Evidence of a one-dimensional thermodynamic phase diagram for simple glass-formers.

Glass formers show motional processes over an extremely broad range of timescales, covering more than ten orders of magnitude, meaning that a full understanding of the glass transition needs to comprise this tremendous range in timescales. Here we report simultaneous dielectric and neutron spectroscopy investigations of three glass-forming liquids, probing in a single experiment the full range of dynamics. For two van der Waals liquids, we locate in the pressure-temperature phase diagram lines of identical dynamics of the molecules on both second and picosecond timescales. This confirms predictions of the isomorph theory and effectively reduces the phase diagram from two to one dimension. The implication is that dynamics on widely different timescales are governed by the same underlying mechanisms.

Slow rheological mode in glycerol and glycerol-water mixtures.

Glycerol-water mixtures were studied at molar concentrations ranging from xgly = 1 (neat glycerol) to xgly = 0.3 using shear mechanical spectroscopy. We observed a low frequency mode in neat glycerol, similar to what has been reported for monohydroxy alcohols. This mode has no dielectric counterpart and disappears with increased water concentration. We propose that the hydrogen-bonded network formed between glycerol molecules is responsible for the observed slow mode and that water acts as a plasticizer for the overall dynamics and as a lubricant softening the hydrogen-bonding contribution to the macroscopic viscosity of this binary system.

Communication: Slow supramolecular mode in amine and thiol derivatives of 2-ethyl-1-hexanol revealed by combined dielectric and shear-mechanical studies.

In this paper, we present results of dielectric and shear-mechanical studies for amine (2-ethyl-1-hexylamine) and thiol (2-ethyl-1-hexanethiol) derivatives of the monohydroxy alcohol, 2-ethyl-1-hexanol. The amine and thiol can form hydrogen bonds weaker in strength than those of the alcohol. The combination of dielectric and shear-mechanical data enables us to reveal the presence of a relaxation mode slower than the α-relaxation. This mode is analogous to the Debye mode seen in monohydroxy alcohols and demonstrates that supramolecular structures are present for systems with lower hydrogen bonding strength. We report some key features accompanying the decrease in the strength of the hydrogen bonding interactions on the relaxation dynamics close to the glass-transition. This includes changes (i) in the amplitude of the Debye and α-relaxations and (ii) the separation between primary and secondary modes.

A systematic study of the isothermal crystallization of the mono-alcohol n-butanol monitored by dielectric spectroscopy.

Isothermal crystallization of the mono-hydroxyl alcohol n-butanol was studied with dielectric spectroscopy in real time. The crystallization was carried out using two different sample cells at 15 temperatures between 120 K and 134 K. Crystallization is characterized by a decrease of the dielectric intensity. In addition, a shift in relaxation times to shorter times was observed during the crystallization process for all studied temperatures. The two different sample environments induced quite different crystallization behaviors, consistent and reproducible over all studied temperatures. An explanation for the difference was proposed on the background of an Avrami analysis and a Maxwell-Wagner analysis. Both types of analysis suggest that the morphology of the crystal growth changes from a higher dimension to a lower at a point during the crystallization. More generally, we conclude that a microscopic interpretation of crystallization measurements requires multiple probes, sample cells, and protocols.

Influence of pressure on the boson peak: stronger than elastic medium transformation.

We study the changes in the low-frequency vibrational dynamics of poly(isobutylene) under pressure up to 1.4 GPa, corresponding to a density change of 20%. Combining inelastic neutron, x-ray, and Brillouin light scattering, we analyze the variations in the boson peak, transverse and longitudinal sound velocities, and the Debye level under pressure. We find that the boson peak variation under pressure cannot be explained by the elastic continuum transformation only. Surprisingly, the shape of the boson peak remains unchanged even at such high compression.

The use of the Balanced ScoreCard (BSC) in the model for investment and evaluation of medical information systems.

This paper describes the use of the Balanced ScoreCard (BSC) in the MIEMIS meso-model (Model for Investment and Evaluation of Medical Information Systems). The scope of the MIEMIS model is to integrate the evaluation process into the whole lifecycle of an information system using both a prospective and a retrospective approach. We conclude, that the MIEMIS-model has benefited from implementing the BSC into the model due to the fact, that the BSC can support the project management work. This approach helps ensuring, that the new information systems are fulfilled according to the plan and with a balance between the four perspectives (financial, customer/user, internal, and innovation/learning perspective) to avoid that the financial aspect is the driving force in developing and implementing a new information system, for example.

Expression of the homeobox gene GBX2 during chicken development.

We have examined the expression pattern of the GBX2 gene during chicken embryogenesis. First transcripts are found in the epiblast of a HH st. 3+ embryo. With the onset of neurogenesis, transcripts mark the posterior neuroectoderm. Later on, expression is detectable in the isthmic region, the hindbrain and the neural tube. We show that GBX2 transcripts, as well as the protein, mark the presumptive hindbrain region. After establishment of the brain vesicles GBX2 transcripts were also detected in distinct domains of the diencephalon. In addition to neural sites of expression, GBX2 was found in several domains including the otic vesicle, the somitic mesoderm, the lateral foregut endoderm, the ventral limb bud ectoderm and in the feather buds.

The homeobox gene GBX2, a target of the myb oncogene, mediates autocrine growth and monocyte differentiation.

The homeobox gene GBX2 was identified as a target gene of the v-Myb oncoprotein encoded by the avian myeloblastosis virus (AMV). GBX2 activation by c-Myb requires signal transduction emanating from the cell surface while the leukemogenic AMV v-Myb constitutively induces the GBX2 gene. Mutations in the DNA binding domain of AMV-Myb render it independent of signaling events and concomitantly abrogate the collaboration between Myb and CCAAT Enhancer Binding Proteins (C/EBP), which are involved in granulocyte differentiation. Ectopic expression of GBX2 in growth factor-dependent myeloblasts induces monocytic features and independence from exogenous cytokines, reflecting distinct features of AMV-transformed cells. Our results suggest that Myb or factors it interacts with contribute to hematopoietic lineage choice and differentiation in a signal transduction-dependent fashion.

Differential activation of the clustered homeobox genes CNOT2 and CNOT1 during notogenesis in the chick.

CNOT2, a newly identified homeobox gene, is physically linked to the CNOT1 gene in the chicken genome. The two chicken genes represent two different subgroups of the Not gene family, the first including CNOT1 and the Xenopus genes XNot1 and XNot2, and the second CNOT2 and the zebrafish floating head gene. The overall expression pattern of CNOT2 in Hensen's node, notochord, neural plate, tailbud, and epiphysis resembled the CNOT1 pattern. However, several significant differences occurred: CNOT2 expression was much stronger and more widespread in the pregastrulation embryo, it showed an additional, transient domain on the anterior intestinal portal, and lacked expression on the early anterior neural folds and the anterodistal limb bud. We studied CNOT expression by transplanting parts of the primitive streak into growing embryos or by explanting them into tissue culture. CNOT gene expression from young nodes was maintained in vivo, but required in vitro the addition of retinoic acid. The generation of differentiated notochord structures could only be obtained, if either older node grafts were used in vitro or young node grafts were transplanted close to the primary axis in vivo. We conclude that CNOT expression in the anterior streak is not enough for notochord differentiation, but further influences are necessary. A Not-related gene has previously been isolated from Drosophila melanogaster and its expression was detected in the posterior brain and the neuroblasts (Dessain and McGinnis, 1993. Adv. Dev. Biochem. 2, 1-55). The correspondence between Not gene-expressing cells in the nervous system of Drosophila and the early neuroectoderm in the chick and its implication for a phylogenetic relationship between neuroectoderm and the notochord is discussed.