Efficient cloning system for construction of gene silencing vectors in Aspergillus niger

An approach based on Gateway recombination technology to efficiently construct silencing vectors was developed for use in the biotechnologically important fungus Aspergillus niger. The transcription activator of xylanolytic and cellulolytic genes XlnR of A. niger was chosen as target for gene silencing. Silencing was based on the expression vector pXLNRir that was constructed and used in co-transformation. From all the strains isolated (N = 77), nine showed poor xylan-degrading activities in two semi-quantitative plate assays testing different activities for xylan degradation. Upon induction on D-xylose, transcript levels of xlnR were decreased in the xlnR-silenced strains, compared to a wild-type background. Under these conditions, the transcript levels of xyrA and xynB (two genes regulated by XlnR) were also decreased for these xlnR-silenced strains. These results indicate that the newly developed system for rapid generation of silencing vectors is an effective tool for A. niger, and this can be used to generate strains with a tailored spectrum of enzyme activities or product formation by silencing specific genes encoding, e.g., regulators such as Xln

Little String Theory from Double-Scaling Limits of Field Theories

We show that little string theory on S^5 can be obtained as double-scaling limits of the maximally supersymmetric Yang-Mills theories on RxS^2 and RxS^3/Z_k. By matching the gauge theory parameters with those in the gravity duals found by Lin and Maldacena, we determine the limits in the gauge theories that correspond to decoupling of NS5-brane degrees of freedom. We find that for the theory on RxS^2, the 't Hooft coupling must be scaled like ln^3(N), and on RxS^3/Z_k, like ln^2(N). Accordingly, taking these limits in these field theories gives Lagrangian definitions of little string theory on S^5.Comment: 16 pages, 5 figures. Minor change

Embedding of theories with SU(2|4) symmetry into the plane wave matrix model

We study theories with SU(2|4) symmetry, which include the plane wave matrix model, 2+1 SYM on RxS^2 and N=4 SYM on RxS^3/Z_k. All these theories possess many vacua. From Lin-Maldacena's method which gives the gravity dual of each vacuum, it is predicted that the theory around each vacuum of 2+1 SYM on RxS^2 and N=4 SYM on RxS^3/Z_k is embedded in the plane wave matrix model. We show this directly on the gauge theory side. We clearly reveal relationships among the spherical harmonics on S^3, the monopole harmonics and the harmonics on fuzzy spheres. We extend the compactification (the T-duality) in matrix models a la Taylor to that on spheres.Comment: 56 pages, 6 figures, v2:a footnote and references added, section 5.2 improved, typos corrected, v3:typos corrected, v4: some equations are corrected, eq.(G.2) is added, conclusion is unchange

Coarse-Graining the Lin-Maldacena Geometries

The Lin-Maldacena geometries are nonsingular gravity duals to degenerate vacuum states of a family of field theories with SU(2|4) supersymmetry. In this note, we show that at large N, where the number of vacuum states is large, there is a natural `macroscopic' description of typical states, giving rise to a set of coarse-grained geometries. For a given coarse-grained state, we can associate an entropy related to the number of underlying microstates. We find a simple formula for this entropy in terms of the data that specify the geometry. We see that this entropy function is zero for the original microstate geometries and maximized for a certain ``typical state'' geometry, which we argue is the gravity dual to the zero-temperature limit of the thermal state of the corresponding field theory. Finally, we note that the coarse-grained geometries are singular if and only if the entropy function is non-zero.Comment: 29 pages, LaTeX, 3 figures; v2 references adde

Ethyl-cellulose rumen-protected methionine enhances performance during the periparturient period and early lactation in Holstein dairy cows

The onset of lactation in dairy cows is characterized by severe negative energy and protein balance. Increasing Met availability during this time may improve milk production, hepatic lipid metabolism, and immune function. The aim of this study was to evaluate the effect of feeding ethyl-cellulose rumen-protected methionine (RPM; Mepron, Evonik Nutrition and Care GmbH, Hanau-Wolfgang, Germany) on the performance of dairy cows during prepartum and early-lactation periods. Sixty multiparous Holstein cows were used in a block design and assigned to either a control or an ethyl-cellulose RPM diet. Ethyl-cellulose RPM was supplied from -28 to 60 d relative to parturition at a rate of 0.09% and 0.10% of dry matter during the prepartum and postpartum periods, respectively. That rate ensured that the ratio of Lys to Met in metabolizable protein was close to 2.8:1. Cows fed ethyl-cellulose RPM had dry matter intakes (DMI) that were 1.2 kg/d greater during the prepartum period and consequently had overall greater cumulative DMI than cows in the control group. Compared with controls, during the fresh period (1-30 d in milk; DIM) feeding ethyl-cellulose RPM increased DMI by 1.7 kg/d, milk yield by 4.1 kg/d, fat yield by 0.17 kg/d, milk protein yield by 0.20 kg/d, 3.5% fat-corrected milk by 4.3 kg/d, and energy-corrected milk by 4.4 kg/d. Although ethyl-cellulose RPM supplementation increased milk protein content by 0.16 percentage units compared with the control during the fresh period, no differences were observed for milk fat, lactose, and milk urea nitrogen concentration. During the high-producing period (31-60 DIM), cows fed ethyl-cellulose RPM increased DMI and milk yield by 1.45 and 4.4 kg/d, respectively. Ethyl-cellulose RPM also increased fat yield by 0.19 kg/d, milk protein yield by 0.17 kg/d, 3.5% fat-corrected milk by 4.7 kg/d, and energy-corrected milk by 4.8 kg/d compared with controls. Ethyl-cellulose RPM supplementation reduced plasma fatty acids in the fresh period and decreased γ-glutamyl transferase, indicating better liver function. In conclusion, when lysine was adequate, feeding ethyl-cellulose RPM to achieve a ratio close to 2.8:1 in metabolizable protein improved dairy cow performance from parturition through 60 DIM. The greater milk production was, at least in part, driven by the greater voluntary DMI and better liver function

Generally Covariant Actions for Multiple D-branes

We develop a formalism that allows us to write actions for multiple D-branes with manifest general covariance. While the matrix coordinates of the D-branes have a complicated transformation law under coordinate transformations, we find that these may be promoted to (redundant) matrix fields on the transverse space with a simple covariant transformation law. Using these fields, we define a covariant distribution function (a matrix generalization of the delta function which describes the location of a single brane). The final actions take the form of an integral over the curved space of a scalar single-trace action built from the covariant matrix fields, tensors involving the metric, and the covariant distribution function. For diagonal matrices, the integral localizes to the positions of the individual branes, giving N copies of the single-brane action.Comment: 34 pages, LaTeX. v2: comments and refs adde

Integrin activation - the importance of a positive feedback

Integrins mediate cell adhesion and are essential receptors for the development and functioning of multicellular organisms. Integrin activation is known to require both ligand and talin binding and to correlate with cluster formation but the activation mechanism and precise roles of these processes are not yet resolved. Here mathematical modeling, with known experimental parameters, is used to show that the binding of a stabilizing factor, such as talin, is alone insufficient to enable ligand-dependent integrin activation for all observed conditions; an additional positive feedback is required.Comment: in press in Bulletin of Mathematical Biolog

Frustrated two-dimensional Josephson junction array near incommensurability

To study the properties of frustrated two-dimensional Josephson junction arrays near incommensurability, we examine the current-voltage characteristics of a square proximity-coupled Josephson junction array at a sequence of frustrations f=3/8, 8/21, 0.382 $(\approx (3-\sqrt{5})/2)$, 2/5, and 5/12. Detailed scaling analyses of the current-voltage characteristics reveal approximately universal scaling behaviors for f=3/8, 8/21, 0.382, and 2/5. The approximately universal scaling behaviors and high superconducting transition temperatures indicate that both the nature of the superconducting transition and the vortex configuration near the transition at the high-order rational frustrations f=3/8, 8/21, and 0.382 are similar to those at the nearby simple frustration f=2/5. This finding suggests that the behaviors of Josephson junction arrays in the wide range of frustrations might be understood from those of a few simple rational frustrations.Comment: RevTex4, 4 pages, 4 eps figures, to appear in Phys. Rev.

Possible implications of the channeling effect in NaI(Tl) crystals

The channeling effect of low energy ions along the crystallographic axes and planes of NaI(Tl) crystals is discussed in the framework of corollary investigations on WIMP Dark Matter candidates. In fact, the modeling of this existing effect implies a more complex evaluation of the luminosity yield for low energy recoiling Na and I ions. In the present paper related phenomenological arguments are developed and possible implications are discussed at some extent.Comment: 16 pages, 10 figures, preprint ROM2F/2007/15, submitted for publicatio