Time-Varying Priority Queuing Models for Human Dynamics

Queuing models provide insight into the temporal inhomogeneity of human dynamics, characterized by the broad distribution of waiting times of individuals performing tasks. We study the queuing model of an agent trying to execute a task of interest, the priority of which may vary with time due to the agent's "state of mind." However, its execution is disrupted by other tasks of random priorities. By considering the priority of the task of interest either decreasing or increasing algebraically in time, we analytically obtain and numerically confirm the bimodal and unimodal waiting time distributions with power-law decaying tails, respectively. These results are also compared to the updating time distribution of papers in the arXiv.org and the processing time distribution of papers in Physical Review journals. Our analysis helps to understand human task execution in a more realistic scenario.Comment: 8 pages, 6 figure

Physiological studies on dormancy in grape seeds (Vitis vinifera var. Black Muscat) II. On the effect of exogenous application of growth substances, low chilling temperature and subjection of the seeds to running water

In order to break the dormancy of grape seeds in the minimum possible time, a number of treatments, including stratification, growth substances and subjecting the seeds to running water, were used. It was observed that grape seeds kept in running water for 8 days germinated in the muslin cloth itself (34.00%). The maximum percentage of germination obtained was 73.00% when the seeds were kept in running water for 16 days. However, the seedling stand was best under the 12 day treatment (72.11 %). This was followed by GA3 treatment (2000 ppm) before stratification, whereby grape seeds germinated within 8 days of stratification and maximum germination percentage was 81.05 after one month. Third best result was obtained under stratification for one month and then a treatment with GA3. Further, grape seeds, when soaked in water for 96 hours, leached some water soluble inhibitor. This could antagonize the germination of GA3 treated grape seeds. When this leached water was bioassayed by the cress seed germination test, it showed the presence of inhibitor at R1 0.7 to 0.85. It appears that the water soluble inhibitor might be responsible for masking the effect of growth substances present in the seeds and thereby disturbing the metabolism of germination.Physiologische Untersuchungen zur Dormanz von Rebensamen (Vitis vinifera var. Black Muscat). II. Über den Einfluß äußerlich angewandter Wuchsstoffe, niedriger Temperaturen und des Auswaschens der Samen in fließendem WasserUm die Dormanz von Rebensamen in der kürzestmöglichen Zeit zu brechen, wurden sie stratifiziert, mit Wuchsstoffen behandelt und in fließendem Wasser ausgewaschen. Es wurde beobachtet, daß Rebensamen, die in einem Musselinsäckchen 8 Tage lang ausgewaschen wurden, schon in dem Säckchen keimten (34,00°/o). Der h öchste Keimungsprozentsatz (73,000/o) wurde erzielt, wenn die Samen 16 Tage lang mit fließendem Wasser behandelt wurden. Bei einer 12tägigen Behandlung (72, 11% gekeimter Samen) war die Standfestigkeit der Sämlinge jedoch am besten. Das zweitbeste Resultat wurde mit GS3-Behandlung (2000 ppm) vor der Stratifikation erzielt, wobei die Rebensamen nach 8tägiger Stratifikation keimten; der höchste Anteil gekeimter Samen betrug - nach 30tägiger Stratifikation - 81,05%. 1monatige Stratifikation mit an schließender GS3-Behandlung lieferte das drittbeste Ergebnis. Ferner gaben Rebensamen, die 96 Std. lang in Wasser gequollen waren , einen wasserlöslichen Inhibitor ab. Dieser konnte die Keimung GS3-behandelter Samen hemmen. Mit Hilfe des Kressewurzeltests ließ sich im Einweichwasser ein Hemmstoff mit ein em Rr von 0,70-0,85 nachweisen. Möglicherweise stört der wasserlösliche Inhibitor den Stoffwechsel der Keimung, so daß die Wirkung der Wuchsstoffe in den Samen verdeckt wird

Fracture strength estimation of L3-L4 intervertebral disc using FEA

Mechanical stress and fracture analysis of the human lumbar intervertebral discs are important in assessing disorders related to lower back pain and ageing. Finite element modelling and simulation approaches assist in easier prediction of the disc behaviour under different load conditions. The causes of mechanical failure and morphological changes still remain partially speculative. The present study addresses the issue by developing a finite element model of an L3-L4 lumbar intervertebral disc subjected to different axial compressive loadings. The morphological deformations and stress concentration regions within the disc are analyzed and reported. A mathematical relation is established to estimate the breaking strength of an L3-L4 intervertebral disc, thus indicating the risk of disc failure based on the applied load

Relativistic mean field study of the properties of Z=117 nucleus and the decay chains of 293,294^{293,294}117 isotopes

We have calculated the binding energy, root-mean-square radius and quadrupole deformation parameter for the recently synthesized superheavy element Z=117, using the axially deformed relativistic mean field (RMF) model. The calculation is extended to various isotopes of Z=117 element, strarting from A=286 till A=310. We predict almost spherical structures in the ground state for almost all the isotopes. A shape transition appears at about A=292 from prolate to a oblate shape structures of Z=117 nucleus in our mean field approach. The most stable isotope (largest binding energy per nucleon) is found to be the $^{288}$117 nucleus. Also, the Q-value of $\alpha$-decay $Q_\alpha$ and the half-lives $T_{\alpha}$ are calculated for the $\alpha$-decay chains of $^{293}$117 and $^{294}$117, supporting the magic numbers at N=172 and/ or 184.Comment: 6 Pages and 8 Figure

A Preliminary Investigation of the Cr3Si-Mo Pseudo-Binary Phase Diagram

An investigation was undertaken to study the phase relations in Cr3Si alloyed with Mo varying from 10 to 83.5 wt. % of the material. Specimens were prepared from arc-melted buttons that were subsequently heat treated at 1673 K for 200 h and air quenched to room temperature to structures. Alloys containing more than 20 wt. % MO were primarily two-phase materials of M3Si and M5Si3, where M is (Cr,Mo). Three alloys contained less than 5% of a third phase, which also had the M5Si3 crystal structure. Differential thermal analysis (DTA) was performed on several specimens at temperatures up to 2073 K in order to determine a solidus curve for the M3Si phase. Since only one DTA peak was observed in each alloy, the M5Si3 phase must melt above 2073 K, the maximum temperature examined. A preliminary pseudo-binary phase diagram for (Cr,Mo)3Si and a portion of the 1673 K isothermal section of the Cr-Mo-Si ternary phase diagram are presented

Mode based frequency behaviour of a cracked beam

Structural analysis is mainly concerned with predicting the behaviour of a structure when subjected to any external excitation. Dynamic analysis of simple structures can be carried out using finite element analysis on various computing platforms such as MatLab. In the case of industrial applications, dynamic analysis is mainly carried out using simulations on softwares such as Ansys. The present paper compares mathematical and simulation analysis of cracked beam and the dynamic behaviour with respect to mode shape and crack position is reported

Dynamics of osteoblasts during bone remodeling cycle

Bone is a dynamic connective tissue which adjusts to load variations through continuous bone remodeling, which occurs due to the dynamic behavior of bone cells. Many researchers made attempts in obtaining the dynamic characteristics of osteoblasts and its role in bone remodeling cycle. While making an effort to understand the effects of mechanical stimuli on the osteoblast, certain ambiguity is observed in the past literatures. This paper is to demonstrate the dynamics of osteoblast cells and exhibition of different natural frequencies during its life cycle. Osteoblast is modeled as a frustum of a sphere, considering it as a continuum model. The three prominent parts of an osteoblast, i.e., membrane, cytoplasm and nucleus are considered with reported material properties. Lifespan of an active osteoblast during bone remodeling cycle is considered as 90 days and progressive osteoblast stages are analysed using Ansys. First ten natural frequencies and mode shapes are extracted for nine stages and reported. It is observed that the natural frequencies of a micron sized osteoblast are in the range of kHz. A mathematical relation for the lifespan of an active osteoblast is obtained using curve fitting for fundamental natural frequencies. The natural frequency for exciting an active osteoblast on each particular day during its lifespan can be derived from the relation. This relation can serve as a guiding tool in bioengineering for in vitro bone cell culturing. Results also throw light on the excitation frequency and natural frequency of an osteoblast for proper analysis purpose. The different modes of vibration of osteoblast is identified and reported

Mathematical modelling for dynamic analysis of cracked L-shape beam

In this paper, a finite element mathematical model to evaluate natural frequencies and Frequency Response Functions (FRFs) of an L-shaped cracked beam structure is established. Dynamics of L-shaped beam structure is a very challenging subject and very little information is reported in literature. L-shaped beam structure is assumed to be fixed at end of the vertical column and free at the other end of the horizontal column. Natural frequencies are evaluated using finite element method in MatLab and simulations using Ansys (Version 18.2) is carried out to validate the mathematical model. Totally 18 cases with different crack positions and three different crack depths are considered for the analysis. Results obtained by both methods are tabulated and find a very good agreement in the results. Reported results can be used as a benchmark for further study of crack propagation and fatigue failure analysis in built-up structures