Phosphorus Sites Research Articles

A Further Extension of Pnictide Oxide Chemistry – Synthesis and Structure of La2AuP2O

AbstractThe phosphide oxide La2AuP2O was synthesized from lanthanum filings, dried La2O3, gold pieces, and ground red phosphorus in the ideal 1.33:0.33:1:2 ratio in an evacuated silica tube at 1473 K. Small single crystals were obtained by recrystallization in a NaCl/KCl flux. The structure was determined on the basis of single‐crystal X‐ray diffractometer data: new type, C2/m, a = 1537.3(3), b = 427.39(8), c = 1009.2(2) pm, β = 131.02(1) °, wR2 = 0.046, 1102 F2 values, 38 variables. La2AuP2O contains two striking structural motifs: The oxygen atoms are located in La4 tetrahedra. The latter are cis‐edge‐shared forming polymeric cationic [La2O]4+ chains. These cationic units are separated and charge‐balanced by [AuP2]4– polyanions which have monovalent gold in distorted trigonal planar phosphorus coordination. Two crystallographically independent phosphorus sites occur in the polyanion, i.e. isolated P3– besides dumb‐bells P24– (P2–P2 223 pm). La2AuP2O, which crystallizes in the form of ruby red transparent crystals, is an electron precise phosphide oxide (4La3+)(2Au+)(2P3–)(P24–)(2O2–).

Marine‐derived Nutrients from Green Turtle Nests Subsidize Terrestrial Beach Ecosystems

AbstractSpatially separated ecosystems are often linked by nutrient fluxes. Nutrient inputs may be transferred by physical vectors (i.e., wind and water) or by biotic vectors. In this study, we examine the role of green turtles (Chelonia mydas) as biotic transporters of nutrients from marine to terrestrial ecosystems, where they deposit eggs. We compare low and high nest density sites at Tortuguero, Costa Rica, the largest green turtle rookery in the western hemisphere. Four plant species (Costus woodsonii, Hibiscus pernanbucensis, Hymenocallis littoralis, Ipomoea pes‐caprae) were analyzed at both nest density sites for 15N, total carbon, nitrogen, and phosphorus, and vegetation cover. Sand was analyzed for 15N and total nitrogen. Vegetation at high nest density sites had higher total nitrogen, which was correlated with higher δ15N values, suggesting nutrient input from a marine source. The dominant plant species changed between low and high nest density sites, indicating that turtle‐derived nutrients may alter the plant community composition. The trend in δ15N values of sand was similar, although less pronounced than that of the vegetation. Sand may be a poor integrator of nutrient input due to low nutrient adsorption and high rate of leaching. Sea turtles have previously been shown to deposit considerable amounts of nutrients and energy on nesting beaches. In this study, we estimate annual nitrogen and phosphorus contributions at Tortuguero are 507 and 45 kg/km, respectively, and we demonstrate that beach vegetation likely assimilates a portion of these marine‐derived nutrients.

Beyond the Limits of X-ray Powder Diffraction: Description of the Nonperiodic Subnetworks in Aluminophosphate-Cloverite by NMR Crystallography

NMR crystallography of the fluorinated aluminophosphate cloverite is presented, with an emphasis on the description of the nonperiodic part of the compound, i.e., the fluorine and organic subnetworks, which are very difficult to access by usual X-ray powder diffraction methods. Multinuclear high-resolution 1D Al-27 and P-31 NMR support the main cloverite-type topological features previously proposed for aluminum cloverite from powder X-ray diffraction. Spatial proximities are extracted from the 2D P-31-P-31 and Al-27-P-31 NMR spectra, allowing a full assignment of the P-31 and Al-27 resonances to the corresponding phosphorus and aluminum sites in the structure. To go further into the description of the main periodic framework, C-13, N-15, and H-1 1D and H-1-H-1 and H-1-P-31 2D NMR measurements are employed, allowing the characterization and selective locations of the two costructural-directing agents in the pores and channels of the framework. The nonperiodic fluorine subnetwork is described by means of F-19-X (X = Al-27 and P-31) 2D NMR experiments. Two kinds of fluorine atoms are distinguished: F- ions trapped in D4R units and F atoms covalently bonded to terminal Al or P atoms and which interrupt the AlPO network. Through the example of aluminum cloverite, we show that, despite the considerable complexity of such systems, an extremely detailed structural model can be obtained, including the simple rules that allow the description of the nonperiodic subnetworks that tailor the structure and properties of a compound, by coupling powder X-ray diffraction and high-resolution NMR data in a generalized crystallography approach.

Tissue and skeletal changes in the scleractinian coral Stylophora pistillata Esper 1797 under phosphate enrichment

Long-term phosphate enrichments (0, 0.5, and 2.5 μmol L − 1 ; 4 to 11 weeks) were used to assess a possible limitation in phosphorus of zooxanthellae and to complement data on the effect of phosphate enrichment on calcification and elemental composition of the tissue in the scleractinian coral Stylophora pistillata. Phosphate addition mainly affected the coral symbionts. Indeed, at 2.5 μmol L − 1 P-enriched, zooxanthellae had a greater photosynthetic efficiency, their intracellular carbon and nitrogen contents increased by 70% and their phosphorus content by 190%, while their specific growth rate increased by 18%. C:P and N:P ratios in zooxanthellae were much higher than the Redfield ratios advocated for nutrient-repleted phytoplankton, and decreased with phosphate enrichment. Collectively, these results suggest a phosphorus limitation of the zooxanthellae growth in hospite. However, the increase in zooxanthellae specific growth rate did not lead to the building of a higher symbiont density, as zooxanthellae growth just matched the tissue and skeletal growth of the enriched corals. Benefits of phosphate supplementation were thus not substantial enough to lead to the building of higher zooxanthellae density and to their balanced growth, which suggests that symbiont growth was likely limited by another nutrient as well, probably nitrogen. At the host level, there were no changes in the elemental composition or in the protein levels, while skeletal growth rate increased by 31% between unenriched and 2.5 μmol L − 1 P-enriched corals. Phosphate-enriched corals also incorporated 1.7 times more phosphorus into their skeleton than did unenriched corals. These results evidenced that zooxanthellae and the skeleton are the two accumulation sites of inorganic phosphorus within the symbiotic association.

Structural Characterization of Phosphorus‐Based Networks and Clusters: 31P MAS NMR Spectroscopy and Magnetic Shielding Calculations on Hittorf’s Phosphorus

The (31)P MAS NMR spectrum of Hittorf's phosphorus has been measured and assigned to the 21 crystallographically distinct phosphorus atoms based on two-dimensional dipolar correlation spectroscopies. Application of such 2D techniques to phosphorus-based networks is particularly challenging owing to the wide chemical shift dispersions, rapid irreversible decay of transverse magnetization, and extremely slow spin-lattice relaxation in these systems. Nevertheless, a complete assignment was possible by using the combination of correlated spectroscopy (COSY) and radiofrequency-driven dipolar recoupling (RFDR). The assignment is supported further by DFT-based ab initio chemical shift calculations using a cluster-model approach, which gives good agreement between experimental and calculated chemical shift values. The (31)P chemical shifts appear to be strongly correlated with the average P-P bond lengths within the P(P(1/3))(3) coordination environments, whereas no clear dependence on average P-P-P bond angles can be detected. Calculations of localized Kohn-Sham orbitals reveal that this bond-length dependence is reflected in energy variations in the corresponding localized p-p-σ orbitals influencing the paramagnetic deshielding contribution in Ramsey's equation. In contrast, the contributions of the lone pairs to shielding differences are small and/or do not vary in a systematic manner for the different crystallographically distinct phosphorus sites. The combined spectroscopic and quantum chemical approach applied here and the increased theoretical understanding of (31)P chemical shifts will facilitate the structural elucidation of other phosphorus-based clusters and networks.

Bismuth flux synthesis and structure of the iridium-rich phosphides RE7Ir 17P 12 ( RE = Y, Gd, Tb, Dy, Ho) with La 7Pd 17P 12 type structure

The iridium-rich phosphides RE 7Ir 17P 12 ( RE = Y, Gd, Tb, Dy, Ho) with La 7Pd 17P 12 type structure, space group C2/ m were synthesized from the elements in bismuth fluxes. The five structures were refined on the basis of X-ray single crystal diffractometer data. These phosphides have six crystallographically independent phosphorus sites which all have coordination number 9 in tricapped trigonal prismatic metal coordination. These prisms are condensed via common rectangular faces within one layer and via the triangular faces perpendicular to the layers. The second striking structural motif is the broad ranges of Ir–Ir distances within the complex iridium substructure. The RE 7Ir 17P 12 phosphides belong to the large series of metal-rich compounds with a metal:non-metal ratio of 2:1.

P22−and P3−Units in the [Rh8P9]δ−Polyanion of La4Rh8P9

The phosphide La(4)Rh(8)P(9) was synthesized from the elements in a bismuth flux. The structure was refined from single crystal diffractometer data: space group Cmcm, a = 1303.1(2), b = 1893.2(2), c = 576.70(6) pm, wR2 = 0.0277, 1380 F(2) values, 65 variables. The rhodium and phosphorus atoms build up a three-dimensional [Rh(8)P(9)] polyanion which leaves larger cages for the three crystallographically independent lanthanum sites. The rhodium atoms have between four and six phosphorus neighbors at Rh-P distance ranging from 229 to 254 pm. Three of the four crystallographically independent phosphorus atoms are isolated (P(3-) units), while the P4 atoms form dimers with double bond character (208 pm P-P). The P(2)(2-) diphosphenide units bond side-on to a Rh3 and end-on to four Rh5 atoms. (31)P magic angle spinning (MAS) NMR spectroscopy is able to resolve three of the four crystallographically distinct phosphorus sites. The doubly bonded phosphorus site P4 is characterized by an axially symmetric shielding tensor of moderate anisotropy Δσ = σ(33) - σ(iso) = 257 ppm. Electronic band structure calculations prove the metallic character and reveal the significant difference between the isolated P(3-) and the phosphorus atoms of the P(2)(2-) units. Magnetic susceptibility measurement reveals Pauli paramagnetism.

ScIrP with ZrNiAl-type Structure

The phosphide ScIrP was synthesized from the elements in a bismuth flux and characterized by powder and singlecrystal X-ray diffraction: ZrNiAl type, P6̄2m, Z = 3, a = 637.2(3), c = 389.2(2) pm, wR2 = 0.0280, 250 F2 values, 15 variables. The two crystallographically independent phosphorus sites have tricapped trigonal-prismatic metal coordination P1Ir3Sc6 and P2Ir6Sc3. The shortest interatomic distances occur for Ir-P (244 - 251 pm) within the 3D [IrP] network in which the scandium atoms fill cavities of coordination number 15 (4 Sc + 6 Ir + 5 P).

Estimating total net primary productivity of managed grasslands by a state-space modeling approach in a small catchment on the Loess Plateau, China

Managed grasslands are important for stabilizing soil and reducing soil erosion on sloping lands. In order to obtain information for better grassland management and soil protection at small scales, managed grassland total net primary productivity (TNPP) data were collected and analyzed with a first order state-space approach and a classical linear regression approach. The objective was to determine the effects of soil properties and site elevation on managed grassland TNPP. Soil water content (SWC), soil bulk density (BD), saturated soil hydraulic conductivity (Ks), soil temperature (T), soil clay content (CC), soil organic carbon (SOC), soil NO 3–N, soil NH 4–N, soil Olsen phosphorus concentration (OP) and site elevation (SE) data were collected along a 300-m transect in the China Loess Plateau. Soil properties and site elevation were evaluated in bi- and multivariate autoregressive state-space analysis to clarify the key factors affecting the spatial distribution of TNPP. Results show that most of the measured variables contributed to the variation of TNPP. CC and OP were especially helpful in describing the spatial pattern of TNPP. The state-space modeling results were compared with classical statistics methodologies, indicating that the state-space approach described the spatial pattern of TNPP much better than the equivalent classical regression methods. All of the TNPP variation was represented by state-space models that included soil NO 3–N and OP or soil CC and OP. Only 76% of the variance of the TNPP was represented by classical statistics analysis because the classical statistics did not include sampling position and assumed sample independence. State-space models are recommended for studying spatial relations between vegetation and soil variables in natural soil-plant systems on the China Loess Plateau.

Indirect Magnetic Coupling in Light-Element-Doped Single-Walled Carbon Nanotubes

Single-walled carbon nanotubes substitutionally doped with the light-element phosphorus are synthesized and are investigated by electrical and nuclear magnetic resonance measurements. Decreased spin-lattice relaxation times compared to undoped tubes point toward enhanced spin-sensitive scattering. Temperature dependence of the zero-bias conductance shows step-like features, a signature of scattering from a very low density (few sites per nanotube) of localized spin moments at oxidized phosphorus sites, consistent with density functional calculations. This supports recent predictions that localized magnetic moments must be indirectly magnetically coupled through the nanotube conduction electrons.

Cortical colonisation is not an absolute requirement for phosphorus transfer to plants in arbuscular mycorrhizas formed by Scutellospora calospora in a tomato mutant: evidence from physiology and gene expression

Arbuscules in Arum-type arbuscular mycorrhizas (AM), formed intracellularly in root cortical cells, are generally believed to be the most important and defining characteristics of the symbiosis as sites for phosphorus (P) and carbon (C) exchange. We used a Pen + Coi– phenotype (penetration of epidermal and exodermal root cells but not arbuscule formation) formed in rmc (reduced mycorrhizal colonisation) mutant tomato (Lycopersicon esculentum Mill.) by Scutellospora calospora (Nicol. & Gerd.) Walker & Sanders to determine whether the fungus is capable of transferring P from soil to plant and whether there is concurrent upregulation of AM-inducible orthophosphate (Pi) transporter gene expression in the roots. Our physiological data showed that colonisation of outer root cell layers is sufficient for P transfer from S. calospora to tomato. This transfer of P was supported by increased expression of the Pi transporter genes, LePT3 and LePT5, known to be upregulated in AM interactions. We conclude that cortical colonisation and formation of arbuscules or arbusculate hyphal coils is not an absolute prerequisite for P transfer in this symbiosis.

Characterization of the gel phases formed in the synthesis of microporous gallophosphate, cloverite

This work examines the formation of a microporous gallophosphate with an extra large pore system, namely cloverite (structure type: CLO) in fluoride medium. The amorphous gallophosphate gel containing the key precursor to cloverite was characterized and its evolution followed by 31P, 71Ga, 19F and 1H MAS NMR and several dipolar-coupling based double-resonance methods including 31P{71Ga} and 19F{71Ga} rotational-echo adiabatic passage double-resonance (REAPDOR), 31P{19F} and 19F{31P} rotational-echo double-resonance (REDOR), and 1H{31P} REDOR and 1H{71Ga} transfer of populations in double-resonance (TRAPDOR). The results indicate that upon mixing the Ga and P sources in the presence of structure directing agent (SDA) and HF, an amorphous oxyfluorinated gallophosphate precursor containing single 4-rings (4Rs) with alternating Ga–O–P linkage forms immediately. The Ga in the 4R is 6-coordinated and the two Ga in the 4R are bridged by a fluorine. Heating quickly converts the 4Rs to double four-membered rings (D4Rs), from which the entire CLO structure is built. The amount of the D4R rapidly increases with increasing heating time. The presence of fluoride ions greatly facilitates the formation of the 4Rs via bridging two Ga sites and the hydrothermal treatment promotes D4Rs via condensation. Interaction between SDA molecule and the phosphorus site in the gel is also probed. Further, the local structure of Ga sites in cloverite is characterized by 71Ga MAS NMR at ultrahigh magnetic field of 21.1 T by obtaining their electric field gradient tensor parameters.

Canada Goose Weed Dispersal and Nutrient Loading in Turfgrass Systems

High populations of Canada geese (Branta canadensis L.) can lead to feces accumulation in areas adjacent to surface waters, creating concern about aquatic eutrophication. Further, turf managers and livestock farmers work to keep their facilities free of noxious or toxic weeds that geese potentially disperse. We investigated the prevalence of viable seeds and nitrogen and phosphorus content in resident Canada goose droppings. During spring, summer, and fall of 2008, we collected 127 fresh individual droppings which were placed in seedling trays within an irrigated greenhouse and allowed 30 days for weed seed to germinate. Trays were cold stratified for 30 days and returned to the greenhouse for an additional 30 days. Also, during summer and fall of 2007 and 2008, we tested 304 fecal samples from 8 sites for total Kjeldahl nitrogen (TKN) and total phosphorus (TP). Out of 127 droppings planted, 4 plants germinated (3.1%): Pennsylvania smartweed (Polygonum pennsylvanicum L.), annual bluegrass (Poa annua L.), and 2 Kyllinga spp. The average amounts of TKN and TP in fecal samples were 24.2 mg/g (range = 12.6 to 55.7) and 3.6 mg/g (range = 1.4 to 8.3) of dry matter, respectively. The results indicate that Canada geese in suburban and urban areas are not frequent vectors of viable seeds, but do have potential to contribute nutrients to adjacent surface waters.

Sustaining Biosolids Recycling Under Phosphorus-Based Nutrient Management

Sustaining Biosolids Recycling Under Phosphorus-Based Nutrient ManagementNearly all states have developed phosphorus (P) site assessment tools (P indices) to rank agricultural fields based on vulnerability to P loss. Using the Pennsylvania P index, 95 active biosolids application fields were evaluated to quantify the impact of mandated P-based management on biosolids recycling. Under existing management, only 22 fields qualify for standard nitrogen (N)-based biosolids...Author(s)Robin C. BrandtHerschel A. ElliottSourceWater PracticeSubjectArticlesDocument typeConference PaperPublisherWater Environment FederationPrint publication date Oct, 2009ISSN1933-1770SICI1933-1770(20091016)3:1L.1;1-DOI10.2175/193317709X12526105489511Volume / Issue3 / 1Content sourceWater PracticeFirst / last page(s)1 - 14Copyright2009Word count158

Micronutrient intakes in two us populations of older adults: Lipid research clinics program prevalence study findings

Dietary intakes of several minerals and vitamins were assessed in two US sub-populations of older men and women between 60 and 80 years as part of the Lipid Research Clinics Program Prevalence Study conducted in the mid-1980s prior to widespread fortification. Dietary intakes were analyzed from 24-hour recalls using the Minnesota Nutrition Coding Center. Descriptive statistics on the two diverse sub-populations were generated for the elderly subjects at the two clinic sites, southern California and Oklahoma. Regression analyses of specific micronutrients were performed while controlling for several variables, namely, age, sex, clinic (region), education, Body Mass Index (BMI), alcohol consumption, and smoking status. Compared to current (1999–2004) Estimated Average Requirements (EARs) and Adequate Intakes (AIs) for three micronutrients without EARs for the US and Canada, several micronutrients were consumed at or close to their EAR values. Exceptions include intakes of vitamin A, vitamin E, folic acid, potassium and calcium which were very low; intakes of thiamin, riboflavin, niacin, and vitamin C were low but closer to the published EAR or AI values. High intakes approaching cut-offs for practically all subjects were found for both groups of elders at the two clinic sites for iron, phosphorus, and sodium. In general, California elderly had somewhat better consumption patterns for the vitamins, but the Oklahomans, males at least, had higher overall mineral intakes. The micronutrient deficits found in this small study suggest that most elderly US citizens were likely to be deficient in five micronutrients and marginally insufficient in four others in the mid-1980s and, despite even greater fortification currently, elderly intakes seem not to have improved substantially since the 1980s, except for subjects who are regular multi-supplement users.

A solid-state 31P NMR study of 1:1 silver–triphenylphosphine complexes — Interpretation of 1J(107,109Ag,31P) values,

High-resolution solid-state 31P NMR spectroscopy was used to investigate a series of 1:1 silver–triphenylphosphine complexes, [Ph3PAgX]n, where X is a monovalent anion and n = 1, 2, 3, 4, or ∞. The 31P CP MAS NMR spectra reveal the number of distinct phosphorus sites in these complexes as well as the |1J(109Ag,31P)| values, which range from 401 ± 10 Hz (X = N3–) to 869 ± 10 Hz (X = SO3CF3–). The data obtained here and in earlier investigations indicate that |1J(109Ag,31P)| values for silver–tertiary phosphine complexes decrease as Ag–P bond lengths increase. This experimental conclusion is supported by DFT calculations, which also indicate that the Fermi-contact mechanism is the only important spin–spin coupling mechanism for 1J(109Ag,31P) in these complexes. In addition, the crystal structure of a silver–triphenylphosphine trifluoroacetate tetramer was determined using X-ray crystallography, and the structure of a silver–triphenylphosphine chloride tetramer was reinvestigated.

Characterizing Slight Structural Disorder in Solids by Combined Solid-State NMR and First Principles Calculations

A general approach for structural interpretation of local disorder in partially ordered solids is proposed, combining high-resolution two-dimensional (2D) nuclear magnetic resonance (NMR) and first principles calculations. We show that small chemical shift variations of the order of a ppm can be interpreted in detailed structural terms with advanced density functional theory methods. Focusing on a model system of bisphosphinoamine, we demonstrate that the existence and the spatial range of small amplitude disorder can be probed using quantitative statistical analyses of 2D NMR line shapes obtained from through-space correlation experiments collected using variable mixing times. We show how low-energy vibration modes calculated from first principles can be conveniently used not as a cause of disorder but, instead, to generate a basis set of physically plausible local distortions to describe candidate static distributions of local geometries. Calculations of (31)P NMR isotropic chemical shifts are then used for the first time to simulate 2D correlation lineshapes associated with these distortions, which permit their evaluation as a potential source of disorder by comparison to experimental 2D cross-peaks between phosphorus sites. This new type of structural constraints allows the identification of changes in the bonding geometry that most likely contribute to the local structural disorder. We thus identify at least one type of structural deformation that is compatible with the experimental 2D NMR data and is also within the order of magnitude of the "thermal ellipsoids" associated with the uncertainties on the atomic positions of the X-ray diffraction structure.

Vanadium Modified LiFePO[sub 4] Cathode for Li-Ion Batteries

The structure and electrochemical behavior of vanadium-modified olivine was investigated. Vanadium was found to be incorporated into the olivine structure on the phosphorus site, not on the iron site, with the unit cell decreasing in size as the vanadium content increases. Material synthesized under reducing conditions with 5% vanadium gave materials with the best electrochemical performance. The rate capability of nanostructured was comparable to the best nanosized formed solvothermally while using less than the amount of carbon conductor. The vanadium does not appear to be electrochemically active within the voltage cycling window of .

Phosphorus‐31 Nuclear Magnetic Resonance Spectroscopy Transect Study of Poultry Operations on the Delmarva Peninsula

Nonpoint source phosphorus (P) pollution into the Chesapeake Bay watershed from poultry operations contributes to the algal blooms, hypoxia, anoxia, and fish kill events that occur there most years. A major source of soluble, bioavailable P species is poultry litter, which is used as a crop fertilizer on fields adjacent to the tributaries of the Bay. A potentially significant source of orthophosphate in the litter is the heavily phosphorylated compound myo-inositol hexakisphosphate (phytate), which is indigestible by poultry and thus becomes a major component of their excreta. Phytate evaluation in environmental samples is expensive; hence, its impact is not captured in standard farmer-friendly eutrophication potential guides, like Delaware's Phosphorus Site Index. In this transect study of two poultry operations on the Delmarva Peninsula, we measured the incidence of all P compounds using solution 31P nuclear magnetic resonance (NMR) spectroscopy and extracts, relating them to relevant geochemical properties. The contribution of phytate to the overall pool of P declined from around 50% in manures to between 2 and 13% in down-gradient soils and sediments, corresponding to a rise in the relative proportion of orthophosphate (increasing from 39% to 65-88%). The results show that the large pool of phytate P spread onto croplands during standard operating practice at poultry farms on the Delmarva Peninsula does not appear to accumulate; rather, phytate decreases in down-gradient locations, most likely due to transport off-site and/or through in situ biological activity.

Surface Reaction Kinetics of InP and InAs Metalorganic Vapor Phase Epitaxy Analyzed by Selective Area Growth Technique

The surface kinetic information of metalorganic vapor phase epitaxy (MOVPE) is difficult to obtain, because growth rate is normally limited by diffusional mass-transfer rate. In this study, by using a selective area growth (SAG) technique, the surface kinetics has been successfully clarified for InP and InAs growth. The temperature dependence of surface reaction rate constant (ks) was examined, and it revealed that for both compounds ks continuously increases with activation energies of 20.1 kJ/mol for InP and 15.0 kJ/mol for InAs. The sticking probability of indium species, converted from ks, was in the range of 0.54–0.79. This is two or three times that of gallium species during GaAs MOVPE. For indium-related binary compounds, the ks of InP is always larger than that of InAs. This kinetic information suggests that group V elements have a significant effect on the ks of III–V binary compounds. These preliminary results show that indium species have quite different reactivities in phosphorus and arsenic sites, which could be fundamental for the kinetic analysis of ternary and quaternary compounds, such as InAsP and InGaAsP.