First evidence of an intimate symbiotic association between fungi and larvae in basal attine ants

The most conspicuous ants in all of tropical America are those that belong to the tribe Attini which cultivate fungus. The objective of the present study is to verify the alterations that occur in the cuticle of the worker larvae from Myrmicocrypta, Mycetarotes and Trachymyrmex with the purpose of trying to establish the degree of this association. Attine ants from the Atta genus were used as a control group. The analysis of histological sections showed results about the distribution of the cells and tissues on the epidermis of A. sexdens rubropilosa ant larvae and Mycetarotes parallelus, Trachymyrmex fuscus and Myrmicocrypta sp. A cuticle covering the ants was observed in the larvae of all the species, and this is formed by a simple cubic epithelium, whose cells possibly change its shape to prismatic, depending on their secretory activity. Just under this epithelium large adipose cells with reserve granules in their cytoplasm were found. The presence of a space filled by granulose and acellular material was also observed, indicating that the larvae were in a molt period. The presence of fungal hyphae is observed both on the external side of the basal attine larvae as well as emitting projections to the interior of the cuticle reaching the epithelium and the adipocyte cells. Data obtained in the present study demonstrated that the fungus deposited on the surface of immature ants from attine basal species maintain a close relationship with them, once the fungus hyphae have the ability to disorganize the cuticle lamellas, penetrating the interior of the insect cells through the emission of prolongations transporting the cuticle and epithelium barriers and making substances exchanges between larvae and fungus.     

Discovery of antagonists of PqsR, a key player in 2-alkyl-4-quinolone-dependent quorum sensing in Pseudomonas aeruginosa

The pqs quorum sensing communication system of Pseudomonas aeruginosa controls virulence factor production and is involved in biofilm formation, therefore playing an important role for pathogenicity. In order to attenuate P. aeruginosa pathogenicity, we followed a ligand-based drug design approach and synthesized a series of compounds targeting PqsR, the receptor of the pqs system. In vitro evaluation using a reporter gene assay in Escherichia coli led to the discovery of the first competitive PqsR antagonists, which are highly potent (K(d,app) of compound 20: 7 nM). These antagonists are able to reduce the production of the virulence factor pyocyanin in P. aeruginosa. Our finding offers insights into the ligand-receptor interaction of PqsR and provides a promising starting point for further drug design.     

Finite width in out-of-equilibrium propagators and kinetic theory

We derive solutions to the Schwinger–Dyson equations on the Closed-Time-Path for a scalar field in the limit where backreaction is neglected. In Wigner space, the two-point Wightman functions have the curious property that the equilibrium component has a finite width, while the out-of equilibrium component has zero width. This feature is confirmed in a numerical simulation for scalar field theory with quartic interactions. When substituting these solutions into the collision term, we observe that an expansion including terms of all orders in gradients leads to an effective finite-width. Besides, we observe no breakdown of perturbation theory, that is sometimes associated with pinch singularities. The effective width is identical with the width of the equilibrium component. Therefore, reconciliation between the zero-width behaviour and the usual notion in kinetic theory, that the out-of-equilibrium contributions have a finite width as well, is achieved. This result may also be viewed as a generalisation of the fluctuation–dissipation relation to out-of-equilibrium systems with negligible backreaction.     

Electron waiting times in mesoscopic conductors

Electron transport in mesoscopic conductors has traditionally involved investigations of the mean current and the fluctuations of the current. A complementary view on charge transport is provided by the distribution of waiting times between charge carriers, but a proper theoretical framework for coherent electronic systems has so far been lacking. Here we develop a quantum theory of electron waiting times in mesoscopic conductors expressed by a compact determinant formula. We illustrate our methodology by calculating the waiting time distribution for a quantum point contact and find a crossover from Wigner-Dyson statistics at full transmission to Poisson statistics close to pinch-off. Even when the low-frequency transport is noiseless, the electrons are not equally spaced in time due to their inherent wave nature. We discuss the implications for renewal theory in mesoscopic systems and point out several analogies with level spacing statistics and random matrix theory.     

High-efficiency 10 J diode pumped cryogenic gas cooled Yb:YAG multislab amplifier

We report on the first demonstration of a diode-pumped, gas cooled, cryogenic multislab Yb:YAG amplifier. The performance was characterized over a temperature range from 88 to 175 K. A maximum small-signal single-pass longitudinal gain of 11.0 was measured at 88 K. When amplifying nanosecond pulses, recorded output energies were 10.1 J at 1 Hz in a four-pass extraction geometry and 6.4 J at 10 Hz in a three-pass setup, corresponding to optical to optical conversion efficiencies of 21% and 16%, respectively. To our knowledge, this represents the highest pulse energy so far obtained from a cryo-cooled Yb-laser and the highest efficiency from a multijoule diode pumped solid-state laser system.     

A short proof of the Doob–Meyer theorem

Every submartingale S$S$ of class D$D$ has a unique Doob–Meyer decomposition S=M+A$S=M+A$, where M$M$ is a martingale and A$A$ is a predictable increasing process starting at 0.     

The elusive tetrasulfate anion [S4O13](2-)

Sulfates united: the unique tetrasulfate S(4)O(13)(2-) anion was observed in the structure of (NO(2))(2)[S(4)O(13)] that forms in the reaction of N(2)O(5) with SO(3). Theoretical investigations show that the anion is a stable member of the polysulfate series [S(n)O(3n+1)](2-), which was investigated up to n=11.     

Cyclic distiba- and dibismadiazenium cations

Think positive, keep the anions away: Hitherto unknown mono- and dications of the type [XE(μ-NTerE)](+) and [E(2) (μ-NTer)(2) ](2+) (E=Sb, Bi; X=Cl, I) were studied and fully characterized for the first time. Salts bearing these highly reactive cations can be obtained from terphenyl-substituted cyclo-dipnictadiazanes [XE(μ-NR)](2) by halide abstraction or triflate substitution.     

Access to Skipped Polyene Macrolides through Ring-Closing Metathesis: Total Synthesis of the RNA Polymerase Inhibitor Ripostatin B

Rip-Roaring! A convergent total synthesis of antibiotic ripostatin?B was developed. A key step in the synthesis is a metathesis reaction allowing for a ring closure to the labile doubly skipped triene macrolide.