The existence of temporal correlations during the intermittent dynamics of a thermally driven structural phase transition is studied in a Cu-Zn-Al alloy. The sequence of avalanches is observed by means of two techniques: acoustic emission and high sensitivity calorimetry. Both methods reveal the existence of event clustering in a way that is equivalent to the Omori correlations between aftershocks in earthquakes as are commonly used in seismology.

This work analyzes time use surveys from 19 countries (17 European and 2 American) in the middle latitude (38–61 degree) accounting for 45% of world population in this range. Time marks for primary activities are contrasted against light/dark conditions. The analysis reveals winter sunrise synchronizes labor start time below 54 degree, occurring within winter civil twilight. Winter sunset is a source of synchronization for labor end times. Winter terminator punctuate meal times in Europe: dinner occurs 3 h after winter sunset time within 1 h; 40% narrower than variability of dinner local times. The sleep-wake cycle of laborers is shown to be related to winter sunrise whereas standard population’s appears to be irrespective of latitude. The significance of the winter terminator depends on two competing factors average labor time (~7 h30 m) and the shortest photoperiod. Winter terminator gains significance when both roughly matches. That is within a latitude range from 38 degree to 54 degree. The significance of winter terminator as a source of synchronization is also related to contemporary year round time schedules: the shortest photoperiod represents the worst case scenario the society faces.

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Heat treatment induced martensitic accommodation and adaptive anisotropy in melt spun Ni55Mn22Ga23 (at. %) ribbons J. Appl. Phys. 112, 103512 (2012) Modulated structure in the martensite phase of Ni1.8Pt0.2MnGa: A neutron diffraction study Appl. Phys. Lett. 101, 171904 (2012) Martensitic and magnetic transformation in Mn50Ni50−xSnx ferromagnetic shape memory alloys J. Appl. Phys. 112, 083902 (2012) Ellipsometry applied to phase transitions and relaxation phenomena in Ni2MnGa ferromagnetic shape memory alloy Appl.

The asymptotic behaviour near phase transitions can be suitably characterized by the scaling of ∆s/Q 2 with ǫ = 1 − T /T c , where ∆s is the excess entropy and Q is the order parameter. As ∆s is obtained by integration of the experimental excess specific heat of the transition ∆c, it displays little experimental noise so that the curve log(∆s/Q 2 ) versus log ǫ is better constrained than, say, log ∆c versus log ǫ. The behaviour of ∆s/Q 2 for different universality classes is presented and compared. In all cases, it clearly deviates from being a constant. The determination of this function can then be an effective method to distinguish asymptotic critical behaviour. For comparison, experimental data for three very different systems, Rb 2 CoF 4 , Rb 2 ZnCl 4 and SrTiO 3 , are analysed under this approach. In SrTiO 3 , the function ∆s/Q 2 does not deviate within experimental resolution from a straight line so that, although Q can be fitted with a non mean-field exponent, the data can be explained by a classical Landau mean-field behaviour. In contrast, the behaviour of ∆s/Q 2 for the antiferromagnetic transition in Rb 2 CoF 4 and the normal-incommensurate phase transition in Rb 2 ZnCl 4 is fully consistent with the asymptotic critical behaviour of the universality class corresponding to each case. This analysis supports, therefore, the claim that incommensurate phase transitions in general, and the A 2 BX 4 compounds in particular, in contrast with most structural phase transitions, have critical regions large enough to be observable.

We have performed simultaneous measurements of heat capacity and dielectric constant on a high-quality single crystal of Rb 2 ZnCl 4 near the commensurate-incommensurate transition area. Maximum heat capacity is found to be at a higher temperature than the maximum dielectric constant, both for heating and cooling and in the area of a jump-wise change of the refractive index found earlier. When measuring heat capacity a peak-type anomaly was detected and the enthalpy of transition was measured. We compare our heat-capacity data with those for the powder samples and both sets with a phenomenological theory. We concluded that the Curie law for heat capacity predicted by the theory is observed in both cases with reasonable values for the Curie constant. We were unable to discriminate latent heat as in previous experiments with the powder sample; however, we estimated an upper limit for the latent heat by subtracting the contribution of specific heat to the enthalpy transition. The latent-heat value estimated both from the Clapeyron-Clausius formula and the phenomenological theory is qualitatively in accordance with the upper limit of this value found in our results.

We studied the two-step martensitic transition of a Cu-Al-Ni shape-memory alloy by calorimetry, acoustic emission (AE), and resonant ultrasound spectroscopy (RUS) measurements. The transition occurs under cooling from the cubic (β, F m3m) parent phase near 242 K to a mixture of orthorhombic 2H and monoclinic 18R phases. Heating leads first to the back transformation of small 18R domains to β and/or 2H near 255 K, and then to the transformation 2H to β near 280 K. The total transformation enthalpy is H T = 328 ± 10 J/mol and is observed as one large latent heat peak under cooling. The back-transformation entropy under heating breaks down into a large component 18R to β at 255 K and a smaller, smeared component of the transformation 2H to β near 280 K. The proportions inside the phase mixture depend on the thermal history of the sample. The elastic response of the sample is dominated by large elastic softening during cooling. The weakening of the elastic shear modulus shows a peak at 242 K, which is typical for the formation of complex microstructures. Cooling the sample further leads to additional changes of the microstructure and domain wall freezing, which is seen by gradual elastic hardening and increasing damping of the RUS signal. Heating from 220 K to room temperature leads to elastic anomalies due to the initial transformation, which is now shifted to high temperatures. The transition is smeared over a wider temperature interval and shows strong elastic damping. The shear modulus of the cubic phase is recovered at 280 K. The phase transformation leads to avalanches, which were recorded by AE and by time-resolved calorimetry. The cooling transition shows very extended avalanche signals in calorimetry with power-law distributions. Cooling and heating runs show AE signals over a large temperature interval above 260 K. Splitting the transformation into two martensite phases leads to power-law exponents ε ∼ 2 (β ↔ 18R) and ε ∼ 1.5 (β ↔ 2H ) while the phase mixture shows an effective AE exponent of 1.7.

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