Successful acute aortomesenteric bypass as a result of favorable circumstances

The author presents an account of a case-history involving ischaemia of the entire small intestine, an acute vascular episode, caused by occlusion of the cranial mesenteric artery. The successful aortomesenteric bypass is presented as an example of the coincidence of favourable circumstances in the solution of the case.     

RETRPROV A system that looks for axioms

 In this paper we shall describe a formal system which enables us to prove theorems within propositional calculus, logic of quantifiers and first order theories, including theorems containing programs. Its main feature relies on generating an additional set of assumptions needed to prove a considered formula. Thus we are able to consider expressions which can become theorems by looking for a special set of assumptions (axioms) and then adding it to the standard set of axioms. Using this system the correctness and equivalence of programs can be determined. In the end we present some experimental results. Received 25 February 1993/11 September 1995     

Graphene Actively Mode‐Locked Lasers

Actively mode‐locked lasers offer varying degrees of flexibility for a wider range of applications than their passively modulated counterparts, due to their capability for electrically controlled ultrahigh repetition rate operation. Graphene based electrooptic modulators with unique advantages of broad operation bandwidth and ultrafast speed are suitable for light modulation in various optoelectronic applications. Here, an actively mode‐locked laser with a graphene based electrooptic modulator is reported for the first time. The active mode‐locking technique combined together with the intracavity nonlinear pulse shortening effect allows the generation of transform‐limited 1.44 ps pulses with pulse energy of 844 pJ. The electrically controlled repetition rate of generated pulses, a key performance advantage of active mode‐locking, is also demonstrated. These results provide a practical and effective approach for actively mode‐locked lasers with broad operation bandwidth and compact footprint, which contributes a new way for applications of two‐dimensional (2D) layered materials in ultrafast lasers.     

Power-Law Decay in the Ionization of H Rydberg Atoms

We consider a classical study of the ionization of hydrogen Rydberg atoms by circularly polarized microwaves (CPM) in the frequency regime, where typically diffusive manner of the ionization is observed [1,2]. The CPM field pulse shape and the atomic initial state influence on the survival probability, S, are investigated in the two-dimensional (2D) Hamiltonian model [3]. This is motivated by the fact that it is possible experimentally to prepare circular states, e.g. by the crossed fields method [4]. For such states and for states with not too large eccentricity the simplified 2D model should be a good approximation of the three-dimensional life for high enough states. Ionization of highly excited hydrogen atoms by linearly polarized microwaves (LPM) has been studied in the last twenty years (e.g. see [5,6]). The very first experimental results [7] were explained theoretically [8] using Monte-Carlo classical simulations. Classically, the ionization occurs due to the break up of the Kolmogorov-Arnold-Moser (KAM) tori when the microwave amplitude is large enough, hence the ionization threshold can be associated with the onset of classical chaos. Therefore, in the presence of an external periodic force we can observe the escape process of an electron to the continuum from a certain phase-space region defined by the initial conditions. For Hamiltonian systems, the escape may be slowed down significantly due to the presence of the remnants of KAM tori (Cantori) and one can observe the power-law (algebraic) decay S ~ t-z from the region containing KAM stability islands rather than exponential decay S ~ exp(-t), in the limit of large time t.     

Retrograde intravenous perfusion--a therapeutic method in trophic defects of the lower extremities. Experience in patients with primary thrombocythemia

Retrograde intravenous perfusion (RIP), so-called Bier's blockade is a relatively new method of treatment of critical ischaemia of the extremities. It is based on the principle of retrograde, i.e. transvenous perfusion of the capillary circulation during which at the time of artificially discontinued circulation in the extremities a high concentration of effective substances in the target tissues is achieved. In addition to the mentioned critical ischaemia Bier's blockade can be successfully used in the treatment of so-called "diabetic foot". It is also possible to implement by this method a local medicamentously induced block of the sympathetic nerves by administration of Guanethidine. In patients with contraindications of systemic fibrinolytic treatment local thrombolysis can be made in phlebothromboses and acral vascular occlusions. In the treatment of tumours on the extremities, e.g. melanoblastome, it is possible to achieve by local administration of cytostatics comparable results, while the incidence of undesirable effects is smaller. The objective of the present work was to make the professional public familiar with this method. On the example of four patients with trophic defects of the lower extremities which developed as a result of primary thrombocythemia the application of Bier's method was demonstrated.     

Anderson accelerated fixed-stress splitting schemes for consolidation of unsaturated porous media

In this paper, we study the robust linearization of nonlinear poromechanics of unsaturated materials. The model of interest couples the Richards equation with linear elasticity equations, generalizing the classical Biot equations. In practice a monolithic solver is not always available, defining the requirement for a linearization scheme to allow the use of separate simulators. It is not met by the classical Newton method. We propose three different linearization schemes incorporating the fixed-stress splitting scheme, coupled with an L-scheme, Modified Picard and Newton linearization of the flow equations. All schemes allow the efficient and robust decoupling of mechanics and flow equations. In particular, the simplest scheme, the Fixed-Stress-L-scheme, employs solely constant diagonal stabilization, has low cost per iteration, and is very robust. Under mild, physical assumptions, it is theoretically shown to be a contraction. Due to possible break-down or slow convergence of all considered splitting schemes, Anderson acceleration is applied as post-processing. Based on a special case, we justify theoretically the general ability of the Anderson acceleration to effectively accelerate convergence and stabilize the underlying scheme, allowing even non-contractive fixed-point iterations to converge. To our knowledge, this is the first theoretical indication of this kind. Theoretical findings are confirmed by numerical results. In particular, Anderson acceleration has been demonstrated to be very effective for the considered Picard-type methods. Finally, the Fixed-Stress-Newton scheme combined with Anderson acceleration shows the best performance among the splitting schemes.     

Blow-assisted multi-jet electrospinning of poly-L-lactic acid nanofibers

Regardless the low production rate, electrospinning remains the attractive technique for the nanofibers production in various fields. Thus, the development of a multi-jet technologies for electrospinning gives an opportunity to scale up and increase throughput of the fibers production. However, the multi-jet electrospinning technologies exhibit one major drawback– electrostatic mutual jet repulsion issue. In present research, we propose air blow-assisted multi-jet electrospinning system allowing production of nanofibers with yield, at least, tenfold higher than single jet electrospinning. The system produces nanofibers in two modes: multi-jet electrospinning and blow-assisted multi-jet electrospinning. In case of the latter, the application of sheath air stream allows the system to overcome the electrostatic mutual repulsion issue. These lead to the reduction of deviation of the polymer solution jets, the reduction of instabilities of the jets and the improvement of the control of the nanofibers deposition. Nanofibers morphology and size were investigated based on the scanning electron microscope micrographs. The comparison of the two modes shows changes in nanofibers morphology from beaded structure to fine nanofibers, and the slight increase in fiber mean size when the blowing assistance was applied to the process.     

Collisions of electrons with hydrogen atoms I. Package outline and high energy code

Being motivated by the applied researchers’ persisting need for accurate scattering data for the collisions of electrons with hydrogen atoms, we developed a computer package–Hex–that is designed to provide trustworthy results for all basic discrete and continuous processes within non-relativistic framework. The package consists of several computational modules that implement different methods, valid for specific energy regimes. Results of the modules are kept in a common database in the unified form of low-level scattering data (partial-wave T$T$-matrices) and accessed by an interface program which is able to produce various derived quantities like e.g. differential and integral cross sections. This article is the first one of a series of articles that are concerned with the implementation and testing of the modules. Here we give an overview of their structure and present (a) the command-line interface program hex-db that can be also easily compiled into a derived code or used as a backend for a web-page form and (b) simple illustrative module specialized for high energies, hex-dwba, that implements distorted and plane wave Born approximation.