Nitric oxide (NO) is an endogenous diatomic molecule important in regulation of numerous physiological functions. The photorelease of NO in a controlled manner can potentially be used in photodynamic therapy (PDT). We present here a method to combine S-nitrosocysteine with TiO(2) nanotube-doped PbS quantum dots (PbS QDs) as a nitric oxide-releasing vehicle to promote production of singlet oxygen. The PbS QDs with a diameter ∼3.6 nm (PbS/TNTs) were attached to the TiO(2) nanotube by using a thiolactic acid linker. S-nitrosocysteine-decorated PbS/TiO(2) nanotubes were prepared by dipping PbS/TNTs in a cysteine solution followed by nitrosylation. The results suggest that this hybrid nanomaterial is capable of photoreleasing nitric oxide and producing singlet oxygen using near-IR light.

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This work is an an early stage of a larger project aiming at answering the question whether or not the Preisach map is really ngerprinting magnetic materials. More precisely, we are interested whether the Preisach model of magnetic hysteresis indeed contains any physics or is just a convenient modeling tool. To this extent we study a very simple mechanical system, thus fully tractable, subjected to the external force. Despite of its simplicity, our model captures all the fundamental features of real magnetic materials, namely their hysteretic behavior, coercivity, remanent magnetization, and saturation at high elds. Both the overall shape of major hysteresis loop as well as rst order reversal curves are reproduced quite correctly; they are very similar to those observed in magnetic materials. The model essentially consists of a single, spring loaded, rigid and rotative bar with non-zero friction torque. The length of a projection of this bar onto the direction of an external force is identied with magnetization. The friction torque and the spring constant are the only freely adjustable parameters of our model. In this situation, it seems natural to develop systematic studies in that matter, starting from the simplest models and making them more realistic (and more complex) later. Here we present our rst attempt in this direction. The modelIn our model (see Fig. 1) a sti rod can be rotated around the axis located at (0, 0). The rod is connected with the rotation axis by means of a spring. An external force is applied either parallel or antiparallel to the x-axis, so the rod's deection θ from vertical direction may never exceed π/2. A static friction between the rod and its rotation axis is present. No movement is possible whenever the torque produced by spring and the external force has lower magnitude than the static friction torque, i.e. whenwhere the spring torque τ s = −kθ, with the dimensionless parameter k being called spring constant from now on, and the external force produced torque is τ F = (µ × F ) z = µ sin θ − π 2 = µ cos θ, where µ (≡ 1) is the length of a rod, and, nally, τ f is the static friction torque.When the relation (1) is not satised, the rod rotates in the direction dictated by the sign of τ s + τ F until the equilibrium condition (13)