Microwave device investigations Semiannual progress report, 1 Oct. 1969 - 1 Apr. 1970

Beam-plasma interactions, cyclotron harmonic instability study, and millimeter and submillimeter wave detection by paramagnetic material

Microwave device investigations Semiannual progress report, 1 Apr. - 1 Oct. 1969

Summaries of progress in beam plasma interactions, paramagnetic and bulk semiconductor materials, and avalanche diode

Microwave device investigations Semiannual progress report, 1 Oct. 1968 - 1 Apr. 1969

Beam plasma amplification, harmonic generation, and coupling scheme

Alignment in total knee arthroplasty : what’s in a name?

Dissatisfaction following total knee arthroplasty is a well-documented phenomenon. Although many factors have been implicated, including modifiable and nonmodifiable patient factors, emphasis over the past decade has been on implant alignment and stability as both a cause of, and a solution to, this problem. Several alignment targets have evolved with a proliferation of techniques following the introduction of computer and robotic-assisted surgery. Mechanical alignment targets may achieve mechanically-sound alignment while ignoring the soft tissue envelope; kinematic alignment respects the soft tissue envelope while ignoring the mechanical environment. Functional alignment is proposed as a hybrid technique to allow mechanically-sound, soft tissue-friendly alignment targets to be identified and achieved

Microwave device investigations Semiannual progress report, 1 Apr. - 1 Oct. 1968

Beam-plasma interactions, cyclotron harmonic instabilities, harmonic generation in beam-plasma system, relativistic electron beam studies, and materials test

Frequency multiplication in high-energy electron beams Semiannual progress report, 1 Oct. 1967 - 31 Mar. 1968

Electron beam-plasma interactions, cyclotron harmonic instabilities, paramagnetic and semiconductor materials, and harmonic current generatio

Detection of vibronic bands of C3_3 in a translucent cloud towards HD 169454

We report the detection of eight vibronic bands of C$_3$, seven of which have been hitherto unobserved in astrophysical objects, in the translucent cloud towards HD~169454. Four of these bands are also found towards two additional objects: HD~73882 and HD~154368. Very high signal-to-noise ratio ($\sim$1000 and higher) and high resolving power ($R=80,000$) UVES-VLT spectra (Paranal, Chile) allow for detecting novel spectral features of C$_3$, even revealing weak perturbed features in the strongest bands. The work presented here provides the most complete spectroscopic survey of the so far largest carbon chain detected in translucent interstellar clouds. High-quality laboratory spectra of C$_3$ are measured using cavity ring-down absorption spectroscopy in a supersonically expanding hydrocarbon plasma, to support the analysis of the identified bands towards HD~169454. A column density of N(C$_3$) = $(6.6 \pm 0.2) \times 10^{12}$ cm$^{-2}$ is inferred and the excitation of the molecule exhibits two temperature components; $T_{exc}= 22 \pm 1$ K for the low-$J$ states and $T_{exc}= 187 \pm 25$ K for the high-$J$ tail. The rotational excitation of C$_3$ is reasonably well explained by models involving a mechanism including inelastic collisions, formation and destruction of the molecule, and radiative pumping in the far-infrared. These models yield gas kinetic temperatures comparable to those found for $T_{exc}$. The assignment of spectral features in the UV-blue range 3793-4054 \AA\ may be of relevance for future studies aiming at unravelling spectra to identify interstellar molecules associated with the diffuse interstellar bands (DIBs).Comment: 15 pages, 13 figures, submitted to MNRA

Deteriorated Concrete Foundation on the Gulf Coast

An investigation into the deteriorated condition of a concrete mat foundation under saline water table on a coastal sabkha sand in Qatar, the Arabian Gulf coast, was undertaken. The investigation aided by visual examination, testing (destructive and non-destructive), analysis and consideration of different soil-structure interaction schemes resulted in re-approval of the foundation from a structural integrity point of view; however its water tightness role was judged inadequate and required remedial works. Options for repair of the foundation were examined and proposed. To safeguard against the adverse effects of salts on foundation concrete, appropriate design and construction measures are required

Superlattice barrier varactors

SBV (Single Barrier Varactor) diodes have been proposed as alternatives to Schottky barrier diodes for harmonic multiplier applications. However, these show a higher current than expected. The excess current is due to X valley transport in the barrier. We present experimental results showing that the use of a superlattice barrier and doping spikes in the GaAs depletion regions on either side of the barrier can reduce the excess current and improve the control of the capacitance vs. voltage characteristic. The experimental results consist of data taken from two types of device structures. The first test structure was used to study the performance of AlAs/GaAs superlattice barriers. The wafer was fabricated into 90 micron diameter mesa diodes and the resulting current vs. voltage characteristics were measured. A 10 period superlattice structure with a total thickness of approximately 400 A worked well as an electron barrier. The structure had a current density of about one A/sq cm at one volt at room temperature. The capacitance variation of these structures was small because of the design of the GaAs cladding layers. The second test structure was used to study cladding layer designs. These wafers were InGaAs and InAlAs layers lattice matched to an InP substrate. The layers have n(+) doping spikes near the barrier to increase the zero bias capacitance and control the shape of the capacitance vs. voltage characteristic. These structures have a capacitance ratio of 5:1 and an abrupt change from maximum to minimum capacitance. The measurements were made at 80 K. Based on the information obtained from these two structures, we have designed a structure that combines the low current density barrier with the improved cladding layers. The capacitance and current-voltage characteristics from this structure are presented

Bouveret\u27s Syndrome: Literature Review.

It was in 1896 that Bouveret\u27s syndrome acquired its name after the French physician Leon Bouveret, who published two case reports in Revue de Medecin. Bouveret\u27s syndrome describes gastric outlet obstruction secondary to an impacted gallstone. The gallstone reaches the small bowel through a bilioenteric fistula as a consequence of chronic inflammation and adherence between the biliary system and the bowels which increase the intraluminal pressure and leads to secondary wall ischemia and wall perforation with gallstone passage into the bowel. Bouveret\u27s syndrome\u27s prevalence is highest among elderly women. Despite the rarity of Bouveret\u27s syndrome, it can cause notable morbidity and mortality rates. We underwent a review of literature about Bouveret syndrome to increase awareness of its occurrence and potentially life-threatening complications