Analysis of polyethylene by using cyclopentadienyl cobalt chemical ionization combined with laser-induced acoustic desorption/fourier transform ion cyclotron resonance mass spectrometry

A new mass spectrometric method has been developed for the analysis of low molecular weight polyethylene (PE). Laser-induced acoustic desorption (LIAD), combined with chemical ionization by the cyclopentadienyl cobalt radical cation (CpCo.+) in a Fourier transform ion cyclotron resonance mass spectrometer, produces predominantly a quasimolecular ion, (R + CpCo - 2H2).+, for each PE oligomer (R). An examination of artificial alkane mixtures revealed no mass bias for alkanes of differing molecular weights. However, the success of the LIAD/CpCo.+ CI technique depends greatly upon the LIAD sample preparation method used. Several sample preparation methods were evaluated, and pneumatically assisted spin coating was concluded to provide the best mass spectra as a result of its ability to provide uniform PE coverage on the LIAD foils. The molecular weight distributions measured for several low molecular weight PE samples (200-655) were found to be in good agreement with manufacturers' values as determined by gel permeation chromatography.     

Effect of mask-roughness on printed contact-size variation in extreme-ultraviolet lithography

Relying on reflective mask technology, extreme-ultraviolet (EUV) lithography is particularly vulnerable to mask substrate roughness. Previous research has shown mask roughness to play a significant role in printed line-edge roughness (LER). Here the analysis of mask-roughness effects is extended to printed contact-size variations. Unlike LER, illumination partial coherence is found to have little affect on the results for contacts that are near the diffraction limit. Analysis shows that, given the current state-of-the-art EUV mask, mask roughness has a significant effect on the process window for small contacts. The analysis also shows that a significant portion of the contact-size variation observed in recent 0.1-numerical-aperture EUV exposures can be attributed to the mask-roughness effect studied here.     

Overexpressed yeast mitochondrial putative RNA helicase Mss116 partially restores proper mtRNA metabolism in strains lacking the Suv3 mtRNA helicase

RNA helicase, encoded by the Saccharomyces cerevisiae nuclear gene SUV3, is a subunit of the mitochondrial (mt) degradosome: an enzyme complex that takes part in turnover of mtRNAs. Deletion of the SUV3 gene leads to a variety of disturbances in mtRNA metabolism and results in respiratory incompetence of yeast cells. Here we show that the nuclear gene MSS116, which codes for a mitochondrial putative RNA helicase necessary for splicing of several mt introns, can suppress the lack of the SUV3 gene. Overexpression of the Mss116 putative helicase from a multicopy plasmid present in the SUV3-deleted strains partially restores respiratory competence, brings the steady-state levels of COB and ATP6/8 mRNA back almost to normal and lowers the accumulation of 21S rRNA and ATP6/8 RNA precursors to the wild-type levels. To the best of our knowledge, this is the first reported case of a substitution of one RNA helicase by another, belonging to a different class of RNA helicases.     

Phenotypic modulation of fibroblastic cells in the mucous layer of the human uterine cervix at term

The uterine cervix is a dynamic structure with a high capacity to adapt to different, even opposing, roles during the sequence of physiological events of gestation (for example, acting as a barrier to retain the fetus during pregnancy and dilating to allow delivery at term). Histoarchitectural changes of the uterine cervix allow its successful adaptation. The aim of this study was to investigate whether fibroblastic cell plasticity, described in the lamina propria of the rat uterine cervix at term, could be observed in women too. Biopsy specimens of non-pregnant and intrapartum human cervices were studied under the transmission electron microscope, and cytoskeletal differentiation markers were identified by immunohistochemistry under the light microscope. Desmin-positive cells were present in the mucous layer of the cervix during labour. These cells displayed cytoplasmic processes (typical of myofibroblasts) that also stained positively for vimentin. The main ultrastructural features for defining the myofibroblast under the electron microscope were also observed in these cells. However, cervices of non-pregnant women contained resident fibroblasts at the same location. Examination of the differentiation repertoire of fibroblastic cells in the mucous layer of the uterine cervix resulted in the characterization of myofibroblasts at term. The implications of the plasticity of fibroblastic-myofibroblastic cells in the physiological changes displayed in the uterine cervix during pregnancy, labour and postpartum involution require further investigation.     

Enhanced optical limiting and nonlinear absorption properties of azoarene-appended phosphorus (V) tetratolylporphyrins

Optical limiting performance, third-order nonlinearity chi(3), and nonlinear absorption properties have been investigated in a new class of azoarene phosphorus (V) porphyrins with charge transfer (CT) states. The introduction of axial azoarene groups into the phosphorus porphyrin structure is found to reduce the limiting threshold by a factor of 2 and lead to a rise in the second hyperpolarizability by 1 order of magnitude in the picosecond time regime and by 2 orders of magnitude in the nanosecond regime. The experimental data show reverse saturation of absorption in the nanosecond time regime and a saturation of the nonlinear absorption above a fluence of 0.5 J/cm2 in the picosecond regime. The presence of the CT state reduces saturation of excited-state absorption (ESA) in the S1 --> Sn transition through the S1 --> CT transition. Faster CT --> T1 transition increases the ESA from T1 --> Tn states in the nanosecond regime. A self-consistent theoretical analysis based on rate equations is used to estimate the high-lying excited-state lifetimes and absorption cross sections from the experimental results.     

Rheological behaviour and mechanical characterization of injectable poly(propylene fumarate)/single-walled carbon nanotube composites for bone tissue engineering

This work investigated the effects of the use of a surfactant or the functionalization of single-walled carbon nanotubes (SWNTs) on their dispersion in uncrosslinked poly(propylene fumarate) (PPF) and the mechanical reinforcement of crosslinked composites as a function of the SWNT concentration. Rheological measurements showed good dispersion of SWNTs in uncrosslinked PPF at low concentrations of 0.05?wt% and SWNT aggregation for higher concentrations for all formulations examined. Mechanical testing demonstrated significant reinforcement in the compressive and flexural mechanical properties of crosslinked nanocomposites which peaked for low SWNT concentrations of the order of 0.05?wt%. For example, a 74% increase was recorded for the compressive modulus and a 69% increase for the flexural modulus of nanocomposites with functionalized SWNTs at a 0.05?wt% loading. Nevertheless, this reinforcement was not related to the use of a surfactant or the functionalization of the SWNTs tested. Scanning electron microscopy examinations of fractured nanocomposite surfaces revealed the formation of SWNT aggregates at higher concentrations corroborating the rheological and mechanical data. These results suggest that the dispersion of individual SWNTs in a uncrosslinked formulation is pivotal to the development of injectable nanocomposites for bone tissue engineering applications.     

Information technology and road transport industry: how does IT affect the lorry driver?

A quasi-experimental design was used to study the effect of on board computer-systems (OBC-systems) on the Dutch lorry drivers' psychosocial work environment (i.e., control and demands) and coinciding mental health (i.e., need for recovery after work) and job attitudes (i.e., organisational commitment). The intervention group (n = 26) started working with an OBC-system between 1998 and 2000 and was compared with two matched reference groups (n = 26 in both groups). All participants were from a cohort of 650 drivers who participated in a prospective study on occupational stress and health. All outcome variables were quantified by standardised and validated questionnaires. Results showed that the application of OBC-systems negatively affected the drivers' job control and organisational commitment. However, OBC-systems did not influence the drivers' psychological job demands and need for recovery after work. Accordingly, it is concluded that the application of OBC-systems negatively affects the lorry driver's psychosocial work environment and job attitudes.     

Relevance of mask-roughness-induced printed line-edge roughness in recent and future extreme-ultraviolet lithography tests

The control of line-edge roughness (LER) of features printed in photoresist poses significant challenges to next-generation lithography techniques such as extreme-ultraviolet (EUV) lithography. Achieving adequately low LER levels requires accurate resist characterization as well as the ability to separate resist effects from other potential contributors to LER. One potentially significant contributor to LER arises from roughness on the mask coupling to speckle in the aerial image and consequently to LER in the printed image. Here I numerically study mask surface roughness and phase roughness to resist LER coupling both as a function of illumination coherence and defocus. Moreover, the potential consequences of this mask effect for recent EUV lithography experiments is studied through direct comparison with experimental through-focus printing data collected at a variety of coherence settings. Finally, the effect that mask roughness will play in upcoming 0.3-numerical-aperture resist testing is considered.     

Role of caustics in the formation of networks of amplitude zeros for partially developed speckle fields

The topology of a partially developed speckle field was studied by use of interference techniques through computer simulation. Amplitude and phase structures in the vicinity of caustics for a coherent radiation field scattered at a surface with large inhomogeneities were investigated. It was confirmed that the caustics are indispensible components of the procedure for the formation of networks of amplitude zeros for a coherent field scattered by a rough surface with large inhomogeneities. It is shown that the formation of interference forklets in the field gives evidence of changes in the field's topology, as these forklets are a diagnostic sign of transition from a caustic to a three-dimensional pattern of a diffraction catastrophe.     

The effect of preventive trimming on weight bearing and force balance on the claws of dairy cattle

Claw disorders and lameness in dairy cattle are an increasing problem of the modern dairy industry. To prevent claw disorders from evolving from the subclinical to the clinical stage, trimming is the management practice most routinely applied. The goal of preventive trimming (Toussaint-Raven method) is to promote natural loading by increasing the weight-bearing contact area of the claws and improving the balance between the medial and lateral claw. The biomechanical effect of preventive claw trimming was investigated with the aid of pressure distribution and ground reaction force recordings of the standing cow sampled simultaneously at 250 Hz. It appeared that preventive trimming of the hind limbs (n = 10) brought the claws slightly more in balance. Before trimming, 80% of the total force is taken up by the lateral claw and 20% by the medial claw. After trimming, this becomes 70 to 30%, respectively. Thereby, a significant increase in the weight-bearing contact area from 27.5 to 40.0 cm2 was achieved, resulting in a significant decrease in average pressure. However, the claws remained subjected to unaltered, high maximum pressures after trimming. The suggestion was made that the main focus of claw trimming should not be force balance; instead, a reduction of local maximum pressures at the contact area should be targeted in such a way that the strongest parts of the claw capsule (i.e., the wall) will be subjected to the highest pressures.