Narrow Results

Lichen samples were collected and observations about lichen communities were recorded at sites in the intermountain western United States. Specifically the states of Idaho, Montana, Wyoming, Nevada, Utah, Colorado, Arizona, and New Mexico were included in this study. The minor and trace-element concentrations in many of the lichens collected were determined by proton induced X-ray emission (PIXE). These data are part of a base line assessment of current air pollution conditions in this region. These data also provide an opportunity to study some aspects of lichen physiology. Using the data from 508 foliose and fruticose lichens, frequency distributions for concentrations of phosphorus and calcium are considered. Phosphorus has a closely-spaced, bimodal distribution: one mode for foliose lichens and one mode for fruticose lichens. This suggests that all lichen genera in this study have similar requirements and absorption mechanisms for phosphorus. Calcium has a complex frequency distribution and concentrations that range from 450 mg/kg to 14 % dry weight. Contributions to this complex distribution pattern can be understood if the data are resolved into growth form, genera within each growth form, and in some cases species within a given genus. This complex dependence on calcium is strong evidence that lichens develop specific calcium-related adaptations in order to accommodate various habitat conditions.

The increase of nutrients in lakes typically stimulates the growth of algae in this environment. Therefore, it is important to understand the connection between nutrient concentration and algal biomass to manage the water pollution caused by excessive plant nutrients. It is worth observing that phosphorus and nitrogen are often considered as the principal limiting nutrients for aquatic algal production due to their short supply compared to cellular growth requirements. In freshwaters, phosphorus is the least abundant among the nutrients needed in large quantity by photosynthetic organisms, hence this is the primary nutrient that limits their growth. The purpose of this work is to compare the effects of nitrogen and phosphorus on the growth of algae in lakes. By using a sensitivity analysis technique, we found that the sources of phosphorus provide a greater risk for bloom of algae than that of nitrogen. Therefore, to reduce the occurrence of algal bloom more attention should be paid for the control of phosphorus input into the lake but the inflow of nitrogen cannot be ignored. The existence of a transcritical bifurcation is discussed and its direction is investigated by applying the projection method technique. Further, to make the system more realistic, time delay involved in the conversion of detritus into nutrients is considered. We show that for increasing values of time delay, the system undergoes an Andronov–Hopf-bifurcation. Some simulations are presented to verify the analytical findings. The results of our study can be helpful for the policy makers to mitigate algal blooms from lakes.

We develop a six-compartment model consisting of phosphorus, detritus, phytoplankton, zooplankton, planktonivorous fish and pisciphagous fish. In this model, we study the implications that the body sizes of phytoplankton and zooplankton have on the system dynamics. We use ascendency as a goal function or indicator of system performance. Ascendency quantifies growth and development of an ecosystem as a product of total system throughflow and the mutual information inherent in the pattern of internal system flows. Different physiological rate parameters of phytoplankton and zooplankton are assessed by means of allometric relationships applied to their body sizes. We let the phytoplankton body size range from 10 μm³ to 10⁷ μm³ and the zooplankton body size range from 10 μm³ to 10⁴ μm³ in volume. We also investigate the effects of phosphorus input conditions, corresponding to oligotrophic, mesotrophic and eutrophic systems on system dynamics. Ascendency (to be maximized over phytoplankton and zooplankton sizes) was computed after the system had reached a steady state. Since it always was a seasonal cycle, and the ascendency followed this behavior, we averaged the ascendency over 365 successive days (duration of one year) in the oscillatory phase. Under all types of nutrient conditions, the smallest phytoplankton size yielded the maximal values of the ascendency, while the corresponding zooplankton size varied. Under oligotrophic conditions, a phytoplankton size of 10 μm³ combined with a zooplankton size of 10^1.25 μm³ to give the maximum value of the ascendency. Under mesotrophic and eutrophic conditions, maxima were obtained for zooplankton sizes 10^2.26 μm³ and 10^3.20 μm³, respectively.

In this study, we investigate the effects of excessive inputs of bioavailable phosphorus into a lake from agricultural fields and households on algal bloom formation, and its potential management by using the lanthanum-modified clay Phoslock as a bioavailable phosphorus adsorbent. We also investigate the impact of time delay involved in the process of applying Phoslock after measuring the density of algal biomass in the lake. Moreover, the seasonal effects in the input of bioavailable phosphorus from the agricultural lands and the application rate of Phoslock have been investigated. Our simulation results show that the algal growth accelerates if the bioavailable phosphorus is excessively loaded through agricultural runoff and domestic discharges. However, algal biomass can be effectively controlled by employing Phoslock in a sufficiently large quantity. Further, we find that a delay in the application of Phoslock induces limit cycle oscillations. Furthermore, our findings show that the combined actions of delay and periodicity in the application of Phoslock bring forth dynamical complexity in the lake system by giving rise to higher periodic solutions and bursting patterns. Lastly, we investigate an optimal control problem to estimate the optimum dosage of Phoslock for the mitigation of algal biomass from the lake system.

The dynamics of consumers can be affected by both nutrient-deficient food (low phosphorus (P) to carbon (C) ratio) and nutrient-excessive (high P:C) food, which is known as the stoichiometric knife-edge phenomenon. In this study, aiming to illustrate the responses of herbivores and omnivores to food with excessive P content, we present and analyze a tri-trophic level stoichiometric knife-edge model incorporating the intraguild predation structure. The model dynamics are theoretically examined, including the boundedness and positivity of solutions, the existence and stability of boundary equilibria, and the existence of positive equilibria. Numerical simulations show that the model has complex dynamics, encompassing chaotic-like oscillations, multiple types of bifurcations, long transients, and regime shifts. Moderate P levels facilitate the coexistence of the three species, whereas both lower and higher P levels result in the extinction of herbivores and omnivores. Specifically, the energy enrichment paradox occurs at low P levels. In contrast, the nutrient enrichment paradox occurs at high P levels, both of which are detrimental to the survival of herbivores and omnivores. Furthermore, the high-intensity predation of producers by omnivores helps to restrain the occurrence of chaotic dynamics. These findings contribute to a deeper understanding of the mechanisms of multi-species coexistence.

This paper reports on the successful deposition of phosphorus (P)-doped n-type (p-C:P) carbon (C) films, and fabrication of n-C:P/p-Si cells by pulsed laser deposition (PLD) using graphite target at room temperature. The cells performances have been given in the dark I–V rectifying curve and I–V working curve under illumination when exposed to AM 1.5 illumination condition (100mW/cm², 25°C). The n-C:P/p-Si cell fabricated using a target with the amount of P by 7 weight percentages (Pwt%) shows the highest energy conversion efficiency η = 1.14% and fill factor FF = 41%. The quantum efficiency (QE) of the n-C:P/p-Si cells are observed to improve with Pwt%. The dependence of P content on the electrical and optical properties of the deposited films and the photovoltaic characteristics of the n-C:P/p-Si heterojunction solar cell are discussed.

The successful deposition of boron (B)-doped p-type (p-C:B) and phosphorous (P)-doped n-type (n-C:P) carbon (C) films, and fabrication of p-C:B on silicon (Si) substrate (p-C:B/n-Si) and n-C:P/p-Si cells by the technique of pulsed laser deposition (PLD) using graphite target is reported. The cells' performances are represented in the dark I–V rectifying curve and I–V working curve under illumination when exposed to AM 1.5 illumination condition (100 mW/cm², 25°C). The open circuit voltage (V_oc) and short circuit current density (J_sc) for p-C:B/n-Si are observed to vary from 230–250 mV and 1.5–2.2 mA/cm², respectively, and to vary from 215–265 mV and 7.5–10.5 mA/cm², respectively, for n-C:P/p-Si cells. The p-C:B/n-Si cell fabricated using the target with the amount of B by 3 Bwt% shows highest energy conversion efficiency, η = 0.20%, and fill factor, FF = 45%, while, the n-C:P/p-Si cell with the amount of P by 7 Pwt% shows highest energy conversion efficiency, η = 1.14%, and fill factor, FF = 41%. The quantum efficiencies (QE) of the p-C:B/n-Si and n-C:P/p-Si cells are observed to improve with Bwt% and Pwt%, respectively. The contributions of QE are suggested to be due to photon absorption by carbon layer in the lower wavelength region (below 750 nm) and Si substrates in the higher wavelength region. The dependence of B and P content on the electrical and optical properties of the deposited films, and the photovoltaic characteristics of the respective p-C:B/n-Si and n-C:P/p-Si heterojunction photovoltaic cells, are discussed.

This paper reports on the successful deposition of boron (B)-doped p-type (p-C:B) and phosphorus (P)-doped n-type (p-C:P) carbon (C) films, and the fabrication of p-C:B on silicon (Si) substrate (p-C:B/n-Si) and n-C:P/p-Si cells by a pulsed laser deposition (PLD) technique using a graphite target at room temperature. The boron and phosphorus atoms incorporated in the films were determined by X-ray photoelectron spectroscopy (XPS) to be in the range of 0.2–1.75 and 0.22–1.77 atomic percentages, respectively. The cells performances have been given in the dark I–V rectifying curve and I–V working curve under illumination when exposed to AM 1.5 illumination conditions (100 mW/cm², 25°C). The open circuit voltage (V_oc) and short circuit current density (J_sc) for p-C:B/n-Si are observed to vary from 230 to 250 mV and from 1.5 to 2.2 mA/cm², respectively; they vary from 215 to 265 mV and from 7.5 to 10.5 mA/cm², respectively, for n-C:P/p-Si cells. The p-C:B/n-Si cell fabricated using the target with the amount of boron by 3 weight percentages (Bwt%) showed the highest energy conversion efficiency, η = 0.20% and fill factor, FF = 45%. The n-C:P/p-Si cell fabricated using the target with the amount of 7 Pwt% showed the highest η = 1.14% and FF = 41%. The quantum efficiency (QE) of the p-C:B/n-Si and n-C:P/p-Si cells were observed to improve with Bwt% and Pwt%, respectively. The contribution of QE in the lower wavelength region (below 750 nm) may be due to photon absorption by the carbon layer, in the higher wavelength region it was due to the Si substrates. In this paper, the dependence of the boron and phosphorus content on the electrical and optical properties of the deposited films and the photovoltaic characteristics of the respective p-C:B/n-Si and n-C:P/p-Si heterojunction solar cells are discussed.

Hypereutectic Al-Si alloys are widely utilized in the automotive industry due to their high strength-to-weight ratio, minimal thermal expansion, and superior castability. The downside of hypereutectic Al-Si alloys is the formation of coarse primary silicon particles. The primary Si phases were controlled by the growth-hindering agents, phosphorus (refiner), and strontium (modifier) by using a conventional stir casting technique at room temperature. The microstructural changes were observed through an optical microscope and SEM analysis. The additions of 0.08% P have ensured the formation of the uniformly distributed fine-grained particles in the alloy. The primary silicon particle size was reduced from 220$\mu$m to 150$\mu$m as compared to the untreated alloy. The tensile and yield properties of the treated alloy were increased by 12.7% when compared to the untreated alloy with a hardness of 131 BHN. The treated alloy imparted better impact toughness, ensuring a ductile mode of failure through the fractography studies. The influence of the microstructure on the machinability of the alloy was investigated in a dry environment with uncoated and coated inserts (code: CCGT 09T304 FL K10) by varying the process parameters, i.e. speed, feed rate, and depth of cut (DoC). Modification of the primary and eutectic Si phases of an Al-20Si hypereutectic alloy increases machinability with coated inserts as well as its mechanical properties.

Nitrogen (N) and phosphorus (P) concentrations in tributaries and bays of the Three Gorges Reservoir area increase significantly after impoundment. It will affect processes such as coalescence/dispersion of soil colloidal particles, which in turn will affect the ecological safety of the reservoir water bodies. We analyzed the aggregation process of purple soil colloidal particles, and found that aggregation was controlled by the interaction of N and P. With the increase of N and P concentration in the water body, purple soil colloidal particles transformed from slow aggregation (represented by linear growth) to fast aggregation (represented with a power function). We chose three forms of purple soil (acidic, calcareous, and alkaline) to check how interactions between nutrients and physical aggregation processes may vary across soil types. Average aggregation rate (TAA) of the three purple soils differed significantly, and the critical coalescence concentration (CCC) of neutral, alkaline, and acidic purple soils was 220.14, 117.49, and 47.20mmolL${}^{-1}$ and 507.49, 437.15, 328.30mmolL${}^{-1}$, respectively. Compared to phosphorus, the nitrogen system has higher TAA and lower CCC, indicating that nitrogen is more effective in triggering colloidal aggregation of purple soils. In the N and P systems, the surface potentials of neutral, alkaline and acidic purple soils decreased from −172.85mV to −70.28mV and −187.65mV to −81.98mV, respectively. With the increase of N and P concentrations, the surface charge density and the absolute surface potential values of the three purple soil colloids decreased, the surface potentials of the three purple soil colloids (absolute values) at the same concentration showed that P was greater than N. Meanwhile, the activation energy of interaction of all three purple soil colloids decreased continuously with the increase of N and P concentrations, and the activation energy of interaction in the N system was significantly lower than that in the P system under the same concentration conditions. Theoretical calculations showed that N and P changed the surface charge properties of the soil and increased the net gravitational force between colloidal particles, which made the net force behave as attraction and colloidal particles were more likely to agglomerate. When the N and P concentrations increased to 0.2, 0.1, 0.05molL${}^{-1}$, and 0.5, 0.4, 0.3molL${}^{-1}$, respectively, they were basically consistent with their CCC values. The net force between the three purple soil particles was negative and behaved as attraction. The surface potentials at the corresponding concentrations were all about −125mV. This study showed that N and P in the water body ultimately affected the aggregation process of soil colloids by changing the surface charge properties of particles, which in turn causes changes in the interaction forces and activation energy between colloidal particles.

Phosphorus (P) is one of the main triggering nutrients responsible for eutrophication which troubles many waters in China. This study was to investigate the influencing factors of limestone (LS) adsorption and establish the parameter of constructed wetland (CW) using LS as the main substrate when treating effluent from a municipal wastewater treatment plant (MWTP) for P removal. First, a series of batch experiments were conducted to study the influencing factors of LS adsorption. Consequently, the P removal efficiency increased with the temperature and was high during the initial 3 h; the efficiency was over 75% even at initial P content 50 mg/L; under 2 mm small LS particle size enhanced the adsorption but the difference was not significant; the efficiency was over 90% when initial pH was below 6.37 and decreased sharply at pH above 8.15; sodium chloride as background electrolyte decreased the adsorption; organic acids including tartaric acid, oxalic acid and citric acid all suppressed the adsorption, and citric acid demonstrated the strongest effect. Then column experiment was conducted to evaluate the effect of the continuous vertical-flow LS bed treating effluent from a MWTP with varying hydraulic retention time (HRT). Over 80 days, the effluent pH was between 7 and 9, and effective running time increased with HRT during which the effluent total P content was below 0.5 mg/L. Short HRT such as 1 h or 1.5 h was recommended for dynamic LS adsorption. It showed that LS was suitable for the substrate in CW for P removal in wastewater advanced treatment.

The structures, vibrational frequencies and adiabatic ionization energies of HPCN and HNCP are calculated at several levels of theory. The adiabatic ionization energy of HPCN is found to be 10.16 eV at the G3 level of theory. The singlet state of HPCN⁺ is found to be approximately 1.3 eV below the lowest energy triplet state (ã³A″). Both states have a bent equilibrium molecular geometry. The adiabatic ionization energy for HNCP is calculated to be 8.30 eV at the G3 level of theory. In contrast to HPCN⁺, the triplet state of HNCP⁺ is lower in energy than that of the singlet state (ã¹A′) by approximately 1 eV. Also, the triplet state of HNCP⁺ is linear in contrast to that of HPCN⁺ due to the larger interaction between neighboring 2p orbitals on the central atoms in HNCP⁺ relative to the interaction between the 3p and 2p orbitals on the central atoms in HPCN⁺. Simulated photoelectron spectra (PES) are presented for the transitions producing both the singlet and triplet ion states of both isomers. As predicted by the dramatic geometry change in the case of , there is a long progression in the bending mode of the cation in the simulated PES.

An important technological problem is solved by numerical methods. Doping of silicene with phosphorus allows changing the morphology of the walls of the silicene channel without reducing their strength. The structure of lithium packings in the channels is studied in detail. The distribution of normal stresses in the walls of the channel before lithium intercalation and after complete lithium filling is determined. The calculated densities of electronic states allow us to conclude that both doped and undoped silicene on a graphite substrate become electrically conductive. The studied two-dimensional silicene can be used as an anode for next-generation lithium-ion batteries.

Recent advances in the chemistry of main group porphyrin complexes are surveyed. New, unprecedented structural types for porphyrin complexes which have been revealed from the recent reports of boron and tellurium porphyrins are described. Advances in the preparation and reactivity of Group 14 (silicon and tin) and Group 15 porphyrin complexes are discussed. A systematic variation in the out-of-plane distortion (ruffling) of light element Group 14 and 15 porphyrin complexes has become apparent now that a significant number of structurally characterized examples are at hand.

A novel phthalocyanine-like photosensitizer, oxophosphorus(V) tetrasulfotriaza-tetrabenzcorrole (POTBCS₄), has been synthesized. Its structure and absorption spectrum are unique. POTBCS₄ has an axial P=O group and peripheral sulfo groups. The fluorescence emission spectra, fluorescence quantum yield and quantum yield of singlet oxygen generation have been studied. The uptake and the photodynamic activities against HeLa cells were measured. The results indicated that POTBCS₄ was a potential photosensitizer for photodynamic therapy (PDT).

Organometallic porphyrins with a metal, metalloid or phosphorus fragment directly attached to their carbon framework emerged for the first time in 1976, and these macrocycles have been intensively investigated in the past decade. The present review summarises for the first time all reported examples as well as applications of these systems.

Octa-(meta-methoxyphenyl) substituted tetraazaporphyrin (TAP, 1) and corrolazine (Cor, 4) phosphorus(V) complexes have been synthesized and characterized. 1 has a blue-shifted, small charge transfer (CT) band while para-methoxyphenyl substituted PTAP 2 has a red-shifted, intense CT band. The difference could be interpreted as an inductive effect of the meta-methoxy groups. The position and intensity of the absorption bands of 1 are well matched to the trend of para-substituted PTAPs. The synthesis of PCor from free-base TAP was also investigated. The PCor was not generated directly but from a PTAP intermediate

meso-Tetra(3,4,5-trimethoxy)phenyl-porphyrin and -tetrabenzoporphyrin and their phosphorus complexes were synthesized and their electronic absorption and magnetic circular dichroism (MCD) spectra discussed based on TD-DFT molecular orbital (MO) calculations. Nucleus-independent chemical shift (NICS) and anisotropy of the induced current density (ACID) calculations were also carried out for metal-free (and phosphorus) tetrabenzoporphyrins in order to discuss the aromaticity and flow of electrons in the molecule.

The Pd–P selective catalyst for liquid-phase hydrogenation of o-chloronitrobenzene (o-CNB) was obtained by the reduction of Pd(acac)₂ with hydrogen at 80^∘C in the presence of white phosphorus (P/Pd = 1) in N,N-dimethylformamide (DMF). It has been shown [(high-resolution transmission electron microscopy (HRTEM), energy dispersive X-ray spectroscopy (EDX), X-ray powder diffraction (XRD)] that such low-temperature synthesis of the Pd–P catalyst affords nanoparticles of palladium phosphides (Pd₅P₂, PdP₂), the Pd₅P₂ phosphide being prevailing. On the nanoparticle surface, palladium is present as a phosphide (BE (Pd3d_5∕2) = 336.2 eV; BE (P2p_3∕2) = 130 eV) and as palladium clusters of ≈ 1 nm in diameter. The formation of the Pd–P catalyst proceeds through a number of stages: a redox process between Pd(acac)₂ and white phosphorus affording mainly PdP₂ nanoparticles, H₃PO₃ and acacH; next follows the reduction of unreacted Pd(acac)₂ with hydrogen at 80^∘C and the reaction of Pd(0) atoms with each other and with PdP₂. It is assumed that formation of small palladium clusters on the surface of the Pd₅P₂ nanoparticles ensures the high selectivity of the Pd–P catalyst in the o-CNB hydrogenation.

Sodium-ion batteries (SIBs) have received widespread attention because of their scalability, low cost, and environmental advantages. Whereas, the low capacity and disappointing cycle capability of anode materials are unavoidable challenges, and high-capacity electrodes are accompanied by large volume expansion and cycle decay. Herein, self-supported TiO₂ nanotube array nanocomposites are rationally designed by combining the stability of TiO₂ and the high capacity of $P$. The unique nanotube structure can effectively limit the expansion of phosphorus so that this anode has excellent reversibility and cycling. It affords a reversible capacity of 0.214 mAh cm${}^{-2}$ at 0.08 mA cm${}^{-2}$, a rate capability of 0.146 mAh cm${}^{-2}$ at 1.6 mA cm${}^{-2}$, and a stable cycling up to 5000 cycles.