Prospects of near-field plasmonic absorption enhancement in semiconductor materials using embedded Ag nanoparticles.

Metal nanoparticles are efficient antennas for light. If embedded in a semiconductor material, they can enhance light absorption in the semiconductor, due to the strong plasmonic near-field coupling. We use numerical simulations to calculate the absorption enhancement in the semiconductor using Ag nanoparticles with diameters in the range 5-60 nm for crystalline Si, amorphous Si, a polymer blend, and Fe2O3. We study single Ag particles in a 100×100×100 nm semiconductor volume, as well as periodic arrays with 100 nm pitch. We find that in all cases Ohmic dissipation in the metal is a major absorption factor. In crystalline Si, while Ag nanoparticles cause a 5-fold enhancement of the absorbance in the weakly absorbing near-bandgap spectral range, Ohmic losses in the metal dominate the absorption. We conclude crystalline Si cannot be sensitized with Ag nanoparticles in a practical way. Similar results are found for Fe2O3. The absorbance in the polymer blend can be enhanced by up to 100% using Ag nanoparticles, at the expense of strong additional absorption by Ohmic losses. Amorphous Si cannot be sensitized with Ag nanoparticles due to the mismatch between the plasmon resonance and the bandgap of a-Si. By using sensitization with Ag nanoparticles the thickness of some semiconductor materials can be reduced while keeping the same absorbance, which has benefits for materials with short carrier diffusion lengths. Scattering mechanisms by plasmonic nanoparticles that are beneficial for enhanced light trapping in solar cells are not considered in this paper.

Optical impedance matching using coupled plasmonic nanoparticle arrays.

Silver nanoparticle arrays placed on top of a high-refractive index substrate enhance the coupling of light into the substrate over a broad spectral range. We perform a systematic numerical and experimental study of the light incoupling by arrays of Ag nanoparticle arrays in order to achieve the best impedance matching between light propagating in air and in the substrate. We identify the parameters that determine the incoupling efficiency, including the effect of Fano resonances in the scattering, interparticle coupling, as well as resonance shifts due to variations in the near-field coupling to the substrate and spacer layer. The optimal configuration studied is a square array of 200 nm wide, 125 nm high spheroidal Ag particles, at a pitch of 450 nm on a 50 nm thick Si(3)N(4) spacer layer on a Si substrate. When integrated over the AM1.5 solar spectral range from 300 to 1100 nm, this particle array shows 50% enhanced incoupling compared to a bare Si wafer, 8% higher than a standard interference antireflection coating. Experimental data show that the enhancement occurs mostly in the spectral range near the Si band gap. This study opens new perspectives for antireflection coating applications in optical devices and for light management in Si solar cells.

Controlling Fano lineshapes in plasmon-mediated light coupling into a substrate.

Metal nanoparticles are efficient resonant plasmonic scatterers for light, and, if placed on top of a high-index substrate, can efficiently couple light into the substrate. This coupling, however, strongly depends on particle shape and surrounding environment. We study the effect of particle shape and substrate refractive index on the plasmonic resonances of silver nanoparticles and we systematically relate this to the efficiency of light scattering into a substrate. The light coupling spectra are dominated by Fano resonances for the corresponding dipolar and quadrupolar scattering modes. Varying the particle shape from spherical to cylindrical leads to large shifts in the Fano resonance for the dipolar mode, reducing the light incoupling integrated over the AM1.5 spectral range. Using a dielectric spacer layer, good light coupling is achieved for cylinders in the near-infrared. An asymmetric environment around the particles turns quadrupolar resonances into efficient radiators as well.

D-aspartate and reproductive activity in sheep.

D-aspartic acid (D-Asp) has been isolated from neuroendocrine tissues of many invertebrates and vertebrates. Recently, it has been demonstrated that this D-amino acid may be converted to N-methyl-D-aspartic acid (NMDA), a neuromodulator associated with sexual activity. In this study, we determined D-Asp and NMDA concentrations in endocrine glands and other tissues in ewes after D-Asp administration and in controls. We also evaluated the effects of d-Asp administration on the reproductive activity of ewes by determining either progesterone concentrations or LH pulses in the presence or absence of estradiol benzoate. The pineal gland showed the highest natural content of D-Asp (1.47+/-0.22 micromol/g tissue), whereas the pituitary gland had the highest capability to store d-Asp, with a peak value (9.7+/-0.81 micromol/g tissue) 6 h after its administration. NMDA increased sharply 12 h following D-Asp administration, reaching values three times higher than the baseline in both the pituitary and brain. D-Asp was quickly adsorbed after subcutaneous administration, with a peak in plasma levels 2 h after administration and a return to baseline values after 6 h. D-Asp administration achieved a significant (P < 0.001) increase in LH values with respect to estradiol or estradiol + D-Asp treatments. d-Asp treatment once or twice a week did not successfully drive acyclic ewes into reproductive activity. In conclusion, the results obtained in this study demonstrated that D-Asp is endogenously present in sheep tissues and electively stored in endocrine glands and brain after its administration. NMDA and LH increase following D-Asp administration suggesting a role of this D-amino acid in the reproductive activity of sheep.

Multiple approach to the exploration of genotype-phenotype correlations in familial adenomatous polyposis.

PURPOSE: Familial adenomatous polyposis (FAP), caused by a mutation in the APC gene, is a colorectal cancer predisposition syndrome associated with several other clinical conditions. The severity of the FAP is related to the position of the inherited mutation in the APC gene. We analyzed a large series of FAP patients to identify associations among major clinical manifestations and to correlate the mutation site with specific disease manifestations. MATERIALS AND METHODS: APC mutations were identified in 953 FAP patients from 187 families. We used unconditional logistic regression models and a method involving generalized estimating equations to investigate the association between genotype and phenotype. We used multiple correspondence analysis to represent the interrelationships of a multiway contingency table of the considered variables. RESULTS: APC germline mutations were located between codons 156 and 2011 of the APC gene. Mutations spanning the region between codons 543 and 1309 were variable, but strongly associated with congenital hypertrophy of retinal pigment epithelium. Mutations between codons 1310 and 2011 were associated with a six-fold risk of desmoid tumors relative to the low-risk reference region (159 to 495). Mutations at codon 1309 were associated with early development of colorectal cancer. Mutations between codons 976 and 1067 were associated with a three- to four-fold increased risk of duodenal adenomas. The cumulative frequency of extracolonic manifestations was highest for mutations between codons 976 and 1067, followed by mutations between 1310 and 2011. CONCLUSION: Analysis of the relation between APC mutation site and phenotype identifies subgroups of FAP patients at high risk for major extracolonic disease, which is useful for surveillance and prevention.

Reducing colorectal cancer mortality by repeated faecal occult blood test: a nested case-control study.

Randomised trials have shown the efficacy of faecal occult blood testing (FOBT) in reducing colorectal cancer mortality, but observational studies are needed to monitor such efficacy in population programmes. We conducted a nested case-control study on a cohort of 21,879 subjects who participated in a colorectal screening programme from 1978 to 1995, undergoing at least one FOBT test. 95 fatal cases of colorectal cancer were eligible for the study. For each fatal case, 5 non-fatal matched controls were randomly selected from the cohort. FOBT screening history was less common among cases than controls. The odds ratio of colorectal cancer mortality among 'attenders' (defined as those who underwent a second FOBT within 2 years of study entry) with respect to 'non-attenders' was 0.64 (95% confidence interval 0.36-1.15). We also computed odds ratios defining exposure as one or more tests in the detectable preclinical period, hypothesising various lengths for the latter, which, however, yielded an efficacy estimate biased towards the null. A strong inverse relationship was observed between mortality and the number of tests, but this phenomenon is interpretable as 'healthy screenee bias'. The results suggest that the potential efficacy in preventing colorectal cancer mortality through annual FOBT screening may be of the order of one third.

Molecular characterization of P-29, a metacestode-specific component of Echinococcus granulosus which is immunologically related to, but distinct from, antigen 5.

In this work the characterization of P-29, a novel 29 kDa antigen from Echinococcus granulosus is reported. E. granulosus was identified while looking for parasite antigens distinct from those present in hydatid cyst fluid. A monoclonal antibody (mAb 47H.PS) prepared against protoscolex components revealed that P-29 is localized to the tegument and rostellum of protoscoleces, and to the germinal layer of the cyst, but it is absent in hydatid cyst fluid or adult worm extracts. Several internal fragments of P-29 showed sequence identity to the amino acid sequence encoded by Eg6, a partial gene sequence reported to code for an epitope of antigen 5 (Ag5), one of the major diagnostic antigens of the parasite. We confirmed that Eg6 encodes a sub-fragment of P-29 by mapping the epitope of mAb 47H.PS, and isolating the full length P-29 cDNA. Since Eg6 had been, postulated to encode a fragment of Ag5, we specifically studied the relationship of P-29 and Ag5 by: (i) examining the cross-reactivity displayed by different mAbs; (ii) comparison of their peptide finger prints; and (iii) a comparative study of their diagnostic value. Our results prove unequivocally that P-29 and Ag5 are immunologically related, but different proteins, raising several questions on the current knowledge of Ag5.

Testicular endocrine activity is upregulated by D-aspartic acid in the green frog, Rana esculenta.

This study investigated the involvement of D-aspartic acid (D-Asp) in testicular steroidogenesis of the green frog Rana esculenta and its effect on stimulation of thumb pad morphology and glandular activity, a typical testosterone-dependent secondary sexual characteristic in this amphibian species. In the testis, D-Asp concentrations vary significantly during the reproductive cycle: they are low in pre- and post-reproductive periods, but reach peak levels in the reproductive period (140-236 nmol/g wet tissue). Moreover, the concentrations of D-Asp in the testis through the sexual cycle positively match the testosterone levels in the gonad and the plasma. The racemase activity evaluated during the cycle expresses its peak when D-Asp and testosterone levels are highest, that is, during the reproductive period, confirming the synthesis of D-Asp from L-Asp by an aspartate racemase. Short-term in vivo experiments consisting of a single injection of D-Asp (2.0 micro mol/g body weight) demonstrated that this amino acid accumulates significantly in the testis, and after 3 h its uptake is coupled with a testosterone increase in both testis and plasma. Moreover, within 18 h of amino acid administration, the D-Asp concentration in the testis decreased along with the testosterone titer to prestimulation levels. Other amino acids (L-Asp, D-Glu and L-Glu) used instead of D-Asp were ineffective, confirming that the significant increase in testicular testosterone was a specific feature of this amino acid. In long-term experiments, D-Asp had been administered chronically to frogs caught during the three phases of the reproductive cycle, inducing testosterone increase and 17beta-estradiol decrease in the gonad during the pre- and post-reproductive period, and vice versa during the reproductive period. The stimulatory effect of D-Asp on testosterone production by the testis is consistent with the stimulation of spermatogenesis and the maturation of thumb pads occurring in D-Asp-treated frogs. In these last animals, there was an increase of seminiferous ampoule area and a higher number of spermatids and sperm. Moreover, in spermatogonia I and II and in spermatocytes, a proliferating cell nuclear antigen (PCNA) intense immunopositivity was observed. In addition, the thumb pads of D-Asp-treated frogs compared with controls showed a significantly thicker epithelial lining, a wider area of their glands with taller secretion cells, and more numerous, PAS-positive-rich secretions. Finally, these results provide functional evidence for a biologic role of D-Asp in amphibian male steroidogenesis; therefore, this unusual amino acid could be considered a modulatory agent for reproductive processes.

Expression of HLA class II determinants by normal and chronic myeloid leukemia progenitors.

It has been suggested that the expression of some HLA class II antigens, derived from three loci (DR, DP, DQ) is important in the regulation of both the immune response and the response of haemopoietic progenitors to regulation factors, such as acidic isoferritins (AIF), as well as in the interaction between T lymphocytes and erythroid progenitors (BFU-E). Changes in the expression of class II antigens have been reported on the surface of granulo-monocyte progenitors in chronic myeloid leukemia (CML) and correlated to the abnormal proliferation of such cells. In this study, monoclonal antibodies against DR and DQ monomorphic determinants were used to investigate the expression of these antigens on the surface of normal and CML bone marrow and peripheral blood BFU-E by means of complement mediated cytotoxicity. It was found that most normal and leukemic BFU-E express DR antigens. Antigens density tends to be greater on marrow as opposed to peripheral precursors. In addition, leukemic BFU-E are more sensitive to cytolytic treatment than their normal counterparts. Normal BFU-E do not express detectable amounts of DQ antigens, whereas these are present on a proportion of leukemic BFU-E.

Ranitidine bismuth citrate with either clarithromycin 1 g/day or 1.5 g/day is equally effective in the eradication of H. pylori and healing of duodenal ulcer.

BACKGROUND: No randomized double-blind studies have been performed to compare clarithromycin 1 g/day with higher doses of the macrolide (1.5 g/day) when combined with ranitidine bismuth citrate (RBC). AIM: To compare H. pylori eradication and ulcer healing rates of RBC 400 mg b.d. for 4 weeks combined for the first 2 weeks either with clarithromycin 500 mg b.d. (Group A) or clarithromycin 500 mg t.d.s. (Group B). METHODS: Two hundred and seventy-three patients with H. pylori-positive active duodenal ulcer were included. H. pylori infection was detected by CLO-test and histology on antral and corpus biopsies before and at least 4 weeks after the end of therapy. Eradication was assumed if both CLO-test and histology results were negative for H. pylori. RESULTS: Eradication/healing rates according to intention-to-treat and per protocol analysis were 76/82% and 87/92% for Group A and 78/85% and 88/95% for Group B, respectively (P = N.S.). Adverse events were reported by 7% and 12% of patients in Groups A and B, respectively, and they were generally mild. CONCLUSIONS: RBC in co-prescription with clarithromycin 500 mg b.d. is as effective as RBC plus clarithromycin 500 t.d.s. in eradicating H. pylori and healing duodenal ulcers.

Myocilin Gln368stop mutation and advanced age as risk factors for late-onset primary open-angle glaucoma.

BACKGROUND: Juvenile open-angle glaucoma has been found to be associated with molecular defects in the myocilin (MYOC) gene. Most of the defects are missense mutations located in the third exon. The Gln368stop mutation has recently been found in several cases of late-onset primary open-angle glaucoma (POAG). OBJECTIVE: To study the effect of glaucoma risk in a relatively homogeneous genetic population. METHODS: A clinical study was performed in all living members of a 5-generation family. DNA analysis was performed for studying association with genetic markers and identifying the mutation. RESULTS: We identified the Gln368stop molecular defect in 19 patients with POAG, 5 patients with ocular hypertension, and 22 healthy carriers. We compared affected and unaffected carriers based on age at onset and last examination, respectively. Besides the presence of 3 young patients with POAG (<40 years old), the number of glaucomatous patients in the advanced age group increased. CONCLUSIONS: The penetrance of glaucoma increases with age in Gln368stop carriers, but some remain unaffected at advanced age and others are affected at an early age. This suggests that additional risk factors are operating within this family, which may be identified by a genome-wide linkage search in this large pedigree. CLINICAL RELEVANCE: The myocilin Gln368stop mutation shows a good genotype-phenotype correlation and should be investigated in all familiar cases of chronic POAG. This may be important for early diagnosis and periodical checkups of presymptomatic individuals belonging to these families.

Conservative management of esophageal leaks by transluminal endoscopic drainage of the mediastinum or pleural space.

BACKGROUND: The management of postoperative leaks into the mediastinum or pleural cavities after esophageal surgery yields unsatisfactory results. A recently described method, drainage of the mediastinum or pleural cavity through suture line defects, has been used in our department with eight patients. METHODS: A suction tube was advanced over an endoscopically placed guide wire into the abscess from inside the esophagus, and gentle aspiration was used to remove saliva and secretions. Intravenous antibiotics and total parenteral nutrition were also given. RESULTS: The sepsis was rapidly controlled, and the abscess cavity progressively collapsed in all cases. Seven patients recovered and were discharged 34 to 61 days after operation; one died of concomitant complications. CONCLUSIONS: This method seems promising for the management of intrathoracic esophageal leaks.

Restaging of patients with ovarian carcinoma.

Sixty-four patients, 34 with no clinical evidence of disease (NED) and 30 with clinical evidence of disease (ED), were submitted to restaging with peritoneoscopy plus diaphragmatic inspection, peritoneal cytology, and lymphography. Eleven patients (32.2%) in the NED group and 25 (83.3%) in the ED group had positive restaging findings. The 3 diagnostic procedures, in combination, are important in establishing occult disease and therefore in the planning of further treatment.

Comparative analysis of results of guaiac and immunochemical tests for faecal occult blood in colorectal cancer screening in two oncological institutions.

The performances of three faecal occult blood tests, rehydrated Hemoccult (HOR), Hemoccult sensa (HOS) and Hemeselect (HSEL) on 3 days were compared in 1,725 subjects consecutively recruited in two oncological institutions in Milan and Florence. Significant differences between the results were evident as far as HOR positivity rates (7.5% vs 4.0%, respectively) and specificity (94.3% vs 97.5%, respectively) are concerned. Overall positivity rates of HOR, HOS and HSEL were 5.9%, 5.4% and 12%, respectively; significant differences were evident between HSEL and each of the two guaiac tests. Cancer was detected in eight subjects, adenoma/s in 47. Specificity estimates were 95.8%, 90.2% and 90.5% for HOR, HOS and HSEL, respectively; significant differences were evident between HSEL and the other two tests. No significant difference between tests was evident for sensitivity or positive predictive values for cancer or adenomas. In the CSPO (Florence) population (1,223 subjects; five with cancer, 16 with adenoma/s) the performances of 1-day HSEL testing were determined on the basis of the first faecal sample only and compared with 3-day HOR, HOS and HSEL testing. The positivity rates of 1-day HSEL, 3-day HOR, HOS and HSEL testing were 7.0%, 5.0%, 5.5% and 12.9%, respectively. Only 3-day HSEL positivity rate was significantly higher than 1-day HSEL. One-day HSEL specificity (94.9%) was significantly higher than 3-day HSEL (90.0%), whereas no significant difference was seen between 1-day HSEL, HOR (96.5%), and HOS (96.1%) specificity. No significant difference between tests is evident in the CSPO population as far as positive predictive values and sensitivity for cancer and adenomas are concerned.(ABSTRACT TRUNCATED AT 250 WORDS)

Congenital hypertrophy of retinal pigment epithelium (CHRPE) as a marker for familial adenomatous polyposis (FAP).

Seventy-eight patients from 26 families were examined to evaluate the potentiality of congenital hypertrophy of retinal pigment epithelium (CHRPE) as a phenotypic marker for familial adenomatous polyposis (FAP). The examined subjects were divided into three different groups: Group I, patients with FAP without extra colonic manifestations (ECM); Group II, patients with FAP and ECM (desmoids/osteomas/upper gastrointestinal adenomas); and Group III, individuals at risk without FAP. Of 24 Group I patients (median age 18 years) 16 had CHRPE compared with 14 out of 24 patients (median age 29 years) in Group II and only three out of 30 patients in Group III. The overall sensitivity of CHRPE for FAP was 70% (+/- 13%) without any difference related to ECM; the predictive value was 92%. The specificity calculated from Group III (median age 26 years) was 90%, but the results should not be considered as definitive because a longer follow-up to determine the appearance of adenomas is required. The data suggest that examination for CHRPE is an inexpensive, non-invasive test for FAP, but the absence of retinal lesions does not eliminate the necessity for adequate follow-up of individuals at risk.

Determinants of Helicobacter pylori seroprevalence among Italian blood donors.

BACKGROUND/AIM: Helicobacter pylori is a worldwide infection. It is estimated that approximately 50% of the general population is affected, but this percentage varies considerably between countries. To investigate the prevalence of H. pylori infection, a cross-sectional epidemiological study, based on the serological determination of the IgG antibodies against H. pylori, was carried out in healthy Italian blood donors by using a commercially available kit. METHODS: From March 1995 to March 1997, a total of 2598 consecutive volunteer blood donors were tested for the presence of antibodies against H. pylori. All patients answered a detailed questionnaire which collected sociodemographic characteristics, and smoking, alcohol drinking and dietary habits. Test-positive subjects with gastrointestinal symptoms underwent endoscopy, with biopsies taken for histological diagnosis. RESULTS: The global prevalence of H. pylori infection in our study was 1161/2598 (45%). It was directly correlated with age (67% in subjects aged > or = 50 years). The prevalence of H. pylori infection was higher in men (46.4%) than women (38.4%), and more frequent in patients with a low educational level, in the lower quintile of height and in the upper quintile of body mass index (BMI). No significant association with smoking and alcohol drinking was found. Inverse associations were found with elevated consumption of milk (chi-square for trend 5.49, P < 0.05), but not other examined food groups. Multivariate analysis selected sex, age, BMI and educational level as the variables independently related to H. pylori infection. CONCLUSION: This study confirms relatively high prevalence of H. pylori seropositivity among Italian healthy adults and points to sex, age, BMI and sociocultural class as persisting determinant features of H. pylori infection.

Botulinum toxin type A (Dysport) for the treatment of Zenker's diverticulum.

The standard treatment for Zenker's diverticulum (ZD) is surgical, but transendoscopic section of the diverticular spur has also been performed with good results. We treated two patients with the injection of 300-350 IU of botulinum toxin type A (Dysport) into the diverticular spur. Both patients were dysphagic because of a large ZD. A few hours after the treatment, the patients were able to return to a normal, nonrestricted diet. They remain symptom-free 12 and 3 months later, respectively. No complications have been observed. As a result of its ease of application and efficacy, this treatment can be recommended for patients who are unable to undergo the surgical operations; it can be considered a valid alternative to the other endoscopic procedures.

Light-induced fluorescence spectroscopy of adenomas, adenocarcinomas and non-neoplastic mucosa in human colon. I. In vitro measurements.

In an attempt to evaluate whether induced fluorescence could be exploited to discriminate neoplastic from non-neoplastic tissue, fluorescence spectroscopy was performed at 450-800 nm on 83 biopsy specimens of colonic mucosa. Measurements showed that fluorescence spectra of adenoma, adenocarcinoma and non-neoplastic mucosa manifest dissimilar patterns. Nine variables, whose photophysical and/or biological bases need further investigation, were derived from the spectra. Discriminant functions between the groups of lesions were determined by using a stepwise discriminant analysis. The diagnostic test had a sensitivity of 80.6% and 88.2%, and a specificity of 90.5% and 95.2% in discriminating neoplastic from non-neoplastic mucosa and adenoma from non-neoplastic mucosa respectively. These results suggest that fluorescence spectroscopy has the potential to improve endoscopic diagnosis of premalignant and malignant lesions of colonic mucosa.

Paldimycins A and B and antibiotics 273a2 alpha and 273a2 beta. Synthesis and characterization.

Paldimycin (antibiotic 273a1) and antibiotic 273a2 as well as their individual components, paldimycins A (273a1 alpha) and B (273a1 beta) and antibiotics 273a2 alpha and 273a2 beta were synthesized from paulomycin, paulomycin A and paulomycin B, respectively, by reacting with N-acetyl-L-cysteine. The semisynthetic antibiotics had chromatographic behavior (TLC, HPLC) and physical and chemical properties identical to the properties of the corresponding antibiotics produced by Streptomyces paulus.

Absorption and excretion of cobalt in the hard metal industry.

Absorption and excretion of cobalt in the hard metal industry was investigated by means of ambient air and urine measurements in three factories with high levels of environmental cobalt pollution. In the presence of poor hygiene conditions and permission to smoking during work, there was no relationship between cobalt ambient air and cobalt urine concentrations. Such a finding was therefore attributed to a substantial skin contact. A simple experiment of skin exposure to freshly mixed or waste powder on volunteers identified a ten-fold increase of cobalt in urine in the post-exposure samples, thus confirming the contribution of dermal exposure as a route of entry. An improvement in the hygiene of the working conditions helped to investigate the relationship between exposure and excretion level. Cobalt uptake through the different routes of entry may be substantial, and requires a more prolonged exposure-free period so that the excretion rate can be reduced to the reference population level.