Spectral polarization measurements by use of the grating division-of-amplitude photopolarimeter

The grating division-of-amplitude photopolarimeter (G-DOAP) is an instrument that exploits the multiple-beam-splitting, polarizing, and dispersive properties of diffraction gratings for the time-resolved measurement of the complete state of polarization of collimated broadband incident light, as represented by the four Stokes parameters as a function of wavelength across the spectrum. It is a compact, high-speed sensor that has no moving parts and is simple to install and operate. These characteristics make the G-DOAP well suited for in situ spectroscopic ellipsometry (SE) applications for monitoring and controlling thin-film processes. The design and performance of a prototype instrument are presented. Precise SE measurements, to +/-0.04 degrees in psi and +/-0.1 degrees in delta, are demonstrated in the 550-940-nm wavelength range.     

Fabrication of a surface plasmon resonance biosensor based on gold nanoparticles chemisorbed onto a 1,10-decanedithiol self-assembled monolayer

We have investigated the fabrication of surface plasmon resonance (SPR) biosensors using self-assembled monolayers (SAMs) and adsorbed gold nanoparticles. The SAM of 1,10-decanedithiol was first fabricated onto a gold substrate. Gold nanoparticles were then chemisorbed onto the SAM surface by bonding with the terminal thiol groups, forming a sensor that can be used to immobilize proteins. Bovine serum albumin (BSA) was used as a test protein in this study. Several spectroscopic and microscopic techniques were used to investigate both the SAM and the chemisorption of gold nanoparticles at the SAM surface. Our results confirm the covalent bonding of the gold nanoparticles onto the SAM. Surface plasmon resonance (SPR) was used to study both the adsorption of BSA to the SAM surface and to the gold nanoparticle-coated SAM. For SAM surfaces with adsorbed gold nanoparticles a larger SPR response to BSA than to the sensors with a bare SAM is observed.     

The improvements of three-dimensional seismic interpretation in comparison with the two-dimensional seismic interpretation in Al-Amal oil field,Gulf of Suez,Egypt

Thirteen 2D seismic lines were interpreted with the help of well velocity and time-depth trace conversion to construct the structure-tectonic maps. This is to characterize the different stratigraphic tops of Al-Amal area, as well as to confirm the validity of the proposed structural model. Most of the available seismic data in Al-Amal area were investigated and reviewed to select the best quality set.In order to study the detailed structural elements based on the 3D seismic lines; six depth structure contour maps were constructed on the tops of Zeit, South Gharib, Belayim, Kareem, Nukhul and Matulla formations from top downward. Interpretation was aided by the missing sections detected from the available well tops and dip-meter data as well. These maps indicate that, both of Miocene and Pre-Miocene formations in Al-Amal field were affected by elongated tilted graben blocks trending in the NW–SE directions and bounded by two sets of faults, which are down throwing toward the west and eastern directions.     

Strength of soil reinforced with fiber materials (Papyrus)

Construction of building and other civil engineering structures on weak or soft soil is highly risky because such soil is susceptible to differential settlements, poor shear strength, and high compressibility. Various soil improvement techniques have been used to enhance the engineering properties of soil. Soil reinforcement by fiber material is considered an effective ground improvement method because of its cost effectiveness, easy adaptability, and reproducibility. Hence, in the present investigation, papyrus fiber has been chosen as the reinforcement material, and it was randomly included into the soil at four different percentages of fiber content, i.e., 5, 10, 15, 25% by volume of raw soil. The main objective of this research is to focus on the strength behavior of soil reinforced with randomly included papyrus fiber. Direct shear, consolidation, and displacement tests were performed on papyrusreinforced specimens with various fiber contents. The results of these tests have clearly shown a significant improvement in the failure deviator stress and shear strength parameters (c and φ) of the studied soil with a percent addition of 10% (the preferred percent). Moreover, this addition ratio reduced the displacement of the soil under loading. It can be concluded that papyrus fiber can be considered an appropriate soil reinforcement material.     

The Influence of the Dielectric Constant and Electrolyte Concentration of the Pore Fluids on the Undrained Shear Strength of Smectite

It is common knowledge that the engineering properties of clays are greatly influenced by the type of pore fluids. However, the impact of the pore fluids on the geotechnical properties of the samples is even more dependent on the type of mineral and interlayer ions. Completely different behaviours could be observed with identical pore fluids but different clay minerals and vice versa. The liquid limit, plastic limit and undrained shear strength were determined for two types of smectites with different interlayer cations, namely Ca and Na-smectite. The pore fluids were varied by using different dielectric constants (ε) and electrolyte concentrations (n₀). The results show that the two kinds of soils respond in a similar way but with a different magnitude depending on the ion occupation.     

The plastic zones and displacements around underground openings in rock masses containing a fault

Faults are the commonly encountered large geological discontinuities in hard rock masses, most severe underground structure instability is found to be closely associated with the faults presence nearby. The parametric study carried out in this paper using numerical method (UDEC) has identified some fault parameters to be really critical for the underground structure stability. These fault parameters are fault dips, fault shear strength and fault locations relative to the underground structure. This numerical investigation revealed that faults affect the stability of underground structure by the tendency of increasing the plastic zones, displacements and causing both asymmetrically distributed in the rock masses adjacent to the excavation. The relationship of the induced plastic zones, maximum displacements varying with these fault parameters was established. The distribution of plastic zone and displacement was graphically presented and the mechanisms such effects were discussed. These results offer a guideline in support design.     

Financing of health in Lebanon. II. Financing sources and global expenses for health

The use of fluorinated quinolones for prophylaxis of infections in neutropenic cancer patients has led to a reduction of infections with gram-negative enteric bacilli, but there is concern about the emergence of antibiotic-resistant entero-bacterial infections and a rise of gram-positive bacteremias. Due to these concerns, in mid-1995 the use of prophylactic norfloxacin was discontinued in our unit. In order to evaluate the impact of this measure on the infectious morbidity in our unit, 91 severe neutropenic episodes in 58 patients with hematologic malignancies who did not receive norfloxacin prophylaxis (NO group) were closely matched to 91 episodes in 60 patients who received norfloxacin prophylaxis (NORFLO group). There were no differences in the incidence of febrile neutropenia, fever of unknown origin or bacteremia during the first febrile episode. There was a trend for a higher rate of coagulase-negative staphylococcal bacteremia in the NORFLO group (5 vs. 11 cases in the NO and NORFLO groups, respectively, p = NS). Enterobacterial bloodstream infections were more frequent in the NO group (13 vs. 2 cases, respectively, p = 0.01), especially Escherichia coli (9 vs. 1 case, respectively, p = 0.01). Twelve of 13 enterobacterial isolates in the NO group were sensitive to the fluoroquinolones vs. 0/2 in the NORFLO group (p = 0.07). We conclude that the abrupt discontinuation of norfloxacin prophylaxis in our ward led to a rapid increase in the rate of fluoroquinolone-susceptible enterobacterial infections, with a scarce impact on infectious morbidity. This suggests that the selection of resistant flora in an inpatient ward by prophylactic antimicrobials may be reversible following the discontinuation of the prophylactic agent(s).     

Polarization-independent Beam Splitter Based on Light Reflection by a Uniaxial Crystal Surface,and an Immersion Method for Determining the Crystal's Principal Refractive Indices

Abstract

Light travelling in an isotropic medium of refractive index n and incident on a uniaxial crystal whose optic axis is parallel to the surface and to the plane of incidence is reflected without a change of polarization when n = N _g = (N _o N _e)^1/2, where N _o and N _e are the crystal's ordinary and extraordinary refractive indices. This is true for all incident polarization states and at all angles of incidence and can be used to design a new polarization-independent beam splitter. For a positive uniaxial crystal (N _e > N _o), total internal reflection occurs at and above a critical angle equal to arcsin (N _o/N _e)^1/2, so that the incident light beam is deflected without attenuation or change of polarization. When n = N _g the reflectance at normal incidence for unpolarized or circularly polarized incident light is a minimum: R _0min = (N_a - N_g)/(N_a + N_g), where N _a = ½(N _o + N _e). This suggests a liquid immersion method in which n and R _0min determine N _g and N _a, hence N _o and N _e of the crystal.     

Optimal beam splitters for the division-of-amplitude photopolarimeter

Optimal optical parameters of the beam splitter that is used in the division-of-amplitude photopolarimeter are determined. These are (1) 50%-50% split ratio of the all-dielectric beam splitter, (2) differential phase shifts in reflection and transmission delta(r) and delta(t) that differ by +/- pi/2, and (3) ellipsometric parameters (psi(r), psi(t)) = (27.368 degrees, 62.632 degrees) or (62.632 degrees, 27.368 degrees). It is also shown that for any nonabsorbing beam splitter that splits incident unpolarized light equally, the relationship psi(r) + psi(t) = pi/2 is always satisfied.