Contribution of dynamic charging effects into dopant contrast mechanisms in silicon

In this work, SEM capability for imaging of both p- and n-doped regions in Si was demonstrated. The best dopant contrast was found when the primary electron range (R) is comparable or larger than the maximum escape depth of secondary electrons (∼5λ) (λ stands for mean free path). Beyond this scale (R < 5λ, R > > 5λ) the contrast between p-, n-doped and intrinsic regions gradually disappears. The dopant profiles obtained by SEM were judged using scanning capacitance microscopy (SCM), dopant selective etch (DSE) and secondary ion mass spectrometry (SIMS) measurements, and excellent matching was demonstrated. A novel dopant contrast mechanism incorporating dynamic charging effects that take place during e-beam/specimen interaction is suggested. Under threshold steady-state imaging conditions, an E _bi field in Si near the surface region is formed. This field, governed by secondary electron (SE) emission and trapping of some incident and generated SE, accelerates electrons towards the surface in p-type regions and decelerates them in n-type regions, compared with the intrinsic material. This results in the observed dopant contrast: C(n) < C(i) < C(p). Use of the SEM for 2D-dopant imaging provides many advantages; giving fast results, covering a wide range of dopant concentrations, applicable to real devices, and does not require sample preparation needed by SCM and DSE. In addition, SEM-dopant contrast data quantification is possible using SIMS standards which needs to be defined with more details.     

Steering Requisites for Crises-Opportunities: On-Going Challenges

That man most luckily forms his plan, among all the persons in Fortune's palace, who chooses a wheel befitting her wish (Machiavelli, quoted in Gilbert, 1989: 747).     

Sulfamethoxazole contamination of a deep phreatic aquifer

Groundwater samples were obtained from the water table region of a phreatic aquifer (unsaturated zone depth up to 28 m) under land irrigated with wastewater effluents for about 5 decades and a relatively deep pumping well (109 m), used as a drinking water source till 2007, located downstream (1300 m) of wastewater effluent and sludge infiltration facilities. Sulfamethoxazole (SMX) concentrations in secondary effluents varied between 90 and 150 ng/L. SMX was extracted using SPE and was analyzed by HPLC-MS/MS. SMX (maximum concentration of 37 ng/L) was detected in the water table region, in two monitoring wells, after an unsaturated zone transport period of about 16 years. The maximum SMX concentration detected in the pumping well was of 20 ng/L. These results question wastewater effluent disposal strategies including the suitability of irrigation with effluents on the replenishment area of an aquifer supplying drinking water.     

A Gel‐Based Model of Selective Cell Motility: Implications for Cell Sorting,Diagnostics, and Screening

The ability to precisely control cell‐loaded material systems is essential for in vitro testing of novel therapeutics poised to advance to clinic. In this report, unique patterns of cell migration are devised into an in vitro gel‐in‐gel model for the purpose of obtaining cell response data to potentially therapeutic chemical agonists. The model consists of co‐cultures in a cell‐loaded microgel invading an acellular “sorting” gel. Material properties including biophysical and chemical compositions of the sorting gel are carefully controlled to guide a desired cell‐specific behavior, leading to massive tumor cell invasion by amoeboid migration mechanisms. Optical transparency enables straightforward and high‐throughput measurements of outgrowth response in the presence of either chemical and photoradiation therapy. Important dosing and drug sensitivity information are obtained with the gel‐in‐gel model using no more than a light microscope, without further need for arduous genomic or proteomic screening of the tissue samples.     

Influence of fluorescence anisotropy on fluorescence intensity and lifetime measurement: theory, simulations and experiments

The significance of fluorescence anisotropy in fluorescence intensity and lifetime measurements, and erroneous measurements and interpretations resulting from its disregard, are thoroughly discussed, formulated and quantified. In all fluorescence-related measurements--including excitation and emission spectra, relative fluorescence intensity (FI), fluorescenc life time (FLT), fluorescence resonance energy transfer (FRET), etc., with the exception of fluorescence polarization and anisotropy--it is generally true that the higher the fluorescence anisotropy, the greater the distortion of fluorescence measurements. Quantifiable distortions occur when fluorescence measurements are conducted without considering the influence of fluorescence anisotropy. Here, this influence is described by numerous newly developed mathematical expressions which are simulated and experimentally confirmed utilizing single and binary fluorescent solutions of fluorophores with different spectroscopic characteristics. A marked agreement is shown between the theory and experimental data, clearly indicating the legitimacy of the physical suppositions and the mathematical expressions presented in this paper. Practical and instructive implications are discussed. The following findings are of special applicative importance: 1) the existence of an infinite number of couples of Magic Angles; 2) the deviation between two equally fluorescing particles having different fluorescence anisotropies; 3) the relation between the detected fluorescence intensity and anisotropy when measured under various setups of emission and excitation polarizers; 4) the dependence of the artificial normalized steady-state weight of a single-exponentially decaying fluorophore on its fluorescence anisotropy.     

Encapsulation of bacteria and viruses in electrospun nanofibres

Bacteria and viruses were encapsulated in electrospun polymer nanofibres. The bacteria and viruses were suspended in a solution of poly(vinyl alcohol) (PVA) in water and subjected to an electrostatic field of the order of 1?kV?cm(-1). Encapsulated bacteria in this work, (Escherichia coli, Staphylococcus albus) and bacterial viruses (T7, T4, λ) managed to survive the electrospinning process while maintaining their viability at fairly high levels. Subsequently the bacteria and viruses remain viable during three months at -20 and -55?°C without a further decrease in number. The present results demonstrate the potential of the electrospinning process for the encapsulation and immobilization of living biological material.     

Fast randomized algorithm for 2-hops clustering in vehicular ad-hoc networks

Vehicular Ad-Hoc Networks (VANETs) enable inter vehicle wireless communication as well as communication with road side equipment. Warning messages can be exchanged among nearby vehicles, helping to predict dangerous situations, and thus improving road safety. Such safety messages require fast delivery and minimal delay to local areas, in order for them to be effective. Therefore, a fast and efficient channel access scheme is required. A feasible solution, derived from the Mobile Ad-Hoc Networks (MANETs) field, groups nodes into smaller manageable sections called clusters. Such an approach can be beneficial for locally delivering messages under strict time constraints. In this paper, a Hierarchical Clustering Algorithm (HCA) is presented. HCA is a distributed randomized algorithm, which manages channel access by forming three hierarchy clusters. The proposed channel access scheme enables delay bounded reliable communication. Unlike other common clustering algorithm for VANETs, HCA does not require the knowledge of the vehicles’ locations. This feature guarantees accurate operation even when localization systems such as GPS are not available. The running time and message complexity were analyzed and simulated. Simulation results show that the algorithm behaves well especially under realistic mobility patterns; therefore, it is a suitable solution for channel access scheme for VANETs.     

Sequencing, Scheduling and Tooling Single-Stage Multifunctional Machines in a Small Batch Environment

Single-Stage multifunctional Machining Systems (SSMSs) are an important integral part of automated, flexible manufacturing systems. However, the SSMS frequently becomes the bottleneck of the entire manufacturing system by virtue of protracted internal set-up requirements. A key aspect of achieving full SSMS utilization is the ability to reduce as much as possible these demands at the expense of increasing external set-up. As of today, fixturing devices have not received much attention in the modeling literature. Nevertheless, fixturing devices are in some cases a limited resource which, may affect the shop scheduling decisions and the shop performance and as such can not be omitted. This study presents a {0–1} programming model which takes the fixturing device's limitation in to consideration when determining the weekly sequence of jobs to be produced. The model tries to minimize the non-productive machine time. Based on this model, a heuristic procedure is developed and tested using data of four production weeks obtained from a hi-tech company that produces medical imaging systems.     

Effect of acid dissolution on the mineral matrix and organic matter of Zefa EFE oil shale

Kerogen of the Israeli Zefa oil shale was isolated and the changes which occur in the initial organic matter during the removal of the inorganic matrix were investigated. Benzene-methanol extraction dissolved the bitumens, hydrochloric acid and hydrofluoric acid dissolution removed the carbonate and silicate minerals and lithium aluminium hydride treatment destroyed pyrite mineral which was unaffected by the attack of acids. X-ray diffractograms and FTIR spectra of the original oil shale and its demineralized products were measured. Benzene-methanol extraction of the oil shale increased the resolution of peaks in the X-ray diffractograms X-ray diffractograms and FTIR spectra indicated the presence of calcite, α-quartz, kaolinite, illite and pyrite in the mineral matrix of the shale. Hydrochloric and hydrofluoric acid dissolution did not cause hydrolysis and oxidation of the organic matter. Lithium aluminium hydride treatment reduced the carbonyl functionalities to newly formed hydroxyl groups, therefore the kerogen isolated seemed to have a chemical composition different from that of the original oil shale.