Differential Stress Levels Research Articles

Mechanical Response and Microprocesses of Reconsolidating Crushed Salt at Elevated Temperature

Design, analysis and performance assessment of potential salt repositories for heat-generating nuclear waste require knowledge of thermal, mechanical, and fluid transport properties of reconsolidating granular salt. To inform salt repository evaluations, we have undertaken an experimental program to determine Bulk and Young’s moduli and Poisson’s ratio of reconsolidated granular salt as a function of porosity and temperature and to establish the deformational processes by which the salt reconsolidates. Tests were conducted at 100, 175, and 250 °C. In hydrostatic tests, confining pressure is increased to 20 MPa with periodic unload/reload loops to determine K. Volume strain increases with increasing temperature. In shear tests at 2.5 and 5 MPa confining pressure, after confining pressure is applied, the crushed salt is subjected to a differential stress, with periodic unload/reload loops to determine E and ν. At predetermined differential stress levels the stress is held constant and the salt consolidates. Displacement gages mounted on the samples show little lateral deformation until the samples reach a porosity of ~10 %. Interestingly, vapor is vented only for 250 °C tests and condenses at the vent port. It is hypothesized that the brine originates from fluid inclusions, which were made accessible by heating and intragranular deformational processes including decrepitation. Identification and documentation of consolidation processes are inferred from optical and scanning electron microstructural observations. Densification at low porosity is enhanced by water film on grain boundaries that enables solution-precipitation phenomena.

Production and characterization of thin film group IIIB, IVB and rare earth hydrides by reactive evaporation

A recent short history of reactive evaporation by D. M. Mattox [History Corner—A Short History of Reactive Evaporation, SVC Bulletin (Society of Vacuum Coaters, Spring 2014), p. 50–51] describes various methods for producing oxides, nitrides, carbides, and some compounds, but hydrides were not mentioned. A study was performed in the mid-1970s at the General Electric Company Neutron Devices Department in Largo, FL, by the author to study preparation of thin film hydrides using reactive evaporation and to determine their unique characteristics and properties. Films were produced of scandium (Sc), yttrium (Y), titanium (Ti), zirconium (Zr), and the rare earth praseodymium (Pr), neodymium (Nd), gadolinium (Gd), dysprosium (Dy), and erbium (Er) hydrides by hot crucible filament and electron beam evaporation in atmospheres of deuterium and tritium gases. All-metal vacuum systems were used and those used with tritium were dedicated for this processing. Thin film test samples 1000 nm thick were prepared on 1.27 cm diameter molybdenum disk substrates for each occluder (i.e., an element that can react with hydrogen to form a hydride) material. Loading characteristics as determined by gas-to-metal atomic ratios, oxidation characteristics as determined by argon–sputter Auger analysis, film structure as determined by scanning electron microscope analysis, and film stress properties as determined by a double resonator technique were used to define properties of interest. Results showed hydrogen-to-metal atomic ratios varied from 1.5 to 2.0 with near maximum loading for all but Pr and Nd occluders which correlated with the oxidation levels observed, with all occluder oxidation levels being variable due to vacuum system internal processing conditions and the materials used. Surface oxide levels varied from ∼80 Å to over 1000 Å. For most films studied, results showed that a maximum loading ratio of near 2.0 and a minimum surface oxide level of ∼80 Å could be obtained with a bulk film oxygen level of ∼0.54 oxygen as determined by microprobe analysis when an evaporation rate of ∼0.313 mg/cm2 min was used in an atmosphere of D2 or T2 gas at a system deposition pressure of 1 × 10−3 Torr (1.33 × 10−1 Pa) in an evaporation time of ∼2 min. Platelet type (i.e., a film microstructure showing an overlay of flat plates with large grain sizes) film structures were observed for most films with some film mechanical properties determined (i.e., grain size and Vickers μ-hardness), and reduced stress levels were seen with initial normalized differential (tensile) stress levels being (1.0–4.0) × 108 dyne/cm2 for tritium loaded samples and (1.5 ± 0.5) × 109 dyne/cm2 for deuterium loaded samples. Also, stress aging characteristics were determined for some hydride films prepared in a radioactive tritium gas atmosphere. Tritium loading, however, had the undesirable characteristic of having to dispose of the internal processing system fixtures, which can be minimized, but the reactive evaporation technique produced desirable thin films.

Differential oxidative stress levels in mothers with preeclampsia delivering male and female babies

Objectives: Increased oxidative stress is known to be associated with pregnancy complications like preeclampsia (PE). We hypothesize that increased maternal oxidative stress may differentially affect/program the pregnancy outcome during early postnatal periods in male and female babies.Materials and methods: One-hundred three healthy pregnant women (gestation ≥37 weeks) were recruited for the normotensive control (NC) group and 57 women with term-preeclampsia (T-PE; gestation ≥37 weeks) and 28 women with preterm-preeclampsia (PT-PE; gestation <37 weeks) were also recruited. All infants were followed for anthropometric measurements until six months of age.Results: Higher maternal plasma malondialdehyde (MDA) and erythrocyte superoxide dismutase and glutathione peroxidase (GPx) levels were observed in both T-PE and PT-PE groups. Higher maternal levels of MDA and GPx were seen in mothers delivering male babies in T-PE and PT-PE groups, respectively, as compared to mothers delivering female babies. Babies born to mothers with PT-PE showed poor growth and development on all the anthropometric parameters compared to those born to mothers with T-PE and NC.Conclusion: The altered levels of oxidative stress and antioxidant enzymes in mothers with PE delivering male babies suggest that they may be at higher risk for developing metabolic and neurodevelopmental disorders than female babies.

Abstract 4550: Differential PARP inhibitors' effects on cell cycle and consequently homologous DNA damage repair

Abstract Background: Poly (ADP)-ribose polymerase (PARP) inhibition has been explored in pre-clinical and clinical studies with greatest successes demonstrated in homologous DNA damage repair (HDR) pathway-deficient cancer patients. PARP inhibitor's (PARPis) potency to inhibit PARP's catalytic activity is well established; however non-catalytic effects that may add to their therapeutic properties are not fully understood. Our objective was to comparatively evaluate non-catalytic effects of olaparib and veliparib, the two most widely used PARPis in clinical trials, with a particular focus on cell cycle effects and HDR. Methods: To measure DNA damage repair activity upon PARPi treatment, we used a well-established DR-GFP reporter assay in two model cell lines, U2OSDR-GFP and H1299DR-GFP. Cell cycle progression was assessed by propidium iodide and monitored by flow cytometry. Depletion of targeted mRNAs was performed by standard siRNA knock-down technique using electroporation for transfection. Immunoblotting was used to confirm cell cycle results and demonstrate replicative stress on the protein expression levels. Results: We found a dramatic decrease in DNA damage repair activity in olaparib- versus veliparib-treated U2OSDR-GFP p53 wild type cells, regardless of inhibitory potency. This decrease in HDR activity was a result of olaparib triggering a cell cycle arrest-like effect as a response to strong replicative stress. Lack of the same effect in p53-null cells suggests that olaparib's effect is p53-dependent, which was confirmed in U2OSDR-GFP cells depleted of p53. Finally, CHK1 is strongly phosphorylated in cells treated with olaparib but not veliparib, confirming cells differential response to these two PARPis. Conclusion: These data demonstrate that olaparib and veliparib differ in their non-catalytic inhibitory effects, with olaparib but not veliparib mitigating DNA damage repair activity via cell cycle arrest-like effects in a p53-WT background. Moreover, olaparib but not veliparib triggers CHK1 phosphorylation, which suggests differential levels of replicative stress. This new insight into olaparib's and veliparib's mechanism of action should be considered when developing inclusion criteria for treatment of cancer patients with these PARP inhibitors. Citation Format: Petar Jelinic, Douglas A. Levine. Differential PARP inhibitors' effects on cell cycle and consequently homologous DNA damage repair. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 4550. doi:10.1158/1538-7445.AM2014-4550

Balancing reservoir creation and seismic hazard in enhanced geothermal systems

SUMMARY Fractureshear-dilatancyisanessentialprocessforenhancingthepermeabilityofdeepgeothermal reservoirs, and is usually accompanied by the radiation of seismic waves. However, the hazard and risk perspective of induced seismicity research typically focuses only on the question of how to reduce the occurrence of induced earthquakes. Here we present a quantitative analysisofseismichazardasafunctionofthetwokeyfactorsdefininganenhancedgeothermal system: The permeability enhancement, and the size of the stimulated reservoir. Our model has two coupled components: (1) a pressure diffusion model and (2) a stochastic seismicity model. Permeability is increased in the source area of each induced earthquake depending on the amount of slip, which is determined by the magnitude. We show that the few largest earthquakes (i.e. 5–10 events with M ≥ 1.5) contribute more than half of the total reservoir stimulation. The results further indicate that planning and controlling of reservoir engineering operations may be compromised by the considerable variability of maximum observed magnitude, reservoir size, the Gutenberg–Richter b-value and Shapiro’s seismogenic index (i.e. a measure of seismic reactivity of a reservoir) that arises from the intrinsic stochastic nature of induced seismicity. We also find that injection volume has a large impact on both reservoir size and seismic hazard. Injection rate and injection scheme have a negligible effect. The impact of site-specific parameters on seismicity and reservoir properties is greater than that of the injected volume. In particular, conditions that lead to high b-values—possibly a low differential stress level—have a high impact on seismic hazard, but also reduce the efficiency of the stimulation in terms of permeability enhancement. Under such conditions, target reservoir permeability can still be achieved without reaching an unacceptable level of seismic hazard, if either the initial reservoir permeability is high or if several fractures are stimulated. The proposed methodology is a first step towards including induced seismic hazard analysis into the design of reservoir stimulation in a quantitative and robust manner.

Exploring the multidimensionality of stature variation in the past through comparisons of archaeological and living populations.

Adult stature variation is commonly attributed to differential stress-levels during development. However, due to selective mortality and heterogeneous frailty, a population's tall stature may be more indicative of high selective pressures than of positive life conditions. This article examines stature in a biocultural context and draws parallels between bioarchaeological and living populations to explore the multidimensionality of stature variation in the past. This study investigates: 1) stature differences between archaeological populations exposed to low or high stress (inferred from skeletal indicators); 2) similarities in growth retardation patterns between archaeological and living groups; and 3) the apportionment of variance in growth outcomes at the regional level in archaeological and living populations. Anatomical stature estimates were examined in relation to skeletal stress indicators (cribra orbitalia, porotic hyperostosis, linear enamel hypoplasia) in two medieval bioarchaeological populations. Stature and biocultural information were gathered for comparative living samples from South America. Results indicate 1) significant (P < 0.01) differences in stature between groups exposed to different levels of skeletal stress; 2) greater prevalence of stunting among living groups, with similar patterns in socially stratified archaeological and modern groups; and 3) a degree of regional variance in growth outcomes consistent with that observed for highly selected traits. The relationship between early stress and growth is confounded by several factors-including catch-up growth, cultural buffering, and social inequality. The interpretations of early life conditions based on the relationship between stress and stature should be advanced with caution.

Prenatal vitamin C deficiency results in differential levels of oxidative stress during late gestation in foetal guinea pig brains

Antioxidant defences are comparatively low during foetal development making the brain particularly susceptible to oxidative stress during antioxidant deficiencies. The brain is one of the organs containing the highest concentration of vitamin C (VitC) and VitC deficiency during foetal development may place the brain at risk of redox status imbalance. In the present study, we investigated the developmental pattern and effect of VitC deficiency on antioxidants, vitamin E and superoxide dismutase (SOD), assessed oxidative damage by measuring malondialdehyde (MDA), hydroxynonenal (HNE) and nitrotyrosine (NT) and analysed gene and protein expression of apoptosis marker caspase-3 in the guinea pig foetal brain at two gestational (GD) time points, GD 45/pre-term and GD 56/near term following either a VitC sufficient (CTRL) or deficient (DEF) maternal dietary regime. We show that except for SOD, antioxidants and oxidative damage markers are differentially expressed between the two GDs, with high VitC (p<0.0001), NT modified proteins (p<0.0001) and active caspase-3 levels (p<0.05) at pre-term and high vitamin E levels (p<0.0001), HNE (p<0.0001) and MDA (p<0.0001) at near term. VitC deficiency significantly increased SOD activity (p<0.0001) compared to CTRLs at both GDs indicating a compensatory response, however, low levels of VitC significantly elevated MDA levels (p<0.05) in DEF at near term. Our results show a differential regulation of the investigated markers during late gestation and suggest that immature brains are susceptible to oxidative stress due to prenatal vitC deficiency in spite of an induction of protective adaptation mechanisms.

Ursolic acid differentially modulates apoptosis in skin melanoma and retinal pigment epithelial cells exposed to UV–VIS broadband radiation

The signaling pathways via mTOR (mammalian target of rapamycin) and AMPK (AMP-activated protein kinase) play key roles in transcription, translation and carcinogenesis, and may be activated by light exposure. These pathways can be modulated by naturally occurring compounds, such as the triterpenoid, ursolic acid (UA). Previously, the transcription factors p53 and NF-κB, which transactivate mitochondrial apoptosis-related genes, were shown to be differentially modulated by UA. UA-modulated apoptosis, following exposure to UV-VIS radiation (ultraviolet to visible light broadband radiation, hereafter abbreviated to UVR), is observed to correspond to differential levels of oxidative stress in retinal pigment epithelial (RPE) and skin melanoma (SM) cells. The cellular response to this phytochemical was characterized using western blot, flow cytometry, microscopy with reactive oxidative species probes MitoTracker and dihydroethidium, and membrane permeability assay. UA pretreatment potentiated cell cycle arrest and UVR-induced apoptosis selectively in SM cells while reducing photo-oxidative stress in the DNA of RPE cells presumably by antioxidant activity of UA. Mechanistically, the nuclear transportation of p65 and p53 was reduced by UA administration prior to UVR exposure while the levels of p65 and p53 nuclear transportation in SM cells were sustained at a substantially higher level. Finally, the mitochondrial functional assay showed that UVR induced the collapse of the mitochondrial membrane potential, and this effect was exacerbated by rapamycin or UA pretreatment in SM preferentially. These results were consistent with reduced proliferation observed in the clonogenic assay, indicating that UA treatment enhanced the phototoxicity of UVR, by modulating the activation of p53 and NF-κB and initiating a mitogenic response to optical radiation that triggered mitochondria-dependent apoptosis, particularly in skin melanoma cells. The study indicates that this compound has multiple actions with the potential for protecting normal cells while sensitizing skin melanoma cells to UV irradiation.

Low stress deformation of garnet by incongruent dissolution precipitation creep

Microstructures indicating incongruent dissolution precipitation creep of garnet in eclogite-facies graphitic micaschist (Tauern window, Eastern Alps) are investigated. Garnet dissolution is observed where garnet poikiloblasts grown at eclogite facies metamorphism approached each other as a consequence of progressive deformation during exhumation, with estimated P-T-conditions between 570 °C, 1.7 GPa and 470 °C, 0.9 GPa. The poikiloblasts are separated by a dissolution seam and flanked by strain shadows filled with quartz, white mica, and chlorite; there is no evidence for crystal plastic deformation of garnet. Two cases are investigated: (A) stylolitic contact zone, (B) smooth contact zone. In both cases, internal fabrics of the poikiloblasts and concentric chemical zoning are truncated. Material previously forming inclusions in the garnet poikiloblasts is now passively enriched in a dissolution seam, the original microstructure of fine-grained mica–graphite aggregates remaining preserved. Though microstructures suggest that garnet dissolution was driven by local stress concentration, the level of differential stress remained too low for plastic deformation of the fine-grained white mica-graphite aggregates set free from the stress supporting garnet. Incongruent dissolution precipitation creep appears to be a particularly effective deformation mechanism at low stress in a subduction channel.

Simultaneous acoustic emissions monitoring and synchrotron X-ray diffraction at high pressure and temperature: Calibration and application to serpentinite dehydration

We have successfully developed an experimental setup that allows collecting in situ X-ray powder diffraction and simultaneously recording full waveform acoustic emissions (AE) at high pressure and temperature (PT) in a DIA multi-anvil device. This setup is a powerful tool for investigating rock embrittlement at high PT due to phase transitions and/or mineral reactions since both reaction progress (and kinetics) and AE triggering can be simultaneously monitored. The dehydration of natural serpentinite samples (antigorite-rich) under deviatoric stress has been investigated by this method since antigorite dehydration is believed to trigger intermediate depth earthquakes through dehydration embrittlement. We performed, beforehand, a series of tests on the cold compression of reference materials with contrasted mechanical behaviors (quartz beads and kaolinite powder). Due to grain crushing, cold compression of quartz gave rise to numerous AE events (several hundreds), which were located within the sample. Cold compression and heating of kaolinite, a ductile material, yielded no AEs, demonstrating that the pressure assembly is noiseless. Unexpectedly, antigorite-rich serpentinite samples produced no detectable AEs in the course of their dehydration under the differential stress imposed by alumina waveguides. The only AEs that were recorded occurred during cold compression. Sample microstructures indicate that conjugate faults inherited from the cold compression stage are activated during or after dehydration of the sample. The “aseismic” slip along these faults could be attributed to the presence of talc (or a talc-like phase) or of fine-grained materials (dehydration reaction products) in the fault gouge. Furthermore, AE triggering can also be influenced by hydraulic diffusivity and the differential stress level on the sample, two parameters that are not controlled in conventional multi-anvil experiments. Our results highlight the fact that coupling between dehydration reactions and seismicity might not be as straightforward as previously thought. In fact, fast reaction kinetics or high reaction extent may inhibit the nucleation of mechanical instabilities through rapid stress relaxation of the solid matrix.

Underlying mechanism of dual hysteresis in NiMnGa single crystals

NiMnGa single crystals are compressed in the [001] orientation at room temperature. The stress–strain response exhibits multiple stages as the deformation proceeds. Initially, the response exhibits a stress drop in the stress–strain curve preceding a plateau stress. By contrast, the second transition, which occurs at five times the initial critical transformation stress, produces a work hardening like response. Complete pseudoelastic (PE) recovery ensues upon unloading with the reverse transformation exhibiting the same two-stages. Furthermore, for the dual hysteresis that results, the second hysteresis is nearly four times wider than the first. The underlying transformation path for each stage is ascertained from local strain analysis utilizing variable magnification in situ digital image correlation (DIC). We distinguish three different morphological transitions; band formation, phase front propagation, and heterogeneous growth. The morphologies can be attributed to austenite undergoing the successive transitions 10M→14M (modulated to modulated) and 10M→L10 (modulated to non-modulated). Differential critical stress and hysteresis levels are rationalized based on the initial modulated-to-modulated and successive modulated-to-non-modulated transition. The strain–temperature response is reported, as well, and exhibits a tiny thermal hysteresis (5°C), which is attributed to the modulated-to-modulated conversion.

Individual differences in cocaine-induced locomotor activity of male Sprague–Dawley rats are not explained by plasma corticosterone levels

Humans differ in their initial response to, and subsequent abuse of, addictive drugs like cocaine. Rodents also exhibit marked individual differences in responsiveness to cocaine. Previously, we classified male Sprague–Dawley rats as either low or high cocaine responders (LCRs or HCRs, respectively), based on their acute low-dose cocaine-induced locomotor activity, and found that with repeated drug exposure LCRs exhibit greater cocaine locomotor sensitization, reward and reinforcement than HCRs. Differential cocaine-induced increases in striatal dopamine help to explain the LCR/HCR phenotypes. Differential levels of stress and/or anxiety could also contribute but have not been explored. Here we measured open-field activity and plasma corticosterone levels both pre- and post-cocaine treatment in LCRs, HCRs, and saline-treated controls. The three groups did not differ in baseline locomotor activity or corticosterone levels. Importantly, LCR/HCR differences in corticosterone levels were also not observed following acute cocaine (10 mg/kg, i.p.), when cocaine induced approximately 3.5-fold greater locomotor activity in HCRs than LCRs. Additionally, there were no LCR/HCR differences in plasma corticosterone levels following 5 days of once-daily cocaine, during which time LCRs developed locomotor sensitization such that their cocaine-induced locomotor activity no longer differed from that of HCRs. Likewise, there were no group activity differences in any of four concentric zones within the open-field chamber. In summary, neither plasma corticosterone levels nor thigmotaxis-type anxiety appears to be a factor that contributes to the observed cocaine-induced LCR/HCR behavioral differences.

Microstructural Inhomogeneity and Mechanical Anisotropy Associated with Bedding in Rothbach Sandstone

This study present the result of conventional triaxial tests conducted on samples of Rothbach sandstone cored parallel, oblique (at 45 degrees) and perpendicular to the bedding at effective pressures ranging from 5 to 250 MPa. Mechanical and microstructural data were used to determine the role of the bedding on mechanical strength and failure mode. We find that samples cored at 45 degrees to the bedding yield at intermediate level of differential stress between the ones for parallel and perpendicular samples at all effective pressures. Strain localization at high confining pressure (i.e., in the compactive domain) is observed in samples perpendicular and oblique to the bedding but not in samples cored parallel to the bedding. However, porosity reduction is comparable whether compactive shear bands, compaction bands or homogeneous cataclastic flow develop. Microstructural data suggest that (1) mechanical anisotropy is controlled by a preferred intergranular contact alignment parallel to the bedding and that (2) localization of compaction is controlled by bedding laminations and grain scale heterogeneity, which both prevent the development of well localized compaction features.

Preeclampsia More Than 1 Disease

In this issue of Hypertension , Rasmussen and Irgens provide strong support for the relationship of preeclampsia and intrauterine growth restriction (IUGR). They also provide data that support but also some that argue against the concept that the pregnancy complication, preeclampsia, may be more than one disease.1 In previous studies these authors demonstrated that women who have had a growth-restricted infant without preeclampsia are more likely to have preeclampsia in a subsequent pregnancy.2 Those data and similar findings in the current study support pathological findings indicating the similarity of IUGR and preeclampsia.3 In preeclampsia, IUGR and interestingly also in about one third of cases of preterm birth,4 the maternal myometrial and decidual vessels perfusing the placental site do not undergo the normal remodeling of pregnancy. In normal pregnancy trophoblastic invasion is associated with a greatly increased diameter and removal of vascular smooth muscle from the wall of these vessels. This results in large diameter, flaccid, unresponsive tubes that greatly increase placental perfusion. These changes are not present in pregnancies complicated by IUGR, preeclampsia, and some with preterm births. Implicit in the current study is the concept that preterm birth as well as IUGR is related to subsequent preeclampsia. Although preterm birth is not assessed directly, the effect of low birth weight (IUGR and preterm birth) was greater than the effect of IUGR alone. In a far smaller study our group was able to more directly support the relationship of preterm birth and preeclampsia, as women with early onset preeclampsia were more likely to have preterm birth in a subsequent nonpreeclamptic pregnancy.5 The current study extends the prior observation of the relationship of IUGR and preeclampsia but also raises other interesting points. In this larger study the authors were …

Field rheology and structural evolution of the Homestake shear zone, Colorado

Proterozoic tectonites within the Homestake shear zone (HSZ) in the northern Sawatch Range, Colorado, record two major cycles of progressive deformation under contrasting P–T conditions. Field relations and microstructures in these tectonites can be used to constrain the geometry, kinematics, and rheology of rocks in the HSZ during these events. The first deformation cycle occurred ∼1.7 Ga at temperatures near the granite solidus and produced structures indicative of pervasive viscous flow at low differential stress levels. The second deformation cycle at ∼1.4 Ga resulted in localized plastic and brittle failure concentrated in relatively narrow shear zones and seismogenic faults. This second deformation occurred at temperatures of 350–450°C and produced mylonite, ultramylonite, and pseudotachylyte. Overprinting relationships between brittle-frictional faults and plastic shear zones suggest that both modes of deformation were active at about the same time. Thus, the latter deformation cycle probably occurred near the brittle-plastic transition. Simple calculations using standard rheologic relationships show that tectonic loads of 300–400 MPa—sufficient to drive brittle failure—could have been transmitted by ductile ultramylonite zones deforming at relatively high strain rates (on the order of 10 −9 –10 −11 ). Thus, plastic shear zones and brittle-frictional faults probably acted together as a dynamically coupled deformation system.

Differential levels of stress in caregivers of brain tumor patients—observations from a pilot study

Caregivers of patients with brain tumors (BT) experience elevated levels of stress. Using pilot data, we sought to determine which caregivers are at risk for experiencing elevated levels of stress based on caregiver-demographic and patient-medical information. Using a convenience sample of 60 caregivers, participants were asked to complete the Perceived Stress Scale and to provide demographic information. The Perceived Stress Scale is a 10-item scale designed to measure the degree to which situations in life are perceived as stressful. Demographic information was collected using self-reported measures. Medical data concerning tumor grade of patient were obtained from most recent medical note. Data for study were standardized using z-scores and analyzed using SPSS software. Seventy-two percent (n=43) of caregivers reported experiencing elevated levels of stress within the last 30 days. Thirty-five percent (n=21) of the sample scored at least one standard deviation above the mean. A statistical trend [F(1, 57)=3.12, p=0.08] exists between caregiver stress and tumor grade of patients for which they are providing care. Caregivers of patients with BT experience significant stress. Furthermore, this data provide an indication of the profound levels of stress these caregivers experience. Caregivers of patients with grade I/II tumors are at increased risk for experiencing stress. Younger caregiver age and higher levels of education were also found to correlate to higher levels of stress.

Sex and rank in competitive brood hierarchies influence stress levels in nestlings of a sexually dimorphic bird

Studies of sibling competition within brood hierarchies have rarely assessed simultaneously the effects of sex and rank in the brood hierarchy on traits other than offspring mortality and differential growth. We studied the expression of heat-shock proteins (Hsps) to assess the physiological stress response to different combinations of sex and position within competitive brood hierarchies in the black kite Milvus migrans (Bodd.), a sexually dimorphic raptor showing facultative siblicide. Senior males showed higher stress levels than did senior females and younger siblings of each sex as revealed by Hsp60 values. The analysis of Hsp70 levels indicated that nestlings from broods in which the senior chick was a male showed higher stress levels than did nestlings from broods in which the senior chick was a female. In addition, levels of Hsp60 were related negatively to nutritional condition expressed as levels of plasmatic albumin. This suggests that the sex of senior chicks may be key in determining their stress level and that of their siblings, which is probably associated with sibling competition by fighting within brood hierarchies. The comparatively higher stress levels of senior males (and their siblings) may be a consequence of their ability to exploit their potential advantage from being the head start while avoiding a possible competitive disadvantage from being the smaller sex, independent of environmental conditions determining the probability of brood reduction. Differential stress levels depending on sex and rank in the brood hierarchy may be a consequence of parental control of offspring behaviour through differential resource allocation (e.g. yolk androgens) or it may reflect adaptations of particular chicks (senior males) to enhance their competitive ability within brood hierarchies.

Investigation of the martensitic-like transformation from Mg2GeO4 olivine to its spinel structure polymorph

A coherent mechanism for the transformation of olivine to its spinel structure polymorph has been investigated in Mg 2 GeO 4 olivine at conditions ranging from 6 GPa to 18 GPa at 300 to 1250 °C using a multi-anvil apparatus. This transformation mechanism, which produces plates of spinel lying parallel to the (100) planes in olivine, becomes increasingly important above 10 GPa at temperatures between 300 and 400 °C. The primary effect of temperature above 400 °C is to increase the length of the lamellae. The primary effect of pressure is to increase the number of lamellae that have nucleated. The distribution of transformation is very inhomogeneous. Lamellae first appear in patches associated with grain edges and corners. As the degree of transformation increases, patches become more extensive and more heavily populated until the majority, if not all grains, contain large numbers of lamellae that span large portions of their host grains. The mechanism that produces the lamellae requires three factors, high pressure overstep of the equilibrium boundary, some level of differential stress (either microscopic or macroscopic), and high enough temperature to facilitate rearrangement of the cations. It is most consistent with a martensitic-like transformation mechanism. The results of this study suggest that olivine may exhibit similar behavior in cold, rapidly subducting lithospheric slabs. If conditions are too cold for olivine to transform by reconstructive nucleation and growth, it could instead progressively transform by the martensitic-like mechanism as conditions deviate further and further from the equilibrium phase boundary.

Grain scale deformation in ultra-high-pressure metamorphic rocks—an indicator of rapid phase transformation

Conspicuous grain scale deformation is observed in some ultra-high-pressure (UHP) metamorphic rocks of the Dora Maira Massif, Western Alps, although no significant strain is discernible on the mesoscopic scale. In a jadeite–kyanite–quartz rock, some of the jadeite crystals reveal (100) deformation twins, indicating local differential stress levels above 0.3 GPa. Many kyanite crystals show marked kink or deformation bands, with a slip system (100)[001]. In contrast, the adjacent coarse-grained quartz matrix (grain size ca. 0.2 mm), which has formed from coesite during exhumation from >100 km depth, reveals a foam structure. The quartz grain boundary configuration is controlled by interfacial free energy, the grains are optically strain-free, and there is no crystallographic preferred orientation. Preservation of this foam microstructure, which indicates grain growth during low-stress annealing, precludes that deformation of the jadeite and kyanite crystals is a result of a late-stage low-temperature overprint. The orientation distribution of jadeite and kyanite with and without twins or deformation bands, respectively, has been investigated with a combination of universal stage and EBSD techniques. On the scale of a thin section, there is no preferred orientation of twinned jadeite and bent kyanite crystals and undeformed crystals, respectively. Thus, the orientation of the inferred local shortening direction is random. This precludes deformation driven by a homogeneous far field tectonic stress, but suggests an internally controlled stress field which is highly inhomogeneous on the scale of a few grain diameters. Laboratory experiments show that the coesite to quartz transformation proceeds within hours after decompression from 3.0 to 2.7 GPa at 800 °C. The microstructures of incompletely transformed samples indicate that the quartz growing at the expense of coesite undergoes crystal plastic deformation and recrystallizes with a very fine grain size during transformation. In this case, the deformation of quartz is attributed to the volumetric strain Δ V=+10% inherent in the coesite–quartz transformation, which causes a highly inhomogeneous stress field inside the sample related to the progress of the transformation. We propose that a similar process has taken place in the polyphase natural rock during exhumation, with the transient stresses causing mechanical twinning of jadeite and bending or kinking of kyanite. When the transformation had gone to completion, grain growth obliterated the microstructures of the quartz matrix, while the deformed jadeite and kyanite crystals preserved the record of inhomogeneous deformation at high temperatures. The peak differential stresses locally exceeded 0.3 GPa, which indicates very high strain rates and a correspondingly rapid transformation of coesite to quartz, comparable to the laboratory results.

Differential levels of diabetogenic stress in two new mouse models of obesity and type 2 diabetes.

The genetic basis for the more common forms of human obesity predisposing to insulin resistance and development of type 2 diabetes is multigenic rather than monogenic in origin. New mouse "diabesity" models have been created by combining independent diabetes risk-conferring quantitative trait loci from two unrelated parental strains: New Zealand Obese (NZO/HlLt) and Nonobese Nondiabetic (NON/Lt). F1 hybrid males, heterozygous at all polymorphic autosomal loci distinguishing the two parental strains, are driven to obesity-induced diabetes (diabesity) at high frequencies. This review focuses on two new recombinant congenic strains (RCSs) developed by introgressing multiple NZO/HlLt chromosomal segments into the nominally diabesity-resistant NON/Lt strain background. Both RCSs gain more weight than NON animals. Although exhibiting comparable weight gain and adiposity, only one of the two RCSs develops diabetes. Hence, these two RCSs will be instructive in elucidating genetic and pathophysiological differences underlying uncomplicated obesity syndromes versus diabetogenic obesity (diabesity) syndromes. Unlike mice with null mutations in a single gene producing morbid obesity, the new models develop a more moderate obesity produced by the interaction of numerous genes with relatively small effects. These RCSs are differentially sensitive to adverse side effects of thiazolidinediones and thus should be particularly useful for pharmacogenetic analyses.