Experimental investigation of the thermal boundary layer in a confined liquid

Experimental investigation of thermal boundary layer in confined liqui

Metrical relationships in a standard triangle in an isotropic plane

Each allowable triangle of an isotropic plane can be set in a standard position, in which it is possible to prove geometric properties analytically in a simplified and easier way by means of the algebraic theory developed in this paper

Autoxidation of lipids in parchment

Historic parchment is a macromolecular material, which is complex due to its natural origin, inhomogeneity of the skin structure, unknown environmental history and potential localised degradation. Most research into its stability has so far focussed on thermal and structural methods of analyses. Using gas chromatographic analysis of the atmosphere surrounding parchment during oxidation, we provide the experimental evidence on the production of volatile aldehydes, which can be the products of lipid autoxidation. Oxidation of parchment with different aldehyde emissions was additionally followed in situ using chemiluminometry and the same techniques were used to evaluate the oxidation of differently delipidised parchment. It was shown that the production of peroxides and the emission of aldehydes from the material decrease with lower lipid content. Building on this evidence, we can conclude that the presence of lipids (either initially present in the skin or resulting from conservation intervention) leads to oxidative degradation of collagen and that the non-destructive analysis of the emission of volatiles could be used as a quick tool for evaluation of parchment stability

Determination of mechanical properties of historical paper based on NIR spectroscopy and chemometrics - a new instrument

Due to sampling restrictions in the analysis of cultural heritage materials, non-destructive approaches are intensively sought for. While NIR spectrometry has rarely been used for this purpose due to the complexity of the spectra, chemometric methods can be used to extract the necessary information. For the purpose of determination of mechanical properties of historical paper, partial least squares approach was used and it is shown that tensile strength, and tensile strength after folding, can be estimated based on NIR spectra. As the mechanical properties of paper-based objects define their accessibility, a new dispersive portable instrument was built, which will enable us to rapidly survey the condition of library and archival collections

Emission of reactive oxygen species during degradation of iron gall ink

Iron gall inks are characterised by high contents of acids and transition metals, promoting degradation of cellulose due to hydrolysis and oxidation, respectively. Their chemical interaction with the environment is not well understood, especially in view of emissions of degradation products which could lead to spread of degradation processes. In order to study the emissions, we employed gas chromatography/mass spectrometry following headspace micro-extraction, and liquid chromatography following hydroxyl radical scavenging with appropriate probes. We also studied chemiluminescence of cellulose affected by ink degradation. We show that while the emissions of organic volatile degradation compounds by inks are less intense than those of surrounding paper, ink does promote the degradation of cellulose across big distances (from object to object). We were able to link this to emission of reactive oxygen species, probably hydrogen peroxide. Its emission from ink is considerably more intensive than from paper

Optical Coherence Tomography for Examination of Parchment Degradation

A novel application of Optical Coherence Tomography utilizing infrared light of 830 nm central wavelength for non invasive examination of the structure of parchment, some covered with iron gall ink, is presented. It is shown that both the parchment and the ink applied are sufficiently transparent to light of this wavelength. In the study, Spectral OCT (SOCT) as well as Polarisation Sensitive OCT (PS-OCT) techniques were used to obtain cross-sectional images of samples of parchment based on scattering properties. The second technique was additionally employed to recover the birefringence properties and the optical axis orientations of the sample. It was shown that freshly produced parchment exhibits a degree of birefringence. However, this property declines with ageing, and samples of old parchment completely depolarise the incident light

Mission Profile Based Optimization of a Synchronous-Buck DC-DC Converter for a Wearable Power System

A Wearable Power System (WPS) is a portable fuel-to-electrical energy converter that is carried on the body and is able to supply an average of 20 W for 4 days and has a total weight of less than 4 kg. Due to limited total weight of the system, each system part must have the highest efficiency to weight ratio. This paper presents the optimization of a synchronous buck DC-DC converter that is used to regulate the variable power source to a constant 14 VDC for the load. Higher switching frequency leads to smaller components and low weight, but at the same time, to higher losses that are compensated through additional fuel weight. If low switching frequency is applied, the weight of the converter will increase due to a larger inductor, but the power losses will be lower. Therefore, an optimal switching frequency should exist that results in the total weight of the DC-DC converter and additional fuel being a minimum. The paper first explains the proposed solution for WPS, the load pattern that is used to test the system and then the algorithm that decides on the number of converters to be used and how to find the optimal switching frequency. Additionally, two prototypes have been constructed. First prototype has nominal power of 20 W and is used in the analysis regarding the optimal number of converters. The second one has rated power of 200 W and it is built to support the conclusions based on the optimization process

Volatile aldehydes in libraries and archives

Volatile aldehydes are produced during degradation of paper-based materials. This may result in their accumulation in archival and library repositories. However, no systematic study has been performed so far. In the frame of this study, passive sampling was carried out at ten locations in four libraries and archives. Despite the very variable sampling locations, no major differences were found, although air-filtered repositories were found to have lower concentrations while a non-ventilated newspaper repository exhibited the highest concentrations of volatile aldehydes (formaldehyde, acetaldehyde, furfural and hexanal). Five employees in one institution were also provided with personal passive samplers to investigate employees’ exposure to volatile aldehydes. All values were lower than the presently valid exposure limits. The concentration of volatile aldehydes, acetic acid, and volatile organic compounds (VOCs) in general was also compared with that of outdoor-generated pollutants. It was evident that inside the repository and particularly inside archival boxes, the concentration of VOCs and acetic acid was much higher than the concentration of outdoor-generated pollutants, which are otherwise more routinely studied in connection with heritage materials. This indicates that further work on the pro-degradative effect of VOCs on heritage materials is necessary and that monitoring of VOCs in heritage institutions should become more widespread

A Middle Jurassic Radiolarite-Clastic Succession from the Medvednica Mt. (NW Croatia

On the NW part of Medvednica Mt. radiolarites with carbonate olistoliths, shales and siltites, matrix-supported conglomerates and basic volcanic rocks were investigated. This facies association is informally named the Poljanica unit. Major element geochemical data indicate deposition of radiolarites in the vicinity of the middle oceanic ridge, while sedimentological data indicate deposition in an area closer to the continent. Shales and siltites, as well as matrix-supported conglomerates, were deposited in short periods characterised by increased input of terrigenous material. Matrix-supported polymict conglomerates are composed of silicified shales, lithic graywackes, cherts and metabasalts, and were deposited by debris flow mechanisms as a consequence of synsedimentary tectonic activity. Carbonate olistoliths are composed of biomicrosparite, and jointly with deformed radiolarian cherts compose an olistostrome. Basic volcanic rocks represent high-Ti tholeiitic basalts formed in the MORB realm. Micropalaeontological investigation of radiolarite samples proved the Middle Jurassic (latest Bajocian - early Bathonian to late Bathonian - early Callovian) age of the Poljanica unit. Additionally, a new radiolarian species Theocapsomma medvednicensis n.sp. has been described. Conodont analyses from carbonate olistoliths in radiolarites proved their Triassic age. The investigated radiolarite-clastic succession is the result of subduction processes. Further continuation of this process caused incorporation of these deposits into the accretionary prism, where they were brought in direct contact with Triassic volcanic rocks and radiolarites (in the form of a tectonic mélange). Based on the lithological similarities with the Middle Jurassic turbidite-olistostrome successions in the Western Carpathians and Northern Calcareous Alps, the study area is considered to be part of the Meliata-Hallstatt Ocean

Effects of Oil and Gas Development on Mule Deer Populations in Western North Dakota and Eastern Montana

Oil and gas production are becoming a significant part of the economy and landscape of western North Dakota and eastern Montana.  Much of the areas being developed overlap with mule deer ranges.  Our ongoing research aims to identify and quantify the direct and indirect effects of oil and gas energy development on mule deer abundance, survival, recruitment, movements and resource selection.  Since February, 2013, we have deployed 240 GPS collars in three main areas of breaks habitat: 1) in North Dakota along the Little Missouri River; 2) the east side of the Yellowstone River; and 3) just south of Culbertson, MT. These collars are being used to collect spatial data about mule deer distributions and monitor survival across areas of low, medium, high energy development.  We will also use digitized aerial survey data to estimate abundance and recruitment across various levels of development. To date we have collared 99 adult females and 110 fawns, gathering more than 300,000 deer locations, conducted 39 lab necropsies on full and partial carcasses, and conducted biannual aerial surveys in North Dakota (2 years) and Montana (1 year). Our research will address potential impacts to mule deer populations, but will also provide mitigation strategies to help minimize disturbances from further development