Development of Morphogen Gradient: The Role of Dimension and Discreteness

The fundamental processes of biological development are governed by multiple signaling molecules that create non-uniform concentration profiles known as morphogen gradients. It is widely believed that the establishment of morphogen gradients is a result of complex processes that involve diffusion and degradation of locally produced signaling molecules. We developed a multi-dimensional discrete-state stochastic approach for investigating the corresponding reaction-diffusion models. It provided a full analytical description for stationary profiles and for important dynamic properties such as local accumulation times, variances and mean first-passage times. The role of discreteness in developing of morphogen gradients is analyzed by comparing with available continuum descriptions. It is found that the continuum models prediction about multiple time scales near the source region in two-dimensional and three-dimensional systems is not supported in our analysis. Using ideas that view the degradation process as an effective potential, the effect of dimensionality on establishment of morphogen gradients is also discussed. In addition, we investigated how these reaction-diffusion processes are modified with changing the size of the source region

Theoretical Analysis of Dynamic Processes for Interacting Molecular Motors

Biological transport is supported by collective dynamics of enzymatic molecules that are called motor proteins or molecular motors. Experiments suggest that motor proteins interact locally via short-range potentials. We investigate the fundamental role of these interactions by analyzing a new class of totally asymmetric exclusion processes where interactions are accounted for in a thermodynamically consistent fashion. Theoretical analysis that combines various mean-field cal- culations and computer simulations suggests that dynamic properties of molecular motors strongly depend on interactions, and correlations are stronger for interacting motor proteins. Surprisingly, it is found that there is an optimal strength of interactions (weak repulsion) that leads to a maxi- mal particle flux. It is also argued that molecular motors transport is more sensitive to attractive interactions. Applications of these results for kinesin motor proteins are discussed

Theoretical analysis of degradation mechanisms in the formation of morphogen gradients

Fundamental biological processes of development of tissues and organs in multicellular organisms are governed by various signaling molecules, which are called morphogens. It is known that spatial and temporal variations in the concentration profiles of signaling molecules, which are frequently referred as morphogen gradients, lead to a cell differentiation via activating specific genes in a concentration-dependent manner. It is widely accepted that the establishment of the morphogen gradients involves multiple biochemical reactions and diffusion processes. One of the critical elements in the formation of morphogen gradients is a degradation of signaling molecules. We develop a new theoretical approach that provides a comprehensive description of the degradation mechanisms. It is based on the idea that the degradation works as an effective potential that drives the signaling molecules away from the source region. Utilizing the method of first-passage processes, the dynamics of the formation of morphogen gradients for various degradation mechanisms is explicitly evaluated. It is found that linear degradation processes lead to a dynamic behavior specified by times to form the morphogen gradients that depend linearly on the distance from the source. This is because the effective potential due to the degradation is quite strong. At the same time, nonlinear degradation mechanisms yield a quadratic scaling in the morphogen gradients formation times since the effective potentials are much weaker. Physical-chemical explanations of these phenomena are presented

Study of Tool Wear and Overcut in EDM Process with Rotary Tool and Magnetic Field

Tool wear and workpiece overcut have been studied in electrical discharge machining process with rotational external magnetic field and rotational electrode. Experiments have been divided to three main regimes, namely, low-energy regime, middle-energy regime, and high-energy regime. The influence of process parameters were investigated on electrode wear rate and overcut. Results indicate that applying a magnetic field around the machining gap increases the electrode wear rate and overcut. Also, rotation of the tool has negative effect on overcut

All-time dynamics of continuous-time random walks on complex networks

The concept of continuous-time random walks (CTRW) is a generalization of ordinary random walk models, and it is a powerful tool for investigating a broad spectrum of phenomena in natural, engineering, social, and economic sciences. Recently, several theoretical approaches have been developed that allowed to analyze explicitly dynamics of CTRW at all times, which is critically important for understanding mechanisms of underlying phenomena. However, theoretical analysis has been done mostly for systems with a simple geometry. Here we extend the original method based on generalized master equations to analyze all-time dynamics of CTRWmodels on complex networks. Specific calculations are performed for models on lattices with branches and for models on coupled parallelchain lattices. Exact expressions for velocities and dispersions are obtained. Generalized fluctuations theorems for CTRW models on complex networks are discussed

Economic importance and GIS mapping of medicinal plants in Iran: A Case study of Darkesh

Iran with a wide diversity of wild medicinal plants (8,000 Medicinal plants) is increasingly becoming a valuable source of household income for many rural people. We showed that economic potential of the wild medicinal plant and their contribution to the local people’s livelihoods. This study identified the economic importance of medicinal plants and evaluated with Geographical Information System (GIS) tool to develop spatial maps covering medicinal plants prevalent in Darkesh area, Northern Khorasan, Iran. Then provide the coordinates of the identified area as your results. 10 medicinal plants belonging to 4 families were collected and its geographical distribution is illustrated in the GIS map. More than 50 species were collected and 10 species being the most frequently collected in this area. Most plants were collected in the form of whole plant. It was estimated that at least 18.000 USD are being annually traded in study area, the 10 species most frequently collected contributing most of the retail value. Results from this study indicate that the collection of certain medicinal plants could be increased livelihood for edge community of natural resources. Also, the geographical location of medicinal plants facilitates easy access of medicinal plant's natural habitat and would help to find out potential of medicinal plants in the study area.Keywords: Medicinal plants, Geographical distribution, GIS Mapping, Darkesh, Ira

Detection and Management of Common Medication Errors inInternal Medicine Wards: Impact on Medication Costs and Patient Care

Introduction: Medication errors (MEs) are a leading cause of morbidity and mortality, yet they have remained as confusing and underappreciated concept. The complex pharmacotherapy in hospitalized patients and sometimes serious clinical consequences of MEs necessitate continued report and surveillance of MEs as well as persistent pharmaceutical care for patients at medical wards. This study evaluated the frequency, types, clinical significance, and costs of MEs in internal medicine wards. Method: In this 8-month prospective and cross-sectional study, an attending clinical pharmacist, as an integral member of a health care team, visited the patients during each physician's ward round at the morning. All MEs including prescription, transcription, and administration errors were detected, recorded, and subsequently appropriate corrective interventions were proposed during these rounds. The changes in the medications' cost after implementing clinical pharmacist's interventions were compared to the calculated medications' cost, assuming that the MEs would not have been detected by clinical pharmacist and continued up to discharge time of the patients. Results: 89% of the patients experienced at least one ME during their hospitalization. A mean of 2.6 errors per patient or 0.2 errors per ordered medication occurred in this study. More than 70% of MEs happened at the prescription stage by treating physicians. The most prevalent prescription errors were inappropriate drug selection, unauthorized drugs and untreated indication. The highest MEs occurred on cardiovascular agents followed by antibiotics, and vitamins, minerals, and electrolytes. Total number of MEs showed a marked correlation with the total number of ordered medications and patients’ length of hospitalization. The net effect of clinical pharmacist’s contributions in medication therapy management was to decline medications’ costs by 33.9%. None of the MEs caused the patients harm. Conclusion: The role of clinical pharmacy services in detection, prevention and reducing the cost of MEs is of paramount importance to internal medicine wards. Key words: clinical pharmacist; medication errors; pharmaceutical care; internal medicine