Extinction Partially Reverts Structural Changes Associated with Remote Fear Memory

ERIC Educational Resources Information Center

Vetere, Gisella; Restivo, Leonardo; Novembre, Giovanni; Aceti, Massimiliano; Lumaca, Massimo; Ammassari-Teule, Martine

2011-01-01

Structural synaptic changes occur in medial prefrontal cortex circuits during remote memory formation. Whether extinction reverts or further reshapes these circuits is, however, unknown. Here we show that the number and the size of spines were enhanced in anterior cingulate (aCC) and infralimbic (ILC) cortices 36 d following contextual fear…

Photoinduced Trans-to-cis Phase Transition of Polycrystalline Azobenzene at Low Irradiance Occurs in the Solid State

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bhattacharjee, Ujjal; Freppon, Daniel; Men, Long

2017-07-09

The ability to produce large-scale, reversible structural changes in a variety of materials by photoexcitation of a wide variety of azobenzene derivatives has been recognized for almost two decades. Because photoexcitation of trans-azobenzene produces the cis-isomer in solution, it has generally been inferred that the macroscopic structural changes occurring in materials are also initiated by a similar large-amplitude trans-to-cis isomerization. This paper provides the first demonstration that a trans-to-cis photoisomerization occurs in polycrystalline azobenzene, and is consistent with the previously hypothesized nature of the trigger in the photoactuated mechanisms of the materials in question. It is also demonstrated that undermore » low irradiance, trans-to-cis isomerization occurs in the solid (not via a pre-melted phase); and the presence of the cis-isomer thus lowers the melting point of the sample, providing a liquid phase. A variety of experimental techniques were employed, including X-ray diffraction measurements of polycrystalline azobenzene during exposure to laser irradiation and fluorescence measurements of the solid sample. Finally, a practical consequence of this work is that it establishes trans-azobenzene as an easily obtainable and well-defined control for monitoring photoinduced structural changes in X-ray diffraction experiments, using easily accessible laser wavelengths.« less

Evidence from a rare case study for Hebbian-like changes in structural connectivity induced by long-term deep brain stimulation.

PubMed

van Hartevelt, Tim J; Cabral, Joana; Møller, Arne; FitzGerald, James J; Green, Alexander L; Aziz, Tipu Z; Deco, Gustavo; Kringelbach, Morten L

2015-01-01

It is unclear whether Hebbian-like learning occurs at the level of long-range white matter connections in humans, i.e., where measurable changes in structural connectivity (SC) are correlated with changes in functional connectivity. However, the behavioral changes observed after deep brain stimulation (DBS) suggest the existence of such Hebbian-like mechanisms occurring at the structural level with functional consequences. In this rare case study, we obtained the full network of white matter connections of one patient with Parkinson's disease (PD) before and after long-term DBS and combined it with a computational model of ongoing activity to investigate the effects of DBS-induced long-term structural changes. The results show that the long-term effects of DBS on resting-state functional connectivity is best obtained in the computational model by changing the structural weights from the subthalamic nucleus (STN) to the putamen and the thalamus in a Hebbian-like manner. Moreover, long-term DBS also significantly changed the SC towards normality in terms of model-based measures of segregation and integration of information processing, two key concepts of brain organization. This novel approach using computational models to model the effects of Hebbian-like changes in SC allowed us to causally identify the possible underlying neural mechanisms of long-term DBS using rare case study data. In time, this could help predict the efficacy of individual DBS targeting and identify novel DBS targets.

Changing Laws for Changing Families. Discussion Paper Number 9.

ERIC Educational Resources Information Center

Harper, Patricia

This paper examines changing family patterns in Australia over the last twenty-five years, and proposed or actual legislative changes which have occurred in this area. Statistics are presented which reflect the changing nature and structures of Australian families for the following categories: married families; one-parent families; de- facto…

Structural and functional changes during epileptogenesis in the mouse model of medial temporal lobe epilepsy.

PubMed

Dietrich, Yvan; Eliat, Pierre-Antoine; Dieuset, Gabriel; Saint-Jalmes, Herve; Pineau, Charles; Wendling, Fabrice; Martin, Benoit

2016-08-01

An important issue in epilepsy research is to understand the structural and functional modifications leading to chronic epilepsy, characterized by spontaneous recurrent seizures, after initial brain insult. To address this issue, we recorded and analyzed electroencephalography (EEG) and quantitative magnetic resonance imaging (MRI) data during epileptogenesis in the in vivo mouse model of Medial Temporal Lobe Epilepsy (MTLE, kainate). Besides, this model of epilepsy is a particular form of drug-resistant epilepsy. The results indicate that high-field (4.7T) MRI parameters (T2-weighted; T2-quantitative) allow to detect the gradual neuro-anatomical changes that occur during epileptogenesis while electrophysiological parameters (number and duration of Hippocampal Paroxysmal Discharges) allow to assess the dysfunctional changes through the quantification of epileptiform activity. We found a strong correlation between EEG-based markers (invasive recording) and MRI-based parameters (non-invasive) periodically computed over the `latent period' that spans over two weeks, on average. These results indicated that both structural and functional changes occur in the considered epilepsy model and are considered as biomarkers of the installation of epilepsy. Additionally, such structural and functional changes can also be observed in human temporal lobe epilepsy. Interestingly, MRI imaging parameters could be used to track early (day-7) structural changes (gliosis, cell loss) in the lesioned brain and to quantify the evolution of epileptogenesis after traumatic brain injury.

Postmortem Biochemistry of Meat and Fish.

ERIC Educational Resources Information Center

Hultin, Herbert O.

1984-01-01

Discusses structural and chemical features of muscle tissue. Emphasizes chemical and physical changes which occur during processing and storage and how these changes affect the eating quality of meat and fish. (JN)

Structural and functional changes in acute liver injury.

PubMed

Smuckler, E A

1976-06-01

Carbon tetrachloride produces liver cell injury in a variety of animal species. The first structurally recognizable changes occur in the endoplasmic reticulum, with alteration in ribosome-membrane interactions. Later there is an increase in intracellular fat, and the formation of tangled nets of the ergastoplasm. At no time are there changes in mitochondria or single membrane limited bodies in cells with intact plasmalemma, although a relative increase in cell sap may appear. In dead cells (those with plasmalemma discontinuties) crystalline deposits of calcium phosphatase may be noted. Functional changes are related to the endoplasmic reticulum and the plasma membrane. An early decrease in protein synthesis takes place; an accumulation of neutral lipid is related to this change. Later alterations in the ergastoplasmic functions (e.g., mixed function oxidation) occurs. Carbon tetrachloride is not the active agent; rather, a product of its metabolism, probably the CC1, free radical, is. The mechanisms of injury include macromolecular adduction and peroxide propagation. A third possibility includes a cascade effect with the production of secondary and tertiary products, also toxic in nature, with the ability to produce more widespread damage to intracellular structures.

Response of Fuelbed Characteristics to Restoration Treatments in Pinyon-Juniper-Encroached Shrublands on the Shivwits Plateau, Arizona

Treesearch

Helen Y. Smith; Sharon Hood; Matt Brooks; JR Matchett; Curt Deuser

2006-01-01

The recent encroachment of piñon (Pinus edulis) and juniper trees (Juniperus osteosperma) into historically shrub- and grass-dominated landscapes has caused major changes in ecosystem structure and function, including dramatic changes in fuel structure and fire regimes. Such encroachment is currently occurring on thousands of acres...

Extrusion of rice, bean, and corn starches: extrudate structure and molecular changes in amylose and amylopectin

USDA-ARS?s Scientific Manuscript database

This study evaluated the effects of starch source and amylose content on expansion ratio, density and texture of expanded extrudates, as well as the structural and molecular changes that occurred in starch granules as a function of extrusion. Rice starches (8%, 20% and 32% amylose), carioca bean sta...

Brain Structure-function Couplings (FY11)

DTIC Science & Technology

2012-01-01

influence time-evolving models of global brain function and dynamic changes in cognitive performance. Both structural and functional connections change on...Artifact Resistant Measure to Detect Cognitive EEG Activity During Locomotion. Journal of NeuroEngineering and Rehabilitation, submitted. 10...Specifically, identifying the communication between brain regions that occurs during tasks may provide information regarding the cognitive processes involved in

Biodegradation of the chitin-protein complex in crustacean cuticle

USGS Publications Warehouse

Artur, Stankiewicz B.; Mastalerz, Maria; Hof, C.H.J.; Bierstedt, A.; Flannery, M.B.; Briggs, D.E.G.; Evershed, R.P.

1998-01-01

Arthropod cuticles consist predominantly of chitin cross-linked with proteins. While there is some experimental evidence that this chitin-protein complex may resist decay, the chemical changes that occur during degradation have not been investigated in detail. The stomatopod crustacean Neogonodactylus oerstedii was decayed in the laboratory under anoxic conditions. A combination of pyrolysis-gas chromatography/mass spectrometry and FTIR revealed extensive chemical changes after just 2 weeks that resulted in a cuticle composition dominated by chitin. Quantitative analysis of amino acids (by HPLC) and chitin showed that the major loss of proteins and chitin occurred between weeks 1 and 2. After 8 weeks tyrosine, tryptophan and valine are the most prominent amino acid moieties, showing their resistance to degradation. The presence of cyclic ketones in the pyrolysates indicates that mucopolysaccharides or other bound non-chitinous carbohydrates are also resistant to decay. There is no evidence of structural degradation of chitin prior to 8 weeks when FTIR revealed a reduction in chitin-specific bands. The chemical changes are paralleled by structural changes in the cuticle, which becomes an increasingly open structure consisting of loose chitinous fibres. The rapid rate of decay in the experiments suggests that where chitin and protein are preserved in fossil cuticles degradation must have been inhibited.Arthropod cuticles consist predominantly of chitin cross-linked with proteins. While there is some experimental evidence that this chitin-protein complex may resist decay, the chemical changes that occur during degradation have not been investigated in detail. The stomatopod crustacean Neogonodactylus oerstedii was decayed in the laboratory under anoxic conditions. A combination of pyrolysis-gas chromatography/mass spectrometry and FTIR revealed extensive chemical changes after just 2 weeks that resulted in a cuticle composition dominated by chitin. Quantitative analysis of amino acids (by HPLC) and chitin showed that the major loss of proteins and chitin occurred between weeks 1 and 2. After 8 weeks tyrosine, tryptophan and valine are the most prominent amino acid moieties, showing their resistance to degradation. The presence of cyclic ketones in the pyrolysates indicates that mucopolysaccharides or other bound non-chitinous carbohydrates are also resistant to decay. There is no evidence of structural degradation of chitin prior to 8 weeks when FTIR revealed a reduction in chitin-specific bands. The chemical changes are paralleled by structural changes in the cuticle, which becomes an increasingly open structure consisting of loose chitinous fibres. The rapid rate of decay in the experiments suggests, that where chitin and protein are preserved in fossil cuticles degradation must have been inhibited.

Sequential events in the irreversible thermal denaturation of human brain-type creatine kinase by spectroscopic methods.

PubMed

Gao, Yan-Song; Su, Jing-Tan; Yan, Yong-Bin

2010-06-25

The non-cooperative or sequential events which occur during protein thermal denaturation are closely correlated with protein folding, stability, and physiological functions. In this research, the sequential events of human brain-type creatine kinase (hBBCK) thermal denaturation were studied by differential scanning calorimetry (DSC), CD, and intrinsic fluorescence spectroscopy. DSC experiments revealed that the thermal denaturation of hBBCK was calorimetrically irreversible. The existence of several endothermic peaks suggested that the denaturation involved stepwise conformational changes, which were further verified by the discrepancy in the transition curves obtained from various spectroscopic probes. During heating, the disruption of the active site structure occurred prior to the secondary and tertiary structural changes. The thermal unfolding and aggregation of hBBCK was found to occur through sequential events. This is quite different from that of muscle-type CK (MMCK). The results herein suggest that BBCK and MMCK undergo quite dissimilar thermal unfolding pathways, although they are highly conserved in the primary and tertiary structures. A minor difference in structure might endow the isoenzymes dissimilar local stabilities in structure, which further contribute to isoenzyme-specific thermal stabilities.

Characterizing the distinct structural changes associated with self-reported knee injury among individuals with incident knee osteoarthritis: Data from the osteoarthritis initiative.

PubMed

Davis, Julie E; Harkey, Matthew S; Ward, Robert J; Mackay, James W; Lu, Bing; Price, Lori Lyn; Eaton, Charles B; Barbe, Mary F; Lo, Grace H; McAlindon, Timothy E; Driban, Jeffrey B

2018-04-01

We aimed to characterize the agreement between distinct structural changes on magnetic resonance (MR) imaging and self-reported injury in the 12 months leading to incident common or accelerated knee osteoarthritis (KOA). We conducted a descriptive study using data from baseline and the first 4 annual visits of the Osteoarthritis Initiative. Knees had no radiographic KOA at baseline (Kellgren-Lawrence [KL]<2). We classified two groups: (1) accelerated KOA: a knee developed advanced-stage KOA (KL = 3 or 4) within 48 months and (2) common KOA: a knee increased in radiographic severity (excluding those with accelerated KOA). Adults were 1:1 matched based on sex. The index visit was when a person met the accelerated or common KOA criteria. We limited our sample to people with MR images and self-reported injury data at index visit and year prior. Among 226 people, we found fair agreement between self-reported injuries and distinct structural changes (kappa = 0.24 to 0.31). Most distinct structural changes were medial meniscal pathology. No distinct structural changes (e.g., root or radial tears) appeared to differ between adults who reported or did not report an injury; except, all subchondral fractures occurred in adults who developed accelerated KOA and reported an injury. While there is fair agreement between self-reported knee injuries and distinct structural changes, there is some discordance. Self-reported injury may represent a different construct from distinct structural changes that occur after joint trauma. Clin. Anat. 31:330-334, 2018. © 2018 Wiley Periodicals, Inc. © 2018 Wiley Periodicals, Inc.

Simultaneous optimisation of earwig hindwings for flight and folding

PubMed Central

Deiters, Julia; Kowalczyk, Wojciech; Seidl, Tobias

2016-01-01

ABSTRACT Earwig wings are highly foldable structures that lack internal muscles. The behaviour and shape changes of the wings during flight are yet unknown. We assume that they meet a great structural challenge to control the occurring deformations and prevent the wing from collapsing. At the folding structures especially, the wing could easily yield to the pressure. Detailed microscopy studies reveal adaptions in the structure and material which are not relevant for folding purposes. The wing is parted into two structurally different areas with, for example, a different trend or stiffness of the wing veins. The storage of stiff or more flexible material shows critical areas which undergo great changes or stress during flight. We verified this with high-speed video recordings. These reveal the extent of the occurring deformations and their locations, and support our assumptions. The video recordings reveal a dynamical change of a concave flexion line. In the static unfolded state, this flexion line blocks a folding line, so that the wing stays unfolded. However, during flight it extends and blocks a second critical folding line and prevents the wing from collapsing. With these results, more insight in passive wing control, especially within high foldable structures, is gained. PMID:27113958

21 CFR 807.26 - Amendments to establishment registration.

Code of Federal Regulations, 2010 CFR

2010-04-01

.... Changes in individual ownership, corporate or partnership structure, or location of an operation defined... if the changes occur at other times. This information shall be submitted within 30 days of such changes. Changes in the names of officers and/or directors of the corporation(s) shall be filed with the...

21 CFR 807.26 - Amendments to establishment registration.

Code of Federal Regulations, 2012 CFR

2012-04-01

.... Changes in individual ownership, corporate or partnership structure, or location of an operation defined... if the changes occur at other times. This information shall be submitted within 30 days of such changes. Changes in the names of officers and/or directors of the corporation(s) shall be filed with the...

21 CFR 807.26 - Amendments to establishment registration.

Code of Federal Regulations, 2011 CFR

2011-04-01

.... Changes in individual ownership, corporate or partnership structure, or location of an operation defined... if the changes occur at other times. This information shall be submitted within 30 days of such changes. Changes in the names of officers and/or directors of the corporation(s) shall be filed with the...

Development of Relational Reasoning during Adolescence

ERIC Educational Resources Information Center

Dumontheil, Iroise; Houlton, Rachael; Christoff, Kalina; Blakemore, Sarah-Jayne

2010-01-01

Non-linear changes in behaviour and in brain activity during adolescent development have been reported in a variety of cognitive tasks. These developmental changes are often interpreted as being a consequence of changes in brain structure, including non-linear changes in grey matter volumes, which occur during adolescence. However, very few…

Anatomic and physiologic changes of the aging kidney.

PubMed

Karam, Zeina; Tuazon, Jennifer

2013-08-01

Aging is associated with structural and functional changes in the kidney. Structural changes include glomerulosclerosis, thickening of the basement membrane, increase in mesangial matrix, tubulointerstitial fibrosis and arteriosclerosis. Glomerular filtration rate is maintained until the fourth decade of life, after which it declines. Parallel reductions in renal blood flow occur with redistribution of blood flow from the cortex to the medulla. Other functional changes include an increase in glomerular basement permeability and decreased ability to dilute or concentrate urine. Copyright © 2013 Elsevier Inc. All rights reserved.

Structural and phase transition changes of sodium dodecyl sulfate micellar solution in alcohols probed by small-angle neutron scattering (SANS)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Putra, Edy Giri Rachman; Patriati, Arum; Department of Chemistry, Faculty of Mathematics and Natural Sciences, University of Gadjah Mada, Bulaksumur, Yogyakarta 55281, Indonesia giri@batan.go.id

2015-04-16

Small-angle neutron scattering (SANS) measurements on 0.3M sodium dodecyl sulfate (SDS) micellar solutions have been performed in the presence of n-alcohols, from ethanol to decanol at different alcohol concentrations, 2–10 wt%. The ellipsoid micellar structure which occurred in the 0.3M SDS in aqueous solution with the size range of 30–50 Å has different behavior at various hydrocarbon chain length and concentration of alcohols. At low concentration and short chain-length of alcohols, such as ethanol, propanol, and butanol, the size of micelles reduced and had a spherical-like structure. The opposite effect occurred as medium to long chain alcohols, such as hexanol,more » octanol and decanol was added into the 0.3M SDS micellar solutions. The micelles structure changed to be more elongated in major axis and then crossed the critical phase transition from micellar solution into liquid crystal phase as lamellar structure emerged by further addition of alcohols. The inter-lamellar distances were also depending on the hydrocarbon chain length and concentration of alcohols. In the meantime, the persistent micellar structures occurred in addition of medium chain of n-alcohol, pentanol at all concentrations.« less

Conservation of protein structure over four billion years.

PubMed

Ingles-Prieto, Alvaro; Ibarra-Molero, Beatriz; Delgado-Delgado, Asuncion; Perez-Jimenez, Raul; Fernandez, Julio M; Gaucher, Eric A; Sanchez-Ruiz, Jose M; Gavira, Jose A

2013-09-03

Little is known about the evolution of protein structures and the degree of protein structure conservation over planetary time scales. Here, we report the X-ray crystal structures of seven laboratory resurrections of Precambrian thioredoxins dating up to approximately four billion years ago. Despite considerable sequence differences compared with extant enzymes, the ancestral proteins display the canonical thioredoxin fold, whereas only small structural changes have occurred over four billion years. This remarkable degree of structure conservation since a time near the last common ancestor of life supports a punctuated-equilibrium model of structure evolution in which the generation of new folds occurs over comparatively short periods and is followed by long periods of structural stasis. Copyright © 2013 Elsevier Ltd. All rights reserved.

Brain structural plasticity with spaceflight.

PubMed

Koppelmans, Vincent; Bloomberg, Jacob J; Mulavara, Ajitkumar P; Seidler, Rachael D

2016-01-01

Humans undergo extensive sensorimotor adaptation during spaceflight due to altered vestibular inputs and body unloading. No studies have yet evaluated the effects of spaceflight on human brain structure despite the fact that recently reported optic nerve structural changes are hypothesized to occur due to increased intracranial pressure occurring with microgravity. This is the first report on human brain structural changes with spaceflight. We evaluated retrospective longitudinal T2-weighted MRI scans and balance data from 27 astronauts (thirteen ~2-week shuttle crew members and fourteen ~6-month International Space Station crew members) to determine spaceflight effects on brain structure, and whether any pre to postflight brain changes are associated with balance changes. Data were obtained from the NASA Lifetime Surveillance of Astronaut Health. Brain scans were segmented into gray matter maps and normalized into MNI space using a stepwise approach through subject specific templates. Non-parametric permutation testing was used to analyze pre to postflight volumetric gray matter changes. We found extensive volumetric gray matter decreases, including large areas covering the temporal and frontal poles and around the orbits. This effect was larger in International Space Station versus shuttle crew members in some regions. There were bilateral focal gray matter increases within the medial primary somatosensory and motor cortex; i.e., the cerebral areas where the lower limbs are represented. These intriguing findings are observed in a retrospective data set; future prospective studies should probe the underlying mechanisms and behavioral consequences.

Different Structural Changes Occur in the Blue- and Green-Absorbing Proteorhodopsin During the Primary Photoreaction†

PubMed Central

Amsden, Jason J.; Kralj, Joel M.; Bergo, Vladislav B.; Spudich, Elena N.; Spudich, John L.; Rothschild, Kenneth J.

2013-01-01

We examine the structural changes during the primary photoreaction in blue-absorbing proteorhodopsin (BPR), a light-driven retinylidene proton pump, using low-temperature FTIR difference spectroscopy. Comparison of the light induced BPR difference spectrum recorded at 80 K to that of green-absorbing proteorhodopsin (GPR) reveals that there are several differences in the BPR and GPR primary photoreactions despite the similar structure of the retinal chromophore and all-trans → 13-cis isomerization. Strong bands near 1700 cm−1 assigned previously to a change in hydrogen bonding of Asn230 in GPR are still present in BPR but in addition bands in the same region are assigned on the basis of site-directed mutagenesis to changes occurring in Gln105. In the amide II region bands are assigned on the basis of total-N15 labeling to structural changes of the protein backbone, although no such bands were previously observed for GPR. A band at 3642 cm−1 in BPR, assigned to the OH stretching mode of a water molecule on the basis of H218O substitution, appears at a different frequency than a band at 3626 cm−1 previously assigned to a water molecule in GPR. However, the substitution of Gln105 for Leu105 in BPR leads to the appearance of both bands at 3642 and 3626 cm−1 indicating the waters assigned in BPR and GPR exist in separate distinct locations and can coexist in the GPR-like Q105L mutant of BPR. These results indicate that there exist significant differences in the conformational changes occurring in these two types proteorhodopsin during the initial photoreaction despite their similar chromophores structures, which might reflect a different arrangement of water in the active site as well as substitution of a hydrophilic for hydrophobic residue at residue 105. PMID:18842006

Progressive Brain Structural Changes Mapped as Psychosis Develops in ‘At Risk’ Individuals

PubMed Central

Sun, Daqiang; Phillips, Lisa; Velakoulis, Dennis; Yung, Alison; McGorry, Patrick D.; Wood, Stephen J.; van Erp, Theo G. M.; Thompson, Paul M.; Toga, Arthur W.; Cannon, Tyrone D.; Pantelis, Christos

2009-01-01

Background Schizophrenia and related psychoses are associated with brain structural abnormalities. Recent findings in ‘at risk’ populations have identified progressive changes in various brain regions preceding illness onset, while changes especially in prefrontal and superior temporal regions have been demonstrated in first-episode schizophrenia patients. However, the timing of the cortical changes and their regional extent, relative to the emergence of psychosis, has not been clarified. We followed individuals at high-risk for psychosis to determine whether structural changes in the cerebral cortex occur with the onset of psychosis. We hypothesized that progressive volume loss occurs in prefrontal regions during the transition to psychosis. Methods 35 individuals at ultra-high risk (UHR) for developing psychosis, of whom 12 experienced psychotic onset by 1-year follow-up (‘converters’), participated in a longitudinal structural MRI study. Baseline and follow-up T1-weighted MR images were acquired and longitudinal brain surface contractions were assessed using Cortical Pattern Matching. Results Significantly greater brain contraction was found in the right prefrontal region in the ‘converters’ compared with UHR cases who did not develop psychosis (‘non-converters’). Conclusions These findings show cortical volume loss is associated with the onset of psychosis, indicating ongoing pathological processes during the transition stage to illness. The prefrontal volume loss is in line with structural and functional abnormalities in schizophrenia, suggesting a critical role for this change in the development of psychosis. PMID:19138834

Glutamate-mediated excitotoxicity in schizophrenia: A review

PubMed Central

Plitman, Eric; Nakajima, Shinichiro; de la Fuente-Sandoval, Camilo; Gerretsen, Philip; Chakravarty, M. Mallar; Kobylianskii, Jane; Chung, Jun Ku; Caravaggio, Fernando; Iwata, Yusuke; Remington, Gary; Graff-Guerrero, Ariel

2015-01-01

Findings from neuroimaging studies in patients with schizophrenia suggest widespread structural changes although the mechanisms through which these changes occur are currently unknown. Glutamatergic activity appears to be increased in the early phases of schizophrenia and may contribute to these structural alterations through an excitotoxic effect. The primary aim of this review was to describe the possible role of glutamate-mediated excitotoxicity in explaining the presence of neuroanatomical changes within schizophrenia. A Medline® literature search was conducted, identifying English language studies on the topic of glutamate-mediated excitotoxicity in schizophrenia, using the terms “schizophreni*” and “glutam*” and ((“MRS” or “MRI” or “magnetic resonance”) or (“computed tomography” or “CT”)). Studies concomitantly investigating glutamatergic activity and brain structure in patients with schizophrenia were included. Results are discussed in the context of findings from preclinical studies. Seven studies were identified that met the inclusion criteria. These studies provide inconclusive support for the role of glutamate-mediated excitotoxicity in the occurrence of structural changes within schizophrenia, with the caveat that there is a paucity of human studies investigating this topic. Preclinical data suggest that an excitotoxic effect may occur as a result of a paradoxical increase in glutamatergic activity following N-methyl-D-aspartate receptor hypofunction. Based on animal literature, glutamate-mediated excitotoxicity may account for certain structural changes present in schizophrenia, but additional human studies are required to substantiate these findings. Future studies should adopt a longitudinal design and employ magnetic resonance imaging techniques to investigate whether an association between glutamatergic activity and structural changes exists in patients with schizophrenia. PMID:25159198

Structural changes concurrent with ferromagnetic transition

NASA Astrophysics Data System (ADS)

Yang, Sen; Bao, Hui-Xin; Zhou, Chao; Wang, Yu; Ren, Xiao-Bing; Song, Xiao-Ping; Yoshitaka, Matsushita; Yoshio, Katsuya; Masahiko, Tanaka; Keisuke, Kobayashi

2013-04-01

Ferromagnetic transition has generally been considered to involve only an ordering of magnetic moment with no change in the host crystal structure or symmetry, as evidenced by a wealth of crystal structure data from conventional X-ray diffractometry (XRD). However, the existence of magnetostriction in all known ferromagnetic systems indicates that the magnetic moment is coupled to the crystal lattice; hence there is a possibility that magnetic ordering may cause a change in crystal structure. With the development of high-resolution synchrotron XRD, more and more magnetic transitions have been found to be accompanied by simultaneous structural changes. In this article, we review our recent progress in understanding the structural change at a ferromagnetic transition, including synchrotron XRD evidence of structural changes at the ferromagnetic transition, a phenomenological theory of crystal structure changes accompanying ferromagnetic transitions, new insight into magnetic morphotropic phase boundaries (MPB) and so on. Two intriguing implications of non-centric symmetry in the ferromagnetic phase and the first-order nature of ferromagnetic transition are also discussed here. In short, this review is intended to give a self-consistent and logical account of structural change occurring simultaneously with a ferromagnetic transition, which may provide new insight for developing highly magneto-responsive materials.

Thermal changes of the environment and their influence on reinforced concrete structures

NASA Astrophysics Data System (ADS)

Fojtik, R.; Cajka, R.

2018-04-01

The thermal expansion of concrete elements concerns both monolithic and prefabricated structures. Inappropriate design of dilation segments may cause minor but even larger failures. Critical environment factors are temperature-changing operations, such as unheated underground garages, where temperature fluctuations may occur depending on the exterior conditions. This paper numerically and experimentally analyses the thermal deformation of selected girders in the underground garages and the consequent structure failures, their causes, possible prevention and appropriate remediation.

Mitigating Anthropocene influences in forests in the United States

Treesearch

Chadwick Dearing Oliver

2014-01-01

Anthropogenic and other climate changes, land use changes, forest structure changes, and introduced organisms are difficult to isolate with respect to their cumulative consequences. Similar changes have occurred before with undesirable effects and the currently high human population could suffer greatly if they happen again. Active forest management can help avoid...

Eight guidelines for developing a strategy for the '90s.

PubMed

Kaufman, N

1994-03-20

Regardless of the outcome of federal reform initiatives, health care is undergoing structural change of unprecedented magnitude. Structural change occurs when there is a fundamental, sustainable change in the values and purchasing behavior of buyers. During such times, market leaders are extremely vulnerable to competitive threats due to internal bureaucratic barriers. Witness the U.S. computer and automobile industries. As Robert Lutz, president of Chrysler, points out, "Being large doesn't mean being safe. The large won't eat the small. The swift will eat the slow." During this dynamic period in health care, it is critical that strategy be on target. Periods of structural change are filled with numerous threats as well as opportunities. The following are eight guidelines for developing health care strategy during the structural changes of the '90s.

14 CFR 183.55 - Limitations.

Code of Federal Regulations, 2010 CFR

2010-01-01

.... (a) If any change occurs that may affect an ODA Unit's qualifications or ability to perform a function (such as a change in the location of facilities, resources, personnel or the organizational structure), no Unit member may perform that function until the Administrator is notified of the change, and...

Thermal decomposition of ammonium hexachloroosmate.

PubMed

Asanova, T I; Kantor, I; Asanov, I P; Korenev, S V; Yusenko, K V

2016-12-07

Structural changes of (NH 4 ) 2 [OsCl 6 ] occurring during thermal decomposition in a reduction atmosphere have been studied in situ using combined energy-dispersive X-ray absorption spectroscopy (ED-XAFS) and powder X-ray diffraction (PXRD). According to PXRD, (NH 4 ) 2 [OsCl 6 ] transforms directly to metallic Os without the formation of any crystalline intermediates but through a plateau where no reactions occur. XANES and EXAFS data by means of Multivariate Curve Resolution (MCR) analysis show that thermal decomposition occurs with the formation of an amorphous intermediate {OsCl 4 } x with a possible polymeric structure. Being revealed for the first time the intermediate was subjected to determine the local atomic structure around osmium. The thermal decomposition of hexachloroosmate is much more complex and occurs within a minimum two-step process, which has never been observed before.

Erythritol: crystal growth from the melt.

PubMed

Lopes Jesus, A J; Nunes, Sandra C C; Ramos Silva, M; Matos Beja, A; Redinha, J S

2010-03-30

The structural changes occurring on erythritol as it is cooled from the melt to low temperature, and then heated up to the melting point have been investigated by differential scanning calorimetry (DSC), polarized light thermal microscopy (PLTM), X-ray powder diffraction (PXRD) and Fourier transform infrared spectroscopy (FTIR). By DSC, it was possible to set up the conditions to obtain an amorphous solid, a crystalline solid, or a mixture of both materials in different proportions. Two crystalline forms have been identified: a stable and a metastable one with melting points of 117 and 104 degrees C, respectively. The fusion curve decomposition of the stable form revealed the existence of three conformational structures. The main paths of the crystallization from the melt were followed by PLTM. The texture and colour changes allowed the characterization of the different phases and transitions in which they are involved on cooling as well as on heating processes. The type of crystallization front and its velocity were also followed by microscopic observation. These observations, together with the data provided by PXRD, allowed elucidating the transition of the metastable form into the stable one. The structural changes occurring upon the cooling and subsequent heating processes, namely those arising from intermolecular hydrogen bonds, were also accompanied by infrared spectroscopy. Particular attention was given to the spectral changes occurring in the OH stretching region. Copyright (c) 2009 Elsevier B.V. All rights reserved.

A symmetry measure for damage detection with mode shapes

NASA Astrophysics Data System (ADS)

Chen, Justin G.; Büyüköztürk, Oral

2017-11-01

This paper introduces a feature for detecting damage or changes in structures, the continuous symmetry measure, which can quantify the amount of a particular rotational, mirror, or translational symmetry in a mode shape of a structure. Many structures in the built environment have geometries that are either symmetric or almost symmetric, however damage typically occurs in a local manner causing asymmetric changes in the structure's geometry or material properties, and alters its mode shapes. The continuous symmetry measure can quantify these changes in symmetry as a novel indicator of damage for data-based structural health monitoring approaches. This paper describes the concept as a basis for detecting changes in mode shapes and detecting structural damage. Application of the method is demonstrated in various structures with different symmetrical properties: a pipe cross-section with a finite element model and experimental study, the NASA 8-bay truss model, and the simulated IASC-ASCE structural health monitoring benchmark structure. The applicability and limitations of the feature in applying it to structures of varying geometries is discussed.

State-Level Reforms That Support College-Level Program Changes in North Carolina

ERIC Educational Resources Information Center

Bowling, R. Edward; Morrissey, Sharon; Fouts, George M.

2014-01-01

This chapter describes the concurrent reforms occurring in North Carolina--both campus-level changes focused on such issues as developing structured programs of study and state-level reforms aimed at supporting the campus efforts.

Climate change and forest disturbances

Treesearch

Virginia H. Dale; Linda A. Joyce; Steve McNulty; Ronald P. Neilson; Matthew P. Ayres; Michael D. Flannigan; Paul J. Hanson; Lloyd C. Irland; Ariel E. Lugo; Chris J. Peterson; Daniel Simberloff; Frederick J. Swanson; Brian J. Stocks; Michael Wotton

2001-01-01

This article examines how eight disturbances influence forest structure, composition, and function, and how climate change may influence the severity, frequency, and magnitude of disturbances to forests. We focus on examples from the United States, although these influences occur worldwide. We also consider options for coping with disturbance under changing climate....

Adsorption of fibrinogen on a biomedical-grade stainless steel 316LVM surface: a PM-IRRAS study of the adsorption thermodynamics, kinetics and secondary structure changes.

PubMed

Desroches, Marie-Josee; Omanovic, Sasha

2008-05-14

Polarization-modulation infrared reflection-absorption spectroscopy (PM-IRRAS) was employed to investigate the interaction of serum protein fibrinogen with a biomedical-grade 316LVM stainless steel surface, in terms of the adsorption thermodynamics, kinetics and secondary structure changes of the protein. Apparent Gibbs energy of adsorption values indicated a highly spontaneous and strong adsorption of fibrinogen onto the surface. The kinetics of fibrinogen adsorption were successfully modeled using a pseudo first-order kinetic model. Deconvolution of the amide I bands indicated that the adsorption of fibrinogen on 316LVM results in significant changes in the protein's secondary structure that occur predominantly within the first minute of adsorption. Among the investigated structures, the alpha-helix structure undergoes the smallest changes, while the beta-sheet and beta-turns structures undergo significant changes. It was shown that lateral interactions between the adsorbed molecules do not play a role in controlling the secondary structure changes. An increase in temperature induced changes in the secondary structure of the protein, characterized by a loss of the alpha-helical content and its transformation into the beta-turns structure.

Metacarpal geometry changes during Thoroughbred race training are compatible with sagittal-plane cantilever bending.

PubMed

Merritt, J S; Davies, H M S

2010-11-01

Bending of the equine metacarpal bones during locomotion is poorly understood. Cantilever bending, in particular, may influence the loading of the metacarpal bones and surrounding structures in unique ways. We hypothesised that increased amounts of sagittal-plane cantilever bending may govern changes to the shape of the metacarpal bones of Thoroughbred racehorses during training. We hypothesised that this type of bending would require a linear change to occur in the combined second moment of area of the bones for sagittal-plane bending (I) during race training. Six Thoroughbred racehorses were used, who had all completed at least 4 years of race training at a commercial stable. The approximate change in I that had occurred during race training was computed from radiographic measurements at the start and end of training using a simple model of bone shape. A significant (P < 0.001), approximately linear pattern of change in I was observed in each horse, with the maximum change occurring proximally and the minimum change occurring distally. The pattern of change in I was compatible with the hypothesis that sagittal-plane cantilever bending governed changes to the shape of the metacarpal bones during race training. © 2010 EVJ Ltd.

Nucleotide-dependent bisANS binding to tubulin.

PubMed

Chakraborty, S; Sarkar, N; Bhattacharyya, B

1999-07-13

Non-covalent hydrophobic probes such as 5, 5'-bis(8-anilino-1-naphthalenesulfonate) (bisANS) have become increasingly popular to gain information about protein structure and conformation. However, there are limitations as bisANS binds non-specifically at multiple sites of many proteins. Successful use of this probe depends upon the development of binding conditions where only specific dye-protein interaction will occur. In this report, we have shown that the binding of bisANS to tubulin occurs instantaneously, specifically at one high affinity site when 1 mM guanosine 5'-triphosphate (GTP) is included in the reaction medium. Substantial portions of protein secondary structure and colchicine binding activity of tubulin are lost upon bisANS binding in absence of GTP. BisANS binding increases with time and occurs at multiple sites in the absence of GTP. Like GTP, other analogs, guanosine 5'-diphosphate, guanosine 5'-monophosphate and adenosine 5'-triphosphate, also displace bisANS from the lower affinity sites of tubulin. We believe that these multiple binding sites are generated due to the bisANS-induced structural changes on tubulin and the presence of GTP and other nucleotides protect those structural changes.

Cryogenic expansion joint for large superconducting magnet structures

DOEpatents

Brown, Robert L.

1978-01-01

An expansion joint is provided that accommodates dimensional changes occurring during the cooldown and warm-up of large cryogenic devices such as superconducting magnet coils. Flattened tubes containing a refrigerant such as gaseous nitrogen (N.sub.2) are inserted into expansion spaces in the structure. The gaseous N.sub.2 is circulated under pressure and aids in the cooldown process while providing its primary function of accommodating differential thermal contraction and expansion in the structure. After lower temperatures are reached and the greater part of the contraction has occured, the N.sub.2 liquefies then solidifies to provide a completely rigid structure at the cryogenic operating temperatures of the device.

Sleep loss and structural plasticity.

PubMed

Areal, Cassandra C; Warby, Simon C; Mongrain, Valérie

2017-06-01

Wakefulness and sleep are dynamic states during which brain functioning is modified and shaped. Sleep loss is detrimental to many brain functions and results in structural changes localized at synapses in the nervous system. In this review, we present and discuss some of the latest observations of structural changes following sleep loss in some vertebrates and insects. We also emphasize that these changes are region-specific and cell type-specific and that, most importantly, these structural modifications have functional roles in sleep regulation and brain functions. Selected mechanisms driving structural modifications occurring with sleep loss are also discussed. Overall, recent research highlights that extending wakefulness impacts synapse number and shape, which in turn regulate sleep need and sleep-dependent learning/memory. Copyright © 2017 Elsevier Ltd. All rights reserved.

Morphological and structural changes at the Merapi lava dome monitored using Unmanned Aerial Vehicles (UAVs)

NASA Astrophysics Data System (ADS)

Darmawan, H.; Walter, T. R.; Brotopuspito, K. S.; Subandriyo, S.; Nandaka, M. A.

2017-12-01

Six gas-driven explosions between 2012 and 2014 had changed the morphology and structures of the Merapi lava dome. The explosions mostly occurred during rainfall season and caused NW-SE elongated open fissures that dissected the lava dome. In this study, we conducted UAVs photogrammetry before and after the explosions to investigate the morphological and structural changes and to assess the quality of the UAV photogrammetry. The first UAV photogrammetry was conducted on 26 April 2012. After the explosions, we conducted Terrestrial Laser Scanning (TLS) survey on 18 September 2014 and repeated UAV photogrammetry on 6 October 2015. We applied Structure from Motion (SfM) algorithm to reconstruct 3D SfM point clouds and photomosaics of the 2012 and 2015 UAVs images. Topography changes has been analyzed by calculating height difference between the 2012 and 2015 SfM point clouds, while structural changes has been investigated by visual comparison between the 2012 and 2015 photo mosaics. Moreover, a quality assessment of the results of UAV photogrammetry has been done by comparing the 3D SfM point clouds to TLS dataset. Result shows that the 2012 and 2015 SfM point clouds have 0.19 and 0.57 m difference compared to the TLS point cloud. Furthermore, topography, and structural changes reveal that the 2012-14 explosions were controlled by pre-existing structures. The volume of the 2012-14 explosions is 26.400 ± 1320 m3 DRE. In addition, we find a structurally delineated unstable block at the southern front of the dome which potentially collapses in the future. We concluded that the 2012-14 explosions occurred due to interaction between magma intrusion and rain water and were facilitated by pre-existing structures. The unstable block potentially leads to a rock avalanche hazard. Furthermore, our drone photogrammetry results show very promising and therefore we recommend to use drone for topography mapping in lava dome building volcanoes.

Purpose and Structure: Learner-Centered Reform in a Multi-Functional System.

ERIC Educational Resources Information Center

Berry, Paul; Francis, John Bruce

This paper describes a conceptual framework that can order the host of changes occuring in institutional structure as a consequence of recent learner-centered reform in postsecondary education. Several schemata are examined, and a functional systematization of structures suggested; however, none of these purports to be a completely satisfactory…

Changes in composition, ecology and structure of high-mountain vegetation: a re-visitation study over 42 years.

PubMed

Evangelista, Alberto; Frate, Ludovico; Carranza, Maria Laura; Attorre, Fabio; Pelino, Giovanni; Stanisci, Angela

2016-01-27

High-mountain ecosystems are increasingly threatened by climate change, causing biodiversity loss, habitat degradation and landscape modifications. However, very few detailed studies have focussed on plant biodiversity in the high mountains of the Mediterranean. In this study, we investigated the long-term changes that have occurred in the composition, structure and ecology of high-mountain vegetation in the central Apennines (Majella) over the last 42 years. We performed a re-visitation study, using historical and newly collected vegetation data to explore which ecological and structural features have been the most successful in coping with climatic changes. Vegetation changes were analysed by comparing geo-referenced phytosociological relevés collected in high-mountain habitats (dolines, gentle slopes and ridges) on the Majella massif in 1972 and in 2014. Composition analysis was performed by detrended correspondence analysis, followed by an analysis of similarities for statistical significance assessment and by similarity percentage procedure (SIMPER) for identifying which species indicate temporal changes. Changes in ecological and structural indicators were analysed by a permutational multivariate analysis of variance, followed by a post hoc comparison. Over the last 42 years, clear floristic changes and significant ecological and structural variations occurred. We observed a significant increase in the thermophilic and mesonitrophilic plant species and an increment in the frequencies of hemicryptophytes. This re-visitation study in the Apennines agrees with observations in other alpine ecosystems, providing new insights for a better understanding of the effects of global change on Mediterranean high-mountain biodiversity. The observed changes in floristic composition, the thermophilization process and the shift towards a more nutrient-demanding vegetation are likely attributable to the combined effect of higher temperatures and the increase in soil nutrients triggered by global change. The re-visitation approach adopted herein represents a powerful tool for studying climate-related changes in sensitive high-mountain habitats. Published by Oxford University Press on behalf of the Annals of Botany Company.

Microscopic structural change in a liquid Fe-C alloy of ~5 GPa

DOE PAGES

Shibazaki, Yuki; Kono, Yoshio; Fei, Yingwei

2015-07-04

The structure of a liquid Fe-3.5 wt% C alloy is examined for up to 7.2 GPa via multiangle energy-dispersive X-ray diffraction using a Paris-Edinburgh type large-volume press. X-ray diffraction data show clear changes in the pressure-dependent peak positions of structure factor and reduced pair distribution function at 5GPa. These results suggest that the liquid Fe-3.5wt%C alloys change structurally at approximately 5GPa. This finding serves as a microscopic explanation for the alloy’s previously observed density change at the same pressure. The pressure dependencies of the nearest and second neighbor distances of the liquid Fe-3.5 wt% C alloy are similar to thosemore » of liquid Fe which exhibits a structural change near the bcc-fcc-liquid triple point (5.2GPa and 1991 K). Here, similarities between Fe-3.5wt% C and Fe suggest that a density change also occurs in liquid Fe and that this structural change extends to other Fe-light element alloys.« less

Structure changes in steels and hard metal induced by nanosecond and femtosecond laser processing

NASA Astrophysics Data System (ADS)

Dumitru, Gabriel; Romano, Valerio; Weber, Heinz P.; Haefke, Henry; Gerbig, Yvonne; Sentis, Marc L.; Hermann, Joerg; Bruneau, Sebastien

2003-11-01

Investigations on the occurrence of structure and hardness changes (for two sorts of steel and for a hard metal substrate) in the immediate vicinity of laser induced craters are presented in this work. Experiments with femtosecond pulses were performed in air with a Ti:sapphire laser (800 nm, 100 fs) at mean fluences of 2, 5 and 10 J/cm2. Series of microcraters were induced with 100 to 5,000 laser pulses per hole. Experiments with similar fluences, but 10 to 40 pules per hole, were performed on the same materials using a Nd:YAG delivering 100 ns pulese. After laser irradiation, cuts were made through the processed samples and the changes occurred in the crystalline structure of the target materials were evidenced by metallographical analysis of the resulting cross-sections. Hardness measurements were performed in points situated in the immediate vicinity of the laser-induced pores. Affected zones in the material surrounding laser induced pores were always found in the ns-regime, however with different properties for various laser parameters. In the fs-regime, zones of modified materials were also found and in such zones a significant hardness increasing was evidenced; the limit of the low fluences regime, where no structure changes occurred, was found to be slightly above 2 J/cm2.

Structural changes in the oxygen-evolving complex of photosystem II induced by the S 1 to S 2 transition: A combined XRD and QM/MM study

DOE PAGES

Askerka, Mikhail; Wang, Jimin; Brudvig, Gary W.; ...

2014-10-27

The S 1 → S 2 transition of the oxygen-evolving complex (OEC) of photosystem II does not involve the transfer of a proton to the lumen and occurs at cryogenic temperatures. Therefore, it is commonly thought to involve only Mn oxidation without any significant change in the structure of the OEC. Here, we analyze structural changes upon the S 1 → S 2 transition, as revealed by quantum mechanics/molecular mechanics methods and the isomorphous difference Fourier method applied to serial femtosecond X-ray diffraction data. Lastly, we find that the main structural change in the OEC is in the position ofmore » the dangling Mn and its coordination environment.« less

[Structure of crambin in solution, crystal and in the trajectories of molecular dynamics simulations].

PubMed

Abaturov, L V; Nosova, N G

2013-01-01

The mechanisms of the three-dimensional crambin structure alterations in the crystalline environments and in the trajectories of the molecular dynamics simulations in the vacuum and crystal surroundings have been analyzed. In the crystalline state and in the solution the partial regrouping of remote intramolecular packing contacts, involved in the formation and stabilization of the tertiary structure of the crambin molecule, occurs in NMR structures. In the crystalline state it is initiated by the formation of the intermolecular contacts, the conformational influence of its appearance is distributed over the structure. The changes of the conformations and positions of the residues of the loop segments, where the intermolecular contacts of the crystal surroundings are preferably concentrated, are most observable. Under the influence of these contacts the principal change of the regular secondary structure of crambin is taking place: extension of the two-strand beta structure to the three-strand structure with the participation of the single last residue N46 of the C-terminal loop. In comparison with the C-terminal loop the more profound changes are observed in the conformation and the atomic positions of the backbone atoms and in the solvent accessibility of the residues of the interhelical loop. In the solution of the ensemble of the 8 NMR structures relative accessibility to the solvent differs more noticeably also in the region of the loop segments and rather markedly in the interhelical loop. In the crambin cryogenic crystal structures the positions of the atoms of the backbone and/or side chain of 14-18 of 46 residues are discretely disordered. The disorganizations of at least 8 of 14 residues occur directly in the regions of the intermolecular contacts and another 5 residues are disordered indirectly through the intramolecular contacts with the residues of the intermolecular contacts. Upon the molecular dynamics simulation in the vacuum surrounding as in the solution of the crystalline structure of crambin the essential changes of the backbone conformation are caused by the intermolecular contacts absence, but partly masked by the structure changes owing to the nonpolar H atoms absence on the simulated structure. The intermolecular contact absence is partly manifested upon the molecular dynamics simulation of the crambin crystal with one protein molecule. Compared to the crystal structure the lengths of the interpeptide hydrogen bonds and other interresidue contacts in an average solution NMR structure are somewhat shorter and accordingly the energy of the interpeptide hydrogen bonds is better. This length shortening can occur at the stage of the refinement of the NMR structures of the crambin and other proteins by its energy minimizations in the vacuum surroundings and not exist in the solution protein structures.

Theory of multinonlinear media and its application to the soliton processes in ferrite–ferroelectric structures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cherkasskii, M. A., E-mail: macherkasskii@hotmail.com; Nikitin, A. A.; Kalinikos, B. A.

A theory is developed to describe the wave processes that occur in waveguide media having several types of nonlinearity, specifically, multinonlinear media. It is shown that the nonlinear Schrödinger equation can be used to describe the general wave process that occurs in such media. The competition between the electric wave nonlinearity and the magnetic wave nonlinearity in a layered multinonlinear ferrite–ferroelectric structure is found to change a total repulsive nonlinearity into a total attractive nonlinearity.

Reversible thermosalience of 4-aminobenzonitrile.

PubMed

Alimi, Lukman O; van Heerden, Dewald P; Lama, Prem; Smith, Vincent J; Barbour, Leonard J

2018-05-31

Crystals of 4-aminobenzonitrile grown by sublimation undergo reversible thermosalient phase changes during cooling and subsequent heating. Single-crystal diffraction studies have been carried out at 20 K intervals during cooling from 300 to 100 K in order to explain the structural change that occurs.

Launching Confident Numerate Learners

ERIC Educational Resources Information Center

Wade, Peter; Gervasoni, Ann; McQuade, Catharine; Smith, Catherine

2013-01-01

This paper explores how a secondary school in western Sydney used educational research as an impetus to change its mathematical education culture over a three year period. Key changes occurred in four areas: leadership; pedagogy; structures for teaching and learning; and mathematical environments. These included increased professional…

Analysis of Horizontal Integration within the Program Executive Office, Integrated Warfare Systems

DTIC Science & Technology

2006-09-01

intervention approach is likely to be effective at changing social relationships and behaviors. Change occurs at the basis of qualitative social time...four types of planned change interventions deal with organizational structures, processes, beliefs, and social relationships . Kotter’s change stages...effective at changing social relationships which favors the long-term. Since the commanding intervention does not deal with the social aspect

Effect of ion-beam treatment on structure and fracture resistance of 12Cr1MoV steel under static, cyclic and dynamic loading

DOE Office of Scientific and Technical Information (OSTI.GOV)

Panin, S. V., E-mail: svp@ispms.tsc.ru; Vlasov, I. V., E-mail: good0@yandex.ru; Sergeev, V. P., E-mail: retc@ispms.tsc.ru

2015-10-27

Features of the structure and properties modification of 12Cr1MoV steel subjected to irradiation by zirconium ion beam have been investigated with the use of optical and electron microscopy as well as microhardness measurement. It has been shown that upon treatment the structure modification occurred across the entire cross-section of specimens with the thickness of 1 mm. Changes in the mechanical properties of these specimens under static, cyclic and impact loading are interpreted in terms of identified structure changes.

Oxidation-induced Structural Changes of Ceruloplasmin Foster NGR Motif Deamidation That Promotes Integrin Binding and Signaling

PubMed Central

Barbariga, Marco; Curnis, Flavio; Spitaleri, Andrea; Andolfo, Annapaola; Zucchelli, Chiara; Lazzaro, Massimo; Magnani, Giuseppe; Musco, Giovanna; Corti, Angelo; Alessio, Massimo

2014-01-01

Asparagine deamidation occurs spontaneously in proteins during aging; deamidation of Asn-Gly-Arg (NGR) sites can lead to the formation of isoAsp-Gly-Arg (isoDGR), a motif that can recognize the RGD-binding site of integrins. Ceruloplasmin (Cp), a ferroxidase present in the cerebrospinal fluid (CSF), contains two NGR sites in its sequence: one exposed on the protein surface (568NGR) and the other buried in the tertiary structure (962NGR). Considering that Cp can undergo oxidative modifications in the CSF of neurodegenerative diseases, we investigated the effect of oxidation on the deamidation of both NGR motifs and, consequently, on the acquisition of integrin binding properties. We observed that the exposed 568NGR site can deamidate under conditions mimicking accelerated Asn aging. In contrast, the hidden 962NGR site can deamidate exclusively when aging occurs under oxidative conditions, suggesting that oxidation-induced structural changes foster deamidation at this site. NGR deamidation in Cp was associated with gain of integrin-binding function, intracellular signaling, and cell pro-adhesive activity. Finally, Cp aging in the CSF from Alzheimer disease patients, but not in control CSF, causes Cp deamidation with gain of integrin-binding function, suggesting that this transition might also occur in pathological conditions. In conclusion, both Cp NGR sites can deamidate during aging under oxidative conditions, likely as a consequence of oxidative-induced structural changes, thereby promoting a gain of function in integrin binding, signaling, and cell adhesion. PMID:24366863

Kinetics and fracture resistance of lithiated silicon nanostructure pairs controlled by their mechanical interaction

DOE PAGES

Lee, Seok Woo; Lee, Hyun -Wook; Ryu, Ill; ...

2015-06-26

Following an explosion of studies of silicon as a negative electrode for Li-ion batteries, the anomalous volumetric changes and fracture of lithiated single Si particles have attracted significant attention in various fields, including mechanics. However, in real batteries, lithiation occurs simultaneously in clusters of Si in a confined medium. Hence, understanding how the individual Si structures interact during lithiation in a closed space is necessary. Here, we demonstrate physical and mechanical interactions of swelling Si structures during lithiation using well-defined Si nanopillar pairs. Ex situ SEM and in situ TEM studies reveal that compressive stresses change the reaction kinetics somore » that preferential lithiation occurs at free surfaces when the pillars are mechanically clamped. Such mechanical interactions enhance the fracture resistance of lithiated Si by lessening the tensile stress concentrations in Si structures. Lastly, this study will contribute to improved design of Si structures at the electrode level for high-performance Li-ion batteries.« less

Second harmonic generation imaging as a potential tool for staging pregnancy and predicting preterm birth

NASA Astrophysics Data System (ADS)

Akins, Meredith L.; Luby-Phelps, Katherine; Mahendroo, Mala

2010-03-01

We use second harmonic generation (SHG) microscopy to assess changes in collagen structure of murine cervix during cervical remodeling of normal pregnancy and in a preterm birth model. Visual inspection of SHG images revealed substantial changes in collagen morphology throughout normal gestation. SHG images collected in both the forward and backward directions were analyzed quantitatively for changes in overall mean intensity, forward to backward intensity ratio, collagen fiber size, and porosity. Changes in mean SHG intensity and intensity ratio take place in early pregnancy, suggesting that submicroscopic changes in collagen fibril size and arrangement occur before macroscopic changes become evident. Fiber size progressively increased from early to late pregnancy, while pores between collagen fibers became larger and farther apart. Analysis of collagen features in premature cervical remodeling show that changes in collagen structure are dissimilar from normal remodeling. The ability to quantify multiple morphological features of collagen that characterize normal cervical remodeling and distinguish abnormal remodeling in preterm birth models supports future studies aimed at development of SHG endoscopic devices for clinical assessment of collagen changes during pregnancy in women and for predicting risk of preterm labor which occurs in 12.5% of all pregnancies.

26 CFR 1.48-10 - Single purpose agricultural or horticultural structures.

Code of Federal Regulations, 2014 CFR

2014-04-01

... test if either of the requirements of paragraph (e)(1)(i) of this section is not met. Thus, for example... the structure to fail the exclusive use test when the change occurs. Thus, for example, a hog-raising... example). Finally, the structure fails the incidental use test of paragraph (e) of this section because...

26 CFR 1.48-10 - Single purpose agricultural or horticultural structures.

Code of Federal Regulations, 2013 CFR

2013-04-01

... test if either of the requirements of paragraph (e)(1)(i) of this section is not met. Thus, for example... the structure to fail the exclusive use test when the change occurs. Thus, for example, a hog-raising... example). Finally, the structure fails the incidental use test of paragraph (e) of this section because...

Quantum chemical determination of Young's modulus of lignin. Calculations on a beta-O-4' model compound.

PubMed

Elder, Thomas

2007-11-01

The calculation of Young's modulus of lignin has been examined by subjecting a dimeric model compound to strain, coupled with the determination of energy and stress. The computational results, derived from quantum chemical calculations, are in agreement with available experimental results. Changes in geometry indicate that modifications in dihedral angles occur in response to linear strain. At larger levels of strain, bond rupture is evidenced by abrupt changes in energy, structure, and charge. Based on the current calculations, the bond scission may be occurring through a homolytic reaction between aliphatic carbon atoms. These results may have implications in the reactivity of lignin especially when subjected to processing methods that place large mechanical forces on the structure.

Effect of gamma irradiation on the structural, mechanical and optical properties of polytetrafluoroethylene sheet

NASA Astrophysics Data System (ADS)

Mohammadian-Kohol, M.; Asgari, M.; Shakur, H. R.

2018-04-01

In this study, the effects of gamma radiation on the chemical structure, mechanical and optical properties of polytetrafluoroethylene (PTFE) sheet were investigated with various doses up to 12 kGy. The chemical changes in the structure were studied by FTIR spectroscopy. Also, effects of radiation on the different mechanical parameters such as Young's modulus, toughness, strain, and stress were studied at the maximum tolerable force and the fracture points. Furthermore, changing the various optical parameters such as absorption coefficient, Urbach energy, optical band gaps, refractive index, optical dispersion parameters and plasma resonance frequency were studied by UV-visible spectroscopy. Formation of a band at 1594 cm-1, which was belonged to double carbon bonds, indicated that chain-scission was occurred at 12 kGy gamma irradiation dose. As well, the mechanical results showed an increase in the elastic behavior of PTFE sheets and a decrease in the plastic behavior of it with absorbed dose increasing. Moreover, the results showed that gamma irradiation can effectively change the various optical properties of PTFE sheets due to different phenomena such as degradation of the main chains, occurring chain-scission, formation of free radicals and cross-linking in the polymer structure.

Correlating structure and function during the evolution of fibrinogen-related domains

PubMed Central

Doolittle, Russell F; McNamara, Kyle; Lin, Kevin

2012-01-01

Fibrinogen-related domains (FReDs) are found in a variety of animal proteins with widely different functions, ranging from non-self recognition to clot formation. All appear to have a common surface where binding of one sort or other occurs. An examination of 19 completed animal genomes—including a sponge and sea anemone, six protostomes, and 11 deuterostomes—has allowed phylogenies to be constructed that show where various types of FReP (proteins containing FReDs) first made their appearance. Comparisons of sequences and structures also reveal particular features that correlate with function, including the influence of neighbor-domains. A particular set of insertions in the carboxyl-terminal subdomain was involved in the transition from structures known to bind sugars to those known to bind amino-terminal peptides. Perhaps not unexpectedly, FReDs with different functions have changed at different rates, with ficolins by far the fastest changing group. Significantly, the greatest amount of change in ficolin FReDs occurs in the third subdomain (“P domain”), the very opposite of the situation in most other vertebrate FReDs. The unbalanced style of change was also observed in FReDs from non-chordates, many of which have been implicated in innate immunity. PMID:23076991

Left atrial function in heart failure with impaired and preserved ejection fraction.

PubMed

Fang, Fang; Lee, Alex Pui-Wai; Yu, Cheuk-Man

2014-09-01

Left atrial structural and functional changes in heart failure are relatively ignored parts of cardiac assessment. This review illustrates the pathophysiological and functional changes in left atrium in heart failure as well as their prognostic value. Heart failure can be divided into those with systolic dysfunction and heart failure with preserved ejection fraction (HFPEF). Left atrial enlargement and dysfunction commonly occur in systolic heart failure, in particular, in idiopathic dilated cardiomyopathy. Atrial enlargement and dysfunction also carry important prognostic value in systolic heart failure, independently of known parameters such as left ventricular ejection fraction. In HFPEF, there is evidence of left atrial enlargement, impaired atrial compliance, and reduction of atrial pump function. This occurs not only at rest but also during exercise, indicating significant impairment of atrial contractile reserve. Furthermore, atrial dyssynchrony is common in HFPEF. These factors further contribute to the development of new onset or progression of atrial arrhythmias, in particular, atrial fibrillation. Left atrial function is an integral part of cardiac function and its structural and functional changes in heart failure are common. As changes of left atrial structure and function have different clinical implications in systolic heart failure and HFPEF, routine assessment is warranted.

Direct observation of fast protein conformational switching.

PubMed

Ishikawa, Haruto; Kwak, Kyungwon; Chung, Jean K; Kim, Seongheun; Fayer, Michael D

2008-06-24

Folded proteins can exist in multiple conformational substates. Each substate reflects a local minimum on the free-energy landscape with a distinct structure. By using ultrafast 2D-IR vibrational echo chemical-exchange spectroscopy, conformational switching between two well defined substates of a myoglobin mutant is observed on the approximately 50-ps time scale. The conformational dynamics are directly measured through the growth of cross peaks in the 2D-IR spectra of CO bound to the heme active site. The conformational switching involves motion of the distal histidine/E helix that changes the location of the imidazole side group of the histidine. The exchange between substates changes the frequency of the CO, which is detected by the time dependence of the 2D-IR vibrational echo spectrum. These results demonstrate that interconversion between protein conformational substates can occur on very fast time scales. The implications for larger structural changes that occur on much longer time scales are discussed.

Structural and functional changes in acute liver injury.

PubMed Central

Smuckler, E A

1976-01-01

Carbon tetrachloride produces liver cell injury in a variety of animal species. The first structurally recognizable changes occur in the endoplasmic reticulum, with alteration in ribosome-membrane interactions. Later there is an increase in intracellular fat, and the formation of tangled nets of the ergastoplasm. At no time are there changes in mitochondria or single membrane limited bodies in cells with intact plasmalemma, although a relative increase in cell sap may appear. In dead cells (those with plasmalemma discontinuties) crystalline deposits of calcium phosphatase may be noted. Functional changes are related to the endoplasmic reticulum and the plasma membrane. An early decrease in protein synthesis takes place; an accumulation of neutral lipid is related to this change. Later alterations in the ergastoplasmic functions (e.g., mixed function oxidation) occurs. Carbon tetrachloride is not the active agent; rather, a product of its metabolism, probably the CC1, free radical, is. The mechanisms of injury include macromolecular adduction and peroxide propagation. A third possibility includes a cascade effect with the production of secondary and tertiary products, also toxic in nature, with the ability to produce more widespread damage to intracellular structures. Images FIGURE 1. FIGURE 2. FIGURE 3. FIGURE 4. FIGURE 5. FIGURE 6. FIGURE 7. FIGURE 11. PMID:1001290

Comparative impact analysis of laser radiation on steel grades 1045 and 5140

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lobankova, Olga V., E-mail: lobankovaov@gmail.com, E-mail: zilyu@yandex.ru; Zykov, Ilya Y., E-mail: lobankovaov@gmail.com, E-mail: zilyu@yandex.ru; Melnikov, Alexander G., E-mail: melnikov-ag@tpu.ru

2014-11-14

There are results of experiments with deep engraving steel grades 1045 and 5140. The deep engraving was made by laser system equipped with a pulsed ytterbium fiber laser. The objectives of the work is to evaluate the change in the structure and properties of the material in the laser exposure area. Microsections of materials have been investigated and microhardness was measured for this purpose. The optimal parameters of laser material removal were considered. It is shown that various changes occur in the metal structure, which depends on the composition of the steel. In particular, when processing with identical laser parameters,more » tempered steel 1045 remelts and its hardness changes, while steel 5140 does not change its structure.« less

Time-Resolved Small-Angle X-ray Scattering Reveals Millisecond Transitions of a DNA Origami Switch.

PubMed

Bruetzel, Linda K; Walker, Philipp U; Gerling, Thomas; Dietz, Hendrik; Lipfert, Jan

2018-04-11

Self-assembled DNA structures enable creation of specific shapes at the nanometer-micrometer scale with molecular resolution. The construction of functional DNA assemblies will likely require dynamic structures that can undergo controllable conformational changes. DNA devices based on shape complementary stacking interactions have been demonstrated to undergo reversible conformational changes triggered by changes in ionic environment or temperature. An experimentally unexplored aspect is how quickly conformational transitions of large synthetic DNA origami structures can actually occur. Here, we use time-resolved small-angle X-ray scattering to monitor large-scale conformational transitions of a two-state DNA origami switch in free solution. We show that the DNA device switches from its open to its closed conformation upon addition of MgCl 2 in milliseconds, which is close to the theoretical diffusive speed limit. In contrast, measurements of the dimerization of DNA origami bricks reveal much slower and concentration-dependent assembly kinetics. DNA brick dimerization occurs on a time scale of minutes to hours suggesting that the kinetics depend on local concentration and molecular alignment.

Ultra-Small-Angle X-ray Scattering – X-ray Photon Correlation Spectroscopy Studies of Incipient Structural Changes in Amorphous Calcium Phosphate Based Dental Composites

PubMed Central

Zhang, F.; Allen, A.J.; Levine, L.E.; Espinal, L.; Antonucci, J.M.; Skrtic, D.; O’Donnell, J.N.R.; Ilavsky, J.

2012-01-01

The local structural changes in amorphous calcium phosphate (ACP) based dental composites were studied under isothermal conditions using both static, bulk measurement techniques and a recently developed methodology based on combined ultra-small angle X-ray scattering – X-ray photon correlation spectroscopy (USAXS-XPCS), which permits a dynamic approach. While results from conventional bulk measurements do not show clear signs of structural change, USAXS-XPCS results reveal unambiguous evidence for local structural variations on a similar time scale to that of water loss in the ACP fillers. A thermal-expansion based simulation indicates that thermal behavior alone does not account for the observed dynamics. Together, these results suggest that changes in the water content of ACP affect the composite morphology due to changes in ACP structure that occur without an amorphous-to-crystalline conversion. It is also noted that biomedical materials research could benefit greatly from USAXS-XPCS, a dynamic approach. PMID:22374649

Structural Changes of Lumbar Muscles in Non-specific Low Back Pain: A Systematic Review.

PubMed

Goubert, Dorien; Oosterwijck, Jessica Van; Meeus, Mira; Danneels, Lieven

2016-01-01

Lumbar muscle dysfunction due to pain might be related to altered lumbar muscle structure. Macroscopically, muscle degeneration in low back pain (LBP) is characterized by a decrease in cross-sectional area and an increase in fat infiltration in the lumbar paraspinal muscles. In addition microscopic changes, such as changes in fiber distribution, might occur. Inconsistencies in results from different studies make it difficult to draw firm conclusions on which structural changes are present in the different types of non-specific LBP. Insights regarding structural muscle alterations in LBP are, however, important for prevention and treatment of non-specific LBP. The goal of this article is to review which macro- and/or microscopic structural alterations of the lumbar muscles occur in case of non-specific chronic low back pain (CLBP), recurrent low back pain (RLBP), and acute low back pain (ALBP). Systematic review. All selected studies were case-control studies. A systematic literature search was conducted in the databases PubMed and Web of Science. Only full texts of original studies regarding structural alterations (atrophy, fat infiltration, and fiber type distribution) in lumbar muscles of patients with non-specific LBP compared to healthy controls were included. All included articles were scored on methodological quality. Fifteen studies were found eligible after screening title, abstract, and full text for inclusion and exclusion criteria. In CLBP, moderate evidence of atrophy was found in the multifidus; whereas, results in the paraspinal and the erector spinae muscle remain inconclusive. Also moderate evidence occurred in RLBP and ALBP, where no atrophy was shown in any lumbar muscle. Conflicting results were seen in undefined LBP groups. Results concerning fat infiltration were inconsistent in CLBP. On the other hand, there is moderate evidence in RLBP that fat infiltration does not occur, although a larger muscle fat index was found in the erector spinae, multifidus, and paraspinal muscles, reflecting an increased relative amount of intramuscular lipids in RLBP. However, no studies were found investigating fat infiltration in ALBP. Restricted evidence indicates no abnormalities in fiber type in the paraspinal muscles in CLBP. No studies have examined fiber type in ALBP and RLBP. Lack of clarity concerning patient definitions, exact LBP symptoms, and applied methods. The results indicate atrophy in CLBP in the multifidus and paraspinal muscles but not in the erector spinae. No atrophy was shown in RLBP and ALBP. Fat infiltration did not occur in RLBP, but results in CLBP were inconsistent. No abnormalities in fiber type in the paraspinal muscles were found in CLBP. Low back pain, non-specific, chronic, recurrent, acute, muscle structure, fat infiltration, cross-sectional area, fiber type, review.

A Quantitative Measure of Conformational Changes in Apo, Holo and Ligand-Bound Forms of Enzymes.

PubMed

Singh, Satendra; Singh, Atul Kumar; Wadhwa, Gulshan; Singh, Dev Bukhsh; Dwivedi, Seema; Gautam, Budhayash; Ramteke, Pramod W

2016-06-01

Determination of the native geometry of the enzymes and ligand complexes is a key step in the process of structure-based drug designing. Enzymes and ligands show flexibility in structural behavior as they come in contact with each other. When ligand binds with active site of the enzyme, in the presence of cofactor some structural changes are expected to occur in the active site. Motivation behind this study is to determine the nature of conformational changes as well as regions where such changes are more pronounced. To measure the structural changes due to cofactor and ligand complex, enzyme in apo, holo and ligand-bound forms is selected. Enzyme data set was retrieved from protein data bank. Fifteen triplet groups were selected for the analysis of structural changes based on selection criteria. Structural features for selected enzymes were compared at the global as well as local region. Accessible surface area for the enzymes in entire triplet set was calculated, which describes the change in accessible surface area upon binding of cofactor and ligand with the enzyme. It was observed that some structural changes take place during binding of ligand in the presence of cofactor. This study will helps in understanding the level of flexibility in protein-ligand interaction for computer-aided drug designing.

A Current Appraisal of Adult Education Activity in Australia with a Focus on Community-Based Education and Work among Women and Aboriginal People.

ERIC Educational Resources Information Center

Randell, Shirley

As adult education in Australia becomes a priority, emphases have changed. Structure has also changed, as traditional providers of adult education have begun to adjust to changing political, economic, and social realities. Changes in community-based education have occurred as government involvement has provided more funds and begun to encroach on…

Age structure changes and extraordinary lifespan in wild medfly populations.

PubMed

Carey, James R; Papadopoulos, Nikos T; Müller, Hans-Georg; Katsoyannos, Byron I; Kouloussis, Nikos A; Wang, Jane-Ling; Wachter, Kenneth; Yu, Wei; Liedo, Pablo

2008-06-01

The main purpose of this study was to test the hypotheses that major changes in age structure occur in wild populations of the Mediterranean fruit fly (medfly) and that a substantial fraction of individuals survive to middle age and beyond (> 3-4 weeks). We thus brought reference life tables and deconvolution models to bear on medfly mortality data gathered from a 3-year study of field-captured individuals that were monitored in the laboratory. The average time-to-death of captured females differed between sampling dates by 23.9, 22.7, and 37.0 days in the 2003, 2004, and 2005 field seasons, respectively. These shifts in average times-to-death provided evidence of changes in population age structure. Estimates indicated that middle-aged medflies (> 30 days) were common in the population. A surprise in the study was the extraordinary longevity observed in field-captured medflies. For example, 19 captured females but no reference females survived in the laboratory for 140 days or more, and 6 captured but no reference males survived in the laboratory for 170 days or more. This paper advances the study of aging in the wild by introducing a new method for estimating age structure in insect populations, demonstrating that major changes in age structure occur in field populations of insects, showing that middle-aged individuals are common in the wild, and revealing the extraordinary lifespans of wild-caught individuals due to their early life experience in the field.

Articulatory Changes Following Treatment of Muscle Tension Dysphonia: Preliminary Acoustic Evidence

ERIC Educational Resources Information Center

Dromey, Christopher; Nissen, Shawn L.; Roy, Nelson; Merrill, Ray M.

2008-01-01

Purpose: Primary muscle tension dysphonia (MTD), a voice disturbance that occurs in the absence of structural or neurological pathology, may respond to manual circumlaryngeal techniques, which ostensibly alter the posture of the larynx and/or the configuration of the vocal folds without directly targeting supralaryngeal articulatory structures.…

Relaxed structure of typical nitro explosives in the excited state: Observation, implication and application

NASA Astrophysics Data System (ADS)

Chu, Genbai; Yang, Zuhua; Xi, Tao; Xin, Jianting; Zhao, Yongqiang; He, Weihua; Shui, Min; Gu, Yuqiu; Xiong, Ying; Xu, Tao

2018-04-01

Understanding the structural, geometrical, and chemical changes that occur after an electronic excitation is essential to elucidate the inherent mechanism of nitro explosives. Herein, relaxed structures of typical nitro explosives in the lowest singlet excited state are investigated using time-dependent density functional theory. During the excitation process, the nitro group is activated and relaxes via geometrical change. The five explosives RDX, HMX, CL-20, PETN, and LLM-105 exhibit similar relaxed structures, and the impact sensitivity is related to their excitation energy. High-sensitivity δ-HMX has a lower excitation energy for relaxed structure than β-HMX. This study offers novel insight into energetic materials.

Microgravity changes in heart structure and cyclic-AMP metabolism

NASA Technical Reports Server (NTRS)

Philpott, D. E.; Fine, A.; Kato, K.; Egnor, R.; Cheng, L.

1985-01-01

The effects of microgravity on cardiac ultrastructure and cyclic AMP metabolism in tissues of rats flown on Spacelab 3 are reported. Light and electron microscope studies of cell structure, measurements of low and high Km phosphodiesterase activity, cyclic AMP-dependent protein kinase activity, and regulatory subunit compartmentation show significant deviations in flight animals when compared to ground controls. The results indicate that some changes have occurred in cellular responses associated with catecholamine receptor interactions and intracellular signal processing.

Thermomechanical deformation in the presence of metallurgical changes

NASA Technical Reports Server (NTRS)

Robinson, D. N.

1985-01-01

Nonisothermal testing that can be used as a basis of a nonisothermal representation is discussed. Related tests regarding metallurgical changes that occur in other high temperature structural alloys are discussed. A viscoplastic constitutive model capable of qualitatively representing the behavioral features was formulated. This model is used to assess the differences in ultimate life prediction in some typical nonisothermal structural problems when the constitutive model does or does not account for metallurgically induced thermomechanical history dependence.

Transformations of dislocation martensite in tempering secondary-hardening steel

NASA Astrophysics Data System (ADS)

Gorynin, I. V.; Rybin, V. V.; Malyshevskii, V. A.; Semicheva, T. G.; Sherokhina, L. G.

1999-09-01

Analysis of the evolution of the fine structure of secondary-hardening steel in tempering makes it possible to understand the nature of processes that cause changes in the strength and ductility. They are connected with the changes that occur in the solid solution, the ensemble of disperse segregations of the carbide phase, and the dislocation structure of martensite. These transformations are interrelated, and their specific features are determined by the chemical composition of the steel.

Structural insight into the substrate- and dioxygen-binding manner in the catalytic cycle of rieske nonheme iron oxygenase system, carbazole 1,9a-dioxygenase.

PubMed

Ashikawa, Yuji; Fujimoto, Zui; Usami, Yusuke; Inoue, Kengo; Noguchi, Haruko; Yamane, Hisakazu; Nojiri, Hideaki

2012-06-24

Dihydroxylation of tandemly linked aromatic carbons in a cis-configuration, catalyzed by multicomponent oxygenase systems known as Rieske nonheme iron oxygenase systems (ROs), often constitute the initial step of aerobic degradation pathways for various aromatic compounds. Because such RO reactions inherently govern whether downstream degradation processes occur, novel oxygenation mechanisms involving oxygenase components of ROs (RO-Os) is of great interest. Despite substantial progress in structural and physicochemical analyses, no consensus exists on the chemical steps in the catalytic cycles of ROs. Thus, determining whether conformational changes at the active site of RO-O occur by substrate and/or oxygen binding is important. Carbazole 1,9a-dioxygenase (CARDO), a RO member consists of catalytic terminal oxygenase (CARDO-O), ferredoxin (CARDO-F), and ferredoxin reductase. We have succeeded in determining the crystal structures of oxidized CARDO-O, oxidized CARDO-F, and both oxidized and reduced forms of the CARDO-O: CARDO-F binary complex. In the present study, we determined the crystal structures of the reduced carbazole (CAR)-bound, dioxygen-bound, and both CAR- and dioxygen-bound CARDO-O: CARDO-F binary complex structures at 1.95, 1.85, and 2.00 Å resolution. These structures revealed the conformational changes that occur in the catalytic cycle. Structural comparison between complex structures in each step of the catalytic mechanism provides several implications, such as the order of substrate and dioxygen bindings, the iron-dioxygen species likely being Fe(III)-(hydro)peroxo, and the creation of room for dioxygen binding and the promotion of dioxygen binding in desirable fashion by preceding substrate binding. The RO catalytic mechanism is proposed as follows: When the Rieske cluster is reduced, substrate binding induces several conformational changes (e.g., movements of the nonheme iron and the ligand residue) that create room for oxygen binding. Dioxygen bound in a side-on fashion onto nonheme iron is activated by reduction to the peroxo state [Fe(III)-(hydro)peroxo]. This state may react directly with the bound substrate, or O-O bond cleavage may occur to generate Fe(V)-oxo-hydroxo species prior to the reaction. After producing a cis-dihydrodiol, the product is released by reducing the nonheme iron. This proposed scheme describes the catalytic cycle of ROs and provides important information for a better understanding of the mechanism.

Instability of plasmid DNA sequences: macro and micro evolution of the antibiotic resistance plasmid R6-5.

PubMed

Timmis, K N; Cabello, F; Andrés, I; Nordheim, A; Burkhardt, H J; Cohen, S N

1978-11-16

Detailed examination of the structure of cloned DNA fragments of the R6-5 antibiotic resistance plasmid has revealed a substantial degree of polynucleotide sequence heterogeneity and indicates that sequence rearrangements in plasmids and possible other replicons occur more frequently than has hitherto been appreciated. The sequences changes in cloned R6-5 fragments were shown in some instances to have occurred prior to cloning, i.e. existing in the original population of R6-5 molecules that was obtained from a single bacterial clone and by several different criteria judged to be homogeneous, and in others to have occurred either during the cloning procedure or during subsequent propagation of hybrid molecules. The molecular changes that are described involved insertion/deletion of the previously characterized IS2 insertion element, formation of a new inverted repeat structure probably by duplication of a preexisting R6-5 DNA sequence, sequence inversion, and loss and gain of restriction endonuclease cleavage sites.

Post-bleaching coral community change on southern Maldivian reefs: is there potential for rapid recovery?

NASA Astrophysics Data System (ADS)

Perry, C. T.; Morgan, K. M.

2017-12-01

Given the severity of the 2016 global bleaching event, there are major questions about how quickly reef communities will recover. Here, we explore the ecological and physical structural changes that occurred across five atoll interior reefs in the southern Maldives using data collected at 6 and 12 months post-bleaching. Following initial severe coral mortality, further minor coral mortality had occurred by 12 months post-bleaching, and coral cover is now low (<6%). In contrast, reef rugosity has continued to decline over time, and our observations suggest transitions to rubble-dominated states will occur in the near future. Juvenile coral densities in shallow fore-reef habitats are also exceptionally low (<6 individuals m-2), well below those measured 9-12 months following the 1998 bleaching event, and below recovery thresholds identified on other Indian Ocean reefs. Our findings suggest that the physical structure of these reefs will need to decline further before effective recruitment and recovery can begin.

Critical temperatures of 70%Pb(Mg1/3Nb2/3)O3-30%PbTiO3 thin films investigated by dielectric, ferroelectric, and structural measurements

NASA Astrophysics Data System (ADS)

Meng, X. J.; Rémiens, D.; Detalle, M.; Dkhil, B.; Sun, J. L.; Chu, J. H.

2007-03-01

The authors have investigated the temperature dependence of the ferroelectric, dielectric, and structural properties of 70%Pb(Mg1/3Nb2/3)O3-30%PbTiO3 thin films. Two critical temperatures were evidenced. The first one occurring around 410K corresponds to the bulk paraelectric-ferroelectric phase transition and the second one around 200K is rather related to a self-arrangement of small domains into macrodomains in order to minimize elastic energies. A multiscale domainlike structure is induced and the temperature evolution of such complex structure can be revealed through pronounced changes occurring in the nonlinear dielectric susceptibility.

Higher Education in Europe. Higher Education Policy Series 16.

ERIC Educational Resources Information Center

Gellert, Claudius, Ed.

This book addresses some of the major institutional and structural changes that have occurred in European universities and other tertiary institutions in recent years. It includes descriptive accounts of new developments in organizational patterns and discusses how new demands from the labor market and changing sociopolitical expectations have…

Capitalism, Identity Politics, and Queerness Converge: LGBT Employee Resource Groups

ERIC Educational Resources Information Center

Githens, Rod P.

2009-01-01

Lesbian, gay, bisexual, and transgender (LGBT) employee resource groups have brought about substantial organizational change within corporations. Capitalist structures have enabled these changes to occur more quickly in the private sector than within the public sector. In this article, I explore how capitalism has converged with two approaches of…

Resistance to Change: Overcoming Institutional and Individual Limitations for Improving Student Behavior through PLCs

ERIC Educational Resources Information Center

Maag, John W.

2009-01-01

Many public schools currently have organizational structures that form barriers for dealing more effectively with students' challenging behaviors even though positive school-wide approaches exist and provide empirical support for their use. Nevertheless, resistance to change occurs at both institutional and individual levels. Improving student…

Developing a field and cyberinfrastructure to study land-atmosphere interactions in the Chihuahuan Desert

USDA-ARS?s Scientific Manuscript database

Chihuahuan desert landscapes are representative of many arid and semiarid ecosystems of the world where dramatic changes in vegetation structure and ecosystem processes have occurred over the past several centuries. These changes in ecosystem state are often interpreted as “desertification”, the bro...

Age structure and development in ASEAN and Japan: 1950-2015; a preliminary report.

PubMed

Campbell, B O

1982-01-01

An attempt was made to show that significant shifts in age composition have occurred and will occur in the ASEAN countries and Japan. Based on the key ratio, the ratio of the entering labor force population, 15-29, to the established labor force population, 30-64, and on the education and dependency burdence, the evidence supports that such shifts have occurred and will occur. Another goal was to trace the potential impact of these age structure changes on the economy and society of the ASEAN countries and Japan, assuming a set of hypothetical relations between age structure changes, as measured by the key ratio and various demographic, economic, and social outcomes. This was done for Indonesia, and the Indonesian "case study" suggests that past and future changes in age strucute could have led and could lead to wide swings or long waves in per capita incomes or the growth rate in per capita incomes, the skill and possible captial intensity of production, household formation rates, emigration and immigration rates, fertility rates, and suicide rates, and other indicators of social instability. Interesting conclusions also emerged from the analysis of education and dependency burdens, especially the inverse relation between Japan's and ASEAN's burdens on both indices. The low educational and dependency burdens Japan enjoyed must have given Japan a distinct advantage in providing resources for infrastrucute, plant, and equipment, and so forth--an advantage that Japan will maintain (joined by Singapore) over the rest of this century. It is entirely possible that the relative economic performance of Japan versus the ASEAN countries or the ASEAN countries versus one another could not be fully explained or adequately forecasted without considering the impact of age structure and changes in age structure. It seems unlikely that the past or future performance of these countries individually can be adequately understood or forecasted without considering the long swing apparent in the key ratio and in the education and dependency burdens of each. For example, future fertility rates in several of the ASEAN countries and in Japan will differ from UN forecasts if they vary with the key ratio in the future as they have in the past. Even if this result is correct, ignoring age structure changes could lead to major forecasting and planning errors. A 1st step to encouraging research necessary to test the hypothetical relations on which these outcomes are based and to empirically determine the contribution of age structure would be to develop a more sophisticated theoretical framework than that used in this study and to carry out country by country investigations of the institutional and cultural constraints that influence the relations involved.

Wanting to Be Different Predicts Nonmotivated Change: Actual-Desired Self-Discrepancies and Susceptibility to Subtle Change Inductions.

PubMed

DeMarree, Kenneth G; Rios, Kimberly; Randell, J Adam; Wheeler, S Christian; Reich, Darcy A; Petty, Richard E

2016-12-01

Actual-desired discrepancies in people's self-concepts represent structural incongruities in their self-representations that can lead people to experience subjective conflict. Theory and research suggest that structural incongruities predict susceptibility to subtle influences like priming and conditioning. Although typically examined for their motivational properties, we hypothesized that because self-discrepancies represent structural incongruities in people's self-concepts, they should also predict susceptibility to subtle influences on people's active self-views. Across three studies, we found that subtle change inductions (self-evaluative conditioning and priming) exerted greater impact on active self-perceptions and behavior as actual-desired self-discrepancies increased in magnitude. Exploratory analyses suggested that these changes occurred regardless of the compatibility of the change induction with individuals' desired self-views. © 2016 by the Society for Personality and Social Psychology, Inc.

Structural changes during annealing of GaInAsN

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kurtz, Sarah; Webb, J.; Gedvilas, L.

2001-02-05

The alloy GaInAsN has great potential as a lower-band-gap material lattice matched to GaAs, but there is little understanding of what causes its poor optoelectronic properties and why these improve with annealing. This study provides information about the structural changes that occur when GaInAsN is annealed. The Fourier transform infrared spectra exhibit two primary features: a triplet at {approx}470 cm-1 (Ga--N stretch) and two or three bands at {approx}3100 cm-1 (N--H stretch). The change in the Ga--N stretch absorption can be explained if the nitrogen environment is converted from NGa{sub 4} to NInGa{sub 3} after annealing. The N--H stretch ismore » also changed after annealing, implying a second, and unrelated, structural change.« less

The Adaptation of Workers to Industrial Change. European Seminar (Toulouse, France, January 22-23, 1996). Summary of the Debates.

ERIC Educational Resources Information Center

Social Europe, 1996

1996-01-01

This document summarizes the debates that occurred at a European seminar on the adaptation of workers to industrial change. The document begins with the following three speeches: "The Challenges of Adapting Workers to Industrial Change" (Dominique Balmary); "Objective 4 of the Structural Funds: A Response to the Double Challenge of…

The response of terrestrial ecosystems to global climate change: Towards an integrated approach

Treesearch

Lindsey E. Rustad

2008-01-01

Accumulating evidence points to an anthropogenic 'fingerprint' on the global climate change that has occurred in the last century. Climate change has, and will continue to have, profound effects on the structure and function of terrestrial ecosystems. As such, there is a critical need to continue to develop a sound scientific basis for national and...

Effect of landslides on the structural characteristics of land-cover based on complex networks

NASA Astrophysics Data System (ADS)

He, Jing; Tang, Chuan; Liu, Gang; Li, Weile

2017-09-01

Landslides have been widely studied by geologists. However, previous studies mainly focused on the formation of landslides and never considered the effect of landslides on the structural characteristics of land-cover. Here we define the modeling of the graph topology for the land-cover, using the satellite images of the earth’s surface before and after the earthquake. We find that the land-cover network satisfies the power-law distribution, whether the land-cover contains landslides or not. However, landslides may change some parameters or measures of the structural characteristics of land-cover. The results show that the linear coefficient, modularity and area distribution are all changed after the occurence of landslides, which means the structural characteristics of the land-cover are changed.

In situ transmission electron microscopy of individual carbon nanotetrahedron/ribbon structures in bending

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kohno, Hideo, E-mail: kohno.hideo@kochi-tech.ac.jp; Masuda, Yusuke

2015-05-11

When the direction of flattening of a carbon nanotube changes during growth mediated by a metal nanoparticle, a carbon nanotetrahedron is formed in the middle of the carbon nanoribbon. We report the bending properties of the carbon nanotetrahedron/nanoribbon structure using a micro-manipulator system in a transmission electron microscope. In many cases, bending occurs at an edge of the carbon nanotetrahedron. No significant change is observed in the tetrahedron's shape during bending, and the bending is reversible and repeatable. Our results show that the carbon nanotetrahedron/nanoribbon structure has good durability against mechanical bending.

Time simulation of flutter with large stiffness changes

NASA Technical Reports Server (NTRS)

Karpel, M.; Wieseman, C. D.

1992-01-01

Time simulation of flutter, involving large local structural changes, is formulated with a state-space model that is based on a relatively small number of generalized coordinates. Free-free vibration modes are first calculated for a nominal finite-element model with relatively large fictitious masses located at the area of structural changes. A low-frequency subset of these modes is then transformed into a set of structural modal coordinates with which the entire simulation is performed. These generalized coordinates and the associated oscillatory aerodynamic force coefficient matrices are used to construct an efficient time-domain, state-space model for basic aeroelastic case. The time simulation can then be performed by simply changing the mass, stiffness and damping coupling terms when structural changes occur. It is shown that the size of the aeroelastic model required for time simulation with large structural changes at a few a priori known locations is similar to that required for direct analysis of a single structural case. The method is applied to the simulation of an aeroelastic wind-tunnel model. The diverging oscillations are followed by the activation of a tip-ballast decoupling mechanism that stabilizes the system but may cause significant transient overshoots.

Time simulation of flutter with large stiffness changes

NASA Technical Reports Server (NTRS)

Karpel, Mordechay; Wieseman, Carol D.

1992-01-01

Time simulation of flutter, involving large local structural changes, is formulated with a state-space model that is based on a relatively small number of generalized coordinates. Free-free vibration modes are first calculated for a nominal finite-element model with relatively large fictitious masses located at the area of structural changes. A low-frequency subset of these modes is then transformed into a set of structural modal coordinates with which the entire simulation is performed. These generalized coordinates and the associated oscillatory aerodynamic force coefficient matrices are used to construct an efficient time-domain, state-space model for a basic aeroelastic case. The time simulation can then be performed by simply changing the mass, stiffness, and damping coupling terms when structural changes occur. It is shown that the size of the aeroelastic model required for time simulation with large structural changes at a few apriori known locations is similar to that required for direct analysis of a single structural case. The method is applied to the simulation of an aeroelastic wind-tunnel model. The diverging oscillations are followed by the activation of a tip-ballast decoupling mechanism that stabilizes the system but may cause significant transient overshoots.

Climate change and oceanic barriers: genetic differentiation in Pomatomus saltatrix (Pisces: Pomatomidae) in the North Atlantic Ocean and the Mediterranean Sea.

PubMed

Pardiñas, A F; Campo, D; Pola, I G; Miralles, L; Juanes, F; Garcia-Vazquez, E

2010-11-01

Nucleotide variation of partial cytochrome b sequences was analysed in the bluefish Pomatomus saltatrix to investigate the population-structuring roles of climate change and oceanic barriers. Western and eastern North Atlantic Ocean populations appeared to be totally isolated, with the latter connected to the Mediterranean Sea within which further structuring occurred. © 2010 The Authors. Journal of Fish Biology © 2010 The Fisheries Society of the British Isles.

Structural changes and damage of single-crystal turbine blades during life tests of an aviation gas turbine engine

NASA Astrophysics Data System (ADS)

Ospennikova, O. G.; Orlov, M. R.; Kolodochkina, V. G.; Nazarkin, R. M.

2015-04-01

The irreversible structural changes of the single-crystal ZhS32-VI nickel superalloy blades of a high-pressure turbine that occur during life tests of a gas turbine engine are studied. The main operation damages in the hottest section of the blade airfoil are found to be the fracture of the heat-resistant coating in the leading edge and the formation of thermomechanical fatigue cracks. The possibility of reconditioning repair of the blades is considered.

Cognitive training-induced short-term functional and long-term structural plastic change is related to gains in global cognition in healthy older adults: a pilot study.

PubMed

Lampit, Amit; Hallock, Harry; Suo, Chao; Naismith, Sharon L; Valenzuela, Michael

2015-01-01

Computerized cognitive training (CCT) is a safe and inexpensive intervention to enhance cognitive performance in the elderly. However, the neural underpinning of CCT-induced effects and the timecourse by which such neural changes occur are unknown. Here, we report on results from a pilot study of healthy older adults who underwent three 1-h weekly sessions of either multidomain CCT program (n = 7) or an active control intervention (n = 5) over 12 weeks. Multimodal magnetic resonance imaging (MRI) scans and cognitive assessments were performed at baseline and after 9 and 36 h of training. Voxel-based structural analysis revealed a significant Group × Time interaction in the right post-central gyrus indicating increased gray matter density in the CCT group compared to active control at both follow-ups. Across the entire sample, there were significant positive correlations between changes in the post-central gyrus and change in global cognition after 36 h of training. A post-hoc vertex-based analysis found a significant between-group difference in rate of thickness change between baseline and post-training in the left fusiform gyrus, as well as a large cluster in the right parietal lobe covering the supramarginal and post-central gyri. Resting-state functional connectivity between the posterior cingulate and the superior frontal gyrus, and between the right hippocampus and the superior temporal gyrus significantly differed between the two groups after 9 h of training and correlated with cognitive change post-training. No significant interactions were found for any of the spectroscopy and diffusion tensor imaging data. Though preliminary, our results suggest that functional change may precede structural and cognitive change, and that about one-half of the structural change occurs within the first 9 h of training. Future studies are required to determine the role of these brain changes in the mechanisms underlying CCT-induced cognitive effects.

Structure and mechanism of a molecular rheostat, an RNA thermometer that modulates immune evasion by Neisseria meningitidis

PubMed Central

Barnwal, Ravi Pratap; Loh, Edmund; Godin, Katherine S.; Yip, Jordan; Lavender, Hayley; Tang, Christoph M.; Varani, Gabriele

2016-01-01

Neisseria meningitidis causes bacterial meningitis and septicemia. It evades the host complement system by upregulating expression of immune evasion factors in response to changes in temperature. RNA thermometers within mRNAs control expression of bacterial immune evasion factors, including CssA, in the 5′-untranslated region of the operon for capsule biosynthesis. We dissect the molecular mechanisms of thermoregulation and report the structure of the CssA thermometer. We show that the RNA thermometer acts as a rheostat, whose stability is optimized to respond in a small temperature range around 37°C as occur within the upper airways during infection. Small increases in temperature gradually open up the structure to allow progressively increased access to the ribosome binding site. Even small changes in stability induced by mutations of imperfect base pairs, as in naturally occurring polymorphisms, shift the thermometer response outside of the desired temperature range, suggesting that its activity could be modulated by pharmacological intervention. PMID:27369378

Function and structure in glycine receptors and some of their relatives.

PubMed

Colquhoun, David; Sivilotti, Lucia G

2004-06-01

In the field of ligand-gated ion channels, recent developments, both in the knowledge of structure and in the measurement of function at the single-channel level, have allowed a sensible start to be made on understanding the relationship between structure and function in these proteins. In this review, the cases of glycine, nicotinic ACh and glutamate receptors are compared and contrasted, and problems such as how binding of agonist causes the channel to open, and why partial agonists are partial, are considered. Some observations, both structural and functional, suggest that more attention needs to be paid to conformational changes that occur before the channel opens. Such changes might account for the interaction found between subunits of the glycine receptor while it is still shut and, perhaps, the agonist-dependent structural changes seen in AMPA receptors. They might also complicate our understanding of the binding-gating problem.

Forest resources of Pennsylvania

Treesearch

Richard H. Widmann; Richard H. Widmann

1995-01-01

Phis report presents an analysis of the results of the 1989 forest inventory of Pennsylvania as well as trends that habe occurred since the previous survey. Major topics include changes in forest land by ownership, forest type, and timberland component7 stand structure is charaterized by stand size, understory woody vegetation, dead trees, and changes in relative...

The effects of declining population growth on the demand for housing.

Treesearch

Thomas C. Marcin

1974-01-01

Declining population growth and unprecedented changes in the age structure of the population in the next several decades will profoundly affect housing demand in the next 50 years. A decline in housing demand and substantial change in the type of housing in demand are likely to occur by 1990.

Electron transfer and conformational change in complexes of trimethylamine dehydrogenase and electron transferring flavoprotein.

PubMed

Jones, Matthew; Talfournier, Francois; Bobrov, Anton; Grossmann, J Günter; Vekshin, Nikolai; Sutcliffe, Michael J; Scrutton, Nigel S

2002-03-08

The trimethylamine dehydrogenase-electron transferring flavoprotein (TMADH.ETF) electron transfer complex has been studied by fluorescence and absorption spectroscopies. These studies indicate that a series of conformational changes occur during the assembly of the TMADH.ETF electron transfer complex and that the kinetics of assembly observed with mutant TMADH (Y442F/L/G) or ETF (alpha R237A) complexes are much slower than are the corresponding rates of electron transfer in these complexes. This suggests that electron transfer does not occur in the thermodynamically most favorable state (which takes too long to form), but that one or more metastable states (which are formed more rapidly) are competent in transferring electrons from TMADH to ETF. Additionally, fluorescence spectroscopy studies of the TMADH.ETF complex indicate that ETF undergoes a stable conformational change (termed structural imprinting) when it interacts transiently with TMADH to form a second, distinct, structural form. The mutant complexes compromise imprinting of ETF, indicating a dependence on the native interactions present in the wild-type complex. The imprinted form of semiquinone ETF exhibits an enhanced rate of electron transfer to the artificial electron acceptor, ferricenium. Overall molecular conformations as probed by small-angle x-ray scattering studies are indistinguishable for imprinted and non-imprinted ETF, suggesting that changes in structure likely involve confined reorganizations within the vicinity of the FAD. Our results indicate a series of conformational events occur during the assembly of the TMADH.ETF electron transfer complex, and that the properties of electron transfer proteins can be affected lastingly by transient interaction with their physiological redox partners. This may have significant implications for our understanding of biological electron transfer reactions in vivo, because ETF encounters TMADH at all times in the cell. Our studies suggest that caution needs to be exercised in extrapolating the properties of in vitro interprotein electron transfer reactions to those occurring in vivo.

Anomalous transport regimes and asymptotic concentration distributions in the presence of advection and diffusion on a comb structure

NASA Astrophysics Data System (ADS)

Dvoretskaya, Olga A.; Kondratenko, Peter S.

2009-04-01

We study the transport of impurity particles on a comb structure in the presence of advection. The main body concentration and asymptotic concentration distributions are obtained. Seven different transport regimes occur on the comb structure with finite teeth: classical diffusion, advection, quasidiffusion, subdiffusion, slow classical diffusion, and two kinds of slow advection. Quasidiffusion deserves special attention. It is characterized by a linear growth of the mean-square displacement. However, quasidiffusion is an anomalous transport regime. We established that a change in transport regimes in time leads to a change in regimes in space. Concentration tails have a cascade structure, namely, consisting of several parts.

Wrinkle ridge-upland scarp transitions: Implications for the mechanical properties of the deformed materials

NASA Technical Reports Server (NTRS)

Watters, Thomas R.; Tuttle, Michael J.; Simpson, Debra

1991-01-01

Wrinkle ridge-upland scarp transitions are structures that occur at the contact between smooth plains material and highlands or uplands materials on the Moon and Mars. In the smooth plains material the structures have a morphology typical of wrinkle ridges, interpreted to be the result of a combination of folding and thrust faulting. Where the structures extend into the uplands, a distinct change in the morphology occurs. The generally asymmetric cross sectional geometry characteristics of wrinkle ridges becomes that of a one-sided, often lobate scarp. The scarp is indistinguishable from other highland/upland scarps, interpreted to be the result of reverse or thrust faulting. Although these structures are rare, they provide important insight into the mechanical properties of deformed materials. These insights are discussed.

[Changes of structures of anterior chamber angle in rabbit chronic high intraocular pressure model].

PubMed

Lei, Xun-wen; Wei, Ping; Li, Xiao-lin; Yang, Kan; Lei, Jian-zhen

2009-10-01

To observe the anterior chamber angle changes occurred in compound Carbomer-induced chronic high intraocular pressure (IOP) model in rabbit eyes. It was an experimental study. Thirty two rabbits were randomly divided into eight groups. Compound Carbomer (0.3%, 0.3 ml) was injected into the left anterior chamber. A group of rabbits were randomly killed after 1, 2, 3, 4, 6, 8, 10 and 12 weeks. The anterior chamber of the rabbit eye specimens was observed. IOP increased slowly following the application of the drug, high IOP lasted for 3 months. The drug-induced changes of anterior chamber angle consisted of early inflammatory response and late fibrous changes. Inflammatory response occurred in early stage and reduced or disappeared after 3 weeks. Fibrous degeneration and adhesion obstruction occurred in the anterior chamber angle after 4 weeks. Under the electron microscope, the trabecular was expanded and deformed, with hyperplasia of collagen and elastic fibers. Endothelial cells were separated from the trabecular, and showed the morphology of lymphocytes, with the function similar to the macrophages. Phagocytized Carbomer particles were transported through the vacuoles of Schlemm's canal endothelial cells. Large vacuoles gradually reduced. Excessive Carbomer particles were accumulated in the endothelial cells and obstructed the Schlemm's canal. This induced the fibrous proliferation and the destruction of anterior chamber angle structures. The obstruction of aqueous humor outflow induced by compound Carbomer in rabbit high IOP model is caused mainly by the changes in trabecular endothelial cells.

Refractive index degeneration in older lenses: A potential functional correlate to structural changes that underlie cataract formation.

PubMed

Bahrami, Mehdi; Hoshino, Masato; Pierscionek, Barbara; Yagi, Naoto; Regini, Justyn; Uesugi, Kentaro

2015-11-01

A major structure/function relationship in the eye lens is that between the constituent proteins, the crystallins and the optical property of refractive index. Structural breakdown that leads to cataract has been investigated in a number of studies; the concomitant changes in the optics, namely increases in light attenuation have also been well documented. Specific changes in the refractive index gradient that cause such attenuation, however, are not well studied because previous methods of measuring refractive index require transparent samples. The X-ray Talbot interferometric method using synchrotron radiation allows for measurement of fine changes in refractive index through lenses with opacities. The findings of this study on older human lenses show disruptions to the refractive index gradient and in the refractive index contours. These disruptions are linked to location in the lens and occur in polar regions, along or close to the equatorial plane or in lamellar-like formations. The disruptions that are seen in the polar regions manifest branching formations that alter with progression through the lens with some similarity to lens sutures. This study shows how the refractive index gradient, which is needed to maintain image quality of the eye, may be disturbed and that this can occur in a number of distinct ways. These findings offer insight into functional changes to a major optical parameter in older lenses. Further studies are needed to elicit how these may be related to structural degenerations reported in the literature. Copyright © 2015 The Authors. Published by Elsevier Ltd.. All rights reserved.

High-resolution CT assessment of the pediatric airways: structure and function

NASA Astrophysics Data System (ADS)

Kramer, Sandra S.; Hoffman, Eric A.; Amirav, Israel

1994-05-01

The airway has always been a central focus for respiratory pathology in infants and children. Imaging of the larynx, trachea, and the central bronchi can be readily accomplished by radiographic or conventional CT techniques. Newer high resolution CT (HRCT) techniques have extended our view of the bronchi peripherally to the limits of scanner resolution, i.e., to bronchial generations 7 - 9, and rapid volumetric CT data acquisitions have made it possible to follow the same lung anatomic level through the rapidly occurring changes in a series of experimental protocols. These techniques together with a custom designed computer software program for image display and analysis have enabled us to objectively study changes in airway caliber and lung density that occurred in an animal mode of airway reactivity and thereby relate structure with function in the airways.

Ultrafast myoglobin structural dynamics observed with an X-ray free-electron laser

DOE PAGES

Levantino, Matteo; Schirò, Giorgio; Lemke, Henrik Till; ...

2015-04-02

Light absorption can trigger biologically relevant protein conformational changes. The light induced structural rearrangement at the level of a photoexcited chromophore is known to occur in the femtosecond timescale and is expected to propagate through the protein as a quake-like intramolecular motion. Here we report direct experimental evidence of such ‘proteinquake’ observed in myoglobin through femtosecond X-ray solution scattering measurements performed at the Linac Coherent Light Source X-ray free-electron laser. An ultrafast increase of myoglobin radius of gyration occurs within 1 picosecond and is followed by a delayed protein expansion. As the system approaches equilibrium it undergoes damped oscillations withmore » a ~3.6-picosecond time period. Our results unambiguously show how initially localized chemical changes can propagate at the level of the global protein conformation in the picosecond timescale.« less

Electro-refractive photonic device

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zortman, William A.; Watts, Michael R.

2015-06-09

The various technologies presented herein relate to phase shifting light to facilitate any of light switching, modulation, amplification, etc. Structures are presented where a second layer is juxtaposed between a first layer and a third layer with respective doping facilitating formation of p-n junctions at the interface between the first layer and the second layer, and between the second layer and the third layer. Application of a bias causes a carrier concentration change to occur at the p-n junctions which causes a shift in the effective refractive index per incremental change in an applied bias voltage. The effective refractive indexmore » enhancement can occur in both reverse bias and forward bias. The structure can be incorporated into a waveguide, an optical resonator, a vertical junction device, a horizontal junction device, a Mach-Zehnder interferometer, a tuneable optical filter, etc.« less

An Electrostatic Charge Partitioning Model for the Dissociation of Protein Complexes in the Gas Phase

NASA Astrophysics Data System (ADS)

Sciuto, Stephen V.; Liu, Jiangjiang; Konermann, Lars

2011-10-01

Electrosprayed multi-protein complexes can be dissociated by collisional activation in the gas phase. Typically, these processes follow a mechanism whereby a single subunit gets ejected with a disproportionately high amount of charge relative to its mass. This asymmetric behavior suggests that the departing subunit undergoes some degree of unfolding prior to being separated from the residual complex. These structural changes occur concomitantly with charge (proton) transfer towards the subunit that is being unraveled. Charge accumulation takes place up to the point where the subunit loses physical contact with the residual complex. This work develops a simple electrostatic model for studying the relationship between conformational changes and charge enrichment during collisional activation. Folded subunits are described as spheres that carry continuum surface charge. The unfolded chain is envisioned as random coil bead string. Simulations are guided by the principle that the system will adopt the charge configuration with the lowest potential energy for any backbone conformation. A finite-difference gradient algorithm is used to determine the charge on each subunit throughout the dissociation process. Both dimeric and tetrameric protein complexes are investigated. The model reproduces the occurrence of asymmetric charge partitioning for dissociation events that are preceded by subunit unfolding. Quantitative comparisons of experimental MS/MS data with model predictions yield estimates of the structural changes that occur during collisional activation. Our findings suggest that subunit separation can occur over a wide range of scission point structures that correspond to different degrees of unfolding.

Phylogenetic fields through time: temporal dynamics of geographical co-occurrence and phylogenetic structure within species ranges

PubMed Central

Carotenuto, Francesco; Diniz-Filho, José Alexandre F.

2016-01-01

Species co-occur with different sets of other species across their geographical distribution, which can be either closely or distantly related. Such co-occurrence patterns and their phylogenetic structure within individual species ranges represent what we call the species phylogenetic fields (PFs). These PFs allow investigation of the role of historical processes—speciation, extinction and dispersal—in shaping species co-occurrence patterns, in both extinct and extant species. Here, we investigate PFs of large mammalian species during the last 3 Myr, and how these correlate with trends in diversification rates. Using the fossil record, we evaluate species' distributional and co-occurrence patterns along with their phylogenetic structure. We apply a novel Bayesian framework on fossil occurrences to estimate diversification rates through time. Our findings highlight the effect of evolutionary processes and past climatic changes on species' distributions and co-occurrences. From the Late Pliocene to the Recent, mammal species seem to have responded in an individualistic manner to climate changes and diversification dynamics, co-occurring with different sets of species from different lineages across their geographical ranges. These findings stress the difficulty of forecasting potential effects of future climate changes on biodiversity. PMID:26977061

Phylogenetic fields through time: temporal dynamics of geographical co-occurrence and phylogenetic structure within species ranges.

PubMed

Villalobos, Fabricio; Carotenuto, Francesco; Raia, Pasquale; Diniz-Filho, José Alexandre F

2016-04-05

Species co-occur with different sets of other species across their geographical distribution, which can be either closely or distantly related. Such co-occurrence patterns and their phylogenetic structure within individual species ranges represent what we call the species phylogenetic fields (PFs). These PFs allow investigation of the role of historical processes--speciation, extinction and dispersal--in shaping species co-occurrence patterns, in both extinct and extant species. Here, we investigate PFs of large mammalian species during the last 3 Myr, and how these correlate with trends in diversification rates. Using the fossil record, we evaluate species' distributional and co-occurrence patterns along with their phylogenetic structure. We apply a novel Bayesian framework on fossil occurrences to estimate diversification rates through time. Our findings highlight the effect of evolutionary processes and past climatic changes on species' distributions and co-occurrences. From the Late Pliocene to the Recent, mammal species seem to have responded in an individualistic manner to climate changes and diversification dynamics, co-occurring with different sets of species from different lineages across their geographical ranges. These findings stress the difficulty of forecasting potential effects of future climate changes on biodiversity. © 2016 The Author(s).

A study of the proteorhodopsin primary photoreaction by low-temperature FTIR difference and ultrafast transient infrared spectroscopy

NASA Astrophysics Data System (ADS)

Amsden, Jason J.

Proteorhodopsin (PR), a newly discovered microbial rhodopsin found in marine proteobacteria, functions as a light-driven proton pump similar to bacteriorhodopsin (BR). PR-containing bacteria account for ˜13% of the microorganisms in the oceans' photic zone and are responsible for a significant fraction of the biosphere's solar energy conversion. We study the initial response of proteorhodopsin to photon absorption using a combination of low-temperature (80 K) Fourier transform infrared (FTIR) difference spectroscopy and ultrafast transient infrared (TIR) spectroscopy. Low-temperature FTIR difference spectroscopy combined with site-directed mutagenesis and isotope labeling is used to detect and characterize changes occurring in the conformation of the retinal chromophore, protein, and internal water molecules of green-absorbing PR (GPR) and blue-absorbing PR (BPR) during the initial phototransition. Measurements on cryogenically trapped intermediates do not accurately reflect all native structural changes occurring in PR and other microbial rhodopsins on ultrafast time scales at room temperature. Recent studies demonstrate that photoactive proteins such as photoactive yellow protein, myoglobin, and green-fluorescent protein, can react within several picoseconds to photon absorption by their chromophores. Faster subpicosecond protein responses have been suggested to occur in rhodopsin-like proteins where retinal chromophore photoisomerization may impulsively drive structural changes in nearby protein groups. Here, I test this possibility by investigating the earliest protein and chromophore structural changes occurring in GPR using ultrafast TIR spectroscopy with ˜200 fs time resolution combined with non-perturbing isotope labeling. On the basis of total-15N and retinal C15D (retinal with a deuterium on carbon 15) isotope labeling, the all-trans to 13-cis retinal chromophore isomerization occurs with a 500-700 fs time constant and the amide II mode of one or more peptide bonds in the protein backbone downshifts in frequency on the same 500--700 fs time scale. This downshift represents the weakening of the hydrogen bonding in one or more peptide bonds in the peptide backbone. Preliminary data on BR indicates that this amide II downshift is a universal feature in microbial rhodopsins. In addition, the protein changes we observe on a subpicosecond time-scale may be involved in storage and transfer of the absorbed photon energy subsequently utilized for proton transport.

Relationship of Chromosome Changes to Neoplastic Cell Transformation

PubMed Central

DiPaolo, Joseph A.; Popescu, Nicolae C.

1976-01-01

Chromosomal abnormalities are a frequent concomitant of neoplasia, and although it is tempting to relate these mutations and alterations in chromatin (DNA) function to cancer, their relationship to the initiation or progression of carcinogenesis is unknown. Mammalian cells in culture, after interacting with chemical carcinogens, often exhibit chromosome damage consisting of breaks and exchanges of chromatid material. The pattern of damage of banded metaphases indicates that negative bands are especially vulnerable to the action of chemical carcinogens, probably because of differential chromatin condensation. Damage to individual chromosomes may be random or nonrandom, depending on the species. Cell death can be correlated with chromatid alterations that occur shortly after treatment with chemical carcinogens. There is also a correlation between mutagenic and carcinogenic activity of some chemical carcinogens and the frequency of sister chromatid exchanges. The question of whether specific chromosome changes are absolutely required for neoplastic transformation cannot be answered because of conflicting data and diverse results from studies even with known carcinogens. Cell transformation may occur without any visible chromosome changes. A universal specific numerical or visible structural chromosomal alteration is not necessarily associated with chemical or viral transformation. Chromosome changes are independent of the etiologic agents: different carcinogens may produce transformation associated with the same abnormal chromosomes, but not all transformed lines invariably exhibit the same abnormality, even with the same chemical. In some species, chromosome having nucleolar organizer regions may be more frequently involved in numerical or structural deviations. Progressively growing tumors also may occur as a result of the proliferation of transformed cells without detectable chromosome changes, indicating that tumorigenicity need not be related to an imbalance of chromosome number or structure. Our studies indicate that chromosome changes are not essential for establishment of neoplasms but that karyotypic instability may result in response to selective growth pressures. ImagesFigure 2Figure 11Figure 3Figure 12Figure 4Figure 5Figure 6Figure 7Figure 8Figure 9Figure 1Figure 10 PMID:826168

The Future of Medical Dosimetry

DOE Office of Scientific and Technical Information (OSTI.GOV)

Adams, Robert D., E-mail: robert_adams@med.unc.edu

2015-07-01

The world of health care delivery is becoming increasingly complex. The purpose of this manuscript is to analyze current metrics and analytically predict future practices and principles of medical dosimetry. The results indicate five potential areas precipitating change factors: a) evolutionary and revolutionary thinking processes, b) social factors, c) economic factors, d) political factors, and e) technological factors. Outcomes indicate that significant changes will occur in the job structure and content of being a practicing medical dosimetrist. Discussion indicates potential variables that can occur within each process and change factor and how the predicted outcomes can deviate from normative values.more » Finally, based on predicted outcomes, future opportunities for medical dosimetrists are given.« less

Monocyte chemotactic protein-1 deficiency attenuates and high-fat diet exacerbates bone loss in mice with Lewis lung carcinoma.

PubMed

Yan, Lin; Nielsen, Forrest H; Sundaram, Sneha; Cao, Jay

2017-04-04

Bone loss occurs in obesity and cancer-associated complications including wasting. This study determined whether a high-fat diet and a deficiency in monocyte chemotactic protein-1 (MCP-1) altered bone structural defects in male C57BL/6 mice with Lewis lung carcinoma (LLC) metastases in lungs. Compared to non-tumor-bearing mice, LLC reduced bone volume fraction, connectivity density, trabecular number, trabecular thickness and bone mineral density and increased trabecular separation in femurs. Similar changes occurred in vertebrae. The high-fat diet compared to the AIN93G diet exacerbated LLC-induced detrimental structural changes; the exacerbation was greater in femurs than in vertebrae. Mice deficient in MCP-1 compared to wild-type mice exhibited increases in bone volume fraction, connectivity density, trabecular number and decreases in trabecular separation in both femurs and vertebrae, and increases in trabecular thickness and bone mineral density and a decrease in structure model index in vertebrae. Lewis lung carcinoma significantly decreased osteocalcin but increased tartrate-resistant acid phosphatase 5b (TRAP 5b) in plasma. In LLC-bearing mice, the high-fat diet increased and MCP-1 deficiency decreased plasma TRAP 5b; neither the high-fat diet nor MCP-1 deficiency resulted in significant changes in plasma concentration of osteocalcin. In conclusion, pulmonary metastasis of LLC is accompanied by detrimental bone structural changes; MCP-1 deficiency attenuates and high-fat diet exacerbates the metastasis-associated bone wasting.

Geographic patterns of genetic variation and population structure in Pinus aristata, Rocky Mountain bristlecone pine

Treesearch

Anna W. Schoettle; Betsy A. Goodrich; Valerie Hipkins; Christopher Richards; Julie Kray

2012-01-01

Pinus aristata Engelm., Rocky Mountain bristlecone pine, has a narrow core geographic and elevational distribution, occurs in disjunct populations, and is threatened by rapid climate change, white pine blister rust, and bark beetles. Knowledge of genetic diversity and population structure will help guide gene conservation strategies for this species. Sixteen sites...

Physical modeling of the formation and evolution of seismically active fault zones

USGS Publications Warehouse

Ponomarev, A.V.; Zavyalov, A.D.; Smirnov, V.B.; Lockner, D.A.

1997-01-01

Acoustic emission (AE) in rocks is studied as a model of natural seismicity. A special technique for rock loading has been used to help study the processes that control the development of AE during brittle deformation. This technique allows us to extend to hours fault growth which would normally occur very rapidly. In this way, the period of most intense interaction of acoustic events can be studied in detail. Characteristics of the acoustic regime (AR) include the Gutenberg-Richter b-value, spatial distribution of hypocenters with characteristic fractal (correlation) dimension d, Hurst exponent H, and crack concentration parameter Pc. The fractal structure of AR changes with the onset of the drop in differential stress during sample deformation. The change results from the active interaction of microcracks. This transition of the spatial distribution of AE hypocenters is accompanied by a corresponding change in the temporal correlation of events and in the distribution of event amplitudes as signified by a decrease of b-value. The characteristic structure that develops in the low-energy background AE is similar to the sequence of the strongest microfracture events. When the AR fractal structure develops, the variations of d and b are synchronous and d = 3b. This relation which occurs once the fractal structure is formed only holds for average values of d and b. Time variations of d and b are anticorrelated. The degree of temporal correlation of AR has time variations that are similar to d and b variations. The observed variations in laboratory AE experiments are compared with natural seismicity parameters. The close correspondence between laboratory-scale observations and naturally occurring seismicity suggests a possible new approach for understanding the evolution of complex seismicity patterns in nature. ?? 1997 Elsevier Science B.V. All rights reserved.

Comparative Analyses of Reproductive Structures in Harvestmen (Opiliones) Reveal Multiple Transitions from Courtship to Precopulatory Antagonism

PubMed Central

Burns, Mercedes M.; Hedin, Marshal; Shultz, Jeffrey W.

2013-01-01

Explaining the rapid, species-specific diversification of reproductive structures and behaviors is a long-standing goal of evolutionary biology, with recent research tending to attribute reproductive phenotypes to the evolutionary mechanisms of female mate choice or intersexual conflict. Progress in understanding these and other possible mechanisms depends, in part, on reconstructing the direction, frequency and relative timing of phenotypic evolution of male and female structures in species-rich clades. Here we examine evolution of reproductive structures in the leiobunine harvestmen or “daddy long-legs” of eastern North America, a monophyletic group that includes species in which males court females using nuptial gifts and other species that are equipped for apparent precopulatory antagonism (i.e., males with long, hardened penes and females with sclerotized pregenital barriers). We used parsimony- and Bayesian likelihood-based analyses to reconstruct character evolution in categorical reproductive traits and found that losses of ancestral gift-bearing penile sacs are strongly associated with gains of female pregenital barriers. In most cases, both events occur on the same internal branch of the phylogeny. These coevolutionary changes occurred at least four times, resulting in clade-specific designs in the penis and pregenital barrier. The discovery of convergent origins and/or enhancements of apparent precopulatory antagonism among closely related species offers an unusual opportunity to investigate how major changes in reproductive morphology have occurred. We propose new hypotheses that attribute these enhancements to changes in ecology or life history that reduce the duration of breeding seasons, an association that is consistent with female choice, sexual conflict, and/or an alternative evolutionary mechanism. PMID:23762497

Pioneer and Voyager observations of the solar wind at large heliocentric distances and latitudes

NASA Technical Reports Server (NTRS)

Gazis, P. R.; Mihalov, J. D.; Barnes, A.; Lazarus, A. J.; Smith, E. J.

1989-01-01

Data obtained from the electrostatic analyzers aboard the Pioneer 10 and 11 spacecraft and from the Faraday cup aboard Voyager 2 were used to study spatial gradients in the distant solar wind. Prior to mid-1985, both spacecraft observed nearly identical solar wind structures. After day 150 of 1985, the velocity structure at Voyager 2 became flatter, and the Voyager 2 velocities were smaller than those observed by Pioneer 11. It is suggested that these changes in the solar wind at low latitudes may be related to a change which occurred in the coronal hole structure in early 1985.

Interrogation of bimetallic particle oxidation in three dimensions at the nanoscale

PubMed Central

Han, Lili; Meng, Qingping; Wang, Deli; Zhu, Yimei; Wang, Jie; Du, Xiwen; Stach, Eric A.; Xin, Huolin L.

2016-01-01

An understanding of bimetallic alloy oxidation is key to the design of hollow-structured binary oxides and the optimization of their catalytic performance. However, one roadblock encountered in studying these binary oxide systems is the difficulty in describing the heterogeneities that occur in both structure and chemistry as a function of reaction coordinate. This is due to the complexity of the three-dimensional mosaic patterns that occur in these heterogeneous binary systems. By combining real-time imaging and chemical-sensitive electron tomography, we show that it is possible to characterize these systems with simultaneous nanoscale and chemical detail. We find that there is oxidation-induced chemical segregation occurring on both external and internal surfaces. Additionally, there is another layer of complexity that occurs during the oxidation, namely that the morphology of the initial oxide surface can change the oxidation modality. This work characterizes the pathways that can control the morphology in binary oxide materials. PMID:27928998

Computational Morphometry for Detecting Changes in Brain Structure Due to Development, Aging, Learning, Disease and Evolution

PubMed Central

Mietchen, Daniel; Gaser, Christian

2009-01-01

The brain, like any living tissue, is constantly changing in response to genetic and environmental cues and their interaction, leading to changes in brain function and structure, many of which are now in reach of neuroimaging techniques. Computational morphometry on the basis of Magnetic Resonance (MR) images has become the method of choice for studying macroscopic changes of brain structure across time scales. Thanks to computational advances and sophisticated study designs, both the minimal extent of change necessary for detection and, consequently, the minimal periods over which such changes can be detected have been reduced considerably during the last few years. On the other hand, the growing availability of MR images of more and more diverse brain populations also allows more detailed inferences about brain changes that occur over larger time scales, way beyond the duration of an average research project. On this basis, a whole range of issues concerning the structures and functions of the brain are now becoming addressable, thereby providing ample challenges and opportunities for further contributions from neuroinformatics to our understanding of the brain and how it changes over a lifetime and in the course of evolution. PMID:19707517

Local and global structural drivers for the photoactivation of the orange carotenoid protein

DOE PAGES

Gupta, Sayan; Guttman, Miklos; Leverenz, Ryan L.; ...

2015-09-18

Here, photoprotective mechanisms are of fundamental importance for the survival of photosynthetic organisms. In cyanobacteria, the orange carotenoid protein (OCP), when activated by intense blue light, binds to the light-harvesting antenna and triggers the dissipation of excess captured light energy. Using a combination of small angle X-ray scattering (SAXS), X-ray hydroxyl radical footprinting, circular dichroism, and H/D exchange mass spectrometry, we identified both the local and global structural changes in the OCP upon photoactivation. SAXS and H/D exchange data showed that global tertiary structural changes, including complete domain dissociation, occur upon photoactivation, but with alteration of secondary structure confined tomore » only the N terminus of the OCP. Microsecond radiolytic labeling identified rearrangement of the H-bonding network associated with conserved residues and structural water molecules. Collectively, these data provide experimental evidence for an ensemble of local and global structural changes, upon activation of the OCP, that are essential for photoprotection.« less

Local and global structural drivers for the photoactivation of the orange carotenoid protein

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gupta, Sayan; Guttman, Miklos; Leverenz, Ryan L.

Here, photoprotective mechanisms are of fundamental importance for the survival of photosynthetic organisms. In cyanobacteria, the orange carotenoid protein (OCP), when activated by intense blue light, binds to the light-harvesting antenna and triggers the dissipation of excess captured light energy. Using a combination of small angle X-ray scattering (SAXS), X-ray hydroxyl radical footprinting, circular dichroism, and H/D exchange mass spectrometry, we identified both the local and global structural changes in the OCP upon photoactivation. SAXS and H/D exchange data showed that global tertiary structural changes, including complete domain dissociation, occur upon photoactivation, but with alteration of secondary structure confined tomore » only the N terminus of the OCP. Microsecond radiolytic labeling identified rearrangement of the H-bonding network associated with conserved residues and structural water molecules. Collectively, these data provide experimental evidence for an ensemble of local and global structural changes, upon activation of the OCP, that are essential for photoprotection.« less

Kinetic and Surface Study of Single-Walled Aluminosilicate Nanotubes and Their Precursors

PubMed Central

Arancibia-Miranda, Nicolás; Escudey, Mauricio; Molina, Mauricio; García-González, María Teresa

2013-01-01

The structural and surface changes undergone by the different precursors that are produced during the synthesis of imogolite are reported. The surface changes that occur during the synthesis of imogolite were determined by electrophoretic migration (EM) measurements, which enabled the identification of the time at which the critical precursor of the nanoparticles was generated. A critical parameter for understanding the evolution of these precursors is the isoelectric point (IEP), of which variation revealed that the precursors modify the number of active ≡Al-OH and ≡Si-OH sites during the formation of imogolite. We also found that the IEP is displaced to a higher pH level as a consequence of the surface differentiation that occurs during the synthesis. At the same time, we established that the pH of the reaction (pHrx) decreases with the evolution and condensation of the precursors during aging. Integration of all of the obtained results related to the structural and surface properties allows an overall understanding of the different processes that occur and the products that are formed during the synthesis of imogolite. PMID:28348326

From open to closed canopy: A century of change in Douglas-fir forest, Orcas Island, Washington

USGS Publications Warehouse

Peterson, D.L.; Hammer, R.D.

2001-01-01

During the past century, forest structure on south-facing slopes of Mount Constitution, Orcas Island, Washington, has changed from open-grown Douglas-fir (Pseudotsuga menziesii) mixed with prairie to primarily closed canopy forest. Density of open-grown Douglas-fir was approximately 7 stems/ha in the 19th century, while current density of trees in closed-canopy mature forest is 426 stems/ha. Trees occur at intermediate densities in areas of transition from savanna-like stands to closed canopy. Analysis of fire scars indicates that at least seven fires have occurred on Mount Constitution since 1736, but only one fire has occurred since 1893, which suggests that the recent increase in stem density has been caused primarily by fire exclusion. The high stem densities currently found in this landscape put the relict (120-350+ years old) Douglas-fir at risk from contemporary fires, which would likely be high-intensity crown fires. Given the transition of forests on Orcas Island during the 20th century to closed canopy structure, undisturbed open-grown coniferous forest is now extremely rare in the San Juan Islands.

Kinetic and Surface Study of Single-Walled Aluminosilicate Nanotubes and Their Precursors.

PubMed

Arancibia-Miranda, Nicolás; Escudey, Mauricio; Molina, Mauricio; García-González, María Teresa

2013-03-01

The structural and surface changes undergone by the different precursors that are produced during the synthesis of imogolite are reported. The surface changes that occur during the synthesis of imogolite were determined by electrophoretic migration (EM) measurements, which enabled the identification of the time at which the critical precursor of the nanoparticles was generated. A critical parameter for understanding the evolution of these precursors is the isoelectric point (IEP), of which variation revealed that the precursors modify the number of active ≡Al-OH and ≡Si-OH sites during the formation of imogolite. We also found that the IEP is displaced to a higher pH level as a consequence of the surface differentiation that occurs during the synthesis. At the same time, we established that the pH of the reaction (pH rx ) decreases with the evolution and condensation of the precursors during aging. Integration of all of the obtained results related to the structural and surface properties allows an overall understanding of the different processes that occur and the products that are formed during the synthesis of imogolite.

How Colleges Use Integrated Planning and Advising for Student Success (iPASS) to Transform Student Support. CCRC Working Paper No. 89

ERIC Educational Resources Information Center

Karp, Melinda Mechur; Kalamkarian, Hoori Santikian; Klempin, Serena; Fletcher, Jeffrey

2016-01-01

This paper examines technology-mediated advising reform in order to contribute to the understanding of how colleges engage in transformative change to improve student outcomes. Conceptualizing such change as occurring along three interrelated dimensions of organizational functioning (structural, process, and attitudinal), we seek to understand the…

Changing tree composition by life history strategy in a grassland-forest landscape

Treesearch

Brice B. Hanberry; John M. Kabrick; Hong S. He

2014-01-01

After rapid deforestation in the eastern United States, which generally occurred during the period of 1850-1920, forests did not return to historical composition and structure. We examined forest compositional change and then considered how historical land use and current land use may influence forests in a grassland-forest landscape, the Missouri Plains, where...

Constructing Disability in Bhutan: Schools, Structures, Policies, and Global Discourses

ERIC Educational Resources Information Center

Schuelka, Matthew John

2014-01-01

Bhutan is a small country in the Himalaya that has experienced rapid societal changes in the past 60 years. Perhaps the most significant change in Bhutan has occurred in its educational system, which grew from a very limited presence in 1961 to now serving the entire youth population of Bhutan. With this massive increase in educational service…

Structural alterations of thin actin filaments in muscle contraction by synchrotron X-ray fiber diffraction.

PubMed

Wakabayashi, Katsuzo; Sugimoto, Yasunobu; Takezawa, Yasunori; Ueno, Yutaka; Minakata, Shiho; Oshima, Kanji; Matsuo, Tatsuhito; Kobayashi, Takakazu

2007-01-01

Strong evidence has been accumulated that the conformational changes of the thin actin filaments are occurring and playing an important role in the entire process of muscle contraction. The conformational changes and the mechanical properties of the thin actin filaments we have found by X-ray fiber diffraction on skeletal muscle contraction are explored. Recent studies on the conformational changes of regulatory proteins bound to actin filaments upon activation and in the force generation process are also described. Finally, the roles of structural alterations and dynamics of the actin filaments are discussed in conjunction with the regulation mechanism and the force generation mechanism.

[Topographological-anatomic changes in the structure of temporo-mandibular joint in case of fracture of the mandible condylar process at cervical level].

PubMed

Volkov, S I; Bazhenov, D V; Semkin, V A

2011-01-01

Pathological changes in soft tissues surrounding the fracture site as well as in the structural elements of temporo-mandibular joint always occured in condylar process fracture with shift at cervical mandibular jaw level. Other changes were also seen in the joint on the opposite normal side. Modelling of condylar process fracture at mandibular cervical level by means of three-dimensional computer model of temporo-mandibular joint contributed to proper understanding of this pathology emergence as well as to prediction and elimination of disorders arising in adjacent to the fracture site tissues.

Structure for identifying, locating and quantifying physical phenomena

DOEpatents

Richardson, John G.

2006-10-24

A method and system for detecting, locating and quantifying a physical phenomena such as strain or a deformation in a structure. A minimum resolvable distance along the structure is selected and a quantity of laterally adjacent conductors is determined. Each conductor includes a plurality of segments coupled in series which define the minimum resolvable distance along the structure. When a deformation occurs, changes in the defined energy transmission characteristics along each conductor are compared to determine which segment contains the deformation.

Method and apparatus for identifying, locating and quantifying physical phenomena and structure including same

DOEpatents

Richardson, John G.

2006-01-24

A method and system for detecting, locating and quantifying a physical phenomena such as strain or a deformation in a structure. A minimum resolvable distance along the structure is selected and a quantity of laterally adjacent conductors is determined. Each conductor includes a plurality of segments coupled in series which define the minimum resolvable distance along the structure. When a deformation occurs, changes in the defined energy transmission characteristics along each conductor are compared to determine which segment contains the deformation.

Time-domain separation of optical properties from structural transitions in resonantly bonded materials.

PubMed

Waldecker, Lutz; Miller, Timothy A; Rudé, Miquel; Bertoni, Roman; Osmond, Johann; Pruneri, Valerio; Simpson, Robert E; Ernstorfer, Ralph; Wall, Simon

2015-10-01

The extreme electro-optical contrast between crystalline and amorphous states in phase-change materials is routinely exploited in optical data storage and future applications include universal memories, flexible displays, reconfigurable optical circuits, and logic devices. Optical contrast is believed to arise owing to a change in crystallinity. Here we show that the connection between optical properties and structure can be broken. Using a combination of single-shot femtosecond electron diffraction and optical spectroscopy, we simultaneously follow the lattice dynamics and dielectric function in the phase-change material Ge2Sb2Te5 during an irreversible state transformation. The dielectric function changes by 30% within 100 fs owing to a rapid depletion of electrons from resonantly bonded states. This occurs without perturbing the crystallinity of the lattice, which heats with a 2-ps time constant. The optical changes are an order of magnitude larger than those achievable with silicon and present new routes to manipulate light on an ultrafast timescale without structural changes.

Mechanism of T7 RNAP pausing and termination at the T7 concatemer junction: a local change in transcription bubble structure drives a large change in transcription complex architecture.

PubMed

Nayak, Dhananjaya; Siller, Sylvester; Guo, Qing; Sousa, Rui

2008-02-15

The T7RNA polymerase (RNAP) elongation complex (EC) pauses and is destabilized at a unique 8 nucleotide (nt) sequence found at the junction of the head-to-tail concatemers of T7 genomic DNA generated during T7 DNA replication. The paused EC may recruit the T7 DNA processing machinery, which cleaves the concatemerized DNA within this 8 nt concatemer junction (CJ). Pausing of the EC at the CJ involves structural changes in both the RNAP and transcription bubble. However, these structural changes have not been fully defined, nor is it understood how the CJ sequence itself causes the EC to change its structure, to pause, and to become less stable. Here we use solution and RNAP-tethered chemical nucleases to probe the CJ transcript and changes in the EC structure as the polymerase pauses and terminates at the CJ. Together with extensive mutational scanning of regions of the polymerase that are likely to be involved in recognition of the CJ, we are able to develop a description of the events that occur as the EC transcribes through the CJ and subsequently pauses. In this process, a local change in the structure of the transcription bubble drives a large change in the architecture of the EC. This altered EC structure may then serve as the signal that recruits the processing machinery to the CJ.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gargarella, P., E-mail: piter@ufscar.br; Departamento de Engenharia de Materiais, Universidade Federal de São Carlos, Rodovia Washington Luiz, Km 235, 13565-905 São Carlos, São Paulo; Pauly, S.

The structural evolution of Ti{sub 50}Cu{sub 43}Ni{sub 7} and Ti{sub 55}Cu{sub 35}Ni{sub 10} metallic glasses during heating was investigated by in-situ synchrotron X-ray diffraction. The width of the most intense diffraction maximum of the glassy phase decreases slightly during relaxation below the glass transition temperature. Significant structural changes only occur above the glass transition manifesting in a change in the respective peak positions. At even higher temperatures, nanocrystals of the shape memory B2-Ti(Cu,Ni) phase precipitate, and their small size hampers the occurrence of a martensitic transformation.

Energy Based Topology Optimization of Morphing Wings a Multidisciplinary Global/Local Design Approach

DTIC Science & Technology

2006-12-01

subsystem that drives the active materials to achieve the desired shape changes. As opposed to fixed wing structures in which the aerodynamic and...structures and aerodynamics occur in conjunction with the active material and electronic subsystem interactions that involve transfer of energy from a source...which the aerodynamic and structure integration for the entire wing is the most important interaction mechanism, in the case of a morphing wing

Structural phase transition of magnetic [Ni(dmit)2]- salts induced by supramolecular cation structures of (M+)([12]crown-4)2.

PubMed

Akutagawa, Tomoyuki; Motokizawa, Takeshi; Matsuura, Kazumasa; Nishihara, Sadafumi; Noro, Shin-ichiro; Nakamura, Takayoshi

2006-03-30

Sandwich-type supramolecular cation structures of (M(+))([12]crown-4)(2) complexes (M(+) = Li(+), Na(+), K(+), and Rb(+)) were introduced as countercations to the [Ni(dmit)(2)](-) anion, which bears an S = (1)/(2) spin, to form novel magnetic crystals (dmit(2-) = 2-thione-1,3-dithiole-4,5-dithiolate). The zigzag arrangement of Li(+)([12]crown-4)(2) cations in Li(+)([12]crown-4)(2)[Ni(dmit)(2)](-) salt induced weak intermolecular interactions of [Ni(dmit)(2)](-) dimers, whose magnetic spins were isolated from each other. The molecular arrangements of cations and anions in M(+)([12]crown-4)(2)[Ni(dmit)(2)](-) salts (M(+) = Na(+), K(+), and Rb(+)) were isostructural to each other. In the case of Na(+)([12]crown-4)(2)[Ni(dmit)(2)](-), the space group C2/m changed to C2/c with a lowering in temperature from 298 to 100 K. This structural change occurred at 222.5 K as a first-order phase transition. The space group C2/m (T = 298 K) in the salt K(+)([12]crown-4)(2)[Ni(dmit)(2)](-) also changed to C2/c (T = 100 K), which transition occurred at 270 K. Crystal structural analyses at 298 and 100 K revealed changes in both supramolecular cation conformation and [Ni(dmit)(2)](-) anion arrangements. The transition from C2/m to C2/c crystals generated a dipole moment in the Na(+)([12]crown-4)(2) and K(+)([12]crown-4)(2) structures, which were reconstructed to cancel the net dipole moment of the C2/c crystals. These cation transformations led to changes in intermolecular interactions between the [Ni(dmit)(2)](-) anions via structural rearrangements. The crystal structure of C2/c was stabilized in Rb(+)([12]crown-4)(2)[Ni(dmit)(2)](-) at 298 K. The [Ni(dmit)(2)](-) configuration in these salts with the C2/c space group was a one-dimensional uniform chain, which showed the temperature-dependent magnetic susceptibility of a one-dimensional linear Heisenberg antiferromagnetic chain.

Deciphering the Biophysical Effects of Oxidizing Sulfur-Containing Amino Acids in Interferon-beta-1a using MS and HDX-MS

NASA Astrophysics Data System (ADS)

Houde, Damian J.; Bou-Assaf, George M.; Berkowitz, Steven A.

2017-05-01

Introduction of a chemical change to one or more amino acids in a protein's polypeptide chain can result in various effects on its higher-order structure (HOS) and biophysical behavior (or properties). These effects range from no detectable change to significant structural or conformational alteration that can greatly affect the protein's biophysical properties and its resulting biological function. The ability to reliably detect the absence or presence of such changes is essential to understanding the structure-function relationship in a protein and in the successful commercial development of protein-based drugs (biopharmaceuticals). In this paper, we focus our attention on the latter by specifically elucidating the impact of oxidation on the HOS, structural dynamics, and biophysical properties of interferon beta-1a (IFNβ-1a). Oxidation is a common biochemical modification that occurs in many biopharmaceuticals, specifically in two naturally-occurring sulfur-containing amino acids, methionine and cysteine. To carry out this work, we used combinations of hydrogen peroxide and pH to differentially oxidize IFNβ-1a (to focus on only methionine oxidation versus methionine and cysteine oxidation). We then employed several analytical and biophysical techniques to acquire information about the differential impact of these two oxidation scenarios on IFNβ-1a. In particular, the use of MS-based techniques, especially HDX-MS, play a dominant role in revealing the differential effects.

Structure of the first- and second-neighbor shells of simulated water: Quantitative relation to translational and orientational order

NASA Astrophysics Data System (ADS)

Yan, Zhenyu; Buldyrev, Sergey V.; Kumar, Pradeep; Giovambattista, Nicolas; Debenedetti, Pablo G.; Stanley, H. Eugene

2007-11-01

We perform molecular dynamics simulations of water using the five-site transferable interaction potential (TIP5P) model to quantify structural order in both the first shell (defined by four nearest neighbors) and second shell (defined by twelve next-nearest neighbors) of a central water molecule. We find that the anomalous decrease of orientational order upon compression occurs in both shells, but the anomalous decrease of translational order upon compression occurs mainly in the second shell. The decreases of translational order and orientational order upon compression (called the “structural anomaly”) are thus correlated only in the second shell. Our findings quantitatively confirm the qualitative idea that the thermodynamic, structural, and hence dynamic anomalies of water are related to changes upon compression in the second shell.

Safe structures for future aircraft

NASA Technical Reports Server (NTRS)

Mccomb, H. G., Jr.

1983-01-01

The failure mechanisms, design lessons, and test equipment employed by NASA in establishing the airworthiness and crashworthiness of aircraft components for commercial applications are described. The composites test programs have progressed to medium primary structures such as stabilizers and a vertical fin. The failures encountered to date have been due to the nonyielding nature of composites, which do not diffuse loads like metals, and the presence of eccentricities, irregular shapes, stiffness changes, and discontinuities that cause tension and shear. Testing to failure, which always occurred in first tests before the design loads were reached, helped identify design changes and reinforcements that produced successful products. New materials and NDE techniques are identified, together with aircraft structural design changes that offer greater protection to the passengers, fuel antimisting agents, and landing gear systems.

Biological Ion Exchanger Resins

PubMed Central

Damadian, Raymond; Goldsmith, Michael; Zaner, K. S.

1971-01-01

Biological selectivity is shown to vary with medium osmotic strength and temperature. Selectivity reversals occur at 4°C and at an external osmolality of 0.800 indicating that intracellular hydration and endosolvent (intracellular water) structure are important determinants in selectivity. Magnetic resonance measurements of line width by steady-state nuclear magnetic resonance (NMR) indicate a difference in the intracellular water signal of 16 Hz between the K form and Na form of Escherichia coli, providing additional evidence that changes in the ionic composition of cells are accompanied by changes in endosolvent structure. The changes were found to be consistent with the thermodynamic and magnetic resonance properties of aqueous electrolyte solutions. Calculation of the dependence of ion-pairing forces on medium dielectric reinforces the role of endosolvent structure in determining ion exchange selectivity. PMID:4943653

Femtosecond Structural Dynamics Drives the Trans/Cis Isomerization in Photoactive Yellow Protein

PubMed Central

Pande, Kanupriya; Hutchison, Christopher D. M.; Groenhof, Gerrit; Aquila, Andy; Robinson, Josef S.; Tenboer, Jason; Basu, Shibom; Boutet, Sébastien; DePonte, Daniel P.; Liang, Mengning; White, Thomas A.; Zatsepin, Nadia A.; Yefanov, Oleksandr; Morozov, Dmitry; Oberthuer, Dominik; Gati, Cornelius; Subramanian, Ganesh; James, Daniel; Zhao, Yun; Koralek, Jake; Brayshaw, Jennifer; Kupitz, Christopher; Conrad, Chelsie; Roy-Chowdhury, Shatabdi; Coe, Jesse D.; Metz, Markus; Xavier, Paulraj Lourdu; Grant, Thomas D.; Koglin, Jason E.; Ketawala, Gihan; Fromme, Raimund; Šrajer, Vukica; Henning, Robert; Spence, John C. H.; Ourmazd, Abbas; Schwander, Peter; Weierstall, Uwe; Frank, Matthias; Fromme, Petra; Barty, Anton; Chapman, Henry N.; Moffat, Keith; van Thor, Jasper J.; Schmidt, Marius

2017-01-01

A variety of organisms have evolved mechanisms to detect and respond to light, in which the response is mediated by protein structural changes following photon absorption. The initial step is often the photo-isomerization of a conjugated chromophore. Isomerization occurs on ultrafast timescales, and is substantially influenced by the chromophore environment. Here we identify structural changes associated with the earliest steps in the trans to cis isomerization of the chromophore in photoactive yellow protein. Femtosecond, hard X-ray pulses emitted by the Linac Coherent Light Source were used to conduct time-resolved serial femtosecond crystallography on PYP microcrystals over the time range from 100 femtoseconds to 3 picoseconds to determine the structural dynamics of the photoisomerization reaction. PMID:27151871

Alabama's forests, 2000

Treesearch

Andrew J. Hartsell; Tony G. Johnson

2009-01-01

The principle findings of the seventh forest survey of Alabama (2000) and changes that have occurred since the previous surveys are presented. Topics examined include forest area, ownership, forest-type groups, stand structure, basal area, timber volume, growth, removals, and mortality.

Alabama's Forests, 2005

Treesearch

Andrew J. Hartsell; Tony G. Johnson

2009-01-01

The principle findings of the eighth forest survey of Alabama (2005) and changes that have occurred since the previous surveys are presented. Topics examined include forest area, ownership, forest-type groups, stand structure, basal area, timber volume, growth removals, and mortality.

First principles investigation of the unipolar resistive switching mechanism in an interfacial phase change memory based on a GeTe/Sb2Te3 superlattice

NASA Astrophysics Data System (ADS)

Shirakawa, Hiroki; Araidai, Masaaki; Shiraishi, Kenji

2018-04-01

The interfacial phase change memory (iPCM) based on a GeTe/Sb2Te3 superlattice is one of the candidates for future storage class memories. However, the atomic structures of the high and low resistance states (HRS/LRS) remain unclear and the resistive switching mechanism is still under debate. Clarifying the switching mechanism is essential for developing further high-reliability and low-power-consumption iPCM. We propose, on the basis of the results of first-principles molecular dynamics simulations, a mechanism for resistive switching, and describe the atomic structures of the high and low resistance states of iPCM for unipolar switching. Our simulations indicated that switching from HRS to LRS occurs with Joule heating only, while that from LRS to HRS occurs with both hole injection and Joule heating.

The hazard map of ML6.6 0206 Meinong earthquake near Guanmiao and its Neotectonic implication

NASA Astrophysics Data System (ADS)

Chung, L. H.; Shyu, J. B. H.; Huang, M. H.; Yang, K. M.; Le Beon, M.; Lee, Y. H.; Chuang, R.; Yi, D.

2016-12-01

The serious damage was occurred in SW Taiwan by ML 6.6 0206 Meinong earthquake. Based on InSAR result, 10 cm oval-raised surface deformation is 15 km away from its epicenter, and two obviously N-S trend sharp phase change nearby Guanmiao area. Our field investigation shows bulling damage and surface fracture are high related with the two sharp phase change. Here, we perform the detailed shallow underground geometry by using reflection seismic data, geologic data, and field hazard investigation. This N-S trend surface deformation may be induced by local shallow folding, while the huge uplift west of Guanmiao may be related with pure shear deformation of thick clayey Gutingkeng (GTK) Formation. Our results imply that not only a moderate lower crustal earthquake can trigger active structure at shallower depth, but also those minor shallow active structures are occurred serious damage and surface deformation.

[Structural plasticity associated with drugs addiction].

PubMed

Zhu, Jie; Cao, Guo-fen; Dang, Yong-hui; Chen, Teng

2011-12-01

An essential feature of drug addiction is that an individual continues to use drug despite the threat of severely adverse physical or psychosocial consequences. Persistent changes in behavior and psychological function that occur as a function of drugs of abuse are thought to be due to the reorganization of synaptic connections (structural plasticity) in relevant brain circuits (especially the brains reward circuits). In this paper we summarized evidence that, indeed, exposure to amphetamine, cocaine, nicotine or morphine produced persistent changes in the structure of dendrites and dendritic spines on cells in relevant brain regions. We also approached the potential molecular mechanisms of these changes. It is suggested that structural plasticity associated with exposure to drugs of abuse reflects a reorganization of patterns of synaptic connectivity in these neural systems, a reorganization that alters their operation, thus contributing to some of the persistent sequela associated with drug use-including addiction.

Extended Fenske-Hall LCAO MO Calculations for Mixed Methylene Dihalides

NASA Astrophysics Data System (ADS)

Ziemann, Hartmut; Paulun, Manfred

1988-10-01

The electronic structure of mixed methylene dihalides CH2XY (X, Y = F, Cl, Br. I) has been studied using extended Fenske-Hall LCAO MO method. The comparison with available photoelec­tron spectra confirmes previous assignments of all bands with binding energies <100 eV. The electronic structure changes occurring upon varying the halogen substituents are discussed.

Kinetics and fracture resistance of lithiated silicon nanostructure pairs controlled by their mechanical interaction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lee, Seok Woo; /Stanford U., Geballe Lab.; Lee, Hyun-Wook

2015-06-01

Following an explosion of studies of silicon as a negative electrode for Li-ion batteries, the anomalous volumetric changes and fracture of lithiated single Si particles have attracted significant attention in various fields, including mechanics. However, in real batteries, lithiation occurs simultaneously in clusters of Si in a confined medium. Hence, understanding how the individual Si structures interact during lithiation in a closed space is necessary. Herein, we demonstrate physical/mechanical interactions of swelling Si structures during lithiation using well-defined Si nanopillar pairs. Ex situ SEM and in situ TEM studies reveal that compressive stresses change the reaction kinetics so that preferentialmore » lithiation occurs at free surfaces when the pillars are mechanically clamped. Such mechanical interactions enhance the fracture resistance of This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, Division of Materials Sciences and Engineering, under Contract No. DE-AC02-76SF00515. SLAC-PUB-16300 2 lithiated Si by lessening the tensile stress concentrations in Si structures. This study will contribute to improved design of Si structures at the electrode level for high performance Li-ion batteries.« less

Global Low Frequency Protein Motions in Long-Range Allosteric Signaling

NASA Astrophysics Data System (ADS)

McLeish, Tom; Rogers, Thomas; Townsend, Philip; Burnell, David; Pohl, Ehmke; Wilson, Mark; Cann, Martin; Richards, Shane; Jones, Matthew

2015-03-01

We present a foundational theory for how allostery can occur as a function of low frequency dynamics without a change in protein structure. Elastic inhomogeneities allow entropic ``signalling at a distance.'' Remarkably, many globular proteins display just this class of elastic structure, in particular those that support allosteric binding of substrates (long-range co-operative effects between the binding sites of small molecules). Through multi-scale modelling of global normal modes we demonstrate negative co-operativity between the two cAMP ligands without change to the mean structure. Crucially, the value of the co-operativity is itself controlled by the interactions around a set of third allosteric ``control sites.'' The theory makes key experimental predictions, validated by analysis of variant proteins by a combination of structural biology and isothermal calorimetry. A quantitative description of allostery as a free energy landscape revealed a protein ``design space'' that identified the key inter- and intramolecular regulatory parameters that frame CRP/FNR family allostery. Furthermore, by analyzing naturally occurring CAP variants from diverse species, we demonstrate an evolutionary selection pressure to conserve residues crucial for allosteric control. The methodology establishes the means to engineer allosteric mechanisms that are driven by low frequency dynamics.

Theoretical Studies of Gas Phase Elementary and Carbon Nanostructure Growth Reactions

DTIC Science & Technology

2013-09-19

time dynamics of electron transfer in a prototype redox reaction that occurs in reactive collisions between neutral and ionic fullerenes is discussed...The LvNMD show that the electron transfer occurs within 60 fs directly preceding the collision of the fullerenes , followed by structural changes...collisions between neutral and multiply charged fullerenes . 2 B. Collaboration with the AFRL. Collaboration with the VIggiano group at AFRL at

Financing reform and structural change in the health services industry.

PubMed

Higgins, C W; Phillips, B U

1986-08-01

This paper reviews the major trends in financing reform, emphasizing their impact on those characteristics of the market for health services that economists have viewed as monopolistic, and discusses the implications of structural change for the allied health professions. Hopefully, by understanding the fundamental forces of change and responding to uncertainty with flexibility and imagination, the allied health professions can capitalize on the opportunities afforded by structural change. Overall, these trends should result in the long-term outlook for use of allied health services to increase at an average annual rate of 9% to 10%. Allied health professionals may also witness an increase in independent practice opportunities. Finally, redistribution of jobs will likely occur in favor of outpatient facilities, home health agencies, and nontraditional settings. This in turn will have an impact on allied health education, which will need to adapt to these types of reforms.

Effect of pH shifts on IgE-binding capacity and conformational structure of tropomyosin from short-neck clam (Ruditapes philippinarum).

PubMed

Lin, Haixin; Li, Zhenxing; Lin, Hong; Song, Yongna; Lv, Liangtao; Hao, Zina

2015-12-01

The aim of the present study was to assess pH-induced changes in conformational structures and potential allergenicity of tropomyosin from short-neck clams. As defined with circular dichroism (CD), an unfolded structure was found at pH values ranging from 2.0 to 5.0, followed by the loss of secondary structure at pH of 1.0. Correspondingly, surface hydrophobicity was reduced by 97.7% when pH was reduced from 7.0 to 1.0. Further indirect ELISA and dot-blot results of pH shifted tropomyosin showed that potential allergenicity correlated well with structural changes, as well as with SGF digestibility. Allergenicity decreased significantly with unfolding of the protein and was stable when surface hydrophobicity recovered back to neutral conditions. These results showed that conformational changes in tropomyosin induced by pH shifting significantly influenced the allergenicity of tropomyosin, and that the resulting changes occurred predominately in the acidic pH range. Copyright © 2015 Elsevier Ltd. All rights reserved.

Structural plasticity in the language system related to increased second language proficiency.

PubMed

Stein, Maria; Federspiel, Andrea; Koenig, Thomas; Wirth, Miranka; Strik, Werner; Wiest, Roland; Brandeis, Daniel; Dierks, Thomas

2012-04-01

While functional changes linked to second language learning have been subject to extensive investigation, the issue of learning-dependent structural plasticity in the fields of bilingualism and language comprehension has so far received less notice. In the present study we used voxel-based morphometry to monitor structural changes occurring within five months of second language learning. Native English-speaking exchange students learning German in Switzerland were examined once at the beginning of their stay and once about five months later, when their German language skills had significantly increased. We show that structural changes in the left inferior frontal gyrus are correlated with the increase in second language proficiency as measured by a paper-and-pencil language test. Contrary to the increase in proficiency and grey matter, the absolute values of grey matter density and second language proficiency did not correlate (neither on first nor on second measurement). This indicates that the individual amount of learning is reflected in brain structure changes, regardless of absolute proficiency. Copyright © 2010 Elsevier Srl. All rights reserved.

Permaculture in higher education: Teaching sustainability through action learning

NASA Astrophysics Data System (ADS)

Battisti, Bryce Thomas

This is a case study of the use of Action Learning (AL) theory to teach and confer degrees in Permaculture and other forms of sustainability at the newly formed Gaia University International (GUI). In Chapter Two I argue that GUI, as an institution of higher learning, is organized to provide support for learning. The goal of the university structure is to provide students, called Associates, with a vehicle for accumulation of credit towards a bachelor's degree. This organizational structure is necessary, but insufficient for AL because Associates need more than an organization to provide and coordinate their degree programs. In other words, just because the network of university structures are organized in ways that make AL possible and convenient, it does not necessarily follow that Action Learning will occur for any individual Associate. The support structures within GUI's degrees are discussed in Chapter Three. To a greater or lesser degree GUI provides support for personal learning among Associates as advisors and advisees with the goal of helping Associates complete and document the outcomes of world-change projects. The support structures are necessary, but not sufficient for AL because the personal learning process occurring for each Associate requires transformative reflection. Additionally, because Associates' attrition rate is very high, many Associates do not remain enrolled in GUI long enough to benefit from the support structures. At the simplest organizational level I discuss the reflection process conducted in the patterned interactions of assigned learning groups called Guilds (Chapter Four). These groups of Associates work to provide each other with the best possible environment for personal learning through reflection. As its Associates experience transformative reflection, GUI is able to help elevate the quality of world-change efforts in the Permaculture community. Provided the organizational and support structures are in place, this reflection process is both necessary and sufficient for AL. By this I mean that if transformative reflection is occurring in Guild meetings, and is supported by a system of advisors, reviewers and support people within a university organized to give credit for Action Learning, then Action Learning will occur for individual Associates.

Using real-time electron microscopy to explore the effects of transition-metal composition on the local thermal stability in charged Li xNi yMn zCo 1-y-zO 2 cathode materials

DOE PAGES

Hwang, Sooyeon; Kim, Seung Min; Bak, Seong -Min; ...

2015-05-08

In this study, we use in-situ transmission electron microcopy (TEM) to investigate the thermal decomposition that occurs at the surface of charged Li xNi yMn zCo 1-y-zO 2 (NMC) cathode materials of different composition (with y, z=0.8, 0.1 and 0.6, 0.2 and 0.4, 0.3), after they have been charged to their practical upper limit voltage (4.3V). By heating these materials inside the TEM, we are able to directly characterize near surface changes in both their electronic structure (using electron energy loss spectroscopy) and crystal structure and morphology (using electron diffraction and bright-field imaging). The most Ni-rich material (y, z =more » 0.8, 0.1) is found to be thermally unstable at significantly lower temperatures than the other compositions – this is manifested by changes in both the electronic structure and the onset of phase transitions at temperatures as low as 100°C. Electron energy loss spectroscopy indicates that the thermally induced reduction of Ni ions drives these changes, and that this is exacerbated by the presence of an additional redox reaction that occurs at 4.2V in the y, z = 0.8, 0.1 material. Exploration of individual particles shows that there are substantial variations in the onset temperatures and overall extent of these changes. Of the compositions studied, the composition of y, z = 0.6, 0.2 has the optimal combination of high energy density and reasonable thermal stability. The observations herein demonstrate that real time electron microscopy provide direct insight into the changes that occur in cathode materials with temperature, allowing optimization of different alloy concentrations to maximize overall performance.« less

IMAGING WITH MULTIMODAL ADAPTIVE-OPTICS OPTICAL COHERENCE TOMOGRAPHY IN MULTIPLE EVANESCENT WHITE DOT SYNDROME: THE STRUCTURE AND FUNCTIONAL RELATIONSHIP.

PubMed

Labriola, Leanne T; Legarreta, Andrew D; Legarreta, John E; Nadler, Zach; Gallagher, Denise; Hammer, Daniel X; Ferguson, R Daniel; Iftimia, Nicusor; Wollstein, Gadi; Schuman, Joel S

2016-01-01

To elucidate the location of pathological changes in multiple evanescent white dot syndrome (MEWDS) with the use of multimodal adaptive optics (AO) imaging. A 5-year observational case study of a 24-year-old female with recurrent MEWDS. Full examination included history, Snellen chart visual acuity, pupil assessment, intraocular pressures, slit lamp evaluation, dilated fundoscopic exam, imaging with Fourier-domain optical coherence tomography (FD-OCT), blue-light fundus autofluorescence (FAF), fundus photography, fluorescein angiography, and adaptive-optics optical coherence tomography. Three distinct acute episodes of MEWDS occurred during the period of follow-up. Fourier-domain optical coherence tomography and adaptive-optics imaging showed disturbance in the photoreceptor outer segments (PR OS) in the posterior pole with each flare. The degree of disturbance at the photoreceptor level corresponded to size and extent of the visual field changes. All findings were transient with delineation of the photoreceptor recovery from the outer edges of the lesion inward. Hyperautofluorescence was seen during acute flares. Increase in choroidal thickness did occur with each active flare but resolved. Although changes in the choroid and RPE can be observed in MEWDS, Fourier-domain optical coherence tomography, and multimodal adaptive optics imaging localized the visually significant changes seen in this disease at the level of the photoreceptors. These transient retinal changes specifically occur at the level of the inner segment ellipsoid and OS/RPE line. En face optical coherence tomography imaging provides a detailed, yet noninvasive method for following the convalescence of MEWDS and provides insight into the structural and functional relationship of this transient inflammatory retinal disease.

Effect of social networks and well-being on acute care needs.

PubMed

Sintonen, Sanna; Pehkonen, Aini

2014-01-01

The effect of social surroundings has been noted as an important component of the well-being of elderly people. A strong social network and strong and steady relationships are necessary for coping when illness or functional limitations occur in later life. Vulnerability can affect well-being and functioning particularly when sudden life changes occur. The objective of this study was to analyse how the determinants of social well-being affect individual acute care needs when sudden life changes occur. Empirical evidence was collected using a cross-sectional mail survey in Finland in January 2011 among individuals aged 55-79 years. The age-stratified random sample covered 3000 individuals, and the eventual response rate was 56% (1680). Complete responses were received from 1282 respondents (42.7%). The study focuses on the compactness of social networks, social disability, the stability of social relationships and the fear of loneliness as well as how these factors influence acute care needs. The measurement was based on a latent factor structure, and the key concepts were measured using two ordinal items. The results of the structural model suggest that the need for care is directly affected by social disability and the fear of loneliness. In addition, social disability is a determinant of the fear of loneliness and therefore plays an important role if sudden life changes occur. The compactness of social networks decreases social disability and partly diminishes the fear of loneliness and therefore has an indirect effect on the need for care. The stability of social relationships was influenced by the social networks and disability, but was an insignificant predictor of care needs. To conclude, social networks and well-being can decrease care needs, and supportive actions should be targeted to avoid loneliness and social isolation so that the informal network could be applied as an aspect of care-giving when acute life changes occur. © 2013 John Wiley & Sons Ltd.

Mechanical Factors and Bone Health: Effects of Weightlessness and Neurologic Injury

PubMed Central

Amin, Shreyasee

2014-01-01

Bone is a dynamic tissue with homeostasis governed by many factors. Among them, mechanical stimuli appear to be particularly critical for bone structure and strength. With removal of mechanical stimuli, a profound bone loss occurs, as best observed in the extreme examples following exposure to space flight or neurologic impairment. This review provides an overview of the changes in bone density and structure that occur during and after space flight as well as following neurologic injury from stroke and spinal cord injury. It also discusses the potential mechanisms through which mechanical stimuli are postulated to act on bone tissue. PMID:20425519

A Correlation Between Changes in Solar Luminosity and Differential Radius Measurements

NASA Technical Reports Server (NTRS)

Kroll, R. J.; Hill, H. A.; Beardsley, B. J.

1990-01-01

Solar luminosity variations occurring during solar cycle 21 can be attributed in large part to the presence of sunspots and faculae. Nevertheless, there remains a residual portion of the luminosity variation distinctly unaccounted for by these phenomena of solar activity. At the Santa Catalina Laboratory for Experimental Relativity by Astrometry (SCLERA), observations of the solar limb are capable of detecting changes in the solar limb darkening function by monitoring a quantity known as the differential radius. These observations are utilized in such a way that the effects of solar activity are minimized in order to reveal the more fundamental structure of the photosphere. The results of observations made during solar cycle 21 at various solar latitudes indicate that a measurable change did occur in the global photospheric limb darkening function. It is proposed that the residual luminosity change is associated in part with this change in limb darkening.

Cardiac changes in anorexia nervosa.

PubMed

Spaulding-Barclay, Michael A; Stern, Jessica; Mehler, Philip S

2016-04-01

Introduction Anorexia nervosa is an eating disorder, which is associated with many different medical complications as a result of the weight loss and malnutrition that characterise this illness. It has the highest mortality rate of any psychiatric disorder. A large portion of deaths are attributable to the cardiac abnormalities that ensue as a result of the malnutrition associated with anorexia nervosa. In this review, the cardiac complications of anorexia nervosa will be discussed. A comprehensive literature review on cardiac changes in anorexia nervosa was carried out. There are structural, functional, and rhythm-type changes that occur in patients with anorexia nervosa. These become progressively significant as ongoing weight loss occurs. Cardiac changes are inherent to anorexia nervosa and they become more life-threatening and serious as the anorexia nervosa becomes increasingly severe. Weight restoration and attention to these cardiac changes are crucial for a successful treatment outcome.

Root diseases in coniferous forests of the Inland West: potential implications of fuels treatments

Treesearch

Raini C. Rippy; Jane E. Stewart; Paul J. Zambino; Ned B. Klopfenstein; Joanne M. Tirocke; Mee-Sook Kim; Walter G. Thies

2005-01-01

After nearly 100 years of fire exclusion, introduced pests, and selective harvesting, a change in forest composition has occurred in many Inland West forests of North America. This change in forest structure has frequently been accompanied by increases in root diseases and/or an unprecedented buildup of fuels. Consequently, many forest managers are implementing plans...

Changes in barley (Hordeum vulgare L. subsp. vulgare) genetic diversity and structure in Jordan over a period of 31 years

USDA-ARS?s Scientific Manuscript database

In many regions of the world, the cultivation of landraces is still common, in particular in centres of crop diversity. Significant effort has been put into ex situ conservation of landraces but limited data exist on the changes in genetic diversity that occur over time in farmers’ fields. We assess...

Work and Change. Labor Market Adjustment Policies in a Competitive World.

ERIC Educational Resources Information Center

Committee for Economic Development, New York, NY. Research and Policy Committee.

The net effect on employment of structural changes now occurring in the United States will be determined by the actions that government, management, and labor take to create and support the conditions for new opportunity and to encourage people to move from old to new work. Many of the measures that need to be taken to ensure profitability involve…

Response to Elvira Panaiotidi, "The Nature of Paradigms and Paradigm Shifts in Music Education"

ERIC Educational Resources Information Center

Rodriguez, Carlos Xavier

2005-01-01

Elvira Panaiotidi has delivered a very useful and appealing paper on the topic of how the music education community decides it is time to change the way it thinks and acts. Her primary focus is whether the concept of "paradigms" proposed by Thomas Kuhn in The Structure of Scientific Revolutions reasonably explains how change occurs in…

Molecular accessibility in solvent swelled coal

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kispert, L.D.

1991-08-01

Research continued on the determination of pore size and number distribution changes after swelling the coal samples with various solvents. A paper has just been submitted to the journal Fuel on the Low temperature Swelling of Argonne Premium Coal samples using solvents of varying polarity. The variation in the shape of the pore was followed as a function of temperature and swelling solvent polarity. This change in pore structure was attributed to break-up of the hydrogen bonding network in coal by polar solvents. The modification in pore shape from spherical to cylindrical was attributed to anisotropy in hydrogen bond densities.more » A copy of this paper has been attached to this report. Wojciech Sady has determine the structural changes in the pores that occur when APCS coal is dehydrated prior to swelling with polar solvents. These changes are different from those that occur in the absence of prior dehydration. He has also completed a study on the variation in the hydrogen bonding character of the pore wall as the coals are swelled with various polar solvents. A statistical analysis of the data is currently underway to determine important trends in his data. 9 refs.« less

Structural and biochemical changes in dermis of sea cucumber (Stichopus japonicus) during autolysis in response to cutting the body wall.

PubMed

Liu, Yu-Xin; Zhou, Da-Yong; Liu, Zi-Qiang; Lu, Ting; Song, Liang; Li, Dong-Mei; Dong, Xiu-Ping; Qi, Hang; Zhu, Bei-Wei; Shahidi, Fereidoon

2018-02-01

The autolysis of sea cucumber body wall is caused by endogenous proteolysis of its structural elements. However, changes in collagen fibrils, collagen fibres and microfibrils, the major structural elements in sea cucumber body wall during autolysis are less clear. Autolysis of sea cucumber (S. japonicus) was induced by cutting the body wall, and the structural and biochemical changes in its dermis were investigated using electron microscopy, differential scanning calorimetry, infrared spectroscopy, electrophoresis, and chemical analysis. During autolysis, both collagen fibres and microfibrils gradually degraded. In contrast, damage to microfibrils was more pronounced. Upon massive autolysis, collagen fibres disaggregated into collagen fibril bundles and individual fibrils due to the fracture of interfibrillar bridges. Meanwhile, excessive unfolding of collagen fibrils occurred. However, there was only slight damage to collagen monomers. Therefore, structural damage in collagen fibres, collagen fibrils and microfibrils rather than monomeric collagen accounts for autolysis of S. japonicus dermis. Copyright © 2017 Elsevier Ltd. All rights reserved.

Biological effects of weightlessness and clinostatic conditions registered in cells of root meristem and cap of higher plants

NASA Astrophysics Data System (ADS)

Sytnik, K. M.; Kordyum, E. L.; Belyavskaya, N. A.; Nedukha, E. M.; Tarasenko, V. A.

Research in cellular reproduction, differentiation and vital activity, i.e. processes underlying the development and functioning of organisms, plants included, is essential for solving fundamental and applied problems of space biology. Detailed anatomical analysis of roots of higher plants grown on board the Salyut 6 orbital research station show that under conditions of weightlessness for defined duration mitosis, cytokinesis and tissue differentiation in plant vegetative organs occur essentially normally. At the same time, certain rearrangements in the structural organization of cellular organelles - mainly the plastid apparatus, mitochondria, Golgi apparatus and nucleus - are established in the root meristem and cap of the experimental plants. This is evidence for considerable changes in cellular metabolism. The structural changes in the subcellular level arising under spaceflight conditions are partially absent in clinostat experiments designed to simulate weightlessness. Various clinostatic conditions have different influences on the cell structural and functional organization than does space flight. It is suggested that alterations of cellular metabolism under weightlessness and clinostatic conditions occur within existing genetic programs.

Change of the structure and the digestibility of myofibrillar proteins in Nanjing dry-cured duck during processing.

PubMed

Du, Xiaojing; Sun, Yangying; Pan, Daodong; Wang, Ying; Ou, Changrong; Cao, Jinxuan

2018-06-01

To investigate the change of bioavailability and structure of myofibrillar proteins during Nanjing dry-cured duck processing, carbonyl content, sulfhydryl (SH) group, disulfide (SS) group, sodium dodecyl sulfate polyacrylamide gel electrophoresis, surface hydrophobicity, secondary structures and in vitro digestibility were determined. During processing, carbonyl content and surface hydrophobicity increased; SH turned into SS group; α-helix turned into β-sheet and random coil fractions. Protein degradation occurred during dry-curing and drying-ripening stages. The in vitro digestibility of pepsin and pancreatic proteases increased during the salt curing stage and decreased during the drying-ripening stage. The increase of digestibility could be attributed to the mild oxidation, degradation and unfolding of proteins while the decrease of digestibility was related to the intensive oxidation and aggregation of proteins. Protein degradation was not a main factor of digestibility during the drying-ripening stage. Results demonstrated that the bioavailability loss of myofibrillar proteins in Nanjing dry-cured duck occurred during the stage of drying-ripening instead of curing. © 2017 Society of Chemical Industry. © 2017 Society of Chemical Industry.

A structural approach in the study of bones: fossil and burnt bones at nanosize scale

NASA Astrophysics Data System (ADS)

Piga, Giampaolo; Baró, Maria Dolors; Escobal, Irati Golvano; Gonçalves, David; Makhoul, Calil; Amarante, Ana; Malgosa, Assumpció; Enzo, Stefano; Garroni, Sebastiano

2016-12-01

We review the different factors affecting significantly mineral structure and composition of bones. Particularly, it is assessed that micro-nanostructural and chemical properties of skeleton bones change drastically during burning; the micro- and nanostructural changes attending those phases manifest themselves, amongst others, in observable alterations to the bones colour, morphology, microstructure, mechanical strength and crystallinity. Intense changes involving the structure and chemical composition of bones also occur during the fossilization process. Bioapatite material is contaminated by an heavy fluorination process which, on a long-time scale reduces sensibly the volume of the original unit cell, mainly the a-axis of the hexagonal P63/m space group. Moreover, the bioapatite suffers to a varying degree of extent by phase contamination from the nearby environment, to the point that rarely a fluorapatite single phase may be found in fossil bones here examined. TEM images supply precise and localized information, on apatite crystal shape and dimension, and on different processes that occur during thermal processes or fossilization of ancient bone, complementary to that given by X-ray diffraction and Attenuated Total Reflection Infrared spectroscopy. We are presenting a synthesis of XRD, ATR-IR and TEM results on the nanostructure of various modern, burned and palaeontological bones.

Molecular Dynamics based on a Generalized Born solvation model: application to protein folding

NASA Astrophysics Data System (ADS)

Onufriev, Alexey

2004-03-01

An accurate description of the aqueous environment is essential for realistic biomolecular simulations, but may become very expensive computationally. We have developed a version of the Generalized Born model suitable for describing large conformational changes in macromolecules. The model represents the solvent implicitly as continuum with the dielectric properties of water, and include charge screening effects of salt. The computational cost associated with the use of this model in Molecular Dynamics simulations is generally considerably smaller than the cost of representing water explicitly. Also, compared to traditional Molecular Dynamics simulations based on explicit water representation, conformational changes occur much faster in implicit solvation environment due to the absence of viscosity. The combined speed-up allow one to probe conformational changes that occur on much longer effective time-scales. We apply the model to folding of a 46-residue three helix bundle protein (residues 10-55 of protein A, PDB ID 1BDD). Starting from an unfolded structure at 450 K, the protein folds to the lowest energy state in 6 ns of simulation time, which takes about a day on a 16 processor SGI machine. The predicted structure differs from the native one by 2.4 A (backbone RMSD). Analysis of the structures seen on the folding pathway reveals details of the folding process unavailable form experiment.

Tipping Points in Resource Abundance Drive Irreversible Changes in Community Structure.

PubMed

Haney, Seth D; Siepielski, Adam M

2018-05-01

Global climate change has made what were seemingly extraordinary environmental conditions, such as prolonged droughts, commonplace. One consequence of extreme environmental change is concomitant changes in resource abundance. How will such extreme resource changes impact biodiversity? We developed a trait-based consumer-resource model to examine how resource abundance affects the potential for adaptive evolution and coexistence among competitors. We found that moderate changes in resource abundance have little effect on trait evolution. However, when resource scarcities were sufficiently extreme, a critical transition-a tipping point-occurred, which caused consumer traits to diverge and restructured the community in a way that outlasted the scarcity. Therefore, even though traits can evolve in response to minor resource fluctuations, large environmental shifts may be necessary for producing long-lasting impacts on community structure. These results may also help to illuminate patterns of stasis frequently observed in nature, despite the considerable evidence demonstrating rapid evolutionary change.

Ecological opportunity and the evolution of habitat preferences in an arid-zone bird: implications for speciation in a climate-modified landscape

PubMed Central

Norman, Janette A.; Christidis, Les

2016-01-01

Bioclimatic models are widely used to investigate the impacts of climate change on species distributions. Range shifts are expected to occur as species track their current climate niche yet the potential for exploitation of new ecological opportunities that may arise as ecosystems and communities remodel is rarely considered. Here we show that grasswrens of the Amytornis textilis-modestus complex responded to new ecological opportunities in Australia’s arid biome through shifts in habitat preference following the development of chenopod shrublands during the late Plio-Pleistocene. We find evidence of spatially explicit responses to climatically driven landscape changes including changes in niche width and patterns of population growth. Conservation of structural and functional aspects of the ancestral niche appear to have facilitated recent habitat shifts, while demographic responses to late Pleistocene climate change provide evidence for the greater resilience of populations inhabiting the recently evolved chenopod shrubland communities. Similar responses could occur under future climate change in species exposed to novel ecological conditions, or those already occupying spatially heterogeneous landscapes. Mechanistic models that consider structural and functional aspects of the niche along with regional hydro-dynamics may be better predictors of future climate responses in Australia’s arid biome than bioclimatic models alone. PMID:26787111

Synthesis of dynamic phase profile by the correlation technique for spatial control of optical beams in multiplexing and switching

NASA Astrophysics Data System (ADS)

Bugaychuk, Svitlana A.; Gnatovskyy, Vladimir O.; Sidorenko, Andrey V.; Pryadko, Igor I.; Negriyko, Anatoliy M.

2015-11-01

New approach for the correlation technique, which is based on multiple periodic structures to create a controllable angular spectrum, is proposed and investigated both theoretically and experimentally. The transformation of an initial laser beam occurs due to the actions of consecutive phase periodic structures, which may differ by their parameters. Then, after the Fourier transformation of a complex diffraction field, the output diffraction orders will be changed both by their intensities and by their spatial position. The controllable change of output angular spectrum is carried out by a simple control of the parameters of the periodic structures. We investigate several simple examples of such management.

Skeletal responses to spaceflight

NASA Technical Reports Server (NTRS)

Morey-Holton, Emily; Arnaud, Sara B.

1991-01-01

The role of gravity in the determination of bone structure is elucidated by observations in adult humans and juvenile animals during spaceflight. The primary response of bone tissue to microgravity is at the interface of the mineral and matrix in the process of biomineralization. This response is manifested by demineralization or retarded growth in some regions of the skeleton and hypermineralization in others. The most pronounced effects are seen in the heelbone and skull, the most distally located bones relative to the heart. Ground based flight simulation models that focus on changes in bone structure at the molecular, organ, and whole body levels are described and compared to flight results. On Earth, the morphologic and compositional changes in the unloaded bones are very similar to changes during flight; however, the ground based changes appear to be more transient. In addition, a redistribution of bone mineral in gravity-dependent bones occurs both in space and during head down positioning on Earth. Longitudinal data provided considerable information on the influence of endocrine and muscular changes on bone structure after unloading.

Normal age-related brain morphometric changes: nonuniformity across cortical thickness, surface area and gray matter volume?

PubMed

Lemaitre, Herve; Goldman, Aaron L; Sambataro, Fabio; Verchinski, Beth A; Meyer-Lindenberg, Andreas; Weinberger, Daniel R; Mattay, Venkata S

2012-03-01

Normal aging is accompanied by global as well as regional structural changes. While these age-related changes in gray matter volume have been extensively studied, less has been done using newer morphological indexes, such as cortical thickness and surface area. To this end, we analyzed structural images of 216 healthy volunteers, ranging from 18 to 87 years of age, using a surface-based automated parcellation approach. Linear regressions of age revealed a concomitant global age-related reduction in cortical thickness, surface area and volume. Cortical thickness and volume collectively confirmed the vulnerability of the prefrontal cortex, whereas in other cortical regions, such as in the parietal cortex, thickness was the only measure sensitive to the pronounced age-related atrophy. No cortical regions showed more surface area reduction than the global average. The distinction between these morphological measures may provide valuable information to dissect age-related structural changes of the brain, with each of these indexes probably reflecting specific histological changes occurring during aging. Published by Elsevier Inc.

Structures and properties of alumina-based ceramic for reconstructive oncology

NASA Astrophysics Data System (ADS)

Grigoriev, M. V.; Kulkov, S. N.

2016-08-01

The microstructure of alumina ceramics based on powders with a varying grain size has been investigated. Both commercial alumina powders and those fabricated by denitration of aluminum salts in high-frequency discharge plasma were used. It is shown that the variation of the sintering temperature and morphology of the initial powders of the particles leads to a change of the pore structure of ceramics from pore isolated clusters to a structure consisting of a ceramic skeleton and a large pore space. Changing the type of pore structure occurs at about 50% of porosity. The ceramic pore size distribution is bimodal. Dependencies final density vs initial density are linear; at the same time with increasing temperature, inclination of changes from positive to negative, indicating the change of sealing mechanisms. Extrapolation of these curves showed that they intersect with the values of density of about 2 g/cm3, which indicates the possibility of producing non-shrink ceramics. It is shown that the strength increases with increasing nanocrystalline alumina content in powder mixture. A change in the character the pore structure is accompanied by a sharp decrease in strength, which corresponds to the percolation transition in ceramics. These results showed that it is possible to obtain ceramic materials with the structure and properties similar to natural bone.

Brain Mapping of drug addiction in witdrawal condition based P300 Signals

NASA Astrophysics Data System (ADS)

Turnip, Arjon; Esti Kusumandari, Dwi; Hidayat, Teddy

2018-04-01

Drug abuse for a long time will slowly cause changes in brain structure and performance. These changes tend to occur in the front of the brain which is directly interfere the concentration and the decision-making process. In this study an experiment involving 10 drug users was performed. The process of recording data with EEG system is conducted during craving condition and 1 hour after taking methadone. From brain mapping results obtained that brain activity tend to occur in the upper layer of the brain during craving conditions and tend to be in the midle layer of the brain after one hour of taking methadone.

Deactivation of Pd particles supported on Nb 2O 5/Cu 3Au(1 0 0): SFG and TPD studies from UHV to 100 mbar

NASA Astrophysics Data System (ADS)

Höbel, Frank; Bandara, Athula; Rupprechter, Günther; Freund, Hans-Joachim

2006-02-01

Structural changes that occur on Pd-Nb 2O 5/Cu 3Au(1 0 0) model catalysts upon thermal annealing were followed by sum frequency generation (SFG) and temperature-programmed desorption (TPD) using CO as probe molecule. SFG experiments were performed both under ultrahigh vacuum and mbar pressure. Heating the catalyst to temperatures above 300 K lead to an irreversible 50% decrease in the CO adsorption capacity and modified the remaining adsorption sites. Alterations of the phase between resonant and non-resonant SFG signals upon annealing indicate a change in the electronic structure of the surface, which excludes Pd sintering or migration of Nb 2O 5 over Pd particles to cause the observed effect and rather suggests the formation of "mixed Pd-NbO x" sites. The same changes in surface properties also occur during CO hydrogenation at 1 bar and high temperature, pointing to an involvement of "mixed Pd-NbO x" sites in catalytic reactions.

Channelization in porous media driven by erosion and deposition.

PubMed

Jäger, R; Mendoza, M; Herrmann, H J

2017-01-01

We develop and validate a new model to study simultaneous erosion and deposition in three-dimensional porous media. We study the changes of the porous structure induced by the deposition and erosion of matter on the solid surface and find that when both processes are active, channelization in the porous structure always occurs. The channels can be stable or only temporary depending mainly on the driving mechanism. Whereas a fluid driven by a constant pressure drop in general does not form steady channels, imposing a constant flux always produces stable channels within the porous structure. Furthermore we investigate how changes of the local deposition and erosion properties affect the final state of the porous structure, finding that the larger the range of wall shear stress for which there is neither erosion nor deposition, the more steady channels are formed in the structure.

Clinorotation [correction of Clinoratation] effects on the structural-functional response in potato minitubers.

PubMed

Nedukha, O; Kordyum, E; Ovrutska, I; Martyn, G; Shnyukova, E

2001-07-01

It is established that high plant growth and development in microgravity occurred normal. However, the change of plant growth rate is accompanied by the change of carbohydrate metabolism in photosynthesized cells (Kordyum, 1997). The decrease of starch grain size in chloroplasts and the decrease of content cellulose in cell wall were revealed (Sytnik et al., 1984; Nedukha, 1996). The change carbohydrate metabolism in photosynthesized organs could influence on the growth of underground organs and content of storage carbohydrates in these organs. Therefore, the aim of our study was to investigate the long-term clinorotation influence on the formation, structure of potato minitubers and content of starch and sugars in minitubers.

Structural changes of homodimers in the PDB.

PubMed

Koike, Ryotaro; Amemiya, Takayuki; Horii, Tatsuya; Ota, Motonori

2018-04-01

Protein complexes are involved in various biological phenomena. These complexes are intrinsically flexible, and structural changes are essential to their functions. To perform a large-scale automated analysis of the structural changes of complexes, we combined two original methods. An application, SCPC, compares two structures of protein complexes and decides the match of binding mode. Another application, Motion Tree, identifies rigid-body motions in various sizes and magnitude from the two structural complexes with the same binding mode. This approach was applied to all available homodimers in the Protein Data Bank (PDB). We defined two complex-specific motions: interface motion and subunit-spanning motion. In the former, each subunit of a complex constitutes a rigid body, and the relative movement between subunits occurs at the interface. In the latter, structural parts from distinct subunits constitute a rigid body, providing the relative movement spanning subunits. All structural changes were classified and examined. It was revealed that the complex-specific motions were common in the homodimers, detected in around 40% of families. The dimeric interfaces were likely to be small and flat for interface motion, while large and rugged for subunit-spanning motion. Interface motion was accompanied by a drastic change in contacts at the interface, while the change in the subunit-spanning motion was moderate. These results indicate that the interface properties of homodimers correlated with the type of complex-specific motion. The study demonstrates that the pipeline of SCPC and Motion Tree is useful for the massive analysis of structural change of protein complexes. Copyright © 2017 Elsevier Inc. All rights reserved.

Ocean acidification impacts mussel control on biomineralisation

PubMed Central

Fitzer, Susan C.; Phoenix, Vernon R.; Cusack, Maggie; Kamenos, Nicholas A.

2014-01-01

Ocean acidification is altering the oceanic carbonate saturation state and threatening the survival of marine calcifying organisms. Production of their calcium carbonate exoskeletons is dependent not only on the environmental seawater carbonate chemistry but also the ability to produce biominerals through proteins. We present shell growth and structural responses by the economically important marine calcifier Mytilus edulis to ocean acidification scenarios (380, 550, 750, 1000 µatm pCO2). After six months of incubation at 750 µatm pCO2, reduced carbonic anhydrase protein activity and shell growth occurs in M. edulis. Beyond that, at 1000 µatm pCO2, biomineralisation continued but with compensated metabolism of proteins and increased calcite growth. Mussel growth occurs at a cost to the structural integrity of the shell due to structural disorientation of calcite crystals. This loss of structural integrity could impact mussel shell strength and reduce protection from predators and changing environments. PMID:25163895

Ocean acidification impacts mussel control on biomineralisation.

PubMed

Fitzer, Susan C; Phoenix, Vernon R; Cusack, Maggie; Kamenos, Nicholas A

2014-08-28

Ocean acidification is altering the oceanic carbonate saturation state and threatening the survival of marine calcifying organisms. Production of their calcium carbonate exoskeletons is dependent not only on the environmental seawater carbonate chemistry but also the ability to produce biominerals through proteins. We present shell growth and structural responses by the economically important marine calcifier Mytilus edulis to ocean acidification scenarios (380, 550, 750, 1000 µatm pCO2). After six months of incubation at 750 µatm pCO2, reduced carbonic anhydrase protein activity and shell growth occurs in M. edulis. Beyond that, at 1000 µatm pCO2, biomineralisation continued but with compensated metabolism of proteins and increased calcite growth. Mussel growth occurs at a cost to the structural integrity of the shell due to structural disorientation of calcite crystals. This loss of structural integrity could impact mussel shell strength and reduce protection from predators and changing environments.

Culture, Structure and Leadership Impacts on Gender Inclusion in the Security Sector

DTIC Science & Technology

2017-09-01

culture were outcomes of structural reform. A guided evolution in security sector culture occurred following persistent social pressure, compliance...brought about a change in national and organizational culture to address socially complex issues. As the orchestrators of large successful corporate...challenges them (Jolly 2002). In the process, we are influenced and shaped as we interact with local, national and international information. Likewise, we

The Influence of Financial, Human and Social Capital on Japanese Men's and Women's Health in Single- and Two-Parent Family Structures

ERIC Educational Resources Information Center

Bassani, Cherylynn

2008-01-01

Large-scale demographic changes have been occurring in Japan over the last few decades. During this time, the proportion of two-parent (nuclear) and single-parent families have doubled. Despite this rapid increase, the health of individuals in these family structures have received limited attention, as the focus has been directed towards the…

Polymorphism in Energetic Materials

DTIC Science & Technology

2008-01-01

2Department of Chemistry, Howard University Polymorphism often occurs in energetic materials. Differences in the forms range from conformational changes in...these two areas. rayMond J. ButchEr is a professor of inorganic and structural chemistry at Howard University , Washington, DC. He has worked at Howard ... University since 1977 and has been associated with the NRL Laboratory for Structure of Matter since 1989 (primarily during the summer months as an

Anisotropic Morphological Changes in Goethite during Fe(2+)-Catalyzed Recrystallization.

PubMed

Joshi, Prachi; Gorski, Christopher A

2016-07-19

When goethite is exposed to aqueous Fe(2+), rapid and extensive Fe atom exchange can occur between solid-phase Fe(3+) and aqueous Fe(2+) in a process referred to as Fe(2+)-catalyzed recrystallization. This process can lead to the structural incorporation or release of trace elements, which has important implications for contaminant remediation and nutrient biogeochemical cycling. Prior work found that the process did not cause major changes to the goethite structure or morphology. Here, we further investigated if and how goethite morphology and aggregation behavior changed temporally during Fe(2+)-catalyzed recrystallization. On the basis of existing literature, we hypothesized that Fe(2+)-catalyzed recrystallization of goethite would not result in changes to individual particle morphology or interparticle interactions. To test this, we reacted nanoparticulate goethite with aqueous Fe(2+) at pH 7.5 over 30 days and used transmission electron microscopy (TEM), cryogenic TEM, and (55)Fe as an isotope tracer to observe changes in particle dimensions, aggregation, and isotopic composition over time. Over the course of 30 days, the goethite particles substantially recrystallized, and the particle dimensions changed anisotropically, resulting in a preferential increase in the mean particle width. The temporal changes in goethite morphology could not be completely explained by a single mineral-transformation mechanism but rather indicated that multiple transformation mechanisms occurred concurrently. Collectively, these results demonstrate that the morphology of goethite nanoparticles does change during recrystallization, which is an important step toward identifying the driving force(s) of recrystallization.

Dislocation-induced Charges in Quantum Dots: Step Alignment and Radiative Emission

NASA Technical Reports Server (NTRS)

Leon, R.; Okuno, J.; Lawton, R.; Stevens-Kalceff, M.; Phillips, M.; Zou, J.; Cockayne, D.; Lobo, C.

1999-01-01

A transition between two types of step alignment was observed in a multilayered InGaAs/GaAs quantum-dot (QD) structure. A change to larger QD sizes in smaller concentrations occurred after formation of a dislocation array.

Integrated Modeling for Watershed Ecosystem Services Assessment and Forecasting

EPA Science Inventory

Regional scale watershed management decisions must be informed by the science-based relationship between anthropogenic activities on the landscape and the change in ecosystem structure, function, and services that occur as a result. We applied process-based models that represent...

Timber resources of East Oklahoma

Treesearch

Richard A. Birdsey; Dennis M. May

1988-01-01

Presents the principal findings of the fifth forest survey of east Oklahoma and the changes that have occurred since earlier surveys. Trends in forest area, ownership, forest type, stand structure, stocking, timber volume, growth, removals, mortality, management opportunities, and timber products output are discussed.

Forest resources of Mississippi - 1994

Treesearch

James F. Rosson

2001-01-01

The principal findings of the seventh forest survey of Mississippi and changes that have occurred since the previous survey are presented. Topics examined include forest area, ownership, forest-type groups, stand structure, basal area, timber volume, growth, removals, mortality, harvesting, and management activity.

Forest resources of Arkansas, 1995

Treesearch

James F. Rosson

2002-01-01

The principal findings of the seventh forest survey of Arkansas and changes that have occurred since the previous survey are presented. Topics examined include forest area, ownership, forest-type groups, stand structure, basal area, timber volume, growth, removals, mortality, harvesting, and management activity.

Structure, magnetic, and electrical properties of Zn1-xMnxO material

NASA Astrophysics Data System (ADS)

Sebayang, P.; Hulu, S. F.; Nasruddin, Aryanto, D.; Kurniawan, C.; Subhan, A.; Sudiro, T.; Ginting, M.

2017-07-01

ZnO and MnO2 powder were synthesized using solid state reaction method to produce Zn1-xMnxO materials. Effect of dopant concentrations at the material of Zn1-xMnxO (x = 0.015, 0.02, 0.025) to the change of crystal structure, electrical and magnetic properties was studied. The X-ray diffraction (XRD) result of the samples that were doped with Mn showed a hexagonal wurtzite polycrystalline structure. The addition of Mn dopant resulting the decrease of lattice parameters and peaks intensity. The significant increase of the peak intensity occurred at x = 0.02, which also indicated an increase in the crystal quality of ZnO. The change of the ZnO structure affected the electrical and magnetic properties of the samples.

Resonance between a Prolate and a Superprolate Structure of the Er Nucleus.

PubMed

Pauling, L; Blethen, J

1974-07-01

Observed energy levels of (162)Er from the normal state J = 0 to the excited rotational state J = 18 correspond to values of the moment of inertia and rotational frequency that indicate that a pronounced change in structure occurs at about J = 14. It is shown that the observed values agree well with the values calculated on the assumption that there is resonance between a more stable prolate structure with a core of two spherons and a less stable superprolate structure with a core of three spherons in line.

The Incorporation of Ribonucleotides Induces Structural and Conformational Changes in DNA.

PubMed

Meroni, Alice; Mentegari, Elisa; Crespan, Emmanuele; Muzi-Falconi, Marco; Lazzaro, Federico; Podestà, Alessandro

2017-10-03

Ribonucleotide incorporation is the most common error occurring during DNA replication. Cells have hence developed mechanisms to remove ribonucleotides from the genome and restore its integrity. Indeed, the persistence of ribonucleotides into DNA leads to severe consequences, such as genome instability and replication stress. Thus, it becomes important to understand the effects of ribonucleotides incorporation, starting from their impact on DNA structure and conformation. Here we present a systematic study of the effects of ribonucleotide incorporation into DNA molecules. We have developed, to our knowledge, a new method to efficiently synthesize long DNA molecules (hundreds of basepairs) containing ribonucleotides, which is based on a modified protocol for the polymerase chain reaction. By means of atomic force microscopy, we could therefore investigate the changes, upon ribonucleotide incorporation, of the structural and conformational properties of numerous DNA populations at the single-molecule level. Specifically, we characterized the scaling of the contour length with the number of basepairs and the scaling of the end-to-end distance with the curvilinear distance, the bending angle distribution, and the persistence length. Our results revealed that ribonucleotides affect DNA structure and conformation on scales that go well beyond the typical dimension of the single ribonucleotide. In particular, the presence of ribonucleotides induces a systematic shortening of the molecules, together with a decrease of the persistence length. Such structural changes are also likely to occur in vivo, where they could directly affect the downstream DNA transactions, as well as interfere with protein binding and recognition. Copyright © 2017 Biophysical Society. Published by Elsevier Inc. All rights reserved.

High-Density Amorphous Ice, the Frost on Interstellar Grains

NASA Technical Reports Server (NTRS)

Jenniskens, P.; Blake, D. F.; Wilson, M. A.; Pohorille, A.

1995-01-01

Most water ice in the universe is in a form which does not occur naturally on Earth and of which only minimal amounts have been made in the laboratory. We have encountered this 'high-density amorphous ice' in electron diffraction experiments of low-temperature (T less than 30 K) vapor-deposited water and have subsequently modeled its structure using molecular dynamics simulations. The characteristic feature of high-density amorphous ice is the presence of 'interstitial' oxygen pair distances between 3 and 4 A. However, we find that the structure is best described as a collapsed lattice of the more familiar low-density amorphous form. These distortions are frozen in at temperatures below 38 K because, we propose, it requires the breaking of one hydrogen bond, on average, per molecule to relieve the strain and to restructure the lattice to that of low-density amorphous ice. Several features of astrophysical ice analogs studied in laboratory experiments are readily explained by the structural transition from high-density amorphous ice into low-density amorphous ice. Changes in the shape of the 3.07 gm water band, trapping efficiency of CO, CO loss, changes in the CO band structure, and the recombination of radicals induced by low-temperature UV photolysis all covary with structural changes that occur in the ice during this amorphous to amorphous transition. While the 3.07 micrometers ice band in various astronomical environments can be modeled with spectra of simple mixtures of amorphous and crystalline forms, the contribution of the high-density amorphous form nearly always dominates.

Human and natural influences on the changing thermal structure of the atmosphere

PubMed Central

Santer, Benjamin D.; Painter, Jeffrey F.; Bonfils, Céline; Mears, Carl A.; Solomon, Susan; Wigley, Tom M. L.; Gleckler, Peter J.; Schmidt, Gavin A.; Doutriaux, Charles; Gillett, Nathan P.; Taylor, Karl E.; Thorne, Peter W.; Wentz, Frank J.

2013-01-01

Since the late 1970s, satellite-based instruments have monitored global changes in atmospheric temperature. These measurements reveal multidecadal tropospheric warming and stratospheric cooling, punctuated by short-term volcanic signals of reverse sign. Similar long- and short-term temperature signals occur in model simulations driven by human-caused changes in atmospheric composition and natural variations in volcanic aerosols. Most previous comparisons of modeled and observed atmospheric temperature changes have used results from individual models and individual observational records. In contrast, we rely on a large multimodel archive and multiple observational datasets. We show that a human-caused latitude/altitude pattern of atmospheric temperature change can be identified with high statistical confidence in satellite data. Results are robust to current uncertainties in models and observations. Virtually all previous research in this area has attempted to discriminate an anthropogenic signal from internal variability. Here, we present evidence that a human-caused signal can also be identified relative to the larger “total” natural variability arising from sources internal to the climate system, solar irradiance changes, and volcanic forcing. Consistent signal identification occurs because both internal and total natural variability (as simulated by state-of-the-art models) cannot produce sustained global-scale tropospheric warming and stratospheric cooling. Our results provide clear evidence for a discernible human influence on the thermal structure of the atmosphere. PMID:24043789

Predisposing factors for atrial fibrillation in the elderly

PubMed Central

Wasmer, Kristina; Eckardt, Lars; Breithardt, Günter

2017-01-01

Atrial fibrillation (AF) in the elderly occurs as a consequence of cardiovascular aging and an age related increase of comorbidity. Several predisposing factors for AF have been identified for the overall AF population. Most of them, cardiovascular disease in particular, play a role in younger and older patients. The longer time period during which these risk factors can cause structural changes that ultimately lead to AF may, at least in part, explain the association between age and AF. In addition, less well defined age-related changes in cellular electrophysiologic properties and structure predispose to AF in the elderly. PMID:28592961

Pressure-induced structural change in MgSiO3 glass at pressures near the Earth's core–mantle boundary

NASA Astrophysics Data System (ADS)

Kono, Yoshio; Shibazaki, Yuki; Kenney-Benson, Curtis; Wang, Yanbin; Shen, Guoyin

2018-02-01

Knowledge of the structure and properties of silicate magma under extreme pressure plays an important role in understanding the nature and evolution of Earth’s deep interior. Here we report the structure of MgSiO3 glass, considered an analog of silicate melts, up to 111 GPa. The first (r1) and second (r2) neighbor distances in the pair distribution function change rapidly, with r1 increasing and r2 decreasing with pressure. At 53–62 GPa, the observed r1 and r2 distances are similar to the Si-O and Si-Si distances, respectively, of crystalline MgSiO3 akimotoite with edge-sharing SiO6 structural motifs. Above 62 GPa, r1 decreases, and r2 remains constant, with increasing pressure until 88 GPa. Above this pressure, r1 remains more or less constant, and r2 begins decreasing again. These observations suggest an ultrahigh-pressure structural change around 88 GPa. The structure above 88 GPa is interpreted as having the closest edge-shared SiO6 structural motifs similar to those of the crystalline postperovskite, with densely packed oxygen atoms. The pressure of the structural change is broadly consistent with or slightly lower than that of the bridgmanite-to-postperovskite transition in crystalline MgSiO3. These results suggest that a structural change may occur in MgSiO3 melt under pressure conditions corresponding to the deep lower mantle.

Simple shearing flow of dry soap foams with tetrahedrally close-packed structure

DOE Office of Scientific and Technical Information (OSTI.GOV)

Reinelt, Douglas A.; Kraynik, Andrew M.

2000-05-01

The microrheology of dry soap foams subjected to quasistatic, simple shearing flow is analyzed. Two different monodisperse foams with tetrahedrally close-packed (TCP) structure are examined: Weaire-Phelan (A15) and Friauf-Laves (C15). The elastic-plastic response is evaluated by using the Surface Evolver to calculate foam structures that minimize total surface area at each value of strain. The foam geometry and macroscopic stress are piecewise continuous functions of strain. The stress scales as T/V{sup 1/3}, where T is surface tension and V is cell volume. Each discontinuity corresponds to large changes in foam geometry and topology that restore equilibrium to unstable configurations thatmore » violate Plateau's laws. The instabilities occur when the length of an edge on a polyhedral foam cell vanishes. The length can tend to zero smoothly or abruptly with strain. The abrupt case occurs when a small increase in strain changes the energy profile in the neighborhood of a foam structure from a local minimum to a saddle point, which can lead to symmetry-breaking bifurcations. In general, the new structure associated with each stable solution branch results from an avalanche of local topology changes called T1 transitions. Each T1 cascade produces different cell neighbors, reduces surface energy, and provides an irreversible, film-level mechanism for plastic yield behavior. Stress-strain curves and average stresses are evaluated by examining foam orientations that admit strain-periodic behavior. For some orientations, the deformation cycle includes Kelvin cells instead of the original TCP structure; but the foam does not remain perfectly ordered. Bifurcations during subsequent T1 cascades lead to disorder and can even cause strain localization. (c) 2000 Society of Rheology.« less

The Call of the Sirens? The Influence of Gender in the Decision To Choose Teaching as a Career Change.

ERIC Educational Resources Information Center

Freidus, Helen

Social feminists insist on the relevance of personal experience and believe that, for changes to occur, it is essential to understand the dynamics of how and why gender roles are perpetuated. Social feminists view the career course of second-career teachers as vulnerable to the covert structures and curriculum of the schools. The social feminist…

[Experiments using rats on Kosmos biosatellites: morphologic and biochemical studies].

PubMed

Il'in, E A; Kaplanskiĭ, A S; Savina, E A

1989-01-01

Results of morphological and biochemical investigations of rats flown on Cosmos biosatellites are discussed. It is emphasized that most changes occurring during exposure to microgravity are directly or indirectly related to lower musculoskeletal loads which in turn produce deconditioning of different physiological systems and organism as a whole. It is concluded that this deconditioning is associated with both metabolic and structural changes.

A cellular backline: specialization of host membranes for defence.

PubMed

Faulkner, Christine

2015-03-01

In plant-pathogen interactions, the host plasma membrane serves as a defence front for pathogens that invade from the extracellular environment. As such, the lipid bilayer acts as a scaffold that targets and delivers defence responses to the site of attack. During pathogen infection, numerous changes in plasma membrane composition, organization, and structure occur. There is increasing evidence that this facilitates the execution of a variety of responses, highlighting the regulatory role membranes play in cellular responses. Membrane microdomains such as lipid rafts are hypothesized to create signalling platforms for receptor signalling in response to pathogen perception and for callose synthesis. Further, the genesis of pathogen-associated structures such as papillae and the extra-haustorial membrane necessitates polarization of membranes and membrane trafficking pathways. Unlocking the mechanisms by which this occurs will enable greater understanding of how targeted defences, some of which result in resistance, are executed. This review will survey some of the changes that occur in host membranes during pathogen attack and how these are associated with the generation of defence responses. © The Author 2015. Published by Oxford University Press on behalf of the Society for Experimental Biology. All rights reserved. For permissions, please email: journals.permissions@oup.com.

Photoinduced piezooptics effect in TeO2-Ga2O3 glasses

NASA Astrophysics Data System (ADS)

Ozga, K.; Fedorchuk, A. O.; Armand, P.

2015-08-01

We have found that during the bicolor illumination by two boicolor coherent wavelengths 1540 nm/770 nm there occurred substantial changes of the elastooptical non-diagonal coefficients at 1150 nm cw laser wavelength. They are maximal at power densities 400 … 500 MW/cm2. The studies have shown that the maximal effect exists for ultra-fast quenching glasses and occurs after the 1-2 min of the treatment. The switching off of the optical treatment leads to the disappearance of the photoinduced piezooptics at about 100 ms. The observed changes are explained within the photoinduced changes of the charge density distribution for the principal structural clusters within a framework of the DFT approach. The studies were done both for diagonal as well as off-diagonal piezooptical effect (POE) tensor components.

Changes in coral-reef structure through the Miocene in the Mediterranean province: Adaptive versus environmental influence

NASA Astrophysics Data System (ADS)

Pomar, Luis; Hallock, Pamela

2007-10-01

Well-documented Mediterranean examples of Miocene carbonate platforms, with complete exposures from shallow-water to basinal facies, provide evidence for temporal changes in reef-building capacity of zooxanthellate corals. In pre-late Tortonian platforms, small coralgal patches and mounds occur from platform top to the toe of slope, but they did not build to sea level. In contrast, barrier reefs with unequivocal reef-crest structures that reached sea level are documented in late Tortonian-early Messinian platforms. We suggest that a change in both calcification rates and bathymetric zonation was the result of coevolution of corals and Symbiodinium zooxanthellae, coeval to global cooling and, at least at a regional scale, a geochemical change that supported widespread aragonite precipitation through the late Miocene.

Ultrastructural changes of goat corpus luteum during the estrous cycle.

PubMed

Jiang, Yi-Fan; Hsu, Meng-Chieh; Cheng, Chiung-Hsiang; Tsui, Kuan-Hao; Chiu, Chih-Hsien

2016-07-01

The present study was designed to study the ultrastructure of goat corpora lutea (CL, n=10) and structural changes as related to steroidogenic functions during the estrous cycle. The reproduction status of goats was estimated by analyzing serum progesterone concentrations. The CL at various stages was surgically collected. To characterize ultrastructural features associated with steroidogenesis, tissue and cellular structures were studied. Blood supplies were examined based on features of the endothelial cells and capillary structures in the CL. Activated endothelial cells and developing vessels were observed in the early stage, whereas mature endothelial cells, accumulating extracellular matrix fibers, and stabilized vessels were observed in the middle and late stages of assessment. In the late stage of assessment, shrunken goat luteal cells scattered around the capillaries were detected and formed circular regression areas. Features of autophagy and luteal cell apoptosis were noted. In large luteal cells, steroidogenic organelles were present, including microvillar channels, endoplasmic reticulum, and mitochondria. Conformational changes in the endoplasmic reticulum and increased mitochondria with tubular cristae were observed in the early-middle CL transitions. In contrast, mitochondria swelled and the cristae transformed to the lamellar type in the late stage, suggesting that organelle plasticity could contribute to steroidogenesis in goat CL. In conclusion, results suggest angiogenesis occurs in early developing CL and programmed cell death occurred in the late stage of CL assessment in the present study. Structures and quantiles of steroidogenic organelles are correlated with the steroidogenic functions in goats. Copyright © 2016 Elsevier B.V. All rights reserved.

Mapping Polymerization and Allostery of Hemoglobin S Using Point Mutations

PubMed Central

Weinkam, Patrick; Sali, Andrej

2014-01-01

Hemoglobin is a complex system that undergoes conformational changes in response to oxygen, allosteric effectors, mutations, and environmental changes. Here, we study allostery and polymerization of hemoglobin and its variants by application of two previously described methods: (i) AllosMod for simulating allostery dynamics given two allosterically related input structures and (ii) a machine-learning method for dynamics- and structure-based prediction of the mutation impact on allostery (Weinkam et al. J. Mol. Biol. 2013), now applicable to systems with multiple coupled binding sites such as hemoglobin. First, we predict the relative stabilities of substates and microstates of hemoglobin, which are determined primarily by entropy within our model. Next, we predict the impact of 866 annotated mutations on hemoglobin’s oxygen binding equilibrium. We then discuss a subset of 30 mutations that occur in the presence of the sickle cell mutation and whose effects on polymerization have been measured. Seven of these HbS mutations occur in three predicted druggable binding pockets that might be exploited to directly inhibit polymerization; one of these binding pockets is not apparent in the crystal structure but only in structures generated by AllosMod. For the 30 mutations, we predict that mutation-induced conformational changes within a single tetramer tend not to significantly impact polymerization; instead, these mutations more likely impact polymerization by directly perturbing a polymerization interface. Finally, our analysis of allostery allows us to hypothesize why hemoglobin evolved to have multiple subunits and a persistent low frequency sickle cell mutation. PMID:23957820

Interrogation of bimetallic particle oxidation in three dimensions at the nanoscale

DOE PAGES

Han, Lili; Meng, Qingping; Wang, Deli; ...

2016-12-08

An understanding of bimetallic alloy oxidation is key to the design of hollow-structured binary oxides and the optimization of their catalytic performance. However, one roadblock encountered in studying these binary oxide systems is the difficulty in describing the heterogeneities that occur in both structure and chemistry as a function of reaction coordinate. This is due to the complexity of the three-dimensional mosaic patterns that occur in these heterogeneous binary systems. By combining real-time imaging and chemical-sensitive electron tomography, we show that it is possible to characterize these systems with simultaneous nanoscale and chemical detail. We find that there is oxidation-inducedmore » chemical segregation occurring on both external and internal surfaces. Additionally, there is another layer of complexity that occurs during the oxidation, namely that the morphology of the initial oxide surface can change the oxidation modality. As a result, this work characterizes the pathways that can control the morphology in binary oxide materials.« less

The persistence of the attentional bias to regularities in a changing environment.

PubMed

Yu, Ru Qi; Zhao, Jiaying

2015-10-01

The environment often is stable, but some aspects may change over time. The challenge for the visual system is to discover and flexibly adapt to the changes. We examined how attention is shifted in the presence of changes in the underlying structure of the environment. In six experiments, observers viewed four simultaneous streams of objects while performing a visual search task. In the first half of each experiment, the stream in the structured location contained regularities, the shapes in the random location were randomized, and gray squares appeared in two neutral locations. In the second half, the stream in the structured or the random location may change. In the first half of all experiments, visual search was facilitated in the structured location, suggesting that attention was consistently biased toward regularities. In the second half, this bias persisted in the structured location when no change occurred (Experiment 1), when the regularities were removed (Experiment 2), or when new regularities embedded in the original or novel stimuli emerged in the previously random location (Experiments 3 and 6). However, visual search was numerically but no longer reliably faster in the structured location when the initial regularities were removed and new regularities were introduced in the previously random location (Experiment 4), or when novel random stimuli appeared in the random location (Experiment 5). This suggests that the attentional bias was weakened. Overall, the results demonstrate that the attentional bias to regularities was persistent but also sensitive to changes in the environment.

Continuous gradient temperature Raman spectroscopy of unsaturated fatty acids

USDA-ARS?s Scientific Manuscript database

A new innovative technique gradient temperature, Raman spectroscopy (GTRS), identifies Raman frequency shifts in solid or liquid samples, and correlates them with specific temperature ranges within which flexible structures absorb heat. GTRS can easily detect changes that occur within one celcius te...

The impact of Marcellus gas development on the rural transportation infrastructure.

DOT National Transportation Integrated Search

2013-07-01

Deterioration was observed to occur in the wearing surfaces, decks, and parapets for all seven of the structures inspected. To date, little to no deck condition change was observed compared to the reviewed inspection reports. However, the oldest brid...

Forest resources of east Oklahoma, 1993

Treesearch

James F. Rosson

2001-01-01

The principal findings of the sixth forest survey of east Oklahoma (1993) and changes that have occurred since the previous survey are presented. Topics examined include forest area, ownership, forest-type groups, stand structure, basal area, timber volume, growth, removals, mortality, harvesting, and management activity.

Forest resources of east Texas, 1992

Treesearch

James F. Rosson

2000-01-01

The principal findings of the sixth forest survey of east Texas (1992) and changes that have occurred since the previous survey are presented. Topics examined include forest area, ownership, forest-type groups, stand structure, basal area, timber volume, growth, removals, mortality, harvesting, and management activity.

78 FR 9803 - Tennessee Abandoned Mine Land Program

Federal Register 2010, 2011, 2012, 2013, 2014

2013-02-12

..., dangerous impoundments, abandoned structures/equipment, open mine portals, and open mine shafts and refuse..., policy, procedural, and organizational changes that have occurred since 1984. DATES: Effective Date... procedures to manage their financial management, equipment, and procurement systems. OMB Circular A-102 was...

Study of certain features of the electronic structure of the ternary alloys Ni2(Mn, Fe) and Ni3(Mn, Co)

NASA Technical Reports Server (NTRS)

Zhukova, V. M.; Fadin, V. P.

1981-01-01

The changes in electronic structure related to transport processes occurring during the alloying of he alloy Ni3Mn with iron and cobalt, and the ordering of the ternary alloys thus formed are presented. The Hall effect, the absolute thermal emf, the internal saturation induction, the Nernst-Ettingshausen constant, and the electrical resistivity were measured. Results show a decrease in the contribution of hole sections of the Fermi surface to the transport process occurs together with a considerable increase in the contribution of electron sections. In this case, the mobility of 3 dimensional holes decreases and the mobility of 4s electrons increases considerably.

Right hemisphere structural adaptation and changing language skills years after left hemisphere stroke.

PubMed

Hope, Thomas M H; Leff, Alex P; Prejawa, Susan; Bruce, Rachel; Haigh, Zula; Lim, Louise; Ramsden, Sue; Oberhuber, Marion; Ludersdorfer, Philipp; Crinion, Jenny; Seghier, Mohamed L; Price, Cathy J

2017-06-01

Stroke survivors with acquired language deficits are commonly thought to reach a 'plateau' within a year of stroke onset, after which their residual language skills will remain stable. Nevertheless, there have been reports of patients who appear to recover over years. Here, we analysed longitudinal change in 28 left-hemisphere stroke patients, each more than a year post-stroke when first assessed-testing each patient's spoken object naming skills and acquiring structural brain scans twice. Some of the patients appeared to improve over time while others declined; both directions of change were associated with, and predictable given, structural adaptation in the intact right hemisphere of the brain. Contrary to the prevailing view that these patients' language skills are stable, these results imply that real change continues over years. The strongest brain-behaviour associations (the 'peak clusters') were in the anterior temporal lobe and the precentral gyrus. Using functional magnetic resonance imaging, we confirmed that both regions are actively involved when neurologically normal control subjects name visually presented objects, but neither appeared to be involved when the same participants used a finger press to make semantic association decisions on the same stimuli. This suggests that these regions serve word-retrieval or articulatory functions in the undamaged brain. We teased these interpretations apart by reference to change in other tasks. Consistent with the claim that the real change is occurring here, change in spoken object naming was correlated with change in two other similar tasks, spoken action naming and written object naming, each of which was independently associated with structural adaptation in similar (overlapping) right hemisphere regions. Change in written object naming, which requires word-retrieval but not articulation, was also significantly more correlated with both (i) change in spoken object naming; and (ii) structural adaptation in the two peak clusters, than was change in another task-auditory word repetition-which requires articulation but not word retrieval. This suggests that the changes in spoken object naming reflected variation at the level of word-retrieval processes. Surprisingly, given their qualitatively similar activation profiles, hypertrophy in the anterior temporal region was associated with improving behaviour, while hypertrophy in the precentral gyrus was associated with declining behaviour. We predict that either or both of these regions might be fruitful targets for neural stimulation studies (suppressing the precentral region and/or enhancing the anterior temporal region), aiming to encourage recovery or arrest decline even years after stroke occurs. © The Author (2017). Published by Oxford University Press on behalf of the Guarantors of Brain.

Right hemisphere structural adaptation and changing language skills years after left hemisphere stroke

PubMed Central

Leff, Alex P.; Prejawa, Susan; Bruce, Rachel; Haigh, Zula; Lim, Louise; Ramsden, Sue; Oberhuber, Marion; Ludersdorfer, Philipp; Crinion, Jenny; Seghier, Mohamed L.; Price, Cathy J.

2017-01-01

Abstract Stroke survivors with acquired language deficits are commonly thought to reach a ‘plateau’ within a year of stroke onset, after which their residual language skills will remain stable. Nevertheless, there have been reports of patients who appear to recover over years. Here, we analysed longitudinal change in 28 left-hemisphere stroke patients, each more than a year post-stroke when first assessed—testing each patient’s spoken object naming skills and acquiring structural brain scans twice. Some of the patients appeared to improve over time while others declined; both directions of change were associated with, and predictable given, structural adaptation in the intact right hemisphere of the brain. Contrary to the prevailing view that these patients’ language skills are stable, these results imply that real change continues over years. The strongest brain–behaviour associations (the ‘peak clusters’) were in the anterior temporal lobe and the precentral gyrus. Using functional magnetic resonance imaging, we confirmed that both regions are actively involved when neurologically normal control subjects name visually presented objects, but neither appeared to be involved when the same participants used a finger press to make semantic association decisions on the same stimuli. This suggests that these regions serve word-retrieval or articulatory functions in the undamaged brain. We teased these interpretations apart by reference to change in other tasks. Consistent with the claim that the real change is occurring here, change in spoken object naming was correlated with change in two other similar tasks, spoken action naming and written object naming, each of which was independently associated with structural adaptation in similar (overlapping) right hemisphere regions. Change in written object naming, which requires word-retrieval but not articulation, was also significantly more correlated with both (i) change in spoken object naming; and (ii) structural adaptation in the two peak clusters, than was change in another task—auditory word repetition—which requires articulation but not word retrieval. This suggests that the changes in spoken object naming reflected variation at the level of word-retrieval processes. Surprisingly, given their qualitatively similar activation profiles, hypertrophy in the anterior temporal region was associated with improving behaviour, while hypertrophy in the precentral gyrus was associated with declining behaviour. We predict that either or both of these regions might be fruitful targets for neural stimulation studies (suppressing the precentral region and/or enhancing the anterior temporal region), aiming to encourage recovery or arrest decline even years after stroke occurs. PMID:28444235

Effect of von Karman Vortex Shedding on Regular and Open-slit V-gutter Stabilized Turbulent Premixed Flames

DTIC Science & Technology

2012-04-01

Both flame lengths shrink and large scale disruptions occur downstream with vortex shedding carrying reaction zones. Flames in both flameholders...9) the flame structure changes dramatically for both regular and open-slit V-gutter. Both flame lengths shrink and large scale disruptions occur...reduces the flame length . However, qualitatively the open-slit V-gutter appears to be more sensitive than the regular V-gutter. Both flames remain

Nondestructive ultrasonic testing of materials

DOEpatents

Hildebrand, Bernard P.

1994-01-01

Reflection wave forms obtained from aged and unaged material samples can be compared in order to indicate trends toward age-related flaws. Statistical comparison of a large number of data points from such wave forms can indicate changes in the microstructure of the material due to aging. The process is useful for predicting when flaws may occur in structural elements of high risk structures such as nuclear power plants, airplanes, and bridges.

Nondestructive ultrasonic testing of materials

DOEpatents

Hildebrand, B.P.

1994-08-02

Reflection wave forms obtained from aged and unaged material samples can be compared in order to indicate trends toward age-related flaws. Statistical comparison of a large number of data points from such wave forms can indicate changes in the microstructure of the material due to aging. The process is useful for predicting when flaws may occur in structural elements of high risk structures such as nuclear power plants, airplanes, and bridges. 4 figs.

Cofactor specificity motifs and the induced fit mechanism in class I ketol-acid reductoisomerases.

PubMed

Cahn, Jackson K B; Brinkmann-Chen, Sabine; Spatzal, Thomas; Wiig, Jared A; Buller, Andrew R; Einsle, Oliver; Hu, Yilin; Ribbe, Markus W; Arnold, Frances H

2015-06-15

Although most sequenced members of the industrially important ketol-acid reductoisomerase (KARI) family are class I enzymes, structural studies to date have focused primarily on the class II KARIs, which arose through domain duplication. In the present study, we present five new crystal structures of class I KARIs. These include the first structure of a KARI with a six-residue β2αB (cofactor specificity determining) loop and an NADPH phosphate-binding geometry distinct from that of the seven- and 12-residue loops. We also present the first structures of naturally occurring KARIs that utilize NADH as cofactor. These results show insertions in the specificity loops that confounded previous attempts to classify them according to loop length. Lastly, we explore the conformational changes that occur in class I KARIs upon binding of cofactor and metal ions. The class I KARI structures indicate that the active sites close upon binding NAD(P)H, similar to what is observed in the class II KARIs of rice and spinach and different from the opening of the active site observed in the class II KARI of Escherichia coli. This conformational change involves a decrease in the bending of the helix that runs between the domains and a rearrangement of the nicotinamide-binding site. © The Authors Journal Compilation © 2015 Biochemical Society.

Population structure and strong divergent selection shape phenotypic diversification in maize landraces.

PubMed

Pressoir, G; Berthaud, J

2004-02-01

To conserve the long-term selection potential of maize, it is necessary to investigate past and present evolutionary processes that have shaped quantitative trait variation. Understanding the dynamics of quantitative trait evolution is crucial to future crop breeding. We characterized population differentiation of maize landraces from the State of Oaxaca, Mexico for quantitative traits and molecular markers. Qst values were much higher than Fst values obtained for molecular markers. While low values of Fst (0.011 within-village and 0.003 among-villages) suggest that considerable gene flow occurred among the studied populations, high levels of population differentiation for quantitative traits were observed (ie an among-village Qst value of 0.535 for kernel weight). Our results suggest that although quantitative traits appear to be under strong divergent selection, a considerable amount of gene flow occurs among populations. Furthermore, we characterized nonproportional changes in the G matrix structure both within and among villages that are consequences of farmer selection. As a consequence of these differences in the G matrix structure, the response to multivariate selection will be different from one population to another. Large changes in the G matrix structure could indicate that farmers select for genes of major and pleiotropic effect. Farmers' decision and selection strategies have a great impact on phenotypic diversification in maize landraces.

A framework for evaluating the impact of obesity prevention strategies on socioeconomic inequalities in weight.

PubMed

Backholer, Kathryn; Beauchamp, Alison; Ball, Kylie; Turrell, Gavin; Martin, Jane; Woods, Julie; Peeters, Anna

2014-10-01

We developed a theoretical framework to organize obesity prevention interventions by their likely impact on the socioeconomic gradient of weight. The degree to which an intervention involves individual agency versus structural change influences socioeconomic inequalities in weight. Agentic interventions, such as standalone social marketing, increase socioeconomic inequalities. Structural interventions, such as food procurement policies and restrictions on unhealthy foods in schools, show equal or greater benefit for lower socioeconomic groups. Many obesity prevention interventions belong to the agento-structural types of interventions, and account for the environment in which health behaviors occur, but they require a level of individual agency for behavioral change, including workplace design to encourage exercise and fiscal regulation of unhealthy foods or beverages. Obesity prevention interventions differ in their effectiveness across socioeconomic groups. Limiting further increases in socioeconomic inequalities in obesity requires implementation of structural interventions. Further empirical evaluation, especially of agento-structural type interventions, remains crucial.

Effect of drying methods of microencapsulated Lactobacillus acidophilus and Lactococcus lactis ssp. cremoris on secondary protein structure and glass transition temperature as studied by Fourier transform infrared and differential scanning calorimetry.

PubMed

Dianawati, Dianawati; Mishra, Vijay; Shah, Nagendra P

2013-03-01

Protective mechanisms of casein-based microcapsules containing mannitol on Lactobacillus acidophilus and Lactococcus lactis ssp. cremoris, changes in their secondary protein structures, and glass transition of the microcapsules were studied after spray- or freeze-drying and after 10 wk of storage in aluminum foil pouches containing different desiccants (NaOH, LiCl, or silica gel) at 25°C. An in situ Fourier transform infrared analysis was carried out to recognize any changes in fatty acids (FA) of bacterial cell envelopes, interaction between polar site of cell envelopes and microcapsules, and alteration of their secondary protein structures. Differential scanning calorimetry was used to determine glass transition of microcapsules based on glass transition temperature (T(g)) values. Hierarchical cluster analysis based on functional groups of cell envelopes and secondary protein structures was also carried out to classify the microencapsulated bacteria due to the effects of spray- or freeze-drying and storage for 10 wk. The results showed that drying process did not affect FA and secondary protein structures of bacteria; however, those structures were affected during storage depending upon the type of desiccant used. Interaction between exterior of bacterial cell envelopes and microencapsulant occurred after spray- or freeze-drying; however, these structures were maintained after storage in foil pouch containing sodium hydroxide. Method of drying and type of desiccants influenced the level of similarities of microencapsulated bacteria. Desiccants and method of drying affected glass transition, yet no T(g) ≤25°C was detected. This study demonstrated that the changes in FA and secondary structures of the microencapsulated bacteria still occurred during storage at T(g) above room temperature, indicating that the glassy state did not completely prevent chemical activities. Copyright © 2013 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.

Effects of the bond polarity on the structural and dynamical properties of silica-like liquids

NASA Astrophysics Data System (ADS)

Pafong Sanjon, E.; Drossel, B.; Vogel, M.

2018-03-01

Silica is a network-forming liquid that shares many properties with water due to its tetrahedral structure. It undergoes a transition from a fragile to a strong liquid as the temperature is decreased, which is accompanied by a structural change to lower density and higher tetrahedral order. In order to disentangle the effects of Coulomb and van der Waals interactions on the structure and dynamics of liquid silica, we modify the bond polarity by changing the partial charges assigned to each atom. Using molecular dynamics simulations, we show that density, tetrahedral order, and structural relaxation times decrease when reducing bond polarity. Moreover, we find that the density maximum and the fragile-to-strong transition move to lower temperatures until they eventually vanish when the partial charges are decreased below approximately 75% of their regular value. Irrespective of whether strong or fragile behavior exists, structural relaxation is governed by hopping motion at sufficiently low temperatures. As long as there is a strong regime, the energy barrier associated with strong dynamics decreases with decreasing partial charges, but the dependence on the bond polarity differs from that of the activation energy in the Arrhenius regime at high temperatures. We show that the fragile-to-strong transition is associated with structural changes occurring between the first and second coordination shells that lead to a decrease in density and an increase in tetrahedral order. In particular, independent of the value of the partial charges, the distribution of the local structures is the same at this dynamic crossover, but we find no evidence that the effect occurs upon crossing the Widom line. In the fragile regime at intermediate temperatures, the relaxation times are well described by a previously proposed model which decomposes the apparent activation energy into a constant single-particle contribution and a temperature-dependent collective contribution. However, our results for silica-like melts do not obey several common relations of the model parameters reported for molecular glass formers.

Structural response of phyllomanganates to wet aging and aqueous Mn(II)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hinkle, Margaret A. G.; Flynn, Elaine D.; Catalano, Jeffrey G.

Naturally occurring Mn(IV/III) oxides are often formed through microbial Mn(II) oxidation, resulting in reactive phyllomanganates with varying Mn(IV), Mn(III), and vacancy contents. Residual aqueous Mn(II) may adsorb in the interlayer of phyllomanganates above vacancies in their octahedral sheets. The potential for interlayer Mn(II)-layer Mn(IV) comproportionation reactions and subsequent formation of structural Mn(III) suggests that aqueous Mn(II) may cause phyllomanganate structural changes that alters mineral reactivity or trace metal scavenging. Here we examine the effects of aging phyllomanganates with varying initial vacancy and Mn(III) content in the presence and absence of dissolved Mn(II) at pH 4 and 7. Three phyllomanganates weremore » studied: two exhibiting turbostratic layer stacking (δ-MnO2 with high vacancy content and hexagonal birnessite with both vacancies and Mn(III) substitutions) and one with rotationally ordered layer stacking (triclinic birnessite containing predominantly Mn(III) substitutions). Structural analyses suggest that during aging at pH 4, Mn(II) adsorbs above vacancies and promotes the formation of phyllomanganates with rotationally ordered sheets and mixed symmetries arranged into supercells, while structural Mn(III) undergoes disproportionation. These structural changes at pH 4 correlate with reduced Mn(II) uptake onto triclinic and hexagonal birnessite after 25 days relative to 48 h of reaction, indicating that phyllomanganate reactivity decreases upon aging with Mn(II), or that recrystallization processes involving Mn(II) uptake occur over 25 days. At pH 7, Mn(II) adsorbs and causes limited structural effects, primarily increasing sheet stacking in δ-MnO2. These results show that aging-induced structural changes in phyllomanganates are affected by aqueous Mn(II), pH, and initial solid-phase Mn(III) content. In conclusion, such restructuring likely alters manganese oxide reactions with other constituents in environmental and geologic systems, particularly trace metals and redox-active compounds.« less

Structural response of phyllomanganates to wet aging and aqueous Mn(II)

DOE PAGES

Hinkle, Margaret A. G.; Flynn, Elaine D.; Catalano, Jeffrey G.

2016-08-06

Naturally occurring Mn(IV/III) oxides are often formed through microbial Mn(II) oxidation, resulting in reactive phyllomanganates with varying Mn(IV), Mn(III), and vacancy contents. Residual aqueous Mn(II) may adsorb in the interlayer of phyllomanganates above vacancies in their octahedral sheets. The potential for interlayer Mn(II)-layer Mn(IV) comproportionation reactions and subsequent formation of structural Mn(III) suggests that aqueous Mn(II) may cause phyllomanganate structural changes that alters mineral reactivity or trace metal scavenging. Here we examine the effects of aging phyllomanganates with varying initial vacancy and Mn(III) content in the presence and absence of dissolved Mn(II) at pH 4 and 7. Three phyllomanganates weremore » studied: two exhibiting turbostratic layer stacking (δ-MnO2 with high vacancy content and hexagonal birnessite with both vacancies and Mn(III) substitutions) and one with rotationally ordered layer stacking (triclinic birnessite containing predominantly Mn(III) substitutions). Structural analyses suggest that during aging at pH 4, Mn(II) adsorbs above vacancies and promotes the formation of phyllomanganates with rotationally ordered sheets and mixed symmetries arranged into supercells, while structural Mn(III) undergoes disproportionation. These structural changes at pH 4 correlate with reduced Mn(II) uptake onto triclinic and hexagonal birnessite after 25 days relative to 48 h of reaction, indicating that phyllomanganate reactivity decreases upon aging with Mn(II), or that recrystallization processes involving Mn(II) uptake occur over 25 days. At pH 7, Mn(II) adsorbs and causes limited structural effects, primarily increasing sheet stacking in δ-MnO2. These results show that aging-induced structural changes in phyllomanganates are affected by aqueous Mn(II), pH, and initial solid-phase Mn(III) content. In conclusion, such restructuring likely alters manganese oxide reactions with other constituents in environmental and geologic systems, particularly trace metals and redox-active compounds.« less

The Effect of Spaceflight on the Ultrastructure of the Cerebellum

NASA Technical Reports Server (NTRS)

Holstein, Gay R.; Martinelli, Giorgio P.

2003-01-01

In weightlessness, astronauts and cosmonauts may experience postural illusions as well as motion sickness symptoms known as the space adaptation syndrome. Upon return to Earth, they have irregularities in posture and balance. The adaptation to microgravity and subsequent re-adaptation to Earth occurs over several days. At the cellular level, a process called neuronal plasticity may mediate this adaptation. The term plasticity refers to the flexibility and modifiability in the architecture and functions of the nervous system. In fact, plastic changes are thought to underlie not just behavioral adaptation, but also the more generalized phenomena of learning and memory. The goal of this experiment was to identify some of the structural alterations that occur in the rat brain during the sensory and motor adaptation to microgravity. One brain region where plasticity has been studied extensively is the cerebellar cortex-a structure thought to be critical for motor control, coordination, the timing of movements, and, most relevant to the present experiment, motor learning. Also, there are direct as well as indirect connections between projections from the gravity-sensing otolith organs and several subregions of the cerebellum. We tested the hypothesis that alterations in the ultrastructural (the structure within the cell) architecture of rat cerebellar cortex occur during the early period of adaptation to microgravity, as the cerebellum adapts to the absence of the usual gravitational inputs. The results show ultrastructural evidence for neuronal plasticity in the central nervous system of adult rats after 24 hours of spaceflight. Qualitative studies conducted on tissue from the cerebellar cortex (specifically, the nodulus of the cerebellum) indicate that ultrastructural signs of plasticity are present in the cerebellar zones that receive input from the gravity-sensing organs in the inner ear (the otoliths). These changes are not observed in this region in cagematched ground control animals. The specific changes include the formation of lamellar bodies, profoundly enlarged Purkinje cell mitochondria, the presence of inter-neuronal cellular protrusions in the molecular layer, and signs of degeneration in the distal dendrites of the Purkinje cells. Since these morphologic signs are not apparent in the control animals, they are not likely to be due to caging or tissue processing effects. The particular nature of the structural alterations in the nodulus, most notably the formation of lamellar bodies and the presence of degeneration, further suggests that excitotoxicity (damaging overstimulation of neurons) may play a role in the short-term neural response to spaceflight. These findings suggest a structural basis for the neuronal and synaptic plasticity accompanying the central nervous system response to altered gravity and help identify the cellular bases underlying the vestibular abnormalities experienced by astronauts during periods of adaptation and re-adaptation to different gravitational forces. Also, since the short- and long-term changes in neural structure occurring during such periods of adaptation resemble the neuronal alterations that occur in some neurologic disorders such as stroke, these findings may offer guidance in the development of strategies for rehabilitation and treatment of such disorders.

The categorical structure of semantic memory for famous people: a new approach using release from proactive interference.

PubMed

Darling, Stephen; Valentine, Tim

2005-05-01

Memory for familiar people is essential to understand their identity and guide social interaction. Nevertheless, we know surprisingly little about the structure of such memory. Previous research has assumed that semantic memory for people has a categorical structure, but recently it was proposed that memory for people consists only of associations and lacks any categorical structure. Four experiments are reported that use a novel approach by adapting the 'release from proactive interference' (RPI) methodology for use with lists of famous names. Proactive interference occurs when items presented on successive trials are drawn from the same category. Recall can improve following a change to a different category. Sets of names were selected relating to aspects previously demonstrated, on the basis of reaction time data, to form a category (occupation) and a property (nationality) of celebrities (Johnston & Bruce, 1990). RPI was observed for a change at both levels of representation but was only present without explicitly cueing the change of set when the stimuli differed at the category level. At the property level, RPI was only evident when change of set was explicitly cued. RPI was absent at the set change in a novel, ad hoc distinction suggesting that the effect reflected the underlying memory structure.

White matter structure changes as adults learn a second language.

PubMed

Schlegel, Alexander A; Rudelson, Justin J; Tse, Peter U

2012-08-01

Traditional models hold that the plastic reorganization of brain structures occurs mainly during childhood and adolescence, leaving adults with limited means to learn new knowledge and skills. Research within the last decade has begun to overturn this belief, documenting changes in the brain's gray and white matter as healthy adults learn simple motor and cognitive skills [Lövdén, M., Bodammer, N. C., Kühn, S., Kaufmann, J., Schütze, H., Tempelmann, C., et al. Experience-dependent plasticity of white-matter microstructure extends into old age. Neuropsychologia, 48, 3878-3883, 2010; Taubert, M., Draganski, B., Anwander, A., Müller, K., Horstmann, A., Villringer, A., et al. Dynamic properties of human brain structure: Learning-related changes in cortical areas and associated fiber connections. The Journal of Neuroscience, 30, 11670-11677, 2010; Scholz, J., Klein, M. C., Behrens, T. E. J., & Johansen-Berg, H. Training induces changes in white-matter architecture. Nature Neuroscience, 12, 1370-1371, 2009; Draganski, B., Gaser, C., Busch, V., Schuirer, G., Bogdahn, U., & May, A. Changes in grey matter induced by training. Nature, 427, 311-312, 2004]. Although the significance of these changes is not fully understood, they reveal a brain that remains plastic well beyond early developmental periods. Here we investigate the role of adult structural plasticity in the complex, long-term learning process of foreign language acquisition. We collected monthly diffusion tensor imaging scans of 11 English speakers who took a 9-month intensive course in written and spoken Modern Standard Chinese as well as from 16 control participants who did not study a language. We show that white matter reorganizes progressively across multiple sites as adults study a new language. Language learners exhibited progressive changes in white matter tracts associated with traditional left hemisphere language areas and their right hemisphere analogs. Surprisingly, the most significant changes occurred in frontal lobe tracts crossing the genu of the corpus callosum-a region not generally included in current neural models of language processing. These results indicate that plasticity of white matter plays an important role in adult language learning and additionally demonstrate the potential of longitudinal diffusion tensor imaging as a new tool to yield insights into cognitive processes.

Ionic and Optical Properties of Methylammonium Lead Iodide Perovskite across the Tetragonal-Cubic Structural Phase Transition

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hoque, Md Nadim Ferdous; Islam, Nazifah; Li, Zhen

Practical hybrid perovskite solar cells (PSCs) must endure temperatures above the tetragonal-cubic structural phase transition of methylammonium lead iodide (MAPbI3). However, the ionic and optical properties of MAPbI3 in such a temperature range, and particularly, dramatic changes in these properties resulting from a structural phase transition, are not well studied. Herein, we report a striking contrast at approximately 45 degrees C in the ionic/electrical properties of MAPbl3 owing to a change of the ion activation energy from 0.7 to 0.5 eV, whereas the optical properties exhibit no particular transition except for the steady increase of the bandgap with temperature. Thesemore » observations can be explained by the 'continuous' nature of perovskite phase transition. We speculate that the critical temperature at which the ionic/electrical properties change, although related to crystal symmetry variation, is not necessarily the same temperature as when tetragonal-cubic structural phase transition occurs.« less

Unraveling the Hydrogenation of TiO 2 and Graphene Oxide/TiO 2 Composites in Real Time by in Situ Synchrotron X-ray Powder Diffraction and Pair Distribution Function Analysis

DOE PAGES

Nguyen-Phan, Thuy-Duong; Liu, Zongyuan; Luo, Si; ...

2016-02-18

The functionalization of graphene oxide (GO) and graphene by TiO 2 and other metal oxides has attracted considerable attention due to numerous promising applications in catalysis, energy conversion, and storage. We propose hydrogenation of this class of materials as a promising way to tune catalytic properties by altering the structural and chemical transformations that occur upon H incorporation. We also investigate the structural changes that occur during the hydrogenation process using in situ powder X-ray diffraction and pair distribution function analysis of GO–TiO 2 and TiO 2 under H 2 reduction. Sequential Rietveld refinement was employed to gain insight intomore » the evolution of crystal growth of TiO 2 nanoparticles in the presence of two-dimensional (2D) GO nanosheets. GO sheets not only significantly retarded the nucleation and growth of rutile impurities, stabilizing the anatase structure, but was also partially reduced to hydrogenated graphene by the introduction of atomic hydrogen into the honeycomb lattice. We discuss the hydrogenation processes and the resulting composite structure that occurs during the incorporation of atomic H and the dynamic structural transformations that leads to a highly active photocatalyst.« less

Variation of directional reflectance factors with structural changes of a developing alfalfa canopy

NASA Technical Reports Server (NTRS)

Kirchner, J. A.; Kimes, D. S.; Mcmurtrey, J. E., III

1982-01-01

Directional reflectance factors of an alfalfa canopy were determined and related to canopy structure, agronomic variables, and irradiance conditions at four periods during a cutting cycle. Nadir and off-nadir reflectance factors decreased with increasing biomass in Thematic Mapper band 3(0.63-0.69 micrometer) and increased with increasing biomass in band 4(0.76-0.90 micrometer). The sensor view angle had less impact on perceived reflectance as the alfalfa progressed from an erectophile canopy of stems after harvest to a near planophile canopy of leaves at maturity. Studies of directional reflectance are needed for testing and upgrading vegetation canopy models and to aid in the complex interpretation problems presented by aircraft scanners and pointable satellites where illumination and viewing geometries may vary widely. Distinct changes in the patterns of radiance observed by a sensor as structural and biomass changes occur are keys to monitoring the growth and condition of crops.

Nanomechanics of the substrate binding domain of Hsp70 determine its allosteric ATP-induced conformational change.

PubMed

Mandal, Soumit Sankar; Merz, Dale R; Buchsteiner, Maximilian; Dima, Ruxandra I; Rief, Matthias; Žoldák, Gabriel

2017-06-06

Owing to the cooperativity of protein structures, it is often almost impossible to identify independent subunits, flexible regions, or hinges simply by visual inspection of static snapshots. Here, we use single-molecule force experiments and simulations to apply tension across the substrate binding domain (SBD) of heat shock protein 70 (Hsp70) to pinpoint mechanical units and flexible hinges. The SBD consists of two nanomechanical units matching 3D structural parts, called the α- and β-subdomain. We identified a flexible region within the rigid β-subdomain that gives way under load, thus opening up the α/β interface. In exactly this region, structural changes occur in the ATP-induced opening of Hsp70 to allow substrate exchange. Our results show that the SBD's ability to undergo large conformational changes is already encoded by passive mechanics of the individual elements.

Nanomechanics of the substrate binding domain of Hsp70 determine its allosteric ATP-induced conformational change

PubMed Central

Mandal, Soumit Sankar; Buchsteiner, Maximilian; Dima, Ruxandra I.; Rief, Matthias; Žoldák, Gabriel

2017-01-01

Owing to the cooperativity of protein structures, it is often almost impossible to identify independent subunits, flexible regions, or hinges simply by visual inspection of static snapshots. Here, we use single-molecule force experiments and simulations to apply tension across the substrate binding domain (SBD) of heat shock protein 70 (Hsp70) to pinpoint mechanical units and flexible hinges. The SBD consists of two nanomechanical units matching 3D structural parts, called the α- and β-subdomain. We identified a flexible region within the rigid β-subdomain that gives way under load, thus opening up the α/β interface. In exactly this region, structural changes occur in the ATP-induced opening of Hsp70 to allow substrate exchange. Our results show that the SBD’s ability to undergo large conformational changes is already encoded by passive mechanics of the individual elements. PMID:28533394

Analysing Health Professionals' Learning Interactions in an Online Social Network: A Longitudinal Study.

PubMed

Li, Xin; Verspoor, Karin; Gray, Kathleen; Barnett, Stephen

2016-01-01

This paper summarises a longitudinal analysis of learning interactions occurring over three years among health professionals in an online social network. The study employs the techniques of Social Network Analysis (SNA) and statistical modeling to identify the changes in patterns of interaction over time and test associated structural network effects. SNA results indicate overall low participation in the network, although some participants became active over time and even led discussions. In particular, the analysis has shown that a change of lead contributor results in a change in learning interaction and network structure. The analysis of structural network effects demonstrates that the interaction dynamics slow down over time, indicating that interactions in the network are more stable. The health professionals may be reluctant to share knowledge and collaborate in groups but were interested in building personal learning networks or simply seeking information.

Determinants of performance failure in the nursing home industry☆

PubMed Central

Zinn, Jacqueline; Mor, Vincent; Feng, Zhanlian; Intrator, Orna

2013-01-01

This study investigates the determinants of performance failure in U.S. nursing homes. The sample consisted of 91,168 surveys from 10,901 facilities included in the Online Survey Certification and Reporting system from 1996 to 2005. Failed performance was defined as termination from the Medicare and Medicaid programs. Determinants of performance failure were identified as core structural change (ownership change), peripheral change (related diversification), prior financial and quality of care performance, size and environmental shock (Medicaid case mix reimbursement and prospective payment system introduction). Additional control variables that could contribute to the likelihood of performance failure were included in a cross-sectional time series generalized estimating equation logistic regression model. Our results support the contention, derived from structural inertia theory, that where in an organization’s structure change occurs determines whether it is adaptive or disruptive. In addition, while poor prior financial and quality performance and the introduction of case mix reimbursement increases the risk of failure, larger size is protective, decreasing the likelihood of performance failure. PMID:19128865

Folding propensity of intrinsically disordered proteins by osmotic stress

DOE PAGES

Mansouri, Amanda L.; Grese, Laura N.; Rowe, Erica L.; ...

2016-10-11

Proteins imparted with intrinsic disorder conduct a range of essential cellular functions. To better understand the folding and hydration properties of intrinsically disordered proteins (IDPs), we used osmotic stress to induce conformational changes in nuclear co-activator binding domain (NCBD) and activator for thyroid hormone and retinoid receptor (ACTR). Osmotic stress was applied by the addition of small and polymeric osmolytes, where we discovered that water contributions to NCBD folding always exceeded those for ACTR. Both NCBD and ACTR were found to gain a-helical structure with increasing osmotic stress, consistent with their folding upon NCBD/ACTR complex formation. Using small-angle neutron scatteringmore » (SANS), we further characterized NCBD structural changes with the osmolyte ethylene glycol. Here a large reduction in overall size initially occurred before substantial secondary structural change. In conclusion, by focusing on folding propensity, and linked hydration changes, we uncover new insights that may be important for how IDP folding contributes to binding.« less

Driven to distraction: A lack of change gives rise to mind wandering.

PubMed

Faber, Myrthe; Radvansky, Gabriel A; D'Mello, Sidney K

2018-04-01

How does the dynamic structure of the external world direct attention? We examined the relationship between event structure and attention to test the hypothesis that narrative shifts (both theoretical and perceived) negatively predict attentional lapses. Self-caught instances of mind wandering were collected while 108 participants watched a 32.5 min film called The Red Balloon. We used theoretical codings of situational change and human perceptions of event boundaries to predict mind wandering in 5-s intervals. Our findings suggest a temporal alignment between the structural dynamics of the film and mind wandering reports. Specifically, the number of situational changes and likelihood of perceiving event boundaries in the prior 0-15 s interval negatively predicted mind wandering net of low-level audiovisual features. Thus, mind wandering is less likely to occur when there is more event change, suggesting that narrative shifts keep attention from drifting inwards. Copyright © 2018 Elsevier B.V. All rights reserved.

Determinants of performance failure in the nursing home industry.

PubMed

Zinn, Jacqueline; Mor, Vincent; Feng, Zhanlian; Intrator, Orna

2009-03-01

This study investigates the determinants of performance failure in U.S. nursing homes. The sample consisted of 91,168 surveys from 10,901 facilities included in the Online Survey Certification and Reporting system from 1996 to 2005. Failed performance was defined as termination from the Medicare and Medicaid programs. Determinants of performance failure were identified as core structural change (ownership change), peripheral change (related diversification), prior financial and quality of care performance, size and environmental shock (Medicaid case mix reimbursement and prospective payment system introduction). Additional control variables that could contribute to the likelihood of performance failure were included in a cross-sectional time series generalized estimating equation logistic regression model. Our results support the contention, derived from structural inertia theory, that where in an organization's structure change occurs determines whether it is adaptive or disruptive. In addition, while poor prior financial and quality performance and the introduction of case mix reimbursement increases the risk of failure, larger size is protective, decreasing the likelihood of performance failure.

Molecular dynamics simulation analysis of the effect of T790M mutation on epidermal growth factor receptor protein architecture in non-small cell lung carcinoma.

PubMed

Peng, Xiao-Nu; Wang, Jing; Zhang, Wei

2017-08-01

Non-small cell lung cancer etiology and its treatment failure are due to epidermal growth factor receptor (EGFR) kinase domain mutations at amino acid position 790. The mutational change from threonine to methionine at position 790 (T790M) is responsible for tyrosine kinase inhibition failure. Using molecular dynamic simulation, the present study investigated the architectural changes occurring at the atomic scale. The 50-nsec runs using a GROMOS force field for wild-type and mutant EGFR's kinase domains were investigated for contrasting variations using Gromacs inbuilt tools. The adenosine triphosphate binding domain and the active site of EGFR were studied extensively in order to understand the structural changes. All the parameters investigated in the present study revealed considerable changes in the studied structures, and the knowledge gained from this may be used to develop novel kinase inhibitors that will be effective irrespective of the structural alterations in kinase domain.

Folding propensity of intrinsically disordered proteins by osmotic stress

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mansouri, Amanda L.; Grese, Laura N.; Rowe, Erica L.

Proteins imparted with intrinsic disorder conduct a range of essential cellular functions. To better understand the folding and hydration properties of intrinsically disordered proteins (IDPs), we used osmotic stress to induce conformational changes in nuclear co-activator binding domain (NCBD) and activator for thyroid hormone and retinoid receptor (ACTR). Osmotic stress was applied by the addition of small and polymeric osmolytes, where we discovered that water contributions to NCBD folding always exceeded those for ACTR. Both NCBD and ACTR were found to gain a-helical structure with increasing osmotic stress, consistent with their folding upon NCBD/ACTR complex formation. Using small-angle neutron scatteringmore » (SANS), we further characterized NCBD structural changes with the osmolyte ethylene glycol. Here a large reduction in overall size initially occurred before substantial secondary structural change. In conclusion, by focusing on folding propensity, and linked hydration changes, we uncover new insights that may be important for how IDP folding contributes to binding.« less

Changes of wood cell walls in response to hygro-mechanical steam treatment.

PubMed

Guo, Juan; Song, Kunlin; Salmén, Lennart; Yin, Yafang

2015-01-22

The effects of compression combined with steam treatment (CS-treatment), i.e. a hygro-mechanical steam treatment on Spruce wood were studied on a cell-structure level to understand the chemical and physical changes of the secondary cell wall occurring under such conditions. Specially, imaging FT-IR microscopy, nanoindentation and dynamic vapour absorption were used to track changes in the chemical structure, in micromechanical and hygroscopic properties. It was shown that CS-treatment resulted in different changes in morphological, chemical and physical properties of the cell wall, in comparison with those under pure steam treatment. After CS-treatment, the cellular structure displayed significant deformations, and the biopolymer components, e.g. hemicellulose and lignin, were degraded, resulting in decreased hygroscopicity and increased mechanical properties of the wood compared to both untreated and steam treated wood. Moreover, CS-treatment resulted in a higher degree of degradation especially in earlywood compared to a more uniform behaviour of wood treated only by steam. Copyright © 2014 Elsevier Ltd. All rights reserved.

Leadership, Charisma, Personality, and Power.

ERIC Educational Resources Information Center

Beaven, Mary H.

Transformational, charismatic leadership occurs in a conflict-ridden situation, where attendant emotional travail is so uncomfortable that macro and micro structures will admit to change in efforts to relieve the tension. An inspirational message that redefines and reprioritizes deeply cherished values and the leader's role-modeling influence…

Thermal alteration experiments on organic matter in recent marine sediments as a model for petroleum genesis

NASA Technical Reports Server (NTRS)

Baedecker, M. J.; Ikan, R.; Ishiwatari, R.; Kaplan, I. R.

1977-01-01

The fate of naturally occurring lipids and pigments in a marine sediment exposed to elevated temperatures was studied. Samples of a young marine sediment from Tanner Basin, California, were heated to a series of temperatures (65-200 C) for varying periods of time (7-64 days). The sediment was analyzed prior to and after heating for pigments, isoprenoid compounds, alcohols, fatty acids, and hydrocarbons. Structural changes caused by heating unextractable organic material (kerogen) were also studied, and the significance of the results for understanding petroleum genesis is considered. Among other results, fatty acids and hydrocarbons increased in abundance although there appeared to be no obvious precursor-to-product relationship via simple decarboxylation reactions. Chlorins were partially converted into porphyrins. The phytyl side chain of pheophytin was initially preserved intact by reduction of the phytyl double bond, but later converted to a variety of isoprenoid compounds including alkanes. Thermal grafting of components onto kerogen occurred as well as structural changes caused by heat.

Aging and Down syndrome: implications for physical therapy.

PubMed

Barnhart, Robert C; Connolly, Barbara

2007-10-01

The number of people over the age of 60 years with lifelong developmental delays is predicted to double by 2030. Down syndrome (DS) is the most frequent chromosomal cause of developmental delays. As the life expectancy of people with DS increases, changes in body function and structure secondary to aging have the potential to lead to activity limitations and participation restrictions for this population. The purpose of this update is to: (1) provide an overview of the common body function and structure changes that occur in adults with DS as they age (thyroid dysfunction, cardiovascular disorders, obesity, musculoskeletal disorders, Alzheimer disease, depression) and (2) apply current research on exercise to the prevention of activity limitations and participation restrictions. As individuals with DS age, a shift in emphasis from disability prevention to the prevention of conditions that lead to activity and participation limitations must occur. Exercise programs appear to have potential to positively affect the overall health of adults with DS, thereby increasing the quality of life and years of healthy life for these individuals.

From Multilingualism to Bilingualism: Changes in Language Use, Language Value, and Social Mobility among Engdewu Speakers in the Solomon Islands

ERIC Educational Resources Information Center

Emerine Hicks, Rachel

2017-01-01

On the island of Santa Cruz in the Solomon Islands, the Engdewu language is facing imminent language shift because of the increasing use of the lingua franca Solomon Islands Pijin in the community. In this article, I argue that this language shift is occurring because of changes to the social structure in Baemawz, one of the villages where Engdewu…

Tree mortality from a short-duration freezing event and global-change-type drought in a Southwestern piñon-juniper woodland, USA

PubMed Central

2014-01-01

This study documents tree mortality in Big Bend National Park in Texas in response to the most acute one-year drought on record, which occurred following a five-day winter freeze. I estimated changes in forest stand structure and species composition due to freezing and drought in the Chisos Mountains of Big Bend National Park using permanent monitoring plot data. The drought killed over half (63%) of the sampled trees over the entire elevation gradient. Significant mortality occurred in trees up to 20 cm diameter (P < 0.05). Pinus cembroides Zucc. experienced the highest seedling and tree mortality (P < 0.0001) (55% of piñon pines died), and over five times as many standing dead pines were observed in 2012 than in 2009. Juniperus deppeana vonSteudal and Quercus emoryi Leibmann also experienced significant declines in tree density (P < 0.02) (30.9% and 20.7%, respectively). Subsequent droughts under climate change will likely cause even greater damage to trees that survived this record drought, especially if such events follow freezes. The results from this study highlight the vulnerability of trees in the Southwest to climatic change and that future shifts in forest structure can have large-scale community consequences. PMID:24949231

Beltless translocation domain of botulinum neurotoxin A embodies a minimum ion-conductive channel.

PubMed

Fischer, Audrey; Sambashivan, Shilpa; Brunger, Axel T; Montal, Mauricio

2012-01-13

Botulinum neurotoxin, the causative agent of the paralytic disease botulism, is an endopeptidase composed of a catalytic domain (or light chain (LC)) and a heavy chain (HC) encompassing the translocation domain (TD) and receptor-binding domain. Upon receptor-mediated endocytosis, the LC and TD are proposed to undergo conformational changes in the acidic endocytic environment resulting in the formation of an LC protein-conducting TD channel. The mechanism of channel formation and the conformational changes in the toxin upon acidification are important but less well understood aspects of botulinum neurotoxin intoxication. Here, we have identified a minimum channel-forming truncation of the TD, the "beltless" TD, that forms transmembrane channels with ion conduction properties similar to those of the full-length TD. At variance with the holotoxin and the HC, channel formation for both the TD and the beltless TD occurs independent of a transmembrane pH gradient. Furthermore, acidification in solution induces moderate secondary structure changes. The subtle nature of the conformational changes evoked by acidification on the TD suggests that, in the context of the holotoxin, larger structural rearrangements and LC unfolding occur preceding or concurrent to channel formation. This notion is consistent with the hypothesis that although each domain of the holotoxin functions individually, each domain serves as a chaperone for the others.

Nanoporous materials for energy applications

NASA Astrophysics Data System (ADS)

Yonemoto, Bryan T.

Batteries have become ubiquitous in modern society by powering small, consumer electronic devices such as flashlights, cell phones, and laptops. Increasingly, batteries are also being examined as a method to improve energy efficiency (and reduce greenhouse gas emissions) for vehicles and power transmission/distribution applications. For lithium-ion based batteries to meet the demands of these new applications, new electrode materials and morphologies are the key to access high energy and/or power density. In this work, the research efforts include two major thrusts, concentrating on the synthesis and understanding of novel porous materials as potential electrodes for rechargeable lithium-ion batteries. The nano-sized walls and multidimensional pore structures allow fast solid state and electrolytic transport, while micron-sized particle ensure better interparticulate contact. The first thrust of research focused on the development of new synthetic approaches for porous material fabrication. A novel ionothermal synthetic method has been developed using deep-eutectic solvents, such as choline chloride and N,N-dimethylurea, to form iron, manganese and cobalt phosphates with a zeotype framework. Through this advanced method the successful synthesis of 4 previously undiscovered metal phosphate zeotypes was achieved. A careful control of water content during the ionothermal synthesis elucidated the multistep decomposition of our framework template and its impacts in the resulting zeotype structures. Upon conclusion of the ionothermal work, the focus shifted to the methodology development for mesoporous metal sulfides. An "oxide-to-sulfide" synthetic strategy was developed for the first time, resulting in the first synthesis of ordered porous iron, cobalt and nickel sulfides. More importantly, this is a general synthetic method, relying primarily on volumetric calculations per metal atom, which could be further extend to other metal-containing compounds, such as metal chalcogenides, phosphides, and nitrides. The second thrust was on the fundamental understanding of structural and electrochemical properties of nanocast mesoporous metal oxides. A thorough examination of three-dimensional porous TiO2 particles (solvothermal grown and micron in particle size) has been performed in order to achieve a better understanding of structure-property relationship. While ex-situ SEM analysis didn't show any notable change after the 1st discharge, significant structural alterations have occurred during the 2nd discharge. This formation coincides with a significant drop in performance, and it appears through ex-situ PXRD that the phase conversion of anatase to Li-titanate, the essential mechanism for energy storage in this material, is no longer occurring. A detailed structure-property investigation of mesoporous beta-MnO 2 was also performed. Previously, it has been reported that the material experiences a 7% volume change during lithium intercalation/de-intercalation while still retaining its mesoscopic order. The large volume change and new assertions about mesoscale beta-MnO2 from atomistic models makes determining additional structure-property insight of great importance. The analysis, through ex-situ PXRD measurements and dQ/dV analysis of the battery cycles indicate that a complex structural rearrangement occurs during cycling. A rearrangement irreversibly occurred in the initial cycles of mesoporous beta-MnO 2, and a complex structural dynamics has been observed. The knowledge generated from this work may help the battery community better understand the irreversible structural evolution occurring in commercialized lithium manganese oxide electrode materials.

Impact of rewilding, species introductions and climate change on the structure and function of the Yukon boreal forest ecosystem.

PubMed

Boonstra, Rudy; Boutin, Stan; Jung, Thomas S; Krebs, Charles J; Taylor, Shawn

2018-03-01

Community and ecosystem changes are happening in the pristine boreal forest ecosystem of the Yukon for 2 reasons. First, climate change is affecting the abiotic environment (temperature, rainfall and growing season) and driving changes in plant productivity and predator-prey interactions. Second, simultaneously change is occurring because of mammal species reintroductions and rewilding. The key ecological question is the impact these faunal changes will have on trophic dynamics. Primary productivity in the boreal forest is increasing because of climatic warming, but plant species composition is unlikely to change significantly during the next 50-100 years. The 9-10-year population cycle of snowshoe hares will persist but could be reduced in amplitude if winter weather increases predator hunting efficiency. Small rodents have increased in abundance because of increased vegetation growth. Arctic ground squirrels have disappeared from the forest because of increased predator hunting efficiency associated with shrub growth. Reintroductions have occurred for 2 reasons: human reintroductions of large ungulates and natural recolonization of mammals and birds extending their geographic ranges. The deliberate rewilding of wood bison (Bison bison) and elk (Cervus canadensis) has changed the trophic structure of this boreal ecosystem very little. The natural range expansion of mountain lions (Puma concolor), mule deer (Odocoileus hemionus) and American marten (Martes americana) should have few ecosystem effects. Understanding potential changes will require long-term monitoring studies and experiments on a scale we rarely deem possible. Ecosystems affected by climate change, species reintroductions and human alteration of habitats cannot remain stable and changes will be critically dependent on food web interactions. © 2017 The Authors. Integrative Zoology published by International Society of Zoological Sciences, Institute of Zoology/Chinese Academy of Sciences and John Wiley & Sons Australia, Ltd.

Seasonal variations in the community structures of macrobenthic fauna and their health status in an estuarine bay, Gwangyang Bay in Korea

NASA Astrophysics Data System (ADS)

Seo, Jin-Young; An, Soon-Mo; Lim, Dhong-il; Choi, Jin-Woo

2017-09-01

Macrobenthic fauna in an estuarine Gwangyang Bay, southern Korean coast, were investigated to uncover recent variations in their community structures. In the study area, macrobenthic faunal communities were mainly composed of polychaete worms which were the most abundant faunal group with the highest values in species number and density, while mollusks accounted for the highest proportion in total biomass. There was no clear seasonal difference in species richness during the two year period of the investigation, but the mean density and biomass increased every spring and summer due to the mass recruitment of Theora fragilis. The Shannon's diversity index (H') was more than 2.0 during most sampling seasons and did not show any significant seasonal difference except for the data in August, 2011 when azoic conditions occurred. The community structures of macrobenthos in Gwangyang Bay did not show any remarkable change in the dominance of the two top dominant species, Scoletoma longifolia and Heteromastus filiformis, which abundantly occurred in all seasons, except for the abundance peaks associated with high occurrence of T. fragilis and Paraprionospio cordifolia, especially in spring and summer and in autumn, respectively. These fauna changes reflected the changes in the macrobenthic community health status in Gwangyang Bay, where stable conditions and a healthy status prevailed in winter, but a slightly disturbed status prevailed from spring to autumn.

Progressive changes in chromatin structure and DNA damage response signals in bone marrow and peripheral blood during myelomagenesis.

PubMed

Gkotzamanidou, M; Terpos, E; Bamia, C; Kyrtopoulos, S A; Sfikakis, P P; Dimopoulos, M A; Souliotis, V L

2014-05-01

The molecular pathways implicated in multiple myeloma (MM) development are rather unknown. We studied epigenetic and DNA damage response (DDR) signals at selected model loci (N-ras, p53, d-globin) in bone marrow plasma cells and peripheral blood mononuclear cells (PBMCs) from patients with monoclonal gammopathy of undetermined significance (MGUS; n=20), smoldering/asymptomatic MM (SMM; n=29) and MM (n=18), as well as in healthy control-derived PBMCs (n=20). In both tissues analyzed, a progressive, significant increase in the looseness of local chromatin structure, gene expression levels and DNA repair efficiency from MGUS to SMM and finally to MM was observed (all P<0.002). Following ex vivo treatment with melphalan, a gradual suppression of the apoptotic pathway occurred in samples collected at different stages of myelomagenesis, with the severity and duration of the inhibition of RNA synthesis, p53 phosphorylation at serine15 and induction of apoptosis being higher in MGUS than SMM and lowest in MM patients (all P<0.0103). Interestingly, for all endpoints analyzed, a strong correlation between plasma cells and corresponding PBMCs was observed (all P<0.0003). We conclude that progressive changes in chromatin structure, transcriptional activity and DDR pathways during myelomagenesis occur in malignant plasma cells and that these changes are also reflected in PBMCs.

Chondroprotection using naturally occurring mineral supplementation formula in degenerative osteoarthritis of the knees.

PubMed

Bansal, Himanshu; Bansal, Anupama; Agrawal, Diwaker; Singh, Dhananjay; Deb, Kaushik

2014-01-01

To evaluate the therapeutic and safety efficacy of a naturally occurring mineral supplementation in the treatment of symptomatic knee osteoarthritis (OA). A prospective, single centre, study of 50 patients aged 50 years and above with painful and radiological Osteoarthritis of knees was carried out for one year. Patients received 40 drops of naturally occurring commercially available mineral supplement concentrate mineral drops purportedly derived from the Great Salt Lake in Utah. Efficacy was objectively confirmed by evaluating changes in the thickness of articular cartilage, joint space width, synovial fluid analysis and subjectively by changes in WOMAC scores and 6 Minute pain-free Walking Distance. The composite WOMAC scores were significantly improved by 17.2 points from a mean of 52 at baseline by year end. 18 (41%) patients showed improvement of more than 100 feet for the pain free distance covered during a 6 minute walk at one year follow-up. Ultrasonologicaly, at one year cartilage thickness improved by at least 0.01 mm in 9 (21%) patients. Though radiologicallynone of patient showed increase in joint space it was noticed that only 2(4.6%) patients had decline of joint space width of more than 0.5 mm. Average cell count reduced to 205/microlitre from a value of 520/microlitre at the start of study suggesting that the mineral supplement used had structural efficacy. Clinically relevant, statistically significant symptomatic and statistically insignificant structural improvement occurred over 1 year period in patients receiving the naturally occurring mineral supplement. The protection of the joint cartilages from progressive degeneration during osteoarthritis by these supplements indicates towards a chondrocyte regenerative potential of this supplement. Such regeneration may occur through activation of tissue specific adult chondrocyte precursors or stem cells.

Analysis of asteroid (216) Kleopatra using dynamical and structural constraints

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hirabayashi, Masatoshi; Scheeres, Daniel J., E-mail: masatoshi.hirabayashi@colorado.edu

This paper evaluates a dynamically and structurally stable size for Asteroid (216) Kleopatra. In particular, we investigate two different failure modes: material shedding from the surface and structural failure of the internal body. We construct zero-velocity curves in the vicinity of this asteroid to determine surface shedding, while we utilize a limit analysis to calculate the lower and upper bounds of structural failure under the zero-cohesion assumption. Surface shedding does not occur at the current spin period (5.385 hr) and cannot directly initiate the formation of the satellites. On the other hand, this body may be close to structural failure;more » in particular, the neck may be situated near a plastic state. In addition, the neck's sensitivity to structural failure changes as the body size varies. We conclude that plastic deformation has probably occurred around the neck part in the past. If the true size of this body is established through additional measurements, this method will provide strong constraints on the current friction angle for the body.« less

LenVarDB: database of length-variant protein domains.

PubMed

Mutt, Eshita; Mathew, Oommen K; Sowdhamini, Ramanathan

2014-01-01

Protein domains are functionally and structurally independent modules, which add to the functional variety of proteins. This array of functional diversity has been enabled by evolutionary changes, such as amino acid substitutions or insertions or deletions, occurring in these protein domains. Length variations (indels) can introduce changes at structural, functional and interaction levels. LenVarDB (freely available at http://caps.ncbs.res.in/lenvardb/) traces these length variations, starting from structure-based sequence alignments in our Protein Alignments organized as Structural Superfamilies (PASS2) database, across 731 structural classification of proteins (SCOP)-based protein domain superfamilies connected to 2 730 625 sequence homologues. Alignment of sequence homologues corresponding to a structural domain is available, starting from a structure-based sequence alignment of the superfamily. Orientation of the length-variant (indel) regions in protein domains can be visualized by mapping them on the structure and on the alignment. Knowledge about location of length variations within protein domains and their visual representation will be useful in predicting changes within structurally or functionally relevant sites, which may ultimately regulate protein function. Non-technical summary: Evolutionary changes bring about natural changes to proteins that may be found in many organisms. Such changes could be reflected as amino acid substitutions or insertions-deletions (indels) in protein sequences. LenVarDB is a database that provides an early overview of observed length variations that were set among 731 protein families and after examining >2 million sequences. Indels are followed up to observe if they are close to the active site such that they can affect the activity of proteins. Inclusion of such information can aid the design of bioengineering experiments.

Sorbitol counteracts temperature- and chemical-induced denaturation of a recombinant α-amylase from alkaliphilic Bacillus sp. TS-23.

PubMed

Chi, Meng-Chun; Wu, Tai-Jung; Chen, Hsing-Ling; Lo, Huei-Fen; Lin, Long-Liu

2012-12-01

Enzymes are highly complex systems with a substantial degree of structural variability in their folded state. In the presence of cosolvents, fluctuations among vast numbers of folded and unfolded conformations occur via many different pathways; alternatively, certain conformations can be stabilized or destabilized. To understand the contribution of osmolytes to the stabilization of structural changes and enzymatic activity of a truncated Bacillus sp. TS-23 α-amylase (BACΔNC), we monitored amylolytic activity, circular dichroism, and fluorescence as a function of osmolytes. In the presence of trimethylamine N-oxide (TMAO) and sorbitol, BACΔNC activity was retained significantly at elevated temperatures. As compared to the control, the secondary structures of this enzyme were essentially conserved upon the addition of these two kinds of osmolytes. Fluorescence results revealed that the temperature-induced conformational change of BACΔNC was prevented by TMAO and sorbitol. However, glycerol did not provide profound protection against thermal denaturation of the enzyme. Sorbitol was further found to counteract guanidine hydrochloride- and SDS-induced denaturation of BACΔNC. Thus, some well-known naturally occurring osmolytes make a dominant contribution to the stabilization of BACΔNC.

Resonance between a Prolate and a Superprolate Structure of the 162Er Nucleus

PubMed Central

Pauling, Linus; Blethen, John

1974-01-01

Observed energy levels of 162Er from the normal state J = 0 to the excited rotational state J = 18 correspond to values of the moment of inertia and rotational frequency that indicate that a pronounced change in structure occurs at about J = 14. It is shown that the observed values agree well with the values calculated on the assumption that there is resonance between a more stable prolate structure with a core of two spherons and a less stable superprolate structure with a core of three spherons in line. PMID:16592173

Investigation of the Presence of Charge Order in Magnetite by Measurement of the Sprin Wave Spectrum

DOE Office of Scientific and Technical Information (OSTI.GOV)

McQueeny, R. J.; Yethiraj, Mohana; Montfrooij, W.

Inelastic neutron scattering results on magnetite (Fe{sub 3}O{sub 4}) show a large splitting in the acoustic spin wave branch, producing a 7 meV gap midway to the Brillouin zone boundary at q = (0,0,1/2) and {h_bar}{omega} = 43 meV. The splitting occurs below the Verwey transition temperature, where a metal-insulator transition occurs simultaneously with a structural transformation, supposedly caused by the charge ordering on the iron sublattice. The wavevector (0,0,1/2) corresponds to the superlattice peak in the low symmetry structure. The dependence of the magnetic superexchange on changes in the crystal structure and ionic configurations that occur below the Verweymore » transition affect the spin wave dispersion. To better understand the origin of the observed splitting, several Heisenberg models intended to reproduce the pair-wise variation of the magnetic superexchange arising from both small crystalline distortions and charge ordering were studied. None of the models studied predicts the observed splitting, whose origin may arise from charge-density wave formation or magnetoelastic coupling.« less

New perspectives on evolutionary medicine: the relevance of microevolution for human health and disease.

PubMed

Rühli, Frank Jakobus; Henneberg, Maciej

2013-04-29

Evolutionary medicine (EM) is a growing field focusing on the evolutionary basis of human diseases and their changes through time. To date, the majority of EM studies have used pure theories of hominin macroevolution to explain the present-day state of human health. Here, we propose a different approach by addressing more empirical and health-oriented research concerning past, current and future microevolutionary changes of human structure, functions and pathologies. Studying generation-to-generation changes of human morphology that occurred in historical times, and still occur in present-day populations under the forces of evolution, helps to explain medical conditions and warns clinicians that their current practices may influence future humans. Also, analyzing historic tissue specimens such as mummies is crucial in order to address the molecular evolution of pathogens, of the human genome, and their coadaptations.

Hydrogen–Deuterium Exchange and Mass Spectrometry Reveal the pH-Dependent Conformational Changes of Diphtheria Toxin T Domain

PubMed Central

2015-01-01

The translocation (T) domain of diphtheria toxin plays a critical role in moving the catalytic domain across the endosomal membrane. Translocation/insertion is triggered by a decrease in pH in the endosome where conformational changes of T domain occur through several kinetic intermediates to yield a final trans-membrane form. High-resolution structural studies are only applicable to the static T-domain structure at physiological pH, and studies of the T-domain translocation pathway are hindered by the simultaneous presence of multiple conformations. Here, we report the application of hydrogen–deuterium exchange mass spectrometry (HDX-MS) for the study of the pH-dependent conformational changes of the T domain in solution. Effects of pH on intrinsic HDX rates were deconvolved by converting the on-exchange times at low pH into times under our “standard condition” (pH 7.5). pH-Dependent HDX kinetic analysis of T domain clearly reveals the conformational transition from the native state (W-state) to a membrane-competent state (W+-state). The initial transition occurs at pH 6 and includes the destabilization of N-terminal helices accompanied by the separation between N- and C-terminal segments. The structural rearrangements accompanying the formation of the membrane-competent state expose a hydrophobic hairpin (TH8–9) to solvent, prepare it to insert into the membrane. At pH 5.5, the transition is complete, and the protein further unfolds, resulting in the exposure of its C-terminal hydrophobic TH8–9, leading to subsequent aggregation in the absence of membranes. This solution-based study complements high resolution crystal structures and provides a detailed understanding of the pH-dependent structural rearrangement and acid-induced oligomerization of T domain. PMID:25290210

Hydrogen-deuterium exchange and mass spectrometry reveal the pH-dependent conformational changes of diphtheria toxin T domain.

PubMed

Li, Jing; Rodnin, Mykola V; Ladokhin, Alexey S; Gross, Michael L

2014-11-04

The translocation (T) domain of diphtheria toxin plays a critical role in moving the catalytic domain across the endosomal membrane. Translocation/insertion is triggered by a decrease in pH in the endosome where conformational changes of T domain occur through several kinetic intermediates to yield a final trans-membrane form. High-resolution structural studies are only applicable to the static T-domain structure at physiological pH, and studies of the T-domain translocation pathway are hindered by the simultaneous presence of multiple conformations. Here, we report the application of hydrogen-deuterium exchange mass spectrometry (HDX-MS) for the study of the pH-dependent conformational changes of the T domain in solution. Effects of pH on intrinsic HDX rates were deconvolved by converting the on-exchange times at low pH into times under our "standard condition" (pH 7.5). pH-Dependent HDX kinetic analysis of T domain clearly reveals the conformational transition from the native state (W-state) to a membrane-competent state (W(+)-state). The initial transition occurs at pH 6 and includes the destabilization of N-terminal helices accompanied by the separation between N- and C-terminal segments. The structural rearrangements accompanying the formation of the membrane-competent state expose a hydrophobic hairpin (TH8-9) to solvent, prepare it to insert into the membrane. At pH 5.5, the transition is complete, and the protein further unfolds, resulting in the exposure of its C-terminal hydrophobic TH8-9, leading to subsequent aggregation in the absence of membranes. This solution-based study complements high resolution crystal structures and provides a detailed understanding of the pH-dependent structural rearrangement and acid-induced oligomerization of T domain.

Simple shearing flow of dry soap foams with TCP structure[Tetrahedrally Close-Packed

DOE Office of Scientific and Technical Information (OSTI.GOV)

REINELT,DOUGLAS A.; KRAYNIK,ANDREW M.

2000-02-16

The microrheology of dry soap foams subjected to large, quasistatic, simple shearing deformations is analyzed. Two different monodisperse foams with tetrahedrally close-packed (TCP) structure are examined: Weaire-Phelan (A15) and Friauf-Laves (C15). The elastic-plastic response is evaluated by calculating foam structures that minimize total surface area at each value of strain. The minimal surfaces are computed with the Surface Evolver program developed by Brakke. The foam geometry and macroscopic stress are piecewise continuous functions of strain. The stress scales as T/V{sup 1/3} where T is surface tension and V is cell volume. Each discontinuity corresponds to large changes in foam geometrymore » and topology that restore equilibrium to unstable configurations that violate Plateau's laws. The instabilities occur when the length of an edge on a polyhedral foam cell vanishes. The length can tend to zero smoothly or abruptly with strain. The abrupt case occurs when a small increase in strain changes the energy profile in the neighborhood of a foam structure from a local minimum to a saddle point, which can lead to symmetry-breaking bifurcations. In general, the new foam topology associated with each stable solution branch results from a cascade of local topology changes called T1 transitions. Each T1 cascade produces different cell neighbors, reduces surface energy, and provides an irreversible, film-level mechanism for plastic yield behavior. Stress-strain curves and average stresses are evaluated by examining foam orientations that admit strain-periodic behavior. For some orientations, the deformation cycle includes Kelvin cells instead of the original TCP structure; but the foam does not remain perfectly ordered. Bifurcations during subsequent T1 cascades lead to disorder and can even cause strain localization.« less

Redox-dependent structure change and hyperfine nuclear magnetic resonance shifts in cytochrome c

DOE Office of Scientific and Technical Information (OSTI.GOV)

Feng, Yiquing; Roder, H.; Englander, S.W.

1990-04-10

Proton nuclear magnetic resonance assignments for reduced and oxidized equine cytochrome c show that many individual protons exhibit different chemical shifts in the two protein forms, reflecting diamagnetic shift effects due to structure change, and in addition contact and pseudocontact shifts that occur only in the paramagnetic oxidized form. To evaluate the chemical shift differences for structure change, the authors removed the pseudocontact shift contribution by a calculation based on knowledge of the electron spin g tensor. The g-tensor calculation, when repeated using only 12 available C{sub {alpha}}H proton resonances for cytochrom c from tuna, proved to be remarkably stable.more » The derived g tensor was then used together with spatial coordinates for the oxidized form to calculate the pseudocontact shift contribution to proton resonances at 400 identifiable sites throughout the protein, so that the redox-dependent chemical shift discrepancy, could be evaluated. Large residual changes in chemical shift define the Fermi contact shifts, where are found as expected to be limited to the immediate covalent structure of the heme and its ligands and to be asymmetrically distributed over the heme. The chemical shift discrepancies observed appear in the main to reflect structure-dependent diamagnetic shifts rather than hyperfine effects due to displacements in the pseudocontact shift field. Although 51 protons in 29 different residues exhibit significant chemical shift changes, the general impressions one of small structural adjustments to redox-dependent strain rather than sizeable structural displacements or rearrangements.« less

High pressure polymorphs and amorphization of upconversion host material NaY(WO 4) 2

DOE PAGES

Hong, Fang; Yue, Binbin; Cheng, Zhenxiang; ...

2016-07-29

The pressure effect on the structural change of upconversion host material NaY(WO 4) 2 was studied in this paper by using in-situ synchrotron X-ray diffraction. A transition from the initial scheelite phase to the M-fergusonite phase occurs near 10 GPa, and another phase transition is found near 27.5 GPa, which could be an isostructural transition without symmetry change. The sample becomes amorphous when the pressure is fully released from high pressure. Finally, this work demonstrates the possibility of synthesizing various polymorph structures for non-linear optical applications with a high pressure, chemical doping, or strained thin-film nanostructure process.

In Operando XRD and TXM Study on the Metastable Structure Change of NaNi 1/3Fe 1/3Mn 1/3O 2 under Electrochemical Sodium-Ion Intercalation

DOE PAGES

Xie, Yingying; Wang, Hong; Xu, Guiliang; ...

2016-09-02

In operando XRD and TXM-XANES approaches demonstrate that structure evolution in NaNi 1/3Fe 1/3Mn 1/3O 2 during cycling follows a continuous change, and the formation of a nonequilibrium solid solution phase in the existence of two phases. Here, an O3' and P3' monoclinic phase occur, and redox couples of Ni 3+/Ni 4+ and Fe 3+/Fe 4+ are mainly responsible in the charge voltage range from 4.0 to 4.3 V.

Magnetostructural phase transformations in Tb 1-x Mn 2

DOE PAGES

Zou, Junding; Paudyal, Durga; Liu, Jing; ...

2015-01-16

Magnetism and phase transformations in non-stoichiometric Tb 1-xMn 2 (x = 0.056, 0.039) have been studied as functions of temperature and magnetic field using magnetization, heat capacity, and X-ray powder diffraction measurements. Lowering the temperature, the compounds sequentially order ferrimagnetically and antiferromagnetically, and finally, exhibit spin reorientation transitions. Moreover, these structural distortions from room temperature cubic to low temperature rhombohedral structures occur at T N, and are accompanied by large volume changes reaching ~-1.27% and -1.42%, respectively. First principles electronic structure calculations confirm the phase transformation from the ferrimagnetic cubic structure to the antiferromagnetic rhombohedral structure in TbMn 2.

Competition in size-structured populations: mechanisms inducing cohort formation and population cycles.

PubMed

de Roos, André M; Persson, Lennart

2003-02-01

In this paper we investigate the consequences of size-dependent competition among the individuals of a consumer population by analyzing the dynamic properties of a physiologically structured population model. Only 2 size-classes of individuals are distinguished: juveniles and adults. Juveniles and adults both feed on one and the same resource and hence interact by means of exploitative competition. Juvenile individuals allocate all assimilated energy into development and mature on reaching a fixed developmental threshold. The combination of this fixed threshold and the resource-dependent developmental rate, implies that the juvenile delay between birth and the onset of reproduction may vary in time. Adult individuals allocate all assimilated energy to reproduction. Mortality of both juveniles and adults is assumed to be inversely proportional to the amount of energy assimilated. In this setting we study how the dynamics of the population are influenced by the relative foraging capabilities of juveniles and adults. In line with results that we previously obtained in size-structured consumer-resource models with pulsed reproduction, population cycles primarily occur when either juveniles or adults have a distinct competitive advantage. When adults have a larger per capita feeding rate and are hence competitively superior to juveniles, population oscillations occur that are primarily induced by the fact that the duration of the juvenile period changes with changing food conditions. These cycles do not occur when the juvenile delay is a fixed parameter. When juveniles are competitively superior, two different types of population fluctuations can occur: (1) rapid, low-amplitude fluctuations having a period of half the juvenile delay and (2) slow, large-amplitude fluctuations characterized by a period, which is roughly equal to the juvenile delay. The analysis of simplified versions of the structured model indicates that these two types of oscillations also occur if mortality and/or development is independent of food density, i.e. in a situation with a constant juvenile developmental delay and a constant, food-independent background mortality. Thus, the oscillations that occur when juveniles are more competitive are induced by the juvenile delay per se. When juveniles exert a larger foraging pressure on the shared resource, maturation implies an increase not only in adult density, but also in food density and consequently fecundity. Our analysis suggests that this correlation in time between adult density and fecundity is crucial for the occurrence of population cycles when juveniles are competitively superior.

Multiscale spatial and small-scale temporal variation in the composition of Riverine fish communities.

PubMed

Growns, Ivor; Astles, Karen; Gehrke, Peter

2006-03-01

We studied the multiscale (sites, river reaches and rivers) and short-term temporal (monthly) variability in a freshwater fish assemblage. We found that small-scale spatial variation and short-term temporal variability significantly influenced fish community structure in the Macquarie and Namoi Rivers. However, larger scale spatial differences between rivers were the largest source of variation in the data. The interaction between temporal change and spatial variation in fish community structure, whilst statistically significant, was smaller than the variation between rivers. This suggests that although the fish communities within each river changed between sampling occasions, the underlying differences between rivers were maintained. In contrast, the strongest interaction between temporal and spatial effects occurred at the smallest spatial scale, at the level of individual sites. This means whilst the composition of the fish assemblage at a given site may fluctuate, the magnitude of these changes is unlikely to affect larger scale differences between reaches within rivers or between rivers. These results suggest that sampling at any time within a single season will be sufficient to show spatial differences that occur over large spatial scales, such as comparisons between rivers or between biogeographical regions.

7 CFR 3300.43 - Application for approval.

Code of Federal Regulations, 2011 CFR

2011-01-01

... tests of mechanical refrigerating appliances according to subpart D of this rule. (d) A general... laboratory of a mechanical refrigerating appliance for a Class “C” mechanically refrigerated container or... significant change occur in the facility with respect to structure or test equipment as a result of redesign...

7 CFR 3300.43 - Application for approval.

Code of Federal Regulations, 2012 CFR

2012-01-01

... tests of mechanical refrigerating appliances according to subpart D of this rule. (d) A general... laboratory of a mechanical refrigerating appliance for a Class “C” mechanically refrigerated container or... significant change occur in the facility with respect to structure or test equipment as a result of redesign...

7 CFR 3300.43 - Application for approval.

Code of Federal Regulations, 2013 CFR

2013-01-01

... tests of mechanical refrigerating appliances according to subpart D of this rule. (d) A general... laboratory of a mechanical refrigerating appliance for a Class “C” mechanically refrigerated container or... significant change occur in the facility with respect to structure or test equipment as a result of redesign...

7 CFR 3300.43 - Application for approval.

Code of Federal Regulations, 2014 CFR

2014-01-01

... tests of mechanical refrigerating appliances according to subpart D of this rule. (d) A general... laboratory of a mechanical refrigerating appliance for a Class “C” mechanically refrigerated container or... significant change occur in the facility with respect to structure or test equipment as a result of redesign...

7 CFR 3300.43 - Application for approval.

Code of Federal Regulations, 2010 CFR

2010-01-01

... tests of mechanical refrigerating appliances according to subpart D of this rule. (d) A general... laboratory of a mechanical refrigerating appliance for a Class “C” mechanically refrigerated container or... significant change occur in the facility with respect to structure or test equipment as a result of redesign...

NATURAL AND ANTHROPOGENIC FACTORS INFLUENCING FOOD WEB STRUCTURE IN GREAT LAKES COASTAL WETLANDS

EPA Science Inventory

We are investigating factors governing the biological organization of Great Lakes coastal wetlands. Food web analyses using stable isotope techniques verify the role of algae as an energetic foundation, and also suggest that fundamental changes occur as a result of anthropogenic ...

Use of Topical PC-NSAIDs to Treat Burn Injury and Pain

DTIC Science & Technology

2016-08-01

burn injury, biochemical changes which occur during the burn injury process was analyzed with myeloperoxidase (MPO) activity. MPO is an enzyme known... denatured but overall, it is quite healthy. (Fig.5 right) Fluorescence probing also reveals healthy looking cells and structures. Hair follicles, vessels

Rheological changes of polyamide 12 under oscillatory shear

NASA Astrophysics Data System (ADS)

Mielicki, C.; Gronhoff, B.; Wortberg, J.

2014-05-01

Changes in material properties as well as process deviation prevent Laser Sintering (LS) technology from manufacturing of quality assured parts in a series production. In this context, the viscosity of Polyamide 12 (PA12) is assumed to possess the most significant influence, as it determines the sintering velocity, the resistance towards melt formation and the bonding strength of sintered layers. Moreover, the viscosity is directly related to the structure of the molten polymer. In particular, it has been recently reported that LS process conditions lead to structural changes of PA12 affecting viscosity and coalescence of adjacent polymer particles, i.e. melt formation significantly. Structural change of PA12 was understood as a post condensation. Its influence on viscosity was described by a time and temperature depending rheological model whereas time dependence was considered by a novel structural change shift factor which was derived from melt volume rate data. In combination with process data that was recorded using online thermal imaging, the model is suitable to control the viscosity (processability of the material) as result of material and process properties. However, as soon as laser energy is exposed to the powder bed PA12 undergoes a phase transition from solid to molten state. Above the melting point, structural change is expected to occur faster due to a higher kinetic energy and free volume of the molten polymer. Oscillatory shear results were used to study the influence of aging time and for validation of the novel structural change shift factor and its model parameters which were calibrated based on LS processing condition.

Mesozoic to Cenozoic tectonic transition process in Zhanhua Sag, Bohai Bay Basin, East China

NASA Astrophysics Data System (ADS)

Cheng, Yanjun; Wu, Zhiping; Lu, Shunan; Li, Xu; Lin, Chengyan; Huang, Zheng; Su, Wen; Jiang, Chao; Wang, Shouye

2018-04-01

The Zhanhua sag is part of the Bohai Bay intracontinental basin system that has developed since the Mesozoic in East China. The timing of this basin system coincides with the final assembly of East Asia and the development of Western Pacific-type plate margin. Here we use 3-D seismic and core log data to investigate the evolution of this basin and discuss its broad tectonic settings. Our new structural study of Zhanhua sag suggests that there are four major tectonic transitions occurred in the Bohai Bay Basin during Mesozoic and Cenozoic: (1) The first tectonic transition was from stable Craton to thrusting during the Triassic, mainly caused by the South China Block's subduction northward beneath the North China Block, which induced the formation of the NW-striking thrust faults. (2) The second tectonic transition was mainly characterized by a change from compression to extension, which can be further divided into two-stages. At the first stage, two episodes of NW-SE shortening occurred in East Asia during Early-Middle Jurassic and Late Jurassic-earliest Cretaceous, respectively. At the second stage, the extension and left-lateral shearing took place during Early Cretaceous while compression occurred during Late Cretaceous. The NW-striking thrust faults changed to normal faults and the NNE-striking left-lateral strike-slip faults started to influence the eastern part of the basin. (3) The third transition occurred when the NW-SE extension and NNE-striking right-lateral shearing started to form during Paleogene, and the peak deformation happen around 40 Ma due to the change of the subduction direction of Pacific Plate relative to Eurasia Plate. The NE-striking normal faults are the main structure, and the pre-existing NNE-striking strike-slip faults changed from left-lateral to right-lateral. (4) The fourth transition saw the regional subsidence during Neogene, which was probably caused by the India-Asia "Hard collision" between 25 and 20 Ma.

Climate-mediated changes in zooplankton community structure for the eastern Bering Sea

NASA Astrophysics Data System (ADS)

Eisner, Lisa B.; Napp, Jeffrey M.; Mier, Kathryn L.; Pinchuk, Alexei I.; Andrews, Alexander G.

2014-11-01

Zooplankton are critical to energy transfer between higher and lower trophic levels in the eastern Bering Sea ecosystem. Previous studies from the southeastern Bering Sea shelf documented substantial differences in zooplankton taxa in the Middle and Inner Shelf Domains between warm and cold years. Our investigation expands this analysis into the northern Bering Sea and the south Outer Domain, looking at zooplankton community structure during a period of climate-mediated, large-scale change. Elevated air temperatures in the early 2000s resulted in regional warming and low sea-ice extent in the southern shelf whereas the late 2000s were characterized by cold winters, extensive spring sea ice, and a well-developed pool of cold water over the entire Middle Domain. The abundance of large zooplankton taxa such as Calanus spp. (C. marshallae and C. glacialis), and Parasagitta elegans, increased from warm to cold periods, while the abundance of gelatinous zooplankton (Cnidaria) and small taxa decreased. Biomass followed the same trends as abundance, except that the biomass of small taxa in the southeastern Bering Sea remained constant due to changes in abundance of small copepod taxa (increases in Acartia spp. and Pseudocalanus spp. and decreases in Oithona spp.). Statistically significant changes in zooplankton community structure and individual species were greatest in the Middle Domain, but were evident in all shelf domains, and in both the northern and southern portions of the eastern shelf. Changes in community structure did not occur abruptly during the transition from warm to cold, but seemed to begin gradually and build as the influence of the sea ice and cold water temperatures persisted. The change occurred one year earlier in the northern than the southern Middle Shelf. These and previous observations demonstrate that lower trophic levels within the eastern Bering Sea respond to climate-mediated changes on a variety of time scales, including those shorter than the commonly accepted quasi-decadal time periods. This lack of resilience or inertia at the lowest trophic levels affects production at higher trophic levels and must be considered in management strategy evaluations of living marine resources.

Allosteric Ligand Binding and Anisotropic Energy Flow in Albumin

NASA Astrophysics Data System (ADS)

Dyer, Brian

2014-03-01

Protein allostery usually involves propagation of local structural changes through the protein to a remote site. Coupling of structural changes at remote sites is thought to occur through anisotropic energy transport, but the nature of this process is poorly understood. We have studied the relationship between allosteric interactions of remote ligand binding sites of the protein and energy flow through the structure of bovine serum albumin (BSA). We applied ultrafast infrared spectroscopy to probe the flow of energy through the protein backbone following excitation of a heater dye, a metalloporphyrin or malachite green, bound to different binding sites in the protein. We observe ballistic flow through the protein structure following input of thermal energy into the flexible ligand binding sites. We also observe anisotropic heat flow through the structure, without local heating of the rigid helix bundles that connect these sites. We will discuss the implications of this efficient energy transport mechanism with regard to the allosteric propagation of binding energy through the connecting helix structures.

Ultrashort Pulse Inscription of Photonic Structures in ZnSe and GaAs for Mid Infrared Applications

DTIC Science & Technology

2010-08-01

structure shown in Figure 2 is an example of a type I waveguide where guiding occurs in the modified region created at the focus of the fabrication beam...turn produces a refractive index change. The end facet cross sections of type I and type II waveguide structures are illustrated below in Figure 2 and...and E. Mazur, Meas. Sci. Technol. 12, 1784 (2001). 4) A. G. Okhrimchuk, V. K. Mezentsev, H. Schmitz, M. Dubov, and I . Bennion, Laser Phys. 19 1415

Prevalent Exon-Intron Structural Changes in the APETALA1/FRUITFULL, SEPALLATA, AGAMOUS-LIKE6, and FLOWERING LOCUS C MADS-Box Gene Subfamilies Provide New Insights into Their Evolution

PubMed Central

Yu, Xianxian; Duan, Xiaoshan; Zhang, Rui; Fu, Xuehao; Ye, Lingling; Kong, Hongzhi; Xu, Guixia; Shan, Hongyan

2016-01-01

AP1/FUL, SEP, AGL6, and FLC subfamily genes play important roles in flower development. The phylogenetic relationships among them, however, have been controversial, which impedes our understanding of the origin and functional divergence of these genes. One possible reason for the controversy may be the problems caused by changes in the exon-intron structure of genes, which, according to recent studies, may generate non-homologous sites and hamper the homology-based sequence alignment. In this study, we first performed exon-by-exon alignments of these and three outgroup subfamilies (SOC1, AG, and STK). Phylogenetic trees reconstructed based on these matrices show improved resolution and better congruence with species phylogeny. In the context of these phylogenies, we traced evolutionary changes of exon-intron structures in each subfamily. We found that structural changes have occurred frequently following gene duplication and speciation events. Notably, exons 7 and 8 (if present) suffered more structural changes than others. With the knowledge of exon-intron structural changes, we generated more reasonable alignments containing all the focal subfamilies. The resulting trees showed that the SEP subfamily is sister to the monophyletic group formed by AP1/FUL and FLC subfamily genes and that the AGL6 subfamily forms a sister group to the three abovementioned subfamilies. Based on this topology, we inferred the evolutionary history of exon-intron structural changes among different subfamilies. Particularly, we found that the eighth exon originated before the divergence of AP1/FUL, FLC, SEP, and AGL6 subfamilies and degenerated in the ancestral FLC-like gene. These results provide new insights into the origin and evolution of the AP1/FUL, FLC, SEP, and AGL6 subfamilies. PMID:27200066

Photonic Crystal Structures with Tunable Structure Color as Colorimetric Sensors

PubMed Central

Wang, Hui; Zhang, Ke-Qin

2013-01-01

Colorimetric sensing, which transduces environmental changes into visible color changes, provides a simple yet powerful detection mechanism that is well-suited to the development of low-cost and low-power sensors. A new approach in colorimetric sensing exploits the structural color of photonic crystals (PCs) to create environmentally-influenced color-changeable materials. PCs are composed of periodic dielectrics or metallo-dielectric nanostructures that affect the propagation of electromagnetic waves (EM) by defining the allowed and forbidden photonic bands. Simultaneously, an amazing variety of naturally occurring biological systems exhibit iridescent color due to the presence of PC structures throughout multi-dimensional space. In particular, some kinds of the structural colors in living organisms can be reversibly changed in reaction to external stimuli. Based on the lessons learned from natural photonic structures, some specific examples of PCs-based colorimetric sensors are presented in detail to demonstrate their unprecedented potential in practical applications, such as the detections of temperature, pH, ionic species, solvents, vapor, humidity, pressure and biomolecules. The combination of the nanofabrication technique, useful design methodologies inspired by biological systems and colorimetric sensing will lead to substantial developments in low-cost, miniaturized and widely deployable optical sensors. PMID:23539027

Complement activation on B lymphocytes opsonized with rituximab or ofatumumab produces substantial changes in membrane structure preceding cell lysis.

PubMed

Beum, Paul V; Lindorfer, Margaret A; Beurskens, Frank; Stukenberg, P Todd; Lokhorst, Henk M; Pawluczkowycz, Andrew W; Parren, Paul W H I; van de Winkel, Jan G J; Taylor, Ronald P

2008-07-01

Binding of the CD20 mAb rituximab (RTX) to B lymphocytes in normal human serum (NHS) activates complement (C) and promotes C3b deposition on or in close proximity to cell-bound RTX. Based on spinning disk confocal microscopy analyses, we report the first real-time visualization of C3b deposition and C-mediated killing of RTX-opsonized B cells. C activation by RTX-opsonized Daudi B cells induces rapid membrane blebbing and generation of long, thin structures protruding from cell surfaces, which we call streamers. Ofatumumab, a unique mAb that targets a distinct binding site (the small loop epitope) of the CD20 Ag, induces more rapid killing and streaming on Daudi cells than RTX. In contrast to RTX, ofatumumab promotes streamer formation and killing of ARH77 cells and primary B cells from patients with chronic lymphocytic leukemia. Generation of streamers requires C activation; no streaming occurs in media, NHS-EDTA, or in sera depleted of C5 or C9. Streamers can be visualized in bright field by phase imaging, and fluorescence-staining patterns indicate they contain membrane lipids and polymerized actin. Streaming also occurs if cells are reacted in medium with bee venom melittin, which penetrates cells and forms membrane pores in a manner similar to the membrane-attack complex of C. Structures similar to streamers are demonstrable when Ab-opsonized sheep erythrocytes (non-nucleated cells) are reacted with NHS. Taken together, our findings indicate that the membrane-attack complex is a key mediator of streaming. Streamer formation may, thus, represent a membrane structural change that can occur shortly before complement-induced cell death.

Maturation of Cortico-Subcortical Structural Networks-Segregation and Overlap of Medial Temporal and Fronto-Striatal Systems in Development.

PubMed

Walhovd, Kristine B; Tamnes, Christian K; Bjørnerud, Atle; Due-Tønnessen, Paulina; Holland, Dominic; Dale, Anders M; Fjell, Anders M

2015-07-01

The brain consists of partly segregated neural circuits within which structural convergence and functional integration occurs during development. The relationship of structural cortical and subcortical maturation is largely unknown. We aimed to study volumetric development of the hippocampus and basal ganglia (caudate, putamen, pallidum, accumbens) in relation to volume changes throughout the cortex. Longitudinal MRI data were obtained across a mean interval of 2.6 years in 85 participants with an age range of 8-19 years at study start. Left and right subcortical changes were related to cortical change vertex-wise in the ipsilateral hemisphere with general linear models with age, sex, interval between scans, and mean cortical volume change as covariates. Hippocampal-cortical change relationships centered on parts of the Papez circuit, including entorhinal, parahippocampal, and isthmus cingulate areas, and lateral temporal, insular, and orbitofrontal cortices in the left hemisphere. Basal ganglia-cortical change relationships were observed in mostly nonoverlapping and more anterior cortical areas, all including the anterior cingulate. Other patterns were unique to specific basal ganglia structures, including pre-, post-, and paracentral patterns relating to putamen change. In conclusion, patterns of cortico-subcortical development as assessed by morphometric analyses in part map out segregated neural circuits at the macrostructural level. © The Author 2014. Published by Oxford University Press. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.

Public health in transition: views of the specialist workforce.

PubMed

Griffiths, Sian; Thorpe, Allison

2007-09-01

The constant structural changes to the NHS in England have created instability and lack of job security within the public health workforce in the U.K. Since posts are linked to structures which keep changing, recent years have seen constant changes in titles, responsibilities and expectations. Effective public health practice involves teamwork across sectors and strong relationships with local communities, and this constant change has posed professional challenges. The changes in 2002 offered the Faculty of Public Health the opportunity to work with the Department of Health to consult with specialists, the main objective being to reach agreement on future roles and ways of working. The lessons learnt from this exercise are described here as they remain relevant as the structural changes continue. Key messages are that if the many opportunities of the current policy agenda are to be realized, the public health profession needs to be supported to play its full role in the three domains of practice: health improvement, health protection and developing better health services. This challenge needs professional bodies to be clear on expected competence of their members; employers to be clear on the potential contribution of public health specialists not only in promoting and protecting health in communities but also within the acute sector; organizational arrangements to be in place to sustain the capacity of the workforce whatever the structural changes occurring. This lesson has yet to be learnt.

Effects of long- and short-term management on the functional structure of meadows through species turnover and intraspecific trait variability.

PubMed

Volf, Martin; Redmond, Conor; Albert, Ágnes J; Le Bagousse-Pinguet, Yoann; Biella, Paolo; Götzenberger, Lars; Hrázský, Záboj; Janeček, Štěpán; Klimešová, Jitka; Lepš, Jan; Šebelíková, Lenka; Vlasatá, Tereza; de Bello, Francesco

2016-04-01

The functional structures of communities respond to environmental changes by both species replacement (turnover) and within-species variation (intraspecific trait variability; ITV). Evidence is lacking on the relative importance of these two components, particularly in response to both short- and long-term environmental disturbance. We hypothesized that such short- and long-term perturbations would induce changes in community functional structure primarily via ITV and turnover, respectively. To test this we applied an experimental design across long-term mown and abandoned meadows, with each plot containing a further level of short-term management treatments: mowing, grazing and abandonment. Within each plot, species composition and trait values [height, shoot biomass, and specific leaf area (SLA)] were recorded on up to five individuals per species. Positive covariations between the contribution of species turnover and ITV occurred for height and shoot biomass in response to both short- and long-term management, indicating that species turnover and intraspecific adjustments selected for similar trait values. Positive covariations also occurred for SLA, but only in response to long-term management. The contributions of turnover and ITV changed depending on both the trait and management trajectory. As expected, communities responded to short-term disturbances mostly through changes in intraspecific trait variability, particularly for height and biomass. Interestingly, for SLA they responded to long-term disturbances by both species turnover and intraspecific adjustments. These findings highlight the importance of both ITV and species turnover in adjusting grassland functional trait response to environmental perturbation, and show that the response is trait specific and affected by disturbance regime history.

Multi-decadal analysis reveals contrasting patterns of resilience and decline in coral assemblages

NASA Astrophysics Data System (ADS)

Tanner, Jason E.

2017-12-01

A 50-yr study of coral dynamics at Heron Island, on Australia's Great Barrier Reef, shows that community change on a single reef is highly variable and that while some areas of the reef are in decline, others are recovering well 40 yr after a major cyclonic disturbance that eliminated all corals in the study plot. At one site, the genus-level composition in 2012 was identical to that before the cyclone, although it took around 30 yr to recover, and there were still differences at the species level. The colony size structure of some species at this site, notably the dominant Acropora digitifera, which had over 40% cover in 2012, also recovered after 30 yr, although sub-dominant species still lacked large colonies even after 40 yr. Given the small scale of the individual study plots (1 m2), this shows an unexpected degree of determinism in assemblage structure. At a second site, however, both composition and size structure changed dramatically over the last 40 yr of the study as both external and internal factors altered local environmental conditions. At both sites, major changes in composition appear to be related to drying out of the reef crest due to changes in flow regimes and/or natural accretion. At the site that has recovered, erosion has reversed this drying out, whereas no such erosion has occurred at the second site. If such erosion occurs, or sea levels increase due to global warming, then the second site may also prove to be resilient over decadal time scales.

The application of Fourier transform infrared microspectroscopy for the study of diseased central nervous system tissue.

PubMed

Caine, Sally; Heraud, Philip; Tobin, Mark J; McNaughton, Donald; Bernard, Claude C A

2012-02-15

In the last two decades the field of infrared spectroscopy has seen enormous advances in both instrumentation and the development of bioinformatic methods for spectral analysis, allowing the examination of a large variety of healthy and diseased samples, including biological fluids, isolated cells, whole tissues, and tissue sections. The non-destructive nature of the technique, together with the ability to directly probe biochemical changes without the addition of stains or contrast agents, enables a range of complementary analyses. This review focuses on the application of Fourier transform infrared (FTIR) microspectroscopy to analyse central nervous system tissues, with the aim of understanding the biochemical and structural changes associated with neurodegenerative diseases such as Alzheimer's disease, Parkinson's disease, transmissible spongiform encephalopathies, multiple sclerosis, as well as brain tumours. Modern biospectroscopic methods that combine FTIR microspectroscopy with bioinformatic analysis constitute a powerful new methodology that can discriminate pathology from normal healthy tissue in a rapid, unbiased fashion, with high sensitivity and specificity. Notably, the ability to detect protein secondary structural changes associated with Alzheimer's plaques, neurons in Parkinson's disease, and in some spectra from meningioma, as well as in the animal models of Alzheimer's disease, transmissible spongiform encephalopathies, and multiple sclerosis, illustrates the power of this technology. The capacity to offer insight into the biochemical and structural changes underpinning aetio-pathogenesis of diseases in tissues provides both a platform to investigate early pathologies occurring in a variety of experimentally induced and naturally occurring central nervous system diseases, and the potential to evaluate new therapeutic approaches. Copyright © 2011 Elsevier Inc. All rights reserved.

Tropical specialist vs. climate generalist: Diversification and demographic history of sister species of Carlia skinks from northwestern Australia.

PubMed

Afonso Silva, Ana C; Bragg, Jason G; Potter, Sally; Fernandes, Carlos; Coelho, Maria Manuela; Moritz, Craig

2017-08-01

Species endemic to the tropical regions are expected to be vulnerable to future climate change due in part to their relatively narrow climatic niches. In addition, these species are more likely to have responded strongly to past climatic change, and this can be explored through phylogeographic analyses. To test the hypothesis that tropical specialists are more sensitive to climate change than climate generalists, we generated and analyse sequence data from mtDNA and ~2500 exons to compare scales of historical persistence and population fluctuation in two sister species of Australian rainbow skinks: the tropical specialist Carlia johnstonei and the climate generalist C. triacantha. We expect the tropical specialist species to have deeper and finer-scale phylogeographic structure and stronger demographic fluctuations relative to the closely related climate generalist species, which should have had more stable populations through periods of harsh climate in the late Quaternary. Within C. johnstonei, we find that some populations from the northern Kimberley islands are highly divergent from mainland populations. In C. triacantha, one major clade occurs across the deserts and into the mesic Top End, and another occurs primarily in the Kimberley with scattered records eastwards. Where their ranges overlap in the Kimberley, both mitochondrial DNA and nuclear DNA suggest stronger phylogeographic structure and range expansion within the tropical specialist, whereas the climate generalist has minimal structuring and no evidence of recent past range expansion. These results are consistent with the hypothesis that tropical specialists are more sensitive to past climatic change. © 2017 John Wiley & Sons Ltd.

Structural and spectroscopic changes to natural nontronite induced by experimental impacts between 10 and 40 GPa

NASA Astrophysics Data System (ADS)

Friedlander, Lonia R.; Glotch, Timothy D.; Bish, David L.; Dyar, M. Darby; Sharp, Thomas G.; Sklute, Elizabeth C.; Michalski, Joseph R.

2015-05-01

Many phyllosilicate deposits remotely detected on Mars occur within bombarded terrains. Shock metamorphism from meteor impacts alters mineral structures, producing changed mineral spectra. Thus, impacts have likely affected the spectra of remotely sensed Martian phyllosilicates. We present spectral analysis results for a natural nontronite sample before and after laboratory-generated impacts over five peak pressures between 10 and 40 GPa. We conducted a suite of spectroscopic analyses to characterize the sample's impact-induced structural and spectral changes. Nontronite becomes increasingly disordered with increasing peak impact pressure. Every infrared spectroscopic technique used showed evidence of structural changes at shock pressures above ~25 GPa. Reflectance spectroscopy in the visible near-infrared region is primarily sensitive to the vibrations of metal-OH and interlayer H2O groups in the nontronite octahedral sheet. Midinfrared (MIR) spectroscopic techniques are sensitive to the vibrations of silicon and oxygen in the nontronite tetrahedral sheet. Because the tetrahedral and octahedral sheets of nontronite deform differently, impact-driven structural deformation may contribute to differences in phyllosilicate detection between remote sensing techniques sensitive to different parts of the nontronite structure. Observed spectroscopic changes also indicated that the sample's octahedral and tetrahedral sheets were structurally deformed but not completely dehydroxylated. This finding is an important distinction from previous studies of thermally altered phyllosilicates in which dehydroxylation follows dehydration in a stepwise progression preceding structural deformation. Impact alteration may thus complicate mineral-specific identifications based on the location of OH-group bands in remotely detected spectra. This is a key implication for Martian remote sensing arising from our results.

Top-down regulation, climate and multi-decadal changes in coastal zoobenthos communities in two Baltic Sea areas.

PubMed

Olsson, Jens; Bergström, Lena; Gårdmark, Anna

2013-01-01

The structure of many marine ecosystems has changed substantially during recent decades, as a result of overexploitation, climate change and eutrophication. Despite of the apparent ecological and economical importance of coastal areas and communities, this aspect has received relatively little attention in coastal systems. Here we assess the temporal development of zoobenthos communities in two areas on the Swedish Baltic Sea coast during 30 years, and relate their development to changes in climate, eutrophication and top-down regulation from fish. Both communities show substantial structural changes, with a decrease in marine polychaetes and species sensitive to increased water temperatures. Concurrently, opportunistic species tolerant to environmental perturbation have increased in abundance. Species composition show a similar temporal development in both communities and significant changes in species composition occurred in both data sets in the late 1980s and early 1990s. The change in species composition was associated with large scale changes in climate (salinity and water temperature) and to the structure of the local fish community, whereas we found no effects of nutrient loading or ambient nutrient concentrations. Our results suggest that these coastal zoobenthos communities have gone through substantial structural changes over the last 30 years, resulting in communities of different species composition with potentially different ecological functions. We hence suggest that the temporal development of coastal zoobenthos communities should be assessed in light of prevailing climatic conditions considering the potential for top-down effects exerted by local fish communities.

Top-Down Regulation, Climate and Multi-Decadal Changes in Coastal Zoobenthos Communities in Two Baltic Sea Areas

PubMed Central

Olsson, Jens; Bergström, Lena; Gårdmark, Anna

2013-01-01

The structure of many marine ecosystems has changed substantially during recent decades, as a result of overexploitation, climate change and eutrophication. Despite of the apparent ecological and economical importance of coastal areas and communities, this aspect has received relatively little attention in coastal systems. Here we assess the temporal development of zoobenthos communities in two areas on the Swedish Baltic Sea coast during 30 years, and relate their development to changes in climate, eutrophication and top-down regulation from fish. Both communities show substantial structural changes, with a decrease in marine polychaetes and species sensitive to increased water temperatures. Concurrently, opportunistic species tolerant to environmental perturbation have increased in abundance. Species composition show a similar temporal development in both communities and significant changes in species composition occurred in both data sets in the late 1980s and early 1990s. The change in species composition was associated with large scale changes in climate (salinity and water temperature) and to the structure of the local fish community, whereas we found no effects of nutrient loading or ambient nutrient concentrations. Our results suggest that these coastal zoobenthos communities have gone through substantial structural changes over the last 30 years, resulting in communities of different species composition with potentially different ecological functions. We hence suggest that the temporal development of coastal zoobenthos communities should be assessed in light of prevailing climatic conditions considering the potential for top-down effects exerted by local fish communities. PMID:23737998

Structural changes of the regulatory proteins bound to the thin filaments in skeletal muscle contraction by X-ray fiber diffraction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sugimoto, Yasunobu; Takezawa, Yasunori; Matsuo, Tatsuhito

2008-04-25

In order to clarify the structural changes related to the regulation mechanism in skeletal muscle contraction, the intensity changes of thin filament-based reflections were investigated by X-ray fiber diffraction. The time course and extent of intensity changes of the first to third order troponin (TN)-associated meridional reflections with a basic repeat of 38.4 nm were different for each of these reflections. The intensity of the first and second thin filament layer lines changed in a reciprocal manner both during initial activation and during the force generation process. The axial spacings of the TN-meridional reflections decreased by {approx}0.1% upon activation relativemore » to the relaxing state and increased by {approx}0.24% in the force generation state, in line with that of the 2.7-nm reflection. Ca{sup 2+}-binding to TN triggered the shortening and a change in the helical symmetry of the thin filaments. Modeling of the structural changes using the intensities of the thin filament-based reflections suggested that the conformation of the globular core domain of TN altered upon activation, undergoing additional conformational changes at the tension plateau. The tail domain of TN moved together with tropomyosin during contraction. The results indicate that the structural changes of regulatory proteins bound to the actin filaments occur in two steps, the first in response to the Ca{sup 2+}-binding and the second induced by actomyosin interaction.« less

Biochemical Storage Lesions Occurring in Nonirradiated and Irradiated Red Blood Cells: A Brief Review

PubMed Central

Adams, F.; Bellairs, G.; Bird, A. R.; Oguntibeju, O. O.

2015-01-01

Red blood cells undergo a series of biochemical fluctuations during 35–42-day storage period at 1°C to 6°C. The sodium/potassium pump is immobilised causing a decrease in intracellular potassium with an increase in cytoplasmic sodium levels, glucose levels decline, and acidosis occurs as a result of low pH levels. The frailty of stored erythrocytes triggers the formation of haemoglobin-containing microparticles and the release of cell-free haemoglobin which may add to transfusion difficulties. Lipid peroxidation, oxidative stress to band 3 structures, and other morphological and structural molecular changes also occur leading to spheroechinocytes and osmotic fragility. These changes that transpire in the red cells during the storage period are referred to as “storage lesions.” It is well documented that gamma irradiation exacerbates storage lesions and the reports of increased potassium levels leading to adverse reactions observed in neonates and infants have been of particular concern. There are, however, remarkably few systematic studies comparing the in vitro storage lesions of irradiated and nonirradiated red cell concentrates and it has been suggested that the impact of storage lesions on leucocyte reduced red blood cell concentrate (RBCC) is incomplete. The review examines storage lesions in red blood cells and their adverse effects in reference to blood transfusion. PMID:25710038

Bark beetle responses to vegetation management practices

Treesearch

Joel D. McMillin; Christopher J. Fettig

2009-01-01

Native tree-killing bark beetles (Coleoptera: Curculionidae, Scolytinae) are a natural component of forest ecosystems. Eradication is neither possible nor desirable and periodic outbreaks will occur as long as susceptible forests and favorable climatic conditions co-exist. Recent changes in forest structure and tree composition by natural processes and management...

Dysfunctional Families of the Student with Special Needs.

ERIC Educational Resources Information Center

Daniels-Mohring, Debbie; Lambie, Rosemary

1993-01-01

This paper outlines the changes that occur in family systems when a child is diagnosed with special needs and examines the structure of dysfunctional families in which there is a child with physical disabilities, including chronic illness; behavior disorders, including social maladjustment; learning disabilities; or mental retardation. (JDD)

Lichen indicator [Section 4

Treesearch

Paul L. Patterson; Susan Will-Wolf; Marie T. Trest

2009-01-01

Lichens are very responsive to environmental stressors in forests, including changes in forest structure, air quality, and climate. Each lichen species on a plot is an indicator of how lichen communities respond to ecological conditions. Individual lichen species occur erratically and even common species are often absent from plots with suitable habitat. The combined...

Geographic patterns of genetic variation and population structure in Pinus aristata, Rocky Mountain bristlecone pine

USDA-ARS?s Scientific Manuscript database

Pinus aristata Engelm., Rocky Mountain bristlecone pine, has a narrow core geographic and elevational distribution, occurs in disjunct populations and is threatened by multiple stresses, including rapid climate change, white pine blister rust, and bark beetles. Knowledge of genetic diversity and pop...

Chemistry--The Big Picture

ERIC Educational Resources Information Center

Cassell, Anne

2011-01-01

Chemistry produces materials and releases energy by ionic or electronic rearrangements. Three structure types affect the ease with which a reaction occurs. In the Earth's crust, "solid crystals" change chemically only with extreme heat and pressure, unless their fixed ions touch moving fluids. On the other hand, in living things, "liquid crystals"…

FOOD WEB STRUCTURE AS A POTENTIAL INDICATOR OF NUTRIENT ENRICHMENT IN GREAT LAKES COASTAL WETLANDS

EPA Science Inventory

Analyses of the food webs of Great Lakes coastal wetlands verify the role of algae as an energetic foundation, and also suggest that fundamental changes occur in response to both natural and anthropogenic influences. We analyzed coastal wetlands with a range of nutrient concentra...

The Emergence of Mathematical Structures

ERIC Educational Resources Information Center

Hegedus, Stephen John; Moreno-Armella, Luis

2011-01-01

We present epistemological ruptures that have occurred in mathematical history and in the transformation of using technology in mathematics education in the twenty-first century. We describe how such changes establish a new form of digital semiotics that challenges learning paradigms and mathematical inquiry for learners today. We focus on drawing…

Ordered distribution of I and Cl in the low-temperature crystal structure of mutnovskite, Pb{sub 4}As{sub 2}S{sub 6}ICl: An X-ray single-crystal study

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bindi, Luca; Garavelli, Anna; Pinto, Daniela

2008-02-15

To study the temperature-dependent structural changes and to analyze the crystal chemical behavior of the halogens as a function of temperature, a crystal of the recently discovered mineral mutnovskite, ideally Pb{sub 2}AsS{sub 3}(I,Cl,Br), has been investigated by X-ray single-crystal diffraction methods at 300 and 110 K. At room temperature (RT) mutnovskite was confirmed to possess a centrosymmetric structure-type, space group Pnma, while at low temperature (110 K) it adopts a non-centrosymmetric orthorhombic structure-type, space group Pnm2{sub 1}, with a=11.5394(9) A, b=6.6732(5) A, c=9.3454(7) A, V=719.64(9) A{sup 3} and Z=2. Mutnovskite reconverts to the centrosymmetric-type upon returning to RT thus indicatingmore » that the phase transition is completely reversible in character. The refinement of the LT-structure leads to a residual factor R=0.0336 for 1827 independent observed reflections [F{sub o}>4{sigma}(F{sub o})] and 80 variables. The crystal structure of cooled mutnovskite is topologically identical to that observed at RT and the slight structural changes occurring during the phase transition Pnma{yields}Pnm2{sub 1} are mainly restricted to the coordination polyhedra around Pb. The structure solution revealed that I and Cl are ordered into two specific sites. Indeed, the unique mixed (I,Cl) position in the RT-structure (Wyckoff position 4c) transforms into two 2a Wyckoff positions in the LT-structure hosting I and Cl, respectively. - Graphical abstract: In the crystal structure of mutnovskite at 110 K the two halogens I and Cl are ordered into two specific sites and only slight changes in the coordination environment around Pb atoms occur during the phase transition Pnma{yields}Pnm2{sub 1} from the RT-structure to the LT-structure. Two kinds of layers alternating along a are present in the LT-structure: Layer I contains Cl atoms and [001] columns of Pb1 and Pb4 prisms, layer II contains I atoms and [001] columns of Pb2 and Pb3 prisms.« less

Dynamic functional connectivity using state-based dynamic community structure: method and application to opioid analgesia.

PubMed

Robinson, Lucy F; Atlas, Lauren Y; Wager, Tor D

2015-03-01

We present a new method, State-based Dynamic Community Structure, that detects time-dependent community structure in networks of brain regions. Most analyses of functional connectivity assume that network behavior is static in time, or differs between task conditions with known timing. Our goal is to determine whether brain network topology remains stationary over time, or if changes in network organization occur at unknown time points. Changes in network organization may be related to shifts in neurological state, such as those associated with learning, drug uptake or experimental conditions. Using a hidden Markov stochastic blockmodel, we define a time-dependent community structure. We apply this approach to data from a functional magnetic resonance imaging experiment examining how contextual factors influence drug-induced analgesia. Results reveal that networks involved in pain, working memory, and emotion show distinct profiles of time-varying connectivity. Copyright © 2014 Elsevier Inc. All rights reserved.

Mechanical Anisotropy and Pressure Induced Structural Changes in Piroxicam Crystals Probed by In Situ Indentation and Raman Spectroscopy

NASA Astrophysics Data System (ADS)

Manimunda, Praveena; Hintsala, Eric; Asif, Syed; Mishra, Manish Kumar

2017-01-01

The ability to correlate mechanical and chemical characterization techniques in real time is both lacking and powerful tool for gaining insights into material behavior. This is demonstrated through use of a novel nanoindentation device equipped with Raman spectroscopy to explore the deformation-induced structural changes in piroxicam crystals. Mechanical anisotropy was observed in two major faces ( 0bar{1}1 ) and (011), which are correlated to changes in the interlayer interaction from in situ Raman spectra recorded during indentation. The results of this study demonstrate the considerable potential of an in situ Raman nanoindentation instrument for studying a variety of topics, including stress-induced phase transformation mechanisms, mechanochemistry, and solid state reactivity under mechanical forces that occur in molecular and pharmaceutical solids.

Changes in geometrical and biomechanical properties of immature male and female rat tibia

NASA Technical Reports Server (NTRS)

Zernicke, Ronald F.; Hou, Jack C.-H.; Vailas, Arthur C.; Nishimoto, Mitchell; Patel, Sanjay

1990-01-01

The differences in the geometry and mechanical properties of immature male and female rat tibiae were detailed in order to provide comparative data for spaceflight, exercise, or disease experiments that use immature rats as an animal model. The experiment focuses on the particularly rapid period of growth that occurs in the Sprague-Dawley rat between 40 and 60 d of age. Tibial length and middiaphysical cross-sectional data were analyzed for eight different groups of rats according to age and sex, and tibial mechanical properties were obtained via three-point bending tests to failure. Results indicate that, during the 15 d period of rapid growth, changes in rat tibial geometry are more important than changes in bone material properties for influencing the mechanical properties of the tibia. Male tibiae changed primarily in structural properties, while in the female rats major changes in mechanical properties of the tibia were only attributable to changes in the structural properties of the bone.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Barroo, Cedric; Janvelyan, Nare; Zugic, Branko

To improve the understanding of catalytic processes, the surface structure and composition of the active materials need to be determined before and after reaction. Morphological changes may occur under reaction conditions and can dramatically influence the reactivity and/or selectivity of a catalyst. Goldbased catalysts with different architectures are currently being developed for selective oxidation reactions at low temperatures. Specifically, nanoporous Au (npAu) with a composition of Au 97-Ag 3 is obtained by dealloying a Ag 70-Au 30 bulk alloy. Recent studies highlight the efficiency of npAu catalysts for methanol oxidation using ozone to activate the catalysts before methanol oxidation. Inmore » this paper, we studied the morphological and compositional changes occurring at the surface of Au-based catalysts in certain conditions.« less

Aging Neural Progenitor Cells Have Decreased Mitochondrial Content and Lower Oxidative Metabolism*

PubMed Central

Stoll, Elizabeth A.; Cheung, Willy; Mikheev, Andrei M.; Sweet, Ian R.; Bielas, Jason H.; Zhang, Jing; Rostomily, Robert C.; Horner, Philip J.

2011-01-01

Although neurogenesis occurs in discrete areas of the adult mammalian brain, neural progenitor cells (NPCs) produce fewer new neurons with age. To characterize the molecular changes that occur during aging, we performed a proteomic comparison between primary-cultured NPCs from the young adult and aged mouse forebrain. This analysis yielded changes in proteins necessary for cellular metabolism. Mitochondrial quantity and oxygen consumption rates decrease with aging, although mitochondrial DNA in aged NPCs does not have increased mutation rates. In addition, aged cells are resistant to the mitochondrial inhibitor rotenone and proliferate in response to lowered oxygen conditions. These results demonstrate that aging NPCs display an altered metabolic phenotype, characterized by a coordinated shift in protein expression, subcellular structure, and metabolic physiology. PMID:21900249

Genetic influences on individual differences in longitudinal changes in global and subcortical brain volumes: Results of the ENIGMA plasticity working group.

PubMed

Brouwer, Rachel M; Panizzon, Matthew S; Glahn, David C; Hibar, Derrek P; Hua, Xue; Jahanshad, Neda; Abramovic, Lucija; de Zubicaray, Greig I; Franz, Carol E; Hansell, Narelle K; Hickie, Ian B; Koenis, Marinka M G; Martin, Nicholas G; Mather, Karen A; McMahon, Katie L; Schnack, Hugo G; Strike, Lachlan T; Swagerman, Suzanne C; Thalamuthu, Anbupalam; Wen, Wei; Gilmore, John H; Gogtay, Nitin; Kahn, René S; Sachdev, Perminder S; Wright, Margaret J; Boomsma, Dorret I; Kremen, William S; Thompson, Paul M; Hulshoff Pol, Hilleke E

2017-09-01

Structural brain changes that occur during development and ageing are related to mental health and general cognitive functioning. Individuals differ in the extent to which their brain volumes change over time, but whether these differences can be attributed to differences in their genotypes has not been widely studied. Here we estimate heritability (h 2 ) of changes in global and subcortical brain volumes in five longitudinal twin cohorts from across the world and in different stages of the lifespan (N = 861). Heritability estimates of brain changes were significant and ranged from 16% (caudate) to 42% (cerebellar gray matter) for all global and most subcortical volumes (with the exception of thalamus and pallidum). Heritability estimates of change rates were generally higher in adults than in children suggesting an increasing influence of genetic factors explaining individual differences in brain structural changes with age. In children, environmental influences in part explained individual differences in developmental changes in brain structure. Multivariate genetic modeling showed that genetic influences of change rates and baseline volume significantly overlapped for many structures. The genetic influences explaining individual differences in the change rate for cerebellum, cerebellar gray matter and lateral ventricles were independent of the genetic influences explaining differences in their baseline volumes. These results imply the existence of genetic variants that are specific for brain plasticity, rather than brain volume itself. Identifying these genes may increase our understanding of brain development and ageing and possibly have implications for diseases that are characterized by deviant developmental trajectories of brain structure. Hum Brain Mapp 38:4444-4458, 2017. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

Visualization of the structural changes in plywood and gypsum board during the growth of Chaetomium globosum and Stachybotrys chartarum.

PubMed

Lewinska, Anna M; Hoof, Jakob B; Peuhkuri, Ruut H; Rode, Carsten; Lilje, Osu; Foley, Matthew; Trimby, Patrick; Andersen, Birgitte

2016-10-01

Fungal growth in indoor environments is associated with many negative health effects. Many studies focus on brown- and white-rot fungi and their effect on wood, but there is none that reveals the influence of soft-rot fungi, such as Stachybotrys spp. and Chaetomium spp., on the structure of building materials such as plywood and gypsum wallboard. This study focuses on using micro-computed tomography (microCT) to investigate changes of the structure of plywood and gypsum wallboard during fungal degradation by S. chartarum and C. globosum. Changes in the materials as a result of dampness and fungal growth were determined by measuring porosity and pore shape via microCT. The results show that the composition of the building material influenced the level of penetration by fungi as shown by scanning electron microscopy (SEM). Plywood appeared to be the most affected, with the penetration of moisture and fungi throughout the whole thickness of the sample. Conversely, fungi grew only on the top cardboard in the gypsum wallboard and they did not have significant influence on the gypsum wallboard structure. The majority of the observed changes in gypsum wallboard occurred due to moisture. This paper suggests that the mycelium distribution within building materials and the structural changes, caused by dampness and fungal growth, depend on the type of the material. Copyright © 2016 Elsevier B.V. All rights reserved.

Formation of insulin amyloid fibrils followed by FTIR simultaneously with CD and electron microscopy.

PubMed Central

Bouchard, M.; Zurdo, J.; Nettleton, E. J.; Dobson, C. M.; Robinson, C. V.

2000-01-01

Fourier transform infrared spectroscopy (FTIR), circular dichroism (CD), and electron microscopy (EM) have been used simultaneously to follow the temperature-induced formation of amyloid fibrils by bovine insulin at acidic pH. The FTIR and CD data confirm that, before heating, insulin molecules in solution at pH 2.3 have a predominantly native-like alpha-helical structure. On heating to 70 degrees C, partial unfolding occurs and results initially in aggregates that are shown by CD and FT-IR spectra to retain a predominantly helical structure. Following this step, changes in the CD and FTIR spectra occur that are indicative of the extensive conversion of the molecular conformation from alpha-helical to beta-sheet structure. At later stages, EM shows the development of fibrils with well-defined repetitive morphologies including structures with a periodic helical twist of approximately 450 A. The results indicate that formation of fibrils by insulin requires substantial unfolding of the native protein, and that the most highly ordered structures result from a slow evolution of the morphology of the initially formed fibrillar species. PMID:11106169

A structural study of bone changes in knee osteoarthritis by synchrotron-based X-ray fluorescence and X-ray absorption spectroscopy techniques

NASA Astrophysics Data System (ADS)

Sindhupakorn, Bura; Thienpratharn, Suwittaya; Kidkhunthod, Pinit

2017-10-01

Osteoarthritis (OA) is characterized by degeneration of articular cartilage and thickening of subchondral bone. The present study investigated the changing of biochemical components of cartilage and bone compared between normal and OA people. Using Synchrotron-based X-ray fluorescence (SR-XRF) and X-ray absorption spectroscopy (XAS) techniquesincluding X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) were employed for the bone changes in kneeosteoarthritisstudies. The bone samples were collected from various osteoarthritis patients with both male and female in the ages range between 20 and 74 years old. SR-XRF results excited at 4240 eV for Ca elements show a majority three main groups, based on their XRF intensities, 20-36 years, 40-60 years and over 70 years, respectively. By employing XAS techniques, XANES features can be used to clearly explain in term of electronic transitions occurring in bone samples which are affected from osteoarthritis symptoms. Moreover, a structural change around Ca ions in bone samples is obviously obtained by EXAFS results indicating an increase of Ca-amorphous phase when the ages increase.

Developmental changes in organization of structural brain networks.

PubMed

Khundrakpam, Budhachandra S; Reid, Andrew; Brauer, Jens; Carbonell, Felix; Lewis, John; Ameis, Stephanie; Karama, Sherif; Lee, Junki; Chen, Zhang; Das, Samir; Evans, Alan C

2013-09-01

Recent findings from developmental neuroimaging studies suggest that the enhancement of cognitive processes during development may be the result of a fine-tuning of the structural and functional organization of brain with maturation. However, the details regarding the developmental trajectory of large-scale structural brain networks are not yet understood. Here, we used graph theory to examine developmental changes in the organization of structural brain networks in 203 normally growing children and adolescents. Structural brain networks were constructed using interregional correlations in cortical thickness for 4 age groups (early childhood: 4.8-8.4 year; late childhood: 8.5-11.3 year; early adolescence: 11.4-14.7 year; late adolescence: 14.8-18.3 year). Late childhood showed prominent changes in topological properties, specifically a significant reduction in local efficiency, modularity, and increased global efficiency, suggesting a shift of topological organization toward a more random configuration. An increase in number and span of distribution of connector hubs was found in this age group. Finally, inter-regional connectivity analysis and graph-theoretic measures indicated early maturation of primary sensorimotor regions and protracted development of higher order association and paralimbic regions. Our finding reveals a time window of plasticity occurring during late childhood which may accommodate crucial changes during puberty and the new developmental tasks that an adolescent faces.

System for tamper identification

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bobbitt, III, John Thomas; Weeks, George E.

2017-09-05

A system for tamper identification. A fastener has a tamper identification surface with a unique grain structure that is altered if the fastener is removed or otherwise exposed to sufficient torque. After a period of time such as e.g., shipment and/or storage of the sealed container, a determination of whether tampering has occurred can be undertaken by examining the grain structure to determine if it has changed since the fastener was used to seal the container or secure the device.

How the Structure of Mesoscale Precipitation Systems Affects their Production of Transient Luminous Events

NASA Astrophysics Data System (ADS)

Lang, T. J.; Lyons, W.; Rutledge, S. A.; Cummer, S. A.; MacGorman, D. R.

2011-12-01

Recently, Lang et al. (2010) analyzed the parent lightning of transient luminous events (TLEs) in the context of the structure and evolution of two mesoscale convective systems (MCSs). These two MCSs were very different - one a giant symmetric leading-line/trailing stratiform storm, and one a small asymmetric MCS that contained a mesoscale convective vortex. These structural differences were associated with substantially different TLE-parent lightning structure as well as TLE production. The results suggested that TLE (especially sprite) production, and TLE-parent positive charge altitude, depend on MCS morphology. Current work is focused on analyzing the structure, evolution, lightning behavior, and TLE production of additional MCSs over various regions of the United States. Several additional TLE-producing MCS cases already have been identified for the years 2008-2010, featuring a variety of organizational modes (symmetric, asymmetric, and other more exotic varieties) in different meteorological regimes (including some cold-season cases). More cases will be incorporated as they occur and are observed. Data sources include geostationary satellite imagery, Doppler radar, three-dimensional lightning mapping networks, ground-strike detection networks, charge moment change measurements, and low-light video observations. The ultimate goal is to further test the hypothesis that MCS structure affects TLE production, and if so to quantify its impact. Research on two Oklahoma case studies, a multicellular system that occurred on 24 March 2009 and a classic bow-echo MCS that occurred on 19 August 2009, is ongoing. Over a 2.5-h period, the March case produced 23 observed TLEs (all sprites) whose parent flashes occurred within 175 km of the Oklahoma Lightning Mapping Array (OKLMA). The median altitude of LMA sources during the TLEs was 5.9 km above Mean Sea Level (MSL), or -19.2 °C. The August storm produced, in 2.5 hours, 34 TLEs (all sprites) with 32 of those having parent flashes within 175 km of the OKLMA. The median altitude for those flashes was higher, 7.1 km MSL, though at a warmer temperature of -14.7 °C due to the time of season. Based on analysis of the radar structures and the lightning data, the two storms support the hypothesized effects of organizational mode on sprite production. In particular, sprite production by the August MCS appeared to benefit from its leading-line/trailing-stratiform structure, which likely led to a higher altitude for the dominant stratiform positive charge layer. This would increase charge moment change, a key metric for the production of sprites.

Structural and functional changes associated with normal and abnormal fundus autofluorescence in patients with retinitis pigmentosa.

PubMed

Greenstein, Vivienne C; Duncker, Tobias; Holopigian, Karen; Carr, Ronald E; Greenberg, Jonathan P; Tsang, Stephen H; Hood, Donald C

2012-02-01

To analyze the structure and visual function of regions bordering the hyperautofluorescent ring/arcs in retinitis pigmentosa. Twenty-one retinitis pigmentosa patients (21 eyes) with rings/arcs and 21 normal individuals (21 eyes) were studied. Visual sensitivity in the central 10° was measured with microperimetry. Retinal structure was evaluated with spectral-domain optical coherence tomography. The distance from the fovea to disruption/loss of the inner outer segment (IS/OS) junction and thicknesses of the total receptor plus retinal pigment epithelial complex and outer segment plus retinal pigment epithelial complex layers were measured. Results were compared with measurements of the distance from the fovea to the inner and outer borders of the ring/arc seen on fundus autofluorescence. Disruption/loss of the inner outer segment junction occurred closer to the inner border of the ring/arc and it was closer to the fovea in eight eyes. For 19 eyes, outer segment plus and receptor plus RPE complex thicknesses were significantly decreased at locations closer to the fovea than the appearance of the inner border of hyperautofluorescence. Mean visual sensitivity was decreased inside, across, and outside the ring/arc by 3.5 ± 3.8, 8.9 ± 4.8, and 17.0 ± 2.4 dB, respectively. Structural and functional changes can occur inside the hyperfluorescent ring/arc in retinitis pigmentosa.

Structural and Functional Changes Associated with Normal and Abnormal Fundus Autofluorescence in Patients with Retinitis Pigmentosa

PubMed Central

Greenstein, Vivienne C.; Duncker, Tobias; Holopigian, Karen; Carr, Ronald E.; Greenberg, Jonathan; Tsang, Stephen H.; Hood, Donald C.

2013-01-01

Purpose To analyze the structure and visual function of regions bordering the hyperautofluorescent ring/arcs in retinitis pigmentosa (RP). Methods Twenty -one RP patients (21 eyes) with rings/arcs and 21 normals (21 eyes) were studied. Visual sensitivity in the central 10° was measured with microperimetry. Retinal structure was evaluated with spectral domain optical coherence tomography (SD-OCT). The distance from the fovea to disruption/loss of the inner outer segment (IS/OS) junction and thicknesses of the total receptor plus retinal pigment epithelial (RPE) complex (R+), and outer segment plus RPE complex (OS+) layers were measured. Results were compared to measurements of the distance from the fovea to the inner and outer borders of the ring/arc seen on fundus autofluorescence (FAF). Results Disruption/loss of the IS/OS junction occurred closer to the inner border of the ring/arc and it was closer to the fovea in 8 eyes. For 19 eyes, OS+ and R+ thicknesses were significantly decreased at locations closer to the fovea than the appearance of the inner border of hyperautofluorescence. Mean visual sensitivity was decreased inside, across and outside the ring/arc by 3.5 ± 3.8, 8.9 ± 4.8 and 17.0±2.4 dB respectively. Conclusions Structural and functional changes can occur inside the hyperfluorescent ring/arc in RP. PMID:21909055

Structural Studies of Complex Carbohydrates of Plant Cell Walls

DOE Office of Scientific and Technical Information (OSTI.GOV)

Darvill, Alan; Hahn, Michael G.; O'Neill, Malcolm A.

Most of the solar energy captured by land plants is converted into the polysaccharides (cellulose, hemicellulose, and pectin) that are the predominant components of the cell wall. These walls, which account for the bulk of plant biomass, have numerous roles in the growth and development of plants. Moreover, these walls have a major impact on human life as they are a renewable source of biomass, a source of diverse commercially useful polymers, a major component of wood, and a source of nutrition for humans and livestock. Thus, understanding the molecular mechanisms that lead to wall assembly and how cell wallsmore » and their component polysaccharides contribute to plant growth and development is essential to improve and extend the productivity and value of plant materials. The proposed research will develop and apply advanced analytical and immunological techniques to study specific changes in the structures and interactions of the hemicellulosic and pectic polysaccharides that occur during differentiation and in response to genetic modification and chemical treatments that affect wall biosynthesis. These new techniques will make it possible to accurately characterize minute amounts of cell wall polysaccharides so that subtle changes in structure that occur in individual cell types can be identified and correlated to the physiological or developmental state of the plant. Successful implementation of this research will reveal fundamental relationships between polysaccharide structure, cell wall architecture, and cell wall functions.« less

Protein structural changes during processing of vegetable feed ingredients used in swine diets: implications for nutritional value.

PubMed

Salazar-Villanea, S; Hendriks, W H; Bruininx, E M A M; Gruppen, H; van der Poel, A F B

2016-06-01

Protein structure influences the accessibility of enzymes for digestion. The proportion of intramolecular β-sheets in the secondary structure of native proteins has been related to a decrease in protein digestibility. Changes to proteins that can be considered positive (for example, denaturation and random coil formation) or negative (for example, aggregation and Maillard reactions) for protein digestibility can occur simultaneously during processing. The final result of these changes on digestibility seems to be a counterbalance of the occurrence of each phenomenon. Occurrence of each phenomenon depends on the conditions applied, but also on the source and type of the protein that is processed. The correlation between denaturation enthalpy after processing and protein digestibility seems to be dependent on the protein source. Heat seems to be the processing parameter with the largest influence on changes in the structure of proteins. The effect of moisture is usually limited to the simultaneous application of heat, but increasing level of moisture during processing usually increases structural changes in proteins. The effect of shear on protein structure is commonly studied using extrusion, although the multifactorial essence of this technology does not allow disentanglement of the separate effects of each processing parameter (for example, heat, shear, moisture). Although most of the available literature on the processing of feed ingredients reports effects on protein digestibility, the mechanisms that explain these effects are usually lacking. Clarifying these mechanisms could aid in the prediction of the nutritional consequences of processing conditions.

Conformational switching upon phosphorylation: a predictive framework based on energy landscape principles.

PubMed

Lätzer, Joachim; Shen, Tongye; Wolynes, Peter G

2008-02-19

We investigate how post-translational phosphorylation modifies the global conformation of a protein by changing its free energy landscape using two test proteins, cystatin and NtrC. We first examine the changes in a free energy landscape caused by phosphorylation using a model containing information about both structural forms. For cystatin the free energy cost is fairly large indicating a low probability of sampling the phosphorylated conformation in a perfectly funneled landscape. The predicted barrier for NtrC conformational transition is several times larger than the barrier for cystatin, indicating that the switch protein NtrC most probably follows a partial unfolding mechanism to move from one basin to the other. Principal component analysis and linear response theory show how the naturally occurring conformational changes in unmodified proteins are captured and stabilized by the change of interaction potential. We also develop a partially guided structure prediction Hamiltonian which is capable of predicting the global structure of a phosphorylated protein using only knowledge of the structure of the unphosphorylated protein or vice versa. This algorithm makes use of a generic transferable long-range residue contact potential along with details of structure short range in sequence. By comparing the results obtained with this guided transferable potential to those from the native-only, perfectly funneled Hamiltonians, we show that the transferable Hamiltonian correctly captures the nature of the global conformational changes induced by phosphorylation and can sample substantially correct structures for the modified protein with high probability.

Tracking the Remodeling of SNOMED CT's Bacterial Infectious Diseases.

PubMed

Ochs, Christopher; Case, James T; Perl, Yehoshua

2016-01-01

SNOMED CT's content undergoes many changes from one release to the next. Over the last year SNOMED CT's Bacterial infectious disease subhierarchy has undergone significant editing to bring consistent modeling to its concepts. In this paper we analyze the stated and inferred structural modifications that affected the Bacterial infectious disease subhierarchy between the Jan 2015 and Jan 2016 SNOMED CT releases using a two-phased approach. First, we introduce a methodology for creating a human readable list of changes. Next, we utilize partial-area taxonomies, which are compact summaries of SNOMED CT's content and structure, to identify the "big picture" changes that occurred in the subhierarchy. We illustrate how partial-area taxonomies can be used to help identify groups of concepts that were affected by these editing operations and the nature of these changes. Modeling issues identified using our two-phase methodology are discussed.

How Conformational Dynamics of DNA Polymerase Select Correct Substrates: Experiments and Simulations

PubMed Central

Kirmizialtin, Serdal; Nguyen, Virginia; Johnson, Kenneth A.; Elber, Ron

2012-01-01

Summary Nearly every enzyme undergoes a significant change in structure after binding it’s substrate. New experimental and theoretical analyses of the role of changes in HIV reverse transcriptase structure in selecting a correct substrate are presented. Atomically detailed simulations using the Milestoning method predict a rate and free energy profile of the conformational change commensurate with experimental data. A large conformational change occurring on a ms timescale locks the correct nucleotide at the active site, but promotes release of a mismatched nucleotide. The positions along the reaction coordinate that decide the yield of the reaction are not determined by the chemical step. Rather, the initial steps of weak substrate binding and protein conformational transition significantly enrich the yield of a reaction with a correct substrate, while the same steps diminish the reaction probability of an incorrect substrate. PMID:22483109

Quantitative percussion diagnostics as an indicator of the level of the structural pathology of teeth: Retrospective follow-up investigation of high-risk sites that remained pathological after restorative treatment.

PubMed

Sheets, Cherilyn G; Wu, Jean C; Earthman, James C

2017-11-29

Structural damage may remain even after a tooth is restored. Conventional diagnostic aids do not quantify the severity of structural damage or allow the monitoring of structural changes after restoration. The purpose of this retrospective clinical study was to provide an in-depth analysis of 9 high-risk sites after restoration. The analysis followed structural defects found upon disassembly, restorative materials used, therapeutic procedures provided, current longevity, and long-term quantitative percussion diagnostics (QPD) to monitor results. The hypothesis was that QPD can be used to quantify positive and negative changes in structural stability. Sixty sites requiring restoration were part of an institutional review board-approved clinical study. Each participant was examined comprehensively, including QPD testing, at each follow-up. Long-term changes in normal fit error (NFE) values after restoration were evaluated according to a pathology rating system established in an earlier publication. Nine highly compromised sites were chosen for further analysis and monitored for an additional 6 years. Of the 9 high-risk sites (NFE>0.04), 7 sites improved and 2 sites deteriorated. Potential causes for each trend were documented. The data support the hypothesis that QPD can be used to monitor changes in structural stability after restoration. Knowledge of changes in advance of any symptoms allows further preventive or therapeutic intervention before serious structural damage can occur. Follow-up QPD indications of site improvement can also assure the clinician of the desired structural outcome. Copyright © 2017 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.

New perspectives on evolutionary medicine: the relevance of microevolution for human health and disease

PubMed Central

2013-01-01

Evolutionary medicine (EM) is a growing field focusing on the evolutionary basis of human diseases and their changes through time. To date, the majority of EM studies have used pure theories of hominin macroevolution to explain the present-day state of human health. Here, we propose a different approach by addressing more empirical and health-oriented research concerning past, current and future microevolutionary changes of human structure, functions and pathologies. Studying generation-to-generation changes of human morphology that occurred in historical times, and still occur in present-day populations under the forces of evolution, helps to explain medical conditions and warns clinicians that their current practices may influence future humans. Also, analyzing historic tissue specimens such as mummies is crucial in order to address the molecular evolution of pathogens, of the human genome, and their coadaptations. PMID:23627943

Examining land-use/land-cover change in the Lake Dianchi watershed of the Yunnan-Guizhou Plateau of Southwest China with remote sensing and GIS techniques: 1974–2008.

PubMed

Zhao, Yaolong; Zhang, Ke; Fu, Yingchun; Zhang, Hong

2012-10-24

Monitoring land-use/land-cover change (LULCC) and exploring its mechanisms are important processes in the environmental management of a lake watershed. The purpose of this study was to examine the spatiotemporal pattern of LULCC by using multi landscape metrics in the Lake Dianchi watershed, which is located in the Yunnan-Guizhou Plateau of Southwest China. Landsat images from the years 1974, 1988, 1998, and 2008 were analyzed using geographical information system (GIS) techniques. The results reveal that land-use/land-cover has changed greatly in the watershed since 1974. This change in land use structure was embodied in the rapid increase of developed areas with a relative change rate of up to 324.4%. The increase in developed areas mainly occurred in agricultural land, especially near the shores of Lake Dianchi. The spatial pattern and structure of the change was influenced by the urban sprawl of the city of Kunming. The urban sprawl took on the typical expansion mode of cyclic structures and a jigsaw pattern and expanded to the shore of Lake Dianchi. Agricultural land changed little with respect to the structure but changed greatly in the spatial pattern. The landscape in the watershed showed a trend of fragmentation with a complex boundary. The dynamics of land-use/land-cover in the watershed correlate with land-use policies and economic development in China.

Examining Land-Use/Land-Cover Change in the Lake Dianchi Watershed of the Yunnan-Guizhou Plateau of Southwest China with Remote Sensing and GIS Techniques: 1974-2008

PubMed Central

Zhao, Yaolong; Zhang, Ke; Fu, Yingchun; Zhang, Hong

2012-01-01

Monitoring land-use/land-cover change (LULCC) and exploring its mechanisms are important processes in the environmental management of a lake watershed. The purpose of this study was to examine the spatiotemporal pattern of LULCC by using multi landscape metrics in the Lake Dianchi watershed, which is located in the Yunnan-Guizhou Plateau of Southwest China. Landsat images from the years 1974, 1988, 1998, and 2008 were analyzed using geographical information system (GIS) techniques. The results reveal that land-use/land-cover has changed greatly in the watershed since 1974. This change in land use structure was embodied in the rapid increase of developed areas with a relative change rate of up to 324.4%. The increase in developed areas mainly occurred in agricultural land, especially near the shores of Lake Dianchi. The spatial pattern and structure of the change was influenced by the urban sprawl of the city of Kunming. The urban sprawl took on the typical expansion mode of cyclic structures and a jigsaw pattern and expanded to the shore of Lake Dianchi. Agricultural land changed little with respect to the structure but changed greatly in the spatial pattern. The landscape in the watershed showed a trend of fragmentation with a complex boundary. The dynamics of land-use/land-cover in the watershed correlate with land-use policies and economic development in China. PMID:23202820

Proteomic profiling of mitochondria: what does it tell us about the ageing brain?

PubMed

Ingram, Thomas; Chakrabarti, Lisa

2016-12-13

Mitochondrial dysfunction is evident in numerous neurodegenerative and age-related disorders. It has also been linked to cellular ageing, however our current understanding of the mitochondrial changes that occur are unclear. Functional studies have made some progress reporting reduced respiration, dynamic structural modifications and loss of membrane potential, though there are conflicts within these findings. Proteomic analyses, together with functional studies, are required in order to profile the mitochondrial changes that occur with age and can contribute to unravelling the complexity of the ageing phenotype. The emergence of improved protein separation techniques, combined with mass spectrometry analyses has allowed the identification of age and cell-type specific mitochondrial changes in energy metabolism, antioxidants, fusion and fission machinery, chaperones, membrane proteins and biosynthesis pathways. Here, we identify and review recent data from the analyses of mitochondria from rodent brains. It is expected that knowledge gained from understanding age-related mitochondrial changes of the brain should lead to improved biomarkers of normal ageing and also age-related disease progression.

The Secondary Structure of Human Hageman Factor (Factor XII) and its Alteration by Activating Agents

PubMed Central

McMillin, Carl R.; Saito, Hidehiko; Ratnoff, Oscar D.; Walton, Alan G.

1974-01-01

Hageman factor (factor XII) is activated by exposure to surfaces such as glass or by solutions of certain compounds, notably ellagic acid. Changes in the structure of Hageman factor accompanying activation have been examined in this study by circular dichroism spectroscopy. The spectrum of unactivated Hageman factor in aqueous solutions suggests that its conformation is mainly aperiodic. Various perturbants altered the conformation of Hageman factor in differing ways, demonstrating the sensitivity of Hageman factor to its environment. After activation of Hageman factor with solutions of ellagic acid, a negative trough appeared in the region of the circular dichroism spectrum commonly assigned to tyrosine residues, along with other minor changes in the peptide spectral region. Some of these changes are similar to changes that occurred upon partial neutralization of the basic residues at alkali pH. Activation of Hageman factor by adsorption to quartz surfaces (in an aqueous environment) also produced changes similar to those in the ellagic acid-activated Hageman factor, including the negative ellipticity in the tyrosine region. These observations suggest that the activation process may be related to a change in status of some of the basic amino acid residues, coupled with a specific change in the environment of some tyrosine residues. The importance of these changes during the activation process remains to be determined. The sensitivity of Hageman factor to its environment is consistent with the view that the initiation of clotting by exposure of plasma to appropriate agents is brought about by alterations in the conformation of Hageman factor that occur in the apparent absence of Fletcher factor or other recognized clotting factors. Images PMID:4373492

The anatomy of group dysfunction.

PubMed

Hayes, David F

2014-04-01

The dysfunction of the radiology group has 2 components: (1) the thinking component-the governance structure of the radiology group; how we manage the group; and (2) the structural component-the group's business model and its conflict with the partner's personal business model. Of the 2 components, governance is more important. Governance must be structured on classic, immutable business management principles. The structural component, the business model, is not immutable. In fact, it must continually change in response to the marketplace. Changes in the business model should occur only if demanded or permitted by the marketplace; instituting changes for other reasons, including personal interests or deficient knowledge of the deciders, is fundamentally contrary to the long-term interests of the group and its owners. First, we must learn basic business management concepts to appreciate the function and necessity of standard business models and standard business governance. Peter Drucker's The Effective Executive is an excellent primer on the subjects of standard business practices and the importance of a functional, authorized, and fully accountable chief executive officer. Copyright © 2014 American College of Radiology. Published by Elsevier Inc. All rights reserved.

Temperature Dependence of the Structural Parameters in the Transformation of Aragonite to Calcite, as Determined from In Situ Synchrotron Powder X-ray-Diffratction Data

DOE Office of Scientific and Technical Information (OSTI.GOV)

Antao, Sytle M.; Hassan, Ishmael; West Indies)

The temperature dependency of the crystal structure and the polymorphic transition of CaCO{sub 3} from aragonite to calcite were studied using Rietveld structure refinement and high-temperature in situ synchrotron powder X-ray-diffraction data at ambient pressure, P. The orthorhombic metastable aragonite at room P, space group Pmcn, transforms to trigonal calcite, space group R{bar 3}c, at about T{sub c} = 468 C. This transformation occurs rapidly; it starts at about 420 C and is completed by 500 C, an 80 C interval that took about 10 minutes using a heating rate of 8 C/min. Structurally, from aragonite to calcite, the distributionmore » of the Ca atom changes from approximately hexagonal to cubic close-packing. A 5.76% discontinuous increase in volume accompanies the reconstructive first-order transition. Besides the change in coordination of the Ca atom from nine to six from aragonite to calcite, the CO{sub 3} groups change by a 30{sup o} rotation across the transition.« less

Structural responses of metallic glasses under neutron irradiation.

PubMed

Yang, L; Li, H Y; Wang, P W; Wu, S Y; Guo, G Q; Liao, B; Guo, Q L; Fan, X Q; Huang, P; Lou, H B; Guo, F M; Zeng, Q S; Sun, T; Ren, Y; Chen, L Y

2017-12-01

Seeking nuclear materials that possess a high resistance to particle irradiation damage is a long-standing issue. Permanent defects, induced by irradiation, are primary structural changes, the accumulation of which will lead to structural damage and performance degradation in crystalline materials served in nuclear plants. In this work, structural responses of neutron irradiation in metallic glasses (MGs) have been investigated by making a series of experimental measurements, coupled with simulations in ZrCu amorphous alloys. It is found that, compared with crystalline alloys, MGs have some specific structural responses to neutron irradiation. Although neutron irradiation can induce transient vacancy-like defects in MGs, they are fully annihilated after structural relaxation by rearrangement of free volumes. In addition, the rearrangement of free volumes depends strongly on constituent elements. In particular, the change in free volumes occurs around the Zr atoms, rather than the Cu centers. This implies that there is a feasible strategy for identifying glassy materials with high structural stability against neutron irradiation by tailoring the microstructures, the systems, or the compositions in alloys. This work will shed light on the development of materials with high irradiation resistance.

Transient Structures and Possible Limits of Data Recording in Phase-Change Materials.

PubMed

Hu, Jianbo; Vanacore, Giovanni M; Yang, Zhe; Miao, Xiangshui; Zewail, Ahmed H

2015-07-28

Phase-change materials (PCMs) represent the leading candidates for universal data storage devices, which exploit the large difference in the physical properties of their transitional lattice structures. On a nanoscale, it is fundamental to determine their performance, which is ultimately controlled by the speed limit of transformation among the different structures involved. Here, we report observation with atomic-scale resolution of transient structures of nanofilms of crystalline germanium telluride, a prototypical PCM, using ultrafast electron crystallography. A nonthermal transformation from the initial rhombohedral phase to the cubic structure was found to occur in 12 ps. On a much longer time scale, hundreds of picoseconds, equilibrium heating of the nanofilm is reached, driving the system toward amorphization, provided that high excitation energy is invoked. These results elucidate the elementary steps defining the structural pathway in the transformation of crystalline-to-amorphous phase transitions and describe the essential atomic motions involved when driven by an ultrafast excitation. The establishment of the time scales of the different transient structures, as reported here, permits determination of the possible limit of performance, which is crucial for high-speed recording applications of PCMs.

Effect of Se substitution on the phase change properties of Ge2Sb2Te5

NASA Astrophysics Data System (ADS)

Shekhawat, Roopali; Rangappa, Ramanna; Gopal, E. S. R.; Ramesh, K.

2018-05-01

Ge2Sb2Te5 popularly known as GST is being explored for non-volatile phase change random access memory(PCRAM) applications. Under high electric field, thin films of amorphous GST undergo a phase change from amorphous to crystalline with a high contrast in electrical resistivity (about 103). The phase change is between amorphous and metastable NaCl structure occurs at about 150°C and not to the stable hexagonal phase which occurs at a high temperature (> 250 °C). In GST, about 50 % of Te substituted by Se (Ge2Sb2Te2.5Se2.5) is found to increase the contrast in electrical resistivity by 7 orders of magnitude (about 4 orders of magnitude higher than GST). The phase transition in Se added GST also found to be between amorphous and the stable hexagonal structure. The threshold voltage at which the Ge2Sb2Te2.5Se2.5 switches to the high conducting state increases to 9V as compared to 2V in GST. Interestingly, the threshold current decrease to 1mA as compared to 1.8mA in GST indicating the Se substitution reduces the power needed for switching between the low and high conducting states. The reduction in power needed for phase change, high contrast in electrical resistivity with high thermal stability makes Ge2Sb2Te2.5Se2.5 as a better candidate for PCRAM.

Effect of thermal stability on protein adsorption to silica using homologous aldo-keto reductases

PubMed Central

Felsovalyi, Flora; Patel, Tushar; Mangiagalli, Paolo; Kumar, Sanat K; Banta, Scott

2012-01-01

Gaining more insight into the mechanisms governing the behavior of proteins at solid/liquid interfaces is particularly relevant in the interaction of high-value biologics with storage and delivery device surfaces, where adsorption-induced conformational changes may dramatically affect biocompatibility. The impact of structural stability on interfacial behavior has been previously investigated by engineering nonwild-type stability mutants. Potential shortcomings of such approaches include only modest changes in thermostability, and the introduction of changes in the topology of the proteins when disulfide bonds are incorporated. Here we employ two members of the aldo-keto reductase superfamily (alcohol dehydrogenase, AdhD and human aldose reductase, hAR) to gain a new perspective on the role of naturally occurring thermostability on adsorbed protein arrangement and its subsequent impact on desorption. Unexpectedly, we find that during initial adsorption events, both proteins have similar affinity to the substrate and undergo nearly identical levels of structural perturbation. Interesting differences between AdhD and hAR occur during desorption and both proteins exhibit some level of activity loss and irreversible conformational change upon desorption. Although such surface-induced denaturation is expected for the less stable hAR, it is remarkable that the extremely thermostable AdhD is similarly affected by adsorption-induced events. These results question the role of thermal stability as a predictor of protein adsorption/desorption behavior. PMID:22619179

Effect of thermal stability on protein adsorption to silica using homologous aldo-keto reductases.

PubMed

Felsovalyi, Flora; Patel, Tushar; Mangiagalli, Paolo; Kumar, Sanat K; Banta, Scott

2012-08-01

Gaining more insight into the mechanisms governing the behavior of proteins at solid/liquid interfaces is particularly relevant in the interaction of high-value biologics with storage and delivery device surfaces, where adsorption-induced conformational changes may dramatically affect biocompatibility. The impact of structural stability on interfacial behavior has been previously investigated by engineering nonwild-type stability mutants. Potential shortcomings of such approaches include only modest changes in thermostability, and the introduction of changes in the topology of the proteins when disulfide bonds are incorporated. Here we employ two members of the aldo-keto reductase superfamily (alcohol dehydrogenase, AdhD and human aldose reductase, hAR) to gain a new perspective on the role of naturally occurring thermostability on adsorbed protein arrangement and its subsequent impact on desorption. Unexpectedly, we find that during initial adsorption events, both proteins have similar affinity to the substrate and undergo nearly identical levels of structural perturbation. Interesting differences between AdhD and hAR occur during desorption and both proteins exhibit some level of activity loss and irreversible conformational change upon desorption. Although such surface-induced denaturation is expected for the less stable hAR, it is remarkable that the extremely thermostable AdhD is similarly affected by adsorption-induced events. These results question the role of thermal stability as a predictor of protein adsorption/desorption behavior. Copyright © 2012 The Protein Society.

Chemical structures and characteristics of animal manures and composts during composting and assessment of maturity indices

PubMed Central

Huang, Jieying; Yu, Zixuan; Gao, Hongjian; Yan, Xiaoming; Chang, Jiang; Wang, Chengming; Hu, Jingwei

2017-01-01

Changes in physicochemical characteristics, chemical structures and maturity of swine, cattle and chicken manures and composts during 70-day composting without addition of bulking agents were investigated. Physicochemical characteristics were measured by routine analyses and chemical structures by solid-state 13C NMR and FT-IR. Three manures were of distinct properties. Their changes in physicochemical characteristics, chemical structures, and maturity were different not only from each other but also from those with addition of bulking agents during composting. Aromaticity in chicken manure composts decreased at first, and then increased whereas that in cattle and swine manure composts increased. Enhanced ammonia volatilization occurred without addition of bulking agents. NMR structural information indicated that cattle and chicken composts were relatively stable at day 36 and 56, respectively, but swine manure composts were not mature up to day 70. Finally, the days required for three manures to reach the threshold values of different maturity indices were different. PMID:28604783

Autotransporter structure reveals intra-barrel cleavage followed by conformational changes.

PubMed

Barnard, Travis J; Dautin, Nathalie; Lukacik, Petra; Bernstein, Harris D; Buchanan, Susan K

2007-12-01

Autotransporters are virulence factors produced by Gram-negative bacteria. They consist of two domains, an N-terminal 'passenger' domain and a C-terminal beta-domain. beta-domains form beta-barrel structures in the outer membrane while passenger domains are translocated into the extracellular space. In some autotransporters, the two domains are separated by proteolytic cleavage. Using X-ray crystallography, we solved the 2.7-A structure of the post-cleavage state of the beta-domain of EspP, an autotransporter produced by Escherichia coli strain O157:H7. The structure consists of a 12-stranded beta-barrel with the passenger domain-beta-domain cleavage junction located inside the barrel pore, approximately midway between the extracellular and periplasmic surfaces of the outer membrane. The structure reveals an unprecedented intra-barrel cleavage mechanism and suggests that two conformational changes occur in the beta-domain after cleavage, one conferring increased stability on the beta-domain and another restricting access to the barrel pore.

A Framework for Evaluating the Impact of Obesity Prevention Strategies on Socioeconomic Inequalities in Weight

PubMed Central

Beauchamp, Alison; Ball, Kylie; Turrell, Gavin; Martin, Jane; Woods, Julie; Peeters, Anna

2014-01-01

We developed a theoretical framework to organize obesity prevention interventions by their likely impact on the socioeconomic gradient of weight. The degree to which an intervention involves individual agency versus structural change influences socioeconomic inequalities in weight. Agentic interventions, such as standalone social marketing, increase socioeconomic inequalities. Structural interventions, such as food procurement policies and restrictions on unhealthy foods in schools, show equal or greater benefit for lower socioeconomic groups. Many obesity prevention interventions belong to the agento–structural types of interventions, and account for the environment in which health behaviors occur, but they require a level of individual agency for behavioral change, including workplace design to encourage exercise and fiscal regulation of unhealthy foods or beverages. Obesity prevention interventions differ in their effectiveness across socioeconomic groups. Limiting further increases in socioeconomic inequalities in obesity requires implementation of structural interventions. Further empirical evaluation, especially of agento–structural type interventions, remains crucial. PMID:25121810

Identification of time-varying structural dynamic systems - An artificial intelligence approach

NASA Technical Reports Server (NTRS)

Glass, B. J.; Hanagud, S.

1992-01-01

An application of the artificial intelligence-derived methodologies of heuristic search and object-oriented programming to the problem of identifying the form of the model and the associated parameters of a time-varying structural dynamic system is presented in this paper. Possible model variations due to changes in boundary conditions or configurations of a structure are organized into a taxonomy of models, and a variant of best-first search is used to identify the model whose simulated response best matches that of the current physical structure. Simulated model responses are verified experimentally. An output-error approach is used in a discontinuous model space, and an equation-error approach is used in the parameter space. The advantages of the AI methods used, compared with conventional programming techniques for implementing knowledge structuring and inheritance, are discussed. Convergence conditions and example problems have been discussed. In the example problem, both the time-varying model and its new parameters have been identified when changes occur.

Thermodynamics of water structural reorganization due to geometric confinement

NASA Astrophysics Data System (ADS)

Stroberg, Wylie; Lichter, Seth

2015-03-01

Models of aqueous solvation have successfully quantified the behavior of water near convex bodies. However, many important processes occurring in aqueous solution involve interactions between solutes and surfaces with complicated non-convex geometries. Examples include the folding of proteins, hydrophobic association of solutes, ligand-receptor binding, and water confined within nanotubes and pores. For these geometries, models for solvation of convex bodies fail to account for the added interactions associated with structural confinement. Due to water's propensity to form networks of hydrogen bonds, small alterations to the confining geometry can induce large structural rearrangement within the water. We perform systematic Monte Carlo simulations of water confined to cylindrical cavities of varying aspect ratio to investigate how small geometric changes to the confining geometry may cause large changes to the structure and thermodynamic state of water. Using the Wang-Landau algorithm, we obtain free energies, enthalpies, entropies, and heat capacities across a broad range of temperatures, and show how these quantities are influenced by the structural rearrangement of water molecules due to geometric perturbations.

The reliability of multistory buildings with the effect of non-uniform settlements of foundation

NASA Astrophysics Data System (ADS)

Al'Malul, Rafik; Gadzhuntsev, Michail

2018-03-01

The issue is the evaluation of reliability of construction considering the influence of the variation of the support settlement, which is changing during the lifetime of constructions due to the consolidation process of the ground. Recently, the specialists give special emphasis to the necessity to develop the methods for the estimation of reliability and durability of structures. The problem, the article considers, is the determination of the reliability of multistory buildings with non-uniform changing-in-time sediments caused by the consolidation process in soils. Failure of structures may occur before the draft reaches it`s stabilizing value, because of the violations of the conditions of normal use.

Is Cycloxygenase-2 (COX-2) a Major Component of the Mechanism Responsible for Microvascular Remodeling in the Brain?

NASA Astrophysics Data System (ADS)

LaManna, Joseph C.; Sun, Xiaoyan; Ivy, Andre D.; Ward, Nicole L.

We have used a relatively simple model of hypoxia that triggers adaptive structural changes in the cerebral microvasculature to study the process of physiological angiogenesis. This model can be used to obtain mechanistic data for the processes that probably underlie the dynamic structural changes that occur in learning and the control of oxygen availability to the neurovascular unit. These mechanisms are broadly involved in a wide variety of pathophysiological processes. This is the vascular component to CNS functional plasticity, supporting learning and adaptation. The angiogenic process may wane with age, contributing to the decreasing ability to survive metabolic stress and the diminution of neuronal plasticity.

High pressure polymorphs and amorphization of upconversion host material NaY(WO{sub 4}){sub 2}

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hong, Fang; Yue, Binbin, E-mail: yuebb@hpstar.ac.cn, E-mail: chenbin@hpstar.ac.cn; The Advanced Light Source, Lawrence Berkeley National Laboratory, 1 Cyclotron Rd, Berkeley, California 94720

2016-07-25

The pressure effect on the structural change of upconversion host material NaY(WO{sub 4}){sub 2} was studied by using in-situ synchrotron X-ray diffraction. A transition from the initial scheelite phase to the M-fergusonite phase occurs near 10 GPa, and another phase transition is found near 27.5 GPa, which could be an isostructural transition without symmetry change. The sample becomes amorphous when the pressure is fully released from high pressure. This work demonstrates the possibility of synthesizing various polymorph structures for non-linear optical applications with a high pressure, chemical doping, or strained thin-film nanostructure process.

Processing of Building Binder Materials to Increase their Activation

NASA Astrophysics Data System (ADS)

Fediuk, R. S.; Garmashov, I. S.; Kuzmin, D. E.; Stoyushko, N. Yu; Gladkova, N. A.

2018-01-01

The paper deals modern physical methods of activation of building powder materials. During mechanical activation a composite binder active molecules cement minerals occur in the destruction of the molecular defects in the areas of packaging and breaking metastable phase decompensation intermolecular forces. The process is accompanied by a change in the kinetics of hardening of Portland cement. Activated concrete has a number of features that are used as design characteristics of structures and are due to the structure of the activated binder and its contacts with concrete aggregates. These features also have a significant impact on the nature of the destruction of concrete under load, changing the boundaries of its microcracks and durability.

Alternative approaches used to assess structural changes of natural zircon caused by heat treatment

NASA Astrophysics Data System (ADS)

Huong, L. T. T.; Thuyet, N. T. M.; Phan, T. L.; Tran, N.; Toan, D. N.; Thang, P. D.; Huy, B. T.

2018-03-01

It is known that large changes in the crystal structure of zircon (ZrSiO4) can be assessed through the linewidth of the characteristic Raman mode (Δν3) at 1008 cm-1. However, the use of Δν3 to assess small changes caused by heat treatment at temperatures below its decomposition temperature of 1670 °C is difficult. The present work points out that the combination of X-ray diffraction (XRD) analyses, and photoluminescence (PL) and Raman (RS) measurements with different excitation wavelengths is an effective approach to solve the above problem. In this context, we have selected natural zircon containing some rare-earth (RE) impurities, and then studied the changes in its crystal structure caused by heat treatment at temperatures Tan=400-1600 °C. XRD analyses reveal that small modifications of the unit-cell parameters occur as Tan>600 °C. Taking the intensity ratios of the ν3 mode to RE-related emissions (Iν3/IRE) or the PL intensity ratios between RE-related emissions into consideration, the similar results in good agreement with the XRD analyses are also found. We believe that the small structural changes are related to the migration and redistribution of defects and impurities, and re-crystallization of zircon. This could be further confirmed though the relation between paramagnetic and ferromagnetic signals when Tan changes.

Investigating ion channel conformational changes using voltage clamp fluorometry.

PubMed

Talwar, Sahil; Lynch, Joseph W

2015-11-01

Ion channels are membrane proteins whose functions are governed by conformational changes. The widespread distribution of ion channels, coupled with their involvement in most physiological and pathological processes and their importance as therapeutic targets, renders the elucidation of these conformational mechanisms highly compelling from a drug discovery perspective. Thanks to recent advances in structural biology techniques, we now have high-resolution static molecular structures for members of the major ion channel families. However, major questions remain to be resolved about the conformational states that ion channels adopt during activation, drug modulation and desensitization. Patch-clamp electrophysiology has long been used to define ion channel conformational states based on functional criteria. It achieves this by monitoring conformational changes at the channel gate and cannot detect conformational changes occurring in regions distant from the gate. Voltage clamp fluorometry involves labelling cysteines introduced into domains of interest with environmentally sensitive fluorophores and inferring structural rearrangements from voltage or ligand-induced fluorescence changes. Ion channel currents are monitored simultaneously to verify the conformational status. By defining real time conformational changes in domains distant from the gate, this technique provides unexpected new insights into ion channel structure and function. This review aims to summarise the methodology and highlight recent innovative applications of this powerful technique. This article is part of the Special Issue entitled 'Fluorescent Tools in Neuropharmacology'. Copyright © 2015 Elsevier Ltd. All rights reserved.

[Effects of land use structure change on regional ecological health--taking Shapingba County as an example].

PubMed

Wang, Cheng; Wei, Chaofu; Gao, Ming; Luo, Guanglian; Jiang, Wei

2005-12-01

Land resource is the carrier for the exchange of matter, energy and information flows, while the change velocity and the intensity of land use has strong effects on the ecological processes such as matter circulation, energy flow, and biologic diversity. Land use structure change will alter the type, area, and spatial distribution of ecosystem, and in the meantime, result in the changes of regional ecological health. Employing the principles and methods of landscape ecology, and through endowing relative ecological value to land use type, this paper analyzed the charaeteristics of recent 10 years land use change in Shapingba County of Chongqing, and discussed the effects of land use change on regional ecological health, aimed to provide scientific references for land use planning and sustainable land resource utilization. The results indicated that transformation often occurred among different land use types, and the land use structure in each transformation phase differed quite obviously. Under different land use structure, there was a great disparity in relative ecological value of sub-ecosystems, which played various roles in regional ecological health. In general, the regional relative ecological value embodied both increase and decrease. In the future, the relative ecological value of sub-ecosystem would represent three tendencies, i.e., increase first and decrease then, continuous decrease, and continuous increase. The situation of regional ecological health would gradually become better.

Architectural and biochemical adaptations in skeletal muscle and bone following rotator cuff injury in a rat model.

PubMed

Sato, Eugene J; Killian, Megan L; Choi, Anthony J; Lin, Evie; Choo, Alexander D; Rodriguez-Soto, Ana E; Lim, Chanteak T; Thomopoulos, Stavros; Galatz, Leesa M; Ward, Samuel R

2015-04-01

Injury to the rotator cuff can cause irreversible changes to the structure and function of the associated muscles and bones. The temporal progression and pathomechanisms associated with these adaptations are unclear. The purpose of this study was to investigate the time course of structural muscle and osseous changes in a rat model of a massive rotator cuff tear. Supraspinatus and infraspinatus muscle architecture and biochemistry and humeral and scapular morphological parameters were measured three days, eight weeks, and sixteen weeks after dual tenotomy with and without chemical paralysis via botulinum toxin A (BTX). Muscle mass and physiological cross-sectional area increased over time in the age-matched control animals, decreased over time in the tenotomy+BTX group, and remained nearly the same in the tenotomy-alone group. Tenotomy+BTX led to increased extracellular collagen in the muscle. Changes in scapular bone morphology were observed in both experimental groups, consistent with reductions in load transmission across the joint. These data suggest that tenotomy alone interferes with normal age-related muscle growth. The addition of chemical paralysis yielded profound structural changes to the muscle and bone, potentially leading to impaired muscle function, increased muscle stiffness, and decreased bone strength. Structural musculoskeletal changes occur after tendon injury, and these changes are severely exacerbated with the addition of neuromuscular compromise. Copyright © 2015 by The Journal of Bone and Joint Surgery, Incorporated.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pfiffner, Susan M.; Brandt, Craig C.; Kostka, Joel E.

Our current research represents a joint effort between Oak Ridge National Laboratory (ORNL), Florida State University (FSU), and the University of Tennessee. ORNL will serve as the lead institution with Dr. A.V. Palumbo responsible for project coordination, integration, and deliverables. This project was initiated in November, 2004, in the Integrative Studies Element of the NABIR program. The overall goal of our project is to provide an improved understanding of the relationships between microbial community structure, geochemistry, and metal reduction rates. The research seeks to address the following questions: Is the metabolic diversity of the in situ microbial community sufficiently largemore » and redundant that bioimmobilization of uranium will occur regardless of the type of electron donor added to the system? Are their donor specific effects that lead to enrichment of specific community members that then impose limits on the functional capabilities of the system? Will addition of humics change rates of uranium reduction without changing community structure? Can resource-ratio theory be used to understand changes in uranium reduction rates and community structure with respect to changing C:P ratios?« less

Effect of space structures against development of transport infrastructure in Banda Aceh by using the concept of transit oriented development

NASA Astrophysics Data System (ADS)

Noer, Fadhly; Matondang, A. Rahim; Sirojuzilam, Saleh, Sofyan M.

2017-11-01

Due to the shifting of city urban development causing the shift of city services center, so there is a change in space pattern and space structure in Banda Aceh, then resulting urban sprawl which can lead to congestion problem occurs on the arterial road in Banda Aceh, it can be seen from the increasing number of vehicles per year by 6%. Another issue occurs by urban sprawl is not well organized of settlement due to the uncontrolled use of space so that caused grouping or the differences in socioeconomic strata that can impact to the complexity of population mobility problem. From this background problem considered to be solved by a concept that is Transit Oriented Development (TOD), that is a concept of transportation development in co-operation with spatial. This research will get the model of transportation infrastructure development with TOD concept that can handle transportation problem in Banda Aceh, due to change of spatial structure, and to find whether TOD concept can use for the area that has a population in medium density range. The result that is obtained equation so the space structure is: Space Structure = 0.520 + 0.206X3 + 0.264X6 + 0.100X7 and Transportation Infrastructure Development = -1.457 + 0.652X1 + 0.388X5 + 0.235X6 + 0.222X7 + 0.327X8, So results obtained with path analysis method obtained variable influences, node ratio, network connectivity, travel frequency, travel destination, travel cost, and travel time, it has a lower value when direct effect with transportation infrastructure development, but if the indirect effect through the structure of space has a greater influence, can be seen from spatial structure path scheme - transportation infrastructure development.

Common 5S rRNA variants are likely to be accepted in many sequence contexts

NASA Technical Reports Server (NTRS)

Zhang, Zhengdong; D'Souza, Lisa M.; Lee, Youn-Hyung; Fox, George E.

2003-01-01

Over evolutionary time RNA sequences which are successfully fixed in a population are selected from among those that satisfy the structural and chemical requirements imposed by the function of the RNA. These sequences together comprise the structure space of the RNA. In principle, a comprehensive understanding of RNA structure and function would make it possible to enumerate which specific RNA sequences belong to a particular structure space and which do not. We are using bacterial 5S rRNA as a model system to attempt to identify principles that can be used to predict which sequences do or do not belong to the 5S rRNA structure space. One promising idea is the very intuitive notion that frequently seen sequence changes in an aligned data set of naturally occurring 5S rRNAs would be widely accepted in many other 5S rRNA sequence contexts. To test this hypothesis, we first developed well-defined operational definitions for a Vibrio region of the 5S rRNA structure space and what is meant by a highly variable position. Fourteen sequence variants (10 point changes and 4 base-pair changes) were identified in this way, which, by the hypothesis, would be expected to incorporate successfully in any of the known sequences in the Vibrio region. All 14 of these changes were constructed and separately introduced into the Vibrio proteolyticus 5S rRNA sequence where they are not normally found. Each variant was evaluated for its ability to function as a valid 5S rRNA in an E. coli cellular context. It was found that 93% (13/14) of the variants tested are likely valid 5S rRNAs in this context. In addition, seven variants were constructed that, although present in the Vibrio region, did not meet the stringent criteria for a highly variable position. In this case, 86% (6/7) are likely valid. As a control we also examined seven variants that are seldom or never seen in the Vibrio region of 5S rRNA sequence space. In this case only two of seven were found to be potentially valid. The results demonstrate that changes that occur multiple times in a local region of RNA sequence space in fact usually will be accepted in any sequence context in that same local region.

Protein-protein binding before and after photo-modification of albumin

NASA Astrophysics Data System (ADS)

Rozinek, Sarah C.; Glickman, Randolph D.; Thomas, Robert J.; Brancaleon, Lorenzo

2016-03-01

Bioeffects of directed-optical-energy encompass a wide range of applications. One aspect of photochemical interactions involves irradiating a photosensitizer with visible light in order to induce protein unfolding and consequent changes in function. In the past, irradiation of several dye-protein combinations has revealed effects on protein structure. Beta lactoglobulin, human serum albumin (HSA) and tubulin have all been photo-modified with meso-tetrakis(4- sulfonatophenyl)porphyrin (TSPP) bound, but only in the case of tubulin has binding caused a verified loss of biological function (loss of ability to form microtubules) as a result of this light-induced structural change. The current work questions if the photo-induced structural changes that occur to HSA, are sufficient to disable its biological function of binding to osteonectin. The albumin-binding protein, osteonectin, is about half the molecular weight of HSA, so the two proteins and their bound product can be separated and quantified by size exclusion high performance liquid chromatography. TSPP was first bound to HSA and irradiated, photo-modifying the structure of HSA. Then native HSA or photo-modified HSA (both with TSPP bound) were compared, to assess loss in HSA's innate binding ability as a result of light-induced structure modification.

Effect of Al-doped YCrO3 on structural, electronic and magnetic properties

NASA Astrophysics Data System (ADS)

Durán, A.; Verdín, E.; Conde, A.; Escamilla, R.

2018-05-01

Structural, dielectric and magnetic properties were investigated in the YCr1-xAlxO3 with 0 < x < 0.5 compositions. XRD and XPS studies show that the partial substitution of the Al3+ ion decreases the cell volume of the orthorhombic structure without changes in the oxidation state of the Cr3+ ions. We discuss two mechanisms that could have a significant influence on the magnetic properties. The first is related to local deformation occurring for x < 0.1 of Al content and the second is related to change of the electronic structure. The local deformation is controlled by the inclination of the octahedrons and the octahedral distortion having a strong effect on the TN and the coercive field at low Al concentrations. On the other hand, the decreasing of the magnetization values (Mr and Hc) is ascribed to changes in the electronic structure, which is confirmed by a decreasing of the contribution of Cr 3d states at Fermi level due to increasing Al3+ content. Thus, we analyzed and discussed that both mechanisms influence the electronic properties of the YCr1-xAlxO3 solid solution.

Viewing Golgi structure and function from a different perspective--insights from electron tomography.

PubMed

Marsh, Brad J; Pavelka, Margit

2013-01-01

Historically, ultrastructural investigations, which have focused on elucidating the biological idiosyncrasies of the Golgi apparatus, have tended towards oversimplified or fallacious hypotheses when postulating how the Golgi apparatus reorganizes itself both structurally and functionally to fulfill the plethora of cellular processes underpinned by this complex organelle. Key questions are still unanswered with regard to how changes in Golgi architecture correlate so reproducibly to changes in its functional priorities under different physiological conditions or experimental perturbations. This fact alone serves to highlight how the technical limitations associated with conventional two-dimensional imaging approaches employed in the past failed to adequately capture the extraordinary complexity of the Golgi's three-dimensional (3D) structure-now a hallmark of this challenging organelle. Consequently, this has hampered progress towards developing a clear understanding of how changes in its structure and function typically occur in parallel. In this chapter, we highlight but a few of the significant new insights regarding variations in the Golgi's structure-function relationships that have been afforded over recent years through advanced electron microscopic techniques for 3D image reconstruction, commonly referred to as electron tomography. Copyright © 2013 Elsevier Inc. All rights reserved.

The Drug-Resistant Variant P167S Expands the Substrate Profile of CTX-M β-Lactamases for Oxyimino-Cephalosporin Antibiotics by Enlarging the Active Site upon Acylation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Patel, Meha P.; Hu, Liya; Stojanoski, Vlatko

β-Lactamases are enzymes produced by bacterial cells that provide resistance to β-lactam antibiotics. The CTX-M class of β-lactamases provides resistance against the antibiotic, cefotaxime, but not a related oxyimino-cephalosporin antibiotic, ceftazidime. β-lactamases that carry the P167S substitution, however, have been reported to provide ceftazidime resistance. The mechanism by which the P167S substitution expands the substrate profile of CTX-M enzymes is not known. In this study, CTX-M-14 was used as the model enzyme to study the structural changes caused by the P167S mutation that may accelerate ceftazidime turnover. X-ray crystallography was used to determine the structures of the CTX-M-14 P167S apo-enzymemore » along with the structures of the S70G/P167S, E166A/P167S and E166A mutant enzymes complexed with ceftazidime as well as the E166A/P167S apo-enzyme. The S70G and E166A mutations allow the capture of the enzyme-substrate complex and acylated forms of the ceftazidime molecule, respectively. The results showed a large conformational change in the Ω-loop of the CTX-M-14 ceftazidime acyl-enzyme complex of the P167S mutant but not in the enzyme-substrate complex suggesting the conformational change occurs upon acylation. The conformational change results in a larger active site cavity that prevents steric clash between the aminothiazole ring of ceftazidime and the Asn170 residue in the Ω-loop, allowing for accommodation of ceftazidime for hydrolysis. In addition, the conformational change in the Ω-loop was not observed in the E166A/P167S apoenzyme, suggesting the presence of acylated ceftazidime influences the conformational change. Finally, the E166A acyl-enzyme structure with ceftazidime did not exhibit the altered Ω-loop conformation, indicating the P167S substitution is required for the change. Taken together, the results reveal that the P167S substitution and the presence of acylated ceftazidime both drive the structure towards a conformational change of the Ω-loop and that in CTX-M P167S enzymes found in drug-resistant bacteria this will lead to increased ceftazidime hydrolysis. Lastly, this study demonstrates how a naturally occurring substitution can dramatically alter the active site to expand the substrate profile of an enzyme due to antibiotic selective pressure.« less

The Drug-Resistant Variant P167S Expands the Substrate Profile of CTX-M β-Lactamases for Oxyimino-Cephalosporin Antibiotics by Enlarging the Active Site upon Acylation

DOE PAGES

Patel, Meha P.; Hu, Liya; Stojanoski, Vlatko; ...

2017-06-14

β-Lactamases are enzymes produced by bacterial cells that provide resistance to β-lactam antibiotics. The CTX-M class of β-lactamases provides resistance against the antibiotic, cefotaxime, but not a related oxyimino-cephalosporin antibiotic, ceftazidime. β-lactamases that carry the P167S substitution, however, have been reported to provide ceftazidime resistance. The mechanism by which the P167S substitution expands the substrate profile of CTX-M enzymes is not known. In this study, CTX-M-14 was used as the model enzyme to study the structural changes caused by the P167S mutation that may accelerate ceftazidime turnover. X-ray crystallography was used to determine the structures of the CTX-M-14 P167S apo-enzymemore » along with the structures of the S70G/P167S, E166A/P167S and E166A mutant enzymes complexed with ceftazidime as well as the E166A/P167S apo-enzyme. The S70G and E166A mutations allow the capture of the enzyme-substrate complex and acylated forms of the ceftazidime molecule, respectively. The results showed a large conformational change in the Ω-loop of the CTX-M-14 ceftazidime acyl-enzyme complex of the P167S mutant but not in the enzyme-substrate complex suggesting the conformational change occurs upon acylation. The conformational change results in a larger active site cavity that prevents steric clash between the aminothiazole ring of ceftazidime and the Asn170 residue in the Ω-loop, allowing for accommodation of ceftazidime for hydrolysis. In addition, the conformational change in the Ω-loop was not observed in the E166A/P167S apoenzyme, suggesting the presence of acylated ceftazidime influences the conformational change. Finally, the E166A acyl-enzyme structure with ceftazidime did not exhibit the altered Ω-loop conformation, indicating the P167S substitution is required for the change. Taken together, the results reveal that the P167S substitution and the presence of acylated ceftazidime both drive the structure towards a conformational change of the Ω-loop and that in CTX-M P167S enzymes found in drug-resistant bacteria this will lead to increased ceftazidime hydrolysis. Lastly, this study demonstrates how a naturally occurring substitution can dramatically alter the active site to expand the substrate profile of an enzyme due to antibiotic selective pressure.« less

Study on control of defect mode in hybrid mirror chirped porous silicon photonic crystal

NASA Astrophysics Data System (ADS)

Chen, Ying; Luo, Pei; Han, Yangyang; Cui, Xingning; He, Lei

2018-03-01

Based on the optical resonance principle and the tight-binding theory, a hybrid mirror chirped porous silicon photonic crystal is proposed. The control of the defect mode in hybrid mirror chirped porous silicon photonic crystal is studied. Through the numerical simulation, the control regulations of the defect modes resulted by the number of the periodical layers for the fundamental unit and the cascading number of the chirped structures are analyzed, and the split and the degeneration of the defect modes resulted by the change of the relative location between the mirror structures and the quasi-mirror structures are discussed. The simulation results show that the band gap would be broadened with the increase of the chirp quantity and the layer number of unilateral chirp. Adjusting the structural parameters of the hybrid mirror structure, the multimode characteristics will occur in the band gap. The more the cascading number of the chirped units, the more the number of the filtering channels will be. In addition, with the increase of the relative location between the mirror structures and the quasi-mirror structures, the degeneration of the defect modes will occur and can obtain high Q value. The structure can provide effective theoretical references for the design the multi-channel filters and high Q value sensors.

Photonic crystal fiber sensing characteristics research based on alcohol asymmetry filling

NASA Astrophysics Data System (ADS)

Shi, Fu-quan; Luo, Yan; Li, Hai-tao; Peng, Bao-jin

2018-02-01

A new type of Sagnac fiber temperature sensor based on alcohol asymmetric filling photonic crystal fiber is proposed. First, the corrosion of photonic crystal fiber and the treatment of air hole collapse are carried out. Then, the asymmetric structure of photonic crystal fiber is filled with alcohol, and then the structure is connected to the Sagnac interference ring. When the temperature changes, the thermal expansion effect of filling alcohol will lead to the change of birefringence of photonic crystal fiber, so that the interference spectrum of the sensor will drift along with the change of temperature. The experimental results show that the interference red shift will occur with the increase of temperature, and the temperature sensitivity is 0.1864nm/ °C. The sensor has high sensitivity to temperature. At the same time, the structure has the advantages of high stability, anti electromagnetic interference and easy to build. It provides a new method for obtaining birefringence in ordinary photonic crystal fibers.

Louisiana's forests, 2013

Treesearch

Sonja N. Oswalt

2016-01-01

The principle findings of the 2013 forest survey in the State of Louisiana and changes that have occurred since previous surveysare presented. Topics examined include forest area, ownership, forest-type groups, stand structure, timber volume, growth, removals, and mortality. Emerald ash borer and invasive plants are also discussed in the context of...

Genome-wide analysis of allele frequency change in sunflower crop-wild hybrid populations evolving under natural conditions

USDA-ARS?s Scientific Manuscript database

Hybridization is known to occur between cultivated and wild populations of numerous plant species. This represents a major mechanism by which a wild population’s genetic structure and evolutionary dynamics could be altered. Studying crop-derived alleles in wild populations is also relevant to assess...

Mississippi’s forests, 2013

Treesearch

Sonja N. Oswalt

2015-01-01

The principle findings of the 2013 forest survey in the State of Mississippi and changes that have occurred since previous surveys are presented. Topics examined include forest area, ownership, forest-type groups, stand structure, timber volume, growth, removals, and mortality. Emerald ash borer and invasive plants are also discussed in the context of Mississippi’s...

Toward a Methodology for Conducting Social Impact Assessments Using Quality of Social Life Indicators.

ERIC Educational Resources Information Center

Olsen, Marvin E.; Merwin, Donna J.

Broadly conceived, social impacts refer to all changes in the structure and functioning of patterned social ordering that occur in conjunction with an environmental, technological, or social innovation or alteration. Departing from the usual cost-benefit analysis approach, a new methodology proposes conducting social impact assessment grounded in…

FOLLOW-UP ANALYSIS OF MADISON JUNIOR HIGH SCHOOL.

ERIC Educational Resources Information Center

CLAYTON, THOMAS E.; AND OTHERS

OVER A PERIOD OF 2 YEARS, A DRAMATIC TRANSFORMATION HAS OCCURRED IN THE LEARNING CLIMATE OF THE SCHOOL. THE TENSION AND HOSTILITY, PRESENT IN MANY OF THE CLASSES OBSERVED IN 1961, HAVE LARGELY DISAPPEARED. WITH A MINIMUM OF STRUCTURAL CHANGES, THE PHYSICAL FACILITIES HAVE BEEN GREATLY IMPROVED. BRIGHT COLORS, LARGE BULLETIN BOARDS, AND DISPLAYS OF…

The porous borders of the protein world.

PubMed

Cordes, Matthew H J; Stewart, Katie L

2012-02-08

Fold switching may play a role in the evolution of new protein folds and functions. He et al., in this issue of Structure, use protein design to illustrate that the same drastic change in a protein fold can occur via multiple different mutational pathways. Copyright © 2012 Elsevier Ltd. All rights reserved.

Using Point Clouds Generated from Unmanned Aerial Vehicles Imagery Processed with Structure from Motion to Address Tsunami vs Storm Wave Boulder Deposition in Watu Karung, Indonesia

NASA Astrophysics Data System (ADS)

Uribe, A. T.; Bunds, M. P.; Andreini, J.; Horns, D. M.; Harris, R. A.; Prasetyadi, C.; Yulianto, E.; Putra, P. S.

2017-12-01

Tsunamis pose a major hazard to coastal communities along the south coast of much of Indonesia due its location on the Australian-Sunda arc. Furthermore, tsunamis and high-energy wave events are the principal drivers of geomorphic change in the area and it is difficult to distinguish the effects of each. A potentially useful indicator of past tsunami activity is coastal imbricated boulder deposits. To address whether an imbricated boulder deposit located on a beach in Watu Karung (Java, Indonesia) could have been formed by non-tsunami wave activity and to investigate coastal geomorphic change, we generated three pairs of digital surface models (DSMs) over an approximately one year period using photographs taken from a small unmanned aerial vehicle and structure-from-motion photogrammetry. The first two DSMs were made from photographs taken on 7/30-31/2016 and 8/2/2016, immediately before and after a significant 4.2 m swell struck the beach during a +2.5 m spring high tide. The third DSM pair was made from imagery collected 7/12/2017. Each pair of DSMs consists of a 1 cm pixel DSM of the boulder deposit and a 4 cm DSM of the larger beach area that surrounds the boulders. In addition, prior to the 2016 wave event 21 boulders up to 75 kg were marked and hand-placed shoreward of the boulder deposit; their movement was tracked with RTK GPS measurements. In the 2016 wave event, every hand-placed boulder moved, with an average displacement of 27.6 m. At the same time, approximately 20 of 650 naturally - occurring boulders, up to 2 m in length, moved more than 10 cm and up to 5.6 m. Between 2016 and 2017, approximately 300 of 650 naturally - occurring boulders with an average length of 1.6 m moved varying distances of at least 10 cm and up to 30 m. In addition, changes in beach sand volume occurred in ten 25 m2 localized zones on the beach with an average volume change of approximately 65 m2. Changes in both boulder position and sand volume occurred during the 2016 to 2017 time period when no tsunamis affected Watu Karung—thus indicating that all changes were the result of storm wave events.

Inner Ear Barotrauma After Underwater Pool Competency Training Without the Use of Compressed Air Case and Review.

PubMed

McIntire, Sean; Boujie, Lee

2016-01-01

Inner ear barotrauma can occur when the gas-filled chambers of the ear have difficulty equalizing pressure with the outside environment after changes in ambient pressure. This can transpire even with small pressure changes. Hypobaric or hyperbaric environments can place significant stress on the structures of the middle and inner ear. If methods to equalize pressure between the middle ear and other connected gas-filled spaces (i.e., Valsalva maneuver) are unsuccessful, middle ear overpressurization can occur. This force can be transmitted to the fluid-filled inner ear, making it susceptible to injury. Damage specifically to the structures of the vestibulocochlear system can lead to symptoms of vertigo, hearing loss, and tinnitus. This article discusses the case of a 23-year-old male Marine who presented with symptoms of nausea and gait instability after performing underwater pool competency exercises to a maximum depth of 13 feet, without breathing compressed air. Diagnosis and management of inner ear barotrauma are reviewed, as is differentiation from inner ear decompression sickness. 2016.

Effects of salt concentration and pH on structural and functional properties of Lactobacillus acidophilus: FT-IR spectroscopic analysis.

PubMed

Gandhi, Akanksha; Shah, Nagendra P

2014-03-03

The effects of sodium chloride concentration and varying pH levels on the structural and functional properties of Lactobacillus acidophilus were investigated. Reconstituted skim milk was inoculated with Lb. acidophilus at varying salt concentrations (0, 1, 2, 5 and 10% NaCl) and pH levels (4.0, 5.0 and 6.0) and ACE-inhibitory activity and proteolytic activity were determined and the viable cell count was enumerated after 24h of fermentation at 37 °C. The degree of proteolysis exhibited an increase with higher salt concentration at pH 5.0 and 6.0. ACE-inhibitory activity was found to be the highest at pH 5.0 at all salt concentrations. Fourier transform infrared spectroscopy results demonstrated significant changes occurring beyond 2% NaCl particularly at low pH (4.0). The findings revealed that significant changes occurred in amide I and amide III regions when Lb. acidophilus was subjected to varying salt concentrations. Copyright © 2014 Elsevier B.V. All rights reserved.

Surface chemical structure of poly(ethylene naphthalate) films during degradation in low-pressure high-frequency plasma treatments

NASA Astrophysics Data System (ADS)

Kamata, Noritsugu; Yuji, Toshifumi; Thungsuk, Nuttee; Arunrungrusmi, Somchai; Chansri, Pakpoom; Kinoshita, Hiroyuki; Mungkung, Narong

2018-06-01

The surface chemical structure of poly(ethylene naphthalate) (PEN) films treated with a low-pressure, high-frequency plasma was investigated by storing in a box at room temperature to protect the PEN film surface from dust. The functional groups on the PEN film surface changed over time. The functional groups of –C=O, –COH, and –COOH were abundant in the Ar + O2 mixture gas plasma-treated PEN samples as compared with those in untreated PEN samples. The changes occurred rapidly after 2 d following the plasma treatment, reaching steady states 8 d after the treatment. Hydrophobicity had an inverse relationship with the concentration of these functional groups on the surface. Thus, the effect of the low-pressure high-frequency plasma treatment on PEN varies as a function of storage time. This means that radical oxygen and oxygen molecules are clearly generated in the plasma, and this is one index to confirm that radical reaction has definitely occurred between the gas and the PEN film surface with a low-pressure high-frequency plasma.

A Posteriori Comparison of Natural and Surgical Destabilization Models of Canine Osteoarthritis

PubMed Central

Pelletier, Jean-Pierre; d'Anjou, Marc-André; Blond, Laurent; Pelletier, Johanne-Martel; del Castillo, Jérôme R. E.

2013-01-01

For many years Canis familiaris, the domestic dog, has drawn particular interest as a model of osteoarthritis (OA). Here, we optimized the dog model of experimental OA induced by cranial cruciate ligament sectioning. The usefulness of noninvasive complementary outcome measures, such as gait analysis for the limb function and magnetic resonance imaging for structural changes, was demonstrated in this model. Relationships were established between the functional impairment and the severity of structural changes including the measurement of cartilage thinning. In the dog model of naturally occurring OA, excellent test-retest reliability was denoted for the measurement of the limb function. A criterion to identify clinically meaningful responders to therapy was determined for privately owned dogs undergoing clinical trials. In addition, the recording of accelerometer-based duration of locomotor activity showed strong and complementary agreement with the biomechanical limb function. The translation potential of these models to the human OA condition is underlined. A preclinical testing protocol which combines the dog model of experimental OA induced by cranial cruciate ligament transection and the Dog model of naturally occurring OA offers the opportunity to further investigate the structural and functional benefits of disease-modifying strategies. Ultimately, a better prediction of outcomes for human clinical trials would be brought. PMID:24288664

Utilizing biotechnology in producing fats and oils with various nutritional properties.

PubMed

Flickinger, Brent D

2007-01-01

The role of dietary fat in health and wellness continues to evolve. In today's environment, trans fatty acids and obesity are issues that are impacted by dietary fat. In response to new information in these areas, changes in the amount and composition of edible fats and oils have occurred and are occurring. These compositional changes include variation in fatty acid composition and innovation in fat structure. Soybean, canola, and sunflower are examples of oilseeds with varied fatty acid composition, including mid-oleic, high-oleic, and low-linolenic traits. These trait-enhanced oils are aimed to displace partially hydrogenated vegetable oils primarily in frying applications. Examples of oils with innovation in fat structure include enzyme interesterified (EIE) fats and oils and diacylglycerol oil. EIE fats are a commercial edible fat innovation, where a lipase is used to modify the fat structure of a blend of hard fat and liquid oil. EIE fats are aimed to displace partially hydrogenated vegetable oils in baking and spread applications. Diacylglycerol and medium-chain triglyceride (MCT)-based oils are commercial edible oil innovations. Diacylglycerol and MCT-based oils are aimed for individuals looking to store less of these fats as body fat when they are used in place of traditional cooking and salad oils.

Evolution: Language Use and the Evolution of Languages

NASA Astrophysics Data System (ADS)

Croft, William

Language change can be understood as an evolutionary process. Language change occurs at two different timescales, corresponding to the two steps of the evolutionary process. The first timescale is very short, namely, the production of an utterance: this is where linguistic structures are replicated and language variation is generated. The second timescale is (or can be) very long, namely, the propagation of linguistic variants in the speech community: this is where certain variants are selected over others. At both timescales, the evolutionary process is driven by social interaction and the role language plays in it. An understanding of social interaction at the micro-level—face-to-face interactions—and at the macro-level—the structure of speech communities—gives us the basis for understanding the generation and propagation of language structures, and understanding the nature of language itself.

Excitation energy shift and size difference of low-energy levels in p -shell Λ hypernuclei

NASA Astrophysics Data System (ADS)

Kanada-En'yo, Yoshiko

2018-02-01

Structures of low-lying 0 s -orbit Λ states in p -shell Λ hypernuclei (ZAΛ) are investigated by applying microscopic cluster models for nuclear structure and a single-channel folding potential model for a Λ particle. For A >10 systems, the size reduction of core nuclei is small, and the core polarization effect is regarded as a higher-order perturbation in the Λ binding. The present calculation qualitatively describes the systematic trend of experimental data for excitation energy change from Z-1A to ZAΛ, in A >10 systems. The energy change shows a clear correlation with the nuclear size difference between the ground and excited states. In Li7Λ and Be9Λ, the significant shrinkage of cluster structures occurs consistently with the prediction of other calculations.

Atomic resolution of structural changes in elastic crystals of copper(II) acetylacetonate

NASA Astrophysics Data System (ADS)

Worthy, Anna; Grosjean, Arnaud; Pfrunder, Michael C.; Xu, Yanan; Yan, Cheng; Edwards, Grant; Clegg, Jack K.; McMurtrie, John C.

2018-01-01

Single crystals are typically brittle, inelastic materials. Such mechanical responses limit their use in practical applications, particularly in flexible electronics and optical devices. Here we describe single crystals of a well-known coordination compound—copper(II) acetylacetonate—that are flexible enough to be reversibly tied into a knot. Mechanical measurements indicate that the crystals exhibit an elasticity similar to that of soft materials such as nylon, and thus display properties normally associated with both hard and soft matter. Using microfocused synchrotron radiation, we mapped the changes in crystal structure that occur on bending, and determined the mechanism that allows this flexibility with atomic precision. We show that, under strain, the molecules in the crystal reversibly rotate, and thus reorganize to allow the mechanical compression and expansion required for elasticity and still maintain the integrity of the crystal structure.

Hydra effects in stable communities and their implications for system dynamics.

PubMed

Cortez, Michael H; Abrams, Peter A

2016-05-01

A hydra effect occurs when the mean density of a species increases in response to greater mortality. We show that, in a stable multispecies system, a species exhibits a hydra effect only if maintaining that species at its equilibrium density destabilizes the system. The stability of the original system is due to the responses of the hydra-effect species to changes in the other species' densities. If that dynamical feedback is removed by fixing the density of the hydra-effect species, large changes in the community make-up (including the possibility of species extinction) can occur. This general result has several implications: (1) Hydra effects occur in a much wider variety of species and interaction webs than has previously been described, and may occur for multiple species, even in small webs; (2) conditions for hydra effects caused by predators (or diseases) often differ from those caused by other mortality factors; (3) introducing a specialist or a switching predator of a hydra-effect species often causes large changes in the community, which frequently involve extinction of other species; (4) harvest policies that attempt to maintain a constant density of a hydra-effect species may be difficult to implement, and, if successful, are likely to cause large changes in the densities of other species; and (5) trophic cascades and other indirect effects caused by predators of hydra-effect species can exhibit amplification of effects or unexpected directions of change. Although we concentrate on systems that are originally stable and models with no stage-structure or trait variation, the generality of our result suggests that similar responses to mortality will occur in many systems without these simplifying assumptions. In addition, while hydra effects are defined as responses to altered mortality, they also imply counterintuitive responses to changes in immigration and other parameters affecting population growth.

Changes in the Golgi Apparatus of Neocortical and Hippocampal Neurons in the Hibernating Hamster.

PubMed

Antón-Fernández, Alejandro; León-Espinosa, Gonzalo; DeFelipe, Javier; Muñoz, Alberto

2015-01-01

Hibernating animals have been used as models to study several aspects of the plastic changes that occur in the metabolism and physiology of neurons. These models are also of interest in the study of Alzheimer's disease because the microtubule-associated protein tau is hyperphosphorylated during the hibernation state known as torpor, similar to the pretangle stage of Alzheimer's disease. Hibernating animals undergo torpor periods with drops in body temperature and metabolic rate, and a virtual cessation of neural activity. These processes are accompanied by morphological and neurochemical changes in neurons, which reverse a few hours after coming out of the torpor state. Since tau has been implicated in the structural regulation of the neuronal Golgi apparatus (GA) we have used Western Blot and immunocytochemistry to analyze whether the GA is modified in cortical neurons of the Syrian hamster at different hibernation stages. The results show that, during the hibernation cycle, the GA undergo important structural changes along with differential modifications in expression levels and distribution patterns of Golgi structural proteins. These changes were accompanied by significant transitory reductions in the volume and surface area of the GA elements during torpor and arousal stages as compared with euthermic animals.

Changes in the Golgi Apparatus of Neocortical and Hippocampal Neurons in the Hibernating Hamster

PubMed Central

Antón-Fernández, Alejandro; León-Espinosa, Gonzalo; DeFelipe, Javier; Muñoz, Alberto

2015-01-01

Hibernating animals have been used as models to study several aspects of the plastic changes that occur in the metabolism and physiology of neurons. These models are also of interest in the study of Alzheimer's disease because the microtubule-associated protein tau is hyperphosphorylated during the hibernation state known as torpor, similar to the pretangle stage of Alzheimer's disease. Hibernating animals undergo torpor periods with drops in body temperature and metabolic rate, and a virtual cessation of neural activity. These processes are accompanied by morphological and neurochemical changes in neurons, which reverse a few hours after coming out of the torpor state. Since tau has been implicated in the structural regulation of the neuronal Golgi apparatus (GA) we have used Western Blot and immunocytochemistry to analyze whether the GA is modified in cortical neurons of the Syrian hamster at different hibernation stages. The results show that, during the hibernation cycle, the GA undergo important structural changes along with differential modifications in expression levels and distribution patterns of Golgi structural proteins. These changes were accompanied by significant transitory reductions in the volume and surface area of the GA elements during torpor and arousal stages as compared with euthermic animals. PMID:26696838

Molecular mechanisms of epigenetic variation in plants.

PubMed

Fujimoto, Ryo; Sasaki, Taku; Ishikawa, Ryo; Osabe, Kenji; Kawanabe, Takahiro; Dennis, Elizabeth S

2012-01-01

Natural variation is defined as the phenotypic variation caused by spontaneous mutations. In general, mutations are associated with changes of nucleotide sequence, and many mutations in genes that can cause changes in plant development have been identified. Epigenetic change, which does not involve alteration to the nucleotide sequence, can also cause changes in gene activity by changing the structure of chromatin through DNA methylation or histone modifications. Now there is evidence based on induced or spontaneous mutants that epigenetic changes can cause altering plant phenotypes. Epigenetic changes have occurred frequently in plants, and some are heritable or metastable causing variation in epigenetic status within or between species. Therefore, heritable epigenetic variation as well as genetic variation has the potential to drive natural variation.

FAST TRACK COMMUNICATION Spectral signatures of the surface reconstructions of Au(110)/electrolyte interfaces

NASA Astrophysics Data System (ADS)

Smith, C. I.; Bowfield, A.; Almond, N. J.; Mansley, C. P.; Convery, J. H.; Weightman, P.

2010-10-01

It is demonstrated that the (1 × 1) structure and the (1 × 2) and (1 × 3) surface reconstructions that occur at Au(110)/electrolyte interfaces have unique optical fingerprints. The optical fingerprints are potential, pH and anion dependent and have potential for use in monitoring dynamic changes at this interface. We also observe a specific reflection anisotropy spectroscopy signature that may arise from anions adsorbed on the (1 × 1) structure of Au(110).

Effect of mechanical alloying and heat treatment on the behavior of fe - 28% al - 5% cr powder with nanocrystalline structure

NASA Astrophysics Data System (ADS)

Tang, W. M.; Liu, H. L.; Wang, Y. X.; Xu, G. O.; Zheng, Z. X.

2012-05-01

Nanocrystalline powders of alloy Fe - 28% Al - 5% Cr (at.%) obtained by mechanical alloying from powdered iron, aluminum, and preliminarily alloyed Fe - 20% Cr are studied. The chemical composition is shown to be homogenized. The changes in the structure and in the morphology of the particles in the process of ball milling and subsequent heat treatment are determined. The alloying is shown to occur by the mechanism of continuous diffusion mixing.

Stress Memory and the Inevitable Effects of Drought: A Physiological Perspective

PubMed Central

Fleta-Soriano, Eva; Munné-Bosch, Sergi

2016-01-01

Plants grow and develop by adjusting their physiology to changes in their environment. Changes in the abiotic environment occur over years, seasons, and days, but also over minutes and even seconds. In this ever-changing environment, plants may adjust their structure and function rapidly to optimize growth and reproduction. Plant responses to reiterated drought (i.e., repeated cycles of drought) differ from those to single incidences of drought; in fact, in nature, plants are usually exposed to repeated cycles of drought that differ in duration and intensity. Nowadays, there is increased interest in better understanding mechanisms of plant response to reiterated drought due, at least in part, to the discovery of epigenomic changes that trigger drought stress memory in plants. Beyond epigenomic changes, there are, however, other aspects that should be considered in the study of plant responses to reiterated drought: from changes in other “omics” approaches (transcriptomics, proteomics, and metabolomics), to changes in plant structure; all of which may help us to better understand plant stress memory and its underlying mechanisms. Here, we present an example in which reiterated drought affects the pigment composition of leaves in the ornamental plant Silene dioica and discuss the importance of structural changes (in this case in the photosynthetic apparatus) for the plant response to reiterated drought; they represent a stress imprint that can affect plant response to subsequent stress episodes. Emphasis is placed on the importance of considering structural changes, in addition to physiological adjustments at the “omics” level, to understand stress memory in plants better. PMID:26913046

Thermal modeling using enthalpy methods to aid in the study of microstructural changes of multilayered phase change optical memories

NASA Astrophysics Data System (ADS)

Nagpal, Swati; Aurora, Aradhna

1999-11-01

In DOW type of phase change optical memories the focus has been mainly on gestate based systems due to their good overwriting capability and very high order cyclability. To avoid the material deterioration problems such as material flow, high melting point, high viscosity or high-density components such as CrTe, (which have the same refractive index) can be added to the active layer. This has led to an improved performance of overwrite cycles from 105 to 106. Material flow occurs due to void formation. Voids and sinks are formed due to porosity of the active layer because the active layer has a density lower than that of the bulk material. One of the reasons for the formation and coalescence of voids is the way in which the film is deposited viz. Sputtering which makes Ar atoms accumulate in the films during deposition. Also the mechanical strength of the protective layer effects the repeatability of the active layer. All the above mentioned processes occur during melting and re- solidification of the nano-sized spots which are laser irradiated. Since the structure of the protective layers is very important in controlling the void formation, it is very important to study the thermal modeling of the full layer structure.

The meanings of professional life: teaching across the health professions.

PubMed

Kelley, Maureen

2002-08-01

Most of professional ethics is grounded on the assumption that we can speak meaningfully about particular, insulated professions with aims and goals, that conceptually there exists a clear "inside and outside" to any given profession. Professional ethics has also inherited the two-part assumption from mainstream moral philosophy that we can speak meaningfully about agent-relative versus agent-neutral moral perspectives, and further, that it is only from the agent-neutral perspective that we can truly evaluate our professional moral aims, rules, and practices. Several important changes that have occurred, or are currently taking place, in the structure of the health care professions, challenge those assumptions and signal the need for teachers of professional ethics to rethink the content of what we teach as well as our teaching methods. The changes include: influences and critique from other professions and from those who are served by the health professions, and influences and critique from professionals themselves, including increased activism and dissent from within the professions. The discussion focuses on changes that have occurred in the health-related fields, but insofar as similar changes are occurring in other professions such as law and business, these arguments will have broader conceptual implications for the way we ought to think about professional ethics more generally.

Molecular Dynamics Simulations of Insulin: Elucidating the Conformational Changes that Enable Its Binding.

PubMed

Papaioannou, Anastasios; Kuyucak, Serdar; Kuncic, Zdenka

2015-01-01

A sequence of complex conformational changes is required for insulin to bind to the insulin receptor. Recent experimental evidence points to the B chain C-terminal (BC-CT) as the location of these changes in insulin. Here, we present molecular dynamics simulations of insulin that reveal new insights into the structural changes occurring in the BC-CT. We find three key results: 1) The opening of the BC-CT is inherently stochastic and progresses through an open and then a "wide-open" conformation--the wide-open conformation is essential for receptor binding, but occurs only rarely. 2) The BC-CT opens with a zipper-like mechanism, with a hinge at the Phe24 residue, and is maintained in the dominant closed/inactive state by hydrophobic interactions of the neighboring Tyr26, the critical residue where opening of the BC-CT (activation of insulin) is initiated. 3) The mutation Y26N is a potential candidate as a therapeutic insulin analogue. Overall, our results suggest that the binding of insulin to its receptor is a highly dynamic and stochastic process, where initial docking occurs in an open conformation and full binding is facilitated through interactions of insulin receptor residues with insulin in its wide-open conformation.

Shifts in deep-sea community structure linked to climate and food supply.

PubMed

Ruhl, Henry A; Smith, Kenneth L

2004-07-23

A major change in the community structure of the dominant epibenthic megafauna was observed at 4100 meters depth in the northeast Pacific and was synchronous to a major El Niño/La Niña event that occurred between 1997 and 1999. Photographic abundance estimates of epibenthic megafauna from 1989 to 2002 show that two taxa decreased in abundance after 1998 by 2 to 3 orders of magnitude, whereas several other species increased in abundance by 1 to 2 orders of magnitude. These faunal changes are correlated to climate fluctuations dominated by El Niño/La Niña. Megafauna even in remote marine areas appear to be affected by contemporary climatic fluctuations. Such faunal changes highlight the importance of an adequate temporal perspective in describing biodiversity, ecology, and anthropogenic impacts in deep-sea communities.

[Structural changes in the soleus muscle of rats on the Kosmos-series biosatellites and in hypokinesia].

PubMed

Il'ina-Kakueva, E I; Portugalov, V V

1981-01-01

Structural changes in the soleus muscle of rats used in flight and synchronous experiments of the Cosmos program and hypokinetic studies have been investigated. It is hypothesized that focal edema and dystrophic changes observed in flight, synchronous and hypokinetic rats can be caused by circulation disorders of different etiology. In flight and synchronous rats they develop two days postflight due to the deconditioning of the muscle tissue and intraorgan vascular system which fail to meet the requirements after transition from 0 g to 1 g. In hypokinetic rats circulation disorders occur on the first experimental day due to mechanical causes (paws are pressed against the cage floor impeding venous outflow) and muscle pump deficiency. In all cases circulation disorders seem to be associated with peculiar features of angioarchitectonics of the soleus muscle.

GTKDynamo: a PyMOL plug-in for QC/MM hybrid potential simulations

PubMed Central

Bachega, José Fernando R.; Timmers, Luís Fernando S.M.; Assirati, Lucas; Bachega, Leonardo R.; Field, Martin J.; Wymore, Troy

2014-01-01

Hybrid quantum chemical (QC)/molecular mechanical (MM) potentials are very powerful tools for molecular simulation. They are especially useful for studying processes in condensed phase systems, such as chemical reactions, that involve a relatively localized change in electronic structure and where the surrounding environment contributes to these changes but can be represented with more computationally efficient functional forms. Despite their utility, however, these potentials are not always straightforward to apply since the extent of significant electronic structure changes occurring in the condensed phase process may not be intuitively obvious. To facilitate their use we have developed an open-source graphical plug-in, GTKDynamo, that links the PyMOL visualization program and the pDynamo QC/MM simulation library. This article describes the implementation of GTKDynamo and its capabilities and illustrates its application to QC/MM simulations. PMID:24137667

Magnetic reconnection in terms of catastrophe theory

NASA Astrophysics Data System (ADS)

Echkina, E. Y.; Inovenkov, I. N.; Nefedov, V. V.

2017-12-01

Magnetic field line reconnection (magnetic reconnection) is a phenomenon that occurs in space and laboratory plasma. Magnetic reconnection allows both the change the magnetic topology and the conversion of the magnetic energy into energy of fast particles. The critical point (critical line or plane in higher dimensional cases) of the magnetic field play an important role in process of magnetic reconnection, as in its neighborhood occurs a change of its topology of a magnetic field and redistribution of magnetic field energy. A lot of literature is devoted to the analytical and numerical investigation of the reconnection process. The main result of these investigations as the result of magnetic reconnection the current sheet is formed and the magnetic topology is changed. While the studies of magnetic reconnection in 2D and 3D configurations have a led to several important results, many questions remain open, including the behavior of a magnetic field in the neighborhood of a critical point of high order. The magnetic reconnection problem is closely related to the problem of the structural stability of vector fields. Since the magnetic field topology changes during both spontaneous and induced magnetic reconnection, it is natural to expect that the magnetic field should evolve from a structurally unstable into a structurally stable configuration. Note that, in this case, the phenomenon under analysis is more complicated since, during magnetic reconnection in a highly conducting plasma, we deal with the non-linear interaction between two vector fields: the magnetic field and the field of the plasma velocities. The aim of our article is to consider the process of magnetic reconnection and transformation of the magnetic topology from the viewpoint of catastrophe theory. Bifurcations in similar configurations (2D magnetic configuration with null high order point) with varying parameters were thoroughly discussed in a monograph by Poston and Stewart.

[The morphometric characteristics of the main structural components of renal nephrons in the white rats with experimentally induced acute and chronic alcohol intoxication].

PubMed

Shcherbakova, V M

2016-01-01

The objective of the present work was to study the morphometric characteristics of the main structural components of renal nephrons in the white rats with the experimentally induced acute and chronic alcohol intoxication. We undertook the morphometric examination of the structural elements of rat kidneys with the subsequent statistical analysis of the data obtained. The results of the study give evidence of the toxic action of ethanol on all structural components of the nephron in the case of both acute and chronic alcohol intoxication. The study revealed some specific features of the development of pathological process in the renal tissue structures at different stages of alcohol intoxication. The most pronounced morphological changes were observed in the renal proximal tubules and the least pronounced ones in the structure of the renal glomeruli. The earliest morphological changes become apparent in distal convoluted tubules of the nephron; in the case of persistent alcoholemia, they first develop in the renal corpuscles and thereafter in the distal proximal tubules. The maximum changes occur in the case of acute alcohol intoxication and between 2 weeks and 2 months of chronic intoxication; they become less conspicuous during a later period.

Structural characterization of metal binding to a cold-adapted frataxin.

PubMed

Noguera, Martín E; Roman, Ernesto A; Rigal, Juan B; Cousido-Siah, Alexandra; Mitschler, André; Podjarny, Alberto; Santos, Javier

2015-06-01

Frataxin is an evolutionary conserved protein that participates in iron metabolism. Deficiency of this small protein in humans causes a severe neurodegenerative disease known as Friedreich's ataxia. A number of studies indicate that frataxin binds iron and regulates Fe-S cluster biosynthesis. Previous structural studies showed that metal binding occurs mainly in a region of high density of negative charge. However, a comprehensive characterization of the binding sites is required to gain further insights into the mechanistic details of frataxin function. In this work, we have solved the X-ray crystal structures of a cold-adapted frataxin from a psychrophilic bacterium in the presence of cobalt or europium ions. We have identified a number of metal-binding sites, mainly solvent exposed, several of which had not been observed in previous studies on mesophilic homologues. No major structural changes were detected upon metal binding, although the structures exhibit significant changes in crystallographic B-factors. The analysis of these B-factors, in combination with crystal packing and RMSD among structures, suggests the existence of localized changes in the internal motions. Based on these results, we propose that bacterial frataxins possess binding sites of moderate affinity for a quick capture and transfer of iron to other proteins and for the regulation of Fe-S cluster biosynthesis, modulating interactions with partner proteins.

[Bell's palsy in malopolska's children in 2010-2014 years].

PubMed

Rogalska, Emilia; Skowronek-Bała, Barbara; Świerczyńska, Anna; Kaciński, Marek

2016-01-01

Peripheral facial nerve palsy (Bell' palsy, BP) is a not rare diseases in children, being the most common acquired mononeuropathy. The authors of this study wanted to determine whether the occurrence and course of paralysis changed in the past 5 years (2010-2014). The study involved Lesser Poland region, where the majority of children with paralysis are hospitalized at the Pediatric Neurology Department of University Children's Hospital in Krakow. These children in subsequent years were admitted to our department without any limitations. A review of clinical documentation of 125 patients, in terms of demographics, the coexistence of other diseases, seasonality, the degree of paralysis, location of paralysis, the prevalence of the recurrence was made. Changes in the structure of the nerve VII in MRI and CT, pharmacological treatment, applied rehabilitation, the degree of improvement and time of hospitalization were analyzed. Similar distribution of occurrence and gender of children with BP in Lesser Poland region within 5 years were observed. The predominance of the girls resulted from demographic composition of the population. BP occurred most frequently in summer and winter. In more than half of children BP occurred in the course of acute systemic infection or craniofacial infection and in 5/125 BP followed head injury. Children with infections required antibiotic therapy. Left-sided paralysis was found in the majority of children and almost half of patients needed protection of the cornea of the eye (significant degree). In 12% of children structural changes within the facial nerve were found. In these children antiviral treatment was used and hospitalization time was more than 20 days while in the majority of children hospitalization lasted 15 days. In 8 (6.4%) children with recurrent BP kinezytherapy, electrical stimulation and laser therapy were applied. Steroid therapy was not used. Only 7/125 chil. dren had mild impairment of the eye closing at the discharge and the others received nearly complete recovery. Inflammatory etiology is the most common in children with BP. BP occurs more often in the summer and winter. Severity of paralysis was significant in more than half of hospitalized children. Children with structural changes within the nerve VII required longer hospitalization and comprehensive treatment.

Shelter for the twenty-first century.

PubMed Central

Spengler, J D

1990-01-01

Housing for the twenty-first century will be shaped by the changes that are occurring in society. These include the demographics of the occupant, the products and materials used for construction and furnishing, and the basic use of the structure. An aging population will have different demands on design and function. The health concerns of an aging population encompass chronic degenerative diseases as well as injury. The lessons of the past must make us mindful that chronic, low-level exposures to substances can occur at home. Products and materials used in homes can release vapors that may affect immunologic and neurologic function. Manifestations of dysfunctions will be more important as our population ages and if there is a continued reliance on new chemical formulation for products used in homes and workplaces. The future portends changes in functional use of residences. Electronic communications and robotics will decentralize our work force. Manufacturing or office functions will occur at home. This will present new challenges for health and safety for both monitoring and prevention. PMID:2401266

Effects of CO[sub 2] and climate change on forest trees: Soil biology and enzymology

DOE Office of Scientific and Technical Information (OSTI.GOV)

Moldenke, A.R.; Baumeister, N.; Caldwell, B.A.

1994-06-01

Samples of Teracosm soils were analyzed shortly after initial setup to determine whether initial conditions were equivalent and matched expected values for local soils. Total and active fungal biomass, active bacterial biomass and protozoan numbers were reduced, with greatest decreases occurring in the A horizon. No effect was observed on total bacterial biomass, nematode or anthropod densities, but changes in nematode and arthropod species composition occurred. Significant differences in total density and species composition occurred between the enclosed Teracosms and the open controls. Arthropod and nematode community structure in the three altitudinal field sites had significantly diverged. No significant differencesmore » in activities of key soil enzymes in C- and N-cycling (acid phosphatase, protease, B-glucosidase, phenol oxidase and peroxidase) were found between initial samples relative to treatment, but all levels were significantly difference relative to depth in soil profile. Activities were within ranges previously observed in forests of the Pacific Northwest.« less

Goals and intentions mediate efficacy beliefs and declining physical activity in high school girls.

PubMed

Dishman, Rod K; Saunders, Ruth P; Felton, Gwen; Ward, Dianne S; Dowda, Marsha; Pate, Russ R

2006-12-01

According to theory, girls who set goals about increasing their physical activity and who are dissatisfied with their current activity level are likely to form intentions to be active and to carry out those intentions, especially if they have high efficacy and control beliefs about being physically active. We tested those ideas while observing naturally occurring change during high school. A cohort of 431 black and white girls was tested at the end of their 9th- and 12th-grade academic years. Confirmatory factor analysis established the structural invariance of the measures across the 3-year study period. Structural equation modeling and panel analysis were used to determine whether changes in goal setting and satisfaction would mediate relations of self-efficacy and perceived behavioral control with changes in intention and physical activity. Testing occurred between February and May in 1999 and 2004. Data were analyzed in 2006. Goal setting and intention mediated the indirect relation between self-efficacy and change in physical activity. Perceived behavioral control and physical activity change were related directly and also indirectly by a path mediated through satisfaction and intention. Black girls had lower self-efficacy, but changes in other variables were unrelated to race. These observations of longitudinal relations elaborate application of self-efficacy theory and the theory of planned behavior to physical activity by showing that goal setting and satisfaction mediate the relations of self-efficacy and perceived behavioral control with changes in intention and physical activity. The results encourage additional research to identify the sources and development of physical activity goals, and their attainment, among girls, and whether experimental manipulation of goals and intentions can mitigate the decline in girls' physical activity during high school.

Behavior change communication strategies.

PubMed

Aggleton, P

1997-04-01

Appropriate and effective communication is central to the success of interventions to reduce the risk of HIV infection. This paper reviews what has been learned about the nature of communication in the behavior change process. It examines the contexts in which communication occurs, as well as the contribution of communication theory, social marketing theory, and structural intervention theory to intervention development. Guidance is offered on the most appropriate ways in which to communicate with different groups and audiences, and future priorities for research and intervention are identified.

Heat loading of hoist brakes by example of drum brakes

NASA Astrophysics Data System (ADS)

Vöth, S.; Vasilyeva, M. A.

2017-10-01

Due to the technological development in drive technology, drives controlled by frequency inverters in hoists of cranes are almost standard. Since these drives offer the possibility of electric braking, the operation of the mechanical brakes changes as a result. As a result, the mechanical brakes are used more rarely and, if so, more likely in critical operating conditions. In this paper, an analysis of the changes that occur in the structure under the influence of thermal load is presented.

Effect of elastic strain redistribution on electronic band structures of compressively strained GaInAsP/InP membrane quantum wires

NASA Astrophysics Data System (ADS)

Ferdous, F.; Haque, A.

2007-05-01

The effect of redistribution of elastic strain relaxation on the energy band structures of GaInAsP/InP compressively strained membrane quantum wires fabricated by electron-beam lithography, reactive-ion etching and two-step epitaxial growth is theoretically studied using an 8-band k ṡp method. Anisotropic strain analysis by the finite element method shows that due to etching away the top and the bottom InP clad layers in membrane structures, redistribution of strain occurs. It is found that strain redistribution increases the effective bandgap of membrane quantum wire structures causing a blueshift of the emission frequency. Comparison with effective bandgap calculations neglecting confinement and band mixing demonstrates that neglect of these effects leads to an overestimation of the change in the bandgap. We have also investigated the effect of variation of wire width, barrier strain compensation, number of stacked quantum wire layers, and thickness of the top and the bottom residual InP layers in membrane structures on the change in the effective bandgap of membrane structures.

An In-Situ XAS Study of the Structural Changes in a CuO-CeO2/Al2O3 Catalyst during Total Oxidation of Propane

DOE Office of Scientific and Technical Information (OSTI.GOV)

Silversmith, Geert; Poelman, Hilde; Poelman, Dirk

2007-02-02

A CuOx-CeOx/Al2O3 catalyst was studied with in-situ transmission Cu K XAS for the total oxidation of propane as model reaction for the catalytic elimination of volatile organic compounds. The local Cu structure was determined for the catalyst as such, after pre-oxidation and after reduction with propane. The catalyst as such has a local CuO structure. No structural effect was observed upon heating in He up to 600 deg. C or after pre-oxidation at 150 deg. C. A full reduction of the Cu2+ towards metallic Cu0 occurred, when propane was fed to the catalyst. The change in local Cu structure duringmore » propane reduction was followed with a time resolution of 1 min. The {chi}(k) scans appeared as linear combinations of start and end spectra, CuO and Cu structure, respectively. However, careful examination of the XANES edge spectra indicates the presence of a small amount of additional Cu1+ species.« less

Climate change alters stability and species potential interactions in a large marine ecosystem.

PubMed

Griffith, Gary P; Strutton, Peter G; Semmens, Jayson M

2018-01-01

We have little empirical evidence of how large-scale overlaps between large numbers of marine species may have altered in response to human impacts. Here, we synthesized all available distribution data (>1 million records) since 1992 for 61 species of the East Australian marine ecosystem, a global hot spot of ocean warming and continuing fisheries exploitation. Using a novel approach, we constructed networks of the annual changes in geographical overlaps between species. Using indices of changes in species overlap, we quantified changes in the ecosystem stability, species robustness, species sensitivity and structural keystone species. We then compared the species overlap indices with environmental and fisheries data to identify potential factors leading to the changes in distributional overlaps between species. We found that the structure of the ecosystem has changed with a decrease in asymmetrical geographical overlaps between species. This suggests that the ecosystem has become less stable and potentially more susceptible to environmental perturbations. Most species have shown a decrease in overlaps with other species. The greatest decrease in species overlap robustness and sensitivity to the loss of other species has occurred in the pelagic community. Some demersal species have become more robust and less sensitive. Pelagic structural keystone species, predominately the tunas and billfish, have been replaced by demersal fish species. The changes in species overlap were strongly correlated with regional oceanographic changes, in particular increasing ocean warming and the southward transport of warmer and saltier water with the East Australian Current, but less correlated with fisheries catch. Our study illustrates how large-scale multispecies distribution changes can help identify structural changes in marine ecosystems associated with climate change. © 2017 John Wiley & Sons Ltd.

Age-related changes in the plasticity and toughness of human cortical bone at multiple length-scales

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zimmermann, Elizabeth A.; Schaible, Eric; Bale, Hrishikesh

2011-08-10

The structure of human cortical bone evolves over multiple length-scales from its basic constituents of collagen and hydroxyapatite at the nanoscale to osteonal structures at nearmillimeter dimensions, which all provide the basis for its mechanical properties. To resist fracture, bone’s toughness is derived intrinsically through plasticity (e.g., fibrillar sliding) at structural-scales typically below a micron and extrinsically (i.e., during crack growth) through mechanisms (e.g., crack deflection/bridging) generated at larger structural-scales. Biological factors such as aging lead to a markedly increased fracture risk, which is often associated with an age-related loss in bone mass (bone quantity). However, we find that age-relatedmore » structural changes can significantly degrade the fracture resistance (bone quality) over multiple lengthscales. Using in situ small-/wide-angle x-ray scattering/diffraction to characterize sub-micron structural changes and synchrotron x-ray computed tomography and in situ fracture-toughness measurements in the scanning electron microscope to characterize effects at micron-scales, we show how these age-related structural changes at differing size-scales degrade both the intrinsic and extrinsic toughness of bone. Specifically, we attribute the loss in toughness to increased non-enzymatic collagen cross-linking which suppresses plasticity at nanoscale dimensions and to an increased osteonal density which limits the potency of crack-bridging mechanisms at micron-scales. The link between these processes is that the increased stiffness of the cross-linked collagen requires energy to be absorbed by “plastic” deformation at higher structural levels, which occurs by the process of microcracking.« less

Magnetically tunable control of light reflection in an unusual optical protein of squid

NASA Astrophysics Data System (ADS)

Iwasaka, M.; Tagawa, K.; Kikuchi, Y.

2017-05-01

In this study, we focused on the magnetically tunable changes in the reflectivity of the protein reflectin, which is generated by squid and used to control their body surface color for camouflage in seawater. A cellular organelle called an iridosome was separated from the skin of the dorsal part of a squid (cuttlefish; Sepia esculenta), and the light reflection dynamics of iridosomes containing reflectin were measured with and without exposure to a magnetic field of 500 mT. The magnetic field induced both steady and transient increases of reflection by the iridosomes, suggesting that a reversible conformational change occurred inside the iridosomes when the magnetic field was switched on and off. The intensity of light scattering perpendicular to the direction of the magnetic field increased when the magnetic field was applied. This kind of behavior (Type I) occurred in the majority (60%) of the measured samples. Another kind of reflection change (Type II) was a transient increase in light reflection. It is speculated that the wave-shaped structure of the lipid membrane connected to reflectin proteins changed to enhance the light reflection of reflectin by altering the diamagnetic orientation of the lipid layer in the bent part of the membrane under the applied magnetic field. Overall, our results suggest that the mesoscale lipid layers changed their alignment diamagnetically and the length between iridescent layers was modified by the magnetic field, even though no obvious change in alignment occurred at the microscale.

Education and Training at SNL: Past and Present

DOE Office of Scientific and Technical Information (OSTI.GOV)

BOMBER, THOMAS M.; DREWIEN, CELESTE A.

2002-11-01

The purpose of this review was to provide insights and information to Sandia National Laboratories' (SNL) Education Council on the state of technical education and training at SNL in order to address the concern that a change in philosophy surrounding education had occurred. To accomplish this, the status of current and past technical training and education programs were compared, and significant changes at SNL were assessed for their impact on education and training. Major changes in education and training are in the advertisement of course offerings, the course delivery methods, and the funding mechanisms for student and instructor time asmore » well as course costs. The significant changes in SNL which influenced technical training and education are the considerable increase in mandatory or compliance training, a fundamental shift in SNL's management structure from an institutional structure to a more business-like, project-budgeted structure, and the change in SNL's mission at the end of the Cold War. These changes contributed to less time for technical training, reduction of training funds, elimination of some training, and a Service Center approach to paying for training. Most importantly, the overall combined effect has resulted in a shift from a strategic to a tactical training approach. The Corporate Training Department (CTD) has maneuvered to accommodate these changes and keep abreast of constantly changing needs.« less

Drivers of protogynous sex change differ across spatial scales.

PubMed

Taylor, Brett M

2014-01-22

The influence of social demography on sex change schedules in protogynous reef fishes is well established, yet effects across spatial scales (in particular, the magnitude of natural variation relative to size-selective fishing effects) are poorly understood. Here, I examine variation in timing of sex change for exploited parrotfishes across a range of environmental, anthropogenic and geographical factors. Results were highly dependent on spatial scale. Fishing pressure was the most influential factor determining length at sex change at the within-island scale where a wide range of anthropogenic pressure existed. Sex transition occurred at smaller sizes where fishing pressure was high. Among islands, however, differences were overwhelmingly predicted by reefal-scale structural features, a pattern evident for all species examined. For the most abundant species, Chlorurus spilurus, length at sex change increased at higher overall densities and greater female-to-male sex ratios at all islands except where targeted by fishermen; here the trend was reversed. This implies differing selective pressures on adult individuals can significantly alter sex change dynamics, highlighting the importance of social structure, demography and the selective forces structuring populations. Considerable life-history responses to exploitation were observed, but results suggest potential fishing effects on demography may be obscured by natural variation at biogeographic scales.

Pressure and Temperature Effects on the Activity and Structure of the Catalytic Domain of Human MT1-MMP

PubMed Central

Decaneto, Elena; Suladze, Saba; Rosin, Christopher; Havenith, Martina; Lubitz, Wolfgang; Winter, Roland

2015-01-01

Membrane type 1-matrix metalloproteinase (MT1-MMP or MMP-14) is a zinc-transmembrane metalloprotease involved in the degradation of extracellular matrix and tumor invasion. While changes in solvation of MT1-MMP have been recently studied, little is known about the structural and energetic changes associated with MT1-MMP while interacting with substrates. Steady-state kinetic and thermodynamic data (including activation energies and activation volumes) were measured over a wide range of temperatures and pressures by means of a stopped-flow fluorescence technique. Complementary temperature- and pressure-dependent Fourier-transform infrared measurements provided corresponding structural information of the protein. MT1-MMP is stable and active over a wide range of temperatures (10–55°C). A small conformational change was detected at 37°C, which is responsible for the change in activity observed at the same temperature. Pressure decreases the enzymatic activity until complete inactivation occurs at 2 kbar. The inactivation is associated with changes in the rate-limiting step of the reaction caused by additional hydration of the active site upon compression and/or minor conformational changes in the active site region. Based on these data, an energy and volume diagram could be established for the various steps of the enzymatic reaction. PMID:26636948

Effects of Short-Term Warming and Altered Precipitation on Soil Microbial Communities in Alpine Grassland of the Tibetan Plateau

PubMed Central

Zhang, Kaoping; Shi, Yu; Jing, Xin; He, Jin-Sheng; Sun, Ruibo; Yang, Yunfeng; Shade, Ashley; Chu, Haiyan

2016-01-01

Soil microbial communities are influenced by climate change drivers such as warming and altered precipitation. These changes create abiotic stresses, including desiccation and nutrient limitation, which act on microbes. However, our understanding of the responses of microbial communities to co-occurring climate change drivers is limited. We surveyed soil bacterial and fungal diversity and composition after a 1-year warming and altered precipitation manipulation in the Tibetan plateau alpine grassland. In isolation, warming and decreased precipitation treatments each had no significant effects on soil bacterial community structure; however, in combination of both treatments altered bacterial community structure (p = 0.03). The main effect of altered precipitation specifically impacted the relative abundances of Bacteroidetes and Gammaproteobacteria compared to the control, while the main effect of warming impacted the relative abundance of Betaproteobacteria. In contrast, the fungal community had no significant response to the treatments after 1-year. Using structural equation modeling (SEM), we found bacterial community composition was positively related to soil moisture. Our results indicate that short-term climate change could cause changes in soil bacterial community through taxonomic shifts. Our work provides new insights into immediate soil microbial responses to short-term stressors acting on an ecosystem that is particularly sensitive to global climate change. PMID:27446064

Effects of Short-Term Warming and Altered Precipitation on Soil Microbial Communities in Alpine Grassland of the Tibetan Plateau.

PubMed

Zhang, Kaoping; Shi, Yu; Jing, Xin; He, Jin-Sheng; Sun, Ruibo; Yang, Yunfeng; Shade, Ashley; Chu, Haiyan

2016-01-01

Soil microbial communities are influenced by climate change drivers such as warming and altered precipitation. These changes create abiotic stresses, including desiccation and nutrient limitation, which act on microbes. However, our understanding of the responses of microbial communities to co-occurring climate change drivers is limited. We surveyed soil bacterial and fungal diversity and composition after a 1-year warming and altered precipitation manipulation in the Tibetan plateau alpine grassland. In isolation, warming and decreased precipitation treatments each had no significant effects on soil bacterial community structure; however, in combination of both treatments altered bacterial community structure (p = 0.03). The main effect of altered precipitation specifically impacted the relative abundances of Bacteroidetes and Gammaproteobacteria compared to the control, while the main effect of warming impacted the relative abundance of Betaproteobacteria. In contrast, the fungal community had no significant response to the treatments after 1-year. Using structural equation modeling (SEM), we found bacterial community composition was positively related to soil moisture. Our results indicate that short-term climate change could cause changes in soil bacterial community through taxonomic shifts. Our work provides new insights into immediate soil microbial responses to short-term stressors acting on an ecosystem that is particularly sensitive to global climate change.

[Twenty-second conference of the Czechoslovak Demographic Society: "The Demographic Position of Czechoslovakia within Europe and the World"].

PubMed

Fialova, L; Rychtarikova, J; Roubicek, V; Stloukal, L; Veres, P; Koschin, F; Novakova, B; Pavlik, Z

1992-01-01

This is a collection of short papers presented at a conference held in Prague, Czechoslovakia, in 1991. The focus of the conference was on the demographic changes that have occurred in Czechoslovakia since World War II and their relationship to such changes in the rest of Europe and elsewhere in the world. Essay topics include fertility trends; contraceptive prevalence, including abortion rates; living standards and health care; and changes in the age structure. Some data for selected countries are included for comparison. (SUMMARY IN ENG AND RUS)

Genetic structure among greater white-fronted goose populations of the Pacific Flyway

USGS Publications Warehouse

Ely, Craig R.; Wilson, Robert E.; Talbot, Sandra L.

2017-01-01

An understanding of the genetic structure of populations in the wild is essential for long-term conservation and stewardship in the face of environmental change. Knowledge of the present-day distribution of genetic lineages (phylogeography) of a species is especially important for organisms that are exploited or utilize habitats that may be jeopardized by human intervention, including climate change. Here, we describe mitochondrial (mtDNA) and nuclear genetic (microsatellite) diversity among three populations of a migratory bird, the greater white-fronted goose (Anser albifrons), which breeds discontinuously in western and southwestern Alaska and winters in the Pacific Flyway of North America. Significant genetic structure was evident at both marker types. All three populations were differentiated for mtDNA, whereas microsatellite analysis only differentiated geese from the Cook Inlet Basin. In sexual reproducing species, nonrandom mate selection, when occurring in concert with fine-scale resource partitioning, can lead to phenotypic and genetic divergence as we observed in our study. If mate selection does not occur at the time of reproduction, which is not uncommon in long-lived organisms, then mechanisms influencing the true availability of potential mates may be obscured, and the degree of genetic and phenotypic diversity may appear incongruous with presumed patterns of gene flow. Previous investigations revealed population-specific behavioral, temporal, and spatial mechanisms that likely influence the amount of gene flow measured among greater white-fronted goose populations. The degree of observed genetic structuring aligns well with our current understanding of population differences pertaining to seasonal movements, social structure, pairing behavior, and resource partitioning.

On the Parity of Structural Persistence in Language Production and Comprehension

PubMed Central

Tooley, Kristen M.; Bock, Kathryn

2014-01-01

Structural priming creates structural persistence. That is, differences in experience with syntax can change subsequent language performance, and the changes can be observed in both language production and comprehension. However, the effects in comprehension and production appear to differ. In comprehension, persistence is typically found when the verbs are the same in primes and targets; in production, persistence occurs without verb overlap. The contrast suggests a theoretically important hypothesis: parsing in comprehension is lexically driven while formulation in production is structurally driven. A major weakness in this hypothesis about comprehension-production differences is that its empirical motivation rests on the outcomes of experiments in which the priming manipulations differ, the primed sentence structures differ, and the measures of priming differ. To sharpen the comparison, we examined structural persistence with and without verb overlap in both reading comprehension and spoken production, using the same prime presentation procedure, the same syntactic structures, the same sentences, and the same participants. These methods yielded abstract sructural persistence in comprehension as well as production. A measure of the strength of persistence revealed significant effects of priming and verb overlap without significant comprehension—production differences. This argues for uniformity in the structural mechanisms of language processing. PMID:24803423

Complex pattern of variation in neurocranial ontogeny revealed by CT-scanning.

PubMed

Anzelmo, Marisol; Ventrice, Fernando; Kelmansky, Diana; Sardi, Marina

2018-05-01

The neurocranium of hominid species has been largely studied with reference to the midsagittal plane, with variations being attributed to brain evolution. By contrast, there is limited information on variation in non-midsagittal regions, which are the points of insertion of muscles and bony structures related to mastication. This work aims to analyze ontogenetic changes and sexual dimorphism (SD) in midsagittal and non-midsagittal neurocranial structures from a contemporary human sample comprising 138 computed tomography (CT) cranial images of individuals ranging from infants to adults. Morphology of the vault and the base was assessed by registering landmarks and semilandmarks, which were analyzed by geometric morphometrics, and the endocranial volume (EV). The results of regressions and Kruskal-Wallis test indicate that the major size and shape changes in both midsagittal and non-midsagittal regions occur during infancy and juvenility; shape changes are also associated with an increase in EV. The size of the midsagittal vault, the shape of the non-midsagittal vault and the size of the base show an extension of ontogenetic trajectories. Sexes show similar changes in shape but different changes in size. We conclude that brain growth appears to be an important factor influencing the morphology of the neurocranium, at least during infancy and childhood. Subsequent changes may be attributed to osteogenic activity and the differential growth of the brain lobes. Masticatory-related bony structures and muscles may not be strong enough factors to induce independent modifications in non-midsagittal structures. The small influence of the cranial muscles would explain why the human neurocranium is a quite integrated structure.

Effects of sedimentary sulfide on community structure, population dynamics, and colonization depth of macrozoobenthos in organic-rich estuarine sediments.

PubMed

Kanaya, Gen; Uehara, Tadayasu; Kikuchi, Eisuke

2016-08-15

An annual field survey and in situ recolonization experiment revealed the effects of sedimentary sulfide (H2S) on macrozoobenthos in a eutrophic brackish lagoon. Species diversity was much lower throughout the year in muddy opportunist-dominant sulfidic areas. Mass mortality occurred during warmer months under elevated H2S levels. An enclosure experiment demonstrated that sedimentary H2S modified community composition, size structure, and colonization depth of macrozoobenthos. Species-specific responses to each sediment type (sand, sulfidic mud, and mud with H2S removed) resulted in changes in the established community structure. Dominant polychaetes (Hediste spp., Pseudopolydora spp., and Capitella teleta) occurred predominantly in a thin surface layer in the presence of H2S. On the other hand, organic-rich mud facilitated settlement of polychaete larvae if it does not contain H2S. These results demonstrate that sediment characteristics, including H2S level and organic content, were key structuring factors for the macrozoobenthic assemblage in organically polluted estuarine sediments. Copyright © 2016 Elsevier Ltd. All rights reserved.

Wind velocity-change (gust rise) criteria for wind turbine design

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cliff, W.C.; Fichtl, G.H.

1978-07-01

A closed-form equation is derived for root mean square (rms) value of velocity change (gust rise) that occurs over the swept area of wind turbine rotor systems and an equation for rms value of velocity change that occurs at a single point in space. These formulas confirm the intuitive assumption that a large system will encounter a less severe environment than a small system when both are placed at the same location. Assuming a normal probability density function for the velocity differences, an equation is given for calculating the expected number of velocity differences that will occur in 1 hrmore » and will be larger than an arbitrary value. A formula is presented that gives the expected number of velocity differences larger than an arbitrary value that will be encountered during the design life of a wind turbine. In addition, a method for calculating the largest velocity difference expected during the life of a turbine and a formula for estimating the risk of exceeding a given velocity difference during the life of the structure are given. The equations presented are based upon general atmospheric boundary-layer conditions and do not include information regarding events such as tornados, hurricanes, etc.« less

Predictions of hydrothermal alteration within near-ridge oceanic crust from coordinated geochemical and fluid flow models

USGS Publications Warehouse

Wetzel, L.R.; Raffensperger, Jeff P.; Shock, E.L.

2001-01-01

Coordinated geochemical and hydrological calculations guide our understanding of the composition, fluid flow patterns, and thermal structure of near-ridge oceanic crust. The case study presented here illustrates geochemical and thermal changes taking place as oceanic crust ages from 0.2 to 1.0 Myr. Using a finite element code, we model fluid flow and heat transport through the upper few hundred meters of an abyssal hill created at an intermediate spreading rate. We use a reaction path model with a customized database to calculate equilibrium fluid compositions and mineral assemblages of basalt and seawater at 500 bars and temperatures ranging from 150 to 400??C. In one scenario, reaction path calculations suggest that volume increases on the order of 10% may occur within portions of the basaltic basement. If this change in volume occurred, it would be sufficient to fill all primary porosity in some locations, effectively sealing off portions of the oceanic crust. Thermal profiles resulting from fluid flow simulations indicate that volume changes along this possible reaction path occur primarily within the first 0.4 Myr of crustal aging. ?? 2001 Elsevier Science B.V. All rights reserved.

Effects of space shuttle launches STS-1 through STS-9 on terrestrial vegetation of John F. Kennedy Space Center, Florida

NASA Technical Reports Server (NTRS)

Schmalzer, P. A.; Hinkle, C. R.; Breininger, D.; Knott, W. M., III (Editor); Koller, A. M., Jr. (Editor)

1985-01-01

Space Shuttle launches produce a cloud containing hydrochloric acid (HCl), aluminum oxide (Al203), and other substances. Acidities of less than 0.5 pH have been measured routinely in association with the launch cloud. In an area of about 22 ha regularly exposed to the exhaust cloud during most Shuttle launches, acute vegetation damage has resulted from the first nine Shuttle launches. Changes include loss of sensitive species, loss of plant community structure, reduction in total cover, and replacement of some species by weedy invaders. Community level changes define a retrogressive sequence. One-time impacts to strand and dune vegetation occurred after launches of STS-8 and STS-9. Acute vegetation damage occurred especially to sensitive species. Within six months, however, recovery was nearly complete. Sensitivity of species to the launch cloud was partially predicted by previous laboratory studies. Far-field acidic and dry fallout from the cloud as it rises to stabilization and moves with the prevailing winds causes vegetation spotting. Damage from this deposition is minor; typically at most 1% to 5% of leaf surface area is affected. No plant mortality or community changes have occurred from far-field deposition.

The characteristics of gas hydrates occurring in natural environment

NASA Astrophysics Data System (ADS)

Lu, H.; Moudrakovski, I.; Udachin, K.; Enright, G.; Ratcliffe, C.; Ripmeester, J.

2009-12-01

In the past few years, extensive analyses have been carried out for characterizing the natural gas hydrate samples from Cascadia, offshore Vancouver Island; Mallik, Mackenzie Delta; Mount Elbert, Alaska North Slope; Nankai Trough, offshore Japan; Japan Sea and offshore India. With the results obtained, it is possible to give a general picture of the characteristics of gas hydrates occurring in natural environment. Gas hydrate can occur in sediments of various types, from sands to clay, although it is preferentially enriched in sediments of certain types, for example coarse sands and fine volcanic ash. Most of the gas hydrates in sediments are invisible, occurring in the pores of the sediments, while some hydrates are visible, appearing as massive, nodular, planar, vein-like forms and occurring around the seafloor, in the fractures related to fault systems, or any other large spaces available in sediments. Although methane is the main component of most of the natural gas hydrates, C2 to C7 hydrocarbons have been recognized in hydrates, sometimes even in significant amounts. Shallow marine gas hydrates have been found generally to contain minor amounts of hydrogen sulfide. Gas hydrate samples with complex gas compositions have been found to have heterogeneous distributions in composition, which might reflect changes in the composition of the available gas in the surrounding environment. Depending on the gas compositions, the structure type of a natural gas hydrate can be structure I, II or H. For structure I methane hydrate, the large cages are almost fully occupied by methane molecules, while the small cages are only partly occupied. Methane hydrates occurring in different environments have been identified with almost the same crystallographic parameters.

Developmental Changes in Organization of Structural Brain Networks

PubMed Central

Khundrakpam, Budhachandra S.; Reid, Andrew; Brauer, Jens; Carbonell, Felix; Lewis, John; Ameis, Stephanie; Karama, Sherif; Lee, Junki; Chen, Zhang; Das, Samir; Evans, Alan C.; Ball, William S.; Byars, Anna Weber; Schapiro, Mark; Bommer, Wendy; Carr, April; German, April; Dunn, Scott; Rivkin, Michael J.; Waber, Deborah; Mulkern, Robert; Vajapeyam, Sridhar; Chiverton, Abigail; Davis, Peter; Koo, Julie; Marmor, Jacki; Mrakotsky, Christine; Robertson, Richard; McAnulty, Gloria; Brandt, Michael E.; Fletcher, Jack M.; Kramer, Larry A.; Yang, Grace; McCormack, Cara; Hebert, Kathleen M.; Volero, Hilda; Botteron, Kelly; McKinstry, Robert C.; Warren, William; Nishino, Tomoyuki; Robert Almli, C.; Todd, Richard; Constantino, John; McCracken, James T.; Levitt, Jennifer; Alger, Jeffrey; O'Neil, Joseph; Toga, Arthur; Asarnow, Robert; Fadale, David; Heinichen, Laura; Ireland, Cedric; Wang, Dah-Jyuu; Moss, Edward; Zimmerman, Robert A.; Bintliff, Brooke; Bradford, Ruth; Newman, Janice; Evans, Alan C.; Arnaoutelis, Rozalia; Bruce Pike, G.; Louis Collins, D.; Leonard, Gabriel; Paus, Tomas; Zijdenbos, Alex; Das, Samir; Fonov, Vladimir; Fu, Luke; Harlap, Jonathan; Leppert, Ilana; Milovan, Denise; Vins, Dario; Zeffiro, Thomas; Van Meter, John; Lange, Nicholas; Froimowitz, Michael P.; Botteron, Kelly; Robert Almli, C.; Rainey, Cheryl; Henderson, Stan; Nishino, Tomoyuki; Warren, William; Edwards, Jennifer L.; Dubois, Diane; Smith, Karla; Singer, Tish; Wilber, Aaron A.; Pierpaoli, Carlo; Basser, Peter J.; Chang, Lin-Ching; Koay, Chen Guan; Walker, Lindsay; Freund, Lisa; Rumsey, Judith; Baskir, Lauren; Stanford, Laurence; Sirocco, Karen; Gwinn-Hardy, Katrina; Spinella, Giovanna; McCracken, James T.; Alger, Jeffry R.; Levitt, Jennifer; O'Neill, Joseph

2013-01-01

Recent findings from developmental neuroimaging studies suggest that the enhancement of cognitive processes during development may be the result of a fine-tuning of the structural and functional organization of brain with maturation. However, the details regarding the developmental trajectory of large-scale structural brain networks are not yet understood. Here, we used graph theory to examine developmental changes in the organization of structural brain networks in 203 normally growing children and adolescents. Structural brain networks were constructed using interregional correlations in cortical thickness for 4 age groups (early childhood: 4.8–8.4 year; late childhood: 8.5–11.3 year; early adolescence: 11.4–14.7 year; late adolescence: 14.8–18.3 year). Late childhood showed prominent changes in topological properties, specifically a significant reduction in local efficiency, modularity, and increased global efficiency, suggesting a shift of topological organization toward a more random configuration. An increase in number and span of distribution of connector hubs was found in this age group. Finally, inter-regional connectivity analysis and graph-theoretic measures indicated early maturation of primary sensorimotor regions and protracted development of higher order association and paralimbic regions. Our finding reveals a time window of plasticity occurring during late childhood which may accommodate crucial changes during puberty and the new developmental tasks that an adolescent faces. PMID:22784607

Effects of climate change on ecological disturbance in the northern Rockies

USGS Publications Warehouse

Loehman, Rachel A.; Bentz, Barbara J.; DeNitto, Gregg A.; Keane, Robert E.; Manning, Mary E.; Duncan, Jacob P.; Egan, Joel M.; Jackson, Marcus B.; Kegley, Sandra; Lockman, I. Blakey; Pearson, Dean E.; Powell, James A.; Shelly, Steve; Steed, Brytten E.; Zambino, Paul J.; Halofsky, Jessica E.; Peterson, David L.

2018-01-01

Disturbances alter ecosystem, community, or population structure and change elements of the biological and/or physical environment. Climate changes can alter the timing, magnitude, frequency, and duration of disturbance events, as well as the interactions of disturbances on a landscape, and climate change may already be affecting disturbance events and regimes. Interactions among disturbance regimes, such as the cooccurrence in space and time of bark beetle outbreaks and wildfires, can result in highly visible, rapidly occurring, and persistent changes in landscape composition and structure. Understanding how altered disturbance patterns and multiple disturbance interactions might result in novel and emergent landscape behaviors is critical for addressing climate change impacts and for designing land management strategies that are appropriate for future climates This chapter describes the ecology of important disturbance regimes in the Northern Rockies region, and potential shifts in these regimes as a consequence of observed and projected climate change. We summarize five disturbance types present in the Northern Rockies that are sensitive to a changing climate--wildfires, bark beetles, white pine blister rust (Cronartium ribicola), other forest diseases, and nonnative plant invasions—and provide information that can help managers anticipate how, when, where, and why climate changes may alter the characteristics of disturbance regimes.

Identification of sequence changes in live attenuated goose parvovirus vaccine strains developed in Asia and Europe.

PubMed

Shien, J-H; Wang, Y-S; Chen, C-H; Shieh, H K; Hu, C-C; Chang, P-C

2008-10-01

Live attenuated vaccines have been used for control of the disease caused by goose parvovirus (GPV), but the mechanism involved in attenuation of GPV remains elusive. This report presents the complete nucleotide sequences of two live attenuated strains of GPV (82-0321V and VG32/1) that were independently developed in Taiwan and Europe, together with the parental strain of 82-0321V and a field strain isolated in Taiwan in 2006. Sequence comparisons showed that 82-0321V and VG32/1 had multiple deletions and substitutions in the inverted terminal repeats region when compared with their parental strain or the field virus, but these changes did not affect the formation of the hairpin structure essential for viral replication. Moreover, 82-0321V and VG32/1 had five amino acid changes in the non-structural protein, but these changes were located at positions distant from known functional motifs in the non-structural protein. In contrast, 82-0321V had nine changes and VG32/1 had 11 changes in their capsid proteins (VP1), and the majority of these changes occurred at positions close to the putative receptor binding sites of VP1, as predicted using the structure of adeno-associated virus 2 as the model system. Taken together, the results suggest that changes in sequence near the receptor binding sites of VP1 might be responsible for attenuation of GPV. This is the first report of complete nucleotide sequences of GPV other than the virulent B strain, and suggests a possible mechanism for attenuation of GPV.

Structural-Phase Transformations of CuZn Alloy Under Thermal-Impact Cycling

NASA Astrophysics Data System (ADS)

Potekaev, A. I.; Chaplygina, A. A.; Kulagina, V. V.; Chaplygin, P. A.; Starostenkov, M. D.; Grinkevich, L. S.

2017-02-01

Using the Monte Carlo method, special features of structural - phase transformations in β-brass are investigated during thermal impact using thermal cycling as an example (a number of successive order - disorder and disorder - order phase transitions in the course of several heating - cooling cycles). It is shown that a unique hysteresis is observed after every heating and cooling cycle, whose presence indicates irreversibility of the processes, which suggests a difference in the structural - phase states both in the heating and cooling stages. A conclusion is drawn that the structural - phase transformations in the heating and cooling stages occur within different temperature intervals, where the thermodynamic stimuli of one or the other structural - phase state are low. This is also demonstrated both in the plots of configurational energy, long- and short-range order parameter, atomic structure variations, and structural - phase state distributions. Simultaneously, there coexist ordered and disordered phases and a certain collection of superstructure domains. This implies the presence of low - stability states in the vicinity of the order - disorder phase transition. The results of investigations demonstrate that the structural - phase transitions within two successive heating and cooling cycles at the same temperature are different in both stages. These changes, though not revolutionary, occur in every cycle and decrease with the increasing cycle number. In fact, the system undergoes training with a tendency towards a certain sequence of structural - phase states.

Structural change and higher educated labour in Indonesia.

PubMed

Pasay, N H

1990-12-01

This paper describes an impending shortage of higher-educated labor in Indonesia. Dynamic change is occurring in both Indonesia's population and economy. Its rapidly growing population demands annual national economic growth of 2.2% to avoid declining per capita output. Accordingly, investments have surged in banking and manufacturing industries as Indonesia undergoes structural change from an agricultural to service-based economy. Plagued by a majority of low productivity, elementary-level educated workers, increased productivity is called for to ensure continued development. As the age structural shift progresses, many of these workers will be absorbed in the services sector. Jobs exist requiring workers of all skill levels. This paper is mainly concerned, however, with higher-educated labor's failure to be oriented to the research and development required for sustained economic growth and development, and their entry into clerical positions potentially filled by less educated and less skilled labor. The services sector, particularly public services, is responsible for absorbing much of this labor. As professional, technical, and managerial capabilities and qualifications become increasingly needed in the near future as sector investments take effect, a shortage of higher-educated labor will become apparent. Policy makers are advised to anticipate these shortages and contemplate investments in human capital to facilitate a more smooth adjustment to structural change.

Local Knowledge About The Structure, Function And Conversion Of Landscape In The Karangwangi Village, Cianjur, West Java, Indonesia

NASA Astrophysics Data System (ADS)

Ulfa Dwi Amelia, Fatiya; Iskandar, Johan

2017-10-01

Karangwangi people is one of indigenous people in West Java who has local knowledge about their nature thoroughly. They have local tradition about landscape ecosystem arrangement that based on sakral (sacred) norm. With this rule, local people will always try to preserve the sustainability of their natural environment. However, modernization, increasing population, decreasing forest, and increasing market economic penetration, causing this rule and structure of landscape in Karangwangi village has changed. Land conversion in Karangwangi was occur because of settlement and land investment by people outside the village. These behavior changes in tradition and landscape (structure, function and conversion) in Karangwangi may impact on their daily activities, and so do the changes in daily activities can change their behavior in tradition and landscape. This research was undertaken in the Village of Karangwangi, Sub-district of Cidaun, District of Cianjur, Province of West Java, Indonesia. This paper aims to identify how indigenous people in Karangwangi understand kinds of landscape and another conversion that was happen as a result of management. The method used in this paper is qualitative with ethno ecological approach. The resulted of the study show that local people in Karangwangi Village understand how chronological of landscape structure, function and conversion.

Unveiling the complex network of interactions in Ionic Liquids: a combined EXAFS and Molecular Dynamics approach

NASA Astrophysics Data System (ADS)

Serva, A.; Migliorati, V.; Lapi, A.; D'Angelo, P.

2016-05-01

The structural properties of geminal dicationic ionic liquids ([Cn (mim)2]Br2)/water mixtures have been investigated by means of extended X-ray absorption fine structure (EXAFS) spectroscopy and Molecular Dynamics (MD) simulations. This synergic approach allowed us to assess the reliability of the MD results and to provide accurate structural information about the first coordination shell of the Br- ion. We found that the local environment around the anion changes as a function of the water concentration, while it is the same independently from the length of the bridge-alkyl chain. Moreover, as regards the long-range structural organization, no tail-tail aggregation occurs with increasing alkyl chain length.

Exploring the structural insights on human laforin mutation K87A in Lafora disease--a molecular dynamics study.

PubMed

Srikumar, P S; Rohini, K

2013-10-01

Lafora disease (LD) is an autosomal recessive, progressive form of myoclonus epilepsy which affects worldwide. LD occurs mainly in countries like southern Europe, northern Africa, South India, and in the Middle East. LD occurs with its onset mainly in teenagers and leads to decline and death within 2 to 10 years. The genes EPM2A and EPM2B are commonly involved in 90 % of LD cases. EPM2A codes for protein laforin which contains an amino terminal carbohydrate binding module (CBM) belonging to the CBM20 family and a carboxy terminal dual specificity phosphatase domain. Mutations in laforin are found to abolish glycogen binding and have been reported in wet lab methods. In order to investigate on structural insights on laforin mutation K81A, we performed molecular dynamics (MD) simulation studies for native and mutant protein. MD simulation results showed loss of stability due to mutation K87A which confirmed the structural reason for conformational changes observed in laforin. The conformational change of mutant laforin was confirmed by analysis using root mean square deviation, root mean square fluctuation, solvent accessibility surface area, radius of gyration, hydrogen bond, and principle component analysis. Our results identified that the flexibility of K87A mutated laforin structure, with replacement of acidic amino acid to aliphatic amino acid in functional CBM domain, have more impact in abolishing glycogen binding that favors LD.

Crisis management during anaesthesia: embolism

PubMed Central

Williamson, J; Helps, S; Westhorpe, R; Mackay, P

2005-01-01

Background: Embolism with gas, thrombus, fat, amniotic fluid, or particulate matter may occur suddenly and unexpectedly during anaesthesia, posing a diagnostic and management problem for the anaesthetist. Objectives: To examine the role of a previously described core algorithm "COVER ABCD–A SWIFT CHECK" supplemented by a specific sub-algorithm for embolism, in the management of embolism occurring in association with anaesthesia. Methods: The potential performance of this structured approach for each of the relevant incidents among the first 4000 reported to the Australian Incident Monitoring Study (AIMS) was compared with the actual management as reported by the anaesthetists involved. Results: Among the first 4000 incidents reported to AIMS, 38 reports of embolism were found. A sudden fall in end-tidal carbon dioxide and oxygen saturation were the cardinal signs of embolism, each occurring in about two thirds of cases, with hypotension and electrocardiographic changes each occurring in about one third of cases. Conclusion: The potential value of an explicit structured approach to the diagnosis and management of embolism was assessed in the light of AIMS reports. It was considered that, correctly applied, it potentially would have led to earlier recognition of the problem and/or better management in over 40% of cases. PMID:15933290

DNA packaging intermediates of bacteriophage Φ174

PubMed Central

Music, Cynthia L; Cheng, R Holland; Bowen, Zorina; McKenna, Robert; Rossmann, Michael G; Baker, Timothy S; Incardona, Nino L

2014-01-01

Background Like many viruses, bacteriophage ΦX174 packages its I)NA genome into a procapsid that is assembled from structural intermediates and scaffolding proteins. The procapsid contains the structural proteins F, G and H, as well as the scaffolding proteins B and D. Provirions are formed by packaging of DNA together with the small internal J proteins, while losing at least some of the B scaffolding proteins. Eventually, loss of the I) scaffolding proteins and the remaining B proteins leads to the formation of mature virions. Results ΦX174 108S 'procapsids' have been purified in milligram quantities by removing 114S (mature virion) and 70S (abortive capsid) particles from crude lysates by differential precipitation with polyethylene glycol. 132S 'provirions' were purified on sucrose gradients in the presence of EDTA. Cryo-electron microscopy (cryo-EM) was used to obtain reconstructions of procapsids and provirions. Although these are very similar to each other, their structures differ greatly from that of the virion. The F and G proteins, whose atomic structures in virions were previously determined from X-ray crystallography, were fitted into the cryo-EM reconstructions. This showed that the pentamer of G proteins on each five-fold vertex changes its conformation only slightly during DNA packaging and maturation, whereas major tertiary and quaternary structural changes occur in the F protein. The procapsids and provirions were found to contain 120 copies of the I) protein arranged as tetramers on the twofold axes. IDNA might enter procapsids through one of the 30 Å diameter holes on the icosahedral three-fold axes. Conclusions Combining cryo-EM image reconstruction and X-ray crystallography has revealed the major conformational changes that can occur in viral assembly. The function of the scaffolding proteins may be, in part, to support weak interactions between the structural proteins in the procapsids and to cover surfaces that are subsequently required for subunit–subunit interaction in the virion. The structures presented here are, therefore, analogous to chaperone proteins complexed with folding intermediates of a substrate. PMID:7613866

Land-use and land-management change: relationships with earthworm and fungi communities and soil structural properties.

PubMed

Spurgeon, David J; Keith, Aidan M; Schmidt, Olaf; Lammertsma, Dennis R; Faber, Jack H

2013-12-01

Change in land use and management can impact massively on soil ecosystems. Ecosystem engineers and other functional biodiversity in soils can be influenced directly by such change and this in turn can affect key soil functions. Here, we employ meta-analysis to provide a quantitative assessment of the effects of changes in land use and land management across a range of successional/extensification transitions (conventional arable → no or reduced tillage → grassland → wooded land) on community metrics for two functionally important soil taxa, earthworms and fungi. An analysis of the relationships between community change and soil structural properties was also included. Meta-analysis highlighted a consistent trend of increased earthworm and fungal community abundances and complexity following transitions to lower intensity and later successional land uses. The greatest changes were seen for early stage transitions, such as introduction of reduced tillage regimes and conversion to grassland from arable land. Not all changes, however, result in positive effects on the assessed community metrics. For example, whether woodland conversion positively or negatively affects community size and complexity depends on woodland type and, potentially, the changes in soil properties, such as pH, that may occur during conversion. Alterations in soil communities tended to facilitate subsequent changes in soil structure and hydrology. For example, increasing earthworm abundances and functional group composition were shown to be positively correlated with water infiltration rate (dependent on tillage regime and habitat characteristics); while positive changes in fungal biomass measures were positively associated with soil microaggregate stability. These findings raise the potential to manage landscapes to increase ecosystem service provision from soil biota in relation to regulation of soil structure and water flow.

A Systematic Investigation of the Effect of Action Observation Training and Motor Imagery Training on the Development of Mental Representation Structure and Skill Performance

PubMed Central

Kim, Taeho; Frank, Cornelia; Schack, Thomas

2017-01-01

Action observation training and motor imagery training have independently been studied and considered as an effective training strategy for improving motor skill learning. However, comparative studies of the two training strategies are relatively few. The purpose of this study was to investigate the effects of action observation training and motor imagery training on the development of mental representation structure and golf putting performance as well as the relation between the changes in mental representation structure and skill performance during the early learning stage. Forty novices were randomly assigned to one of four groups: action observation training, motor imagery training, physical practice and no practice. The mental representation structure and putting performance were measured before and after 3 days of training, then after a 2-day retention period. The results showed that mental representation structure and the accuracy of the putting performance were improved over time through the two types of cognitive training (i.e., action observation training and motor imagery training). In addition, we found a significant positive correlation between changes in mental representation structure and skill performance for the action observation training group only. Taken together, these results suggest that both cognitive adaptations and skill improvement occur through the training of the two simulation states of action, and that perceptual-cognitive changes are associated with the change of skill performance for action observation training. PMID:29089881

Small-Angle Neutron Scattering Reveals pH-Dependent Conformational Changes in Trichoderma reesei Cellobiohydrolase I: Implications for Enzymatic Activity

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pingali, Sai Venkatesh; O'Neill, Hugh Michael; McGaughey, Joseph

2011-01-01

Cellobiohydrolase I (Cel7A) of the fungus Trichoderma reesei (now classified as an anamorph of Hypocrea jecorina) hydrolyzes crystalline cellulose to soluble sugars, making it of key interest for producing fermentable sugars from biomass for biofuel production. The activity of the enzyme is pH-dependent, with its highest activity occurring at pH 4 5. To probe the response of the solution structure of Cel7A to changes in pH, we measured small angle neutron scattering of it in a series of solutions having pH values of 7.0, 6.0, 5.3, and 4.2. As the pH decreases from 7.0 to 5.3, the enzyme structure remainsmore » well defined, possessing a spatial differentiation between the cellulose binding domain and the catalytic core that only changes subtly. At pH 4.2, the solution conformation of the enzyme changes to a structure that is intermediate between a properly folded enzyme and a denatured, unfolded state, yet the secondary structure of the enzyme is essentially unaltered. The results indicate that at the pH of optimal activity, the catalytic core of the enzyme adopts a structure in which the compact packing typical of a fully folded polypeptide chain is disrupted and suggest that the increased range of structures afforded by this disordered state plays an important role in the increased activity of Cel7A through conformational selection.« less

New Umami Amides: Structure-Taste Relationship Studies of Cinnamic Acid Derived Amides and the Natural Occurrence of an Intense Umami Amide in Zanthoxylum piperitum.

PubMed

Frerot, Eric; Neirynck, Nathalie; Cayeux, Isabelle; Yuan, Yoyo Hui-Juan; Yuan, Yong-Ming

2015-08-19

A series of aromatic amides were synthesized from various acids and amines selected from naturally occurring structural frameworks. These synthetic amides were evaluated for umami taste in comparison with monosodium glutamate. The effect of the substitution pattern of both the acid and the amine parts on umami taste was investigated. The only intensely umami-tasting amides were those made from 3,4-dimethoxycinnamic acid. The amine part was more tolerant to structural changes. Amides bearing an alkyl- or alkoxy-substituted phenylethylamine residue displayed a clean umami taste as 20 ppm solutions in water. Ultraperformance liquid chromatography coupled with a high quadrupole-Orbitrap mass spectrometer (UPLC/MS) was subsequently used to show the natural occurrence of these amides. (E)-3-(3,4-Dimethoxyphenyl)-N-(4-methoxyphenethyl)acrylamide was shown to occur in the roots and stems of Zanthoxylum piperitum, a plant of the family Rutaceae growing in Korea, Japan, and China.

Time-resolved observation of protein allosteric communication

PubMed Central

Buchenberg, Sebastian; Sittel, Florian; Stock, Gerhard

2017-01-01

Allostery represents a fundamental mechanism of biological regulation that is mediated via long-range communication between distant protein sites. Although little is known about the underlying dynamical process, recent time-resolved infrared spectroscopy experiments on a photoswitchable PDZ domain (PDZ2S) have indicated that the allosteric transition occurs on multiple timescales. Here, using extensive nonequilibrium molecular dynamics simulations, a time-dependent picture of the allosteric communication in PDZ2S is developed. The simulations reveal that allostery amounts to the propagation of structural and dynamical changes that are genuinely nonlinear and can occur in a nonlocal fashion. A dynamic network model is constructed that illustrates the hierarchy and exceeding structural heterogeneity of the process. In compelling agreement with experiment, three physically distinct phases of the time evolution are identified, describing elastic response (≲0.1 ns), inelastic reorganization (∼100 ns), and structural relaxation (≳1μs). Issues such as the similarity to downhill folding as well as the interpretation of allosteric pathways are discussed. PMID:28760989

The effects of graded levels of calorie restriction: VII. Topological rearrangement of hypothalamic aging networks.

PubMed

Derous, Davina; Mitchell, Sharon E; Green, Cara L; Wang, Yingchun; Han, Jing Dong J; Chen, Luonan; Promislow, Daniel E L; Lusseau, David; Speakman, John R; Douglas, Alex

2016-05-01

Connectivity in a gene-gene network declines with age, typically within gene clusters. We explored the effect of short-term (3 months) graded calorie restriction (CR) (up to 40 %) on network structure of aging-associated genes in the murine hypothalamus by using conditional mutual information. The networks showed a topological rearrangement when exposed to graded CR with a higher relative within cluster connectivity at 40CR. We observed changes in gene centrality concordant with changes in CR level, with Ppargc1a, and Ppt1 having increased centrality and Etfdh, Traf3 and Abcc1 decreased centrality as CR increased. This change in gene centrality in a graded manner with CR, occurred in the absence of parallel changes in gene expression levels. This study emphasizes the importance of augmenting traditional differential gene expression analyses to better understand structural changes in the transcriptome. Overall our results suggested that CR induced changes in centrality of biological relevant genes that play an important role in preventing the age-associated loss of network integrity irrespective of their gene expression levels.

The effects of graded levels of calorie restriction: VII. Topological rearrangement of hypothalamic aging networks

PubMed Central

Derous, Davina; Mitchell, Sharon E.; Green, Cara L.; Wang, Yingchun; Han, Jing Dong J.; Chen, Luonan; Promislow, Daniel E.L.; Lusseau, David; Speakman, John R.; Douglas, Alex

2016-01-01

Connectivity in a gene-gene network declines with age, typically within gene clusters. We explored the effect of short-term (3 months) graded calorie restriction (CR) (up to 40 %) on network structure of aging-associated genes in the murine hypothalamus by using conditional mutual information. The networks showed a topological rearrangement when exposed to graded CR with a higher relative within cluster connectivity at 40CR. We observed changes in gene centrality concordant with changes in CR level, with Ppargc1a, and Ppt1 having increased centrality and Etfdh, Traf3 and Abcc1 decreased centrality as CR increased. This change in gene centrality in a graded manner with CR, occurred in the absence of parallel changes in gene expression levels. This study emphasizes the importance of augmenting traditional differential gene expression analyses to better understand structural changes in the transcriptome. Overall our results suggested that CR induced changes in centrality of biological relevant genes that play an important role in preventing the age-associated loss of network integrity irrespective of their gene expression levels. PMID:27115072

Historic changes in fish assemblage structure in midwestern nonwadeable rivers

USGS Publications Warehouse

Parks, Timothy P.; Quist, Michael C.; Pierce, Clay L.

2014-01-01

Historical change in fish assemblage structure was evaluated in the mainstems of the Des Moines, Iowa, Cedar, Wapsipinicon, and Maquoketa rivers, in Iowa. Fish occurrence data were compared in each river between historical and recent time periods to characterize temporal changes among 126 species distributions and assess spatiotemporal patterns in faunal similarity. A resampling procedure was used to estimate species occurrences in rivers during each assessment period and changes in species occurrence were summarized. Spatiotemporal shifts in species composition were analyzed at the river and river section scale using cluster analysis, pairwise Jaccard's dissimilarities, and analysis of multivariate beta dispersion. The majority of species exhibited either increases or declines in distribution in all rivers with the exception of several “unknown” or inconclusive trends exhibited by species in the Maquoketa River. Cluster analysis identified temporal patterns of similarity among fish assemblages in the Des Moines, Cedar, and Iowa rivers within the historical and recent assessment period indicating a significant change in species composition. Prominent declines of backwater species with phytophilic spawning strategies contributed to assemblage changes occurring across river systems.

A Generation at Risk: Growing Up in an Era of Family Upheaval.

ERIC Educational Resources Information Center

Amato, Paul R.; Booth, Alan

During the last three decades, remarkable transformations have occurred in the American family, including changes in economic well-being, gender roles, family relationships, and family structure. Based on a 15-year study begun in 1980, this book examines young Americans coming of age in the 1980s and 1990s among families experiencing these social…

Hardwood crown injuries and rebuilding following ice storms: a literature review

Treesearch

Martin J. Kraemer; Ralph D. Nyland

2010-01-01

Ice storms occur frequently in northeastern North America. They damage and kill trees, change the structural characteristics of a forest, and may importantly alter the goods and services that owners realize from their land. This literature review summarizes 90 years of relevant information, mainly from fairly short term studies published between 1904 and 2006. It...

Distribution of Personal Income in Agriculture-Dependent Counties of Midwestern States: A Policy Variables Approach.

ERIC Educational Resources Information Center

Goreham, Gary A.; And Others

Significant social, demographic, and economic changes have occurred in the North Central states since 1960. This document examines structural and policy variables related to distribution of income, during the years 1960-80 in the 397 counties defined as agriculture-dependent in 13 North Central states. Personal income distribution has been…

Alabama’s forests, 2010

Treesearch

Andrew J. Hartsell; Jason A. Cooper

2013-01-01

The principle findings of the ninth forest survey of Alabama (2010) and changes that have occurred since the previous surveys are presented. Topics examined include forest area, ownership, forest-type groups, stand structure, basal area, timber volume, growth removals, and mortality. Alabama’s contribution to the Nation’s forest resources and regional comparisons are...

Implementation of a Technological Innovation: Factors Influencing the Adoption of a New Student Information System

ERIC Educational Resources Information Center

Johnston, Katrina M.

2013-01-01

School information systems (SIS) have the potential to cause a change in a school's technical, structural, psycho-social, and managerial systems. Implementation of a technological innovation such as an SIS is not a one-step occurrence; it is a process that occurs over time. Implementing any technological innovation involves active learning…

Cicada emergence in southwestern riparian forest: Influences of wildfire and vegetation composition

Treesearch

D. Max Smith; Jeffrey Kelly; Deborah M. Finch

2006-01-01

Annually emerging cicadas are a numerically and ecologically dominant species in Southwestern riparian forests. Humans have altered disturbance regimes that structure these forests such that floods are less common and wildfires occur more frequently than was historically the case. Impacts of these changes on primary consumers such as riparian cicadas are unknown....

What (Who?) Buggered up the English Department? An End of Career Moan

ERIC Educational Resources Information Center

Sutherland, John

2012-01-01

In this article Sutherland surveys over the period of the last 40 years (the length of an average full academic career) the changes which have occurred to the departmental structures and procedures in the teaching of and research into English Literature in British universities. He perceives a marginalization of the English department in the…

Do Sons or Daughters Give More Money to Parents in Urban China?

ERIC Educational Resources Information Center

Xie, Yu; Zhu, Haiyan

2009-01-01

The patriarchal structure of the traditional Chinese family suggests that sons, more than daughters, provide financial support to elderly parents. The norm of receiving support in old age primarily from sons, however, may have been undermined by dramatic demographic, economic, and cultural changes occurring over the last several decades in China,…

Vital Collaboratives, Alliances, and Partnerships: A Search for Key Elements of an Effective Public-Private Partnership

ERIC Educational Resources Information Center

Young, Charles Keith

2010-01-01

Owing to the significant structural changes that have occurred in the global marketplace over the past 2 decades, a corresponding increase of public-private partnerships have been established among the business sector, local governments, and public community colleges. This qualitative project sought to identify and substantiate key elements that…

Persistence of Cognitive Constructs Fostered by Hands-On Science Activities in Middle School Students

ERIC Educational Resources Information Center

Christensen, Rhonda; Knezek, Gerald; Tyler-Wood, Tandra; Gibson, David

2013-01-01

The purpose of this paper is to determine whether the changes that were found to occur pre- to post intervention in students' cognitive structures (Mills, 2013; Knezek, Christensen, Tyler-Wood, & Periathiruvadi, 2013) continued to persist two years later. Major findings were: a) semantic perception of science and STEM as a career became more…

An Update of Marketing Student Perceptions of Learning Activities: Structure, Preferences, and Effectiveness

ERIC Educational Resources Information Center

Karns, Gary L.

2005-01-01

Many changes have occurred in the context of marketing education during the past decade, including the increased use of new technology-based and experiential pedagogies. To update the understanding of how students in advanced marketing courses perceive marketing pedagogies in this new context, a replication and extension of Karns's study of…

Choices and Challenges: A Qualitative Exploration of Professional Women's Career Patterns

ERIC Educational Resources Information Center

Whitmarsh, Lona; Brown, Donalee; Cooper, Jane; Hawkins-Rodgers, Yolanda; Wentworth, Diane Keyser

2007-01-01

With the rapid changes occurring in the role of work in women's lives, this research project was designed to examine the career planning, career decision making, and work history of women in both female-dominated and gender-neutral careers (U.S. Department of Labor, n.d.-a). A qualitative analysis of structured interviews identified 6 emerging…

Effect of peptides Lys-Glu-Asp-Gly and Ala-Glu-Asp-Gly on the morphology of the thymus in hypophysectomized young and old birds.

PubMed

Pateyk, A V; Baranchugova, L M; Rusaeva, N S; Obydenko, V I; Kuznik, B I

2013-03-01

Investigations were carried out on chicks of different age. It was found that the most pronounced changes in the morphology of the thymus occurred after neonatal hypophysectomy. These changes are least pronounced in old chicks. Peptides Lys-Glu-Asp-Gly and Ala-Glu-Asp-Gly synthesized on the basis of amino acid composition of peptide complexes of the anterior and posterior pituitary lobes administered to hypophysectomized birds regardless of age promoted recovery of the morphological structures of the thymus. The anterior pituitary peptide (Lys-Glu-Asp-Gly) had more pronounced effect on the recovery of thymic structure than posterior pituitary peptide (Ala-Glu-Asp-Gly).

Endotoxin-Induced Structural Transformations in Liquid Crystalline Droplets

NASA Astrophysics Data System (ADS)

Lin, I.-Hsin; Miller, Daniel S.; Bertics, Paul J.; Murphy, Christopher J.; de Pablo, Juan J.; Abbott, Nicholas L.

2011-06-01

The ordering of liquid crystals (LCs) is known to be influenced by surfaces and contaminants. Here, we report that picogram per milliliter concentrations of endotoxin in water trigger ordering transitions in micrometer-size LC droplets. The ordering transitions, which occur at surface concentrations of endotoxin that are less than 10-5 Langmuir, are not due to adsorbate-induced changes in the interfacial energy of the LC. The sensitivity of the LC to endotoxin was measured to change by six orders of magnitude with the geometry of the LC (droplet versus slab), supporting the hypothesis that interactions of endotoxin with topological defects in the LC mediate the response of the droplets. The LC ordering transitions depend strongly on glycophospholipid structure and provide new designs for responsive soft matter.

Origin and development of plains-type folds in the mid-continent (United States) during the late Paleozoic

USGS Publications Warehouse

Merriam, D.F.

2005-01-01

Plains-type folds are local, subtle anticlines formed in the thin sedimentary package overlying a shallow, crystalline basement on the craton. They are small in areal extent (usually less than 1-3 km 2 [0.4-1.2 mi2]), and their amplitude increases with depth (usually tens of meters), which is mainly the result of differential compaction of sediments (usually clastic units) over tilted, rigid, basement fault blocks. The development of these structural features by continuous but intermittent movement of the basement fault blocks in the late Paleozoic in the United States mid-continent is substantiated by a record of stratigraphic and sedimentological evidence. The recurrent structural movement, which reflects adjustment to external stresses, is expressed by the change in thickness of stratigraphic units over the crest of the fold compared to the flanks. By plotting the change in thickness for different stratigraphic units of anticlines on different fault blocks, it is possible to determine the timing of movement of the blocks that reflect structural adjustment. These readjustments are confirmed by sedimentological evidence, such as convolute, soft-sediment deformation features and small intraformational faults. The stratigraphic interval change in thickness for numerous structures in the Cherokee, Forest City, and Salina basins and on the Nemaha anticline of the mid-continent United States was determined and compared for location and timing of the adjustments. Most of the adjustment occurred during and after time of deposition of the Permian-Pennsylvanian clastic units, which, in turn, reflect tectonic disturbance in adjacent areas, and the largest amount of movement on the plains-type structures occurred on those nearest and semiparallel to major positive features, such as the Nemaha anticline. Depending on the time of origin and development of plains-type folds, they may control the entrapment and occurrence of oil and gas. Copyright ??2005. The American Association of Petroleum Geologists. All rights reserved.

Structural overshoot of tree growth with climate variability and the global spectrum of drought-induced forest dieback.

PubMed

Jump, Alistair S; Ruiz-Benito, Paloma; Greenwood, Sarah; Allen, Craig D; Kitzberger, Thomas; Fensham, Rod; Martínez-Vilalta, Jordi; Lloret, Francisco

2017-09-01

Ongoing climate change poses significant threats to plant function and distribution. Increased temperatures and altered precipitation regimes amplify drought frequency and intensity, elevating plant stress and mortality. Large-scale forest mortality events will have far-reaching impacts on carbon and hydrological cycling, biodiversity, and ecosystem services. However, biogeographical theory and global vegetation models poorly represent recent forest die-off patterns. Furthermore, as trees are sessile and long-lived, their responses to climate extremes are substantially dependent on historical factors. We show that periods of favourable climatic and management conditions that facilitate abundant tree growth can lead to structural overshoot of aboveground tree biomass due to a subsequent temporal mismatch between water demand and availability. When environmental favourability declines, increases in water and temperature stress that are protracted, rapid, or both, drive a gradient of tree structural responses that can modify forest self-thinning relationships. Responses ranging from premature leaf senescence and partial canopy dieback to whole-tree mortality reduce canopy leaf area during the stress period and for a lagged recovery window thereafter. Such temporal mismatches of water requirements from availability can occur at local to regional scales throughout a species geographical range. As climate change projections predict large future fluctuations in both wet and dry conditions, we expect forests to become increasingly structurally mismatched to water availability and thus overbuilt during more stressful episodes. By accounting for the historical context of biomass development, our approach can explain previously problematic aspects of large-scale forest mortality, such as why it can occur throughout the range of a species and yet still be locally highly variable, and why some events seem readily attributable to an ongoing drought while others do not. This refined understanding can facilitate better projections of structural overshoot responses, enabling improved prediction of changes in forest distribution and function from regional to global scales. © 2017 John Wiley & Sons Ltd.

Structural overshoot of tree growth with climate variability and the global spectrum of drought-induced forest dieback

USGS Publications Warehouse

Jump, Alistair S.; Ruiz-Benito, Paloma; Greenwood, Sarah; Allen, Craig D.; Kitzberger, Thomas; Fensham, Rod; Martínez-Vilalta, Jordi; Lloret, Francisco

2017-01-01

Ongoing climate change poses significant threats to plant function and distribution. Increased temperatures and altered precipitation regimes amplify drought frequency and intensity, elevating plant stress and mortality. Large-scale forest mortality events will have far-reaching impacts on carbon and hydrological cycling, biodiversity, and ecosystem services. However, biogeographical theory and global vegetation models poorly represent recent forest die-off patterns. Furthermore, as trees are sessile and long-lived, their responses to climate extremes are substantially dependent on historical factors. We show that periods of favourable climatic and management conditions that facilitate abundant tree growth can lead to structural overshoot of aboveground tree biomass due to a subsequent temporal mismatch between water demand and availability. When environmental favourability declines, increases in water and temperature stress that are protracted, rapid, or both, drive a gradient of tree structural responses that can modify forest self-thinning relationships. Responses ranging from premature leaf senescence and partial canopy dieback to whole-tree mortality reduce canopy leaf area during the stress period and for a lagged recovery window thereafter. Such temporal mismatches of water requirements from availability can occur at local to regional scales throughout a species geographical range. As climate change projections predict large future fluctuations in both wet and dry conditions, we expect forests to become increasingly structurally mismatched to water availability and thus overbuilt during more stressful episodes. By accounting for the historical context of biomass development, our approach can explain previously problematic aspects of large-scale forest mortality, such as why it can occur throughout the range of a species and yet still be locally highly variable, and why some events seem readily attributable to an ongoing drought while others do not. This refined understanding can facilitate better projections of structural overshoot responses, enabling improved prediction of changes in forest distribution and function from regional to global scales.

Dynamic Investigation of Static Divergence: Analysis and Testing

NASA Technical Reports Server (NTRS)

Heeg, Jennifer

2000-01-01

The phenomenon known as aeroelastic divergence is the focus of this work. The analyses and experiment presented here show that divergence can occur without a structural dynamic mode losing its oscillatory nature. Aeroelastic divergence occurs when the structural restorative capability or stiffness of a structure is overwhelmed by the static aerodynamic moment. This static aeroelastic coupling does not require the structural dynamic system behavior to cease, however. Aeroelastic changes in the dynamic mode behavior are governed not only by the stiffness, but by damping and inertial properties. The work presented here supports these fundamental assertions by examining a simple system: a typical section airfoil with only a rotational structural degree of freedom. Analytical results identified configurations that exhibit different types of dynamic mode behavior as the system encounters divergence. A wind tunnel model was designed and tested to examine divergence experimentally. The experimental results validate the analytical calculations and explicitly examine the divergence phenomenon where the dynamic mode persists. Three configurations of the wind tunnel model were tested. The experimental results agree very well with the analytical predictions of subcritical characteristics, divergence velocity, and behavior of the noncritical dynamic mode at divergence.

pH-dependent conformational changes of diphtheria toxin adsorbed to lipid monolayers by neutron and X-ray reflection

NASA Astrophysics Data System (ADS)

Kent, Michael; Yim, Hyun; Satija, Sushil; Kuzmenko, Ivan

2006-03-01

Several important bacterial toxins, such as diphtheria, tetanus, and botulinum, invade cells through a process of high affinity binding, internalization via endosome formation, and subsequent membrane penetration of the catalytic domain activated by a pH drop in the endosome. These toxins are composed of three domains: a binding domain, a translocation domain, and an enzyme. The translocation process is not well understood with regard to the detailed conformational changes that occur at each step, To address this, we performed neutron reflectivity measurements for diphtheria toxin bound to lipid monolayers as a function of pH. While the final membrane inserted conformation will not be reproduced with the present monolayer system, important insights can still be gained into several intermediate stages. In particular, we show that no adsorption occurs at pH = 7.6, but strong adsorption occurs over at a pH range from 6.5 to 6.0. Following binding, at least two stages of conformational change occur, as the thickness increases from pH 6.3 to 5.3 and then decreases from pH 5.3 to 4.5. In addition, the dimension of the adsorbed layer substantially exceeds that of the largest dimension in the crystal structure of monomeric diphtheria, suggesting that the toxin may be present as multimers.

Early grey matter changes in structural covariance networks in Huntington's disease.

PubMed

Coppen, Emma M; van der Grond, Jeroen; Hafkemeijer, Anne; Rombouts, Serge A R B; Roos, Raymund A C

2016-01-01

Progressive subcortical changes are known to occur in Huntington's disease (HD), a hereditary neurodegenerative disorder. Less is known about the occurrence and cohesion of whole brain grey matter changes in HD. We aimed to detect network integrity changes in grey matter structural covariance networks and examined relationships with clinical assessments. Structural magnetic resonance imaging data of premanifest HD ( n  = 30), HD patients (n = 30) and controls (n = 30) was used to identify ten structural covariance networks based on a novel technique using the co-variation of grey matter with independent component analysis in FSL. Group differences were studied controlling for age and gender. To explore whether our approach is effective in examining grey matter changes, regional voxel-based analysis was additionally performed. Premanifest HD and HD patients showed decreased network integrity in two networks compared to controls. One network included the caudate nucleus, precuneous and anterior cingulate cortex (in HD p  < 0.001, in pre-HD p  = 0.003). One other network contained the hippocampus, premotor, sensorimotor, and insular cortices (in HD p  < 0.001, in pre-HD p  = 0.023). Additionally, in HD patients only, decreased network integrity was observed in a network including the lingual gyrus, intracalcarine, cuneal, and lateral occipital cortices ( p  = 0.032). Changes in network integrity were significantly associated with scores of motor and neuropsychological assessments. In premanifest HD, voxel-based analyses showed pronounced volume loss in the basal ganglia, but less prominent in cortical regions. Our results suggest that structural covariance might be a sensitive approach to reveal early grey matter changes, especially for premanifest HD.

Picosecond Phase Grating Spectroscopy of Hemoglobin and Myoglobin: Vibrational Relaxation and Global Protein Motions.

NASA Astrophysics Data System (ADS)

Genberg, Laura Lynn

The vibrational energy relaxation pathways from optically excited met heme proteins have been studied using the technique of picosecond phase grating spectroscopy. Vibrational energy transfer from the porphyrin ring to the protein backbone leads to extensive delocalization of the energy in the protein matrix which is efficiently transferred to the water interface in less than 20 ps. A slower relaxation process on the nanosecond time scale is also observed. The slow relaxation component is attributed to slow conformational relaxation processes of high potential energy states of the heme proteins. These states are accessed during the high internal energy conditions of the optically excited molecules. In addition, a detailed theoretical analysis of this form of spectroscopy is presented that explains the effects of delayed thermal energy deposition on grating dynamics. The effects of optical pulse shape and duration are also treated. The observable in this technique is not an electronic polarization, but is derived from a response of the material fields to changes in the lattice temperature. Phase grating spectroscopy is also used to observe picosecond tertiary structural changes in both myoglobin and hemoglobin following CO photodissociation. The original interest in this experiment was to ascertain whether local minima are accessed during the highly exothermic conditions following photodissociation, as was observed in the met heme studies. Photodissociation of CO induces a well defined ligated to deoxy structure transition that is important to the functionality of these proteins. Using grating spectroscopy, protein driven density waves are observed on a picosecond time scale. These waves are launched by the tertiary structural changes that occur in both hemoglobin and myoglobin. The exact shape and amplitude of these waves reveal the time scale for the motion as well as the energetics for these protein motions. This result demonstrates that tertiary structure changes are global in nature and occur on an extremely fast time scale. This provides new insight into the biomechanics of conformational changes in proteins and lends support to theoretical models invoking stored strain energy as the driving force for large amplitude correlated motions.

Structure of an agonist-bound ionotropic glutamate receptor.

PubMed

Yelshanskaya, Maria V; Li, Minfen; Sobolevsky, Alexander I

2014-08-29

Ionotropic glutamate receptors (iGluRs) mediate most excitatory neurotransmission in the central nervous system and function by opening their ion channel in response to binding of agonist glutamate. Here, we report a structure of a homotetrameric rat GluA2 receptor in complex with partial agonist (S)-5-nitrowillardiine. Comparison of this structure with the closed-state structure in complex with competitive antagonist ZK 200775 suggests conformational changes that occur during iGluR gating. Guided by the structures, we engineered disulfide cross-links to probe domain interactions that are important for iGluR gating events. The combination of structural information, kinetic modeling, and biochemical and electrophysiological experiments provides insight into the mechanism of iGluR gating. Copyright © 2014, American Association for the Advancement of Science.

Analysis of population genetic structure and gene flow in an annual plant before and after a rapid evolutionary response to drought.

PubMed

Welt, Rachel S; Litt, Amy; Franks, Steven J

2015-03-27

The impact of environmental change on population structure is not well understood. This study aimed to examine the effect of a climate change event on gene flow over space and time in two populations of Brassica rapa that evolved more synchronous flowering times over 5 years of drought in southern California. Using plants grown from seeds collected before and after the drought, we estimated genetic parameters within and between populations and across generations. We expected that with greater temporal opportunity to cross-pollinate, due to reduced phenological isolation, these populations would exhibit an increase in gene flow following the drought. We found low but significant FST, but no change in FST or Nm across the drought, in contrast to predictions. Bayesian analysis of these data indicates minor differentiation between the two populations but no noticeable change in structure before and after the shift in flowering times. However, we found high and significant levels of FIS, indicating that inbreeding likely occurred in these populations despite self-incompatibility in B. rapa. In this system, we did not find an impact of climate change on gene flow or population structuring. The contribution of gene flow to adaptive evolution may vary by system, however, and is thus an important parameter to consider in further studies of natural responses to environmental change. Published by Oxford University Press on behalf of the Annals of Botany Company.

Influence of pH on the Structure and Function of Kiwi Pectin Methylesterase Inhibitor.

PubMed

Bonavita, Alessandro; Carratore, Vitale; Ciardiello, Maria Antonietta; Giovane, Alfonso; Servillo, Luigi; D'Avino, Rossana

2016-07-27

Pectin methylesterase is a pectin modifying enzyme that plays a key role in plant physiology. It is also an important quality-related enzyme in plant-based food products. The pectin methylesterase inhibitor (PMEI) from kiwifruit inhibits this enzyme activity and is widely used as an efficient tool for research purposes and also recommended in the context of fruit and vegetable processing. Using several methodologies of protein biochemistry, including circular dichroism and fluorescence spectroscopy, chemical modifications, direct protein-sequencing, enzyme activity, and bioinformatics analysis of the crystal structure, this study demonstrates that conformational changes occur in kiwi PMEI by the pH rising over 6.0 bringing about structure loosening, exposure, and cleavage of a natively buried disulfide bond, unfolding and aggregation, ultimately determining the loss of ability of kiwi PMEI to bind and inhibit PME. pH-induced structural changes are prevented when PMEI is already engaged in complex or is in a solution of high ionic strength.

Structure of a bacterial type III secretion system in contact with a host membrane in situ

NASA Astrophysics Data System (ADS)

Nans, Andrea; Kudryashev, Mikhail; Saibil, Helen R.; Hayward, Richard D.

2015-12-01

Many bacterial pathogens of animals and plants use a conserved type III secretion system (T3SS) to inject virulence effector proteins directly into eukaryotic cells to subvert host functions. Contact with host membranes is critical for T3SS activation, yet little is known about T3SS architecture in this state or the conformational changes that drive effector translocation. Here we use cryo-electron tomography and sub-tomogram averaging to derive the intact structure of the primordial Chlamydia trachomatis T3SS in the presence and absence of host membrane contact. Comparison of the averaged structures demonstrates a marked compaction of the basal body (4 nm) occurs when the needle tip contacts the host cell membrane. This compaction is coupled to a stabilization of the cytosolic sorting platform-ATPase. Our findings reveal the first structure of a bacterial T3SS from a major human pathogen engaged with a eukaryotic host, and reveal striking `pump-action' conformational changes that underpin effector injection.

Three-dimensional elastic-plastic finite-element analysis of fatigue crack propagation

NASA Technical Reports Server (NTRS)

Goglia, G. L.; Chermahini, R. G.

1985-01-01

Fatigue cracks are a major problem in designing structures subjected to cyclic loading. Cracks frequently occur in structures such as aircraft and spacecraft. The inspection intervals of many aircraft structures are based on crack-propagation lives. Therefore, improved prediction of propagation lives under flight-load conditions (variable-amplitude loading) are needed to provide more realistic design criteria for these structures. The main thrust was to develop a three-dimensional, nonlinear, elastic-plastic, finite element program capable of extending a crack and changing boundary conditions for the model under consideration. The finite-element model is composed of 8-noded (linear-strain) isoparametric elements. In the analysis, the material is assumed to be elastic-perfectly plastic. The cycle stress-strain curve for the material is shown Zienkiewicz's initial-stress method, von Mises's yield criterion, and Drucker's normality condition under small-strain assumptions are used to account for plasticity. The three-dimensional analysis is capable of extending the crack and changing boundary conditions under cyclic loading.

Changing optical band structure with single photons

NASA Astrophysics Data System (ADS)

Albrecht, Andreas; Caneva, Tommaso; Chang, Darrick E.

2017-11-01

Achieving strong interactions between individual photons enables a wide variety of exciting possibilities in quantum information science and many-body physics. Cold atoms interfaced with nanophotonic structures have emerged as a platform to realize novel forms of nonlinear interactions. In particular, when atoms are coupled to a photonic crystal waveguide, long-range atomic interactions can arise that are mediated by localized atom-photon bound states. We theoretically show that in such a system, the absorption of a single photon can change the band structure for a subsequent photon. This occurs because the first photon affects the atoms in the chain in an alternating fashion, thus leading to an effective period doubling of the system and a new optical band structure for the composite atom-nanophotonic system. We demonstrate how this mechanism can be engineered to realize a single-photon switch, where the first incoming photon switches the system from being highly transmissive to highly reflective, and analyze how signatures can be observed via non-classical correlations of the outgoing photon field.

Structure of a bacterial type III secretion system in contact with a host membrane in situ.

PubMed

Nans, Andrea; Kudryashev, Mikhail; Saibil, Helen R; Hayward, Richard D

2015-12-11

Many bacterial pathogens of animals and plants use a conserved type III secretion system (T3SS) to inject virulence effector proteins directly into eukaryotic cells to subvert host functions. Contact with host membranes is critical for T3SS activation, yet little is known about T3SS architecture in this state or the conformational changes that drive effector translocation. Here we use cryo-electron tomography and sub-tomogram averaging to derive the intact structure of the primordial Chlamydia trachomatis T3SS in the presence and absence of host membrane contact. Comparison of the averaged structures demonstrates a marked compaction of the basal body (4 nm) occurs when the needle tip contacts the host cell membrane. This compaction is coupled to a stabilization of the cytosolic sorting platform-ATPase. Our findings reveal the first structure of a bacterial T3SS from a major human pathogen engaged with a eukaryotic host, and reveal striking 'pump-action' conformational changes that underpin effector injection.

Unraveling the Structural Modifications in Lignin of Arundo donax Linn. during Acid-Enhanced Ionic Liquid Pretreatment.

PubMed

You, Tingting; Zhang, Liming; Guo, Siqin; Shao, Lupeng; Xu, Feng

2015-12-23

Solid acid-enhanced ionic liquid (IL) pretreatment is of paramount importance for boosting the yield of sugars from biomass cost-effectively and environmentally friendly. To unravel the chemical and supramolecular structural changes of lignin after pretreatment, IL-acid lignin (ILAL) and subsequent residual cellulolytic enzyme lignin (RCEL) were isolated from Arundo donax Linn. The structural features were compared with those of the corresponding milled wood lignin (MWL). Results indicated that the pretreatment caused loss of β-O-4', β-β', β-1' linkages and formation of condensed structures in lignin. A preferential breakdown of G-type lignin may have occurred, evidenced by an increased S/G ratio revealed by 2D HSQC NMR analysis. It was determined that the depolymerization of β-O-4' linkage, lignin recondensation, and cleavage of ferulate-lignin ether linkages took place. Moreover, a simulation module was first developed to define morphological changes in lignin based on AFM and TEM analyses. Briefly, tree branch like aggregates was destroyed to monodisperse particles.

Crystal Structure Variations of Sn Nanoparticles upon Heating

NASA Astrophysics Data System (ADS)

Mittal, Jagjiwan; Lin, Kwang-Lung

2018-04-01

Structural changes in Sn nanoparticles during heating below the melting point have been investigated using differential scanning calorimetry (DSC), x-ray diffraction (XRD) analysis, electron diffraction (ED), and high-resolution transmission electron microscopy (HRTEM). DSC revealed that the heat required to melt the nanoparticles (28.43 J/g) was about half compared with Sn metal (52.80 J/g), which was attributed to the large surface energy contribution for the nanoparticles. ED and XRD analyses of the Sn nanoparticles revealed increased intensity for crystal planes having large interplaner distances compared with regular crystal planes with increasing heat treatment temperature (HTT). HRTEM revealed an increase in interlayer spacing at the surface and near joints between nanoparticles with the HTT, leading to an amorphous structure of nanoparticles at the surface at 220°C. These results highlight the changes that occur in the morphology and crystal structure of Sn nanoparticles at the surface and in the interior with increase of the heat treatment temperature.

Age-related changes in the kinetics of human lenses: prevention of the cataract

PubMed Central

Pescosolido, Nicola; Barbato, Andrea; Giannotti, Rossella; Komaiha, Chiara; Lenarduzzi, Fiammetta

2016-01-01

The crystalline lens is a transparent, biconvex structure in the eye that, along with the cornea, helps to refract light to be focused on the retina and, by changing shape, it adjusts focal distance (accommodation). The three classes of structural proteins found in the lens are α, β, and γ crystallins. These proteins make up more than 90% of the total dry mass of the eye lens. Other components which can be found are sugars, lipids, water, several antioxidants and low weight molecules. When ageing changes occur in the lens, it causes a gradual reduction in transparency, presbyopia and an increase in the scattering and aberration of light waves as well as a degradation of the optical quality of the eye. The main changes that occur with aging are: 1) reduced diffusion of water from the outside to the inside of the lens and from its cortical to its nuclear zone; 2) crystalline change due to the accumulation of high molecular weight aggregates and insoluble proteins; 3) production of advanced glycation end products (AGEs), lipid accumulation, reduction of reduced glutathione content and destruction of ascorbic acid. Even if effective strategies in preventing cataract onset are not already known, good results have been reached in some cases with oral administration of antioxidant substances such as caffeine, pyruvic acid, epigallocatechin gallate (EGCG), α-lipoic acid and ascorbic acid. Furthermore, methionine sulfoxide reductase A (MSRA) over expression could protect lens cells both in presence and in absence of oxidative stress-induced damage. Nevertheless, promising results have been obtained by reducing ultraviolet-induced oxidative damage. PMID:27803872

Additional freeze hardiness in wheat acquired by exposure to -3 degreesC is associated with extensive physiological, morphological, and molecular changes.

PubMed

Herman, Eliot M; Rotter, Kelsi; Premakumar, Ramaswamy; Elwinger, G; Bae, Hanhong; Bae, Rino; Ehler-King, Linda; Chen, Sixue; Livingston, David P

2006-01-01

Cold-acclimated plants acquire an additional 3-5 degrees C increase in freezing tolerance when exposed to -3 degrees C for 12-18 h before a freezing test (LT50) is applied. The -3 degrees C treatment replicates soil freezing that can occur in the days or weeks leading to overwintering by freezing-tolerant plants. This additional freezing tolerance is called subzero acclimation (SZA) to differentiate it from cold acclimation (CA) that is acquired at above-freezing temperatures. Using wheat as a model, results have been obtained indicating that SZA is accompanied by changes in physiology, cellular structure, the transcriptome, and the proteome. Using a variety of assays, including DNA arrays, reverse transcription-polymerase chain reaction (RT-PCR), 2D gels with mass spectroscopic identification of proteins, and electron microscopy, changes were observed to occur as a consequence of SZA and the acquisition of added freezing tolerance. In contrast to CA, SZA induced the movement of intracellular water to the extracellular space. Many unknown and stress-related genes were upregulated by SZA including some with obvious roles in SZA. Many genes related to photosynthesis and plastids were downregulated. Changes resulting from SZA often appeared to be a loss of rather than an appearance of new proteins. From a cytological perspective, SZA resulted in alterations of organelle structure including the Golgi. The results indicate that the enhanced freezing tolerance of SZA is correlated with a wide diversity of changes, indicating that the additional freezing tolerance is the result of complex biological processes.

Nb K-edge x-ray absorption investigation of the pressure induced amorphization in A-site deficient double perovskite La1/3NbO3.

PubMed

Marini, C; Noked, O; Kantor, I; Joseph, B; Mathon, O; Shuker, R; Kennedy, B J; Pascarelli, S; Sterer, E

2016-02-03

Nb K-edge x-ray absorption spectroscopy is utilized to investigate the changes in the local structure of the A-site deficient double perovskite La1/3NbO3 which undergoes a pressure induced irreversible amorphization. EXAFS results show that with increasing pressure up to 7.5 GPa, the average Nb-O bond distance decreases in agreement with the expected compression and tilting of the NbO6 octahedra. On the contrary, above 7.5 GPa, the average Nb-O bond distance show a tendency to increase. Significant changes in the Nb K-edge XANES spectrum with evident low energy shift of the pre-peak and the absorption edge is found to happen in La1/3NbO3 above 6.3 GPa. These changes evidence a gradual reduction of the Nb cations from Nb(5+) towards Nb(4+) above 6.3 GPa. Such a valence change accompanied by the elongation of the average Nb-O bond distances in the octahedra, introduces repulsion forces between non-bonding adjacent oxygen anions in the unoccupied A-sites. Above a critical pressure, the Nb reduction mechanism can no longer be sustained by the changing local structure and amorphization occurs, apparently due to the build-up of local strain. EXAFS and XANES results indicate two distinct pressure regimes having different local and electronic response in the La1/3NbO3 system before the occurence of the pressure induced amorphization at  ∼14.5 GPa.

Evidence of early ultrastructural photoreceptor abnormalities in light-induced retinal degeneration using spectral domain optical coherence tomography.

PubMed

Aziz, Mehak K; Ni, Aiguo; Esserman, Denise A; Chavala, Sai H

2014-07-01

To study spatiotemporal in vivo changes in retinal morphology and quantify thickness of retinal layers in a mouse model of light-induced retinal degeneration using spectral domain optical coherence tomography (SD-OCT). BALB/c mice were exposed to 5000 lux of constant light for 3 h. SD-OCT images were taken 3 h, 24 h, 3 days, 1 week and 1 month after light exposure and were compared with histology at the same time points. SD-OCT images were also taken at 0, 1 and 2 h after light exposure in order to analyse retinal changes at the earliest time points. The thickness of retinal layers was measured using the Bioptigen software InVivoVue Diver. SD-OCT demonstrated progressive outer retinal thinning. 3 h after light exposure, the outer nuclear layer converted from hyporeflective to hyper-reflective. At 24 h, outer retinal bands and nuclear layer demonstrated similar levels of hyper-reflectivity. Significant variations in outer retinal thickness, vitreous opacities and retinal detachments occurred within days of injury. Thinning of the retina was observed at 1 month after injury. It was also determined that outer nuclear layer changes precede photoreceptor segment structure disintegration and the greatest change in segment structure occurs between 1 and 2 h after light exposure. Longitudinal SD-OCT reveals intraretinal changes that cannot be observed by histopathology at early time points in the light injury model. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://group.bmj.com/group/rights-licensing/permissions.

Plasticity in the adult human auditory brainstem following short-term linguistic training

PubMed Central

Song, Judy H.; Skoe, Erika; Wong, Patrick C. M.; Kraus, Nina

2009-01-01

Peripheral and central structures along the auditory pathway contribute to speech processing and learning. However, because speech requires the use of functionally and acoustically complex sounds which necessitates high sensory and cognitive demands, long-term exposure and experience using these sounds is often attributed to the neocortex with little emphasis placed on subcortical structures. The present study examines changes in the auditory brainstem, specifically the frequency following response (FFR), as native English-speaking adults learn to incorporate foreign speech sounds (lexical pitch patterns) in word identification. The FFR presumably originates from the auditory midbrain, and can be elicited pre-attentively. We measured FFRs to the trained pitch patterns before and after training. Measures of pitch-tracking were then derived from the FFR signals. We found increased accuracy in pitch-tracking after training, including a decrease in the number of pitch-tracking errors and a refinement in the energy devoted to encoding pitch. Most interestingly, this change in pitch-tracking accuracy only occurred in the most acoustically complex pitch contour (dipping contour), which is also the least familiar to our English-speaking subjects. These results not only demonstrate the contribution of the brainstem in language learning and its plasticity in adulthood, but they also demonstrate the specificity of this contribution (i.e., changes in encoding only occurs in specific, least familiar stimuli, not all stimuli). Our findings complement existing data showing cortical changes after second language learning, and are consistent with models suggesting that brainstem changes resulting from perceptual learning are most apparent when acuity in encoding is most needed. PMID:18370594

Ab initio density functional theory investigation of Li-intercalated silicon carbide nanotube bundles

NASA Astrophysics Data System (ADS)

Moradian, Rostam; Behzad, Somayeh; Chegel, Raad

2009-06-01

We present the results of ab initio density functional theory calculations on the energetic, and geometric and electronic structure of Li-intercalated ( 6,6) silicon carbide nanotube (SiCNT) bundles. Our results show that intercalation of lithium leads to the significant changes in the geometrical structure. The most prominent effect of Li intercalation on the electronic band structure is a shift of the Fermi energy which occurs as a result of charge transfer from lithium to the SiCNTs. All the Li-intercalated ( 6,6) SiCNT bundles are predicted to be metallic representing a substantial change in electronic properties relative to the undoped bundle, which is a wide band gap semiconductor. Both inside of the nanotube and the interstitial space are susceptible for intercalation. The present calculations suggest that the SiCNT bundle is a promising candidate for the anode material in battery applications.

Trouble shooting in toxicopathology

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rousseaux, C.G.

2005-09-01

Toxicopathology, also referred to as toxicologic pathology, can be defined as the study of structural and functional changes in cells, tissues, and organs that are induced by toxicants (such as drugs, industrial and agricultural chemicals), toxins (chemicals of biological origin such as mycotoxins and phycotoxins), and physical agents (such as heat and radiation); the investigation of the mechanisms by which these changes are induced; and the development of risk assessment and risk management policies based on such information. Toxicologic pathology primarily deals with the morphologic or structural effects of the toxicant and the mechanism by which this structural effect ismore » induced. This article highlights some of the problems that toxicologic pathologists may encounter in obtaining and interpreting pathology lesions. By alerting toxicologists to some of these issues, it is hoped that a better understanding of the use and limitations of toxicologic pathology data will occur.« less

Revealing Abrupt and Spontaneous Ruptures of Protein Native Structure under picoNewton Compressive Force Manipulation.

PubMed

Chowdhury, S Roy; Cao, Jin; He, Yufan; Lu, H Peter

2018-03-27

Manipulating protein conformations for exploring protein structure-function relationship has shown great promise. Although protein conformational changes under pulling force manipulation have been extensively studied, protein conformation changes under a compressive force have not been explored quantitatively. The latter is even more biologically significant and relevant in revealing protein functions in living cells associated with protein crowdedness, distribution fluctuations, and cell osmotic stress. Here we report our experimental observations on abrupt ruptures of protein native structures under compressive force, demonstrated and studied by single-molecule AFM-FRET spectroscopic nanoscopy. Our results show that the protein ruptures are abrupt and spontaneous events occurred when the compressive force reaches a threshold of 12-75 pN, a force amplitude accessible from thermal fluctuations in a living cell. The abrupt ruptures are sensitive to local environment, likely a general and important pathway of protein unfolding in living cells.

Analysis of angle effect on particle flocculation in branch flow

NASA Astrophysics Data System (ADS)

Prasad, Karthik; Fink, Kathryn; Liepmann, Dorian

2014-11-01

Hollow point microneedle drug delivery systems are known to be highly susceptible to blockage, owing to their very small structures. This problem has been especially noted when delivering suspended particle solutions, such as vaccines. Attempts to reduce particle flocculation in such devices through surface treatments of the particles have been largely unsuccessful. Furthermore, the particle clog only forms at the mouths of the microneedle structures, leaving the downstream walls clear. This implies that the sudden change in length scales alter the hydrodynamic interactions, creating the conditions for particle flocculation. However, while it is known that particle flocculation occurs, the physics behind the event are obscure. We utilize micro-PIV to observe how the occurrence and formation of particle flocculation changes in relation to the angle encountered by particle laden flow into microfluidic branch structures. The results offer the ability to optimize particle flocculation in MEMS devices, increasing device efficacy and longevity.

Perinatal stress and early life programming of lung structure and function

PubMed Central

Wright, Rosalind J.

2010-01-01

Exposure to environmental toxins during critical periods of prenatal and/or postnatal development may alter the normal course of lung morphogenesis and maturation, potentially resulting in changes that affect both structure and function of the respiratory system. Moreover, these early effects may persist into adult life magnifying the potential public health impact. Aberrant or excessive pro-inflammatory immune responses, occurring both locally and systemically, that result in inflammatory damage to the airway are a central determinant of lung structure-function changes throughout life. Disruption of neuroendocrine function in early development, specifically the hypothalamic-pituitary-adrenal (HPA) axis, may alter functional status of the immune system. Autonomic nervous system (ANS) function (sympathovagal imbalance) is another integral component of airway function and immunity in childhood. This overview discusses the evidence linking psychological factors to alterations in these interrelated physiological processes that may, in turn, influence childhood lung function and identifies gaps in our understanding. PMID:20080145

Ferromagnetic quantum criticality: New aspects from the phase diagram of LaCrGe3

NASA Astrophysics Data System (ADS)

Taufour, Valentin; Kaluarachchi, Udhara S.; Bud'ko, Sergey L.; Canfield, Paul C.

2018-05-01

Recent theoretical and experimental studies have shown that ferromagnetic quantum criticality is always avoided in clean systems. Two possibilities have been identified. In the first scenario, the ferromagnetic transition becomes of the first order at a tricritical point before being suppressed. A wing structure phase diagram is observed indicating the possibility of a new type of quantum critical point under magnetic field. In a second scenario, a transition to a modulated magnetic phase occurs. Our recent studies on the compound LaCrGe3 illustrate a third scenario where not only a new magnetic phase occurs, but also a change of order of the transition at a tricritical point leading to a wing-structure phase diagram. Careful experimental study of the phase diagram near the tricritical point also illustrates new rules near this type of point.

To what extent do structural changes in catalytic metal sites affect enzyme function?

PubMed

Valasatava, Yana; Rosato, Antonio; Furnham, Nicholas; Thornton, Janet M; Andreini, Claudia

2018-02-01

About half of known enzymatic reactions involve metals. Enzymes belonging to the same superfamily often evolve to catalyze different reactions on the same structural scaffold. The work presented here investigates how functional differentiation, within superfamilies that contain metalloenzymes, relates to structural changes at the catalytic metal site. In general, when the catalytic metal site is unchanged across the enzymes of a superfamily, the functional differentiation within the superfamily tends to be low and the mechanism conserved. Conversely, all types of structural changes in the metal binding site are observed for superfamilies with high functional differentiation. Overall, the catalytic role of the metal ions appears to be one of the most conserved features of the enzyme mechanism within metalloenzyme superfamilies. In particular, when the catalytic role of the metal ion does not involve a redox reaction (i.e. there is no exchange of electrons with the substrate), this role is almost always maintained even when the site undergoes significant structural changes. In these enzymes, functional diversification is most often associated with modifications in the surrounding protein matrix, which has changed so much that the enzyme chemistry is significantly altered. On the other hand, in more than 50% of the examples where the metal has a redox role in catalysis, changes at the metal site modify its catalytic role. Further, we find that there are no examples in our dataset where metal sites with a redox role are lost during evolution. In this paper we investigate how functional diversity within superfamilies of metalloenzymes relates to structural changes at the catalytic metal site. Evolution tends to strictly conserve the metal site. When changes occur, they do not modify the catalytic role of non-redox metals whereas they affect the role of redox-active metals. Copyright © 2017 The Authors. Published by Elsevier Inc. All rights reserved.

Thermodynamic effects of proline introduction on protein stability.

PubMed

Prajapati, Ravindra Singh; Das, Mili; Sreeramulu, Sridhar; Sirajuddin, Minhajuddin; Srinivasan, Sankaranarayanan; Krishnamurthy, Vaishnavi; Ranjani, Ranganathan; Ramakrishnan, C; Varadarajan, Raghavan

2007-02-01

The amino acid Pro is more rigid than other naturally occurring amino acids and, in proteins, lacks an amide hydrogen. To understand the structural and thermodynamic effects of Pro substitutions, it was introduced at 13 different positions in four different proteins, leucine-isoleucine-valine binding protein, maltose binding protein, ribose binding protein, and thioredoxin. Three of the maltose binding protein mutants were characterized by X-ray crystallography to confirm that no structural changes had occurred upon mutation. In the remaining cases, fluorescence and CD spectroscopy were used to show the absence of structural change. Stabilities of wild type and mutant proteins were characterized by chemical denaturation at neutral pH and by differential scanning calorimetry as a function of pH. The mutants did not show enhanced stability with respect to chemical denaturation at room temperature. However, 6 of the 13 single mutants showed a small but significant increase in the free energy of thermal unfolding in the range of 0.3-2.4 kcal/mol, 2 mutants showed no change, and 5 were destabilized. In five of the six cases, the stabilization was because of reduced entropy of unfolding. However, the magnitude of the reduction in entropy of unfolding was typically several fold larger than the theoretical estimate of -4 cal K(-1) mol(-1) derived from the relative areas in the Ramachandran map accessible to Pro and Ala residues, respectively. Two double mutants were constructed. In both cases, the effects of the single mutations on the free energy of thermal unfolding were nonadditive. Copyright 2006 Wiley-Liss, Inc.

Changes in biomolecular profile in a single nucleolus during cell fixation.

PubMed

Kuzmin, Andrey N; Pliss, Artem; Prasad, Paras N

2014-11-04

Fixation of biological sample is an essential technique applied in order to "freeze" in time the intracellular molecular content. However, fixation induces changes of the cellular molecular structure, which mask physiological distribution of biomolecules and bias interpretation of results. Accurate, sensitive, and comprehensive characterization of changes in biomolecular composition, occurring during fixation, is crucial for proper analysis of experimental data. Here we apply biomolecular component analysis for Raman spectra measured in the same nucleoli of HeLa cells before and after fixation by either formaldehyde solution or by chilled ethanol. It is found that fixation in formaldehyde does not strongly affect the Raman spectra of nucleolar biomolecular components, but may significantly decrease the nucleolar RNA concentration. At the same time, ethanol fixation leads to a proportional increase (up to 40%) in concentrations of nucleolar proteins and RNA, most likely due to cell shrinkage occurring in the presence of coagulant fixative. Ethanol fixation also triggers changes in composition of nucleolar proteome, as indicated by an overall reduction of the α-helical structure of proteins and increase in the concentration of proteins containing the β-sheet conformation. We conclude that cross-linking fixation is a more appropriate protocol for mapping of proteins in situ. At the same time, ethanol fixation is preferential for studies of RNA-containing macromolecules. We supplemented our quantitative Raman spectroscopic measurements with mapping of the protein and lipid macromolecular groups in live and fixed cells using coherent anti-Stokes Raman scattering nonlinear optical imaging.

Space flight and bone formation.

PubMed

Doty, St B

2004-12-01

Major physiological changes which occur during spaceflight include bone loss, muscle atrophy, cardiovascular and immune response alterations. When trying to determine the reason why bone loss occurs during spaceflight, one must remember that all these other changes in physiology and metabolism may also have impact on the skeletal system. For bone, however, the role of normal weight bearing is a major concern and we have found no adequate substitute for weight bearing which can prevent bone loss. During the study of this problem, we have learned a great deal about bone physiology and increased our knowledge about how normal bone is formed and maintained. Presently, we do not have adequate ground based models which can mimic the tissue loss that occurs in spaceflight but this condition closely resembles the bone loss seen with osteoporosis. Although a normal bone structure will respond to application of mechanical force and weight bearing by forming new bone, a weakened osteoporotic bone may have a tendency to fracture. The study of the skeletal system during weightless conditions will eventually produce preventative measures and form a basis for protecting the crew during long term space flight. The added benefit from these studies will be methods to treat bone loss conditions which occur here on earth.

Space flight and bone formation

NASA Technical Reports Server (NTRS)

Doty, St B.

2004-01-01

Major physiological changes which occur during spaceflight include bone loss, muscle atrophy, cardiovascular and immune response alterations. When trying to determine the reason why bone loss occurs during spaceflight, one must remember that all these other changes in physiology and metabolism may also have impact on the skeletal system. For bone, however, the role of normal weight bearing is a major concern and we have found no adequate substitute for weight bearing which can prevent bone loss. During the study of this problem, we have learned a great deal about bone physiology and increased our knowledge about how normal bone is formed and maintained. Presently, we do not have adequate ground based models which can mimic the tissue loss that occurs in spaceflight but this condition closely resembles the bone loss seen with osteoporosis. Although a normal bone structure will respond to application of mechanical force and weight bearing by forming new bone, a weakened osteoporotic bone may have a tendency to fracture. The study of the skeletal system during weightless conditions will eventually produce preventative measures and form a basis for protecting the crew during long term space flight. The added benefit from these studies will be methods to treat bone loss conditions which occur here on earth.

Temperature-dependent dynamics of bovine casein micelles in the range 10-40 °C.

PubMed

Liu, Dylan Z; Weeks, Michael G; Dunstan, David E; Martin, Gregory J O

2013-12-15

Milk is a complex colloidal system that responds to changes in temperature imposed during processing. Whilst much has been learned about the effects of temperature on milk, little is known about the dynamic response of casein micelles to changes in temperature. In this study, a comprehensive physico-chemical study of casein micelles in skim milk was performed between 10 and 40 °C. When fully equilibrated, the amount of soluble casein, soluble calcium and the pH of skim milk all decreased as a function of increasing temperature, whilst the hydration and volume fraction of the casein micelles decreased. The effect of temperature on casein micelle size, as determined by dynamic light scattering and differential centrifugation, was less straightforward. Real-time measurements of turbidity and pH were used to investigate the dynamics of the system during warming and cooling of milk in the range 10-40 °C. Changes in pH are indicative of changes to the mineral system and the turbidity is a measure of alterations to the casein micelles. The pH and turbidity showed that alterations to both the casein micelles and the mineral system occurred very rapidly on warming. However, whilst mineral re-equilibration occurred very rapidly on cooling, changes to the casein micelle structure continued after 40 min of measurement, returning to equilibrium after 16 h equilibration. Casein micelle structure and the mineral system of milk were both dependent on temperature in the range 10-40 °C. The dynamic response of the mineral system to changes in temperature appeared almost instantaneous whereas equilibration of casein was considerably slower, particularly upon cooling. Copyright © 2013 Elsevier Ltd. All rights reserved.