Absence Of Bifurcation Research Articles

Molecular Analysis of Sensory Axon Branching Unraveled a cGMP-Dependent Signaling Cascade.

Axonal branching is a key process in the establishment of circuit connectivity within the nervous system. Molecular-genetic studies have shown that a specific form of axonal branching—the bifurcation of sensory neurons at the transition zone between the peripheral and the central nervous system—is regulated by a cyclic guanosine monophosphate (cGMP)-dependent signaling cascade which is composed of C-type natriuretic peptide (CNP), the receptor guanylyl cyclase Npr2, and cGMP-dependent protein kinase Iα (cGKIα). In the absence of any one of these components, neurons in dorsal root ganglia (DRG) and cranial sensory ganglia no longer bifurcate, and instead turn in either an ascending or a descending direction. In contrast, collateral axonal branch formation which represents a second type of axonal branch formation is not affected by inactivation of CNP, Npr2, or cGKI. Whereas axon bifurcation was lost in mouse mutants deficient for components of CNP-induced cGMP formation; the absence of the cGMP-degrading enzyme phosphodiesterase 2A had no effect on axon bifurcation. Adult mice that lack sensory axon bifurcation due to the conditional inactivation of Npr2-mediated cGMP signaling in DRG neurons demonstrated an altered shape of sensory axon terminal fields in the spinal cord, indicating that elaborate compensatory mechanisms reorganize neuronal circuits in the absence of bifurcation. On a functional level, these mice showed impaired heat sensation and nociception induced by chemical irritants, whereas responses to cold sensation, mechanical stimulation, and motor coordination are normal. These data point to a critical role of axon bifurcation for the processing of acute pain perception.

胆管分岐異常を伴った門脈左右分岐部の欠如の1例

症例は70歳女性．食後の上腹部痛を主訴に受診し，入院精査を行い膵頭部癌と診断された．造影CTにて門脈左枝水平部は欠如し，肝左葉の門脈枝は中肝静脈の腹側をアーチ状に横走する肝内門脈枝を介して描出されており，門脈左右分岐部の欠如と診断した．内視鏡的胆管造影では左右肝管が長く，左肝管はB2＋3および3本のB4がほぼ同じ位置で合流して形成されていた．左肝管に最も右側より合流するB4は肝右縁付近まで描出されており，一部の枝が中肝静脈の腹側をアーチ状に横走する肝内門脈枝と併走していた．肝内門脈枝は，門脈左枝水平部が形成されなかったことに対して，P8とP4の門脈枝の間で形成された肝内門脈吻合枝であると考えられた．門脈左右分岐部の欠如を有する症例では胆管の分岐異常を伴うことが考えられ，術前には詳細な胆管評価が必要である．

074 Risk factors for procedural failure of percutaneous coronary intervention for chronic total occlusion. Impact of novel guide wire “Fielder XT”

Chronic total occlusion (CTO) remains one of the last frontiers of percutaneous coronary intervention (PCI). Recently, a novel “soft” guidewire (GW) developed for tracking invisible micro-channels (Fielder XT) became available in France. The purpose of this study was to clarify the risk factors contributing to PCI success for CTO lesions and evaluate the efficacy and safety of this GW. The study included 166 consecutive Pts with CTO's (European CTO Club definition) who underwent primary PCI at our institution between June 2008 and Feb 2010 by 2 experienced operators. The cohort was divided into 2 groups: group 1 (n = 83), treated before availability of “Fielder XT” GW in France and group 2 (n = 83), treated since availability. Clinical and angiographic characteristics were similar in both groups (age 63.9 ± 11.3 years, lesion length 23.0 ± 18.1 mm, bridging collateral 37.%, tortuosity score 0.16 ± 0.37/1 and calcification score 0.94 ± 1.08/3). Fielder XT was used in 1 case (1.2%) in group 1 and 67 (80.7%) in group 2. Micro catheters were used more frequently in group 2 (73.2% vs 56.6%; p = 0.013) and parallel wire technique was less required (16.2% vs 31.3%; p = 0.011). Angiographic success rate was significantly higher in group 2 (84.3% vs 67.5%; p = 0.005) with a lower rate of dissection (12.2% vs 24.7%; p = 0.02) and a trend for a lower rate of perforation (4.9% vs 1.2%; p = ns). Predictors of failure in the total cohort were by multivariate logistic regression analysis: proximal tortuosity (p = 0.048, OR = 3.15), absence of bifurcation (p = 0.024, OR = 3.39), no visible stump (p<0.0001, OR = 6.25), calcification (p = 0.029, OR = 1.56) and patient in group 1 (p = 0.015, OR = 3.37). Introduction of a dedicated “soft” wire in the CTO treatment strategy improves the angiographic success rate of PCI with a more simple and “soft” technique. Multivariate analysis confirmed classical independent predictors of failure but also demonstrated that a new device may influence success rate.

Bifurcations and sudden current change in ensembles of classically chaotic ratchets

Mateos [Phys. Rev. Lett. 84, 258 (2000)] conjectured that current reversal in a classical deterministic ratchet is associated with bifurcations from chaotic to periodic regimes. This is based on the comparison of the current and the bifurcation diagram as a function of a given parameter for a periodic asymmetric potential. Barbi and Salerno [Phys. Rev. E 62, 1988 (2000)] have further investigated this claim and argue that, contrary to Mateos' claim, current reversals can occur also in the absence of bifurcations. Barbi and Salerno's studies are based on the dynamics of one particle rather than the statistical mechanics of an ensemble of particles moving in the chaotic system. The behavior of ensembles can be quite different, depending upon their characteristics, which leaves their results open to question. In this paper we present results from studies showing how the current depends on the details of the ensemble used to generate it, as well as conditions for convergent behavior (that is, independent of the details of the ensemble). We are then able to present the converged current as a function of parameters, in the same system as Mateos as well as Barbi and Salerno. We show evidence for current reversal without bifurcation, as well as bifurcation without current reversal. We conjecture that it is appropriate to correlate abrupt changes in the current with bifurcation, rather than current reversals, and show numerical evidence for our claims.

Why Newton’s method is hard for travelling waves: Small denominators, KAM theory, Arnold’s linear Fourier problem, non-uniqueness, constraints and erratic failure

Nonlinear travelling waves and standing waves can computed by discretizing the appropriate partial differential equations and then solving the resulting system of nonlinear algebraic equations. Here, we show that the “small denominator” problem of Kolmogorov–Arnold–Moser (KAM) theory is equally awkward for numerical algorithms. Furthermore, Newton’s iteration combined with continuation in a parameter often exhibits “erratic failure” even in the absence of bifurcation. Wave resonances can interlock a countable infinity of branches in an extremely complex topology, as will be illustrated through the fifth-degree Korteweg–deVries equation. Continuation can easily jump, unsuspected, from one branch to another. Constraints, sometimes finite and sometimes infinite in number, are usually needed to specify a unique solution. This confluence of numerical difficulties can be overcome only by combining the latest numerical algorithms with a strong understanding of travelling wave physics.

Phase locking effect and current reversals in deterministic underdamped ratchets

We study the transport properties (currents) of deterministic underdamped ratchets in terms of phase locking dynamics. The occurrence of reverse currents is interpreted in terms of different stability properties of the periodic rotating orbits and is shown to exist also in the absence of bifurcations from chaos to periodic motion. We briefly discuss the effects of noise on this phase locked dynamics.

Absence of Bifurcation in theE-Layer

Absence of Bifurcation in the<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>E</mml:mi></mml:math>-Layer

I. Researches on the foraminifera

119. In my preceding memoirs, I have shown that two very dissimilar types of structure present themselves among the Foraminifera; one characterized by its simplicity, the other by its complexity. In the former, of which Orbitolites , Orbiculina , and Alveolina are typical examples, the calcareous skeleton does not present any definite indications of organization, but seems to have been formed by the simple calcification of a portion of the homogeneous sarcode-body of the animal; that the sarcode-body is but very imperfectly divided into segments, the communications between the cavities occupied by these segments being very free and irregular; the form of the segments themselves, and the mode of their connexion, are alike inconsistent; and even the plan of growth, on which the character of the organism as a whole depends, though preserving a general uniformity, is by no means invariable maintained. In the latter, to which Cycloclypeus and Heterostegina belong, we find the calcareous skeleton presenting a very definite and elaborate organization; the several segments of the body are so completely separated from each other, that they remain connected only by delicate threads of sarcode; each segment thus isolated has its own proper calcareous envelope, which seems to be moulded (as it were) upon it, and this envelope or shell is perforated with minute parallel tubuli, closely resembling those of dentine except in the absence of bifurcation or ramification; the partition-walls between adjacent segments are consequently double, and are strengthened by an intermediate calcareous deposit, which is traversed by a system of inosculating passages that seems properly to belong to it. The form of the segments, their mode of communication, and consequently the general plan of growth, have a very considerable degree of constancy; and altogether the tendency is strongly manifested in this type, to the greater individualization of the parts of the composite body, which in the preceding must be looked upon rather as constituting one aggregate whole. 120. I purpose in the present memoir to carry on this contrast, by presenting a detailed comparison of the structure of two generic forms, which, whilst they so far agree in general plan of growth as not only to have been ranked by M. d'Orbigny side bv side in his order Hélicostègues , but to have been placed by other systematists in close apposition, differ in the most marked manner as to all the particulars just enumerated. Both these types are of peculiar interest:- the first, Peneroplis , on account of the very wide range of variation it presents, which has led to the establishment of three genera , apparently distinguishable by well-marked differences in conformation, upon what I feel satisfied will prove to be but individual modifications of one and the same specific type ;— the second, Operculina , as being the nearest existing representative of Nummulites , and consequently as affording not merely the key to the elucidation of the structure, but also the basis for the determination of the value of the reputed species, of that genus, by the study of the range of variation which it presents; this range being, though more restricted than in the preceding case, still quite sufficient to justify a large multiplication of species, in the estimation of those who do not practise that extended method of comparative inquiry, on the importance of which I have dwelt in a former Memoir (74). With the latter of these genera, as also with Nummulites , I shall prove that the genus Amphistegina is closely allied; although M. d’Orbigny, misled by the marked want of symmetry and by the alternation in the disposition of the chambers, which are exhibited by certain forms of that type, has placed it in a different order, Entomostègues . For I shall have to show that a gradational variety in this respect, ending in complete symmetry, may coincide with such a uniformity in general structure, that even a very decided departure from symmetry must be regarded as a character of little value in classification, compared with agreement in the organization of the shell and in those peculiarities in the conformation of the animal which are indicated by it; and further, that a most marked difference in degree of organization exists between two species of Amphistegina , which so closely resemble each other externally that the young of one may easily be mistaken for the adult of the other.

XX. Researches on the foraminifera.—Part III. On the genera peneroplis, operculina , and amphistegina

In his preceding memoirs, the author has shown that two very dissimilar types of structure present themselves among Foraminifera, one characterized by its simplicity, the other by its complexity. In the former, of which Orbitolites, Orbiculina and Alveolina are typical examples, the calcareous skeleton does not present any definite indications of organization, but seems to have been formed by the simple calcification of a portion of the homogeneous sarcode-body of the animal; that sarcode-body is but very imperfectly divided into segments, the communications between the cavities occupied by these segments being very free and irregular; the form of the segments themselves, and the mode of their connexion, are alike inconstant; and even the plan of growth, on which the character of the organism as a whole depends, though preserving a general uniformity, is by no means invariably maintained. In the latter, to which Cycloclypeus and Heterostegina belong, the calcareous skeleton is found to present a very definite and elaborate organization. The several segments of the body are so completely separated from each other, that they remain connected only by delicate threads of sarcode. Each segment thus isolated has its own proper calcareous envelope, which seems to be moulded (as it were) upon it; and this envelope or shell is perforated with minute parallel tubuli closely resembling those of dentine, except in the absence of bifurcation; the partition-walls between adjacent segments are consequently double, and are strengthened by an intermediate calcareous deposit, which is traversed by a system of inosculating passages that seems properly to belong to it. The form of the segments, their mode of communication, and consequently the general plan of growth, have a very considerable degree of constancy; and altogether the tendency is strongly manifested in this type to the greater individualization of the parts of the composite body, which in the preceding must be looked upon rather as constituting one aggregate whole. In the present memoir this contrast is fully carried out by a detailed comparison of two characteristic examples from these types respectively, each of them having its own features of peculiar interest.