The Space of Stability Conditions on Abelian Threefolds, and on some Calabi-Yau Threefolds

We describe a connected component of the space of stability conditions on abelian threefolds, and on Calabi-Yau threefolds obtained as (the crepant resolution of) a finite quotient of an abelian threefold. Our proof includes the following essential steps: 1. We simultaneously strengthen a conjecture by the first two authors and Toda, and prove that it follows from a more natural and seemingly weaker statement. This conjecture is a Bogomolov-Gieseker type inequality involving the third Chern character of "tilt-stable" two-term complexes on smooth projective threefolds; we extend it from complexes of tilt-slope zero to arbitrary tilt-slope. 2. We show that this stronger conjecture implies the so-called support property of Bridgeland stability conditions, and the existence of an explicit open subset of the space of stability conditions. 3. We prove our conjecture for abelian threefolds, thereby giving reproving and generalizing a result by Maciocia and Piyaratne. Important in our approach is a more systematic understanding on the behaviour of quadratic inequalities for semistable objects under wall-crossing, closely related to the support property.Comment: 45 pages, 1 figure. v2: addressed referee comments. To appear in Inventiones Mat

Isotropic magnetization response of electrodeposited nanocrystalline Ni–W alloy nanowire arrays

Isotropic magnetization response was demonstrated in electrodeposited nanocrystalline Ni–15 % W alloy nanowire arrays, which can be applied to nanoscale magnetic field sensors. The Ni–W alloy nanowire arrays were electrochemically synthesized on a nanochannel template electrode from an aqueous electrolytic solution. X-ray and electron diffraction patterns revealed that Ni–15 % W alloy deposits were composed of ultrafine crystal grains with a supersaturated solid solution phase. The magnetization of the Ni–15 % W alloy thin films reached saturation at around 2.5 kOe in a perpendicular direction to the film plane, whereas the pure Ni thin films hardly magnetized in the perpendicular direction. On the contrary, Ni–15 % W alloy nanowire arrays were easily magnetized, and reach saturation at around 1.0 kOe, even in a perpendicular direction to the array film plane that corresponds to the long-axis direction of the alloy nanowires

Tannic Acid Modified Silver Nanoparticles Show Antiviral Activity in Herpes Simplex Virus Type 2 Infection

The interaction between silver nanoparticles and herpesviruses is attracting great interest due to their antiviral activity and possibility to use as microbicides for oral and anogenital herpes. In this work, we demonstrate that tannic acid modified silver nanoparticles sized 13 nm, 33 nm and 46 nm are capable of reducing HSV-2 infectivity both in vitro and in vivo. The antiviral activity of tannic acid modified silver nanoparticles was size-related, required direct interaction and blocked virus attachment, penetration and further spread. All tested tannic acid modified silver nanoparticles reduced both infection and inflammatory reaction in the mouse model of HSV-2 infection when used at infection or for a post-infection treatment. Smaller-sized nanoparticles induced production of cytokines and chemokines important for anti-viral response. The corresponding control buffers with tannic acid showed inferior antiviral effects in vitro and were ineffective in blocking in vivo infection. Our results show that tannic acid modified silver nanoparticles are good candidates for microbicides used in treatment of herpesvirus infections.This work was supported by the Polish National Science Centre grant No. 2011/03/B/NZ6/04878 (for MK) and Centre for Preclinical Research and Technology (CePT) Project No. POIG.02.02.00-14-024/08-0 (for MG and MD). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscrip

A consistent picture of the proton release mechanism of oNBA in water by ultrafast spectroscopy and ab initio molecular dynamics

With a combination of transient pump-probe IR spectroscopy and ab initio molecular dynamics, the controversial pico- and nanosecond steps of the o-nitrobenzaldehyde (oNBA) photoreaction have been investigated in aqueous solution. In this way, the measured reaction kinetics have been complemented with an atomistic picture of the reactive events as obtained with unbiased simulations in explicit solvent. Our results allow for a detailed description of the oNBA proton photorelease, a process of fundamental importance and relevant to the use of oNBA as a proton cage in many experiments. In a first step, a stable ketene intermediate is formed on a subpicosecond time scale. This intermediate reacts in a solvent assisted way with an OH transfer to produce nitrosobenzoic acid with a characteristic time of 7 ps. Finally, in permitting pH conditions, this product molecule dissociates a carboxyl proton with a 21 ns time constant. The particular combination of theory and experiment employed in this work appears to be sufficiently general and powerful to find widespread application in the study of ultrafast reactive systems

pH jump induced α-helix folding.

pH can be used to impact the folding equilibrium of peptides and proteins. This fact is utilized, similarly to temperature jumps, in pH jump experiments employing laser time-resolved spectroscopy to study the function and structural dynamics of these molecules. Here the application of pH jumps in folding experiments was investigated. Experiments with poly-L-glutamic acid alpha-helix formation shown the critical aspects of pH jump experiments and yielded direct information about the folding kinetics monitored with the amide I IR band

pH-Jump overshooting

Acid – base systems are commonly expected to equilibrate on a timescale much faster than any other chemical reaction, so their composition can be deduced from the corresponding pKa or pKb values. In a pH-jump experiment done on a multi acid/base pair system, it was found that it takes tens of microseconds before an equilibrium is established. Within that time, the system is kinetically driven reaching surprising states far different from its final equilibrium, for example carboxylate groups were protonated in the presence of hydroxyl ions

Kinetic response of a photoperturbed allosteric protein

By covalently linking an azobenzene photoswitch across the binding groove of a PDZ domain, a conformational transition, similar to the one occurring upon ligand binding to the unmodified domain, can be initiated on a picosecond timescale by a laser pulse. The protein structures have been characterized in the two photoswitch states through NMR spectroscopy and the transition between them through ultrafast IR spectroscopy and molecular dynamics simulations. The binding groove opens on a 100-ns timescale in a highly nonexponential manner, and the molecular dynamics simulations suggest that the process is governed by the rearrangement of the water network on the protein surface. We propose this rearrangement of the water network to be another possible mechanism of allostery