A Well in a 'Target' Stratum of a Two-Layered Formation: The Muskat-Riesenkampf Solution Revisited

Explicit analytical solutions are obtained in terms of hydraulic head (pressure) and Darcian velocity for a steady Darcian flow to a point/line sink and array of sinks with refraction of streamlines on a horizontal interface between two layers of constant hydraulic conductivities. The sinks are placed in a 'target' layer between a constant potential plane and interface. An equipotential surface, encompassing the sink represents a horizontal or vertical well, is reconstructed as a quasi-cylinder or quasi-sphere. The method of electrostatic images and theory of holomorphic functions are employed for obtaining series expansion solutions of two conjugated Laplace equations. If the conductivity of the 'target' layer is less than that of the super/sub-stratum, then there is a minimum of the flow rate into the well of a given size. Applications to agricultural drainage and surface DC-electrical resistivity surveying are discussed. © 2010 Springer Science+Business Media B.V

Streets and pedestrian trajectories in an urban district: Bejan's constructal principle revisited

Bejan's (1996) analytical optimum for the average travel time between an arbitrary point in a rectangle and its "gravitating" vertex along a trajectory, consisting of a low-resistance side of the rectangle (street) and a high-resistance internal segment perpendicular to this side, is generalized in the following way: (a) our street length is shorter than the rectangle side; (b) our "internal" segment of the trajectory is tilted with respect to the street at an angle which is either constant (a middle zone of the district) or varies in two other zones where trajectories directly converge to either the vertex or the tip of the street, wherefrom a pedestrian embarks a bus transporting him to the vertex; (c) our double integrals in the criterion and the first-second derivative tests are more cumbersome for evaluation and require computer algebra for calculation. The total energy spent by a moving entity is assumed to be linearly dependent on the length of the walkway or street trajectory segments with two different resistance coefficients. This energy is minimized for an individual particle such that the tilt angle is determined and zonation is done. Then another minimum of the area-averaged " community" energy is searched with the total rectangle area as a constraint and the side ratio of the rectangle as a control variable. Explicit analytical expressions for double integrals and minima are presented. Alternative criteria, involving the travel time, non-constant specific bus fare and area-averaged tilt angle are discussed. © 2014 Elsevier B.V. All rights reserved

Pharmacoeconomic evaluation of apixaban use for the treatment and prevention of venous thromboembolism in the general population and patients with oncological diseases

Aim. To conduct a pharmacoeconomic analysis of the use of the drug Eliquis® (apixaban), belonging to direct oral anticoagulants (DOACs), for the treatment and prevention of deep vein thrombosis (DVT) and/or pulmonary embolism (PE), including in patients suffering from cancer disease compared with other anticoagulants. Materials and Methods. The economic assessment was made from the standpoint of the healthcare of the Russian Federation. Comparative evaluation of the effectiveness of DOACs was carried out on the basis of the combined rate of the incidence of VTE and death from VTE, as well as death from any cause. Safety assessment — based on the rate of major bleeding (MB) and clinically significant non-severe bleeding (CSNSB). The evaluation was performed on the basis of data obtained in the course of previously performed meta-analyses, the results of which were published. The total cost of patient management for each of the compared alternative treatment tactics was estimated by calculating the cost of a course of drug therapy, as well as the cost of managing adverse events in the study horizon, which was 12 months. The conclusion about the most preferred alternative was made on the basis of data on the relationship between the effectiveness and cost of treating the patient. Results. Apixaban compared with dabigatran and rivaroxaban was associated with a lower risk of developing MB and CSNSB. In addition, in patients taking apixaban, there was a trend towards a decrease in the risk of death from any cause compared with patients who used dabigatran and rivaroxaban, which did not reach statistical significance, which in turn led to the choice of the method of pharmacoeconomic analysis — “cost minimization”. It has been established that the use of apixaban is characterized by the lowest costs, the cost of managing one patient amounted to 59 271,89 rubles per year, which is 28,8 % and 27,2 % lower than similar costs for treatment regimens with the original drugs dabigatran and rivaroxaban, respectively. The difference in costs was due to both the cost of treating complications (1362.8 rubles vs. 2536.3 rubles vs. 3170.9 rubles for apixaban, rivaroxaban and dabigatran, respectively), and the cost of treatment and prophylaxis of DOACs (31 514,20 RUB vs 46 434,8 RUB vs 46 790,6 RUB, respectively). Similar results were achieved in the group of patients suffering from oncological diseases, as DOACs also allowed to reduce costs by 4–5 times compared with the use of LMWH. Conclusion. Among the original DOACs and traditional LMWH therapies, the apixaban regimen has the best cost-effectiveness ratio and is the most preferred alternative in terms of pharmacoeconomic analysis

Comparative pharmacoeconomic analysis of the use of apixaban, rivaroxaban and dabigatran for prevention of stroke and embolism in the vessels of the systemic circulation in patients with non-valvular atrial fibrillation

Aim. To compare the effectiveness of direct oral anticoagulants (DOACs) in patients with non-valvular atrial fibrillation (AF) for preventing stroke and systemic thromboembolism (embolism in the vessels of the systemic circulation, systemic embolism) in terms of pharmacoeconomic indicators. Materials and Methods. The economic assessment was carried out from the standpoint of the healthcare system of the Russian Federation. We used published data on the clinical efficacy and safety of DOACs, which were obtained earlier in clinical trials. The efficacy of therapy was assessed by the incidence of ischemic stroke (IS) of systemic embolism (SE), while the safety was assessed by the incidence of major bleeding (MB) and clinically signifi cant minor bleeding (CSNMB). The total cost of patient management for each alternative treatment option included both the cost of drug therapy and the cost of managing adverse events over a study horizon of 12 months. The conclusion about the most preferred alternative was made on the basis of the ratio of effectiveness and cost of treating the patient. Results. The use of apixaban to prevent IS or SE in patients with AF was accompanied by a decrease in the incidence of their development (HR 0.80, 95 % CI 0.73–0.89; HR 0.72, 95 % CI 0.60–0.85 — compared with rivaroxaban and dabigatran, respectively), as well as a decrease in the frequency of MB compared with other DOACs (HR 0.55, 95 % CI 0.53–0.59; HR 0.78, 95 % CI 0.70–0.87 — compared with rivaroxaban and dabigatran, respectively). Since apixaban was more effective and safer than rivaroxaban and dabigatran, a cost-effectiveness approach was applied in this study. The least expensive treatment regimen included apixaban, the direct cost was 33,263 roubles per patient. The advantage was achieved both due to the lower of therapy with apixaban (29.6–34.0 % lower than other DOACs) and the minimum cost of managing the adverse events: for MB and CSNMB, it was reduced by 20.7 % compared to dabigatran and by 44.7 % compared to rivaroxaban; for stroke/SE, it was reduced by 25.9 % and 20.6 %, respectively. Conclusion. In patients with AF, apixaban was more cost-effective compared with rivaroxaban or dabigatran for preventing IS and SE, as it led to higher clinical efficacy and safety while requiring less healthcare system costs

Can heterogeneity of the near-wellbore rock cause extrema of the Darcian fluid inflow rate from the formation (the Polubarinova-Kochina problem revisited)?

Darcian steady 2-D flow to a point sink (vertical well) placed eccentrically with respect to two circles demarcating zones of contrasting permeability is studied by the methods of complex analysis and numerically by MODFLOW package. In the analytical approach, two conjugated Laplace equations for a characteristic flow function are solved by the method of images, i.e. the original sink is mirrored about two circles that generates an infinite system of fictitious sinks and source. The internal circle of the annulus models formation damage (gravel pack) near the well and the ring-shaped zone represents a pristine porous medium. On the external circle the head (pressure) is fixed and on the internal circle streamlines are refracted. The latter is equivalent to continuity of pressure and normal component of specific discharge that is satisfied by the choice of the intensity and loci of fictitious sinks. Flow net and dependence of the well discharge on eccentricity are obtained for different annulus radii and permeability ratios. A non-trivial minimum of the discharge is discovered for the case of the ring domain permeability higher than that of the internal circle. In the numerical solution, a finite difference code is implemented and compared with the analytical results for the two-conductivity zone. Numerical solution is also obtained for an aquifer with a three-conductivity zonation. The case of permeability exponentially varying with one Cartesian coordinate within a circular feeding contour is studied analytically by series expansions of a characteristic function obeying a modified Helmholtz equation with a point singularity located eccentrically inside the feeding contour. The coefficients of the modified Bessel function series are obtained by the Sommerfeld addition theorem. A trivial minimum of the flow rate into a small-radius well signifies the trade-off between permeability variation and short-cutting between the well and feeding contour. © 2010 Elsevier Ltd

Dynamics of postsurgical wound local changes and healing rate during the use of alpha-glutamyl-tryptophan in combination therapy of patients with skin and soft-tissue infections

Skin and soft-tissue infections (SSTI) take the lead in surgical disorders. Changes of local and systemic immunoreactivity highlight the SSTI and hinder treatment due to disease chronicity. The immunotropic therapy could be the useful tool in SSTI treatment. The aim of the study was to assess the dynamics of local changes and and duration of wound healing during the use of alpha-glutamyl-tryptophan (AGT/Thymogen) in the combination therapy of SSTI patients. Material and methods. A sample of 77 individuals aged 18–55 years with moderate SSTI of different localization and with signs of infectious intoxication participated in the randomized, double-blind, parallel group, placebo-controlled clinical trial. The patients were divided into the main (39 people) and control (38 people) groups. The combination therapy of the main group included 100 μg of AGT by intramuscular injection daily during 7 days, whereas the control group received placebo (0,9 % sodium chloride) along the same schedule. Results and discussion. The combination therapy of SSTI patients with AGT significantly decreased the local inflammation, i.e. pain intensity, hyperemia, edema (p = 0,022), infiltration within damage area (p = 0,03). Besides, AGT treatment leads to statistically and clinically significant reduction in the duration of septic wound healing by an average of 2 days as compared to control group. Thus, statistically, and clinically significant superiority of efficacy of alpha-glutamyl-tryptophan in comparison with placebo in reducing the time of healing of purulent wounds of patients with SSTI has been established

The Multiband Photometry of GRB Host Galaxies: Comparison with the Spectral Energy Distributions of Nearby and Theoretical Modeling Galaxies

We present one of the results of $BVRI$ photometry of the hosts of GRB for the host galaxy of GRB 970508 and the theoretical modeling of its continuum spectral energy distribution (SED) to show that it is important to take into account internal extinction in the host galaxies. We compared the BVRI broad-band flux spectrum of the host to template SEDs of local starburst galaxies and found that there is a significant internal extintion in this host. Moreover, this comparison allows us to derive the absolute magnitude (M_{B_{rest}}) and rouhgly estimate reddening (A_V). Population synthesis modeling of the continuum SED for different reddening laws demostrates that the observational data of the host galaxy of GRB 970508 are best fitted by the spectral properties of a model SED with extinction of A_V\approx 2.Comment: 3 pages, 2 figures, poster presentation on 2nd Rome Workshop on Gamma-Ray Bursts in the Afterglow Er

Therapeutic Drug Monitoring for Evaluation of the Efficacy and Safety of Vancomycin in Patients with Orthopaedic Infections

Vancomycin is a drug of choice for the infections caused by methicillin-resistant strains of staphylococci. Its use requires individualised dosing and renal function monitoring.The aim of the study was to evaluate, using therapeutic drug monitoring (TDM), the frequency of reaching target trough serum concentrations (TSCs) and the frequency of renal function impairment in orthopaedic infection patients receiving vancomycin therapy.Materials and methods: the authors carried out a retrospective analysis of vancomycin TSC test results of 457 patients admitted to a purulent osteology department in 2019–2021. The results were grouped according to the number of TSC determination performed as part of TDM (tests 1, 2, and 3). Each of the 3 groups was further divided into 4 subgroups according to the TSCs of vancomycin: ≤9.9 µg/ml (extremely low), 10–14.9 µg/ml (recommended for mild infections), 15–19.9 µg/ml (recommended for bone and joint infections), ≥20 µg/ml (potentially toxic). The results obtained in each group were analysed separately.Results: according to the 1st TDM test, only 9.6% of patients achieved the TSCs of vancomycin recommended for bone and joint infections. Extremely low TSCs, insufficient for treatment of the infections, were found in 64.8% of patients. According to the 2nd and 3rd TSC determinations, dose corrections decreased the percentage of patients with extremely low TSCs to 49.9% and 41.2%, respectively. Potentially toxic TSCs of vancomycin were detected in 48 (10.5%) patients, but renal dysfunction was observed only in 8 (1.75%) of them. The authors exemplify the use of TDM to control the efficacy and safety of vancomycin in patients with pronounced signs of renal function impairment by two clinical cases.Conclusion: with a standard dose of vancomycin, the concentrations recommended for bone and joint infections were reached only in every tenth patient. There was a large percentage of patients with extremely low serum concentrations of the medicinal product (64.8%), but it decreased after dose adjustments. Monitoring of vancomycin concentrations allows for individualised dosing, efficacy control and significant reduction of the risk of adverse kidney reactions

Optimal shape of an anthill dome: Bejan's constructal law revisited

An anthill is modelled as a paraboloid of revolution, whose surface (dome) dissipates heat from the interior of the nest to the ambient air according to the Robin boundary condition, which involves a constant coefficient, given temperature jump and dome's area. The total heat loss of the net is one (integral) component of ants' colony expenditures of energy. Ants, populating the paraboloid, spend also energy individually, by hoisting the load from the ground surface to a certain elevation within the paraboloid and by overcoming a Coulombian resistance, proportional to the trajectory length. In order to count the gross colony expenditures for these mechanical activities all trajectories are integrated over the volume. Ants are assumed to move along the shortest straight lines of their regular sorties between the nest and forest. The three-component energy is mathematically expressed as a closed-form function of only one variable, the paraboloid height-to-width ratio. The minimum of this function is found by a routine of computer algebra. The proposed model amalgamates into a single and relatively simple function, tractable by standard calculus, the property of the whole structure (dome area) with labouring of insects-comrades. The ants are sociobiologically analogized with Bejan's builders of ancient pyramids and contemporary designers of man-made "dream-houses" or "dream-prisons". © 2012 Elsevier B.V