of wave elevation, we show that the behavior of waves agrees with the theoretical predictions given by the weak wave turbulence theory, which predicts a decay Sη(k)∼k−4 in the inertial regime, followed by a steeper decay at large k, in the surface-tension-dominated regime. We clearly show that the transition between the inertial and the surface-tension-dominated regime is pushed towards larger k by increasing the Weber number. In addition, we show that the two-dimensional frequency–wavenumber spectra of the wave elevation – the dispersion relation – is in good agreement with well established theoretical prediction, ω(k)∼k3/2, and that the range of validity of such prediction broadens for increasing Weber number.

Near-infrared spectroscopy identification method of cashmere and wool fibers based on an optimized wavelength selection algorithm

Cashmere and wool fibers have similar chemical compositions, making them difficult to distinguish based on their absorption peaks and band positions in near-infrared spectroscopy. Existing studies commonly use wavelength selection or feature extraction algorithms to obtain significant spectral features, but traditional algorithms often overlook the correlations between wavelengths, resulting in weak adaptability and local optimum issues. To address this problem, this paper proposes a recognition algorithm based on optimal wavelength selection, which can remove redundant information and make the model effective in capturing patterns and key features of the data. The wavelengths are rearranged by computing the information gain ratio for each wavelength. Then, the sorted wavelengths are grouped based on equal density, which ensures that all wavelengths within each group have equal information and avoids over-focusing on individual groups. Meanwhile, the group genetic algorithm is used to find the wavelengths with highly informative and search optimal grouped combinations, in order to explore the entire spectrum wavelength. Finally, combined with a partial least squares discriminant analysis(PLS-DA) model, the recognition accuracy reached 97.3 %. The results indicate that, compared to traditional methods such as CARS, SPA, and GA, our method effectively reduces redundant information, selects fewer but more informative wavelengths, and improves classification accuracy and model adaptability.

Study on the properties of deuterium ions in a composite cathode vacuum arc discharge

A vacuum arc discharge with a metal-deuteride cathode can generate a supersonic deuterium ion jet, which finds important applications in vacuum arc ion sources. In this study, a 1D3V spherical particle-in-cell direct simulation Monte Carlo cathode spot model with a titanium-deuteride cathode is developed to investigate the ionization and acceleration of deuterium ions from vacuum breakdown to the steady-arc stage. The effects of cathode deuteration concentration on the deuterium ion fraction and kinetic energy are also analyzed. The results show that the released deuterium atoms start to be ionized at around tens of nanometers from the cathode and then become fully ionized at about 0.4μm as the cathode potential drop gradually builds up. The proportion of deuterium ions in the plasma is slightly higher than the proportion of deuterium atoms in the cathode material. Velocity separation of deuterium and titanium ions occurs due to the acceleration of the electric field during the vacuum breakdown stage; however, the predominant ion–ion Coulomb collisions wipe out this separation in the steady-arc stage. Shifting the deuterium atom concentration in the cathode under a constant arc burning voltage produces an approximately equal current density, and increases the velocities of all ion species. A higher ion kinetic energy is gained by reducing the ohmic heating dissipation, facilitated by the lower plasma resistivity under the increased deuterium ion density.

Thermal perception of infrared radiation applied at different wavelengths to distal body segments in neutral and cool ambient environments

Personal Comfort Systems (PCS) hold the promise of simultaneously improving energy conservation and occupants’ thermal comfort. Locally applied thermal radiation is one of the most common PCS strategies for cool ambient environments. This study examines the subjective impacts of different infrared wavelengths applied to distal body segments of human subjects sitting quietly in cool and neutral environments. Experiment participants were exposed to three different wavelengths (near-infrared, mid-to far-infrared, and far-infrared), each of approximately equal flux density, on the backs of hands, lower arms, and lower legs, in both neutral (26.0 °C operative temperature) and cool (21.5 °C operative temperature) ambient environments within the chamber. Skin temperature, along with subjective thermal sensation and thermal pleasure votes were recorded throughout each exposure experiment. In the cool environment, similar to the neutral environment, far-infrared radiation increased skin temperature more than near-infrared and elicited warmer subjective thermal sensations and thermal pleasure responses. Of the three distal body segments examined, the back of the hands was most sensitive to the different wavelengths and was associated with the strongest and fastest pleasure response at the onset of radiant heating during the cool ambient environmental exposures. These findings have implications for PCS design, suggesting that irradiating the back of the hand with far-infrared wavelengths at the onset of PCS use may maximize thermal comfort of sedentary occupants in cool ambient conditions for a given power input.

Mechanical Characteristics of Sandwich Structures with 3D-Printed Bio-Inspired Gyroid Structure Core and Carbon Fiber-Reinforced Polymer Laminate Face-Sheet.

The gyroid structure is a bio-inspired structure that was discovered in butterfly wings. The geometric design of the gyroid structure in butterfly wings offers a unique combination of strength and flexibility. This study investigated sandwich panels consisting of a 3D-printed gyroid structure core and carbon fiber-reinforced polymer (CFRP) facing skin. A filament fused fabrication 3D printer machine was used to print the gyroid cores with three different relative densities, namely 10%, 15%, and 20%. Polylactic acid (PLA) was used as the printing material for the gyroid. The gyroid structure was then sandwiched and joined by an epoxy resin between CFRP laminates. Polyurethane foam (PUF) was filled into the gyroid core to fill the cavity on the core for another set of samples. Flexural and compression tests were performed on the samples to investigate the mechanical behavior of the sandwiches. Moreover, the two-parameter Weibull distribution was used to evaluate the results statistically. As a result, the sandwich-specific facing stress and core shear strength from the three-point bending test of the composites increased with the increase in sandwich density. Core density controls the flexural characteristics of the sandwich. Adding PUF improves the deflection at the maximum stress and the sustained load after fracture of the sandwich. Compression strength, modulus, and energy absorbed by gyroid core sandwiches and their specific properties are higher than the PUF-filled gyroid core sandwiches at equal sandwich density.

Breast Hemangiomas: Imaging Features With Histopathology Correlation.

Breast hemangiomas are rare benign vascular lesions. In a previously performed review of approximately 10,000 breast surgical pathology results, roughly 0.15% (15/~10 000) were hemangiomas. Hemangiomas are more frequent in women and have a documented age distribution of 1.5 to 82 years. They are most often subcutaneous or subdermal and anterior to the anterior mammary fascia but may rarely be seen in the pectoralis muscles or chest wall. On imaging, breast hemangiomas typically present as oval or round masses, often measuring less than 2.5 cm, with circumscribed or mostly circumscribed, focally microlobulated margins, equal or high density on mammography, and variable echogenicity on US. Calcifications, including phleboliths, can be seen. Color Doppler US often shows hypovascularity or avascularity. MRI appearance can vary, although hemangiomas are generally T2 hyperintense and T1 hypointense with variable enhancement. Pathologic findings vary by subtype, which include perilobular, capillary, cavernous, and venous hemangiomas. If core biopsy pathology results are benign, without atypia, and concordant with imaging and clinical findings, surgical excision is not routinely indicated. Because of histopathologic overlap with well-differentiated or low-grade angiosarcomas, surgical excision may be necessary for definitive diagnosis. Findings that are more common with angiosarcomas include size greater than 2 cm, hypervascularity on Doppler US, irregular shape, and invasive growth pattern.

Abstract 2916: Discoidin domain receptor 1 (DDR1) expression is associated with degree of immune exclusion across epithelial tumors

Abstract Background: Discoidin domain receptor 1 (DDR1) is highly expressed in epithelial cancers and has been implicated in tumor growth, invasion, and lack of response to therapy. DDR1 contributes to immune exclusion by promoting tumor collagen alignment in in vivo models. However, it is unclear how DDR1 expression impacts immune cell infiltration in human tumors. A first-in-human trial of PRTH-101, a DDR1-targeted therapeutic antibody, is underway. Establishing a correlation between DDR1 expression and immune infiltration in the tumor microenvironment (TME) will shed light on the role of DDR1 in the TME and inform indication and patient selection strategies for DDR1-targeted therapies. Methods: Adjacent formalin fixed paraffin embedded slides from colorectal (CRC), non-small cell lung (NSCLC), ovarian (OC), pancreatic (PDAC), and triple-negative breast cancers (TNBC) were stained by H&E and a multiplex immunofluorescence (mIF) panel containing DDR1 and immune cell markers CD8 and CD45. Tumor-stromal segmentation and cell identification was done from H&E using AI-powered models developed by PathAI (PathExplore™) or from mIF by image analysis using QuPath. DDR1 mRNA expression was measured by bulk RNA-sequencing, while DDR1 protein expression was measured by mIF. Immune Exclusion Scores (IESs) were calculated for each tumor based on lymphocyte density (from H&E), CD8+ T cell density (from mIF), or CD45+ cell density (from mIF). Each IES is the orthogonal distance between the coordinate of immune cell density in tumor epithelium and stroma, and the regression line representing equal density in epithelium and stroma. Correlations between lymphocyte, CD8, and CD45 IESs and DDR1 mRNA or protein expression levels were evaluated. Results: Both DDR1 mRNA and protein expression levels were significantly correlated with all Immune Exclusion Scores (IESs) measured by the distribution of lymphocytes (H&E), CD8+, or CD45+ cells (mIF) in tumor epithelium and stroma (R: 0.31-0.55, adjusted p: <0.001-0.01) at a pan-cancer level. While the degree of the correlation varied between tumor indications by IES immune cell type, pancreatic cancer exhibited the strongest correlation between the lymphocyte-based IES and DDR1 mRNA and protein expression (R: 0.48-0.54, adjusted p: 0.04-0.07). DDR1 mRNA was also moderately correlated with lymphocyte IES in NSCLC and TNBC (R: 0.37-0.48, adjusted p: 0.12-0.14). Conclusions: We developed a continuous scoring method to quantify the degree of immune exclusion in tumors based on the spatial distributions of lymphocytes, CD8+ T cells, and CD45+ immune cells from H&E and mIF images. DDR1 mRNA and protein expression are correlated with immune exclusion at both the pan-cancer and specific indication level. This adds additional insight into the role of DDR1 in human cancers and may be useful in selecting indications and stratifying patients for DDR1-targeted therapies. Citation Format: Xinwei Sher, Fredrick D. Gootkind, Thomas Schürpf, Florent Peyraud, Jean-Philippe Guégan, Antoine Italiano, G. Travis Clifton, Laura A. Dillon. Discoidin domain receptor 1 (DDR1) expression is associated with degree of immune exclusion across epithelial tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 2916.

Parity and Partition of the Rational Numbers

Summary We define an extension of parity from the integers to the rational numbers. Three parity classes are found—even, odd, and “none”. Using the 2-adic valuation, we partition the rationals into subgroups with a rich algebraic structure. The natural density provides a means of distinguishing the sizes of countably infinite sets. The Calkin-Wilf tree has a remarkably simple parity pattern, with the sequence “odd/none/even” repeating indefinitely. This pattern means that the three parity classes have equal natural density in the rationals. A similar result holds for the Stern-Brocot tree.

Thermal Conductivity of Liquid trans-1,2-Dichloroethene (R-1130(E)): Measurement and Modeling

The thermal conductivity of liquid trans-1,2-dichloroethene (R-1130(E)) was measured at temperatures ranging from 240 K to 340 K and pressures up to 25 MPa using a transient hot-wire instrument. A total of 447 thermal conductivity data points were measured along six isotherms. Each isotherm includes data at nine pressures, which were chosen to be at equal density increments starting at a pressure of 0.1 MPa (or slightly above the saturation pressure of R-1130(E) at temperatures above its normal boiling point) to a maximum pressure of 25 MPa. The combined expanded uncertainty of the presented experimental data is 1.4% at a 95% confidence level. The experimental data were used to evaluate the performance of an extended corresponding states (ECS) model and a residual entropy scaling (RES) model. Both models were applied in a totally predictive mode, and in a mode where the experimental data were used to tune the model parameters. A volume-translated Peng–Robinson equation of state was used to provide thermodynamic properties needed to apply both models. In a totally predictive mode, the ECS model had an average absolute relative deviation (ΔAARD) of 6.89% relative to the experimental data with the largest deviation being − 8.33%. The RES model in a totally predictive mode showed an ΔAARD of 2.55% with the largest deviation being − 5.81%. When model parameters were fitted to the experimental data, both the ECS and the RES model represented the experimental data to within its uncertainty of 1.4%.

Advancing lithium neutron capture therapy: 6Li-loaded nanoparticles and laser-driven neutron sources

We report on 6Li neutron capture therapy (LiNCT) in anticipation of using carbon nanoparticles to deliver targeted, high linear energy transfer radiation to non-resectable tumors. Our investigations show that, compared with existing 10B neutron capture therapy (BNCT), 6Li offers similar dose potential for equal mass density (DLi∼DB when mLi=mB), for capture products that span 7 times more range and approximately three cell lengths. Consequently, 6Li-filled nanoparticles dispersed more than half-a-cell-length apart, better convey high doses and ultra-high dose-rates, as LiNCT generates substantially less γ-rays and becomes more targeted than BNCT. To this end, we propose a neutron production scheme involving laser-plasma driven protons incident on various 7Li targets, capable of producing >109 n/sr/pulse. For high repetition frequency, efficient neutron moderation, and ideal 6Li concentration, the modality offers greater precision than existing neutron capture therapy.

A Low Ratio of Red to Far-red Radiation (R:FR) Throughout the Photoperiod but Not at End-of-day Promotes Shade Avoidance for Petunia ×hybrida Seedlings

Electric lighting is often necessary to achieve a target daily light integral (DLI) for the production of high-quality young annual bedding plants (plugs). Early in production, plugs have a low leaf area index that limits light interception and likely results in wasted radiation supplied by electric sources. Previous research has shown that the addition of far-red radiation (700–780 nm) to the radiation spectrum in sole-source lighting experiments or the use of end-of-day far-red (EOD-FR) radiation treatments can promote an increase in leaf expansion and leaf area for many species. However, leaf expansion in response to far-red radiation may depend on other factors such as the ratio of red (600–699 nm) to far-red radiation (R:FR) and air temperature. Thus, the objectives of this work were to examine the effects of far-red radiation applied throughout the photoperiod and as an end-of-day radiation treatment on the morphology of petunia ‘Dreams Midnight’ seedlings grown under different temperature conditions. Specifically, petunia seed was sown in 128-cell trays and moved to one of two growth chambers set at 16 or 21 °C when cotyledons unfolded. Seedlings received an equal total photon flux density (400–780 nm) of 164 µmol·m−2·s−1 for a 17.25-hour photoperiod, and either a high (∼10.7) or low R:FR (0.5). Low R:FR-treated seedlings were grown at a constant temperature of either 16 or 21 °C and placed under blackout conditions at the end of the photoperiod. High R:FR-grown seedlings received either a 1-hour end-of-day white (EOD-W) or EOD-FR treatment at the end of the photoperiod, and were grown at a constant 16 or 21 °C; one EOD-FR treatment was also shifted from the 21 °C chamber to the 16 °C at the end of the photoperiod for both the EOD-FR treatment and subsequent dark period. Seedlings were harvested at 21 and 28 days after treatment initiation. For petunia seedlings grown at 21 °C, EOD-FR treatments had minimal effect on morphology or dry mass as all measured parameters, including total and average leaf area and stem length, were similar to EOD-W treatments. In contrast, low R:FR-treated seedlings showed responses characteristic of plants grown under shade, including significant stem elongation, an increase in total and average leaf area, and a reduction in leaf mass per unit area. As expected, production at 16 °C slowed the growth of petunia seedlings resulting in much smaller plants compared with the 21 °C grown plants, but shade responses such as elongated leaves and stems under a low R:FR were apparent. The EOD-FR–treated seedlings that received the diurnal temperature shift also showed reduced leaf area and dry mass compared with their constant 21 °C counterparts. Shade responses were observable at both 16 and 21 °C for low R:FR-grown plants, but the quantifiable impact of temperature on far-red responses could not be fully determined in the present study. Further research is warranted investigating crop responses to far-red radiation as well as potential interacting environmental factors as the promotion of morphological responses, such as leaf expansion, early in production may prove a useful strategy.