126 research outputs found
Relationships Among Foliar Phenology, Radial Growth Rate, and Xylem Density in a Young Douglas-Fir Plantation
We related intra-annual patterns in radial growth rate and xylem density to foliar phenology and second growth flushes in a young Douglas-fir plantation in western Washington. Three foliar maturity classes were defined: (1) shoots and needles elongating; (2) elongation complete, needles maturing; and (3) needles mature. Diameter growth rate had two peaks, one about the time of budbreak and one when foliage was in maturity Class 2. There was a limit to the maximum periodic density of xylem formed at a given rate of diameter growth; as growth rate increased, maximum periodic density decreased. Although xylem density profiles varied widely among individual trees, xylem density differed significantly among foliar maturity classes, increasing 16% from Class 1 to 2 and 60% from Class 2 to 3. Diameter growth rate of second-flushing trees was significantly greater in July compared with trees with no second flush, but we detected no relationships between second-flushing and xylem density patterns or false rings. Although the young trees in this study did not show distinct earlywood-latewood transitions, fully mature foliage (Class 3) was associated with formation of xylem exhibiting characteristics of latewood: greater density, reduced diameter growth rate, reduced tracheid radial diameter, and less interannual growth variation
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A Nonvolatile MOSFET Memory Device Based on Mobile Protons in SiO(2) Thin Films
It is shown how mobile H{sup +} ions can be generated thermally inside the oxide layer of Si/SiO{sub 2}/Si structures. The technique involves only standard silicon processing steps: the nonvolatile field effect transistor (NVFET) is based on a standard MOSFET with thermally grown SiO{sub 2} capped with a poly-silicon layer. The capped thermal oxide receives an anneal at {approximately}1100 C that enables the incorporation of the mobile protons into the gate oxide. The introduction of the protons is achieved by a subsequent 500-800 C anneal in a hydrogen-containing ambient, such as forming gas (N{sub 2}:H{sub 2} 95:5). The mobile protons are stable and entrapped inside the oxide layer, and unlike alkali ions, their space-charge distribution can be controlled and rapidly rearranged at room temperature by an applied electric field. Using this principle, a standard MOS transistor can be converted into a nonvolatile memory transistor that can be switched between normally on and normally off. Switching speed, retention, endurance, and radiation tolerance data are presented showing that this non-volatile memory technology can be competitive with existing Si-based non-volatile memory technologies such as the floating gate technologies (e.g. Flash memory)
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Nonvolatile Field Effect Transistors Based on Protons and Si/SiO{Sub 2}Si Structures
Recently, the authors have demonstrated that annealing Si/SiO{sub 2}/Si structures in a hydrogen containing ambient introduces mobile H{sup +} ions into the buried SiO{sub 2} layer. Changes in the H{sup +} spatial distribution within the SiO{sub 2} layer were electrically monitored by current-voltage (I-V) measurements. The ability to directly probe reversible protonic motion in Si/SiO{sub 2}/Si structures makes this an exemplar system to explore the physics and chemistry of hydrogen in the technologically relevant Si/SiO{sub 2} structure. In this work, they illustrate that this effect can be used as the basis for a programmable nonvolatile field effect transistor (NVFET) memory that may compete with other Si-based memory devices. The power of this novel device is its simplicity; it is based upon standard Si/SiO{sub 2}/Si technology and forming gas annealing, a common treatment used in integrated circuit processing. They also briefly discuss the effects of radiation on its retention properties
What Ecological Factors Shape Species-Area Curves in Neutral Models?
Understanding factors that shape biodiversity and species coexistence across scales is of utmost importance in ecology, both theoretically and for conservation policies. Species-area relationships (SARs), measuring how the number of observed species increases upon enlarging the sampled area, constitute a convenient tool for quantifying the spatial structure of biodiversity. While general features of species-area curves are quite universal across ecosystems, some quantitative aspects can change significantly. Several attempts have been made to link these variations to ecological forces. Within the framework of spatially explicit neutral models, here we scrutinize the effect of varying the local population size (i.e. the number of individuals per site) and the level of habitat saturation (allowing for empty sites). We conclude that species-area curves become shallower when the local population size increases, while habitat saturation, unless strongly violated, plays a marginal role. Our findings provide a plausible explanation of why SARs for microorganisms are flatter than those for larger organisms
Factors contributing to posttraumatic growth and its buffering effect in adult chidren of cancer patients undergoing treatment
This study examined relationships among demographic, clinical,
and psychosocial variables in adult children of cancer patients.
Two hundred and fourteen participants completed measures of
posttraumatic growth (PTG), distress, posttraumatic stress disorder
(PTSD) symptoms, social support, and family functioning. Significant
gender differences in all PTG dimensions were found, as well
as associations among PTG, gender, parental dependency, distress,
PTSD, and family functioning. Social support was not a mediator
in the relationship between gender and PTG. Gender, education,
disease duration, dependency, distress, and family flexibility predicted
PTG. Finally, PTG had amoderating effect in the relationship
between distress and PTSD/social support. These results may guide
psychosocial interventions in this population.Fundação para a Ciência e Tecnologia (FCT
Beyond NIMBYs and NOOMBYs:what can wind farm controversies teach us about public involvement in hospital closures?
Background Many policymakers, researchers and commentators argue that hospital closures are necessary as health systems adapt to new technological and financial contexts, and as population health needs in developed countries shift. However closures are often unpopular with local communities. Previous research has characterised public opposition as an obstacle to change. Public opposition to the siting of wind farms, often described as NIMBYism (Not In My Back Yard), is a useful comparator issue to the perceived NOOMBYism (Not Out Of My Back Yard) of hospital closure protestors. Discussion The analysis of public attitudes to wind farms has moved from a fairly crude characterisation of the ‘attitude-behaviour gap’ between publics who support the idea of wind energy, but oppose local wind farms, to empirical, often qualitative, studies of public perspectives. These have emphasised the complexity of public attitudes, and revealed some of the ‘rational’ concerns which lie beneath protests. Research has also explored processes of community engagement within the wind farm decision-making process, and the crucial role of trust between communities, authorities, and developers. Summary Drawing on what has been learnt from studies of opposition to wind farms, we suggest a range of questions and approaches to explore public perspectives on hospital closure more thoroughly. Understanding the range of public responses to service change is an important first step in resolving the practical dilemma of effecting health system transformation in a democratic fashion
Shedding Light on the Galaxy Luminosity Function
From as early as the 1930s, astronomers have tried to quantify the
statistical nature of the evolution and large-scale structure of galaxies by
studying their luminosity distribution as a function of redshift - known as the
galaxy luminosity function (LF). Accurately constructing the LF remains a
popular and yet tricky pursuit in modern observational cosmology where the
presence of observational selection effects due to e.g. detection thresholds in
apparent magnitude, colour, surface brightness or some combination thereof can
render any given galaxy survey incomplete and thus introduce bias into the LF.
Over the last seventy years there have been numerous sophisticated
statistical approaches devised to tackle these issues; all have advantages --
but not one is perfect. This review takes a broad historical look at the key
statistical tools that have been developed over this period, discussing their
relative merits and highlighting any significant extensions and modifications.
In addition, the more generalised methods that have emerged within the last few
years are examined. These methods propose a more rigorous statistical framework
within which to determine the LF compared to some of the more traditional
methods. I also look at how photometric redshift estimations are being
incorporated into the LF methodology as well as considering the construction of
bivariate LFs. Finally, I review the ongoing development of completeness
estimators which test some of the fundamental assumptions going into LF
estimators and can be powerful probes of any residual systematic effects
inherent magnitude-redshift data.Comment: 95 pages, 23 figures, 3 tables. Now published in The Astronomy &
Astrophysics Review. This version: bring in line with A&AR format
requirements, also minor typo corrections made, additional citations and
higher rez images adde
Elective Cancer Surgery in COVID-19-Free Surgical Pathways During the SARS-CoV-2 Pandemic: An International, Multicenter, Comparative Cohort Study.
PURPOSE: As cancer surgery restarts after the first COVID-19 wave, health care providers urgently require data to determine where elective surgery is best performed. This study aimed to determine whether COVID-19-free surgical pathways were associated with lower postoperative pulmonary complication rates compared with hospitals with no defined pathway. PATIENTS AND METHODS: This international, multicenter cohort study included patients who underwent elective surgery for 10 solid cancer types without preoperative suspicion of SARS-CoV-2. Participating hospitals included patients from local emergence of SARS-CoV-2 until April 19, 2020. At the time of surgery, hospitals were defined as having a COVID-19-free surgical pathway (complete segregation of the operating theater, critical care, and inpatient ward areas) or no defined pathway (incomplete or no segregation, areas shared with patients with COVID-19). The primary outcome was 30-day postoperative pulmonary complications (pneumonia, acute respiratory distress syndrome, unexpected ventilation). RESULTS: Of 9,171 patients from 447 hospitals in 55 countries, 2,481 were operated on in COVID-19-free surgical pathways. Patients who underwent surgery within COVID-19-free surgical pathways were younger with fewer comorbidities than those in hospitals with no defined pathway but with similar proportions of major surgery. After adjustment, pulmonary complication rates were lower with COVID-19-free surgical pathways (2.2% v 4.9%; adjusted odds ratio [aOR], 0.62; 95% CI, 0.44 to 0.86). This was consistent in sensitivity analyses for low-risk patients (American Society of Anesthesiologists grade 1/2), propensity score-matched models, and patients with negative SARS-CoV-2 preoperative tests. The postoperative SARS-CoV-2 infection rate was also lower in COVID-19-free surgical pathways (2.1% v 3.6%; aOR, 0.53; 95% CI, 0.36 to 0.76). CONCLUSION: Within available resources, dedicated COVID-19-free surgical pathways should be established to provide safe elective cancer surgery during current and before future SARS-CoV-2 outbreaks
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