Luminance Degradation Research Articles

Glucose-Induced Incretin Hormone Release and Inactivation Are Differently Modulated by Oral Fat and Protein in Mice

Monounsaturated fatty acids, such as oleic acid (OA), and certain milk proteins, especially whey protein (WP), have insulinotropic effects and can reduce postprandial glycemia. This effect may involve the incretin hormones glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1). To explore this, we examined the release and inactivation of GIP and GLP-1 after administration of glucose with or without OA or WP through gastric gavage in anesthetized C57BL/6J mice. Insulin responses to glucose (75 mg) were 3-fold augmented by addition of WP (75 mg; P < 0.01), which was associated with enhanced oral glucose tolerance (P < 0.01). The insulin response to glucose was also augmented by addition of OA (34 mg; P < 0.05) although only 1.5-fold and with no associated increase in glucose elimination. The slope of the glucose-insulin curve was increased by OA (1.7-fold; P < 0.05) and by WP (4-fold; P < 0.01) compared with glucose alone, suggesting potentiation of glucose-stimulated insulin release. WP increased GLP-1 secretion (P < 0.01), whereas GIP secretion was unaffected. OA did not affect GIP or GLP-1 secretion. Nevertheless, WP increased the levels of both intact GIP and intact GLP-1 (both P < 0.01), and OA increased the levels of intact GLP-1 (P < 0.05). WP inhibited dipeptidyl peptidase IV activity in the proximal small intestine by 50% (P < 0.05), suggesting that luminal degradation of WP generates small fragments, which are substrates for dipeptidyl peptidase IV and act as competitive inhibitors. We therefore conclude that fat and protein may serve as exogenous regulators of secretion and inactivation of the incretin hormones with beneficial influences on glucose metabolism.

High-Aperture Pixel Design Employing VDD Line Elimination for Active Matrix Organic Light Emitting Diode Display

High-aperture ratio pixel design employing polycrystalline silicon thin-film transistors (poly-Si TFTs) for active matrix organic light emitting diode (AMOLED) displays is proposed. The VDD supply line in each pixel is eliminated and the gate scan line is utilized as a VDD supply so that the pixel aperture ratio is increased considerably. The increased emission area achieves low current density through OLED, thus the troublesome OLED luminance degradation would be suppressed and the life-time of OLED materials may be increased. In order to implement the proposed pixel driving, a new fabrication process for the storage capacitor (CST) which uses indium–tin oxide (ITO) and the cathode layers is presented.

Physical mechanism responsible for the stretched exponential decay behavior of aging organic light-emitting diodes

The main process responsible for the luminance degradation in organic light-emitting diodes (OLEDs) driven under constant current has not yet been identified. In this paper, we propose an approach to describe the intrinsic mechanisms involved in the OLED aging. We first show that a stretched exponential decay can be used to fit almost all the luminance versus time curves obtained under different driving conditions. In this way, we are able to prove that they can all be described by employing a single free parameter model. By using an approach based on local relaxation events, we will demonstrate that a single mechanism is responsible for the dominant aging process. Furthermore, we will demonstrate that the main relaxation event is the annihilation of one emissive center. We then use our model to fit all the experimental data measured under different driving condition, and show that by carefully fitting the accelerated luminance lifetime-curves, we can extrapolate the low-luminance lifetime needed for real display applications, with a high degree of accuracy.

Development of a new blue CaMgSi[sub 2]O[sub 6]:Eu[sup 2+] phosphor for PDPs

— A blue-light-emitting Eu2+-doped CaMgSi2O6 phosphor having a long lifetime for a plasma-display panel (PDP) was developed. The CaMgSi2O6:Eu2+(CMS:Eu) phosphors show no luminance degradation during the baking process, and an equivalent photoluminescence peak intensity compared to that of the conventional blue-phosphor BaMgAl10O17:Eu2+ (BAM) after baking. CMS: Eu shows a poor luminescent characteristic for the Xe excimer band excitation due to the lack of absorption. To introduce the absorption center for the Xe excimer band, we performed Gd-codoping of CMS: Eu as a sensitizer and found a new excitation band around 172 nm, which originated from Gd3+. The test PDPs panels using synthesized CMS: Eu phosphor and CMS: Eu, Gd phosphor were examined to investigate the luminescent and aging characteristics of a Xe-discharge excitation source. The CMS: Eu panel shows an emission peak intensity comparable to that of the BAM panel (i.e., a comparable stimuli L/CIEy, 93% of BAM), while the CMS: Eu, Gd panel shows poorer blue emission intensity compared to the BAM panel (up to 53% of total stimuli of BAM). The CMS: Eu panel and the CMS: Eu, Gd panel show less luminance degradation than the BAM panel under the aging test, and the panel retains 90% of its luminance after 300 hours of driving. It was found that CMS: Eu appears to be a candidate for a new blue PDP phosphor because of its longevity in a Xe-discharge plasma environment.

Study of the effect of water on thermal and operating degradation of BaMgAl[sub 10]O[sub 17]:Eu[sup 2+] (BAM) blue phosphor

— From the adsorption and desorption characteristics of water, we showed that water can intercalate into BaMgAl10O17: Eu2+ blue phosphor. ESR, XANES, and XPS analyses confirmed that oxidation by water causes thermal degradation of BAM. We also demonstrated that intercalated water accelerates luminance degradation under VUV irradiation and showed oxidation of Eu2+ during panel operation by means of μ-XPS. We concluded that the cause of thermal and operating degradation of BAM is the oxidation of Eu2+ due to water.

OLED degradation described by using a time-dependent local relaxation model

AbstractThe main mechanisms responsible for the luminance degradation in OLEDs driven under constant current has not yet been identified. In this paper we propose a new approach to describe the intrinsic mechanisms involved in the OLED aging. We will first show that a stretched exponential decay can be used to fit almost all the luminance vs time curves obtained under different driving conditions. In this way we are able to prove that they can all be described by employing a single free parameter model.By using as an approach based on local relaxation events, we will demonstrate that a single mechanism is responsible for the dominant aging process. Furthermore, we will demonstrate that the main relaxation event is the annihilation of one emissive center.We will then use our model to fit all the experimental data measured under different driving condition, and show that by carefully fitting the accelerated luminance lifetime-curves, we can extrapolate the low-luminance lifetime needed for real display applications, with a high degree of accuracy.

The improvement of discharge characteristics and lifetime of alternate current plasma display panel by MgO deposition on the phosphor

An alternate application of MgO film for the improvement of discharge characteristics and lifetime in an ac plasma display panel (PDP) is suggested. In the normal ramp reset, the accumulated wall charges on the phosphor surface just after the reset period are different as to their color (red, green, blue) of each phosphor, which reduces the common voltage margin of ac PDP. In general, MgO is used for the protective layer of dielectrics from ion sputtering and the improvement of secondary electron emission which affects the driving voltage in an ac PDP. In this research, we deposited MgO on the phosphor to get the same addressing characteristics irrespective to the color of each phosphor, high speed addressing, and prolonged lifetime of phosphor despite the vacuum ultraviolet irradiation and ion bombardment. An optimized MgO thickness was used to avoid the excessive luminance and luminous efficacy degradation by the MgO deposition on the phosphor. Results showed that PDP with MgO coated phosphor has more uniform formative delays in address discharges and improved degradation characteristics.

Monte Carlo simulation of imprisonment of Xe resonant photons and luminous efficiency considerations of colour plasma displays

A Monte Carlo model of imprisonment of Xe resonant photons and electronic de-excitation of the Xe resonance level, Xe*, in ac colour plasma displays is developed. The number of resonant photons arriving at phosphor are calculated for various discharge cell heights, discharge thicknesses, Xe mixture ratios, current pulse widths, and drive frequencies in 67 kPa Ne+Xe mixtures. From the calculations, it was found that only 23.2% of the total Xe* participate in generating photons, which arrive at the phosphor under a typical electron density of 5.0 × 1019 m−3. Photons from 22.5% Xe* reach the front glass plate where phosphor is not deposited, and 54.3% of Xe* are de-excited by electronic collisions. Driving the discharge cells at low current density is one of the effective methods of reducing the de-excitation loss. Optimized drive conditions, such as a narrow current pulse drive, can suppress the luminous efficiency degradation. An increase in the height of the discharge cell is preferable provided that the discharge fills the space.

Distinct Steps in Dislocation of Luminal Endoplasmic Reticulum-associated Degradation Substrates: ROLES OF ENDOPLASMIC RETICULUM-BOUND p97/Cdc48p AND PROTEASOME

Dislocation of endoplasmic reticulum-associated degradation (ERAD) substrates from the endoplasmic reticulum (ER) lumen to cytosol is considered to occur in a single step that is tightly coupled to proteasomal degradation. Here we show that dislocation of luminal ERAD substrates occurs in two distinct consecutive steps. The first is passage across ER membrane to the ER cytosolic face, where substrates can accumulate as ubiquitin conjugates. In vivo, this step occurs despite proteasome inhibition but requires p97/Cdc48p because substrates remain entrapped in ER lumen and are prevented from ubiquitination in cdc48 yeast strain. The second dislocation step is the release of accumulated substrates to the cytosol. In vitro, this release requires active proteasome, consumes ATP, and relies on salt-removable ER-bound components, among them the ER-bound p97 and ER-bound proteasome, which specifically interact with the cytosol-facing substrates. An additional role for Cdc48p subsequent to ubiquitination is revealed in the cdc48 strain at permissive temperature, consistent with our finding that p97 recognizes luminal ERAD substrates through multiubiquitin. BiP interacts exclusively with ERAD substrates, suggesting a role for this chaperone in ERAD. We propose a model that assigns the cytosolic face of the ER as a midpoint to which luminal ERAD substrates emerge and p97/Cdc48p and the proteasome are recruited. Although p97/Cdc48p plays a dual role in dislocation and is involved both in passage of the substrate across ER membrane and subsequent to its ubiquitination, the proteasome takes part in the release of the substrate from the ER face to the cytosol en route to degradation.

Luminescence quenching in thermally-treated barium magnesium aluminate phosphor

BaMgAl 10 O 17 : Eu 2+ (BAM) phosphors used for plasma display panels (PDP) are compelled to be exposed to an oxidizing environment at about 500 °C, which is currently unavoidable in the actual manufacturing process of PDP. We investigated the mechanism of the luminance degradation of BAM caused by the annealing at 500 °C, using photoluminescence (PL), decay measurement, and synchrotron light source x-ray absorption and diffraction measurements. The annealing treatment altered the valence state of Eu ions, whereas no new Eu compounds were detected. By estimating the exact fraction of divalent Eu ions and by comparing it with the luminance data, we found that more than 30% degradation of luminance was induced at the expense of only a few percent of divalent Eu. This finding led us to suggest that the origin of the dramatic decrease in PL intensity is not due to the valence state change but due to the local structure change surrounding the Eu2+ ions.

A Novel Approach to Increase Oral Drug Absorption

A comprehensive analytical solution that accounts for many factors and assumptions affecting drug concentration profile in the gastrointestinal tract was presented. A sensitivity analysis approach was utilized in order to investigate the importance of different parameters in the model. The partition coefficient is found to be the key parameter. Hence, for drugs stable in the intestinal wall, increasing partition coefficient only can lead to higher drug absorption. However, for drugs unstable in the intestinal wall, increasing partition coefficient and diffusivity is needed to counteract drug instability. On the other hand, the model is essentially insensitive to degradation in the intestinal lumen for degradation half lives greater than 0.7 min at a given intestinal length. However, a high model sensitivity to the rate of luminal degradation is obtained at higher intestinal length values. The proposed model can be used as a guide for oral drug delivery.

LP‐3: Late‐News Poster: Improvement of Thermal Degradation of Blue Phosphor for Color Plasma Displays

AbstractThe BAM (BaMgAl10O17:Eu2+) solid solution with the barium‐poor aluminate (Ba0.75Al11O17.25) developed in the present work shows the strong resistant property to the thermal degradation, such as luminous efficiency and the color coordinates compared to the conventional BAM. From adopting the BAM solid solution system, it is confirmed that the luminous degradation and the alteration of the color coordinate y value after heat treatment are improved to be about 1/7 and 1/12 of those of the conventional BAM, respectively.

Blue emitting CaAl 2O 4 : Eu 2+ phosphors for PDP application

The single-phase CaAl 2O 4(CA) : Eu 2+ powder phosphors showing 440 nm blue emission were prepared by two-step firing synthesis. It is expected that CA : Eu 2+ phosphor can be applied to plasma display panels (PDPs), because it is more resistant to luminance degradation by heating process in comparison to BaMgAl 10O 17(BAM) : Eu 2+. However, the initial PL luminance of CA : Eu 2+ excited by 147 nm light remains 50% of that of BAM : Eu 2+.

Reveiw article: factors influencing antibiotic transfer across the gastric mucosa

The delivery of antimicrobial drugs to Helicobacter pylori within the stomach is poorly understood. The gastric environment represents a unique pharmacokinetic compartment, into which drug can be delivered directly following oral administration, or indirectly following intestinal absorption and transfer from the blood into the stomach across the gastric mucosa. Several methods have been used to study drug disposition across the gastric mucosa, including endoscopic biopsy studies, nasogastric intubation studies and animal models. Direct, or topical, delivery is limited by luminal drug degradation, drug formulation and the permeability of the mucus layer. Indirect, or systemic, delivery is limited by factors affecting the concentration gradient across the gastric mucosa and the permeability of the mucosa. These factors include intragastric pH, plasma protein binding, drug lipophilicity, the presence of active transport mechanisms, drugs that damage the gastric mucosa and inflammation secondary to H. pylori infection. Little is known about the last of these, and further research in this area should help in the rational approach to development of treatments against H. pylori.

Lamp Life Predictive Model for Avionics Backlights

ABSTRACTActive Matrix Liquid Crystal Displays (AMLCDs) used in avionics applications require high luminance, high efficacy, and long‐life backlights. Currently, fluorescent lamps are the favored light sources for these high performance avionics backlights. Their spectral characteristics and high electrical efficiency are well suited to illuminating AMLCDs used in avionics applications. Fluorescent lamps, however, suffer gradual reduction in luminance output caused by various degradation mechanisms.Korry Electronics Co. recently developed a mathematical model for predicting fluorescent lamp life. The model's basis is the well characterized exponential decay of the phosphor output. The primary luminance degradation mechanism of a fluorescent lamp is related to the arc discharge. Consequently, phosphor depreciation is proportional to the discharge arc power divided by the phosphor surface area. This “wall loading” is a parameter in the computer model developed to extrapolate long‐term luminance performance. Our model predicts a rapidly increasing decay rate of the lamp output as the input power is increased to sustain constant luminance. Eventually, a run‐away condition occurs — lamp arc power must be increased by unrealistically large factors (&gt;5x) to maintain the required luminance output. This condition represents the end of the useful lamp life.The lamp life model requires the definition of several key parameters in order to accurately predict the useful lamp life of an avionics backlight. These important factors include the construction of the lamp, lamp arc power, a decay constant based on the phosphor loading, and the operational profile. Based on the above‐mentioned factors, our model approximates the useful lamp life of an avionics backlight using fluorescent lamp technology. Comparisons between calculated and experimental lamp depreciation are presented.

Novel bioadhesive chitosan-EDTA conjugate protects leucine enkephalin from degradation by aminopeptidase N.

To develop a novel bioadhesive polymer that protects peptide drugs from luminal degradation by aminopeptidase N and to evaluate the system in vitro on porcine mucosa. EDTA was covalently bound to chitosan in order to combine the bioadhesive properties of the polymer with the well known capacity of EDTA to complexed metal ions which are essential for the enzymatic activity of proteases. The inhibitory effect of this polymer conjugate was evaluated by using leucine enkephalin (Leu enkephalin) as a model drug. The degree of Leu enkephalin degradation caused by aminopeptidase N (EC 3.4.11.2), as well as porcine mucosa, in the presence of the polymer conjugate, was quantified by HPLC analysis. The chitosan-EDTA conjugate is capable of binding 2.01 +/- 0.12 mmole of zinc per gram of polymer at pH 6.5 (n = 3; +/-S.D.). As zinc is an essential co-factor for aminopeptidase N, enzyme activity (48 mU/ml) could be completely inhibited under the use of 1.0% chitosan-EDTA conjugate. The inhibitory effect of 1.0% chitosan-EDTA conjugate on the degradation of Leu enkephalin on porcine mucosa within 3 h at 37 degrees C was even 2.9-fold higher than that of a recently developed zinc complexing bacitracin-poly(acrylic acid) conjugate of the same concentration. The novel polymer conjugate is more bioadhesive than unmodified chitosan and is easily hydratable in water and basic aqueous solutions exhibiting quick swelling properties. The bioadhesive polymer conjugate described here seems to be a useful tool in overcoming enzymatic degradation by aminopeptidase N.

Development and Analysis of a Polymer Protecting from Luminal Enzymatic Degradation Caused by α-Chymotrypsin

We have been developing a modified polymer which protects inserted peptide and protein drugs from chymotrypsinic degradation. A trypsin-chymotiypsin-inhibitor was covalently bound to a bioadhesive polymer (poly (acrylic acid)) by a condensation reaction of the available amino groups of the inhibitor with the carboxyl groups of the polymer. The inhibition of α-chymotrypsin by the isolated conjugate was determined by an enzyme assay using N-benzoyl-L-tyrosine ethyl ester as substrate. It had an inhibitory effect of 2.4 CIU (= chymotrypsin inhibiting units) per mg. The protective effect was also evaluated in a drug delivery system containing 5% of this modified polymer. Under physiological α-chymotrypsin concentrations it demonstrated, in lateral parts of the carrier matrix, the remaining of 71.4% ± 14.3% (means of three experiments; ± S.D.) of undigested inserted test-protein (β-galactosidase) afer 7 hr of incubation at 37 ± 0.5°C. Samples from the center of the matrix did not show any digestion of the protein. On the other hand a complete digestion in lateral parts and the remaining of only 67% ± 14.4% of undigested test-protein in the center, could be observed by the same delivery system without the conjugate. Because of this verified protective effect and the possibility to exclude toxic side effects of the inhibitor by immobilization, the system described here seems to be an important step towards a successful peroral (poly)peptide drug administration.

Effect of chronic ethanol administration and dietary protein regimens on intestinal absorption of macromolecules in rats.

The effect of feeding ethanol daily for 40 days has been studied on intestinal absorption of bovine serum albumin (BSA) and gamma-globulin (IgG) in rats fed a low (8%) protein (LP) or a high (30%) protein (HP) diet. Feeding the LP diet enhanced the tissue uptake of BSA (p < 0.05) and absorption of BSA and IgG into serum (p < 0.001) as compared with controls. Feeding the HP diet also augmented the uptake of IgG (p < 0.001) by the intestinal tissue and significantly enhanced serum levels of BSA and IgG. Ethanol feeding to rats for 40 days enhanced the uptake of BSA and IgG (24-84%) and their absorption into serum (p < 0.001) as compared with the controls. Ethanol administration to rats fed LP or HP diets did not alter the uptake of these proteins as compared with their respective controls. Luminal degradation of BSA and IgG was higher in ethanol-administered (48-50% and 36-39%, respectively) and LP-fed rats (50 and 38%, respectively). It was reduced by 17-21% in HP-fed rats as compared with the control group. This indicated that the observed increase in protein absorption is not related to the luminal degradation of the proteins under these conditions. These findings suggest that the absorption of macromolecules from intestine in response to ethanol feeding is influenced by the dietary status of the animals.

Subcutaneous but not Intraluminal Epidermal Growth Factor Stimulates Colonic Growth in Normal Adult Rats

Epidermal growth factor (EGF) was administered by chronic subcutaneous or intracolonic infusion into normal adult rats to determine the effect on colonic growth. Subcutaneous infusion of 200 micrograms EGF/kg/day for 7 days increased the cross-sectional mass and protein content of the muscularis and mucosal layers of the proximal colon, with the distal colon showing less response. In the mucosa, subcutaneous EGF induced proportional increments in the number of cells per crypt, and in the number of cells positively labelled for PCNA, while maintaining a normal crypt growth fraction. In contrast, an 8-fold higher dose of EGF administered intraluminally had no effect on colonic mucosal or muscularis growth. This lack of bioactivity was unlikely to reflect rapid luminal degradation as radiolabelled EGF remained stable in the colonic lumen for at least 4 h. The results demonstrate that the normal adult colon is responsive to subcutaneously delivered EGF, particularly the proximal colon, whereas EGF may not be active on the normal colon when presented from the luminal direction.

Luminal and basolateral uptake and degradation of insulin in the proximal tubules of the dog kidney.

In order to determine the major routes of insulin degradation in the body, insulin was labelled with a 'trapped' or 'residualizing' label: [125I]tyramine-cellobiose ([125I]TC) and injected intravenously in dogs. In contrast to conventional iodine-labelled insulin (131I-insulin), the [125I]TC-insulin allows measurements of total uptake in specific organs in vivo because the radioactive degradation products do not leave the cells. One h after the injection of trace doses, the amount of radioactivity recovered in the kidney from [125I]TC-insulin was nine times higher than when conventional [131I]insulin was used. In the blood, the amount of acid-precipitable radioactivity was the same for both labelled preparations, indicating similar clearance rates. A comparison of the uptake of insulin in filtering vs. non-filtering (ureter-occluded) kidneys indicated that the uptake of insulin is twice as high through the luminal than through the basolateral cell membrane; after 60 min, 8.9 +/- 0.8% of the injected [125I]TC-insulin dose remained in the filtering kidney and 3.2 +/- 0.2% of the dose was accumulated in the contralateral kidney, with occluded ureter but normal blood perfusion. In both filtering and non-filtering (ureter-occluded) kidneys, the subcellular distributions of [125I]TC-insulin were studied after various times by isopycnic sedimentation in sucrose gradients. No difference between peritubular and tubular uptake was discernible. The intracellular transport was rapid, leading to accumulation of radioactive label in dense lysosomes within 10 min.