Flow Equations for U_k and Z_k

By considering the gradient expansion for the wilsonian effective action S_k of a single component scalar field theory truncated to the first two terms, the potential U_k and the kinetic term Z_k, I show that the recent claim that different expansion of the fluctuation determinant give rise to different renormalization group equations for Z_k is incorrect. The correct procedure to derive this equation is presented and the set of coupled differential equations for U_k and Z_k is definitely established.Comment: 5 page

Stability of a cubic fixed point in three dimensions. Critical exponents for generic N

The detailed analysis of the global structure of the renormalization-group (RG) flow diagram for a model with isotropic and cubic interactions is carried out in the framework of the massive field theory directly in three dimensions (3D) within an assumption of isotropic exchange. Perturbative expansions for RG functions are calculated for arbitrary $N$ up to the four-loop order and resummed by means of the generalized Pad$\acute{\rm e}$-Borel-Leroy technique. Coordinates and stability matrix eigenvalues for the cubic fixed point are found under the optimal value of the transformation parameter. Critical dimensionality of the model is proved to be equal to $N_c=2.89 \pm 0.02$ that agrees well with the estimate obtained on the basis of the five-loop \ve-expansion [H. Kleinert and V. Schulte-Frohlinde, Phys. Lett. B342, 284 (1995)] resummed by the above method. As a consequence, the cubic fixed point should be stable in 3D for $N\ge3$, and the critical exponents controlling phase transitions in three-dimensional magnets should belong to the cubic universality class. The critical behavior of the random Ising model being the nontrivial particular case of the cubic model when N=0 is also investigated. For all physical quantities of interest the most accurate numerical estimates with their error bounds are obtained. The results achieved in the work are discussed along with the predictions given by other theoretical approaches and experimental data.Comment: 33 pages, LaTeX, 7 PostScript figures. Final version corrected and added with an Appendix on the six-loop stud

Three-loop renormalization group analysis of a complex model with stable fixed point: Critical exponents up to ϵ3\epsilon^3 and ϵ4\epsilon^4

The complete analysis of a model with three quartic coupling constants associated with an O(2N)--symmetric, a cubic, and a tetragonal interactions is carried out within the three-loop approximation of the renormalization-group (RG) approach in $D=4-2\epsilon$ dimensions. Perturbation expansions for RG functions are calculated using dimensional regularization and the minimal subtraction (MS) scheme. It is shown that for $N\ge 2$ the model does possess a stable fixed point in three dimensional space of coupling constants, in accordance with predictions made earlier on the base of the lower-order approximations. Numerical estimate for critical (marginal) value of the order parameter dimensionality $N_c$ is given using Pad\'e-Borel summation of the corresponding $\epsilon$--expansion series obtained. It is observed that two-fold degeneracy of the eigenvalue exponents in the one-loop approximation for the unique stable fixed point leads to the substantial decrease of the accuracy expected within three loops and may cause powers of $\sqrt{\epsilon}$ to appear in the expansions. The critical exponents $\gamma$ and $\eta$ are calculated for all fixed points up to $\epsilon^3$ and $\epsilon^4$, respectively, and processed by the Borel summation method modified with a conformal mapping. For the unique stable fixed point the magnetic susceptibility exponent $\gamma$ for N=2 is found to differ in third order in $\epsilon$ from that of an O(4)--symmetric point. Qualitative comparison of the results given by $\epsilon$--expansion, three-dimensional RG analysis, non-perturbative RG arguments, and experimental data is performed.Comment: 30 pages, LaTeX, no figures. To be published in Phys. Rev. B, V.57, Jan. issue (1998

Ubiquitin ligase UBR3 regulates cellular levels of the essential DNA repair protein APE1 and is required for genome stability

APE1 (Ref-1) is an essential human protein involved in DNA damage repair and regulation of transcription. Although the cellular functions and biochemical properties of APE1 are well characterized, the mechanism involved in regulation of the cellular levels of this important DNA repair/transcriptional regulation enzyme, remains poorly understood. Using an in vitro ubiquitylation assay, we have now purified the human E3 ubiquitin ligase UBR3 as a major activity that polyubiquitylates APE1 at multiple lysine residues clustered on the N-terminal tail. We further show that a knockout of the Ubr3 gene in mouse embryonic fibroblasts leads to an up-regulation of the cellular levels of APE1 protein and subsequent genomic instability. These data propose an important role for UBR3 in the control of the steady state levels of APE1 and consequently error free DNA repair

Goal-directed and habitual control in the basal ganglia: implications for Parkinson's disease

Progressive loss of the ascending dopaminergic projection in the basal ganglia is a fundamental pathological feature of Parkinson's disease. Studies in animals and humans have identified spatially segregated functional territories in the basal ganglia for the control of goal-directed and habitual actions. In patients with Parkinson's disease the loss of dopamine is predominantly in the posterior putamen, a region of the basal ganglia associated with the control of habitual behaviour. These patients may therefore be forced into a progressive reliance on the goal-directed mode of action control that is mediated by comparatively preserved processing in the rostromedial striatum. Thus, many of their behavioural difficulties may reflect a loss of normal automatic control owing to distorting output signals from habitual control circuits, which impede the expression of goal-directed action. © 2010 Macmillan Publishers Limited. All rights reserved

Crying spells triggered by thumb-index rubbing after thalamic stroke: a case report

BACKGROUND: Pathologic crying, devoid of any emotional counterpart, is known to occur as a consequence of various brain stem, cortical hemispheric and cerebellar lesions or, quite exceptionally, of “dacrystic” epilepsy. The case reported here suggests that thalamic lesions may also cause crying spells, under the special circumstances described below. CASE PRESENTATION: After a mild left thalamic stroke a caucasian 77 years old man presented with crying spells with no emotional counterpart, triggered by thumb-index rubbing of his right hand. Only a modest sensation loss on right infra-orbital and nose-labial areas and the first three right fingers could be detected at clinical examination. The circumstances and processes leading to the crying spells were investigated, together with their neural substrate. Brain computerized tomography (CT), magnetic resonance imaging (MRI) and functional magnetic resonance imaging (fMRI) were conducted. Neurophysiologic studies included Video-Electroencephalography, Electromyography, motor and sensory Evoked potentials. Active thumb-index rubbing, passive fingertips stimulation and interaction of sensory-motor stimulation with cognitive/speech activities were tested under different paradigms. A treatment with pregabalin (75 mg twice a day) was attempted. CT and MRI showed a small ischemic infarct in the left ventral postero-lateral thalamus, while fMRI led to the expected findings, i.e. a bilateral activation of the hand motor representation during the crying-triggering right-hand finger rubbing activity. Sensory potentials evoked from stimulation of the right upper limb were the only abnormal neurophysiologic test. Crying spells could be invariably evoked by both real and imagined active finger rubbing, in either the left of right hemi-space. Rubbing by an examiner was ineffective. Immersion in water (18 °C) but not oiling of the fingertips prevented the symptom. Administration and discontinuation of pregabalin 75 mg daily could be associated with suppression and reappearance of the symptom, respectively. CONCLUSIONS: In this patient loss of sensation seemed to generate crying spells rather than the more common allodynia. As a matter of speculation, both symptoms might represent responses to a sensory loss, but in this case the pathway might have been selectively affected providing inhibition from the lateral to the medial segment of the VPLT, which is linked to the anterior cingulate (limbic) cortex engaged in emotional behaviour. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/s13104-017-2425-z) contains supplementary material, which is available to authorized users

Global variation in anastomosis and end colostomy formation following left-sided colorectal resection

Background End colostomy rates following colorectal resection vary across institutions in high-income settings, being influenced by patient, disease, surgeon and system factors. This study aimed to assess global variation in end colostomy rates after left-sided colorectal resection. Methods This study comprised an analysis of GlobalSurg-1 and -2 international, prospective, observational cohort studies (2014, 2016), including consecutive adult patients undergoing elective or emergency left-sided colorectal resection within discrete 2-week windows. Countries were grouped into high-, middle- and low-income tertiles according to the United Nations Human Development Index (HDI). Factors associated with colostomy formation versus primary anastomosis were explored using a multilevel, multivariable logistic regression model. Results In total, 1635 patients from 242 hospitals in 57 countries undergoing left-sided colorectal resection were included: 113 (6·9 per cent) from low-HDI, 254 (15·5 per cent) from middle-HDI and 1268 (77·6 per cent) from high-HDI countries. There was a higher proportion of patients with perforated disease (57·5, 40·9 and 35·4 per cent; P < 0·001) and subsequent use of end colostomy (52·2, 24·8 and 18·9 per cent; P < 0·001) in low- compared with middle- and high-HDI settings. The association with colostomy use in low-HDI settings persisted (odds ratio (OR) 3·20, 95 per cent c.i. 1·35 to 7·57; P = 0·008) after risk adjustment for malignant disease (OR 2·34, 1·65 to 3·32; P < 0·001), emergency surgery (OR 4·08, 2·73 to 6·10; P < 0·001), time to operation at least 48 h (OR 1·99, 1·28 to 3·09; P = 0·002) and disease perforation (OR 4·00, 2·81 to 5·69; P < 0·001). Conclusion Global differences existed in the proportion of patients receiving end stomas after left-sided colorectal resection based on income, which went beyond case mix alone