A general expression for the thermodynamic relationship between liquidus and solidus equilibrium compositions is derived for systems which are nonideal but homogeneous and monotonic. For a number of typical systems, the nonideal term in this expression is found to be very small, thus indicating that the ideal form of the general expression can be used to calculate one of the boundaries of the two-phase field when the other one and the enthalpies of fusion of the pure components are known. For many of the systems examined (InAs–GaAs, InSb–InAs, InSb–GaSb, GaSb–AlSb, InSb–AlSb, CdTe–ZnTe, CdTe–CdSe, HgTe–CdTe, GeTe–MnTe, PbBr2–PbCl2), the solidus curves calculated by this method are in good to excellent agreement with the published experimental values; for the Ag–Au, InAs–InP, SnTe–PbTe, and PbTe–PbSe systems they confirm the results of the more recent and more dependable investigations; for the Cu–Ni, Ge–Si and HgTe–HgSe systems however, they suggest the need for a critical reevaluation of the presently available data. In the absence of pertinent experimental data, calculated solidus and liquidus curves, respectively, are also presented for the ZnTe–ZnSe and HgTe–ZnTe systems.

The ternary Zn‐Cd‐Te liquidus surface and the pseudobinary CdTe‐ZnTe solidus curve have been determined by thermal analysis of cooling and heating curves, respectively, of homogenized liquid and solid alloy samples. The binary Cd‐Te and Zn‐Te liquidus arrest temperatures are in good agreement with most of the previously published data and confirm the presence of well‐ defined inflections on the metal‐rich and Te‐rich sides of both liquidus curves. The binary interchange energy parameters calculated along each liquidus curve for the regular and quasi‐chemical approximation solution models give essentially similar values for dilute solutions. Near equiatomic composition however, they show values respectively in excess of 200 kcal/mole and less than 40 kcal/mole. The pseudobinary CdTe‐ZnTe liquidus and solidus curves exhibit monotonic and sublinear increases in temperature with increasing ZnTe content. The gap between the two curves remains less than 0.16 mole fraction and shows excellent agreement with the values calculated from the ideal liquidus‐solidus thermodynamic relationship. The ternary liquidus temperatures form a smooth surface with a narrow ridge near the pseudobinary CdTe‐ZnTe composition line and practically degenerate ternary eutectic and boundary lines.

The liquidus and solidus curves of the CdTe-CdSe pseudobinary system have been determined by thermal analysis of cooling and heating curves, respectively, for homogenized liquid and solid alloy samples. The phase diagram has a eutectie point at 1091 ~ • 1~ near 20 m/o (mole per cent) CdSe. Above the eutectic composition both liquidus and solidus temperatures increase monotonically and sublinearly with increasing CdSe content. In this region the experimental values of the liquidus-solidus gap do not exceed iI m/o and are in excellent agreement with the ideal thermodynamic liquidus-solidus relationship. The phase diagram below the solidus has been investigated by x-ray diffraction measurements on alloy powders annealed between 770 ~ and 1050~ and quenched. It consists of two broad single-phase regions, one of alloys with the zinc blende structure of CdTe and the other of alloys with the wurtzite structure of CdSe, separated by a two-phase region only about 3 m/o wide, whose boundaries shift toward increasing CdSe content with decreasing temperature. For compositions between 30 and 45 m/o CdSe, either structure could be obtained at room temperature, depending on annealing temperature and rate of cooling. In addition, a polytype of unknown structure, which appears to be a metastable intermediate in the wurtzite-to-zine blende transformation, was observed in two melt-grown furnace-cooled ingots containing 45-50 m/o CdSe.The II-VI compounds CdTe and CdSe have the cubic zinc blende and hexagonal wurtzite structures, respectively, when prepared by solidification of stoichiometric melts or nonstoichiometric Cd-Te or Cd-Se solutions.[Other methods of preparation can be used to obtain CdTe with wurtzite structure (1) or CdSe with zinc blende structure (2).] The phase diagram of the CdTeCdSe system has not been determined previously but x-ray diffraction studies (3, 4) on a limited number of samples prepared by solidifying stoichiometric melts indicate that pseudobinary solid solutions are formed over the entire composition range. According to these studies, undoped alloys containing less than about 40 m/o CdSe have the zinc blende structure, those containing at least 70 m/o CdSe have the wurtzite structure, and those with intermediate compositions may have either structure.In this investigation, the liquidus and solidus curves in the CdTe-CdSe pseudobinary system have been determined by thermal analysis measurements on homogenized liquid and solid alloy samples. The cubic-hexagonal transition in the solid phase has been studied by x-ray diffraction analysis of annealed and quenched alloy powders. The x-ray data show that the cubic and hexagonal phase fields are separated by a two-phase region about 3 m/o wide, whose boundaries shift toward increasing CdSe content with decreasing temperature. Therefore, within a certain composition range, alloys can be obtained with either cubic or hexagonal structure, as reported earlier (3, 4), depending on the annealing temperature and rate of cooling. In addition to these two phases, a p...

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`Candy Sunblaze' and `Red Sunblaze' miniature roses (Rosa L. sp.), were grown at several temperatures. The phenological events of budbreak (BB), visible flower bud (VB), and open flower (OF) were recorded daily. Based on these events, phenophases from BB to VB (BB:VB), from VB to OF (VB:OF), and from BB to OF (VB:OF) were defined. Daily rates of development to complete a phenophase increased with temperature between 13.6 and 27 °C. For `Candy Sunblaze', the rate of increase changed to a smaller slope beyond 25 °C. A piecewise linear regression change point model was fitted to each dataset. The base temperature (Tb) and the temperature at which the nonlinearity (Ti) occurred could then be determined. Tb for the phenophase BB:OF was 9.5 °C for `Candy Sunblaze' and 8.1 °C for `Red Sunblaze'. Ti for `Candy Sunblaze' was 24.9 °C for BB:VB and 25.6 °C for the phenophase BB:OF. The resulting point of change in rate of development prompted a modification of the traditional thermal unit formula. To complete the phenophase BB:OF using the modified formula, 479 degree days (°Cd) were predicted necessary for `Candy Sunblaze' and 589 °Cd for `Red Sunblaze'. Predicted time of events was compared with observed values. Subdividing BB:OF into BB:VB and VB:OF and using their respective Tb and thermal units summations (TU) reduced the average prediction error from 1.9 to 1.8 days for `Candy Sunblaze' and from 2.4 to 1.5 days for `Red Sunblaze'. In addition to single plant observations, phenological observations and thermal units were determined for pots with four plants to simulate commercial greenhouse crop production. Subdividing BB:OF into BB:VB and VB:OF and using their respective Tb and TU accumulations, reduced OF prediction errors on a crop basis for `Red Sunblaze', but was ineffective for `Candy Sunblaze'.

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Adiantum pedatum (maidenhair fern) is a fern commonly used in landscapes and interiorscapes for its attractive foliage. A. pedatum is quite hardy and under conditions of good soil fertility it can become highly intrusive if left unchecked. Maidenhair fern showing symptoms associated with possible virus infection were collected from the Chadwick Arboretum on the campus of The Ohio State University, Columbus. The leaves of the affected plants were slightly malformed such that the pinnules were arranged irregularly at the pinna. The sequence of the pinnae on the rachis and the general appearance of the rachis were distorted. Overall, the symptoms observed were not as severe as those described by Nienhaus et al. on other species of ferns (1). Viral-associated double-stranded RNA (dsRNA) analysis was used to analyze tissue from symptomatic and asymptomatic plants for evidence of virus infection. Results of dsRNA analysis gave evidence of a possible cucumovirus. There was no evidence of dsRNA in the asymptomatic tissue. Symptomatic tissue was subsequently tested for cucumber mosaic virus (CMV) with a direct antibody sandwich, enzyme-linked immunosorbent assay (ELISA). ELISA results were positive for CMV in symptomatic tissue and negative for CMV in asymptomatic tissue. This is the first report of a virus associated with a disease in A. pedatum. Reference: (1) F. Nienhaus et al. Z. Pflanzenkrankh. Pflanzenschutz 9:533, 1974.