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Background: The aim of this study was to investigate intraoperative methods to generate patient-specific PMMA bone implants during a craniotomy. The proposed methods combine a cost-efficient, and non-invasive structured light scanner (SLS) as an imaging modality and a prototype printer for rapid generation of implant molds. Methods: This simulation study was performed using retrospective data from three craniotomy patients. The extracted bone flap and the cranial defect were scanned using a SLS, which generates a 3D surface model of an object by projecting a series of light-patterns on it. Prototype printed implant models were generated using two different techniques. The molds were then used to shape PMMA bone implants. These implants were evaluated regarding their accuracy to reconstruct the natural skull anatomy and compared to freehand formed implants. Results: The patient-specific bone implants reconstructed the preoperative anatomy with an average RMS error of 1.37mm (StDev 0.27), compared to an error of 1.5mm (StDev 0.43) for the freehand shaped implants. On average the intraoperative scanning time was 4.7min. The average time to generate and print the implant molds was 204 min. Conclusions: Results of this study have shown great promise for the proposed method to be used for patient-specific bone flap reconstruction during craniotomies.
We present a theoretical framework for describing electromagnetic kinetic turbulence in a multi-species, magnetized, pressure-anisotropic plasma. The turbulent fluctuations are assumed to be small compared to the mean field, to be spatially anisotropic with respect to it and to have frequencies small compared to the ion cyclotron frequency. At scales above the ion-Larmor radius, the theory reduces to the pressure-anisotropic generalization of kinetic reduced magnetohydrodynamics (KRMHD) formulated by Kunz et al. (J. Plasma Phys., vol. 81, 2015, 325810501). At scales at and below the ion-Larmor radius, three main objectives are achieved. First, we analyse the linear response of the pressure-anisotropic gyrokinetic system, and show it to be a generalization of previously explored limits. The effects of pressure anisotropy on the stability and collisionless damping of Alfvénic and compressive fluctuations are highlighted, with attention paid to the spectral location and width of the frequency jump that occurs as Alfvén waves transition into kinetic Alfvén waves. Secondly, we derive and discuss a very general gyrokinetic free-energy conservation law, which captures both the KRMHD free-energy conservation at long wavelengths and dual cascades of kinetic Alfvén waves and ion entropy at sub-ion-Larmor scales. We show that non-Maxwellian features in the distribution function change the amount of phase mixing and the efficiency of magnetic stresses, and thus influence the partitioning of free energy amongst the cascade channels. Thirdly, a simple model is used to show that pressure anisotropy, even within the bounds imposed on it by firehose and mirror instabilities, can cause order-of-magnitude variations in the ion-to-electron heating ratio due to the dissipation of Alfvénic turbulence. Our theory provides a foundation for determining how pressure anisotropy affects turbulent fluctuation spectra, the differential heating of particle species and the ratio of parallel and perpendicular phase mixing in space and astrophysical plasmas.
A theoretical framework for low-frequency electromagnetic (drift-)kinetic turbulence in a collisionless, multi-species plasma is presented. The result generalises reduced magnetohydrodynamics (RMHD) and kinetic RMHD (Schekochihin et al., Astrophys. J. Suppl. Ser., vol. 182, 2009, pp. 310–377) to the case where the mean distribution function of the plasma is pressure-anisotropic and different ion species are allowed to drift with respect to each other – a situation routinely encountered in the solar wind and presumably ubiquitous in hot dilute astrophysical plasmas such as the intracluster medium. Two main objectives are achieved. First, in a non-Maxwellian plasma, the relationships between fluctuating fields (e.g. the Alfvén ratio) are order-unity modified compared to the more commonly considered Maxwellian case, and so a quantitative theory is developed to support quantitative measurements now possible in the solar wind. Beyond these order-unity corrections, the main physical feature of low-frequency plasma turbulence survives the generalisation to non-Maxwellian distributions: Alfvénic and compressive fluctuations are energetically decoupled, with the latter passively advected by the former; the Alfvénic cascade is fluid, satisfying RMHD equations (with the Alfvén speed modified by pressure anisotropy and species drifts), whereas the compressive cascade is kinetic and subject to collisionless damping (and for a bi-Maxwellian plasma splits into three independent collisionless cascades). Secondly, the organising principle of this turbulence is elucidated in the form of a conservation law for the appropriately generalised kinetic free energy. It is shown that non-Maxwellian features in the distribution function reduce the rate of phase mixing and the efficacy of magnetic stresses, and that these changes influence the partitioning of free energy amongst the various cascade channels. As the firehose or mirror instability thresholds are approached, the dynamics of the plasma are modified so as to reduce the energetic cost of bending magnetic-field lines or of compressing/rarefying them. Finally, it is shown that this theory can be derived as a long-wavelength limit of non-Maxwellian slab gyrokinetics.
Post-conflict mental health studies in low-income countries have lacked
pre-conflict data to evaluate changes in psychiatric morbidity resulting
from political violence.
This prospective study compares mental health before and after exposure
to direct political violence during the People's War in Nepal.
An adult cohort completed the Beck Depression Inventory and Beck Anxiety
Inventory in 2000 prior to conflict violence in their community and in
2007 after the war.
Of the original 316 participants, 298 (94%) participated in the
post-conflict assessment. Depression increased from 30.9 to 40.6%.
Anxiety increased from 26.2 to 47.7%. Post-conflict post-traumatic stress
disorder (PTSD) was 14.1%. Controlling for ageing, the depression
increase was not significant. The anxiety increase showed a dose–response
association with conflict exposure when controlling for ageing and daily
stressors. No demographic group displayed unique vulnerability or
resilience to the effects of conflict exposure.
Conflict exposure should be considered in the context of other types of
psychiatric risk factors. Conflict exposure predicted increases in
anxiety whereas socioeconomic factors and non-conflict stressful life
events were the major predictors of depression. Research and
interventions in postconflict settings therefore should consider
differential trajectories for depression v. anxiety and
the importance of addressing chronic social problems ranging from poverty
to gender and ethnic/caste discrimination.
Maintenance of postural balance requires an active sensorimotor control system. Current data are limited and sometimes conflicting regarding the influence of the proprioceptive, visual, and vestibular afferent systems on posture control in children. This study investigated the development of sensory organization according to each sensory component in relation to age and sex. A total of 140 children (70 males, 70 females; mean age 10y [SD 4y]; age range 3y 5mo–16y 2mo) and 20 adults (10 males, 10 females; mean age 30y 6mo [SD 8y 4mo]; age range 17y 2mo–49y 1mo) were examined using the Sensory Organization Test. Participants were tested in three visual conditions (eyes open, blindfolded, and sway-referenced visual enclosure) while standing on either a fixed or a sway-referenced force platform. Mean equilibrium scores for the six balance conditions showed rapid increases and maturation ceiling levels for age-related development of the sensorimotor control system. Proprioceptive function seemed to mature at 3 to 4 years of age. Visual and vestibular afferent systems reached adult level at 15 to 16 years of age, revealing differences between young males and females. Characterizing balance impairments can contribute to the diagnostic evaluation of neuromotor disorders.
Growth and development of adult schistosomes requires permanent communication processes of the parasites with their specific host environment and, additionally, between the two genders. Accumulating evidence suggests that, at the molecular level, the mandatory interactions are mediated by signal transduction processes. During recent years, a considerable interest has emerged in the identification of signalling molecules from this parasite and to elucidate their roles during development. In this organism, a number of different molecules have been identified which belong to diverse classes of evolutionary conserved signal transduction cascades. However, up to now no representative of the conserved family of cellular tyrosine kinases has been identified. In this study we present a suitable approach to identify this class of molecules and demonstrate the successful cloning and molecular characterization of one of the isolated genes, the tyrosine kinase 5 (TK5). An unexpected finding was that in the Liberian strain of Schistosoma mansoni the TK5 gene exhibits an allelic polymorphism.
Patterns of dispersion and site fidelity were investigated in a tent-roosting population of the short-nosed fruit bat, Cynopterus sphinx (Megachiroptera), in southern India. A local population of C. sphinx occupied diurnal roosts in a variable subset of 45 stem tents constructed within the dense foliage of mast trees (Polyalthia longifolia). Individually marked tent-roosting bats were visually censused over the course of a 38-d interval spanning the postpartum oestrus period. On any given day, 33.3–85.7% (mean = 60.8%, SD = 14.2) of adult males roosted singly, with the remainder holding harems of 1–10 breeding females (mean = 3.01, SD = 0.79). Average harem sex ratio was 2.8-fold higher than the adult sex ratio of the total tent-roosting population within the study area, indicating the potential for a high variance in male mating success within a single breeding season. Bats of both sexes typically occupied one primary tent, interspersed with shorter periods of residency in alternate tents. Males exhibited a significantly higher degree of roost fidelity than females. Some females roosted sequentially with different males and with different combinations of females, whereas others remained continuously associated with a single male and/or particular female roostmates over the duration of the census period. There were no statistically significant relationships between physical characteristics of tents and rates of occupancy by males or females. Intermittent transfers by females between groups suggest that the defence of diurnal roosts by males represents a more profitable mating strategy than the direct defence of compositionally labile female groups.
We describe the size and developmental state at birth, examine factors which influence intra- and inter-year variation in post-natal growth, and derive age-predictive equations and logistic growth parameters for the eastern pipistrelle bat, Pipistrellus subflavus. Ambient and roost temperature and insect abundance were lowest, and precipitation highest, before and during the post-natal growth period in 1982, as compared to 1981. We found no sex differences in the size of pups at birth or in post-natal growth rates in a given year; however, body mass and length of forearm of neonates differed significantly between years, being smaller in 1982 than in 1981. During the first two weeks of post-natal growth in both years, the body mass and length of forearm of pups increased linearly at mean rates of 0.15 g.day−1 and 1.12 mm.day−1, respectively. Post-natal growth rates for length of forearm and body mass were the same during the early linear phase of growth, but the intercept for body mass was less and growth trajectories were more variable in 1982. Length of forearm was the least variable and thus most reliable character for estimating age of P. subflavus pups during the first 14 days of post-natal growth. When length of forearm was used in combination with mean changes in the length of the fourth metacarpal-phalangeal epiphyseal gap, we derived reliable age-estimation equations ranging from 1 to 45 days. Litter size averaged 1.96 and 1.93 at birth, but this was reduced to one by the time pups became volant. At birth, litter mass represented 44, and 54% of the post-partum mass of females in 1981 and 1982, respectively. This maternal effort during pregnancy is among the highest reported for bats. At weaning, the body mass of pups approached 80% of adult post-partum body mass, and the length of forearm exceeded 90% of adult female size. Our results suggest that size at birth and post-natal growth are influenced by ambient and roost temperature, rainfall, and the quantity of insects available to pregnant and lactating females. Thus, energetic constraints on both mothers and pups can lead to inter-year and inter-individual differences in maternal effort and post-natal growth of pups.
Information on the feeding habits of the the lesser dog-faced friut bat, Cynopterus brachyotis, was obtained by the collection of food remains directly beneath daytime and feeding roosts. The bats were found to feed on the fruits of 54 plant species, the leaves of 14 species and the flower parts of four species. The seasonal phenological differences among congeneric plant species led to steady production of fruit throughout the year and the data suggets that Ficus spp. are a key component in the diet. Judging from its wide selection of fruits, C. brachyotis, is considered to be an important seed disperser. Folivory in C. brachyotis appears to be more common than previously thought. Of the leaves consumed by the bats, seven species belonged to the family Leguminosae, followed by Myrtaccae, Moraccae, Rhizophoacae and Euphorbiaccae. Friuts in general, provide an energy rich diet for phytophagous bats but most are low in protein. In contrast, leaves consumed by bats have a relatively high protein content. We suggest that folivory (by leaf fractionation) should be energetically more advantageous than the ingestion of large amounts of low protein friut or the active pursuit of mobile insects.
A female-specifically expressed cDNA clone was obtained
by screening of a subtractive cDNA library enriched for RNA
from Schistosoma mansoni females. The deduced
protein shows significant homology to a class of enzymes
functioning as amidases. Northern blots revealed a transcript
of 4·0 kb which is absent in larval stages, but is
expressed in adult female
worms. By in situ hybridization, the expression site
of the gene was exclusively localized in the gastrodermis of female
schistosomes. This is the first report of a female-specifically
transcribed sequence of S. mansoni that is not
expressed in the reproductive organs.
The tegument of the human parasite Schistosoma mansoni is critical for parasite survival within the mammalian host. The role of protein kinase C (PKC), a major effector molecule in the phosphoinositide pathway, in maintaining the structural organization of this syncytial layer was examined in adult worms. Phorbol 12-myristate, 13-acetate (PMA) and phorbol 12,13-dibutyrate (PDB), phorbol esters that activate PKC, induced formation of surface vesicles as determined by light and scanning electron microscopy. Similar results were seen with sn-2-dioctanoyl-glycerol, a synthetic analogue of diacylglycerol. No effect was seen in parasites incubated with 4-a-phorbol ester or a isomers of PMA or PDB, compounds that do not activate PKC. Vesicle formation was reversible in parasites treated with sn-2-dioctanoyl-glycerol but not with phorbol esters. The tegument of male worms was more sensitive to the effect of phorbol esters than females. Transmission electron microscopy revealed vacuolization of the tegument. These data suggest that signal transduction pathways may have a critical role in the maintenance of the structural integrity of the tegument of parasitic helminths.
For a complete description of a material's microstructure the morphology as well as the distributions of chemical elements and of crystal lattice orientations must be known. While morphology is a standard issue of electron microscopy, and element distributions can be mapped readily using an EDX appliance, crystal lattice orientations in the bulk surface are accessible in routine work only recently [1, 2]. Backscatter Kikuchi patterns (BKP), also termed electron backscattering patterns (EBSP), are widely used for the determination of individual grain orientations in the surface of bulk polycrystals.
Neutron diffraction texture goniometry indicates that naturally deformed polycrystalline pyrite ores from Mt. Lyell (Tasmania) and Degtiarka (Ural Mountains) have weak lattice preferred orientations. During experimental deformation involving dislocation flow at elevated temperatures and pressures, these initial fabrics have been modified to produce new lattice preferred orientations.
Polycrystalline pyrite form Mt. Lyell (B-1) has an initial <111> - fibre texture perpendicular to a grain-size layering. After 24% shortening perpendicular to the <111> - fibre axis at 700°C a new, but weak <100> texture has developed parallel to the shortening axis. The Degtiarka pyrite (PN-6) initially has two weak fibre components. The somewhat stronger component is a <100>-fibre texture, similar to that in the experimentally deformed B-1 pyrite. The other one is a <111> - fibre texture similar to the intital B-1 preferred orientation. After 30% shortening oblique to both initial fibre axes at 600°C weak <110>- and <111>-fibre textures have developed. The experimentally produced fabrics have developed during deformation involving dislocation flow, dynamic recrystallisation and some microcracking. Intergranular sliding may also have been involved. Differences between lattice preferred orientations developed in the 600°C and 700°C experiments are interpreted to indicate a change in the dominant flow mechanism with changing temperature.
In comparison with other cubic minerals that have been deformed experimentally by dislocation flow mechanisms, the pyrite shows an unusually weak preferred orientation which can be detected only by means of neutron diffraction texture goniometry.
Single photon laser ionization time-of-flight mass spectroscopy (SPI-TOFMS) is used to monitor the gaseous fluxes of Ga and Asn, during molecular beam epitaxy of GaAs. This noninvasive and real-time probe measures densities, and hence fluxes, of multiple chemical species impinging on or scattered from a substrate during conventional MBE. With single photon ionization at 118 nm (10.5 eV, ninth harmonic of Nd:YAG laser), the photon energy is large enough to ionize the species, but insufficient to both ionize and fragment. The lack of molecular dissociation of As2 and As4 greatly simplifies the interpretation of mass spectra. Additionally, the geometry of the single photon ionization TOFMS permits simultaneous film growth monitoring using RHEED. Results will be presented on the probing of scattering and desorption of III-V MBE species during GaAs growth. This technique promises to be a valuable in-situ diagnostic for III-V and II-VI MBE.
The development of a constitutive model describing the deformation response of plasma sprayed metal matrix composite (MMC) foils during hot isostatic pressing (HIP) is described. A representative volume element of the composite is chosen whose constitutive behavior, including inelastic compressibility, is analyzed for the particular case of constrained uniaxial compression. Results of this preliminary model for the case of a SCS–6/Ti–14wt%Al–21wt%Nb intermetallic matrix composite are presented in the form of a density–pressure HIP map.
Photoreactions in polyalkylsilyne thin films induced by ArFlaser (193 nm) irradiation have been examined. Photoexcitation of the σ-conjugated Si-network at 193 nm (6.42 eV) results in Si-Si bond scission and alkyl-group desorption when irradiated in a vacuum. In addition to these processes, efficient (up to 7% quantum efficiency) insertion of oxygen into the Si backbone occurs when the irradiation is performed in air, resulting in the formation of a siloxane. Both infrared and X-ray photoelectron spectroscopies indicate a higher oxygen coordination about the Si atoms in the oxidized product than observed for linear polysilanes. This higher oxygen coordination indicates a siloxane network. The polysilynes have been demonstrated as deep UV photoresists and may have additional applications as precursors for thin film or binary optical components.