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Search Results: 1 - 10 of 212246 matches for " Adrian L. Cavalieri "
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Perinatal consequences of disproportionate fetal trunk growth  [PDF]
Ralph L. Cavalieri, Suzanne Laroche, Wayne R. Cohen
Open Journal of Obstetrics and Gynecology (OJOG) , 2012, DOI: 10.4236/ojog.2012.22025
Abstract: Objective: To identify the impact of an abnormally large neonatal chest circumference relative to head circumference on labor and neonatal morbidity. Methods: We used a retrospective cohort design to study 54 obstetric cases in which the neonatal thoracic circumference was ≥2.5 cm greater than that of the head. For each case we sought controls with a smaller thorax-head circumference difference. Ninety-seven controls were matched with their respective cases for birth weight, parity, maternal body mass index (BMI), and maternal ethnicity. Results: Cases had significantly smaller heads and larger trunks than controls (P < 0.0001). Cases were twice as likely (39% vs 19%, P = 0.007) to require admission to the neonatal intensive care unit. There was no significant difference between cases and controls in the frequency of shoulder dystocia, long second stage, or long deceleration phase of labor. However, compound presentations occurred more frequently in the cases than in controls (5.5% vs 0%, P = 0.044). Conclusion: Babies with disproportionately large trunk growth were at risk for requiring neonatal intensive care and for compound presentation.
Momentum-dependent snapshots of a melting charge density wave
Jesse C. Petersen,Stefan Kaiser,Nicky Dean,Alberto Simoncig,Haiyun Liu,Adrian L. Cavalieri,Cephise Cacho,I. C. Edmond Turcu,Emma Springate,Fabio Frassetto,Luca Poletto,Sarnjeet S. Dhesi,Helmuth Berger,Andrea Cavalleri
Physics , 2010, DOI: 10.1103/PhysRevLett.107.177402
Abstract: Charge density waves (CDWs) underpin the electronic properties of many complex materials. Near-equilibrium CDW order is linearly coupled to a periodic, atomic-structural distortion, and the dynamics is understood in terms of amplitude and phase modes. However, at the shortest timescales lattice and charge order may become de-coupled, highlighting the electronic nature of this many-body broken symmetry ground state. Using time and angle resolved photoemission spectroscopy with sub-30-fs XUV pulses, we have mapped the time- and momentum-dependent electronic structure in photo-stimulated 1T-TaS2, a prototypical two-dimensional charge density wave compound. We find that CDW order, observed as a splitting of the uppermost electronic bands at the Brillouin zone boundary, melts well before relaxation of the underlying structural distortion. Decoupled charge and lattice modulations challenge the view of Fermi Surface nesting as a driving force for charge density wave formation in 1T-TaS2.
Arctic sea ice variability and trends, 1979–2010
D. J. Cavalieri,C. L. Parkinson
The Cryosphere Discussions , 2012, DOI: 10.5194/tcd-6-957-2012
Abstract: Analyses of 32 yr (1979–2010) of Arctic sea ice extents and areas derived from satellite passive microwave radiometers are presented for the Northern Hemisphere as a whole and for nine Arctic regions. There is an overall negative yearly trend of 51.5 ± 4.1 × 103 km2 yr 1 ( 4.1 ± 0.3% decade 1) in sea ice extent for the hemisphere. The sea ice extent trends for the individual Arctic regions are all negative except for the Bering Sea: 3.9 ± 1.1 × 103 km2 yr 1 ( 8.7 ± 2.5% decade 1) for the Seas of Okhotsk and Japan, +0.3 ± 0.8 × 103 km2 yr 1 (+1.2 ± 2.7% decade 1) for the Bering Sea, 4.4 ± 0.7 × 103 km2 yr 1 ( 5.1 ± 0.9% decade 1) for Hudson Bay, 7.6 ± 1.6 × 103 km2 yr 1 ( 8.5 ± 1.8% decade 1) for Baffin Bay/Labrador Sea, 0.5 ± 0.3 × 103 km2 yr 1 ( 5.9 ± 3.5% decade 1) for the Gulf of St. Lawrence, 6.5 ± 1.1 × 103 km2 yr 1 ( 8.6 ± 1.5% decade 1) for the Greenland Sea, 13.5 ± 2.3 × 103 km2 yr 1 ( 9.2 ± 1.6% decade 1) for the Kara and Barents Seas, 14.6 ± 2.3 × 103 km2 yr 1 ( 2.1 ± 0.3% decade 1) for the Arctic Ocean, and 0.9 ± 0.4 × 103 km2 yr 1 ( 1.3 ± 0.5% decade 1) for the Canadian Archipelago. Similarly, the yearly trends for sea ice areas are all negative except for the Bering Sea. On a seasonal basis for both sea ice extents and areas, the largest negative trend is observed for summer with the next largest negative trend being for autumn.
Antarctic sea ice variability and trends, 1979–2010
C. L. Parkinson,D. J. Cavalieri
The Cryosphere , 2012, DOI: 10.5194/tc-6-871-2012
Abstract: In sharp contrast to the decreasing sea ice coverage of the Arctic, in the Antarctic the sea ice cover has, on average, expanded since the late 1970s. More specifically, satellite passive-microwave data for the period November 1978–December 2010 reveal an overall positive trend in ice extents of 17 100 ± 2300 km2 yr 1. Much of the increase, at 13 700 ± 1500 km2 yr 1, has occurred in the region of the Ross Sea, with lesser contributions from the Weddell Sea and Indian Ocean. One region, that of the Bellingshausen/Amundsen Seas, has (like the Arctic) instead experienced significant sea ice decreases, with an overall ice extent trend of 8200 ± 1200 km2 yr 1. When examined through the annual cycle over the 32-yr period 1979–2010, the Southern Hemisphere sea ice cover as a whole experienced positive ice extent trends in every month, ranging in magnitude from a low of 9100 ± 6300 km2 yr 1 in February to a high of 24 700 ± 10 000 km2 yr 1 in May. The Ross Sea and Indian Ocean also had positive trends in each month, while the Bellingshausen/Amundsen Seas had negative trends in each month, and the Weddell Sea and western Pacific Ocean had a mixture of positive and negative trends. Comparing ice-area results to ice-extent results, in each case the ice-area trend has the same sign as the ice-extent trend, but the magnitudes of the two trends differ, and in some cases these differences allow inferences about the corresponding changes in sea ice concentrations. The strong pattern of decreasing ice coverage in the Bellingshausen/Amundsen Seas region and increasing ice coverage in the Ross Sea region is suggestive of changes in atmospheric circulation. This is a key topic for future research.
Arctic sea ice variability and trends, 1979–2010
D. J. Cavalieri,C. L. Parkinson
The Cryosphere , 2012, DOI: 10.5194/tc-6-881-2012
Abstract: Analyses of 32 yr (1979–2010) of Arctic sea ice extents and areas derived from satellite passive microwave radiometers are presented for the Northern Hemisphere as a whole and for nine Arctic regions. There is an overall negative yearly trend of 51.5 ± 4.1 × 103 km2 yr 1 ( 4.1 ± 0.3% decade 1) in sea ice extent for the hemisphere. The yearly sea ice extent trends for the individual Arctic regions are all negative except for the Bering Sea: 3.9 ± 1.1 × 103 km2 yr 1 ( 8.7 ± 2.5% decade 1) for the Seas of Okhotsk and Japan, +0.3 ± 0.8 × 103 km2 yr 1 (+1.2 ± 2.7% decade 1) for the Bering Sea, 4.4 ± 0.7 × 103 km2 yr 1 ( 5.1 ± 0.9% decade 1) for Hudson Bay, 7.6 ± 1.6 × 103 km2 yr 1 ( 8.5 ± 1.8% decade 1) for Baffin Bay/Labrador Sea, 0.5 ± 0.3 × 103 km2 yr 1 ( 5.9 ± 3.5% decade 1) for the Gulf of St. Lawrence, 6.5 ± 1.1 × 103 km2 yr 1 ( 8.6 ± 1.5% decade 1) for the Greenland Sea, 13.5 ± 2.3 × 103 km2 yr 1 ( 9.2 ± 1.6% decade 1) for the Kara and Barents Seas, 14.6 ± 2.3 × 103 km2 yr 1 ( 2.1 ± 0.3% decade 1) for the Arctic Ocean, and 0.9 ± 0.4 × 103 km2 yr 1 ( 1.3 ± 0.5% decade 1) for the Canadian Archipelago. Similarly, the yearly trends for sea ice areas are all negative except for the Bering Sea. On a seasonal basis for both sea ice extents and areas, the largest negative trend is observed for summer with the next largest negative trend being for autumn. Both the sea ice extent and area trends vary widely by month depending on region and season. For the Northern Hemisphere as a whole, all 12 months show negative sea ice extent trends with a minimum magnitude in May and a maximum magnitude in September, whereas the corresponding sea ice area trends are smaller in magnitude and reach minimum and maximum values in March and September.
Antarctic sea ice variability and trends, 1979–2010
C. L. Parkinson,D. J. Cavalieri
The Cryosphere Discussions , 2012, DOI: 10.5194/tcd-6-931-2012
Abstract: In sharp contrast to the decreasing sea ice coverage of the Arctic, in the Antarctic the sea ice cover has, on average, expanded since the late 1970s. More specifically, satellite passive-microwave data for the period November 1978–December 2010 reveal an overall positive trend in ice extents of 17 100 ± 2300 km2 yr 1. Much of the increase, at 13 700 ± 1500 km2 yr 1, has occurred in the region of the Ross Sea, with lesser contributions from the Weddell Sea and Indian Ocean. One region, that of the Bellingshausen/Amundsen Seas, has, like the Arctic, instead experienced significant sea ice decreases, with an overall ice extent trend of 8200 ± 1200 km2 yr 1. When examined through the annual cycle over the 32-yr period 1979–2010, the Southern Hemisphere sea ice cover as a whole experienced positive ice extent trends in every month, ranging in magnitude from a low of 9100 ± 6300 km2 yr 1 in February to a high of 24 700 ± 10 000 km2 yr 1 in May. The Ross Sea and Indian Ocean also had positive trends in each month, while the Bellingshausen/Amundsen Seas had negative trends in each month, and the Weddell Sea and Western Pacific Ocean had a mixture of positive and negative trends. Comparing ice-area results to ice-extent results, in each case the ice-area trend has the same sign as the ice-extent trend, but differences in the magnitudes of the two trends identify regions with overall increasing ice concentrations and others with overall decreasing ice concentrations. The strong pattern of decreasing ice coverage in the Bellingshausen/Amundsen Seas region and increasing ice coverage in the Ross Sea region is suggestive of changes in atmospheric circulation. This is a key topic for future research.
Evaluacion termica, mecanica y electrica de materiales compuestos cordierita-mullita
Camerucci, M.A.;Urretavizcaya, G.;Cavalieri, A.L.;
Materials Research , 2000, DOI: 10.1590/S1516-14392000000400006
Abstract: commercially available cordierite and mullite powders were used to obtain cordierite and cordierite-30wt% mullite materials by attrition milling, uniaxial pressing and sintering. cordierite powders were the coarse (d50 = 1.82 mm), medium (d50 = 0.9 mm) and fine (d50 = 0.45 mm) single granulometric fractions and binary mixtures of them. mullite powder employed in composites was the 7 h-attrition milled one (d50 = 1.3 mm). hardness (hv) and fracture toughness (kic) were measured by vickers indentation techniques. composites showed higher hv and kic than cordierite matrices. in both materials, hv and kic diminish with the increasing porosity. dielectric constant (e) and losses (tan d) were determined at 1 mhz. an increase in e and tan d values was registered when mullite was present in composites with respect to cordierite material. higher the porosity, e was lower and tan d increased. the thermal expansion coefficients (a) were determined up to 1000 °c resulting the a of the composite close to that of the silicon.
Análisis por elementos finitos de alúmina sometida a esfuerzos mecánicos y térmicos
Tomba Martinez, A.G.;Cavalieri, A.L.;
Materials Research , 2001, DOI: 10.1590/S1516-14392001000100003
Abstract: disks of a commercial alumina were fabricated by slip casting, calcination and sintering. the surfaces were machined using sic papers (120 and 320 grit) and characterized by residual stresses measurements. the mechanical strength was determined in biaxial flexure (ball on discontinuous ring). the specimens were subjected to thermal shock conditions (cooling using a high-velocity air jet) and the critical temperature differential for crack propagation was determined. the temperature and stress distributions during air impinging were calculated using a finite element method. the value of the heat transfer coefficient was estimated by fitting the calculated temperature profiles with those measured during each test. the calculated tension for the thermal shock fracture was compared with the mechanical strength, together with the fracture features in each case. the differences were explained on the basis of the calculated stress distributions.
Evaluacion termica, mecanica y electrica de materiales compuestos cordierita-mullita
Camerucci M.A.,Urretavizcaya G.,Cavalieri A.L.
Materials Research , 2000,
Abstract: Commercially available cordierite and mullite powders were used to obtain cordierite and cordierite-30wt% mullite materials by attrition milling, uniaxial pressing and sintering. Cordierite powders were the coarse (D50 = 1.82 mum), medium (D50 = 0.9 mum) and fine (D50 = 0.45 mum) single granulometric fractions and binary mixtures of them. Mullite powder employed in composites was the 7 h-attrition milled one (D50 = 1.3 mum). Hardness (H V) and fracture toughness (K IC) were measured by Vickers indentation techniques. Composites showed higher H V and K IC than cordierite matrices. In both materials, H V and K IC diminish with the increasing porosity. Dielectric constant (epsilon) and losses (tan delta) were determined at 1 MHz. An increase in epsilon and tan delta values was registered when mullite was present in composites with respect to cordierite material. Higher the porosity, epsilon was lower and tan delta increased. The thermal expansion coefficients (alpha) were determined up to 1000 °C resulting the alpha of the composite close to that of the silicon.
Análisis por elementos finitos de alúmina sometida a esfuerzos mecánicos y térmicos
Tomba Martinez A.G.,Cavalieri A.L.
Materials Research , 2001,
Abstract: Disks of a commercial alumina were fabricated by slip casting, calcination and sintering. The surfaces were machined using SiC papers (120 and 320 grit) and characterized by residual stresses measurements. The mechanical strength was determined in biaxial flexure (ball on discontinuous ring). The specimens were subjected to thermal shock conditions (cooling using a high-velocity air jet) and the critical temperature differential for crack propagation was determined. The temperature and stress distributions during air impinging were calculated using a finite element method. The value of the heat transfer coefficient was estimated by fitting the calculated temperature profiles with those measured during each test. The calculated tension for the thermal shock fracture was compared with the mechanical strength, together with the fracture features in each case. The differences were explained on the basis of the calculated stress distributions.
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