Fm Values Research Articles

Unraveling of cross talk between Ca(2+) and ROS regulating enzymes in Anabaena 7120 and ntcA mutant.

In order to understand a cross talk between Ca(2+) and ROS regulating enzymes and the possible involvement of ntcA gene, Anabaena sp. PCC 7120 and its derivative ntcA mutant grown in varied levels of calcium chloride (0, 1, 10, and 100 mM) have been investigated. Scanning Electron Microscopy showed abnormal structure formation at high calcium concentration (100 mM) both in wild type and mutant. Fv /Fm values suggested that 100 mM calcium concentration was detrimental for photosynthetic apparatus. SOD, catalase, APX, GR, and peroxidase activity were found to be maximum for 100 mM and minimum for 1 mM of exogenously supplied calcium salt. NADPH contents were higher for wild type than mutant. RAPD-PCR and SDS-PAGE analysis revealed a difference in DNA as well as proteome pattern with changes in calcium chloride regime. Prominent bands of approximately 70, 33, 21, and 14 kDa expressed in the wild type served as the marker polypeptide bands under calcium supplementation. Results suggest that higher levels of calcium ion disturb the cellular homeostasis generating ROS, thereby inducing enhanced levels of antioxidative enzymes. Further, data also suggests possible involvement of ntcA gene in cross talk between calcium ion and ROS regulating enzymes.

Extracted and depolymerized alginates from brown algae Sargassum vulgare of Lebanese origin: chemical, rheological, and antioxidant properties

Purified sodium alginate (PS alginate) was isolated from the brown seaweed Sargassum vulgare collected from the Lebanese Mediterranean coast and then depolymerized into homopolymeric polyguluronate (PolyG) and polymannuronate (PolyM) blocks by controlled acid hydrolysis. These fractions of PS alginate issued from S. vulgare were characterized in terms of composition and structure by SEC, elemental analysis, FTIR and 1H and 13C NMR spectroscopy. An alginate with a low content of protein (<0.62 %) and a molecular weight of 110 200 g mol-1 was identified as sole polysaccharide. Depolymerized PS alginate fractions, PolyG (32.6 %) and PolyM (22.3 %), were found to have close molecular weights, of 7500 and 6900 g mol-1, respectively. From NMR analysis, values of F G, F M, M/G ratio, F GG, F MM, and F GM (or F MG) blocks were determined and compared with those of alginates from S. vulgare of Brazilian origin and other Sargassum species. Our PS alginate appeared different from the Brazilian S. vulgare alginate, with a lower M/G ratio (0.785 instead of 1.27), a predominance of the G blocks (F G and F GG > 0.5) instead of the M blocks, and it showed more similarity to the composition of some alginates extracted from other species of Sargassum. High G or M contents (≥80 %) were measured from PolyG and PolyM blocks, respectively. The viscosity of the PS alginate and its fractions PolyG and PolyM was determined. PS alginate from S. vulgare of Lebanese origin showed a Newtonian flow behavior for concentration lower than 0.5 % in 0.1 M NaCl solution, while a shear-thinning pseudoplastic behavior is observed for concentration range between 0.75 and 10 %. Also, storage (G′) and loss (G″) moduli were studied for two concentrations of PS alginate solutions (5 and 10 %). Antioxidant properties of the non-depolymerized and depolymerized alginates were evaluated by determining the scavenging ability of the stable radical DPPH (2,2-diphenyl-1 picrylhydrazyl). Clearly, the results demonstrated differences in radical scavenging efficacy between PolyG and PolyM fractions. The higher hydroxyl radical scavenging activity was observed for the PolyG fractions (~92 % at 2 mg mL-1) and this activity was comparable with those of standard antioxidants. These PolyG fractions could be valuable in foods or pharmaceutical products as alternatives to synthetic antioxidants.

The Thermotolerance and Repair Mechanism of Photosystem in Alpine Plant Arabis paniculata (Cruciferae)

The heat stress associated with extremely and moderately high temperatures affects a series of physiologi cal activities in plants especially photosynthesis. Howeverꎬ it is proposed that the plants use different photosynthetic strategy to deal with extreme and moderate heat stresses. Most reports focus on the cold tolerant ability but thermotol erance of alpine plants. In the present studyꎬ we used the alpine plant Arabis paniculata as a model alpine plant to examine whether its capacity for heat tolerance is exhibited under moderate heat stress andꎬ if soꎬ how this capacity is related to differences in its photosynthesis compared with that of its close relative Arabidopsis thaliana. We found that A􀆰 paniculata had high photochemical efficiency at a moderately high temperature and a rapid reversible recovery processꎬ which reflected substantial heat tolerance. Despite no obvious difference in F0 between the two speciesꎬ the higher Fm values after heat treatment and recovery in A􀆰 paniculata than in A􀆰 thaliana facilitated the rapid photo chemical recovery. A rapid and transient increase in non photochemical quenching after moderate heat stress provid ed timely protection for PSII against the damage caused by heat and light. The rapid accumulation of heat shock pro tein 101 upon exposure to moderately high temperatures might initiate photochemical repair. Finallyꎬ the high rate of survival of A􀆰 paniculata after severe heat treatment attested to the substantial heat tolerance of its photosynthetic ma chinery under moderate stress. Our results indicated that a highly heat tolerant photosystem and effective photochemi 植 物 分 类 与 资 源 学 报 2015ꎬ 37 (1): 46~54 Plant Diversity and Resources DOI: 10.7677 / ynzwyj201514037 ∗ ∗ ∗ Funding: NSFC (31300251) and XiBuZhiGuang Project Author for correspondenceꎻ E mail: weiqili@mail􀆰 kib􀆰 ac􀆰 cn Received date: 2014-03-12ꎬ Accepted date: 2014-06-11 作者简介: 唐婷 (1987-) 女ꎬ 博士ꎬ 主要从事植物逆境分子生理学研究ꎮ E mail: tangtingnkjdx@163􀆰 com cal repair mechanism contribute to the capacity of A􀆰 paniculata to tolerate moderate heat stress.

Ultra-Small Graphitization Reactors for Ultra-Microscale 14C Analysis at the National Ocean Sciences Accelerator Mass Spectrometry (NOSAMS) Facility

In response to the increasing demand for 14C analysis of samples containing less than 25 μg C, ultra-small graphitization reactors with an internal volume of ∼0.8 mL were developed at NOSAMS. For samples containing 6 to 25 μg C, these reactors convert CO2 to graphitic carbon in approximately 30 min. Although we continue to refine reaction conditions to improve yield, the reactors produce graphite targets that are successfully measured by AMS. Graphite targets produced with the ultra-small reactors are measured by using the Cs sputter source on the CFAMS instrument at NOSAMS where beam current was proportional to sample mass. We investigated the contribution of blank carbon from the ultra-small reactors and estimate it to be 0.3 ± 0.1 μg C with an Fm value of 0.43 ± 0.3. We also describe equations for blank correction and propagation of error associated with this correction. With a few exceptions for samples in the range of 6 to 7 μg C, we show that corrected Fm values agree with expected Fm values within uncertainty for samples containing 6–100 μg C.

Collective Calculation of Actual Values of Non-Photochemical Quenching from Their Apparent Values after Chloroplast Movement and Photoinhibition

Chlorophyll fluorescence parameters such as Fv/Fm, NPQ and ΦII (YII) are widely used to estimate the fitness and photosynthetic activity of plant leaves and non-photochemical dissipation of excessive excitation energy in photosystem II. The effect of chloroplast movement on these fluorescence parameters reduces the accuracy of estimations of the size of de-excitation processes, but there is no method to calculate correct parameters from altered (fluctuated) parameters. Chloroplast movement was recently identified as the “middle” kinetic component of NPQ. In this paper, we devised a complex but reasonable mathematical method to remove the effect of chloroplast movement on fluorescence parameters, based on our previously reported fluorescence theory. The fraction of “S fluctuation” (designated as σ) was estimated from fluorescence observations and used to calculate the non-fluctuated Fs and F′m. fluorescence yields. From the σ values, the fractional change of light absorbance by a leaf caused by chloroplast movement was estimated at 70% - 100%, which varied according to the experimental conditions and plant species. The effect of photoinhibition on fluorescence parameters was also examined in this paper. The photochemical and non-photochemical de-excitation sizes during photoinhibition (measured by the parameters qPI and qSlow) changed on a single regression line. Using this correlation, qPI and qSlow can be predicted from Fv/Fm, and the non-fluctuated Fm and Fo values can be estimated from the fluctuated F″m and F″o values.

开顶式气室内外冬小麦光合特性差异比较研究

PDF HTML阅读 XML下载 导出引用 引用提醒 开顶式气室内外冬小麦光合特性差异比较 DOI: 10.5846/stxb201402200299 作者: 作者单位: 江西省气象科学研究所,江西省农业气象试验站,江苏省气象灾害重点试验室,江苏省气象灾害重点试验室,云南省气候中心,气象防灾减灾湖南省重点实验室 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金(41075114) Comparative of the photosynthetic characteristics of winter wheat grown inside and outside open-top chambers Author: Affiliation: Eteorological Research Institute of Jiangxi Province,Agro-meteorological Experiment Station of Jiangxi Province,,Jiangsu Key Laboratory of Meteorological Disaster,,Key Lab of Hunan Province for Meteorological Disaster Prevention and Mitigation Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:为探明开顶式气室(OTC)内外冬小麦光合特性的差异,测定了OTC内(T1处理组,冬小麦整个生育期生长在OTC内)和OTC外(T2处理组,大田自然环境组)冬小麦(扬麦16)不同生育期的气体交换参数、光合色素含量和叶绿素荧光参数。结果表明,T1处理的净光合速率Pn、气孔导度Gs、胞间CO2浓度Ci、最大光合速率Pm和半饱和光强Ik大部分生育期均大于T2;灌浆之前T1的表观量子效率AQY较高,蒸腾速率Tr和暗呼吸速率Rd较低,灌浆之后则出现逆转。大部分生育期T1处理叶绿素和类胡萝卜素含量均显著大于T2。T1处理的初始荧光Fo和最大荧光Fm均大于T2,而两者最大光量子产量Fv/Fm大部分生育期无显著差异,孕穗期和扬花期T1处理光化学淬灭系数qP显著低于T2。T1和T2处理PSⅡ的实际光化学量子效率Y(II)大部分生育期无显著差异,但灌浆期以后T1的非光化学淬灭系数NPQ和PSⅡ处调节性能量耗散的量子产量Y(NPQ)显著大于T2,而PSⅡ处非调节性能量耗散的量子产量Y(NO)显著低于T2。由此可见,OTC内冬小麦的气体交换能力和光响应能力均优于OTC外,光合色素含量也更高;OTC内外冬小麦内禀光能转换效率和实际光化学量子效率相当,但OTC内冬小麦过剩光能向调节性热耗散分配的比例较高而向非调节性热耗散分配的比例较低,其光保护能力更强,光能分配也更加合理。 Abstract:The open-top chamber (OTC) is an important device used to study the impact of climate change on ecosystems. These chambers have been widely used in climate change simulation and pollution ecology research. Compared to the conventional closed artificial climate chamber or the newly developed free-air concentration enrichment (FACE) method, the OTC creates a microclimate that is more similar to the atmospheric environment. Moreover, its test gas concentration control is more precise, and its construction and operating costs are lower. Our research results indicated that microclimatic elements inside and outside the OTC are different. Although much research has been carried out on microclimatic elements inside and outside the OTC, and improvements have been made based on these research results, there are only a few reports on the growth and photosynthetic response of plants to these microclimatic differences.This study aimed to evaluate the photosynthetic response of winter wheat (Triticum aestivum L.) grown inside (T1) and outside (T2) an OTC, using the plants of a modern cultivar, 'YangMai16.’ Gas exchange, photosynthetic pigment content, and chlorophyll fluorescence parameters were evaluated. The test field was located at the Agricultural Meteorological Experiment Station of Nanjing University of Information Science and Technology, China (32°03'N, 118°51'E). The seeds were sown on November 5, 2009, by drilling, with a seeding rate of 220.5 kg/hm2, and plants were harvested on May 31, 2010. The daily mean temperature and relative humidity inside the OTC used in our experiments were 8.9% and 3.3% higher, respectively, than those of the atmospheric environment; however, total radiation was 20.4% lower. The differences in microclimatic elements inside and outside the OTC used in this study were similar to those recorded by other groups.Our results indicated that the net photosynthetic rate (Pn), stomatal conductance (Gs), intercellular CO2 concentration (Ci), max photo-synthetic rate (Pm), and half-saturation light intensity (Ik ) of T1 were significantly higher than those of T2 (P<0.05). Before the filling stage, the apparent quantum yield (AQY) of T1 was significantly higher than that of T2, whereas transpiration rate (Tr) and dark respiratory rate (Rd) were significantly lower (P<0.05). After the filling stage, the results reversed. The chlorophyll and carotenoid contents of T1 were significantly higher than those of T2 during most of the growth stages P<0.05). The basic fluorescence yield (Fo) and dark-adapted maximum fluorescence yield (Fm) values of T1 were higher than those of T2, but there was no difference in the maximum photochemical capacity of PSⅡ (photosystem II) (Fv/Fm) between T1 and T2 during most of the growth stages. In the booting and flowering stages, the photochemical quenching coefficient (qP) of T1 was significantly lower than that of T2 (P<0.05). There was no difference in the quantum yield of photochemical energy conversion in PSⅡ [Y(II)]of T1 and T2 during most of the growth stages. The non-photochemical quenching coefficient (NPQ) and quantum yield of regulated non-photochemical energy loss in PSⅡ [Y(NPQ)] of T1 were significantly higher than those of T2 after the filling stage (P<0.05), whereas the quantum yield of non-regulated non-photochemical energy loss in PSⅡ [Y(NO)] was lower. Our results indicate that the gas exchange capability, light response capability, and photosynthetic pigment content of winter wheat grown inside the OTC were higher than those of wheat grown outside. There were no differences in the maximum photochemical capacity and quantum yield of photochemical energy conversion in the PSⅡ of winter wheat grown inside and outside the OTC. In contrast, the fraction of energy dissipated as heat via the regulated photo-protective NPQ mechanism was higher, while the fraction that was passively dissipated in the form of heat and fluorescence was lower, for winter wheat grown inside the OTC. Photo-protection of the photosynthetic apparatus from excess energy in PSⅡ was also better in the winter wheat grown inside the OTC. Our results are expected to help improve OTCs, including the evaluation of data from controversial ecology projects and the application of research knowledge obtained from OTCs to field conditions. 参考文献 相似文献 引证文献

How does magnetization transfer influence mcDESPOT results?

A steady-state approach that was termed multicomponent driven equilibrium single pulse observation of T1 and T2 (mcDESPOT) has recently been proposed for myelin water fraction (fM) mapping in brain development and demyelinating diseases. However, fMs estimated by mcDESPOT are significantly higher than myelin water fraction derived from multiecho spin echo T2-decay curve approaches. Magnetization transfer (MT), enhanced by the use of short, relatively high amplitude radiofrequency (RF) pulses in mcDESPOT, may artifactually influence fM maps. Our goal was to investigate the role of MT in mcDESPOT. mcDESPOT data was collected twice from three healthy volunteers using short RF pulses with higher MT effect and long RF pulses with lower MT effect. MR parameters from 11 white and gray regions were compared using a paired student t-test. Whole slice difference images were also compared. MT effects had a substantial influence on the signal generated by the balanced steady-state free procession sequences used in mcDESPOT. However, these MT effects were not clearly evident in the fM values determined by the conventional two-pool mcDESPOT analysis. The signal generated from mcDESPOT is sensitive to MT, but the extracted myelin water fractions are relatively insensitive to changes of MT.

Effects of NaCl Stress on Chlorophyll Content and Chlorophyll Fluorescence in Sunflower (Helianthus annuus L.) Lines

Tuzluluk, fotosentez, klorofil, floresans ve bunların bileşenleri üzerinde olumsuz etkileri olan önemli abiyotik streslerden biridir. Bu çalışmada, 12 adet ayçiçeği (H. annuus) hattının klorofil ve floresansı üzerine tuzluluğun (0, 100 ve 200 mM NaCl) etkisi, hidrofonik sistemde bir aylık dönem boyunca araştırılmıştır. Sonuçlar, tuz stresinin klorofil içeriğini ilk üç hafta içinde arttırdığını, fakat son hafta hafifçe düşürdüğünü göstermektedir. Bununla birlikte, stres uygulanmayan bitkilerde klorofil içeriği, dört hafta boyunca artmıştır. Araştırma sonuçları, tuz stresinin sadece uzun vadede klorofil içeriğini olumsuz etkilediğini, ancak kısa vadede tuzluluğun ikincil etkilerle klorofil içeriğini artırdığını göstermektedir. 12 ayçiçeği hattı arasında, en yüksek klorofil içeriği artışı, hem duyarlı hem de tolerant hatlarda gözlemlenmiştir. Ayrıca, sonuçlar, aşırı stresin Fv/Fm oranını 1. haftadan 3. haftaya kadar arttırdığını, fakat 4. haftada bu oranın azaldığını göstermektedir. İkinci haftadan sonra strese maruz bırakılmış bitkilerde, kontrol bitkilerine oranla hem F hem de Fm değerlerinde artış gözlenmiştir. Fdeğeri Fm değerine oranla daha fazla artmıştır, bu da Fv/Fm oranında iyileşmeye neden olmuştur. Bu üst (genç) ayçiçeği yaprakların uzun süreli stres altında daha aktif kalmaya adapte olması, bitkilerin uzun dönem stres koşullarında hayatta kalmasını sağlamaktadır.

Community dynamics and physiology of Symbiodinium spp. before, during, and after a coral bleaching event

Community dynamics and physiology of Symbiodinium associated with Orbicella ( = Montastraea) faveolata were examined before, during, and after a thermally induced coral bleaching event in Puerto Morelos, Mexico. We combined microsampling molecular genotyping with in situ pulse‐amplitude modulated fluorometry to correlate colony variability of Symbiodinium population identities and the phenomena of partial coral bleaching. Pigmented nonbleached portions of O. ( = M.) faveolata were compared with bleached portions of the same colony. During bleaching, maximum quantum yield of photosystem II (PSII; Fv : Fm) was significantly lower and highly variable (range 0.110 to 0.680) compared with previous summers in which coral bleaching was absent (range 0.516 to 0.661) and recovery (range 0.480 to 0.716). Differential susceptibility to environmental perturbation of Fv : Fm corresponded to distinct genetic identities of Symbiodinium. Analysis of ribosomal deoxyribonucleic acid (rDNA) internal transcribed spacer 2 (ITS2) revealed regions of the coral colonies that had phylotype A3 prior to bleaching were more resistant to the bleaching perturbation than adjacent bleaching‐prone patches that harbored phylotypes B17 and C7. During environmental perturbation, regions of the colonies containing predominantly Symbiodinium phylotypes A3 or D1a retained significantly higher Fv : Fm values than adjacent regions with phylotypes B17 and C7. Following bleaching, rapid recovery of symbiotic algal densities greatly exceeded normal seasonal oscillations. During recovery we document shifts in Symbiodinium populations and increase prevalence of Symbiodinium types A3 and D1a, phylotypes known to have enhanced thermal tolerances. Thermal tolerance of Symbiodinium spp. influences the changes of coral—Symbiodinium communities during disturbance events and the dynamics of coral—Symbiodinium repopulation.

The effect of high UV-B dosage on apple fruit photosystems at different fruit maturity stages

Apple fruits (Malus domestica Borkh) of the cultivars Granny Smith, Fuji, Cripp's Pink, Braeburn, Golden Delicious and Topred were harvested at three stages during fruit growth. Previously sun-exposed peels of the apple fruits were exposed to a high ultraviolet radiation-B (UV-B) dosage for 150min at each stage. In a second experiment mature ‘Granny Smith’, ‘Fuji’ and ‘Cripps’ Pink’ fruits previously sun or shade exposed were also exposed to the UV-B stress. The effect of UV-B stress on fruits photosystem components was assessed by measuring the change in maximum light use efficiency and light reflection of fruit peels. UV-B induced pigment changes were analysed for ‘Braeburn’, ‘Fuji’ and ‘Cripps’ Pink’. The UV-B stress did not cause photoinhibition to any of the cultivars during fruit growth. However, UV-B stress did cause photoinhibition to previously shaded mature ‘Granny Smith’ and ‘Fuji’ fruits. Previously shaded ‘Cripps’ Pink’ fruits were conversely as insensitive to UV-B stress as the previously sun exposed fruits. ‘Braeburn’ showed no major pigment response to UV-B stress throughout the season. However, in ‘Fuji’ and ‘Cripps’ Pink’ fruits, total phenolic content increased at mid-season and maturity, while decreasing at the juvenile stage. All cultivars appear to have a stronger light reflection response to UV-B stress at the juvenile stage than later in the season. Photosystem II (PS II) units (as indicated by the Fm values) and the oxygen evolving complex activity (as indicated by the Fv values) in all the cultivars decreased with fruit maturity. Shaded ‘Cripps’ Pink’ fruits seemed to use the xanthophyll cycle as a photoprotective mechanism after UV-B stress. Photosynthetic systems in sun-exposed, therefore acclimatised, apple fruit peel are possibly not sensitive to UV-B stress in isolation. The fruits are probably well screened against UV light. Conversely, shaded peel may be less adapted and therefore more sensitive to high UV-B exposure. The light reflection response to UV-B stress at the juvenile stage could be due to the reduced phenolic content after stress and the presence of more PS II units at this stage compared to the mature stage.

Nutrient regimes control phytoplankton ecophysiology in the South Atlantic

Abstract. Fast Repetition Rate fluorometry (FRRf) measurements of phytoplankton photophysiology from an across-basin South Atlantic cruise (as part of the GEOTRACES programme) characterised two dominant ecophysiological regimes which were interpreted on the basis of nutrient limitation. South of the South Subtropical Convergence (SSTC) in the northern sub-Antarctic sector of the Antarctic Circumpolar Current (ACC) in the Eastern Atlantic Basin, waters are characterised by elevated chlorophyll concentrations, a dominance by larger phytoplankton cells, and low apparent photochemical efficiency (Fv / Fm). Shipboard 24 h iron (Fe) addition incubation experiments confirmed that Fe stress was primarily responsible for the low Fv / Fm, with Fe addition to these waters, either within the artificial bottle additions or naturally occurring downstream enrichment from Gough Island, significantly increasing Fv / Fm values. To the north of the SSTC at the southern boundary of the South Atlantic Gyre, phytoplankton are characterised by high values of Fv / Fm which, coupled with the low macronutrient concentrations and increased presence of picocyanobacteria, are interpreted as conditions of Fe replete, balanced macronutrient-limited growth. Spatial correlation was found between Fv / Fm and Fe:nitrate ratios, supporting the suggestion that the relative supply ratios of these two nutrients can control patterns of limitation and consequently the ecophysiology of phytoplankton in subtropical gyre and ACC regimes.

24-weeks Pilates-aerobic and educative training to improve body fat mass in elderly Serbian women

BackgroundThe purpose of this study was to examine the differences in anthropometric measurements using an aerobic and Pilates exercise program which lasted 24 weeks.MethodThis was a clinical intervention study of 303 women over the age of 60 living in Novi Sad, Serbia. Changes in body mass index and skinfold thickness were estimated through height, weight, and anthropometric measurements. The program comprised Pilates exercises for upper- and lower-body strength, agility, and aerobic capacity.ResultsFat mass (FM) improved significantly (pre-test, 32.89%, 8.65; post-test, 28.25%, 6.58; P<0.01). Bone diameters and muscle perimeters showed no significant changes pre- and post-test (P>0.05), but there was a higher correlation between FM (%) and waist–hip ratio (rho, 0.80; P<0.01).ConclusionA mixed program of aerobics and Pilates, controls and improves baseline muscle mass and decreases FM values, without causing deterioration during practice and follow-up exercises.

Bulk and Thin Film Morphological Behavior of Broad Dispersity Poly(styrene-b-methyl methacrylate) Diblock Copolymers

We describe the morphological implications of broad molecular weight dispersity on the bulk and thin film self-assembly behavior of seven model poly(styrene-block-methyl methacrylate) (SM) diblock copolymers. Derived from sequential nitroxide-mediated polymerizations, these unimodal diblock copolymers are comprised of narrow dispersity S blocks (Đ ≤ 1.14) and broad dispersity M blocks (Đ ∼ 1.7) with total molecular weights Mn,total = 29.2–42.9 kg/mol and M volume fractions fM = 0.35–0.63. Small-angle X-ray scattering (SAXS) and transmission electron microscopy (TEM) analyses demonstrate that these diblock copolymers microphase separate into lamellar and cylindrical morphologies with substantially larger microdomain spacings at lower overall molecular weights as compared to their narrow dispersity analogues. The observed microphase-separated melt stabilization is also accompanied by a substantial shift in the lamellar phase composition window to higher values of fM. In thin films, these polydisperse copoly...

Air–particle abrasion on zirconia ceramic using different protocols: Effects on biaxial flexural strength after cyclic loading, phase transformation and surface topography

This study evaluated the effect of different air–particle abrasion protocols on the biaxial flexural strength and structural stability of zirconia ceramics. Zirconia ceramic specimens (ISO 6872) (Lava, 3M ESPE) were obtained (N=336). The specimens (N=118, n=20 per group) were randomly assigned to one of the air-abrasion protocols: Gr1: Control (as-sintered); Gr2: 50 µm Al2O3 (2.5 bar); Gr3: 50 µm Al2O3 (3.5 bar); Gr4: 110 µm Al2O3(2.5 bar); Gr5: 110 µm Al2O3 (3.5 bar); Gr6: 30 µm SiO2 (2.5 bar) (CoJet); Gr7: 30 µm SiO2(3.5 bar); Gr8: 110 µm SiO2 (2.5 bar) (Rocatec Plus); and Gr9: 110 µm SiO2 (3.5 bar) (duration: 20 s, distance: 10 mm). While half of the specimens were tested immediately, the other half was subjected to cyclic loading in water (100,000 cycles; 50 N, 4 Hz, 37 °°C) prior to biaxial flexural strength test (ISO 6872). Phase transformation (t→m), relative amount of transformed monoclinic zirconia (FM), transformed zone depth (TZD) and surface roughness were measured. Particle type (p=0.2746), pressure (p=0.5084) and cyclic loading (p=0.1610) did not influence the flexural strength. Except for the air-abraded group with 110 µm Al2O3 at 3.5 bar, all air-abrasion protocols increased the biaxial flexural strength (MPa) (Controlnon-aged: 1030±153, Controlaged: 1138±138; Experimentalnon-aged: 1307±184–1554±124; Experimentalaged: 1308±118–1451±135) in both non-aged and aged conditions, respectively. Surface roughness (Ra) was the highest with 110 µm Al2O3(0.84 µm. FM values ranged from 0% to 27.21%, higher value for the Rocatec Plus (110 µm SiO2) and 110 µm Al2O3 groups at 3.5 bar pressure. TZD ranged between 0 and 1.43 µm, with the highest values for Rocatec Plus and 110 µm Al2O3 groups at 3.5 bar pressure.

Studies on soil to grass transfer factor (Fv) and grass to milk transfer coefficient (Fm) for cesium in Kaiga region

Detailed studies were carried out to establish site-specific soil to grass transfer factors (Fv) and grass to cow milk transfer coefficients (Fm) for radioactive cesium (137Cs) and stable cesium (Cs) for Kaiga region, where a nuclear power station has been in operation for more than 10 years. The study included adopted cows, cows of local farmers, and cows from the dairy farm. A grass field was developed specifically for the study and 2 local breed cows were adopted and allowed to graze in this grass field. The soil and grass samples were collected regularly from this field and analyzed for the concentrations of 137Cs and stable Cs to evaluate the soil to grass Fv values. The milk samples from the adopted cows were analyzed for the 137Cs and stable Cs concentrations to evaluate Fm values. For comparison, studies were also carried out in dominant grazing areas in different villages around the nuclear power plant and the cows of local farmers which graze in these areas were identified and milk samples were collected and analyzed regularly. The geometric mean values of Fv were found to be 1.1 × 10−1 and 1.8 × 10−1 for 137Cs and stable Cs, respectively. The Fm of 137Cs had geometric mean values of 1.9 × 10−2 d L−1 and 4.6 × 10−2 d L−1, respectively, for adopted Cows 1 and 2; 1.7 × 10−2 d L−1 for the cows of local farmers, and 4.0 × 10−3 d L−1 for the dairy farm cows. The geometric mean values of Fm for stable Cs were similar to those of 137Cs. The Fm value for the dairy farm cows was an order of magnitude lower than those for local breed cows. The Fm values observed for the local breed cows were also an order of magnitude higher when compared to the many values reported in the literature and in the IAEA publication. Possible reasons for this higher Fm values were identified. The correlation between Fv and Fm values for 137Cs and stable Cs and their dependence on the potassium content (40K and stable K) in the soil and grass were also studied. In order to estimate the ingestion dose accurate data of the dietary habits of the population was necessary and this data was collected through a well planned demographic survey. The internal doses to a child due to the ingestion of 137Cs along with the milk of the local cows and from the dairy farm were found to be 0.29 μSv y−1 and 0.04 μSv y−1,while that to an adult were 0.39 μSv y−1 and 0.05 μSv y−1, respectively.

CHLOROPHYLL FLUORESCENCE AS AN INDICATOR OF WHEN TO HARVEST MANGO 'COGSHALL' FRUIT ACCORDING TO THE MARKET (EXPORT OR DOMESTIC)

A non-destructive technique to predict harvest date of mango according to the market (domestic or export), combined with the traditional criterion was presented. Changes in chlorophyll fluorescence of mango and in indicators of maturation were evaluate at different maturity stages. Maximal (Fm), minimal (Fo), variable (Fv), variable to maximal ratio (Fv/Fm) chlorophyll fluorescence, fruit size, density, total sugar content in flesh, and respiration rate were evaluated at three harvest dates (i.e. 106, 120 and 132 days after full bloom, the latest corresponding to the traditional date of harvest, according to change in fruit appearance). No difference in Fv/Fm value was found, regardless of the harvest date, while the three maturity stages were differentiated using Fm, Fo, and Fv values. These chlorophyll fluorescence parameters declined with the maturation process. The respiration rate increased with harvest date, especially for fruit from the latest harvest in which the climacteric crisis has begun. Total sugar content and fruit density increased as chlorophyll fluorescence parameters decreased. Chlorophyll fluorescence appeared to be a helpful, non-destructive technique to predict harvest date before visible changes in fruit appearance, especially for export market. Whereas, the traditional criteria could be kept as an indicator to harvest 'Cogshall' mango for domestic market, in which it is not necessary to store fruit. (Resume d'auteur)

D‐2‐hydroxyglutarate metabolism is linked to photorespiration in the shm1‐1 mutant

The Arabidopsis mutant shm1-1 is defective in mitochondrial serine hydroxymethyltransferase 1 activity and displays a lethal photorespiratory phenotype at ambient CO2 concentration but grows normally at high CO2 . After transferring high CO2 -grown shm1-1 plants to ambient CO2 , the younger leaves remain photosynthetically active while developed leaves display increased yellowing and decreased FV /FM values. Metabolite analysis of plants transferred from high CO2 to ambient air indicates a massive light-dependent (photorespiratory) accumulation of glycine, 2-oxoglutarate (2OG) and D-2-hydroxyglutarate (D-2HG). Amino acid markers of senescence accumulated in ambient air in wild-type and shm1-1 plants maintained in darkness and also build up in shm1-1 in the light. This, together with an enhanced transcription of the senescence marker SAG12 in shm1-1, suggests the initiation of senescence in shm1-1 under photorespiratory conditions. Mitochondrial D-2HG dehydrogenase (D-2HGDH) converts D-2HG into 2OG. In vitro studies indicate that 2OG exerts competitive inhibition on D-2HGDH with a Ki of 1.96 mm. 2OG is therefore a suitable candidate as inhibitor of the in vivo D-2HGDH activity, as 2OG is produced and accumulates in mitochondria. Inhibition of the D-2HGDH by 2OG is likely a mechanism by which D-2HG accumulates in shm1-1, however it cannot be ruled out that D-2HG may also accumulate due to an active senescence programme that is initiated in these plants after transfer to photorespiratory conditions. Thus, a novel interaction of the photorespiratory pathway with cellular processes involving D-2HG has been identified.

Formation of hybrid films from perylenediimide-labeled core–shell silica–polymer nanoparticles

We prepared water-dispersible core–shell nanoparticles with a perylenediimide-labeled silica core and a poly(butyl methacrylate) shell, for application in photoactive high performance coatings. Films cast from water dispersions of the core–shell nanoparticles are flexible and transparent, featuring homogeneously dispersed silica nanoparticles, and exhibiting fluorescence under appropriate excitation. We characterized the film formation process using nanoparticles where the polymer shell has been labeled with either a non-fluorescent N-benzophenone derivative (NBen) or a fluorescent phenanthrene derivative (PheBMA). We used Förster resonance energy transfer (FRET) from PheBMA to NBen to follow the interparticle interdiffusion of the polymer anchored to the silica surface that occurs after the dried dispersions are annealing above the glass transition temperature of the polymer. By calculating the evolution of the FRET quantum efficiency with annealing time, we could estimate the approximate fraction of mixing (fm) between polymer from neighbor particles, and from this, the apparent diffusion coefficients (Dapp) for this process. For long annealing times, the limiting values of fm are slightly lower than for films of pure PBMA particles at similar temperatures (go up to 80% of total possible mixing). The corresponding diffusion coefficients are also very similar to those reported for films of pure PBMA, indicating that the fact that the polymer chains are anchored to the silica particles does not significantly hinder the diffusion process during the initial part of the mixing process. From the temperature dependence of the diffusion coefficients, we found an effective activation energy for diffusion of Ea=38kcal/mol, very similar to the value obtained for particles of the same polymer without the silica core. With these results, we show that, although the polymer is grafted to the silica surface, polymer interdiffusion during film formation is not significantly decreased by the silica core. This explains the excellent properties of the photoactive high performance coatings formed from the core–shell nanoparticles.

Influência do posicionamento do ciclista na sobrecarga mecânica da coluna cervical, calculada pela técnica da dinâmica inversa

This study examined the influence of the subject position on the bicycle during pedaling, on the mechanical overload in the cervical spine. Nine subjects were evaluated during the test on a racing bicycle coupled to a cyclesimulator. The protocol consisted in pedaling in four different postures (erect, rest, intermediate and attack), with video filming in the sagittal plane. Images were digitized using the software DVideow, which enabled the calculation of kinematic variables, later inserted into the biomechanics model to calculate the muscle (FM) and joint (FA) forces. When the subjects changed from erect to rest posture, rest to intermediate posture, intermediate to attack posture, the mean and the maximum values of FM and FA have increased (p&lt;0.05). Therefore, there was a significant increase in the FM and FA forces as the cervical spine became more extended and projected forward.

Body composition in subjects with anorexia nervosa: bioelectrical impedance analysis and dual-energy X-ray absorptiometry.

To evaluate the applicability and validity of bioelectrical impedance analysis (BIA) compared with dual-energy X-ray absorptiometry (DXA) in a population of girls with restrictive anorexia nervosa (AN). A total of 30 girls (11-19 years old) with AN were enrolled. DXA and BIA (BIA software and the Deurenberg equations) were used to estimate the body composition. The correlation between the methods was assessed by Pearson's correlation coefficient and the Bland-Altman method. The mean FFM estimates were 33.2 kg (BIA software), 32.8 kg (BIA, Deurenberg equation) and 33.1 kg (DXA). The mean FM values were 5.6 kg (BIA software), 6.2 kg (BIA, Deurenberg equation) and 6.4 kg (DXA). There was a high correlation between the FFM values estimated with the two methods (BIA software vs DXA r=0.917, p<0.001; Deurenberg equation vs DXA r=0.931, p<0.001). For the FFM, the limits of agreement were equal to ±3.34 kg for the BIA software and ±2.96 kg for the Deurenberg equation. For the FM, the limits of agreement were equal to ±4.60 kg for the BIA software and ±3.82 kg for the Deurenberg equation. The results show a good correlation between DXA and BIA. BIA seems to be a valid alternative for epidemiological and clinical evaluations.