Perfect Gold Research Articles

Synthesis, Properties, and Biological Application of Perfect Crystal Gold Nanowires: A Review

In the last decade, numerous kinds of nanoscale materials have been created. Their characteristics are critically influenced by their synthetic or fabrication methods. In this review article, we introduce perfect crystal gold nanowires (Au NWs) synthesized by vapor transport method and summarize their material properties and biological applications. Single-crystalline Au NWs having no defects or twins show unique mechanical, electrical, and electrochemical characteristics. Notably, they are exceptionally competent in penetrating cells or tissues with minimum biological damage and in the electrical analysis and manipulation of biological activities in the cells and/or tissues. It is expected that the Au NWs would give us technological breakthrough in diverse applications such as nanoscale functional components as well as new insights in fundamental material science.

Magnetic dipole radiation tailored by substrates: numerical investigation.

Nanoparticles of high refractive index materials can possess strong magnetic polarizabilities and give rise to artificial magnetism in the optical spectral range. While the response of individual dielectric or metal spherical particles can be described analytically via multipole decomposition in the Mie series, the influence of substrates, in many cases present in experimental observations, requires different approaches. Here, the comprehensive numerical studies of the influence of a substrate on the spectral response of high-index dielectric nanoparticles were performed. In particular, glass, perfect electric conductor, gold, and hyperbolic metamaterial substrates were investigated. Optical properties of nanoparticles were characterized via scattering cross-section spectra, electric field profiles, and induced electric and magnetic moments. The presence of substrates was shown to have significant impact on particle's magnetic resonances and resonant scattering cross-sections. Variation of substrate material provides an additional degree of freedom in tailoring optical properties of magnetic multipoles, important in many applications.

Michael Maier — Nine Newly Discovered Letters

The authors provide a transcription, translation, and evaluation of nine newly discovered letters from the alchemist Michael Maier (1568–1622) to Gebhardt Johann von Alvensleben (1576–1631), a noble landholder in the vicinity of Magdeburg. Stemming from the final year of his life, this correspondence casts new light on Maier's biography, detailing his efforts to secure patronage amid the financial crisis of the early Thirty Years’ War. While his ill-fated quest to perfect potable gold continued to form the central focus of his patronage suits, Maier also offered his services in several arts that he had condemned in his printed works, namely astrology and “supernatural” magic. Remarks concerning his previously unknown acquaintance with Heinrich Khunrath call for a re-evaluation of Maier's negotiation of the discursive boundaries between Lutheran orthodoxy and Paracelsianism. The letters also reveal Maier's substantial contribution to a work previously ascribed solely to the English alchemist Francis Anthony.

Sendivogius in Sweden: Elias Artista and the Fratres roris cocti

‭The Polish adept Michael Sendivogius had a definite influence in Queen Christina’s Sweden through the botanist Johannes Franck’s alchemical allegory “Colloquium with Mountain Gods” (1651). It describes the genealogy of generations of a royal family that finally bring forth the daughter Aurelia aurea - the perfect gold. Sendivogius’ work with boiling heavenly dew is implied and described as working “de rore coeli”. Franck also sees Sendivogius’ prophecy of a new metallic monarchy in the North as the coming of Elias Artista. In 1639, the “Fratres roris cocti” were said to have used a play on the word LVX from the sixteenth theorem in John Dee’s Monas Hieroglyphica (1564) as constructed out of X – St. Andrew's cross. The Dane Olaus Borrichius noted the wordplay and explained that F.R.C. would thus be the mark of the “brothers of boiled dew” and a sign for the Rose Cross.‬

The fire assay reloaded

The fire assay process is still the most accurate and precise method for measuring the gold content in gold alloys. Scanning electron microscopy and transmission electron microscopy have been applied to observe the change in microstructure of the samples undergoing the fire assay process. The performed observations reveal that the microstructure of the specimen is more complex than expected. Before the parting stage, the specimen is not a perfect gold–silver binary alloy but contains also copper–silver oxides and other residual compounds. The parting stage appears to be a dealloying process leading to a nanoporous gold nanostructure. What observed after partition explains the evolution of the shape and colour of the specimen and may allow for a better comprehension of the procedure and an improvement in the method.

Theoretical Study of CO Adsorption on Perfect and Defective Gold Surfaces

The activities of Au(111), Au(100) and Au(110) surfaces, as well as the activity of an Au adatom on Au(111), Au(100) and Au(110) surfaces have been characterized by density functional theory using CO as a probe. The results clearly show that the activity of Au surfaces towards CO adsorption is attributable to the presence of low-coordinated gold atoms to which the molecule binds. The results may enrich the understanding of CO adsorption on Au surfaces.

Considerations underlying the use of mixed group validation.

Mixed Group Validation (MGV) is an approach for estimating the diagnostic accuracy of tests. MGV is a promising alternative to the more commonly used Known Groups Validation (KGV) approach for estimating diagnostic accuracy. The advantage of MGV lies in the fact that the approach does not require a perfect external validity criterion or gold standard. However, the research designs where MGV is most appropriate have not been thoroughly explored. We give a brief description of the ideal research design to minimize error for MGV studies, test whether the MGV assumptions hold with clinical data, evaluate whether there is evidence of assumption violation among published MGV studies, give a practical description of the MGV assumptions, and describe an example of an optimal use of MGV. Ultimately, we conclude that MGV is not generally superior to KGV but may be used in some cases where the assumptions and standard error have been considered appropriately.

Latent-Class Methods to Evaluate Diagnostics Tests for Echinococcus Infections in Dogs

BackgroundThe diagnosis of canine echinococcosis can be a challenge in surveillance studies because there is no perfect gold standard that can be used routinely. However, unknown test specificities and sensitivities can be overcome using latent-class analysis with appropriate data.MethodologyWe utilised a set of faecal and purge samples used previously to explore the epidemiology of canine echinococcosis on the Tibetan plateau. Previously only the purge results were reported and analysed in a largely deterministic way. In the present study, additional diagnostic tests of copro-PCR and copro-antigen ELISA were undertaken on the faecal samples. This enabled a Bayesian analysis in a latent-class model to examine the diagnostic performance of a genus specific copro-antigen ELISA, species-specific copro-PCR and arecoline purgation. Potential covariates including co-infection with Taenia, age and sex of the dog were also explored. The dependence structure of these diagnostic tests could also be analysed.Principle findingsThe most parsimonious result, indicated by deviance-information criteria, suggested that co-infection with Taenia spp. was a significant covariate with the Echinococcus infection. The copro-PCRs had estimated sensitivities of 89% and 84% respectively for the diagnoses of Echinococcus multilocularis and E. granulosus. The specificities for the copro-PCR were estimated at 93 and 83% respectively. Copro-antigen ELISA had sensitivities of 55 and 57% for the diagnosis of E. multilocularis and E. granulosus and specificities of 71 and 69% respectively. Arecoline purgation with an assumed specificity of 100% had estimated sensitivities of 76% and 85% respectively.SignificanceThis study also shows that incorporating diagnostic uncertainty, in other words assuming no perfect gold standard, and including potential covariates like sex or Taenia co-infection into the epidemiological analysis may give different results than if the diagnosis of infection status is assumed to be deterministic and this approach should therefore be used whenever possible.

Following Grandfather (review)

Reviewed by: Following Grandfather Jeannette Hulick Wells, Rosemary. Following Grandfather; illus. by Christopher Denise. Candlewick, 2012. 58p. ISBN 978-0-7636-5069-8 $14.99 Reviewed from galleys R Gr. 2–4. Little Jenny the mouse and her grandfather spend much of their time together, trekking around Boston and going to the beach to look for shells (especially the rare and beautiful “queen’s teacup”) while her parents run their busy restaurant. When Grandfather dies, Jenny misses him terribly—so much so that she starts following other mice that she mistakes for him (“It can’t be him, I told myself, but the pull to follow was as irresistible as the current of the sea”). The last of these “Grandfather [End Page 223] sightings” leads her to the sea where she finds “four perfect gold queen’s teacups,” which she interprets as a gentle message of love from her departed grandfather. Kids who have lost a beloved family member may certainly relate to this, and the compact page count and frequent illustrations make this accessible as a longer readaloud for younger children as well. Wells’ moving (but not overly sweet) text and Denise’s pictures both have a dreamily vintage feel to them, and the piquant textual details of Jenny’s world and soft-edged digital illustrations of adorable mice in clothing may appeal to readers who love all things miniature. Denise is particularly skilled at playing light and shadow against one another and at creating strong compositions, as in the picture of a small but robust, suspenders-wearing Grandfather playing with tinier Jenny in a shaft of sunlight in their attic home. Those who appreciate a more lyrical approach to the loss of an elder may prefer this to the more comic Alvin Ho: Allergic to Dead Bodies (BCCB 1/11). Jeannette Hulick Reviewer Copyright © 2012 The Board of Trustees of the University of Illinois

Performances of Elasto-FibroTest®, a combination between FibroTest® and liver stiffness measurements for assessing the stage of liver fibrosis in patients with chronic hepatitis C

FibroTest(®) (FT), and liver stiffness measurement (LSM) are the most validated techniques for the non-invasive assessment of fibrosis in patients with chronic hepatitis C (CHC). The combination between FibroTest(®) and LSM has never been assessed using methods assuming that biopsy is not a perfect gold standard. The aim was to assess the performance of a new test the Elasto-FibroTest(®) (EFT) combining FibroTest(®) and LSM. An integrated data base of 1289 patients with biopsy and 604 healthy volunteers was analyzed. EFT took into account the applicability of both tests, included two algorithms taking one for the diagnosis of advanced fibrosis (EFT-F2) and one for the diagnosis of cirrhosis (EFT-F4). Performances of EFTs were assessed by three methods: area under the ROC curve (AUROC), "Obuchowski method" (OBU) and 1 TAGS the "Latent class with random factor". For the diagnosis of advanced fibrosis EFT-F2 performances (specificity=0.99 and sensitivity=0.83) were not greater than the performances of FibroTest(®) alone (specificity=0.93 and sensitivity=0.99). For the diagnosis of cirrhosis, EFT-F4 performances were greater than those of FibroTest(®) alone, particularly for the sensitivity (0.88 vs. 0.74); when compared with LSM, EFT-F4 performances (specificity=0.99 and sensitivity=0.99) were also greater than those of LSM alone particularly because of its lower specificity (0.92). For the diagnosis of cirrhosis the Elasto-FibroTest(®) has higher performances than FibroTest(®) or FibroScan(®) alone. No improvement in performance has been observed for the diagnosis of advanced fibrosis vs. FibroTest(®) alone.

The Accuracy of the Single Intradermal Comparative Skin Test for the Diagnosis of Bovine Tuberculosis-Estimated from a Systematic Literature Search

Background: Bovine Tuberculosis (bTN) elimination programs are based on test-and-slaughter strategies. No diagnostic test used in the control of Bovine Tuberculosis (bTB), a zoonotic disease, is a perfect gold standard having a diagnostic sensitivity and specificity of 100%. Methods: To find relevant data to assess diagnostic accuracy of one variant of the tuberculin test, the Single Intradermal Comparative Cervical Tuberculin Test (SICCT) used in the diagnosis of bTB a systematic literature search was performed. To estimate diagnostic test accuracies of the SICCT, a Bayesian latent class analysis has been undertaken. Results: Only one eligible study was found. Assuming bacterial isolation has a specificity of 100%, specificity of gross lesion detection and histopathology were estimated as 90% and 97% respectively. Estimates of the sensitivity of the Single Intradermal Comparative Cervical Tuberculin Test (SICCT), gross lesion detection, histopathology and bacteriological isolation were 80%, 89%, 93% and 98% respectively. The design of this study precluded estimating the SICCT specificity, although official UK surveillance data indicates specificity greater than 99.67%. Conclusion: Studies to estimate the diagnostic performance of key tests for bTB are lacking, yet essential for an informed debate in regard to bTB public health policy.

The Risk of Multiplying Diagnostic Combinations in the Absence of a Perfect Gold Standard For a Fibrosis Test

Munteanu, Mona MD1; Ratziu, Vlad MD, PhD2; Poynard, Thierry MD, PhD2 Author Information

An Application of a Bayesian Approach in Diagnostic Testing Problems in the Absence of a Gold Standard

A number of methods have been proposed to estimate the parameters of diagnostic tests in the absence of a perfect gold standard. However, these approaches require at least three diagnostic tests to estimate the parameters and most of these methods are inapplicable in point estimation problems involving nonidentifiable parameters. In this article, we describe a method to estimate the properties of various tests for Chlamydia trachomatis. A general approach has been presented to select a range of suitable prior distributions for the diagnostic testing situation required by the Bayesian approach, and the results from this method are compared with those obtained from other methods in context to the Chlamydia example. The effects of different classes of prior distribution such as skeptical, optimistic, and clinical priors on the estimates of the parameters are demonstrated.

Air Plasma Assisting Microcontact Deprinting and Printing for Gold Thin Film and PDMS Patterns

In this paper, we present a simple method to fabricate gold film patterns and PDMS patterns by air plasma assisting microcontact deprinting and printing transfer approaches. Chemical gold plating is employed instead of conventional metal evaporation or sputtering to obtain perfect gold film both on flat and topographic PDMS chips, and complicated SAM precoating is replaced by simple air plasma treatment to activate both the surface of gold film and PDMS. In this way, large area patterns of conductive gold film and PDMS patterns could be easily obtained on the elastomeric PDMS substrate. Both the chemical plating gold film and transferred gold film were of good electrochemical properties and similar hydrophilicity with smooth and conductive surface, which made it potentially useful in microfluidic devices and electronics. The gold transfer mechanism is discussed in detail. For typical applications, a cell patterning chip based on the gold pattern was developed to imply the interfacial property, and dielectrophoresis control of live cells was carried out with the patterned gold as interdigital electrodes to show the conductivity.

Echinococcosis: diagnosis and diagnostic interpretation in population studies

Diagnosis is a basic component of population studies on echinococcosis. Other than careful necropsy in animals, there is no perfect gold standard. In the definitive host, techniques for direct parasite identification include copro-antigen and copro-DNA detection. In intermediate hosts, necropsy is typically used. In humans, diagnostic imaging and serology are both widely employed. The use of multiple parallel testing or an additional confirmatory test (or tests) in a diagnostic strategy can overcome the lack of a perfect gold standard. This will yield valuable information at population and individual levels, providing the study is well designed and any shortcomings of the tests are incorporated into the analysis. Here, we discuss analytical approaches to population studies of echinococcosis.

New Single Molecular Detection System from Three-Dimensional Tracking of Single Nanocrystals using Scanning Electron Microscope

Recent technological progress in dynamical observations of individual functional single protein molecules in living cell has been achieved with several single molecular techniques and systems. In order to improve monitoring precisions and stability of the signal intensity from single molecular units under physiological conditions, we have proposed that single molecular techniques using shorten wavelength, for example, X-rays, electrons, neutron, and other accelerated ion probes. In this work, we demonstrate three-dimensional tracking of single nanocrystals using Scanning Electron Microscope. We called Diffracted Electron Tracking (DET).Diffracted X-Ray tracking (DXT) [1] has been developed for obtaining the information about the dynamics of single molecules. This method can observe the rotating motion of an individual nanocrystal, which is linked to specific sites in single protein molecules, using a time-resolved Laue diffraction technique. This method needs a very strong X-ray source, such as the SPring-8, so we began to develop a compact instrument for monitoring the rotation of the single protein molecules, using the electron beam instead of the X-ray.Instead of the Laue diffraction using white X-ray, the Electron Back-Scattered Diffraction Pattern (EBSP) is adopted to monitor the crystal orientation of the nano-crystals linked to the single protein molecules. For this purpose, it is necessary to realize (1) wet cell with very thin sealing film, (2) EBSP system with high sensitivity, (3) damage-less electron irradiation technique and (4) perfect gold nano-crystals.[1] H. Shimizu, M. Iwamoto, F. Inoue, T. Konno, Y.C. Sasaki, S. Oiki: Cell 132, 67-78 (2008).[2] T.Sagawa, T.Azuma, Y. C. Sasaki, Biochem. Biophy. Res. Commun. 335, 770-775 (2007).

C60 on Gold: Adsorption, Motion, and Viscosity

In the thick of it: C60 spins rapidly in the solid but just how viscous is its motion on a perfect gold surface? Molecular dynamics simulations of C60 on a gold surface (see image) show the presence of a variety of molecular motions, where the entire cage spins and bounces on the surface. Two motions, namely the cage bouncing on the surface and the intercage rattling, govern the tribological properties of the system that are quantitatively similar to those of melt polymers.

Evaluation of three serological tests for brucellosis in naturally infected cattle using latent class analysis

Serological methods are traditionally used in diagnosis of brucellosis. However, the comparative performance of these tests and their accuracy under the local environment in Zambia has not been assessed. Thus, the objective of our study was to evaluate the diagnostic performance of three serological tests for brucellosis; Rose Bengal Test (RBT), competitive ELISA (c-ELISA) and Fluorescence Polarisation Assay (FPA) in naturally infected cattle in Zambia without an appropriate reference test to classify animals into truly infected and non-infected. Serological test results from a study to determine sero-prevalence were used to compare the performance of RBT, c-ELISA and FPA in diagnosing brucellosis in traditional cattle. Since none of the tests can be seen as a perfect reference test or gold standard, their performance in a population of naturally infected cattle was evaluated using latent class analysis which allows the sensitivity (Se) and specificity (Sp) to be estimated in the absence of a gold standard. The highest Se was achieved by the c-ELISA (97%; Credible Posterior Interval (CPI) = 93–100%) and the highest Sp by the FPA (93%; CPI = 85–99%), conversely these tests also had the lowest Sp and Se, respectively, with the RBT performing well in both the Se (93%; CPI = 84–98%) and Sp (81%; CPI = 61–97).

String Capsule Endoscopy Has Better Sensitivity/Specificity Than Conventional EGD for the Diagnosis of Barrettʼs Esophagus. A Prospective Blinded Study

Purpose: EGD is the gold standard visual diagnostic test for Barrett's esophagus but is not the perfect gold standard when compared to the histological diagnosis. Aims: To compare the sensitivity, specificity, positive-, and negative-predictive values of String Capsule Endoscopy to conventional EGD when using histological diagnosis as the gold standard for Barrett's esophagus Methods: Patients undergoing EGD for the first time for the evaluation of reflux symptoms and/or screening for Barrett's esophagus underwent String Capsule Endoscopy (SCE) prior to their EGD on the same day. At least 4 biopsies were systematically taken from the squamous-columnar junction and/or the suspected Barrett's segment during EGD. IRB- approved protocol Independent endoscopist unaware of EGD diagnosis reviewed capsule endoscopy pictures and indicated if Barrett's esophagus was suspected or not. SCE was performed using the conventional small bowel capsule modified with a sleeve and “string” prior to the EGD, in the sitting position and without any local or systemic analgesia/sedation. EGD was performed using conscious sedation Sensitivity, specificity, positive and negative predictive values were calculated for SCE and EGD against histological diagnosis. The capsule underwent high-grade disinfection (2% gluteraldehyde for 45 minutes) and re-used after its retrieval from each patient. Patients were asked to indicate their preference: EGD versus SCE Results: 58 patients, all except 9 were men; mean age: 57.6 yrs. Strings remained in place without rupture/displacement and no capsule was lost. Average recording time: 6.03 min (EGD: 6.78 min). SCE was well tolerated, 81% patients preferred SCE over EGD. BE was suspected visually in 31 (53.4%) and 30 (51.7%) patients with EGD and SCE, respectively. Intestinal metaplasia was found in 21 patients (36.2%). The sensitivity, specificity, PPV and, NPV of EGD and SCE when using intestinal metaplasia as the gold standard are shown below Conclusions: This study suggests that SCE has better sensitivity, specificity, PPV and NPV than conventional EGD for the diagnosis of Barrett's esophagus when intestinal metaplasia was used as the gold standard. A larger sample size is needed to assess for statistical significance. SCE was safe and the preferred method in patients undergoing screening for Barrett's esophagus.Table. EGD: vs. SCE When Using Intestinal Metaplasia as Gold Standard

Effects of Polymer Micelles of Alkylated Polyethylenimines on Generation of Gold Nanoparticles

Mono- and di-alkylated polyethylenimines (PEI-1R, PEI-2R) were synthesized and used as both reductants, by exploiting the functionality of the polyethylenimine's (PEI) amino groups, and stabilizers able to protect nascent gold nanoparticles generated from hydrogen tetrachloroaurate (HAuCl4). From TEM images of the stained polymers, it is clear that the polymer micelles are round and well-structured when formed from PEI-2R, fused and less well-structured when formed from PEI-1R, and totally nonstructured when formed from PEI. These findings coincide with the results found by using pyrene as a probe to investigate aggregation behavior, where PEI-2R with a fluorescence intensity ratio (I1/I3) of 1.48 forms the more closely packed polymer micelles than PEI-1R (I1/I3 = 1.64) and PEI (I1/I3 = 1.72). The use of the highly alkylated polymer micelle (PEI-2R) results in the fastest reduction of HAuCl4, and gives the most effective protection to the generated gold nanoparticles. When used at higher polymer concentrations than required for micelle formation, it was found that polymer hydrophobicity was highly influential in directing the nanoparticle's morphology, i.e., the resulting polymer micelles were labeled with perfect and round necklace-like gold nanoparticles when PEI-2R was used, and imperfect and less round gold nanoparticles when PEI-1R was employed. These structures were totally absent when PEI was used. The use of alkylated PEI, being able to act simultaneously as both a reductant and as a very effective protective agent, greatly simplifies the process used for preparing gold nanoparticles.