Technical Note

Some Remarks on the Meaning of Isoelectric Point of Glycine

One of the most important characteristics of proteins, their components aminoacids, colloids and minerals is the so-called isoelectric point (IEP).
 

 English Articles

Morphological Characterization of Eutectic Si and Ge Phases in the Corresponding Al-15Si and Al-20Ge Alloys Using FIB Tomography

The three-dimensional morphology of the eutectic Ge phase in samples modified by Ca and Y in the hypoeutectic Al-20Ge alloy has been investigated by focused ion beam tomography. Addition of Ca (0.2 wt.%) caused a modification of the eutectic Ge phase from a branched plate-like morphology to a compressed cylinder-like shape of smaller dimensions. Addition of Y (0.2 wt.%) resulted in a transformation of the eutectic Ge phase with two types of morphology. One type is vermicular-like in 2D and refined plate-like in 3D, while the other appears as a holey Ge matrix with an embedded eutectic Al phase of rod-like morphology. The morphology of the modified eutectic Ge has been discussed in terms of possible growth mechanisms compared with that of the as-cast non-modified Al-20Ge alloy and that of well-known Sr-modified eutectic Si in Al-Si system.

Field Electron Emission from Pyrograf Ш PR-1 Carbon Nanotube Fibers Embedded in Glass

This study investigates the field electron emission properties of Pyrograf-Ш carbon nanotube fibers (CNTFs). Field emitters were manufactured by employing a drawing technique using a glass puller. A field electron microscope with a tip (cathode) to screen (anode) separation of approximately 10 mm was used to characterize the emitters. The current-voltage (I-V) characteristics of the CNTFs showed a shallow increase in the emitted current with increasing applied voltage, until a threshold voltage (VTH) is reached, after which a “switch-on” phenomenon occurs. The I-V characteristics are then linear. Fowler-Nordheim plots and field electron emission patterns are also discussed and it is shown that it is possible to get a single bright emission spot.

M. S. Mousa,           M.-A. H. Al-Akhras and S. I. Daradkeh
 

Neutron-Induced Reactions in Nuclear Astrophysics

AThe quest for the origin of the chemical elements, which we find in our body, in our planet (Earth), in our star (Sun) or in our galaxy (Milky Way), could only be resolved with a thorough understanding of the nuclear physics properties of stable and unstable atomic nuclei. While the elements until iron are either created during the big bang or during fusion reactions in stars, most of the elements heavier than iron are produced via neutron-induced reactions. Therefore, neutron capture cross-sections of stable and unstable isotopes are important. ...

Modeling the Electrical Impedance of Epoxy Polymer/Carbon Black Composite Materials

The effect of filler aspect ratio on the dielectric properties of epoxy resin reinforced with carbon black (CB) is here investigated. The composites change from an electrical insulator to a conductor as the CB content is increased from 1.5% to 4.5%, which is called the percolation region. Complex impedance spectra and Bode diagrams of these composites were carefully analyzed and the corresponding equivalent circuits (EC) under different concentrations of CB were also provided. Furthermore, the correlation between the shape of Bode diagrams and the equivalent circuits was discussed. Finally, the Cole–Cole representation was used to interpret the impedance spectra of all the samples.

Z. Samir,

R. Belhimria,

S. Boukheir,

M. E. Achour and

L. C. Costa

Advancing Nuclear Astrophysics Using Next-Generation Facilities and Devices

Where are all the heavy elements formed? How are they formed? What is the role played by stars and stellar explosions?
Nuclear astrophysics aims at answering these fundamental scientific questions by linking nuclear physics with astrophysical modelling and observations. Large progress has been achieved in past decades. However, new nuclear physics facilities and devices are urgently required to advance research into regions of the nuclear chart so far not reachable. This will enable unprecedented studies of nuclear reactions in the laboratories, which are key for heavy element synthesis and the fate of a star. Some highlights of upgrade-in-process will be described. ...

C. Langer,

N. Klapper,

C. Köppchen,

S. Dababneh  and

R. Reifarth

Characterization of Composite Electron Sources (Metal - Insulator - Vacuum)
 

Field electron emission measurements were performed on composite tips (Insulator- Tungsten) that were prepared by electrochemical etching in NaOH solution. The current-voltage (I-V) characteristics and field electron emission images were recorded under UHV conditions with a base pressure of <10^-9 mbar. Next, the tips were coated with several different types of dielectric layers. Various techniques were employed to measure the characteristics of these types of emitters and to evaluate the effects of different types of dielectric coatings on the performance and reliability of such an electron source.

A. M. Al-Qudah,

S. S. Alnawasreh,

M. A. Madanat,

O. Trzaska,

D. Matykiewicz,

S. S. Alrawshdeh,

M. J. Hagmann    and M. S. Mousa

 JJP, 2018, 11(1), 59-68

Equations of Motion for Ideal Hydrodynamics in Rotating Frame Using Caputo's Definition

In this paper, we describe the motion of ideal hydrodynamics in a rotating frame by the equations of motion using Caputo's fractional derivative. Then, from the fractional Euler-Lagrangian equation, we obtain the equations that describe the motion of ideal fluid in fractional form, the Hamiltonian density and the energy-stress tensor obtained in fractional form from the fluid Lagrangian density. Finally, from the Hamiltonian density, we also find the Hamiltonian equations of motion for the ideal fluid in fractional form.

Emad K. Jaradat   and Rabea'h A. Al-Fuqaha