High-Tc bolometers with silicon-nitride spiderwebsuspension for far-infrared detection

High-Tc GdBa2Cu3O7-δ (GBCO) superconducting transition edge bolometers with operating temperatures near 90 K have been made with both closed silicon-nitride membranes and patterned silicon-nitride (SiN) spiderweb-like suspension structures. As a substrate silicon-on-nitride (SON) wafers are used which are made by fusion bonding of a silicon wafer to a silicon wafer with a silicon-nitride top layer. The resulting monocrystalline silicon top layer on the silicon-nitride membranes enables the epitaxial growth of GBCO. By patterning the silicon-nitride the thermal conductance G is reduced from about 20 to 3 μW/K. The noise of both types of bolometers is dominated by the intrinsic noise from phonon fluctuations in the thermal conductance G. The optical efficiency in the far infrared is about 75% due to a goldblack absorption layer. The noise equivalent power NEP for FIR detection is 1.8 pW/√Hz, and the detectivity D* is 5.4×1010 cm √Hz/W. Time constants are 0.1 and 0.6 s, for the closed membrane and the spiderweb like bolometers respectively. The effective time constant can be reduced with about a factor 3 by using voltage bias. Further reduction necessarily results in an increase of the NEP due to the 1/f noise of the superconductor

Selenium and other trace elements in the etiology of Parkinson’s disease: a systematic review and meta-analysis of case-control studies

.INTRODUCTION Parkinson’s disease (PD) is a neurodegenerative illness recognised as the most common neurological disorder after Alzheimer’s dementia. Whereas the exact PD etiology remains unknown, risk of developing PD seems to be related to an interrelation of genetic and environmental factors, including also altered exposure to trace elements. In this systematic review and meta-analysis, we updated and summarized the results of epidemiologic case-control studies comparing levels of selenium, copper, iron and zinc in PD patients with healthy subjects in either blood (as whole blood, serum or plasma) and cerebrospinal fluid (CSF). MATERIALS AND METHODS We performed a systematic PubMed search and we included in our assessment only studies reporting demographic and disease-related characteristics, as well as trace element levels in different specimens (whole blood, serum/plasma and CSF). We then performed a meta-analysis of mean differences of trace element levels between cases and controls, using a random-effect model computing the weighted mean differences (WMD) and corresponding 95% confidence intervals (CI) to assess the association between serum/plasma, whole blood, CSF and selenium, copper, iron and zinc with Parkinson’s disease. RESULTS We retrieved 55 papers reporting data for selenium (588 cases and 721 controls), copper (2190 and 2522), iron (2843 and 3434), and zinc (1798 and 1913). Cases showed higher levels of selenium in CSF compared with controls (WMD=5.49; 95%CI 2.82 to 8.15), while levels in serum were similar (WMD=-0.22; -8.05 to 7.62). For copper cases showed higher levels in CSF and lower in serum compared to controls (WMD=1.87; -3.59 to 7.33, and -42.79, -134.35 to 48.76 respectively). Same results were found for iron in CSF (WMD=6.54; -1.97 to 15.04) and in serum/plasma (WMD=-58.19; -106.49 to -9.89 and whole blood (WMD=-95.69; 157.73 to -33.65). On the converse, cases had lower levels of zinc both in CSF (WMD=-7.34; -14.82 to 0.14) and serum/plasma (WMD=-79.93; -143.80 to -16.06). CONCLUSIONS Results of this systematic review and meta-analysis suggests that overexposure to environmental selenium, copper and iron may be risk factors for PD onset or progression. Alternatively, some variation in levels of these trace elements may occur as a consequence of the disease. Considering the burden of PD in the world population, further investigation of trace element exposure in this disease is therefore warranted, especially to plan possible prevention measures

Selenium and Other Trace Elements in the Etiology of Parkinson's Disease: A Systematic Review and Meta-Analysis of Case-Control Studies

Background: Parkinson's disease (PD) is the most common neurodegenerative disease after Alzheimer's dementia. Whereas the exact etiology of PD remains unknown, risk of developing PD seems to be related to a combination of genetic and environmental factors. This also includes abnormal exposure to trace elements of nutritional and toxicological interest. Objectives: In this systematic review and meta-Analysis, we summarized the results of case-control studies comparing levels of selenium, copper, iron, and zinc in PD patients and controls in either blood (whole blood, serum/plasma) or cerebrospinal fluid (CSF). Methods: We performed a systematic PubMed search selecting studies reporting trace element levels in different specimens of patients and controls. We performed a meta-Analysis using a random-effect model to compute the weighted mean differences (WMD) and corresponding 95% CI of selenium, copper, iron, and zinc levels in the blood or CSF of patients and their matched controls. Results: We retrieved 56 papers reporting data for selenium (cases/controls: 588/721), copper (2,190/2,522), iron (2,956/3,469), and zinc (1,798/1,913) contents in CSF and blood. Cases showed considerably higher levels of selenium in CSF compared with controls (+51.6%; WMD 5.49; 95% CI 2.82 to 8.15), while levels in serum were similar (-0.2%; WMD-0.22; 95% CI-8.05 to 7.62). For copper, cases showed slightly higher levels in CSF and slightly lower concentrations in serum (+4.5%; WMD 1.87; 95% CI-3.59 to 7.33, and-4.5%; WMD-42.79; 95% CI-134.35 to 48.76, respectively). A slight increase was also found for CSF iron-levels (+9.5%; WMD 9.92; 1.23 to 18.61), while levels were-decreased in serum/plasma (-5.7%; WMD-58.19; 95% CI-106.49 to-9.89) and whole blood (-10.8%; WMD-95.69; 95% CI-157.73 to-33.65). Conversely, for zinc cases exhibited lower levels both in CSF (-10.8%; WMD-7.34; 95% CI-14.82 to 0.14) and serum/plasma (-7.5%; WMD-79.93; 95% CI-143.80 to-16.06). A longer duration of the disease tends to be associated with overall lower trace element levels in either CSF or blood. Conclusions: Due to the study findings and the greater relevance of the CSF compartment compared with the circulating peripheral ones, this meta-Analysis suggests that overexposure in the central nervous system to selenium, and possibly to copper and iron, may be a risk factor of the disease, while zinc might have a protective-effect

Total antioxidant activity and trace elements in human milk: the first 4 months of breast-feeding

The content of many nutrients in breast milk are dependent on the nutritional status of the lactating woman. This is particularly true for fat and water-soluble vitamins, some of which have antioxidant properties. The aim of the study entertained herein was to evaluate the changes in total antioxidant status of human milk during the first 4 months of lactation, and to correlate such changes with the contents in specific antioxidant oligoelements (Cu, Zn, Mn and Se). Milk samples were collected from (31) lactating women recruited at the Service of Obstetrics of the Hospital de São João in Porto, after 1, 4, 8, 12 and 16 weeks after birth. The total antioxidant status (TAS) of human milk was measured by the Randox® commercial kit and trace metals by ICP-MS (inductively coupled plasma-mass spectrometry). The results found for TAS and oligoelements under study show a decrease in the concentration of these parameters from 7 days to 4 months of breast-feeding and significant correlations (p < 0.05) were found between TAS and Cu, Zn and Se (not Mn). The decreases of Cu, Zn and Se were also correlated, but not proportional between them, suggesting diverse excretion mechanisms for all. Between primipara and multipara women, a significant difference was found only for Cu and Zn concentrations at 7 days of lactation, but not for the other metals or TAS. With respect to the mother’s age, no correlation was found, either for trace metal concentrations or TAS

Correlation between cadmium and selenium blood levels in an Italian population.

Correlation between cadmium and selenium blood levels in an Italian population

Adherence to the Mediterranean-DASH Intervention for Neurodegenerative Delay (MIND) diet and exposure to selenium species: A cross-sectional study

Selenium is a trace element found in many chemical forms. Selenium and its species have nutritional and toxicologic properties, some of which may play a role in the etiology of neurological disease. We hypothesized that adherence to the Mediterranean-Dietary Approach to Stop Hypertension Intervention for Neurodegenerative Delay (MIND) diet could influence intake and endogenous concentrations of selenium and selenium species, thus contributing to the beneficial effects of this dietary pattern. We carried out a cross-sectional study of 137 non-smoking blood donors (75 females and 62 males) from the Reggio Emilia province, Northern Italy. We assessed MIND diet adherence using a semiquantitative food frequency questionnaire. We assessed selenium exposure through dietary intake and measurement of urinary and serum concentrations, including speciation of selenium compound in serum. We fitted non-linear spline-based regression models to investigate the association between MIND diet adherence and selenium exposure concentrations. Adherence to the MIND diet was positively associated with dietary selenium intake and urinary selenium excretion, whereas it was inversely associated with serum concentrations of overall selenium and organic selenium, including serum selenoprotein P-bound selenium, the most abundant circulating chemical form of the metalloid. MIND diet adherence also showed an inverted U-shaped relation with inorganic selenium and particularly with its hexavalent form, selenate. Our results suggest that greater adherence to the MIND diet is non-linearly associated with lower circulating concentrations of selenium and of 2 potentially neurotoxic species of this element, selenoprotein P and selenate. This may explain why adherence to the MIND dietary pattern may reduce cognitive decline

Low noise far-infrared detection at 90 K using high-T(c) superconducting bolometers with silicon-nitride beam suspension

High-T(c) GdBa2Cu3O7-d (GBCO) superconducting transition edge bolometers with operating temperatures near 90 K and receiving area of 1 mm2 have been made with both closed silicon-nitride membranes and patterned silicon-nitride (Si(x)N(y)) spiderweb-like suspension structures. To enable epitaxial growth of the GBCO layer, a thin monocrystalline Si layer is prepared on the silicon-nitride base, using fusion bonding techniques. By pattering the silicon-nitride supporting membrane the thermal conductance G is reduced from 20 to 3.5 μW/K. The noise of both types of bolometers is fully dominated by the intrinsic noise from phonon fluctuations in the thermal conductance G. The optical efficiency in the far infrared is about 75% due to a gold black absorption layer. The optical noise equivalent power (NEP) is 1.8 pW/√Hz, and the detectivity D* is 5.4x1010 cm√Hz/W. Time constants are 0.1 and 0.6 s, for the closed membrane and the spiderweb like bolometers respectively. We have observed an empirical limit for the NEP for this type of bolometers. The effective timeconstant can be reduced with a factor of 3 by using an electronic feedback system or by using voltage bias. A further reduction necessarily results in an increase of the NEP due to the 1/f noise of the superconductor