Identification of cell-to-cell heterogeneity through systems engineering approaches

Cells in a genetically homogeneous cell-population exhibit a significant degree of heterogeneity in their responses to an external stimulus. To understand origins and importance of this heterogeneity, individual-based population model (IBPM), where parameters follow probability density functions (PDFs) instead of being constants, has been previously developed. However, parameter identification for an IBPM is challenging as estimating PDFs is computationally expensive. Also, because of experimental limitations and nonlinearity of models, not all parameters' PDFs are identifiable. Motivated by the above considerations, a new methodology is proposed in this study. First, a subset of parameters whose PDFs is identifiable are determined through sensitivity analysis, and only these PDFs are estimated. Second, an artificial neural network model is developed to find an empirical relation between these parameter and output PDFs to reduce computational costs of the parameter identification. The proposed approach is validated by estimating PDFs of parameters of a tumor necrosis factor-α signaling model.     

Structural and optical characterization of Ni-doped CdS quantum dots

Ni-doped CdS quantum dots have been prepared by chemical precipitation technique. The X-diffraction results indicated that the particle size of Ni-doped CdS nanoparticles is smaller than that of undoped CdS and no secondary phase was observed. The average grain size of the nanoparticles is found to lie in the range of 2.7–4 nm. The compositional analysis results show that Cd, Ni, and S are present in the samples. HRTEM studies reveal that the average particle size of undoped and Ni-doped CdS quantum dots is 2 and 3 nm, respectively. Raman spectra shows that 1LO, 2LO, and 3LO peaks of the Ni-doped CdS samples are slightly red shifted when compared to that of undoped CdS. The absorption edge of Ni-doped CdS nanoparticles is found to shift towards the higher-wavelength (red shift) side when compared to that of undoped CdS and the band gap is observed to lie in the range of 3.79–3.95 eV. This band gap is higher than that of the bulk CdS and is due to quantum confinement effect present in CdS nanoparticles.     

Distribution of cholesterol in milk fat fractions

Milk fat was fractionated into liquid (m.p. congruent to 12 degrees C), intermediate (m.p. congruent to 21 degrees C) and solid (m.p. congruent to 39 degrees C) fractions by three different processes--melt crystallization, short-path distillation and supercritical CO2 extraction--and the cholesterol content of these fractions determined. Cholesterol was enriched in the liquid fractions from all three processes, in particular about 80% of the cholesterol being found in the liquid fraction obtained by short-path distillation. The basis of migration of cholesterol into various milk fat fractions was explained by its affinity to various triglycerides (melt crystallization) and by vapour pressure and molecular weight (short-path distillation). It was more complex in the supercritical CO2 extraction process; the interplay of cholesterol affinity toward CO2 and its molar volume, and its vapour pressure enhancement under applied pressure play a role.     

Blast-related fracture patterns: a forensic biomechanical approach

Improved protective measures and medical care has increased the survivability from battlefield injuries. In an attempt to reduce the debilitating consequences of blast injury, understanding and mitigating the effects of explosion on the extremities is key. In this study, forensic biomechanical analyses have been applied to determine mechanisms of injury after the traumatic event. The aims of this study were (i) to determine which effects of the explosion are responsible for combat casualty extremity bone injury in two distinct environments, namely open, free-field (open group), and in vehicle or in cover (enclosed group), and (ii) to determine whether patterns of combat casualty bone injury differed between environments. Medical records of casualties admitted to a military hospital in Afghanistan were reviewed over a six-month period. Explosive injuries have been sub-divided traditionally into primary, secondary and tertiary effects. All radiographs were independently reviewed by a military radiologist, a team of military orthopaedic surgeons and a team of academic biomechanists, in order to determine ‘zones of injury’ (ZoIs), and their related mechanisms. Sixty-two combat casualties with 115 ZoIs were identified. Thirty-four casualties in the open group sustained 56 ZoIs; 28 casualties in the enclosed group sustained 59 ZoIs. There was no statistical difference in mean ZoIs per casualty between groups (p = 0.54). There was a higher proportion of lower limb injuries in the enclosed group compared with the open group (p < 0.05). Of the casualties in the open group, 1 ZoI was owing to the primary effects of blast, 10 owing to a combination of primary and secondary blast effects, 23 owing to secondary blast effects and 24 owing to tertiary blast effects. In contrast, tertiary blast effects predominated in the enclosed group, accounting for 96 per cent of ZoIs. These data clearly demonstrate two distinct injury groups based upon the casualties'' environment. The enclosed environment appears to attenuate the primary and secondary effects of the explosion. However, tertiary blast effects were the predominant mechanism of injury, with severe axial loading to the lower extremity being a characteristic of the fractures seen. The development of future mitigation strategies must focus on reducing all explosion-related injury mechanisms. Integral to this process is an urgent requirement to better understand the behaviour of bone in this unique environment.     

A Novel Approach for the Synthesis and Characterization Studies of Mn 2 + -Doped CdS Nanocrystals by a Facile Microwave-Assisted Combustion Method

A simple and efficient microwave-assisted combustion method was developed to synthesize Mn ²⁺-doped CdS (Mn _x Cd _1?xS: x= 0.0, 0.3, and 0.5) nanocrystallites. The study suggested that the application of microwave heating produced spherical shaped cluster of pure and Mn ²⁺-doped CdS nanocrystallites, which was achieved in few minutes. The effects of Mn ²⁺-doping on structural, morphological, optical and magnetic properties of CdS nanocrystallites were investigated by powder X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), high-resolution scanning electron microscopy (HR-SEM) with energy dispersive X-ray analysis (EDX), high-resolution transmission electron microscopy (HR-TEM) with selected area electron diffraction (SAED), UV-Visible diffuse reflectance spectroscopy (DRS), photoluminescence (PL) spectroscopy, and vibrating sample magnetometer (VSM). The XRD results confirmed the formation of hexagonal CdS. The formation of pure and Mn ²⁺-doped CdS phase was also confirmed by FT-IR and EDX. The formation of spherical shaped cluster of nanocrystallites was confirmed by HR-SEM and HR-TEM. The as-synthesized nanocrystallites were found to have good optoelectronic properties that were determined by DRS and PL spectra. VSM results of the as-synthesized Mn ²⁺-doped CdS nanocrystallites showed ferromagnetic behavior. Graphical Abstract

A simple and rapid microwave-assisted combustion method was developed to synthesize pure and Mn²⁺-doped CdS-nanocrystallites. The formation of spherical shaped cluster of nano-crystallites was confirmed by HR-SEM and HR-TEM. The optical properties were determined by DRS and PL spectra. Magnetic properties were analyzed by VSM.     

A simple method for the extraction of the isocoumarin 6-methoxymellein from carrot tissues

The use of boiling water for the extraction of 6-mcthoxymellein, a phytoalexin of carrot, was investigated instead of the conventional organic solvent method. The recovery (118%) obtained by a two-step extraction with boiling water compared favourably with that obtained by the conventional two-step extraction with acetone.     

Short communication: rearrangement of rumenic Acid in ruminant fats: a marker of thermal treatment

Rumenic (cis-9,trans-11 18:2) acid is the main conjugated linoleic acid (CLA) isomer in milk and other ruminant fats. Anhydrous regular and high-CLA butterfats were heated at 200 degrees C for 2, 4, and 6 h under atmospheric conditions. [1,5] Sigmatropic isomerization of rumenic acid occurred, resulting in the formation of trans-8,cis-10 18:2 acid, as determined by mass spectrometry of its 4,4-dimethyloxazoline derivative. Rate of isomerization was monitored by gas-liquid chromatography, using a 120-m capillary column coated with 70% equivalent cyanoalkylpolysiloxane polymer, and reaction was of first order. Furthermore, [1,5] sigmatropic rearrangement product analysis can be used as an indicator of heat treatment of natural fats and oils containing CLA.     

Photochemical Treatment to Improve Storability of Fresh Strawberries

We investigated the effect of pre-storage exposure to shortwave ultra-violet (UV-C) light on the decay and quality of fresh strawberries. Fresh strawberries (cv. Kent, 25% to 50% red) were exposed to UV-C at doses of 0.25 and 1.0 kJ/m² and stored at 4 °C or 13 °C. UV treatment controlled the decay caused by Botrytis cinerea at both temperatures and extended the shelf-life of the fruits by 4 to 5 d. UV-treated fruits had a lower respiration rate, higher titratable acidity and anthocyanin content, and were firmer than the untreated fruits. The percentage of free sugars increased faster in UV-treated fruits at the beginning of the storage period. A lower electrical conductivity in fruits treated with 0.25 kJ/m² suggests a slower rate of senescence compared to the control. A higher electrical conductivity observed with 1.0 kJ/m²suggests damage to the fruits. Overall, UV treatment at 0.25 kJ/m² appears to slow down the ripening and senescence of strawberry fruits stored at 4 °C.     

Infinite arrays and infinite computations

A complete metric topology is introduced on the set of all finite and infinite arrays and the topological properties of the space are studied. In this complete metric topology, infinite arrays are the limits of increasing sequences of finite arrays. The notion of successful infinite derivations in Generalized Context-free Kolam Array Grammars, yielding infinite arrays, is a subclass of Generalized context-free kolam array grammars. For this class, the finite array language generated by a reduced grammar in Greibach normal form and the set of infinite arrays generated by it are related through the notion of adherence.     

An efficient fault-tolerant approach for Mobile IP in wireless systems

This paper presents the fault tolerance of Mobile IP in wireless systems. Mobile IP can support wireless users with continuous network connections while changing locations. It is achieved by allocating a number of mobility agents (foreign agents and home agents) in the architecture of a wireless system. If a failure occurs in a mobility agent, the wireless users located in the coverage area of the faulty mobility agent will lose their network connections. To tolerate the failures of mobility agents, this paper proposes an efficient approach to maintaining the network connections of wireless users without being affected by the failures. Once detecting a failure in a mobility agent, failure-free mobility agents are dynamically selected to be organized as a backup set to take over the faulty mobility agent. Compared to the previous approaches, the proposed approach does not take any actions against failures during the failure-free period. Besides, the hardware redundancy technique is also not used in the proposed approach. The overhead of the proposed approach is analyzed using the M/G/c/c queuing model. The results show that the proposed approach can effectively resolve the fault-tolerant problem of Mobile IP in wireless systems.