Feynman Diagrams and Differential Equations

We review in a pedagogical way the method of differential equations for the evaluation of D-dimensionally regulated Feynman integrals. After dealing with the general features of the technique, we discuss its application in the context of one- and two-loop corrections to the photon propagator in QED, by computing the Vacuum Polarization tensor exactly in D. Finally, we treat two cases of less trivial differential equations, respectively associated to a two-loop three-point, and a four-loop two-point integral. These two examples are the playgrounds for showing more technical aspects about: Laurent expansion of the differential equations in D (around D=4); the choice of the boundary conditions; and the link among differential and difference equations for Feynman integrals.Comment: invited review article from Int. J. Mod. Phys.

CASTOR: Centauro and Strange Object Research in nucleus-nucleus collisions at LHC

We describe the CASTOR detector designed to probe the very forward, baryon-rich rapidity region in nucleus-nucleus collisions at the LHC. We present a phenomenological model describing the formation of a QGP fireball in a high baryochemical potential environment, and its subsequent decay into baryons and strangelets. The model explains Centauros and the long-penetrating component and makes predictions for the LHC. Simulations of Centauro-type events were done. To study the response of the apparatus to new effects different exotic species (DCC, Centauros, strangelets etc.) were passed through the deep calorimeter. The energy deposition pattern in the calorimeter appears to be a new clear signature of the QGP.Comment: Talk given by E. Gladysz-Dziadus for the CASTOR group, Intern. Workshop on Nuclear Theory, 10-15 June, 2002, Bulgaria, Rila Mountains, 15 pages, 14 figure

Threshold J/ψ−J/\psi- production in nucleon-nucleon collisions

We analyze $J/\psi-$ production in nucleon-nucleon collisions near threshold in the framework of a general model independent formalism, which can be applied to any reaction $N+N\to N+N+V^0$, where $V^0=\omega$, $\phi$, or $J/\psi$. Such reactions show large isotopic effects: a large difference for $pp$- and $pn$-collisions, which is due to the different spin structure of the corresponding matrix elements. The analysis of the spin structure and of the polarization observables is based on symmetry properties of the strong interaction. Using existing experimental data on the different decays of $J/\psi-$meson, we suggest a model for $N+N\to N+N+J/\psi$, based on $t-$channel $\eta+\pi$-exchanges. We predict polarization phenomena for the $n+p\to n+p+J/\psi$-reaction and the ratio of cross sections for $np$ and $pp$-collisions. For the processes $\eta(\pi)+N\to N+J/\psi$ we apply two different approaches: vector meson exchange and local four-particle interaction. In both cases we find larger $J/\psi$-production in $np$-collisions, with respect to $pp$-collisions.Comment: 17 pages, 6 figure

Changes in spastic muscles of patients with infantile cerebral palsy according to ultrasound findings

Infantile cerebral palsy (ICP) occupies a leading position in its prevalence among childhood disabling neurological diseases.Objective: to investigate the structure of spastic muscles in patients with ICP using ultrasonography (USG).Patients and methods. A total of 196 patients with ICP (spastic diplegia) who received a cycle of sanatorium-and-spa treatment underwent clinical, neurological, electromyographic examinations and lower limb muscle USG.Results. It was established that USG could reliably estimate the degree of structural changes in lower limb muscles. An average correlation was found between the level of development, by using the Gross Motor Function Classification System for Cerebral Palsy (GMFCS), and age at contracture formation (R=0.60; p=0.001). Analysis of USG and electromyographic findings in patients with ICP revealed a strong negative correlation with the amplitude and rates (R=-0.81; p=0.002; R=-0.77; p=0.001, respectively) and weak reciprocity-adequacy correlations (R=0.21; p=0.071; R=0.24; p=0.043, respectively).Conclusion. Based on the findings, the authors formed rehabilitation approaches for motor disorders in children with ICP in relation to the magnitude of structural changes in the muscular system

Absorption of phi mesons in near-threshold proton-nucleus reactions

In the framework of the nuclear spectral function approach for incoherent primary proton--nucleon and secondary pion--nucleon production processes we study the inclusive $\phi$ meson production in the interaction of 2.83 GeV protons with nuclei. In particular, the A-dependences of the absolute and relative $\phi$ meson yields are investigated within the different scenarios for its in-medium width as well as for the cross section ratio $\sigma_{pn \to pn{\phi}}/{\sigma_{pp \to pp{\phi}}}$. Our model calculations take into account the acceptance window of the ANKE facility used in a recent experiment performed at COSY. They show that the pion--nucleon production channel contributes distinctly to the $\phi$ creation in heavy nuclei in the chosen kinematics and, hence, has to be taken into consideration on close examination of the dependences of the phi meson yields on the target mass number with the aim to get information on its width in the medium. They also demonstrate that the experimentally unknown ratio $\sigma_{pn \to pn{\phi}}/{\sigma_{pp \to pp{\phi}}}$ has a weak effect on the A-dependence of the relative $\phi$ meson production cross section at incident energy of present interest, whereas it is found to be appreciably sensitive to the phi in-medium width, which means that this relative observable can indeed be useful to help determine the above width from the direct comparison the results of our calculations with the future data from the respective ANKE-at-COSY experiment.Comment: 16 pages, 9 figure

The investigation of dangerous geological processes resulting in land subsidence while designing the main gas pipeline in South Yakutia

The number of gas main accidents has increased recently due to dangerous geological processes in underdeveloped areas located in difficult geological conditions. The paper analyses land subsidence caused by karst and thermokarst processes in the right of way, reveals the assessment criteria for geological hazards and creates zoning schemes considering the levels of karst and thermorkarst hazards

Behavioural and neurochemical consequences of chronic gut microbiota depletion during adulthood in the rat

Gut microbiota colonization is a key event for host physiology that occurs early in life. Disruption of this process leads to altered brain development which ultimately manifests as changes in brain function and behaviour in adulthood. Studies using germ-free mice highlight the extreme impact on brain health that results from life without commensal microbes, however the impact of microbiota disturbances occurring in adulthood is less studied. To this end, we depleted the gut microbiota of 10-week-old male Sprague Dawley rats via chronic antibiotic treatment. Following this marked, sustained depletion of the gut bacteria, we investigated behavioural and molecular hallmarks of gut-brain communication. Our results reveal that depletion of the gut microbiota during adulthood results in deficits in spatial memory as tested by Morris water maze, increased visceral sensitivity and a greater display of depressive-like behaviours in the forced swim test. In tandem with these clear behavioural alterations we found change in altered CNS serotonin concentration along with changes in the mRNA levels of corticotrophin releasing hormone receptor 1 and glucocorticoid receptor. Additionally, we found changes in the expression of BDNF, a hallmark of altered microbiota-gut-brain axis signaling. In summary, this model of antibiotic-induced depletion of the gut microbiota can be used for future studies interested in the impact of the gut microbiota on host health without the confounding developmental influence of early-life microbial alterations

Climate-driven phenological changes in the Russian Arctic derived from MODIS LAI time series 2000–2019

Abstract: Arctic surface temperature has increased at approximately twice the global rate over the past few decades and is also projected to warm most in the 21st century. However, the mechanism of Arctic vegetation response to this warming remains largely uncertain. Here, we analyse variations in the seasonal profiles of MODerate resolution Imaging Spectroradiometer Leaf Area Index (LAI) and ERA-interim cumulative near-Surface Air Temperature (SATΣ) over the northern Russia, north of 60° N for 2000–2019. We find that commonly used broad temporal interval (seasonal) trends cannot fully represent complex interannual variations of the LAI profile over the growing season. A sequence of narrow temporal interval (weekly) LAI trends form an inverted S-shape over the course of the growing season with enhanced green-up and senescence, but balanced during the growing season’s peak. Spatial patterns of weekly LAI trends match with those of weekly SATΣ trends during the green-up, while the drivers of the browning trends during senescence remain unclear. Geographically the area with the statistically significant temperature-driven enhanced green-up is restricted by a large patch carrying significant positive SATΣ trends, which includes North Siberian Lowland, Taimyr, Yamal and adjacent territories. The strength, duration and timing of the changes depend on vegetation type: enhanced green-up is most pronounced in tundra, while enhanced senescence is pronounced in forests. Continued release of the climatic constraints will likely increase the capacity both of the environment (i.e. permafrost thawing) and vegetation (i.e. appearance of more productive woody species), and transform LAI seasonal shifts to change of LAI seasonal amplitude

e^+e^- Pair Production from γ\gamma A Reactions

We present a calculation of e^+e^- production in $\gamma A$ reactions at MAMI and TJNAF energies within a semi-classical BUU transport model. Dilepton invariant mass spectra for $\gamma$C, $\gamma$Ca and $\gamma$Pb are calculated at 0.8, 1.5 and 2.2 GeV. We focus on observable effects of medium modifications of the $\rho$ and $\omega$ mesons. The in-medium widths of these mesons are taken into account in a dynamical, consistent way. We discuss the transport theoretical treatment of broad resonances.Comment: 42 pages including 16 figure

Ultraviolet crosslinking of corneal collagen in patients with thin cornea. Literature review

For the treatment of progressive keratoconus in the early stages, corneal collagen crosslinking is currently actively used. This technique is based on the stabilization of the pathological process by increasing the biomechanical properties of the own cornea. The thickness of the cornea less than 400 microns significantly limits the possibility of a standard cross-linking procedure performing.The article analyzes the literature data on the use of various methods of corneal crosslinking with a corneal thickness of less than 400 microns, which signifi cantly limits the possibilities of the standard procedure.It is known, that during crosslinking, at the initial stage, de-epithelialization of the cornea is performed, which, in the postoperative period, leads to a pronounced corneal syndrome. This determined the direction of the fi rst modifi cations of the technique associated with the use of partial de-epithelialization or its complete absence. Later, during cross-linking of “thin” corneas, techniques with the use of additional covering materials were actively used in order to replenish the missing corneal tissue of the patient during the UV irradiation procedure. Among them are the use of a soft contact lens without an ultraviolet fi lter, the use of a corneal lenticule obtained after SMILE surgery, the use of a protective fl ap of the donor cornea obtained using a femtosecond laser from the residual stroma of the corneal disc after descemet membrane transplantation or posterior lamellar keratoplasty. The variety of the proposed modifications and the ongoing search for better options indicate the demand for this technology and the need for further research, taking into account the individual characteristics of the patient’s ectasia