Hypothesis: is renal allograft rejection initiated by the response to injury sustained during the transplant process?

Allograft rejection can be caused by numerous factors such as damage to the donor kidney during surgical removal or implantation, injury sustained during the transport process between the donor and recipient, and suboptimal allograft perfusion during the intra- and post-operative period. In cadaveric allografts, damage can occur during cold storage, during the transit stage between donor and recipient, and hemodynamic instability due to the initial damage that caused its removal from the donor (such as brain death or trauma). We hypothesize that rejection requires recognition of this injury in addition to recognition of alloantigens. If indeed injury proves to be one factor in acute rejection episodes, then therapeutic efforts can be made to reduce injury during the transplantation process.

Unexpected transurethral resection of prostate syndrome complicated with acute myocardial infarction during transurethral incision procedure--a case report

Transurethral incision (TUI) is a simple and safe procedure. We, herein, present a case undergoing transurethral incision procedure during which he developed transurethral resection of prostate syndrome (TURP syndrome) and hypothermia precipitating an acute perioperative myocardial infarction attack. The potential risk of development of TURP syndrome in settings other than TURP surgery as well as its prevention are reviewed and discussed.

Potential of denaturing gradient gel electrophoresis for scanning of beta-thalassemia mutations in India

Over the last few years, substantial progress has been made in developing strategies for the detection and characterization of various mutations causing beta-thalassemia. The Indian population comprises of numerous endogamous caste groups and beta-thalassemia is seen in almost all of them. Knowledge of the spectrum of beta-thalassemia mutations in the population is a prerequisite for successful implementation of a prevention programme. Among the different approaches available today, Denaturing Gradient Gel Electrophoresis (DGGE) offers a valid technical approach which is applicable for screening of known mutants and polymorphisms as well as in locating regions of DNA bearing unknown mutations. We analysed 356 unrelated beta-thalassemia heterozygotes by DGGE and detected 30 anomalous DGGE patterns. Fifteen mutations were characterized after sequencing 25 anomalous patterns. Of these, codon 10(GCC --> GCA) is a recently reported novel beta-thalassemia mutation while -28(A --> G) and codon 121(G --> T) are being reported for the first time in the Indian population. HbS and HbE also showed two anomalous DGGE patterns each. Framework (FW) linkage studies showed that four mutations were associated with different beta-globin gene frameworks. Linkage of IVSI-5(G --> C) and cap site +1(A --> C) to FW2 and 619-bp deletion to FW1 is being observed for the first time. Multiple DGGE patterns corresponding to the same mutation is one of the major drawbacks of this technique. In spite of this, if sufficient preliminary work has been carried out to compile a comprehensive catalogue of DGGE patterns; this is a powerful approach to characterize the mutation or to localize a small region of DNA in the case of rarer mutations.

Docosahexaenoic acid, a component of fish oil, inhibits nitric oxide production in vitro

INTRODUCTION

Docosahexaenoic acid (DHA) has been shown to be immunosuppressive in the fetus, and fish oil diets are thought to be beneficial in autoimmune disease and transplantation. This effect may be mediated through nitric oxide (NO). Here, we investigate the effect of DHA on murine macrophages.

METHODS

Peritoneal macrophages were subjected to stimulation with various concentrations of interferon gamma-(IFN-gamma) and tumor necrosis factor alpha (TNF-alpha). NO production was assessed by measuring nitrite (Greiss reaction).

RESULTS

At all doses of IFN-gamma and TNF-alpha, DHA was found to be inhibitory to NO production.

CONCLUSIONS

DHA inhibits macrophage-stimulated NO production in response to IFN-gamma and TNF-alpha. As NO is thought to be important in several disease processes, DHA may be a useful agent in the treatment of conditions such as autoimmune disease.

Nonfunctioning pancreatic tumor manifestated as abdominal mass in a child

This report concerns a 9-year-old girl with a nonfunctioning pancreatic tumor presented as an abdominal mass. An encapsulated tumor, measuring approximately 8 x 7 cm, was found during operation, and debulking surgery was done. Histopathologic studies proved that it was a pancreatic tumor, compatible with non-functioning islet cell tumors. She displayed neither clinical picture of jaundice, nor excessive hormonal manifestations such as diarrhea or flushing. No evidence would suggest its association with multiple endocrine neoplasia type I. To our knowledge, it has never been reported in children in Taiwan.

Endoscopic hydrogen peroxide spray may facilitate localization of the bleeding site in acute upper gastrointestinal bleeding

BACKGROUND AND STUDY AIMS

A major problem encountered in the emergency endoscopic management of acute upper gastrointestinal (UGI) bleeding is poor localization of the bleeding site, which can be obscured by blood or clots. Traditional attempts to overcome this problem have been by physical methods, which have usually proved unsatisfactory. The aim of this prospective study was to show that hydrogen peroxide can be used as a dissolution agent, resulting in an alteration of the characteristics of blood clots and allowing a clearer visual field.

PATIENTS AND METHODS

Twenty patients with acute UGI bleeding (13 male, seven female) were included in the study. The suspected site of bleeding was initially sprayed with 200 ml of saline and then with 25-175 ml of 3 % H2O2. Pictures of the visual field were taken before and after irrigation with both saline and H2O2. These pictures were evaluated by three gastroenterologists and scored using the following visual clearance scoring system: -3, marked worsening of visual field; -2, moderate worsening; -1, slight worsening; 0, no change; +1, slight improvement; +2, moderate improvement; + 3, marked improvement. In cases of active oozing or spurting, after initial hemostasis was achieved the bleeding point was injected with pure ethanol or cauterized with a heater probe. In order to assess the safety of 3 % H2O2 endoscopic biopsies of the antrum and the duodenal bulb were performed before and 30 minutes after its use and examined by a pathologist.

RESULTS

There was a significant improvement in the mean visual clearance score after irrigation with H2O2 compared to irrigation with saline alone (2.13 vs. 0.43, P<0.001). During endoscopic examination there were 19 patients with active oozing from the ulcer base covered by an adherent blood clot; 12 of these (63.1%) achieved initial hemostasis after H2O2 spraying. Eleven of 18 (61.1 %) patients complained of a mild epigastric burning sensation during H2O2 irrigation. There was no clinically significant change in the histology of the antrum and the duodenal bulb after H2O2 therapy.

CONCLUSIONS

We concluded that H2O2 is a safe and effective way to clear the visual field, facilitating the localization of the bleeding site during emergency endoscopy for acute UGI bleeding, with only mild side effects. In some cases H2O2 therapy can also induce temporary hemostasis. We recommended the use of hydrogen peroxide to improve endoscopic visualization, especially in cases where an adherent blood clot covers the suspected bleeding site.

Interaction of hydroxycinnamic acid derivatives with the Cl3COO radical: a pulse radiolysis study

The electron transfer reactions between the trichloromethylperoxyl radical (Cl3COO*) and hydroxycinnamic acid derivatives, including chlorogenic acid, sinapic acid, caffeic acid, ferulic acid and 3,4-(methylenedioxy)cinnamic acid, have been studied by pulse radiolysis. The hydroxycinnamic acid derivatives, especially sinapic acid, are identified as good antioxidants for reduction of Cl3COO* via electron transfer reactions. From buildup kinetic analysis of phenoxyl radical, the rate constant for reaction of Cl3COO* with sinapic acid has been determined to be 8.2x10(7) dm3 mol(-1) s(-1), while the rate constants of electron transfer from other hydroxycinnamic acid derivatives to Cl3COO* were obtained to be about 2x10(7) dm3 mol(-1) s(-1). The reaction of 3,4-(methylenedioxy) cinnamic acid with Cl3COO* was investigated as an evidence for the electron transfer mechanism.

Concurrent increase of oxidative DNA damage and lipid peroxidation together with mitochondrial DNA mutation in human lung tissues during aging--smoking enhances oxidative stress on the aged tissues

Although mutation of mitochondrial DNA (mtDNA) in human tissues has been established to associate with intrinsic aging, the impact of environmental factors on the formation and accumulation of mtDNA mutations and oxidative DNA damage in human tissues is poorly understood. We have investigated the levels of mtDNA with the 4977-bp deletion and A3243G point mutation, oxidative DNA damage (indicated by the formation of 8-hydroxy-2'-deoxyguanosine, 8-OH-dG), and lipid peroxides in lung tissues from smokers and nonsmokers of subjects of different ages. The results showed concurrent age-dependent increase of the 4977-bp deleted mtDNA (P < 0.001), 8-OH-dG (P < 0.05), and lipid peroxides (P < 0.05) in the human lung. In the group of subjects above 60 years old, smokers had more extensive DNA damage and lipid peroxidation than did the nonsmokers. However, the levels of mtDNA with the 4977-bp deletion and A3243G point mutation in the lung of smokers were not significantly different from those of the age-matched nonsmokers. Taken together, these results suggest that accumulation of mtDNA with the 4977-bp deletion together with oxidative DNA damage and lipid peroxides is associated with aging and that smoking enhances oxidative damage in human lung tissues.

Oxidative damage elicited by imbalance of free radical scavenging enzymes is associated with large-scale mtDNA deletions in aging human skin

Mitochondrial DNA (mtDNA) mutations and impaired respiratory function have been demonstrated in various tissues of aged individuals. We hypothesized that age-dependent increase of ROS and free radicals production in mitochondria is associated with the accumulation of large-scale mtDNA deletions. In this study, we first confirmed that the proportion of mtDNA with the 4977 bp deletion in human skin tissues increases with age. We then investigated the 8-hydroxy-2'-deoxyguanosine (8-OH-dG) content in skin tissues and lipid peroxides content of the skin fibroblasts from subjects of different ages. The results showed an age-dependent increase of 8-OH-dG level in the total DNA of skin tissues of the subjects above the age of 60 years. The specific content of malondialdehyde, an end product of lipid peroxidation, was also found to increase with age. On the other hand, we examined the enzyme activities of Cu, Zn-superoxide dismutase (Cu,Zn-SOD), Mn-superoxide dismutase (Mn-SOD), catalase, and glutathione peroxidase (GPx) in the skin fibroblasts. The activities of Cu,Zn-SOD, catalase and glutathione peroxidase were found to decrease with age. However, the activity of Mn-SOD was increased with age before 60 years but was decreased thereafter. Moreover, the activity ratios of Mn-SOD/catalase and Mn-SOD/GPx exhibited the same pattern of change with age. This indicates that free radical scavenging enzymes can effectively dispose of ROS and free radicals before 60 years of age. However, elevated oxidative stress caused by an imbalance between the production and removal of ROS and free radicals occurred in skin fibroblasts after 60 years of age. Taken together, we suggest that the functional decline of free radical scavenging enzymes and the elevation of oxidative stress may play an important role in eliciting oxidative damage and mutation of mtDNA during the human aging process.

The hemodynamic changes of gastroduodenal regional blood flow after Helicobacter pylori eradication in patients with duodenal ulcer scar

Duodenal ulcer (DU) is frequently accompanied by Helicobacter pylori (Hp) infection and associated with the imbalance of aggressive factors and defensive factors. To investigate the possible relationship between Hp and regional gastric blood flow, 26 endoscopically proved DU (scar stage) and Hp infection patients were included and received triple therapy (colloid bismuth subcitrate 120 mg qid for 4 weeks, amoxicillin 500 mg qid for 2 weeks and metronidazole 250 mg tid for 2 weeks). Regional gastroduodenal blood flow (RGDF) was measured at DU scar area and antrum lesser curvature site by laser Doppler flowmetry during endoscopic examination, before and one month after triple therapy. In 22 patients with Hp eradication the RGDF was significantly elevated at antrum lesser site after triple therapy (p < 0.05) but there was no difference at DU scar area. However, in 4 patients without Hp eradication no difference of RGDF in these two points was found. Therefore, Hp appears to have direct effects on gastric microcirculation.

Aging- and smoking-associated alteration in the relative content of mitochondrial DNA in human lung

mtDNA mutations and oxidative DNA damage has been observed to accumulate in the lung and other tissues in human aging. Thus, it is of interest to know whether the content of mtDNA is changed in aging tissues of the human. Using a competitive PCR method, we determined the relative content of mtDNA in the lung tissues of 49 subjects aged 16-85 years. The results showed that the relative content of mtDNA (with respect to the beta-actin gene) in the lung tissues was significantly increased with age (P < 0.005). The average mtDNA content in the lung tissues of the subjects over 80 years of age was found to be about 2.6-fold higher than that of the subjects below age 20. However, the relative content of mtDNA was slightly increased in the lung tissues of light smokers but significantly decreased in heavy smokers. Moreover, we found a significant increase with age in the level of oxidative damage to DNA as indicated by the ratio of 8-OH-dG/dG in total DNA (P < 0.0005). These results together with our previous findings suggest that the increase in mtDNA content of aging tissues may be effected through a feedback mechanism to compensate for the functional decline of mitochondria in human aging and that smoking may modulate the mechanism.

Natural infection of a homozygous delta24 CCR5 red-capped mangabey with an R2b-tropic simian immunodeficiency virus

A homozygous 24-bp deletion (Delta24) was found in the CC chemokine receptor 5 (CCR5) of 11 out of 15 red-capped mangabeys (RCMs), Cercocebus torquatus torquatus, both in Africa and in an American zoo. The CCR5 Delta24 defect encompassed eight amino acids in frame in the fourth transmembrane region. Unexpectedly, RCM-009, one of 11 homozygotes (Delta24CCR5/ Delta24CCR5), was found to be naturally infected with a divergent simian immunodeficiency virus (SIV) strain, which was not R5-tropic, but used CCR2b (R2b) as its major coreceptor. SIVrcmGab1 was the only R2b-tropic SIV among other divergent SIVs tested. Cells transfected with the Delta24 CCR5 did not support entry of R5-tropic SIVmac, SIVcpz, SIVmne, HIV-2, or HIV-1, and were also inactive in signal transduction mediated by beta-chemokines. At 86.6%, the Delta24 allelic frequency was significantly higher than that of the 32-bp deletion found in humans. The Delta24 frequency was 4.1% in 34 sooty mangabeys (SMs), a geographically isolated subspecies that was naturally infected with R5-tropic SIV. Finding identical deletions in two mangabey subspecies separated for 10,000 years or more dates the Delta24 CCR5 deletion as ancient. However, the source of the selective pressure for the high rate of CCR5 deletion in RCMs remains to be determined. The high allelic frequency of the Delta24 CCR5 in RCMs, in comparison to that of SMs, suggests that R2b-tropism may have been acquired by SIVrcm, as an adaptation to CCR5 genetic defects appeared in its host.

Oxidative damage and mutation to mitochondrial DNA and age-dependent decline of mitochondrial respiratory function

Mitochondrial respiration and oxidative phosphorylation are gradually uncoupled, and the activities of the respiratory enzymes are concomitantly decreased in various human tissues upon aging. An immediate consequence of such gradual impairment of the respiratory function is the increase in the production of the reactive oxygen species (ROS) and free radicals in the mitochondria through the increased electron leak of the electron transport chain. Moreover, the intracellular levels of antioxidants and free radical scavenging enzymes are gradually altered. These two compounding factors lead to an age-dependent increase in the fraction of the ROS and free radical that may escape the defense mechanism and cause oxidative damage to various biomolecules in tissue cells. A growing body of evidence has established that the levels of ROS and oxidative damage to lipids, proteins, and nucleic acids are significantly increased with age in animal and human tissues. The mitochondrial DNA (mtDNA), although not protected by histones or DNA-binding proteins, is susceptible to oxidative damage by the ever-increasing levels of ROS and free radicals in the mitochondrial matrix. In the past few years, oxidative modification (formation of 8-hydroxy-2'-deoxyguanosine) and large-scale deletion and point mutation of mtDNA have been found to increase exponentially with age in various human tissues. The respiratory enzymes containing the mutant mtDNA-encoded defective protein subunits inevitably exhibit impaired respiratory function and thereby increase electron leak and ROS production, which in turn elevates the oxidative stress and oxidative damage of the mitochondria. This vicious cycle operates in different tissue cells at different rates and thereby leads to the differential accumulation of mutation and oxidative damage to mtDNA in human aging. This may also play some role in the pathogenesis of degenerative diseases and the age-dependent progression of the clinical course of mitochondrial diseases.

Comparison of once daily cefpodoxime proxetil suspension and thrice daily cefaclor suspension in the treatment of acute otitis media in children

An open-labeled and randomized trial was conducted to compare the efficacy and safety of once daily cefpodoxime proxetil suspension (10mg/kg/day) and thrice daily cefaclor (45mg/kg/day) in the treatment of acute otitis media in children. A total of 57 children aged from 6 months to 9 years were enrolled; 23 were treated with cefpodoxime and 34 with cefaclor. Satisfactory clinical outcome, either cure or improvement, was achieved at the end of treatment in 90% of patients in the cefaclor group and 95% of patients in the cefpodoxime group (p > 0.05). Clinical recurrence was identified at the follow-up visits in one case of the cefaclor group (3%), and none in the cefpodoxime group (p > 0.05). These drugs were well tolerated by 14/21 (67%) in the cefpodoxime-treated group and 27/32 (84%) in the cefaclor-treated group. The incidence of adverse events was slightly higher in the cefpodoxime group than in the cefaclor group, however the difference did not reach statistical significance (p > 0.05). The daily cost of once-daily cefpodoxime was lower than that of thrice-daily cefaclor. We conclude that cefpodoxime administered once daily is as effective and safe as cefaclor administered thrice daily in the treatment of acute otitis media in children. The less dosing frequency and lower daily price of cefpodoxime provide additional benefits.

[Inhibition of GABA-activated currents in isolated rat DRG neurons by bradykinin]

In the present paper, the modulation of GABA-activated currents by bradykinin (BK) was studied in DRG neurons freshly isolated from rat using whole-cell patch-clamp techniques. Among the neurons (n = 34) responding to GABA, 27 were sensitive to BK. Pre-application of BK, eliciting an inward current alone, inhibited GABA-activated current markedly. For example, 10(-6) mol/L BK suppressed GABA-activated current by about 30%. BK shifted the GABA dose-response curve downward obviously and depressed the maximal response to GABA by 1/3 or more while the Kd value was unchanged. The results suggest that BK inhibits GABA-activated current noncompetitively in rat DRG neurons.

Docosahexaenoic acid, a constituent of fetal and neonatal serum, inhibits nitric oxide production by murine macrophages stimulated by IFN gamma plus LPS, or by IFN gamma plus Listeria monocytogenes

Murine macrophage activation is deficient in the fetus and the neonate, and in areas of the placenta perfused by the fetal circulation. Fetal and neonatal serum concentrations of docosahexaenoic acid (DHA) are 150 microM, or approximately 50-fold higher than in the adult. We previously showed that DHA inhibits activation of the gene for inducible nitric oxide synthase (iNOS) in murine macrophages stimulated in vitro with interferon gamma (IFN gamma) plus lipopolysaccharide (LPS). We have now pursued these observations in greater depth. An assay system was developed which separated the stimulation of macrophages by IFN gamma plus LPS, and the actual production of nitric oxide (NO). It was found that macrophages do not produce NO until they have been stimulated by IFN gamma plus LPS for a period of 10 h. NO is produced during the subsequent 10 h, even though IFN gamma plus LPS are not longer present. DHA, if present, inhibited only during the initial 10 h stimulation; DHA did not inhibit the production of NO by macrophages which had previously been stimulated by IFN gamma plus LPS, and were already producing NO. It was also found that DHA was less inhibitory if given prior to the IFN gamma plus LPS stimulation. In a dose-responsive manner, DHA inhibited the increased abundance of iNOS mRNA by macrophages stimulated by IFN gamma plus LPS. NO contributes to the host defense against Listeria monocytogenes and other intracellular pathogens. We therefore investigated the ability of DHA to inhibit NO production by macrophages stimulated by IFN gamma plus Listeria monocytogenes in vitro; DHA inhibited transcription of the iNOS gene and also the listeriocidal activity of activated macrophages. Inhibition of NO production by DHA may contribute to the increased susceptibility of the fetoplacental unit and neonate to intracellular infections.

The influence of alpha-thalassaemia on the haematological & clinical expression of sickle cell disease in western India

We evaluated the clinical and haematological features of 29 sickle cell anaemia patients with associated alpha-thalassaemia and 22 sickle cell homozygotes with a normal alpha-globin genotype from western India. The presence of alpha-thalassaemia resulted in significantly higher haemoglobin (Hb), haematocrit (HCT), red blood cells counts (RBC) and haemoglobin A2 (HbA2) levels but lower mean cell haemoglobin (MCH) and mean cell volume (MCV). The clinical presentation in these patients was also milder with fewer episodes of painful crisis, chest syndromes, infections, requirement of hospitalization and blood transfusions. However, splenomegaly was more common as compared to the patients with a normal alpha-globin genotype. It is evident from the present study that alpha-thalassaemia could be an important genetic factor modulating the clinical expression and haematological severity of sickle cell anaemia in this region.

Natural infection of a household pet red-capped mangabey (Cercocebus torquatus torquatus) with a new simian immunodeficiency virus

A seroprevalence survey was conducted for simian immunodeficiency virus (SIV) antibody in household pet monkeys in Gabon. Twenty-nine monkeys representing seven species were analyzed. By using human immunodeficiency virus type 2 (HIV-2)/SIVsm, SIVmnd, and SIVagm antigens, one red-capped mangabey (RCM) (Cercocebus torquatus torquatus) was identified as harboring SIV-cross-reactive antibodies. A virus isolate, termed SIVrcm, was subsequently established from this seropositive RCM by cocultivation of its peripheral blood mononuclear cells (PBMC) with PBMC from seronegative humans or RCMs. SIVrcm was also isolated by cocultivation of CD8-depleted RCM PBMC with Molt 4 clone 8 cells but not with CEMx174 cells. The lack of growth in CEMx174 cells distinguished this new SIV from all previously reported sooty mangabey-derived viruses (SIVsm), which grow well in this cell line. SIVrcm was also successfully transmitted (cell free) to human and rhesus PBMC as well as to Molt 4 clone 8 cells. To determine the evolutionary origins of this newly identified virus, subgenomic pol (475 bp) and gag (954 bp) gene fragments were amplified from infected cell culture DNA and sequenced. The position of SIVrcm relative to those of members of the other primate lentivirus lineages was then examined in evolutionary trees constructed from deduced protein sequences. This analysis revealed significantly discordant phylogenetic positions of SIVrcm in the two genomic regions. In trees derived from partial gag sequences, SIVrcm clustered independently from all other HIV and SIV strains, consistent with a new primate lentivirus lineage. However, in trees derived from pol sequences, SIVrcm grouped with the HIV-1/SIVcpz lineage. These findings suggest that the SIVrcm genome is mosaic and possibly is the result of a recombination event involving divergent lentiviruses in the distant past. Further analysis of this and other SIVrcm isolates may shed new light on the origin of HIV-1.

Haemoglobin D-Ouled Rabah among the Mozabites: a relevant variant to trace the origin of Berber-speaking populations

We have studied haemoglobin (Hb) variants and blood groups (ABO, RH, and Kell) in 598 children from the Berber population of the Mzab. Hb D-Ouled Rabah, considered as a private marker of the Kel Kummer Tuaregs, and Hb C were found at the same gene frequency (0.015). Haplotype analysis suggests a single origin to the Hb D mutation. Genetic distances calculated from the blood group data cluster Mozabites and Tuaregs with the other Berber-speaking groups, Arabic-speaking populations being more distant. But, we found no specific relationship between Mozabites and Kel Kummers. Tuaregs in general exhibit features that tend to differentiate them from other Berber-speaking groups. Hb D-Ouled Rabah may be specific of Berber-speaking populations.

Effects of recombinant human endothelial-derived interleukin-8 on hemorrhagic shock in rats

AIM

To study the effects of recombinant human endothelial-derived interleukin-8 (IL-8) on hemorrhagic shock.

METHODS

A profound hemorrhagic shock in rats was produced by exsanguination from femoral artery with mean arterial blood pressure (MABP) maintained at 5.32 kPa for 90 min. After transfusion, IL-8 250 micrograms.kg-1 was i.v. injected. Plasma endothelin-1 (ET-1) and 6 ketoprostaglandin F1 alpha (6-KPGF1 alpha) contents were determined with radioimmunoassay.

RESULTS

After i.v. IL-8, the MABP in IL-8 group was elevated obviously (P < 0.01), the rat survival 2 h after infusion was increased (P < 0.05). During profound shock the plasma ET-1 levels were higher (21 +/- 4 vs 8.2 +/- 1.8 ng.L-1, P < 0.01) and the plasma 6-KPGF1 alpha contents lower than those in normal rats (107 +/- 12 vs 157 +/- 11 ng.L-1, P < 0.01). IL-8 remarkably reduced the plasma ET-1 levels (10 +/- 4 ng.L-1, P < 0.01) and enhanced plasma 6-KPGF1 alpha contents (368 +/- 16 ng.L-1, P < 0.01).

CONCLUSION

IL-8 has beneficial antishock effects.

Energy control by linking individual patterns to self-repeating diffractive optical elements

In general, as diffractive optical elements formed by use of self-repeating patterns possess beneficial characteristics such as scratch resistance, low design effort, ease of fabrication, and natural formation of large panels, an efficient design methodology that was developed with a modified preserving-the-best strategy of genetic algorithms is presented. Both genetic algorithms and simulated annealing are examined by the Markov-chain stochastic process to create the insight needed to use these two heuristic algorithms efficiently. It was found that adding the preserving-the-best strategy to traditional genetic algorithms guarantees the possibility of locating the global optimum. Combining this sufficient and necessary condition for locating a global optimum for genetic algorithms with the built-in chromosome crossover searching mechanism and its neighborhood identification makes this newly developed genetic algorithm an effective method for designing diffractive optical elements. In our study, a prototype was fabricated based on our case study with the modified genetic algorithm. The performance of this prototype was measured and analyzed. Experimental results are shown to agree well with theoretical predictions.