DEVELOPMENT OF OPACITY IN ZIRCONIA ENAMELS*

Opaque zirconia-bearing enamels are divided into two general types, namely, those whose opacity is due (1) to the undissolved residue of the zirconia added in the raw batch and (2) to the crystallization of a zirconia compound during firing. These enamels are described and illustrated. The quantity, identity, and appearance of the materials causing opacity in representative samples of each group of enamels are given.     

Potential regulation by trophic factors of low-affinity NGF receptors in spinal motor neurons

Developing spinal motor neurons (SMN) express low-affinity nerve growth factor receptors (LNGFR) but not high-affinity transducing NGF receptors. Moreover, SMN are not supported by NGF in vitro. In the normal adult rat most SMN are not LNGFR immunoreactive (LNGFR-IR), but they transiently reexpress LNGFR (though not the high-affinity receptor) after peripheral nerve injury. With a cut lesion of the sciatic nerve (when only a neuroma forms), the number of LNGFR-IR SMN at L4-L6 rapidly increases to a maximum between day 1 and 7 and returns to baseline levels by day 30. After a crush lesion (accompanied by regeneration to the muscle), LNGFR-IR SMN appear in about the same numbers, but they start to disappear 1 week later. We speculate that the similar appearance and differential decline of LNGFR-IR seen after the two types of lesions are regulated by the availability of a common signal such as ciliary neurotrophic factor. The adult SMN model provides a good opportunity to investigate the reexpression of LNGFR after peripheral nerve injury, and more generally, the unknown role and regulation of LNGFR.     

In-situ plasma cleaning of stainless steel III-V MOCVD growth systems

A plasma enhanced, in-situ, dry etching process for the cleaning of stainless steel III-V Metal Organic Chemical Vapor Deposition growth systems was investigated as a function of etchant gas, flow rate, electrode configuration, power density and plasma frequency. The plasma enhanced etching process was investigated using Ar, CH₄ (5% in H₂), CCl₂F₂ (Freon 12)/Ar and Cl₂/Ar plasmas with flows varying from 5 to 25 seem. The plasma was excited using three electrode configurations, and two radio frequency generators (90–460 KHz and 13.56 MHz), singly and in combination. The plasma power was varied over the range from 200 to 700 Watts (∼0.2W/cm² – 0.7W/cm²). The etching rates of GaAs, InP, As, and Mo were measured using a weight difference method. The Cl₂/Ar plasmas exhibited etching rates typically 5 to 10 times greater than that of CCl₂F₂ plasmas, which in turn is several times greater than that of the other etchant gases investigated. At 400 W, elemental As etch rates, as high as ∼180μm/hr and ∼20μm/hr were achieved using Cl₂ and CCl₂F₂ plasmas, respectively. InP/GaAs etch rates using Cl₂ were ∼30μm/hr and using CCl₂F₂ were ∼7μm/hr. Plasma characteristics and etch rate measurements are reported. The in-situ process investigated is a safe, cost effective and an efficient method for increasing reactor uptime.     

Romantic involvement often reduces men's testosterone levels--but not always: The moderating role of extrapair sexual interest.

Testosterone (T) appears to facilitate what biologists refer to as mating effort--the investment of time and energy into same-sex competition and mate-seeking behavior. Multiple studies show that men who are romantically involved (i.e., are paired) have lower T than single men, which may be due to a facultative adjustment by men of T levels in response to lower demands for mating effort. The authors proceeded on the basis of the idea that men who retain interests in sexual opportunities with women other than a primary partner continue to dedicate more time and energy to mating effort when romantically paired, and so they predicted that the association between relationship status and T depends on men's extrapair sexual interests. Study 1 used the Sociosexual Orientation Inventory to measure extrapair sexual interests, whereas Study 2 used a broader measure to examine this interaction. Both studies found support for it. These results have implications for an understanding of the biosocial regulation of men's behavior in romantic relationships. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The effect of dietary crude protein on growth, ammonia concentration, and litter composition in broilers

An experiment was conducted to determine the effect of diets with reduced CP and supplemental amino acids on broiler performance, N excretion, litter characteristics, and equilibrium NH3 gas concentration. Results suggest that reducing CP (and lysine) below 241 g/kg (13.7 g/kg lysine) in the diets fed during the first 3 wk may slightly increase feed:gain and therefore may not be advisable. During the period 22 to 43 d of age there were no significant differences in weight gain and BW at 6 wk of age when reducing CP from 215 g/kg (11.5 g/kg lysine) to 196 g/kg (11.3 g/kg lysine), but feed intake and feed:gain ratio increased. However, reducing CP did cause equilibrium NH3 gas concentration and litter N to decline by 31 and 16.5%, respectively. Both of these advantages will improve air quality within the housing facility and possibly reduce heating costs during winter associated with higher ventilation rates required to reduce elevated NH3 gas concentrations.     

The role of air plethysmography in the diagnosis of chronic venous insufficiency

The role of protein and cellular components of thrombi in mediating bacterial adhesion on artificial surfaces was investigated in this study. The attachment of Staphylococcus aureus on polyurethane surfaces was observed directly using an automated video microscopy system. Surfaces were preconditioned with components of platelet-fibrin thrombi, including fibrinogen, thrombin, plasma, and isolated platelets. Experiments were performed in a radial flow chamber, and attachment rate constants were compared on the preconditioned surfaces in an effort to understand the complex relationship that exists between bacterial infection and thrombosis on synthetic biomaterials. Preadsorption of fibrinogen to surfaces significantly increased S. aureus adhesion compared to those preadsorbed with albumin alone while the presence of fibrin dramatically increased bacterial attachment compared to plasma preadsorbed surfaces. While the presence of adherent platelets also increased bacterial attachment, fibrin appeared to play a larger role in mediating bacterial adhesion on polyurethane surfaces. Striking results were obtained on the zwitterionic phosphonated polyurethane for a number of pretreatment conditions with regard to decreased bacterial adhesion and fibrinogen deposition.     

Onchocerciasis

An estimated 17.7 million persons, most of them in Africa, are infected with the parasite Onchocerca volvulus. Onchocerciasis has caused blindness in 270,000 and left another 500,000 with severe visual impairment. Onchocerciasis also can cause disfiguring skin changes, musculoskeletal complaints, weight loss, changes in immune function, epilepsy, and growth arrest. The development of ivermectin and its donation by the manufacturer has reduced transmission in many parts of Africa and Latin America. Progress in developing a drug that can destroy adult worms has been slow, however. The immediate need is to extend ivermectin mass distribution to as many endemic areas as possible on a continuing basis, with steps toward community ownership of such programs. This article presents a comprehensive review of the literature on the epidemiology, parasitology, vector, symptoms, diagnosis, and treatment and control of onchocerciasis. Future research aims include fuller understanding of the parasite and its relationship with the host, the nature of the systemic effects of O. volvulus infection, the natural history of skin disease, and a better appreciation of the social and economic consequences of this parasitic disease.     

One Dimensional Scintillation Cameras for Positron Ect Ring Detectors

A one-dimensional scintillation camera configured as a continuous ring with coincidence-mode collimation avoids many of the problems associated with rings formed from an array of discrete detector elements. With the goal of achieving a stationary detector exhibiting high spatial resolution and sensitivity, several detector configurations have been designed. Both analytic and Monte-Carlo simulation techniques have been used to evaluate these designs. Results of the calculations and comparative measurements on the various detector designs are discussed.     

CW room-temperature visible single quantum well Ga0.73Al0.27As diode lasers grown by metalorganic chemical vapour deposition

Room-temperature CW laser operation at 7125 ? has been achieved in a (Ga1?xAlxAs, x?0.27) single quantum well double heterostructure (SQW-DH) diode laser. The laser consists of a 9 ?m-wide delineated shallow proton stripe. The pulsed threshold current for a 250 ?m long device is 115 mA whereas the CW threshold current is 140 mA. The CW external differential quantum efficiency is 60%.     

Analysis of grating-coupled radiation in GaAs:GaAlAs lasers and waveguides--II: Blazing effects

Grating-coupled radiation in lasers and waveguides is analyzed for trapezoidal-shaped grating teeth which includes all triangular shapes. A perturbation technique is used which involves calculating the modes in a geometry with an inhomogeneous refractive index profile in the grating region. Curves are presented for radiated power from traveling waves as a function of blazing angle, grating tooth height, refractive index, and grating period. It is shown that the ratio of power radiated into the outer media depends greatly on tooth shape and size. By judiciously selecting parameters this ratio can exceed 50:1.