Exactly-solvable problems for two-dimensional excitons

Several problems in mathematical physics relating to excitons in two dimensions are considered. First, a fascinating numerical result from a theoretical treatment of screened excitons stimulates a re-evaluation of the familiar two-dimensional hydrogen atom. Formulating the latter problem in momentum space leads to a new integral relation in terms of special functions, and fresh insights into the dynamical symmetry of the system are also obtained. A discussion of an alternative potential to model screened excitons is given, and the variable phase method is used to compare bound-state energies and scattering phase shifts for this potential with those obtained using the two-dimensional analogue of the Yukawa potential. The second problem relates to excitons in a quantising magnetic field in the fractional quantum Hall regime. An exciton against the background of an incompressible quantum liquid is modelled as a few-particle neutral composite consisting of a positively-charged hole and several quasielectrons with fractional negative charge. A complete set of exciton basis functions is derived, and these functions are classified using a result from the theory of partitions. Some exact results are obtained for this complex few-particle problem.Comment: 66 pages, 9 figure

Refractory Hypercalcemia in Sarcoidosis: Exacerbation by thiazide diuretics, differentiation from primary hyperparathyroidism, and possible role of prolactin

Hypercalcemia in a patient with sarcoidosis was made worse by a thiazide diuretic initially given to control hypercalciuria alone. The hypercalcemia was unusually resistant to corticosteroid treatment during the summer even after the thiazide diuretic had been discontinued. Lack of response to corticosteroid together with decreased tubular reabsorption of phosphate and increased tubular reabsorption of calcium suggested associated primary hyperparathyroidism, but PTH was undetectable by immunoassay, and nephrogenous cyclic AMP excretion was zero. Amenorrhea, galactorrhea and hyperprolactinemia were found to be due to a pituitary tumor which was removed. The experience with this patient suggests that: 1) exacerbation of hypercalcemia by thiazides does not discriminate between its different causes; 2) finding low values for plasma parathyroid homone (PTH) and nephrogenous cyclic AMP is the most certain way of excluding primary hyperparathyroidism in patients with hypercalcemia from other causes; 3) prolactin excess, by increasing the synthesis of 1,25 dihydroxycholecalciferol, may have intensified the calcium metabolism disorder

Produção de milho e sorgo em várzea.

ECOFISIOLOGIA E FENOLOGIA DAS CULTURAS DO MILHO E DO SORGO (Paulo Regis Ferreira da Silva; Gilber Argenta pag 7-18); NUTRIÇÃO, CORREÇÃO DO SOLO E ADUBAÇÃO (Walkyria Bueno Scivittaro pag 19-26); SISTEMAS DE CULTIVO DE MILHO EM VÁRZEA - PLANTIO DIRETO (Francisco de Jesus Vernetti Junior; Algenor da Silva Gomes pag 27-38); IMPLANTAÇÃO DA LAVOURA DE MILHO (Marilda Pereira Porto; Claudio Alberto Sousa da Silva; José Maria Barbat Parfitt; Silvio Steinmetz pag 39-43); CULTIVARES DE MILHO (Marilda Pereira Porto pag 45-55); MANEJO DA CULTURA DO SORGO (Antonio André Amaral Raupp pag 57-59); DRENAGEM E IRRIGAÇÃO PARA MILHO E SORGO CULTIVADOS EM ROTAÇÃO COM ARROZ IRRIGADO (Claudio Alberto Souza da Silva; José Maria Barbat Partitt pag 61-72); ADEQUAÇÃO DA ÁREA PARA A SEMEADURA DO SORGO E DO MILHO IRRIGADOS POR INUNDAÇÃO (José Barbat Partitt; Claudio Alberto S. da Silva pag 73-76); MANEJO DE PLANTAS DANINHAS NA CULTURA DO MILHO EM TERRAS BAIXAS (André Andres; Aldo Merotto Júnior pag 77-86); INSETOS-PRAGAS DAS CULTURAS DO MILHO E DO SORGO NO AGROECOSSISTEMA DE VÁRZEA (Anderson Dionei Grützmacher; José Francisco da Silva Martins; Uemerson Silva da Cunha pag 87-101); DOENÇAS DAS CULTURAS DO SORGO E DO MILHO (Nely Brancão pag 103-106); SECAGEM E ARMAZENAMENTO DE GRÃOS DE MILHO E DE SORGO NA PROPRIEDADE RURAL (Moacir Cardoso Elias pag 107-146).bitstream/item/84493/1/Documento-74-.pdf; bitstream/item/84479/1/Documento-74-pag-001-018.pdf; bitstream/item/84480/1/Documento-74-pag-019-026.pdf; bitstream/item/84481/1/Documento-74-pag-027-038.pdf; bitstream/item/84482/1/Documento-74-pag-039-043.pdf; bitstream/item/84483/1/Documento-74-pag-045-055.pdf; bitstream/item/84484/1/Documento-74-pag-057-059.pdf; bitstream/item/84485/1/Documento-74-pag-061-072.pdf; bitstream/item/84487/1/Documento-74-pag-073-076.pdf; bitstream/item/84488/1/Documento-74-pag-077-086.pdf; bitstream/item/84489/1/Documento-74-pag-087-101.pdf; bitstream/item/84490/1/Documento-74-pag-103-106.pdf; bitstream/item/84492/1/Documento-74-pag-107-146.pd

Use of shallow samples to estimate the total carbon storage in pastoral soils

Using data from pastoral soils sampled by horizon at 56 locations across New Zealand, we conducted a meta-analysis. On average, the total depth sampled was 0.93 ± 0.026 m (± SEM), and on a volumetric basis, the total C storage averaged 26.9 ± 1.8, 13.9 ± 0.6 and 9.2 ± 1.4 kg C m⁻² for allophanic (n=12), non-allophanic (n=40) and pumice soils (n=4), respectively. We estimated the total C storage, and quantified the uncertainty, using the data for samples taken from the uppermost A-horizon whose depth averaged 0.1 ± 0.003 m. For A-horizon samples of the allophanic soils, the mean C content was 108 ± 6 g C kg⁻¹ and the bulk density was 772 ± 29 kg m⁻³, for non-allophanic soils they were 51 ± 4 g C kg⁻¹ and 1055 ± 29 kg m⁻³, and for pumice soils they were 68 ± 9 g C kg⁻¹ and 715 ± 45 kg m⁻³. The C density —a product of the C content and bulk density —of the A-horizon samples was proportional to their air-dried water content, a proxy measure for the mineral surface area. By linear regression with C density of the A-horizon, the total C storage could be estimated with a standard error of 3.1 kg C m⁻², 19% of the overall mean

Genome-wide DNA-(de)methylation is associated with Noninfectious Bud-failure exhibition in Almond (Prunus dulcis [Mill.] D.A.Webb).

Noninfectious bud-failure (BF) remains a major threat to almond production in California, particularly with the recent rapid expansion of acreage and as more intensive cultural practices and modern cultivars are adopted. BF has been shown to be inherited in both vegetative and sexual progeny, with exhibition related to the age and propagation history of scion clonal sources. These characteristics suggest an epigenetic influence, such as the loss of juvenility mediated by DNA-(de)methylation. Various degrees of BF have been reported among cultivars as well as within sources of clonal propagation of the same cultivar. Genome-wide methylation profiles for different clones within almond genotypes were developed to examine their association with BF levels and association with the chronological time from initial propagation. The degree of BF exhibition was found to be associated with DNA-(de)methylation and clonal age, which suggests that epigenetic changes associated with ageing may be involved in the differential exhibition of BF within and among almond clones. Research is needed to investigate the potential of DNA-(de)methylation status as a predictor for BF as well as for effective strategies to improve clonal selection against age related deterioration. This is the first report of an epigenetic-related disorder threatening a major tree crop

Irreversibility of advanced osteoporosis: Limited role for pharmacologic intervention

Osteoporosis is of medical interest only because it increases bone fragility and risk of fracture, and except for relief of symptoms, preventing fracture is the only purpose of intervention. To prevent the first fracture, adequate bone density must be accumulated and conserved, but to prevent subsequent fracture, bone density must be augmented so that the supportive function of the skeleton can be restored. Almost 50 years after the recognition of post menopausal osteoporosis as a clinical entity, not one of the many treatments that have been used has been demonstrated to be efficacious in reducing subsequent fracture risk. My purpose is not to recite this chronicle of disappointment, but to account for it in terms of bone biology, to consider some possible exceptions, and to reiterate the importance of preventing damage to the skeleton rather than belatedly attempting its repair

A 14-day ground-based hypokinesia study in nonhuman primates: A compilation of results

A 14 day ground based hypokinesia study with rhesus monkeys was conducted to determine if a spaceflight of similar duration might affect bone remodeling and calcium homeostatis. The monkeys were placed in total body casts and sacrificed either immediately upon decasting or 14 days after decasting. Changes in vertebral strength were noted and further deterioration of bone strength continued during the recovery phase. Resorption in the vertebrae increased dramatically while formation decreased. Cortical bone formation was impaired in the long bones. The immobilized animals showed a progressive decrease in total serum calcium which rebounded upon remobilization. Most mandibular parameters remained unchanged during casting except for retardation of osteon birth or maturation rate and density distribution of matrix and mineral moieties

Effective use of Pupil Premium Plus to improve educational outcomes for looked after children

This publication reports on research funded by the National Association of Virtual School Heads and presents insights into the use of Pupil Premium Plus (PP+) to support educational outcomes for looked after children. Using data generated from Virtual School Heads, Designated Teachers and other stakeholder professionals, supported by available academic and policy texts, these insights together with emerging evidence of gaps in guidance and support inform a set of recommendations for stakeholders to consider to support educational outcomes for looked after children; specifically relating to: 1) The guidance and support available for effective use of PP+; 2) How PP+ is used and allocated; and 3) How impact of PP+-funded interventions is evidenced

The two-dimensional hydrogen atom revisited

The bound state energy eigenvalues for the two-dimensional Kepler problem are found to be degenerate. This "accidental" degeneracy is due to the existence of a two-dimensional analogue of the quantum-mechanical Runge-Lenz vector. Reformulating the problem in momentum space leads to an integral form of the Schroedinger equation. This equation is solved by projecting the two-dimensional momentum space onto the surface of a three-dimensional sphere. The eigenfunctions are then expanded in terms of spherical harmonics, and this leads to an integral relation in terms of special functions which has not previously been tabulated. The dynamical symmetry of the problem is also considered, and it is shown that the two components of the Runge-Lenz vector in real space correspond to the generators of infinitesimal rotations about the respective coordinate axes in momentum space.Comment: 10 pages, no figures, RevTex