Fundus contact lens and Hruby lens

The fundus contact lens is a much overlooked diagnostic aid that can make difficult diagnosis simple. The combination of binocular vision, great light intensity and a range of magnification powers using the fundus contact lens and the slit lamp give the practitioner an excellent resolution to view the fundus.     

Frequency selectivity in the parakeet (Melopsittacus undulatus) studied with psychophysical tuning curves.

Seven parakeets were trained to avoid shock during pure-tone stimulation. A modified method of limits was used to measure detection thresholds of the pure tones. The intensity of masker tones, at numerous frequencies, was varied to measure the masked threshold of a probe-tone signal set at a fixed frequency and intensity. Masking curves were obtained for 3 probe tones (.63, 1.6, and 2.5 kHz) at each of 5 sensation levels (10, 20, 30, 40, and 50 db). The masking curves from this procedure, which are frequently referred to as "psychophysical tuning curves," provide an indication of frequency selectivity. Results are compared with analogous data in other species and suggest that frequency analysis in the parakeet ear is somewhat less accurate than in the mammalian ear. (27 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Tensile behaviour of grass

The tensile behaviour of ryegrass (Lolium perenne L.), which was grown, harvested and tested under controlled conditions, is described. Whereas some of the grass leaf specimens behaved in a predominantly brittle manner, others evinced a semi ductile mode such that a proportional limit could be identified. Results indicated that the tensile properties depended upon specimen location and the tensile test strain rate. The data showed that as strain rate was increased, the stiffness, toughness and strength increased, while ductility decreased. Comparison of test results as a function of water content did not reveal statistically significant differences in any of the mechanical parameters. Analysis of the leaf structure suggests that the epidermal cells play a major role as a load-bearing component.     

Are norms enough? The role of collaborative norms in promoting organizational knowledge seeking

Knowledge sharing, which is critical for the strategic utilization of knowledge resources for the benefit of an organization, can only take place when both knowledge contribution and knowledge seeking exist. However, most previous research has focused on only one side of this process – knowledge contribution motivations. This is despite the fact that various barriers to knowledge seeking and reuse exist, such as the effort required to seek relevant knowledge and the cost of future obligation. In overcoming such barriers, norms related to collaboration are considered to be important. However, little is known of how these norms operate in conjunction with other antecedents to influence individuals' knowledge seeking behavior. Addressing the knowledge gap, this study explores how collaborative norms in an organization impact knowledge seeking with regard to a common knowledge management system type – the electronic knowledge repository (EKR). For this purpose, we have developed a model and tested it through a survey of EKR users in knowledge-intensive organizations. Our results indicate that collaborative norms positively impact individuals' knowledge seeking behavior through EKRs, both directly and through reducing the negative effect of future obligation on seeking. However, collaborative norms could also undermine the positive impact of perceived usefulness on knowledge seeking behavior. We identify other antecedents of knowledge seeking such as knowledge growth, resource-facilitating conditions, and self-efficacy. Implications for research and knowledge sharing practice are discussed.     

Source apportionment of organic pollutants of a highway-traffic-influenced urban area in Bayreuth (Germany) using biomarker and stable carbon isotope signatures

Traffic- and urban-influenced areas are prone to enhanced pollution with products of incomplete combustion of fossil fuels and biomass such as black carbon or polycyclic aromatic hydrocarbons (PAHs). Black carbon is composed of aromatic and graphitic structures and may act as a carrier for pollutants such as PAHs and heavy metals. However, little is known about possible contributions of traffic-derived black carbon to the black carbon inventory in soils. Similar uncertainties exist regarding the contribution of different pollutant sources to total PAH and black carbon contents. Therefore, the objective of this study was to quantify the importance of traffic pollution to black carbon and PAH inventories in soils. PAH contamination of soils adjacent to a major German highway in the urban area of Bayreuth with about 50,000 vehicles per day was in the same order of magnitude compared to highway-close soils reported in other studies. Using molecular (black carbon and PAHs) and compound-specific stable carbon isotope evidence (PAHs) it was demonstrated that this contamination originated not only from automobile exhausts, here primarily diesel, but also from tire abrasion and tailpipe soot which significantly contributed to the traffic-caused black carbon and PAH contamination. Low molecular weight PAHs were more widely transported than their heavy molecular counterparts (local distillation), whereas highway-traffic-caused black carbon contamination was distributed to at least 30 m from the highway. On the other hand, urban fire exhausts were distributed more homogeneously among the urban area.     

Mode of action and inhibition of polygalacturonase covalently bound to polysaccharide and glass carriers

Endo-polygalacturonase (EC 3.2.1.15.) from Aspergillus spec. is much changed as far as its mode of action and the interaction with vegetable inhibitors of pectinase (from green beans and cucumbers) are concerned when it is covalently bound to insoluble carriers (Sepharose, cellulose powder, macroporous glass and nonporous ballotinis). Whereas a 2% degradation of substrate by the soluble enzyme caused a 50% decrease of viscosity of citrus pectic acid, the comparable degradation of substrate was increased to a level of about 10% with the investigated polygalacturonase carrier complexes apparently independent of the properties of the carriers and the kind of binding of the enzyme. In contrast to this the higher degradation of substrate of 15 and 20% respectively which was further stated at a 50% decrease of viscosity is unambiguously connected with the carriers and is in direct correlation with the specific activity of the polygalacturonase carrier complexes. Contrary to the soluble enzyme the covalently bound enzyme produces more lower oligomerous galacturonic acids by an exo-mechanism or by multiple attack already at the beginning of the hydrolysis of pectic acid. During the final stage there is an enrichment of trigalacturonic acid besides mono- and digalacturonic acids independent of the state of solution of the enzyme. It could further be stated that the strong inhibition of the soluble endo-polygalacturonase by selected pectinase inhibitors which was described earlier is reduced by degrees with the enzyme covalently bound to the insoluble carriers.     

Direct cerebral and cardiac 17O-MRI at 3 Tesla: initial results at natural abundance

Purpose

To establish direct ¹⁷O-magnetic resonance imaging (MRI) for metabolic imaging at a clinical field strength of 3 T.

Methods

An experimental setup including a surface coil and transmit/receive switch was constructed. Natural abundance in vivo brain images of a volunteer were acquired with a radial three-dimensional (3D) sequence in the visual cortex and in the heart with electrocardiogram (ECG)-gating.

Results

In the brain, a signal-to-noise ratio of 36 was found at a nominal resolution of (5.6 mm)³, and a transverse relaxation time of T₂* = (1.9 ± 0.2) ms was obtained. In the heart ¹⁷O images were acquired with a temporal resolution of 200 ms.

Conclusion

Cerebral and cardiac ¹⁷O-MRI at natural abundance is feasible at 3 T.     

An experimental study on the bulk precipitation mechanism of physical water treatment for the mitigation of mineral fouling

The present study investigated the mechanism of physical water treatment (PWT) using particle count analyses of water. The PWT method utilized in the present study included catalytic devices and low-voltage–high-frequency device through which water continuously recirculated. Concentrated hard water at electrical conductivity of 2300–2700 μS/cm was circulated in the study at two different flow rates (i.e., 500 l/h and 800 l/h) at the room temperature. After 66 h of operation for each test, the total number of particles in water for the PWT cases increased by 165–540% as compared with those for the no-treatment cases, depending on the flow rate used. The present particle counting results provided a support for the bulk precipitation hypothesis as the mechanism of PWT, which is essentially an electro-flocculation process.     

Evaluation of the microporosity of pillared [Fe(CN)6]–MgAl–LDHs

Layered double hydroxides (LDHs) containing Mg²⁺ and Al³⁺ in the basic layers and NO⁻₃ as an interlayer anion were synthesized by the method of coprecipitation (pH 10). By changing the Mg²⁺/Al³⁺ ratio (1.5–4.5), the charge density on the (NO₃)–MgAl–LDH sheets was varied. After pillaring with Fe(CN)³⁻₆, which was based on an anion exchange process, the interlayer space became accessible. This was reflected in the large created surface areas and micropore volumes. The applied models for the calculation of the micropore size distributions (Maes–Zhu–Vansant and Horvath–Kawazoe) gave matching results, revealing narrow distributions for all the samples, with the majority of the pores smaller than 0.71 nm. A correlation was found between the Mg²⁺/Al³⁺ ratio and the resulting microporosity after pillaring. The optimal ratio was situated around 3.3, resulting in a pillared [Fe(CN)₆]–MgAl–LDH with a Langmuir surface area of 499 m²/g and a micropore volume between 0.158 ml/g (μPV_min) and 0.177 ml/g (μPV_max). As an alternative, direct coprecipitation of the pillared LDHs was evaluated. This one-step mechanism proved to be a method producing similar results. Taking all this into consideration, one can conclude that hexacyanoferrate(III) complexes form ideal anionic pillars for the creation of microporous layered double hydroxides.