Azaphosphatrane Organocatalysts in Confined Space: Cage Effect in CO2 Conversion

The endohedral functionalization of a molecular cage by an azaphosphatrane unit has allowed for the creation of highly engineered catalytic cavities for efficient conversion of CO ₂ into cyclic carbonates. Strong structure/activity/stability correlations have been demonstrated by careful adjustment of the size, shape, and electronic properties of the hemicryptophane host.     

Evaluation of the synergetic radio-chemotherapy effects of the radio labelled cisplatin for the treatment of glioma

The proposal of this work was to investigate the effect of the radioactive (NH₃)₂PtCl₂, cis-diamminedichloroplatinum (II) or CDDP* on malignant glioma cells and verify if the low-dose continuous internal radio-chemotherapy would be able to produce additive effects. The antitumoral activity of CDDP* and the non labeled cisplatin, CDDP, were evaluated in glioblastoma. Cisplatin was cytotoxic for glioblastoma cells in a dose dependent manner. Treatment with CDDP*, (IC₅₀ = 1.75 ± 0.07 μM), proved to be more potent than using just CDDP, (IC₅₀ = 4.96 ± 0.40 μM). These results suggest that cisplatin is a very potent radiosensitizer evoking a supra additive effect. Internal radio-chemotherapy treatment based on CDDP* may be useful alternative to reduce the drug concentration required for effective inhibition of glioblastoma growth.     

Instability regimes and self-excited vibrations in deep drilling systems

This paper analyzes the stability of the discrete model proposed by Richard et al. (2004 [1], 2007 [2]) to study the self-excited axial and torsional vibrations of deep drilling systems. This model, which relies on a rate-independent bit/rock interaction law, reduces to a coupled system of state-dependent delay differential equations governing the axial and angular perturbations to the stationary motion of the bit. A linear stability analysis indicates that, although the steady-state motion of the bit is always unstable, the nature of the instability depends on the nominal angular velocity Ω₀ of the drillstring imposed at the rig. On the one hand, if Ω₀ is larger than a critical velocity Ω_c, the angular dynamics is responsible for the instability. However, on the timescale of the resonance period of the drillstring viewed as a torsional pendulum, the system behaves like a marginally stable one, provided that exogenous perturbations are of limited magnitude. The instability then only appears on a much larger timescale, in the form of slowly growing oscillations that ultimately lead to an undesired drilling regime such as bit-bouncing or stick-slip vibrations. On the other hand, if Ω₀ is smaller than Ω_c, the instability manifests itself on the timescale of the bit motion due to a dominating unstable axial dynamics; perturbations to the steady-state motion then rapidly degenerate into stick-slip limit cycles or bit-bouncing. For typical deep drilling field conditions, the critical angular velocity Ω_c is virtually independent of the axial force acting on the bit and of the bit bluntness. It can be approximated by a power law monomial, a function of known parameters of the drilling system and of the intrinsic specific energy (a quantity characterizing the energy required to drill a particular rock). This approximation holds on account that the dissipation in the drilling structure is negligible with respect to that taking place through the bit/rock interaction, as is typically the case. These findings are further illustrated on an example of deep drilling and shown to match the trends observed in the field.     

Relativistic Approach to the Hydrogen Atom in a Minimal Length Scenario

We show that relativistic contributions to the ground-state energy of the hydrogen atom from a minimal length introduced by a Lorentz-covariant algebra are more important than non-relativistic contributions; the non-relativistic approach is therefore unsuitable. We compare our result with experimental data to estimate an upper bound of the order 10^?20m for the minimal length.     

Aqueous Copper‐Mediated Living Radical Polymerisation of N‐Acryloylmorpholine,SET‐LRP in Water

The polymerisation of N‐acryloylmorpholine in water is reported utilising Cu(0)‐mediated living radical polymerisation (SET‐LRP). The inherent instability of [Cu^I(Me₆‐Tren)Br] in aqueous solution is exploited via rapid disproportionation to prepare Cu(0) particles and [Cu^II(Me₆‐Tren)Br₂] in situ prior to addition of monomer and initiator. Quantitative conversion is attained within 30 min for various degrees of polymerisation (DP_n = 20–640) with SEC showing symmetrical narrow molecular weight distributions (Đ < 1.18) in all cases. Optimised conditions are subsequently applied for the preparation of a diblock copolymer poly(NIPAm)‐b‐(N‐acryloylmorpholine), illustrating the versatility of this approach.

     

Symmetry of components and Liouville theorems for noncooperative elliptic systems on the half-space

We study classical solutions of elliptic systems in the half-space and provide sufficient conditions for having symmetry (or proportionality) of components, i.e. u=Kv$u=Kv$ with K>0$K>0$, which then reduces the system to the scalar case. Under a natural structure condition on the nonlinearities, we show that solutions with sublinear growth, hence in particular bounded solutions, are symmetric. Noncooperative, nonvariational systems as well as supercritical nonlinearities can be covered. We also give an instance of our proportionality results without growth restriction on the solutions. As a consequence, we obtain new Liouville-type theorems in the half-space, as well as a priori estimates and existence results for related Dirichlet problems. Our proofs are based on a maximum principle, on the properties of suitable half-spherical means, on a rigidity result for superharmonic functions and on nonexistence of solution for scalar inequalities on the half-space.     

Multivalued Exponentiation Analysis. Part III: Forward Exponentials

We continue our work on exponentiability of multivalued maps on Banach spaces. In Part I we studied the exponentiability of a map F : X ? X by using a Maclaurin expansion approach. In Part II we studied the recursive exponentiation approach. Recursive exponentials are built by using the trajectories of a discrete-time evolution system governed by F. We now focus the attention on forward exponentiability. The forward exponential of F at the point x is defined as the Kuratowski limit $$e^{F}(x):=\lim\limits_{n\to\infty}\; \left(I+ n^{-1} F \right)^{n}(x).$$ This type of exponential arises in connection with the Euler discretization scheme for solving the first-order differential inclusion \(\dot \psi (t)\in F(\psi (t))\) .     

Two-dedicated-machine scheduling problem with precedence relations to minimize makespan

Two-dedicated-parallel-machine scheduling problem with precedence constraints to minimize makespan is considered. This problem originally appeared as a sub-problem in assembly line balancing but it has also its own applications. Complexity and approximation results for this scheduling problem and its special cases with chains of jobs or equal-processing-times are presented.     

Calcite Reinforced Silica–Silica Joints in the Biocomposite Skeleton of Deep‐Sea Glass Sponges

The hierarchically structured glass sponge Caulophacus species uses the first known example of a silica and calcite biocomposite to join the spicules of its skeleton together. In the stalk and body skeleton of this poorly known deep‐sea glass sponge siliceous spicules are modified by the addition of conical calcite seeds, which then form the basis for further silica secretion to form a spinose region. Spinose regions on adjacent spicules are then joined by siliceous crosslinks, leading to unusually strong cross‐spicule linkages. In addition to the biomaterials implications it is now clear, from this first record of a biomineral other than silica, that the hexactinellid sponges are capable of synthesizing calcite, the ancestral skeletal material. We propose that, while the low concentrations of calcium in deep sea waters drove the evolution of silica skeletons, the brittleness of silica has led to retention of the more resilient calcite in very low concentrations at the skeletal joints.