Thermorheology of living cells: impact of temperature variations on cell mechanics

Upon temperature changes, we observe a systematic shift of creep compliance curves J (t) for single living breast epithelial cells. We use a dual-beam laser trap (optical stretcher) to induce temperature jumps within milliseconds, while simultaneously measuring the mechanical response of whole cells to optical force. The cellular mechanical response was found to differ between sudden temperature changes compared to slow, long-term changes implying adaptation of cytoskeletal structure. Interpreting optically induced cell deformation as a thermorheological experiment allows us to consistently explain data on the basis of time–temperature superposition, well known from classical polymer physics. Measured time shift factors give access to the activation energy of the viscous flow of MCF-10A breast cells, which was determined to be 80 kJ mol−1. The presented measurements highlight the fundamental role that temperature plays for the deformability of cellular matter. We propose thermorheology as a powerful concept to assess the inherent material properties of living cells and to investigate cell regulatory responses upon environmental changes

Working poor: trotz Einkommen kein Auskommen ; Trend- und Strukturanalysen für Österreich im europäischen Kontext

"Der vorliegende Beitrag beschäftigt sich mit dem Thema working poor - Armut trotz Erwerbstätigkeit. Dazu werden in einem ersten Schritt aktuelle Entwicklungen für Österreich im Kontext europäischer Trends betrachtet. Dabei wird der Frage nachgegangen, welchen Stellenwert Unterschiede in den wohlfahrtsstaatlichen Rahmenbedingungen für die Ausprägung von working poor haben. In einem zweiten Schritt werden detaillierte empirische Analysen der Lebenssituation von in Armut lebenden Erwerbstätigen in Österreich vorgestellt. Die entsprechenden Berechnungen beruhen auf den EU-SILC-Daten für die Jahre 2004 bis 2008. Unsere Befunde zeigen, dass Frauen, AlleinerzieherInnen und kinderreiche Familien, aber auch Beschäftigte in der Landwirtschaft und in personenbezogenen Dienstleistungen von Armut trotz Erwerbstätigkeit besonders betroffen sind. Darüber hinaus zeigt unsere Studie, dass die Armutsrisiken innerhalb des Untersuchungszeitraums für diese Personengruppen deutlich zunehmen." (Autorenreferat)"The article analyses the situation of the working poor in Austria in context of the European social welfare states. Firstly, it is being investigated to which extent the social welfare regulations are responsible for differences in the quantity of the poor in the labor force. Secondly, the article presents an overview of the working poor in Austria, based on EU-SILC data for the years 2004-2008. Our results show that women, single parents and families with three or more children as well as employees in the agrarian and service sectors are confronted with higher risks to fall into the category of working poor. Moreover, our study reveals that these risks increased considerably over the examined time period." (author's abstract

Koalas use a novel vocal organ to produce unusually low-pitched mating calls

SummaryDuring the breeding season, male koalas produce ‘bellow’ vocalisations that are characterised by a continuous series of inhalation and exhalation sections, and an extremely low fundamental frequency (the main acoustic correlate of perceived pitch) [1]. Remarkably, the fundamental frequency (F0) of bellow inhalation sections averages 27.1 Hz (range: 9.8–61.5 Hz [1]), which is 20 times lower than would be expected for an animal weighing 8 kg [2] and more typical of an animal the size of an elephant (Supplemental figure S1A). Here, we demonstrate that koalas use a novel vocal organ to produce their unusually low-pitched mating calls

Thermal instability of cell nuclei

DNA is known to be a mechanically and thermally stable structure. In its double stranded form it is densely packed within the cell nucleus and is thermo-resistant up to 70 °C. In contrast, we found a sudden loss of cell nuclei integrity at relatively moderate temperatures ranging from 45 to 55 °C. In our study, suspended cells held in an optical double beam trap were heated under controlled conditions while monitoring the nuclear shape. At specific critical temperatures, an irreversible sudden shape transition of the nuclei was observed. These temperature induced transitions differ in abundance and intensity for various normal and cancerous epithelial breast cells, which clearly characterizes different cell types. Our results show that temperatures slightly higher than physiological conditions are able to induce instabilities of nuclear structures, eventually leading to cell death. This is a surprising finding since recent thermorheological cell studies have shown that cells have a lower viscosity and are thus more deformable upon temperature increase. Since the nucleus is tightly coupled to the outer cell shape via the cytoskeleton, the force propagation of nuclear reshaping to the cell membrane was investigated in combination with the application of cytoskeletal drugs

Pola Interaksi Guru Dan Siswa Tunanetra Dalam Pembelajaran Matematika Di Smplb a Ykab Surakarta (Studi Kasus Pada Siswa Kelas IX Smplb a Ykab Surakarta Semester Ganjil Tahun Pelajaran 2012/2013)

With visual impairment in mathematics teaching learning on a conceptual and procedural knowledge in class IX SMPLB A YKAB Surakarta. This research was a qualitative case study, investigating deeply about the interaction of the teacher and the students in order that the interaction pattern can be described in the mathematics teaching learning. The subjects of this research were a mathematics teacher and all students of class IX SMPLB A YKAB Surakarta. The data in this study were in the form of teacher and students interactions obtained from transcriptions of the teaching learning recordings during twice observations. The transcription results were the teacher and the students\u27 conversations that are further reduced in order to obtain certain conversation related to the teaching learning of conceptual and procedural knowledge. Furthermore, labeling speech act and speech interaction was conducted in the conversation of conceptual and procedural teaching learning. Based on the labeling, speech interaction were categorized into three, namely: 1) speech interaction that was begun with speech act of giving information (BIn), 2) speech interaction that was begun with speech act of performing information (UIn), and 3) speech interaction that was begun with speech act of stimulating information (TIn). Each of the categories was analyzed so that the subjects that are interacting can be examined. The result of the analysis became the data of teacher and students interaction. The technique used to validate the data was time triangulation done by matching the data of the teacher and the students\u27 interaction taken from the first observation and the data of the teacher and the students\u27 interaction taken from the second observation.The results of the matching process were used to describe the interaction pattern. The findings of this research were: 1) the interaction pattern of the teacher and the students with visual impairment in mathematics teaching learning on a conceptual knowledge in class IX SMPLB A YKAB Surakarta was a two-way interaction pattern with inter-students interactions.Two-way interactionwith studentteachersis dominatedby theactivities ofthe teacherto giving information (BIN) and the performing information (TIN) to the students. While theinteractionbetween studentsis dominatedbythe activities ofthe studentsto performanceinformation(UIN). 2) the interaction pattern of the teacher and the students with visual impairment in mathematics teaching learning on a procedural knowledge in class IX SMPLB A YKAB Surakarta was a multiple-way interaction pattern (optimal result). Teacherinteractionwith studentsis dominatedby theactivities ofthe teacherto giving information(BIN), andstimulating information(TIN) to the students. Whilestudent interactionwith studentsspreadis dominated bythe performanceof information(UIN)

The impact of sulfur hexafluoride (SF₆) sinks on age of air climatologies and trends

Mean age of air (AoA) is a common diagnostic for the strength of the stratospheric overturning circulation in both climate models and observations. AoA climatologies and AoA trends over the recent decades of model simulations and proxies derived from observations of long-lived tracers do not agree. Satellite observations show much older air than climate models, and while most models compute a clear decrease in AoA over the last decades, a 30-year time series from measurements shows a statistically nonsignificant positive trend in the Northern Hemisphere extratropical middle stratosphere. Measurement-based AoA derivations are often founded on observations of the trace gas sulfur hexafluoride (SF$_{6}$), a fairly long-lived gas with a near-linear increase in emissions during recent decades. However, SF$_{6}$ has chemical sinks in the mesosphere that are not considered in most model studies. In this study, we explicitly compute the chemical SF$_{6}$ sinks based on chemical processes in the global chemistry climate model EMAC (ECHAM/MESSy Atmospheric Chemistry). We show that good agreement between stratospheric AoA in EMAC and MIPAS (Michelson Interferometer for Passive Atmospheric Sounding) is reached through the inclusion of chemical SF$_{6}$ sinks, as these sinks lead to a strong increase in the stratospheric AoA and, therefore, to a better agreement with MIPAS satellite observations. Remaining larger differences at high latitudes are addressed, and possible reasons for these differences are discussed. Subsequently, we demonstrate that the AoA trends are also strongly influenced by the chemical SF6 sinks. Under consideration of the SF$_{6}$ sinks, the AoA trends over the recent decades reverse sign from negative to positive. We conduct sensitivity simulations which reveal that this sign reversal does not result from trends in the stratospheric circulation strength nor from changes in the strength of the SF$_{6}$ sinks. We illustrate that even a constant SF$_{6}$ destruction rate causes a positive trend in the derived AoA, as the amount of depleted SF$_{6}$ scales with increasing SF$_{6}$ abundance itself. In our simulations, this effect overcompensates for the impact of the accelerating stratospheric circulation which naturally decreases AoA. Although various sources of uncertainties cannot be quantified in detail in this study, our results suggest that the inclusion of SF$_{6}$ depletion in models has the potential to reconcile the AoA trends of models and observations. We conclude the study with a first approach towards a correction to account for SF$_{6}$ loss and deduce that a linear correction might be applicable to values of AoA of up to 4 years

Red fluorescence of the triplefin Tripterygion delaisi is increasingly visible against background light with increasing depth

The light environment in water bodies changes with depth due to the absorption of short and long wavelengths. Below 10 m depth, red wavelengths are almost completely absent rendering any red-reflecting animal dark and achromatic. However, fluorescence may produce red coloration even when red light is not available for reflection. A large number of marine taxa including over 270 fish species are known to produce red fluorescence, yet it is unclear under which natural light environment fluorescence contributes perceptively to their colours. To address this question we: (i) characterized the visual system of Tripterygion delaisi, which possesses fluorescent irides, (ii) separated the colour of the irides into its reflectance and fluorescence components and (iii) combined these data with field measurements of the ambient light environment to calculate depth-dependent perceptual chromatic and achromatic contrasts using visual modelling. We found that triplefins have cones with at least three different spectral sensitivities, including differences between the two members of the double cones, giving them the potential for trichromatic colour vision. We also show that fluorescence contributes increasingly to the radiance of the irides with increasing depth. Our results support the potential functionality of red fluorescence, including communicative roles such as species and sex identity, and non-communicative roles such as camouflage