Determination of the direct band-gap energy of InAlAs matched to InP by photoluminescence excitation spectroscopy

A series of InxAl12xAs samples (0.51,x,0.55) coherently grown on InP was studied in order to measure the band-gap energy of the lattice matched composition. As the substrate is opaque to the relevant photon energies, a method is developed to calculate the optical absorption coefficient from the photoluminescence excitation spectra. The effect of strain on the band-gap energy has been taken into account. For x50.532, at 14 K we have obtained Eg05154966 meV. © 1997 American Institute of Physics.

Mobility of inorganic and organic phosphorus forms under different levels of phosphate and poultry litter fertilization in soils

The eutrophication of aquifers is strongly linked to the mobility of P in soils. Although P mobility was considered irrelevant in a more distant past, more recent studies have shown that P, both in organic (Po) and inorganic forms (Pi), can be lost by leaching and eluviation through the soil profile, particularly in less weathered and/or sandier soils with low P adsorption capacity. The purpose of this study was to determine losses of P forms by leaching and eluviation from soil columns. Each column consisted of five PVC rings (diameter 5 cm, height 10 cm), filled with two soil types: a clayey Red-Yellow Latosol and a sandy loam Red-Yellow Latosol, which were exposed to water percolation. The soils were previously treated with four P rates (as KH2PO4 ) to reach 0, 12.5, 25.0 and 50 % of the maximum P adsorption capacity (MPAC). The P source was homogenized with the whole soil volume and incubated for 60 days. After this period the soils were placed in the columns; the soil of the top ring was mixed with five poultry litter rates of 0, 20, 40, 80, and 160 t ha-1 (dry weight basis). Treatments consisted of a 4 x 5 x 2 factorial scheme corresponding to four MPAC levels, five poultry litter rates, two soils, with three replications, arranged in a completely randomized block design. Deionized water was percolated through the columns 10 times in 35 days to simulate about 1,200 mm rainfall. In the leachate of each column the inorganic P (reactive P, Pi) and organic P forms (unreactive P, Po) were determined. At the end of the experiment, the columns were disassembled and P was extracted with the extractants Mehlich-1 (HCl 0.05 mol L-1 and H2SO4 0.0125 mol L-1) and Olsen (NaHCO3 0.5 mol L-1; pH 8.5) from the soil of each ring. The Pi and Po fractions were measured by the Olsen extractant. It was found that under higher poultry litter rates the losses of unreactive P (Po) were 6.4 times higher than of reactive P (Pi). Both the previous P fertilization and increasing poultry litter rates caused a vertical movement of P down the soil columns, as verified by P concentrations extracted by Mehlich-1 and NaHCO3 (Olsen). The environmental critical level (ECL), i.e., the P soil concentration above which P leaching increases exponentially, was 100 and 150 mg dm-3 by Mehlich-1 and 40 and 60 mg dm-3 by Olsen, for the sandy loam and clay soils, respectively. In highly weathered soils, where residual P is accumulated by successive crops, P leaching through the profile can be significant, particularly when poultry litter is applied as fertilizer.

Post-transcriptional down-regulation of expression of transcription factor NF1 by Ha-ras oncogene.

NF1 is a family of polypeptides that binds to discrete DNA motifs and plays varying roles in the regulation of gene expression. These polypeptides are also thought to mediate the expression of differentiation-specific markers such as adipocyte and mammary cell type-specific genes. The expression of a number of cellular differentiation-specific markers is down-regulated during neoplastic transformation. We therefore investigated whether oncogenic transformation interferes with the action of NF1. Stable transfection of activated Ha-ras into a number of murine cells correlated with a down-regulation of the expression of the NF1 genes NF1/CTF and NF1/X. The down-regulation was not at the transcriptional level but at the level of stability of the NF1 mRNAs. The level of the DNA binding activity of the NF1 proteins was also reduced in Ha-v-ras-transformed cells, and the expression of a gene that depends on this family of transcription factors was specifically repressed. These results demonstrate that an activated Ha-ras-induced pathway destabilizes the half-life of mRNAs encoding specific members in the NF1 family of transcription factors, which leads to a decrease in NF1-dependent gene expression.

Far-infrared spectroscopy of nanoscopic InAs rings

We have employed time-dependent local-spin-density theory to analyze the far-infrared transmission spectrum of InAs self-assembled nanoscopic rings recently reported [A. Lorke et al., Phys. Rev. Lett. (to be published)]. The overall agreement between theory and experiment is fairly good, which on the one hand confirms that the experimental peaks indeed reflect the ringlike structure of the sample, and on the other hand, asseses the suitability of the theoretical method to describe such nanostructures. The addition energies of one- and two-electron rings are also reported and compared with the corresponding capacitance spectra

Multipole modes and spin features in the Raman spectrum of nanoscopic quantum rings

We present a systematic study of ground state and spectroscopic properties of many-electron nanoscopic quantum rings. Addition energies at zero magnetic field (B) and electrochemical potentials as a function of B are given for a ring hosting up to 24 electrons. We find discontinuities in the excitation energies of multipole spin and charge density modes, and a coupling between the charge and spin density responses that allow to identify the formation of ferromagnetic ground states in narrow magnetic field regions. These effects can be observed in Raman experiments, and are related to the fractional Aharonov-Bohm oscillations of the energy and of the persistent current in the ring

A nucleosome-dependent static loop potentiates estrogen-regulated transcription from the Xenopus vitellogenin B1 promoter in vitro.

We describe the transcriptional potentiation in estrogen responsive transcription extracts of the Xenopus vitellogenin B1 gene promoter through the formation of a positioned nucleosome. Nuclease digestion and hydroxyl radical cleavage indicate that strong, DNA sequence-directed positioning of a nucleosome occurs between -300 and -140 relative to the start site of transcription. Deletion of this DNA sequence abolishes the potentiation of transcription due to nucleosome assembly. The wrapping of DNA around the histone core of the nucleosome positioned between -300 and -140 creates a static loop in which distal estrogen receptor binding sites are brought close to proximal promoter elements. This might facilitate interactions between the trans-acting factors themselves and/or RNA polymerase. Such a nucleosome provides an example of how chromatin structure might have a positive effect on the transcription process.

Water retention in a peatland with organic matter in different decomposition stages

Peatlands are ecosystems formed by successive pedogenetic processes, resulting in progressive accumulation of plant remains in the soil column under conditions that inhibit the activity of most microbial decomposers. In Diamantina, state of Minas Gerais, Brazil, a peatland is located at 1366 m asl, in a region with a quartz-rich lithology and characteristic wet grassland vegetation. For this study, the peat area was divided in 12 transects, from which a total of 90 soil samples were collected at a distance of 20 m from each other. The properties rubbed fiber content (RF), bulk density (Bd), mineral material (MM), organic matter (OM), moisture (Moi) and maximum water holding capacity (MWHC) were analyzed in all samples. From three selected profiles of this whole area, samples were collected every 27 cm from the soil surface down to a depth of 216 cm. In these samples, moisture was additionally determined at a pressure of 10 kPa (Moi10) or 1500 kPa (Moi1500), using Richards' extractor and soil organic matter was fractionated by standard procedures. The OM decomposition stage of this peat was found to increase with soil depth. Moi and MWHC were highest in layers with less advanced stages of OM decomposition. The humin levels were highest in layers in earlier stages of OM decomposition and with higher levels of water retention at MWHC and Moi10. Humic acid contents were higher in layers at an intermediate stage of decomposition of organic matter and with lowest levels of water retention at MWHC, Moi10 and Moi1500.

Matching at one loop for the four-quark operators in NRQCD

The matching coefficients for the four-quark operators in NRQCD (NRQED) are calculated at one loop using dimensional regularization for ultraviolet and infrared divergences. The matching for the electromagnetic current follows easily from our results. Both the unequal and equal mass cases are considered. The role played by the Coulomb infrared singularities is explained in detail.

Off-pump transapical mitral valve-in-ring implantation.

OBJECTIVES: The study aimed to evaluate the feasibility of off-pump transapical mitral valve-in-ring implantation and to test the performance of a custom-made self-expandable stent valve, in comparison with the standard SAPIEN valve. METHODS: Acute experiments were performed in five pigs. Animals (mean weight 58.4 ± 7.3 kg) underwent mitral valve annuloplasties under cardiopulmonary bypass using 26-mm rings (SJM?). Then, a 30-mm custom-made self-expandable stent valve or a 23-mm balloon-expandable transcatheter heart valve (Edwards SAPIEN XT?) was deployed within the annuloplasty rings through a transatrial access and under direct vision. Subsequently, the stent valves were inserted transapically under fluoroscopic guidance and off pump. RESULTS: The procedural success of transatrial and transapical mitral valve-in-ring procedures was 100% (10 of 10). Mean transatrial and transapical procedure time was 2.0 ± 1.1 and 22.0 ± 5.7 min, respectively. Haemodynamic status during transapical implantation remained stable, and differences in data collected before and after the stent-valve deployment were not statistically significant. Mean mitral annulus diameter and mean mitral orifice area in the group of self-expandable stent valves were 2.60 ± 0.02 cm and 4.16 ± 0.48 cm(2), respectively, whereas in the SAPIEN group they were 1.95 ± 0.18 cm and 2.26 ± 0.20 cm(2), respectively. Trace or mild regurgitation was detected only in the self-expandable stent-valve group. Mean gradients were 4.1 ± 4.5 mmHg across the self-expandable stent valves and 1.0 ± 0 mmHg across the SAPIEN valves. Postmortem examination confirmed adequate positioning of the self-expandable valves and the SAPIEN valves within the annuloplasty ring. CONCLUSIONS: Off-pump transapical mitral valve-in-ring implantation is safe and feasible. Transapical access may represent the ideal option for valve-in-ring procedures in cases of recurrent mitral regurgitation after mitral valve repair, in high-risk patients. Owing to the supra-annular profile of the valve components, our custom-made nitinol stent valve provides nearer to normal functional area than the SAPIEN valve.

Komik, Ernst und Mise en page. Zum Problem der Farblinien in Heinrich Wittenwilers "Der Ring"

Der Aufsatz nähert sich dem Interpretationsproblem des ,Ring', eines seit Forschungsbeginn ausserordentlich konträr diskutierten Textes, aus wissenschaftsanalytischer Perspektive. Er führt die Zersplitterung und die Extremisierung der Deutungsansätze, die die breite Forschung zu Wittenwilers Werk kennzeichnet, auf einen vergleichsweise simplen Befund zurück: die ungeklärte Frage nach dem Verhältnis von Komik und Didaktik und der Ernsthaftigkeit des lehrhaften Angebots im ,Ring'. Die so auf grundlegendster Ebene offen gebliebene Erfassung des Textes führt in einen interpretatorischen Leerraum, in dem die widersprüchlichsten, oft wissenschaftsideologisch begründeten Positionen Platz finden. Ihre Analyse zeigt, dass sie sich in wiederkehrende Gruppierungen ordnen. Als Schlüsselglied sowohl der Befunddaten als auch der konträren Vernetzungen von Befund und Deutung wird die wechselnd rote und grüne Initialenlinie der Münchner Handschrift identifiziert. Als im Prolog eingeführte Markierung von Ernst auf der einen und Komik auf der anderen Seite ist sie nicht nur visueller Ausdruck des Deutungsproblems des ,Ring', sondern sie hat es wegen der scheinbaren Unstimmigkeit ihrer Zuweisungen auch wesentlich bedingt. Der Aufsatz zeigt ihren bisher übersehenen Aufschluss für das Verständnis des Werks. Nimmt man die Linie als graphisches Verfahren ernst, stellt sie sich als strukturelle Markierung zum Auffinden von Text im diskontinuierlichen Zugriff dar - nicht aber, wie man sie bisher ausnahmslos verstand, als semantische Kommentierung eines laufenden, kontinuierlich zu lesenden Textes. Die strukturierende Funktion des Farbwechsels ist auf zwei Ebenen nachzuweisen: Auf Makroebene trennen seine Zuweisungen vorwiegend narrative und vorwiegend wissensvermittelnde Grosspartien des ,Ring' durch eine jeweilige Grundfarbe. Auf Mikroebene wird diese Grundfarbe durch die jeweils andere Farbe durchbrochen, um formale Einschnitte wie etwa Sprecherwechsel, Ortswechsel, Handlungsneueinsätze, Beginn und Ende eines eingeschalteten Binnentextes oder einer Sentenz anzuzeigen. Dem Benutzer der autornahen Handschrift sollte so in einem ersten Schritt (makrostrukturell) ermöglicht werden, gezielt auf gewünschte Stellen des Textes zuzugreifen und ihn in einem zweiten Schritt (mikrostrukturell) schneller zu erfassen. Nicht in seiner Umsetzung, sehr wohl aber in seiner Funktion steht dieses ungewöhnliche Layout zeitgenössischen Techniken der Buchgliederung durchaus nahe. Auch im Profil der Zusammenstellung seiner Binnentexte rückt der ,Ring' damit in die Nähe der im Spätmittelalter beliebten Sammelhandschriften mit Ziel einer Wissenssumme, die hier narrativ verbundenen wird. Es scheint, als möchte der ,Ring' in einem ungewöhnlichen Experiment beides sein: Kompilation und Werkganzes, Wissenssammlung und Erzählwerk - Texte und Text. Als Ergebnis einer Neuuntersuchung des Münchner codex unicus des ,Ring' weist der Beitrag schliesslich darauf hin, dass auch zahlreiche Markierungszeichen am Spaltenrand formale und strukturelle Texteinschnitte anzeigen und somit die gleiche Funktion haben wie der Farbwechsel auf Mikroebene. Ein kausaler, produktionstechnischer Zusammenhang zwischen diesen Zeichen und der Verteilung des Farbwechsels ist nicht auszuschliessen, zumal beide Verfahren etwa im letzten Fünftel des Textes zunehmend zusammenfallen. Möglicherweise war nur die makrostrukturelle Funktion des Farbwechsel ursprünglich indendiert und mit der Erläuterung im Prolog bezeichnet, während seine mikrostrukturelle Funktion erst Resultat des Abschreibprozesses ist.

Quantifying intracellular protein binding thermodynamics during mechanotransduction based on FRET spectroscopy.

Mechanical force modulates myriad cellular functions including migration, alignment, proliferation, and gene transcription. Mechanotransduction, the transmission of mechanical forces and its translation into biochemical signals, may be mediated by force induced protein conformation changes, subsequently modulating protein signaling. For the paxillin and focal adhesion kinase interaction, we demonstrate that force-induced changes in protein complex conformation, dissociation constant, and binding Gibbs free energy can be quantified by lifetime-resolved fluorescence energy transfer microscopy combined with intensity imaging calibrated by fluorescence correlation spectroscopy. Comparison with in vitro data shows that this interaction is allosteric in vivo. Further, spatially resolved imaging and inhibitor assays show that this protein interaction and its mechano-sensitivity are equal in the cytosol and in the focal adhesions complexes indicating that the mechano-sensitivity of this interaction must be mediated by soluble factors but not based on protein tyrosine phosphorylation.

PPARbeta/delta regulates paneth cell differentiation via controlling the hedgehog signaling pathway.

BACKGROUND & AIMS: All 4 differentiated epithelial cell types found in the intestinal epithelium derive from the intestinal epithelial stem cells present in the crypt unit, in a process whose molecular clues are intensely scrutinized. Peroxisome proliferator-activated receptor beta (PPARbeta) is a nuclear hormone receptor activated by fatty acids and is highly expressed in the digestive tract. However, its function in intestinal epithelium homeostasis is understood poorly. METHODS: To assess the role of PPARbeta in the small intestinal epithelium, we combined various cellular and molecular approaches in wild-type and PPARbeta-mutant mice. RESULTS: We show that the expression of PPARbeta is particularly remarkable at the bottom of the crypt of the small intestine where Paneth cells reside. These cells, which have an important role in the innate immunity, are strikingly affected in PPARbeta-null mice. We then show that Indian hedgehog (Ihh) is a signal sent by mature Paneth cells to their precursors, negatively regulating their differentiation. Importantly, PPARbeta acts on Paneth cell homeostasis by down-regulating the expression of Ihh, an effect that can be mimicked by cyclopamine, a known inhibitor of the hedgehog signaling pathway. CONCLUSIONS: We unraveled the Ihh-dependent regulatory loop that controls mature Paneth cell homeostasis and its modulation by PPARbeta. PPARbeta currently is being assessed as a drug target for metabolic diseases; these results reveal some important clues with respect to the signals controlling epithelial cell fate in the small intestine.

Phosphorus transformation in poultry litter and litter-treated Oxisol of Brazil assessed by 31P-NMR and wet chemical fractionation

Large quantities of poultry litter are being produced in Brazil, which contain appreciable amounts of phosphorus (P) that could be of environmental concern. To assess the immediate environmental threat, five poultry litters composed of diverse bedding material were incubated for 43 days under greenhouse conditions. The litters consisted of: coffee bean husk (CH); wood chips (WC); rice husk (RH); ground corn cobs (CC) and ground napier grass (NG) (Pennisetum purpureum Schum.), in which the change in forms of soluble P was evaluated using 31P NMR spectroscopy. On average, 80.2 and 19.8 % of the total P in the extract, respectively, accounted for the inorganic and organic forms before incubation and 48 % of the organic P was mineralized to inorganic P in 43 days of incubation. Wide variation in the organic P mineralization rate (from 82 % -WC to 4 % - NG) was observed among litters. Inorganic orthophosphate (99.9 %) and pyrophosphate (0.1 %) were the only inorganic P forms, whereas the organic P forms orthophosphate monoesters (76.3 %) and diester (23.7 %) were detected. Diester P compounds were mineralized almost completely in all litters, except in the CH litter, within the incubation period. Pyrophosphates contributed with less than 0.5% and remained unaltered during the incubation period. Wood-chip litter had a higher organic P (40 %) content and a higher diester: monoester ratio; it was therefore mineralized rapidly, within the first 15 days, achieving steady state by the 29th day. Distinct mineralization patterns were observed in the litter when incubated with a clayey Oxisol. The substantial decrease observed in the organic P fraction (Po) of the litter types followed the order: CH (45 %) > CC (25 %) > RH (13 %) ≈ NG (12 %) > WC (5 %), whereas the Pi fraction increased. Incubation of RH litter in soil slowed down the mineralization of organic P.

SET translocation is associated with increase in caspase cleaved amyloid precursor protein in CA1 of Alzheimer and Down syndrome patients.

Caspase cleaved amyloid precursor protein (APPcc) and SET are increased and mislocalized in the neuronal cytoplasm in Alzheimer Disease (AD) brains. Translocated SET to the cytoplasm can induce tau hyperphosphorylation. To elucidate the putative relationships between mislocalized APPcc and SET, we studied their level and distribution in the hippocampus of 5 controls, 3 Down syndrome and 10 Alzheimer patients. In Down syndrome and Alzheimer patients, APPcc and SET levels were increased in CA1 and the frequency of both localizations in the neuronal cytoplasm was high in CA1, and low in CA4. As the increase of APPcc is already present at early stages of AD, we overexpressed APPcc in CA1 and the dentate gyrus neurons of adult mice with a lentiviral construct. APPcc overexpression in CA1 and not in the dentate gyrus induced endogenous SET translocation and tau hyperphosphorylation. These data suggest that increase in APPcc in CA1 neurons could be an early event leading to the translocation of SET and the progression of AD through tau hyperphosphorylation.