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Nanoparticles and colloids functionalized by four single strands of DNA can be thought of as designed analogs to tetrahedral network-forming atoms and molecules, with a difference that the attached DNA strands allow for control of the length scale of bonding relative to the core size. We explore the behavior of an experimentally realized model for nanoparticles functionalized by four single strands of DNA (a tetramer), and show that this single-component model exhibits a rich phase diagram with at least three critical points and four thermodynamically distinct amorphous phases. We demonstrate that the additional critical points are part of the Ising universality class, like the ordinary liquid-gas critical point. The dense phases consist of a hierarchy of interpenetrating networks, reminiscent of a woven cloth. Thus, bonding specificity of DNA provides an effective route to generate new nano-networked materials with polyamorphic behavior. The concept of network interpenetration helps to explain the generation of multiple liquid phases in single-component systems, suggested to occur in some atomic and molecular network-forming fluids, including water and silica. DNA functionalization | nanoparticles | self-assembly | polyamorphism | nanotechnology

Hydrothermal circulation within oceanic crust depends on pressure (P) and temperature (T); the critical point (CP) of seawater at 298 bar and 407 [degrees]C represents the threshold between subcritical and supercritical conditions. Here we present data from the first hydrothermal system in which the sampled fluids fall on and above the CP. The vent system discovered at 5[degrees]S on the Mid-Atlantic Ridge is characterized by multiple fluid emanations at variable temperatures in water depths of ~3000 m. Vigorous vapor phase bubbling, stable emanation of superhot fluid at 407 [degrees]C, and decreased salinity indicate phase separation at conditions above the CP at one site. At another site the measured maximum T of 464 [degrees]C during a 20 s interval is by far the hottest fluid ever measured at the seafloor and falls into the vapor-phase supercritical region of seawater. Besides these two separate fields with ongoing phase separation and extremely hot fluids, a third vent field emanates non-phase-separated fluids at 349 [degrees]C and is used as a reference site. Fluid chemistry shows that supercritical fluids evolve differently than subcritical fluids, making this vent system a unique natural laboratory to investigate processes at high P-T conditions. The stability of the high temperature and fluid geochemistry measured in 2005 and 2006 after the assumed seismic trigger event in 2002 supports this as an exceptional site along the Mid-Atlantic Ridge. Keywords: hydrothermal, fluids, critical point of seawater, supercritical, phase separation.

The synthesis, crystal structure and dielectric properties of the novel double perovskite [Pb.sub.2]TmSb[O.sub.6] are presented. Dielectric permittivity measurements have shown the presence of a paraelectric/antiferroelectric transition, as suggested by the negative Curie temperature obtained from the Curie-Weiss fit of the reciprocal permittivity.

The mechanisms involved in the synthesis of the various high-Curie-temperature [Fe.sub.0.02][Ge.sub.0.98] quantum dots are explained. The application of the compound for the development of a new class of spintronics devices is also discussed.

A combination of the standard transmission and scanning electron microscope techniques is employed to explain the crystalline structures of the different permalloy narrow wires. The crystalline grains are shown to grow larger in the current region around the Curie temperature.

The article explains the microstructure, as well as the various magnetic properties that are exhibited by the Co-contained Finemet nanocrystalline alloys. The alloys are shown to exhibit completely enhanced soft magnetic properties after the full crystallization process.

The various effects of annealing and homogenization on the structure, as well as the magnetic properties of the [Mn.sub.1.1][Fe.sub.0.9][P.sub.0.8][Ge.sub.0.2] compounds are analyzed. Annealing is shown to lead to a significant increase in the Curie temperature and the magnetic entropy changes of the compounds.

The article studies effect of [Zn.sub.1-x][Mn.sub.x]Te light emitting devices under Curie-Weiss temperature. Findings suggest the presence of the acceptor bound magnetic polarons and their clusters in [Zn.sub.1-x][Mn.sub.x]Te crystals near the Curie-Weiss temperature.

A study of magnetic and reversible room-temperature magnetocaloric properties of antiperovskite compounds of [Ga.sub.1-x]C[Mn.sub.3+x] with large temperature span is reported. The results indicated the application of [Ga.sub.1-x]C[Mn.sub.3+x] as a promising candidate for magnetic refrigeration around room temperature.

Polycrystalline samples of UCoGe doped by Fe, Ni and Ru are prepared. The increasing Curie temperature ([T.sub.C]) value and stabilization of magnetic moments induced by the transition moments doping are accompanied by a shift in the superconducting transition to lower temperatures with respect to pure UCoGe.

Polycrystalline [Bi.sub.1/2][Sr.sub.1/2]Fe[O.sub.3] is prepared by solid state reaction method and its multiferroic properties are analyzed. The single phase material has displayed ferrimagnetism and ferroelectricity with magnetic and electrical Curie transitions and the superexchange interaction between Fe ions is used for discussing the origin of the spontaneous magnetic disorder.

Rosenweig's theory has shown that particle size dependence on RF magnetic heating of ferrofluids is determined by magnetic moment, magnetic anisotropy and the viscosity of the fluid. The materials are modeled with Curie temperatures near room temperature for which the magnetic properties are strongly T dependent to solve the problem of self-regulated heating of ferrofluids.

[Gd.sub.5][([Si.sub.x][Ge.sub.1-x]).sub.4] has displayed a field induced first order phase transition from a monoclinic paramagnetic to an orthorhombic ferromagnetic at temperatures above its Curie temperature. The field induced first order phase transition is observed above the projected second order phase transition temperature of the orthorhombic phase, which is attributed to the fact that the applied field is so high that it causes the broadening to a wide range of higher temperatures of the second order phase transition of the orthorhombic phase.

Crystallographic orientation and the magnetocaloric effect in single crystals of manganese phosphide (MnP), a material displaying a first-order ferromagnetic to paramagnetic transition at a Curie temperature of 290 K, are analyzed. The density and [DELTA]S of MnP is measured, whereas no hysteresis or irreversibility is measured over a range of temperatures from 10 to 300 K.

The Arrott-Noakes equation of state has shown that the Curie point (T.sub.C] and the temperature where the magnetic entropy change is maximum ([T.sub.peak]) coincide only in the mean field approximation, but the Heisenberg model has implied that [T.sub.peak]>[T.sub.C] even for homogeneous materials. The studies have shown that the field dependence of the magnetic entropy change is exactly the same at the Curie temperature and at the temperature of the peak.

Unconventional exchange bias (EB) is studied in Co[Cr.sub.2][O.sub.4]/[Cr.sub.2][O.sub.3] nanocomposites, in which the Curie temperature of the ferrimagnetic Co[Cr.sub.2][O.sub.4] is lower than the Neel temperature of the antiferromagnetic [Cr.sub.2][O.sub.3]. Cooling field has played a decisive role in the creation of the interfacial spin configuration for the unconventional EB, not only by exchange interaction between the induced magnetization of a polarized paramagnet and interfacial spins of an antiferromagnet but also by Zeeman interaction between the domain-state surplus magnetization and the external field.

The perovskite-type phases of SrMo[O.sub.2]N were treated in the temperature range of 3 K

The dependence of the measured magnetocaloric effect on the demagnetization factor of a number of thin sheets of gadolinium is analyzed. The demagnetization factor can be varied by changing the orientation and number sheets and the average internal field is calculated in the Gd sheets.

The effects of lanthanum efficiency on the structural and magnetic properties of manganites with normal composition [La.sub.0.7-x][Sr.sub.0.03]Mn[O.sub.3] prepared by sol-gel method with the highest heat treatment temperature are examined by using X-ray diffraction (XRD). The ion ratios are used in Rietveld fitting of the XRD spectra and the dependence of the Curie temperature on the content ratio [R.sub.M4] of [Mn.sup.4+] ions at B site is similar to that of the perovskite [La.sub.1-x][Sr.sub.x]Mn[O.sub.3].

A memory concept based on the interfacial exchange energy between itinerant holes in a quantum dot and magnetic ions in an adjacent magnetic insulator is examined. The results have shown the possibility of room temperature operation, given the availability of insulating ferromagnetic or antiferromagnetic materials whose Curie temperature is above room temperature.