Multilabeling biomolecules at a single site. 1. Synthesis and characterization of a dendritic label for electrochemiluminescence assays

Ultrasensitive bioanalytical assays are of great value for early detection of human diseases and pathogens. The sensitivities of immunoassays and DNA probing can be enhanced by multilabeling the biorecognition partner used for affinity-based assays. However, the bioreactivity of biomolecules is affected by a high degree of multilabeling at multiple functional sites. It is proposed that dendritic scaffoldings be used to link multiple signal-generating units to a single site with potentially minimum impact on the bioaffinity. A prototype label, a zeroth-generation dendron, bearing three [Ru(bpy)(3)](2+) units for electrochemiluminescence (ECL) assays was synthesized and characterized preliminarily by spectroscopic, electrochemical, and ECL methods. No evidence of interaction between the neighboring [Ru(bpy)(3)](2+) units in the label molecule was found from these characterizations. Both the photoluminescence and ECL of the prototype label have features very similar to those of mononuclear [Ru(bpy)(3)](2+) compounds. Labeling a model protein with a triad of [Ru(bpy)(3)](2+) at one NH(2) position was demonstrated. The results reported here provide support to applying the proposed multilabeling strategy to affinity-based bioanalytical assays.     

SIMULATION OF SPRAY DRYING WITH REACTION: ABSORPTION OF HYDROGEN SULFIDE IN AMMONIACAL SOLUTION OF ZINC CHLORIDE

Absorption of hydrogen sulfide gas in ammoniacal solution of zinc chloride is accompanied with an instantaneous chemical reaction forming zinc sulfide precipitates. Such reactions are moat suited for operation of spray drying with reaction. A mathematical model for the system which incorporates chemical reaction, heat, mass and momentum transfer has been proposed. It is assumed that the gases and the spray droplets move in co-current plug flow mode end spray is considered monodiaperse for sake of simplicity. The differential equations derived for the modal have been solved as an initial value problem uslng the Runge-Kutta method. The variations of temperature, humidity, droplet diame-ter. moisture content and concentrations of reactants are pra-dieted along the length of the column and compared with exprimental data.     

Some observations on the surface and subsurface features of failed babbitt pads

Surface and subsurface details are presented of tin-based babbitt bearing pads which have failed due three different causes; through electrical pitting in the thrust pads, thermal fatigue in a tilting pad journal bearing, or cavitation in the thrust pads. Other associated defects in these pads are also highlighted. The microscopic details of the pits reveal the different features of electrical pitting and cavitation. Thermal fatigue produces initiation of cracks and final debonding of babbitt. It has also been found that high temperature in the mating surfaces of the bearing pads during sliding causes concentration of SbSn cuboids and Cu₆Sn₅ needles in the surface zone.     

Evaluation of Calcofluor staining in the diagnosis of fungal corneal ulcer

For laboratory diagnosis of mycotic keratitis, demonstration of fungal pathogens on direct microscopy and their isolation by culture is essential. The addition of Calcofluor white (CFW) stain to the diagnostic armamentarium has significantly increased the sensitivity of smear examination on direct microscopy. During a period of 1 year, 143 consecutive patients with corneal ulcers were investigated by direct microscopy with potassium hydroxide (KOH) wet mount, Calcofluor white stain and routine cultures of corneal scrapings. Fungi were detected as aetiological agents in 21 (15%) patients. Different species of the genera Aspergillus (35%), Fusarium (23%), Acremonium (12%), Paecilomyces (12%), Cladosporium (6%), Alternaria (6%) and Pseudallescheria (6%) were the common isolates. Calcofluor white stain on direct microscopy detected fungi in 20 (95.2%) patients in comparison with 15 (71.4%) patients by both KOH wet mount examination and culture. Calcofluor white stain was significantly more sensitive than KOH wet mount in demonstrating fungal pathogens.     

Pattern recognition with generalized centroids and subcentroids

We propose a class of generalized moment functions (GMFs) that can be used to determine a set of geometric points, namely, generalized centroids (G centroids), within an object. Based on a linear GMF, a mass centroid and its subcentroids can be defined and extracted, which provide information on the location and orientation of an object. Similar to traditional moment functions, GMFs can also be used to describe the global shape of an object, including symmetry and fullness. However, GMFs, along with G centroids and subcentroids, can further serve to construct a feature vector of an object, which is critical for image registration and invariant pattern recognition. One can extract more distinguishing features from the same object by changing the combination of GMFs. We present results that show simulations of pattern recognition from uniform backgrounds.     

Using goals to design and verify rule bases

The design of rule-based systems is often plagued by errors and anomalies. The verification and validation (V and V) processes to detect errors and anomalies in a rule base are complex. Methods that are general enough for comprehensive anomaly detection suffer from heavy computation. Special methods for V and V that have reduced computational needs lack in their scope and applicability. Most of the existing verification tools perform their checking based on the syntax of rule base encoding often ignoring useful meta knowledge of the domain. In this paper, we propose a way to abstract domain knowledge using goals. At the design level, goals are realized in a rule base using one of several design schemes, where a design scheme is a goal-to-hypothesis mapping satisfying certain constraints. At the implementation level, goals are inferred using partially ordered rule sequences called paths. Verification of a rule base can be performed by identifying certain rule aberrations, that can be indicative of the rule base anomalies circularity, ambivalence, redundancy, and deficiency. A case study is presented to highlight that the goal-based approach is useful for preventing rule subsumption (a form of redundancy) and for enhancing the (run time) performance of a rule base.     

Abnormal wear of gear couplings — a case study

A number of failures occurred in the gear coupling transmitting the torque from a steam turbine (rotating at 7500 r/min) to a 1.5 MW generator through a 1 : 5 reduction gear box. Failure was found to be occurring in the form of rapid wear of teeth. Heavy wear steps were notices on both the hub and the spool pieces. Vibration measurements revealed that twice the running speed component was the most dominant frequency, with the maximum amplitude in the axial direction, indicating misalignment. Non-synchronous components appearing in the frequency spectrum revealed that rubbing was taking place. Overall vibration analysis at different locations in the assembly indicated seating problems in the bearing pedestals with the bed plate.Excessive sludge accumulation was noticed in the gear coupling. Analysis of the sludge indicated the presence of large quantities of iron oxide, water, calcium and silica. Other elements of the gear coupling material were also present. However, no deviations in the physical and chemical properties were found through analysis of oil collected from the tank. Examination of the lubrication system showed lack of proper filters and centrifuge. The shape, size and orientation of the nozzle for the oil jet to gear coupling were found to be incorrect. Ferrographic analysis of the lubricating oil revealed a large quantity of wear particles. It was concluded that the wear was due to the misalignment aided by faults in the lubrication system     

2D Tellurium Based High‐Performance All‐Optical Nonlinear Photonic Devices

Tellurium (Te), as one of the rarest stable solid elements far more common in the universe than on earth, is a p‐type semiconductor with excellent optical properties. Herein, a novel two‐dimensional (2D) Te nanosheets (Ns)‐based air‐stable nonlinear photonic devices: all‐optical switcher and photonic diode, owing to its strong light–matter interaction in the visible‐to‐infrared band are reported. The findings validate that the proposed photonic diode can be utilized for the function of nonreciprocal light propagation in optical telecommunications or integrated photonics. Moreover, 2D Te‐based light‐modulate‐light system is successfully designed to realize “ON” and “OFF” modes for all‐optical switching operation. This work highlights a good promise of 2D Te in the field of nonlinear photonics, leading to an important step toward 2D Te‐based advanced photonics devices. The versatile solution process allows a universal access of 2D Te as a new 2D material in a wider range of photonics device applications such as, detector, modulator, switcher, etc.     

Antibiotic use and the prevalence of antibiotic resistant bacteria on turkey farms

BACKGROUND: A preliminary study was undertaken to compare the prevalence of antibiotic resistance bacteria (ARB) on turkey farms using either antibiotics sub‐therapeutically (AU) or no antibiotics (NAU). Samples of manure, soil, and dog feces were collected from seven AU and six NAU farms. RESULTS: The prevalence of tetracycline resistant (TC^r) bacteria was significantly higher (P≤0.05) in manure samples from AU farms while the prevalence of monensin resistant bacteria (MON^r) was higher on the NAU farms. There was no difference in the prevalence of tylosin resistant bacteria (TYL^r) between the two types of farm. The prevalence of TC^r, TYL^r and Mon^r bacteria in soil or the prevalence of TYL^r and Mon^r bacteria in dog fecal samples from either type of farm was not significantly different. However, the prevalence of TC^r in dog fecal samples was significantly higher (P≤0.05) from NAU farms than AU farms. Escherichia coli and Pasteurella isolated from manure samples on AU farms showed higher resistance to multiple antibiotics than those isolated from NAU farms. However, there was no difference in the antibiotic susceptibility of Pseudomonas isolates in soil samples or E. coli isolates in dog fecal samples from the two types of farms. CONCLUSION: These results indicate that although the prevalence of ARB is higher in turkey manure from AU farms, its application on land does not appear to be spreading ARB to the terrestrial environment or to pets on the farm. Copyright © 2007 Society of Chemical Industry