3,196 research outputs found
For Fixed Control Parameters the Quantum Approximate Optimization Algorithm's Objective Function Value Concentrates for Typical Instances
The Quantum Approximate Optimization Algorithm, QAOA, uses a shallow depth
quantum circuit to produce a parameter dependent state. For a given
combinatorial optimization problem instance, the quantum expectation of the
associated cost function is the parameter dependent objective function of the
QAOA. We demonstrate that if the parameters are fixed and the instance comes
from a reasonable distribution then the objective function value is
concentrated in the sense that typical instances have (nearly) the same value
of the objective function. This applies not just for optimal parameters as the
whole landscape is instance independent. We can prove this is true for low
depth quantum circuits for instances of MaxCut on large 3-regular graphs. Our
results generalize beyond this example. We support the arguments with numerical
examples that show remarkable concentration. For higher depth circuits the
numerics also show concentration and we argue for this using the Law of Large
Numbers. We also observe by simulation that if we find parameters which result
in good performance at say 10 bits these same parameters result in good
performance at say 24 bits. These findings suggest ways to run the QAOA that
reduce or eliminate the use of the outer loop optimization and may allow us to
find good solutions with fewer calls to the quantum computer.Comment: 16 pages, 1 figur
Five Years Experience of Ureterovaginal Fistulae Following Obstetric or Gynecological Intervention in Ethiopia
Objectives: To study the etiology, presentation and outcome of women presenting to the Addis Ababa Fistula Hospital with an ureterovaginal fistula.Patients and Methods: Women presenting with ureterovaginal fistulae following obstetric or gynecological intervention. The operating register from June 2004 to July 2009 was studied to identify women who had undergone ureteric re-implantation. Patient files were reviewed and onlywomen with fistulae resulting from iatrogenic injury were included.Results: Ureterovaginal fistulae were found in 89 women, 64 after Caesarean section, of which 43 were for a stillborn baby, 12 women have uterine rupture, 6 with instrumental delivery and only 7 with abdominal hysterectomy. The left ureter was most frequently injured (54). The number of patients seen has doubled over the past two years. Using one of four methods of repair, 88 women were continent at discharge from hospital. One died from a suspected pulmonary embolism.Conclusion: The incidence of iatrogenic ureteric injury is increasing in Ethiopia and most result from Caesarean section. The reasons should be studied. Using a variety of repair techniques, all patients can be cured. However, surgeons undertaking this surgery should have a wide range of urological training.Key Words : Ureter, vagina, fistula, latrogenic, caesarean section, hysterectomy, complicatio
Environmental Site Characterization and Risk-Based Evaluation of a Site Contaminated with Tetrachloroethene (PCE) and Trichloroethene (TCE)
A healthcare company purchased property in eastern Iowa for a facility expansion. Before the purchase, a Phase I environmental site assessment (ESA) revealed that the property was the site of a former dry cleaning business. Phase II sampling and testing indicated that tetrachloroethene (PCE) and trichloroethene (TCE) had affected site soil and groundwater. Maximum concentrations of PCE and TCE in groundwater were 538 and 209 µg/L, respectively, and 105 and 1.51 mg/kg in soil. Additional sampling delineated the vertical and horizontal extent of contamination in the soil. The concentrations of the chlorinated solvents in both the soil and groundwater were below levels of regulatory concern. However, the company was concerned that the Iowa statewide standard for PCE in soil (780 mg/kg) might not provide adequate protection for several exposure pathways and wanted to assess the risk to the public from the contamination at the site. The results of a receptor survey were used to develop site-specific target levels (SSTLs) for contamination, using accepted human health exposure factors, models, and chemical-specific toxicity values. The recommended remedial options allowed the company to minimize the human health risks posed by contamination at the site
Ipratropium bromide delivered by metered-dose aerosol to infant wheezers
Two methods of administration of ipratropium bromide (Atrovent; Boehringer Ingelheim) to wheezing children'< 25 months of age were compared: (i) the conventional nebulisation (15 children); and (ii) a metered-dose aerosol plus spacer and mask (MDA group, 17 children). The drug induced a significant and similar fall in respiratory rate in both groups. Transcutaneous carbon dioxide pressure was also reduced significantly but was more marked in the MDA group. This increase in alveolar ventilation was 'similar in those < 12 months as in older children; in those with recurrent or with first time wheezing; and in those with radiological evidence of pneumonia. Clinical assessment of bronchospasm and recession was recorded as improved' in over 80% of both groups. The MDA delivery of ipratropium bromide was as effective as nebulisation and was more convenient, since it required less time and equipment. It was also well accepted by the small patients
Beans ( Phaseolus spp.) - model food legumes
Globally, 800 million people are malnourished. Heavily subsidised farmers in rich countries produce sufficient surplus food to feed the hungry, but not at a price the poor can afford. Even donating the rich world's surplus to the poor would not solve the problem. Most poor people earn their living from agriculture, so a deluge of free food would destroy their livelihoods. Thus, the only answer to world hunger is to safeguard and improve the productivity of farmers in poor countries. Diets of subsistence level farmers in Africa and Latin America often contain sufficient carbohydrates (through cassava, corn/maize, rice, wheat, etc.), but are poor in proteins. Dietary proteins can take the form of scarce animal products (eggs, milk, meat, etc.), but are usually derived from legumes (plants of the bean and pea family). Legumes are vital in agriculture as they form associations with bacteria that 'sfix-nitrogen' from the air. Effectively this amounts to internal fertilisation and is the main reason that legumes are richer in proteins than all other plants. Thousands of legume species exist but more common beans (Phaseolus vulgaris L.) are eaten than any other. In some countries such as Mexico and Brazil, beans are the primary source of protein in human diets. As half the grain legumes consumed worldwide are common beans, they represent the species of choice for the study of grain legume nutrition. Unfortunately, the yields of common beans are low even by the standards of legumes, and the quality of their seed proteins is sub-optimal. Most probably this results from millennia of selection for stable rather than high yield, and as such, is a problem that can be redressed by modern genetic techniques. We have formed an international consortium called Phaseomics' to establish the necessary framework of knowledge and materials that will result in disease-resistant, stress-tolerant, high-quality protein and high-yielding beans. Phaseomics will be instrumental in improving living conditions in deprived regions of Africa and the Americas. It will contribute to social equity and sustainable development and enhance inter- and intra-cultural understanding, knowledge and relationships. A major goal of Phaseomics is to generate new common bean varieties that are not only suitable for but also desired by the local farmer and consumer communities. Therefore, the socio-economic dimension of improved bean production and the analysis of factors influencing the acceptance of novel varieties will be an integral part of the proposed research (see Figure 1). Here, we give an overview of the economic and nutritional importance of common beans as a food crop. Priorities and targets of current breeding programmes are outlined, along with ongoing efforts in genomics. Recommendations for an international coordinated effort to join knowledge, facilities and expertise in a variety of scientific undertakings that will contribute to the overall goal of better beans are given. To be rapid and effective, plant breeding programmes (i.e., those that involve crossing two different 'sparents') rely heavily on molecular 'smarkers'. These genetic landmarks are used to positio
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