Amplification of obliquity forcing through mean-annual and seasonal atmospheric feedbacks

International audiencePleistocene benthic ?18O records exhibit strong spectral power at ~41 kyr, indicating that global ice volume has been modulated by Earth's axial tilt. This feature, and weak spectral power in the precessional band, has been attributed to the influence of obliquity on mean-annual and seasonal insolation gradients at high latitudes. In this study, we use a coupled ocean-atmosphere general circulation model to quantify changes in continental snowfall associated with mean-annual and seasonal insolation forcing due to a change in obliquity. Our model results indicate that insolation changes associated with a decrease in obliquity amplify continental snowfall in two ways: (1) An increase in high-latitude winter insolation is enhanced through a low-cloud feedback, resulting in colder air temperatures and increased snow precipitation. (2) An increase in the summer insolation gradient enhances summer eddy activity, increasing vapor transport to high-latitude regions. In our experiments, a decrease in obliquity leads to an annual snowfall increase of 25.0 cm; just over one-half of this response (14.1 cm) is attributed to seasonal changes in insolation. Our results indicate that the role of insolation gradients is important in amplifying the relatively weak insolation forcing due to a change in obliquity. Nonetheless, the total snowfall response to obliquity is similar to that due to a shift in Earth's precession, suggesting that obliquity forcing alone can not account for the spectral characteristics of the ice-volume record

Palaeoclimate - A balmy Arctic

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/62910/1/432814a.pd

TCR remote monitoring for the LHC technical infrastructure

The remote monitoring of the LHC technical infrastructure will mainly be done in CERN’s Technical Control Room (TCR). The technical infrastrucure consists of specialised equipment from different groups and divisions, mainly cooling and ventilation and electrical equipment. The responsibility for the definition, operation and maintenance of the equipment is covered by the relevant equipment group. However the monitoring and alerting for action in case of equipment failure is initiated by the TCR and is based on alarms that are sent by the equipment. This implies the correct integration of the equipment and the establishment of rules to follow during the commissioning and start-up of the equipment in order to ensure proper operation. This paper shows the integration possibilities and the different tasks and steps to follow by the different parties for smooth equipment integration and avoiding organizational problems

Unitary representations of nilpotent super Lie groups

We show that irreducible unitary representations of nilpotent super Lie groups can be obtained by induction from a distinguished class of sub super Lie groups. These sub super Lie groups are natural analogues of polarizing subgroups that appear in classical Kirillov theory. We obtain a concrete geometric parametrization of irreducible unitary representations by nonnegative definite coadjoint orbits. As an application, we prove an analytic generalization of the Stone-von Neumann theorem for Heisenberg-Clifford super Lie groups

A quantum beam splitter for atoms

An interferometric method is proposed to controllably split an atomic condensate in two spatial components with strongly reduced population fluctuations. All steps in our proposal are in current use in cold atom laboratories, and we show with a theoretical calculation that our proposal is very robust against imperfections of the interferometer.Comment: 6 pages, 3 figures, revtex

Manipulating the torsion of molecules by strong laser pulses

A proof-of-principle experiment is reported, where torsional motion of a molecule, consisting of a pair of phenyl rings, is induced by strong laser pulses. A nanosecond laser pulse spatially aligns the carbon-carbon bond axis, connecting the two phenyl rings, allowing a perpendicularly polarized, intense femtosecond pulse to initiate torsional motion accompanied by an overall rotation about the fixed axis. The induced motion is monitored by femtosecond time-resolved Coulomb explosion imaging. Our theoretical analysis accounts for and generalizes the experimental findings.Comment: 4 pages, 4 figures, submitted to PRL; Major revision of the presentation of the material; Correction of ion labels in Fig. 2(a

Regulation of peptide import through phosphorylation of Ubr1, the ubiquitin ligase of the N-end rule pathway

Substrates of the N-end rule pathway include proteins with destabilizing N-terminal residues. These residues are recognized by E3 ubiquitin ligases called N-recognins. Ubr1 is the N-recognin of the yeast Saccharomyces cerevisiae. Extracellular amino acids or short peptides up-regulate the peptide transporter gene PTR2, thereby increasing the capacity of a cell to import peptides. Cup9 is a transcriptional repressor that down-regulates PTR2. The induction of PTR2 by peptides or amino acids involves accelerated degradation of Cup9 by the N-end rule pathway. We report here that the Ubr1 N-recognin, which conditionally targets Cup9 for degradation, is phosphorylated in vivo at multiple sites, including Ser300 and Tyr277. We also show that the type-I casein kinases Yck1 and Yck2 phosphorylate Ubr1 on Ser300, and thereby make possible (“prime”) the subsequent (presumably sequential) phosphorylations of Ubr1 on Ser296, Ser292, Thr288, and Tyr277 by Mck1, a kinase of the glycogen synthase kinase 3 (Gsk3) family. Phosphorylation of Ubr1 on Tyr277 by Mck1 is a previously undescribed example of a cascade-based tyrosine phosphorylation by a Gsk3-type kinase outside of autophosphorylation. We show that the Yck1/Yck2-mediated phosphorylation of Ubr1 on Ser300 plays a major role in the control of peptide import by the N-end rule pathway. In contrast to phosphorylation on Ser300, the subsequent (primed) phosphorylations, including the one on Tyr277, have at most minor effects on the known properties of Ubr1, including regulation of peptide import. Thus, a biological role of the rest of Ubr1 phosphorylation cascade remains to be identified