Please note, due to essential maintenance online transactions will not be possible between 02:30 and 04:00 BST, on Tuesday 17th September 2019 (22:30-00:00 EDT, 17 Sep, 2019). We apologise for any inconvenience.
To send content items to your account,
please confirm that you agree to abide by our usage policies.
If this is the first time you use this feature, you will be asked to authorise Cambridge Core to connect with your account.
Find out more about sending content to .
To send content items to your Kindle, first ensure firstname.lastname@example.org
is added to your Approved Personal Document E-mail List under your Personal Document Settings
on the Manage Your Content and Devices page of your Amazon account. Then enter the ‘name’ part
of your Kindle email address below.
Find out more about sending to your Kindle.
Note you can select to send to either the @free.kindle.com or @kindle.com variations.
‘@free.kindle.com’ emails are free but can only be sent to your device when it is connected to wi-fi.
‘@kindle.com’ emails can be delivered even when you are not connected to wi-fi, but note that service fees apply.
To ensure that workers in certain industries are not exposed to harmful levels of toxic chemicals, it is necessary to provide regular monitoring of the concentrations of chemical contaminants in the workplace air. In the United Kingdom, monitoring is normally carried out on a routine basis by the factory occupier backed up by periodic visits from the Factory Inspectorate acting on behalf of the Government. The main source of guidance for occupational hygienists in assessing conditions in a factory is the list of threshold limit values (TLVs) published annually by the American Conference of Governmental Industrial Hygienists. Threshold limit values refer to airborne concentrations of substances and represent conditions under which it is believed that nearly all workers may be repeatedly exposed day after day without adverse effect.
The effect of transportation and lairage on the faecal shedding and post-slaughter contamination of carcasses with Escherichia coli O157 and O26 in young calves (4–7-day-old) was assessed in a cohort study at a regional calf-processing plant in the North Island of New Zealand, following 60 calves as cohorts from six dairy farms to slaughter. Multiple samples from each animal at pre-slaughter (recto-anal mucosal swab) and carcass at post-slaughter (sponge swab) were collected and screened using real-time PCR and culture isolation methods for the presence of E. coli O157 and O26 (Shiga toxin-producing E. coli (STEC) and non-STEC). Genotype analysis of E. coli O157 and O26 isolates provided little evidence of faecal–oral transmission of infection between calves during transportation and lairage. Increased cross-contamination of hides and carcasses with E. coli O157 and O26 between co-transported calves was confirmed at pre-hide removal and post-evisceration stages but not at pre-boning (at the end of dressing prior to chilling), indicating that good hygiene practices and application of an approved intervention effectively controlled carcass contamination. This study was the first of its kind to assess the impact of transportation and lairage on the faecal carriage and post-harvest contamination of carcasses with E. coli O157 and O26 in very young calves.
Much can be learned from terrestrial planets that appear to have had the potential to be habitable, but failed to realize that potential. Mars shows evidence of a once hospitable surface environment. The reasons for its current state, and in particular its thin atmosphere and dry surface, are of great interest for what they can tell us about habitable zone planet outcomes. A main goal of the MAVEN mission is to observe Mars’ atmosphere responses to solar and space weather influences, and in particular atmosphere escape related to space weather ‘storms’ caused by interplanetary coronal mass ejections (ICMEs). Numerical experiments with a data-validated MHD model suggest how the effects of an observed moderately strong ICME compare to what happens during a more extreme event. The results suggest the kinds of solar and space weather conditions that can have evolutionary importance at a planet like Mars.
X-ray computed tomography augmented by elemental microanalysis has been used to characterize two drill cores from the Borrowdale Volcanic Group, west Cumbria, UK. Information about the three-dimensional (3D) distribution of mineral phases was obtained non-destructively, and regions of interest were extracted for thin sectioning and elemental analysis. This revealed the presence of pyrite and other iron- and iron-titanium-bearing minerals. X-ray computed tomography is a very useful tool for 3D visualization, but the limitations of the tomography system used made it difficult to distinguish between regions with similar compositions, such as the different layers within the calcite veins. Methods by which these limitations might be overcome are briefly discussed.
High thermal conductivity heat sinks for thermal management in electronic packaging is enabling to a variety of advanced electronic applications. Heat sinks in industrial semiconductor application have thermal conductivities generally less than 180 W/mK, and frequently have large expansion mismatch with chips such as silicon and gallium arsenide. A unique technology of producing graphite fiber reinforced copper (Cf/Cu) composite has been developed that produced thermal conductivities up to 454 W/mK utilizing a K=640 W/mK fiber reinforcement (with a potential for 800 W/mK when utilizing a K = 1100 W/mK P130 fiber) and thermal expansion that can be matched to chip materials. The process consists of utilizing a hollow cathode sputtering process to deposit a bonding layer followed by copper on spread graphite fibers, which are then consolidated into composites with architectures to achieve desired thermal conductivity and thermal expansion. The copper thickness determines graphite fiber loading up to 80 %. In heat sink applications, where the electrical conductivity of the graphite fiber reinforced copper composite is a problem, processing has been developed for applying electrically insulating diamond film, which has high thermal conductivity and acts as a heat spreader.
A characterization of Plasma-Enhanced CVD Fluorinated Silicate Glass (FSG) is presented. This study investigates the behavior of FSG film in the Chemical Mechanical Polishing (CMP) environment and compares those characteristics to undoped TEOS (UTEOS), Thermal Oxide and Si-Rich oxide capped FSG films. The removal rate, refractive index (RI), surface roughness, contact angle, water content by FTIR and thermal desorption spectroscopy (TDS) were studied.
The FSG films are polished ˜ 10% faster than the undoped PECVD oxide films. Their composition was slightly changed after CMP as can be seen by the minor increase in the RI. A layer of Si-Rich oxide (SRO) was found to have a stabilizing effect on the FSG film during CMP and post CMP cleaning operations, and thus can be used in the intermetal dielectric schemes that require low dielectric constant FSG layers.
Rapid advances in high power electronic packaging require the development of new heat-sink/substrate materials. Advanced composites designed to provide thermal control as well as improved thermal conductivity have the potential to provide benefits in the removal of excess heat from electronic devices. Carbon-carbon (C-C)composites are under consideration for numerous electronic packaging applications. A new manufacturing process has been developed to produce high thermal conductivity (400 W/mK) C-C composites at greatly reduced cost (less than $50/lb). However, low CTE (0.25 × 10−6cm/cm °C) of C-C composites results in reduced fatigue life in chipon- board (COB) applications with silicon chips (CTE ≈ 2.6 × 10−6 cm/cm °C). A novel process was developed to convert the carbon matrix into the SiC matrix which retains the overall high composite thermal conductivity. This novel technology is well-suited for COB applications. Several types of coatings, such as CVD AIN, CVD Si and a polymer slurry-based low dielectric coating were applied to the C-SiC composite. Processing schemes were developed to produce crack-free coatings. Metallization of the dielectric coating was performed for the process integration with electronic devices. Thus, integrated substrates for power electronics were fabricated without the need of conventional metal/ceramic joining and associated high stresses. The properties of this new composite material for power electronics substrates are presented.
Over the past several years interest in adaptive ‘smart'materials development has gained momentum. Smart structures utilize both polymeric sensors and lead-based piezo-ceramic actuators. This paper addresses the development of an alternative smart material which consists of a novel lead-free piezo-ceramic/PVDF hybrid composite, to be used as a single component system capable of performing multiple tasks. A lead-free controlled porosity perovskite ceramic of the type A2B2O7 (Sr2 (Nb.5Ta.5)2O7 was developed utilizing hot forging. Long, oriented grains along the x-y plane, perpendicular to the forging direction were obtained in the ceramics. PVDF was subsequently infiltrated into the porous piezo-ceramic resulting in a three dimensional architecture in which the piezo-ceramic is oriented perpendicular to the PVDF. It is anticipated that manufacturability combined with the ease of functional tailorability of such a class of lead-free hybrid materials can be useful in a variety of smart structures applications.
ZnO colloidal nanocrystals have been synthesized using two different approaches and characterized by HRTEM, EDS, and photoluminescence spectroscopy. ZnO nanocrystals synthesized from zinc alkoxy alkyl precursors in the MeIm/H2O coordinating solvent showed only visible surface-defect related emission in their PL spectra. No band-to-band UV emission was observed after ZnS coating of those ZnO nanocrystals. In contrast, a strong band-to-band UV emission dominated PL spectra of ZnO nanocrystals synthesized through wet-chemical acid-catalyzed esterification of zinc acetate.
The effects of 137Cs gamma irradiation on photoluminescence properties, such as spectra, light output, and lifetime, of several types of colloidal nanocrystals have been investigated. Irradiation-induced damage testing was performed on CdSe/ZnS, LaF3:Eu, LaF3:Ce, ZnO, and PbI2 nanocrystals synthesized on a Schlenk line using appropriate solvents and precursors. Optical degradation of the nanocrystals was evaluated based on the measured dependence of their photoluminescence intensity on the irradiation dose. Radiation hardness varies significantly between various nanocrystalline material systems.
This study estimated total body water (TBW) in four groups (twelve per group; sedentary and highly trained men and women) at the time of 2H dosing (T0) and after a 3·5 h equilibration period (Teq). Standard TBW calculations were employed at T0 (no correction for disproportionate urinary tracer loss) and Teq (correction for urinary tracer loss only), plus those calculations that corrected for a disproportionate urinary tracer loss and insensible tracer loss respectively. The measurement of body density enabled the four TBW estimates to be compared for the determination of three-compartment % body fat (BF). The very small difference between the standard and corrected T0 TBW data was not significant (P=0·914) and no Group×TBW interaction was identified (P=0·125). These results reflect the closeness of the 2H concentration in the urine produced during the equilibration period and the Teq saliva samples. The associated mean % BF values were essentially identical. Although correcting for insensible 2H losses in addition to urinary losses at Teq produced a statistically significant (P<0·001) lower mean TBW (about 200 g) than the standard calculation, this translated to a small difference in % BF (0·3). The larger difference (about 500 g, P<0·001) between the two (T0, Teq) corrected TBW calculations was also associated with a small body composition difference (0·1 % BF), which was less than the propagated error (0·3 % BF) for the three-compartment body composition model. Corrections to the standard calculations of TBW at T0 and Teq for a protocol employing a brief equilibration period (3·5 h) were therefore of marginal use for improving the accuracy of % BF estimates. The TBW difference over time (T0v. Teq) also had little impact on % BF values.
This chapter considers (a) the generation of highly branched (colonial)mutants during prolonged fermentation of the Quorn® myco-protein fungus, Fusarium graminearum A3/5, (b) the influence of hyphal branch frequency on the production of extracellular enzymes by Aspergillus oryzae, and (c) the stability of Aspergillus niger gla A transformants in prolonged continuous how cultures. We believe that the results obtained with these three species can be extended to most, if not all, filamentous fungi.
Highly branched mutants do not have a selective advantage because of their morphology
When filamentous fungi or streptomycetes are grown in prolonged, continuous culture, it is common for the relatively sparsely branched parental strain to be supplanted by a relatively highly branched mutant (Fig. 5.1). Such mutants are called colonial because in Petri dish culture they form dense colonies that expand in radius more slowly than parentalcolonies. Selection of colonial mutants has been observed in continuouscultures of Byssochlamys nivea, Paecilomyces variotii, Paecilomyces puntanii, Gliocladium virens, Trichoderma viride (Forss et al., 1974), Penicillium chrysogerrum (Righelato, 1976), F. graminearum (Solomons & Scammell, 1976) and Acremonium chrysogemrm (A. Trilli, personal communication).
Sixteen highly branched (colonial) mutants of
Fusarium graminearum A3/5 were isolated at the
end of 11 Quorn® myco-protein
production fermentations. These ranged from the highly
branched C134-3 to the sparsely branched C145, which was similar to
A3/5 in liquid culture. Although allelic complementation
was observed to occur between some of the mutants,
revealed that all the highly branched mutants belonged to
a single complementation group. Mixed cultures of A3/5
and six of the
colonial mutants were grown in glucose-, ammonium-,
magnesium- and sulphate-limited chemostat culture. One
mutant (C153) had a
selective advantage over A3/5 in all nutrient
limitations tested; four mutants (C134-1, C134-3, C137-1,
and C135) had a selective
advantage over A3/5 in all except one nutrient
limitation; and one mutant (C139) had a selective advantage
over A3/5 in
magnesium-limited chemostat culture only. Four mutants
(C134-3, C139-1, C153 and C135) had a selective advantage
when the dilution rate was increased above the critical
dilution rate (0·22 h−1)
and nutrients were present in excess. These results
suggest that the growth conditions in the Quorn®
production plant (which is operated as a glucose-stat)
favour mutations that
confer general growth rate advantages, but these mutations
may result in growth disadvantages when nutrient limitations are
imposed. As all of the mutations appear to occur in one
gene or gene cluster, the differing patterns of selective
advantage/disadvantage for the six mutants studied
suggests that regulatory genes may also be involved or
that different sites of
mutation can lead to a variety of pleiotropic effects.