On the rise and fall of a ball with linear or quadratic drag

We review the problem of a vertically thrown ball, with a drag force which is either linear or quadratic in the speed. It is stressed from the outset that these two types of drag correspond to specific ranges of the Reynolds number (Re<1 and 103<Re<2×105, respectively) and do not hold outside these intervals. We also include the buoyant force in our treatment of the problem. The equations of motion are solved analytically and several true-to-life examples are discussed. The calculations are somewhat harder than for the well-known case without drag force, but no highbrow mathematics is required and the extra effort is amply compensated by the gain in realism and surprise value. © 1999 American Association of Physics Teachers

Evolution of the Great Tehuelche Paleolake in the Torres del Paine National Park of Chilean Patagonia during the Last Glacial Maximum and Holocene

Indexación: Web of Science; ScieloRESUMEN. Una serie de morrenas glaciares se distribuyen desde el margen oriental de la cuenca de drenaje Torres del Paine a cerca del actual margen de los Campos de Hielo Patagónico, junto con una serie de terrazas lacustres regional continuos relacionados con las fluctuaciones glaciales. La geomorfología, apoyada por la evidencia de sedimentos del lago, indica la existencia de un único paleolago proglacial en esta zona, aquí denominado el Gran Tehuelche paleolago. Este concepto ayuda a aclarar la cronología de eventos glaciales y conduce a una mejor comprensión de la evolución del sistema hidrológico de la zona de Torres del Paine. Avances glaciales referidos anteriormente como ocurrieron A, B y C durante el Último Máximo Glacial y alimentados con la Gran Tehuelche paleolago con agua de deshielo, que le permite alcanzar su máxima extensión. El descubrimiento de trombolitos en Laguna Amarga sugiere que el drenaje de la paleolago hacia el fiordo de Última Esperanza tuvo lugar en 7113 Cal. años AP, después de la fusión de una barrera de hielo que existía durante el avance glacial antes. Esto dio lugar al desarrollo de un sistema hidrológico fluvio-lacustre complejo que persiste hasta nuestros días. Palabras clave: Patagonia, último máximo glacial, Younger Dryas, trombolitos. RESUMEN. Un grupo de morrenas glaciales estan Distribuidas desde el margen Este de la cuenca de drenaje de Torres del Paine Hacia el margen real de los Campos de Hielo Patagónicos. Las morrenas se observan en conjunto con las Naciones Unidas Grupo de terrazas Lacustres Regionales, las Cuales estan vinculadas y una las fluctuaciones glaciales. La geomorfología y Evidencias de sedimentos Lacustres indicano la existence De unico ONU lago proglacial, referido En Este Estudio de Como Gran Paleolago Tehuelche. Este Concepto ayuda a clarificar la cronología de los eventos glaciales y permite Una mejor Comprensión de la Evolución del Sistema hidrológico del sector de Torres del Paine. Los eventos glaciales, previamente Referidos Como Avance A, B y C, ocurrieron Durante el Último Máximo Glacial y alimentaron con Aguas de fusión al Gran Paleolago Tehuelche, permitiéndole Alcanzar su alcalde extensión. El Descubrimiento de trombolitos en Laguna Amarga sugiere Que El desagüe del paleolago Ocurrió Hace 7.113 Cal. Por años AP el Seno de Última Esperanza, producto de la fusión De Una barrera glaciar existente Durante los Avances glaciales Anteriores. LUEGO del drenaje sí Desarrollo en Un complejo Sistema hidrológico Que Persiste Hasta el presente. Palabras clave: Patagonia, Último Máximo Glacial, Dryas Temprano, Trombolitos.http://ref.scielo.org/wgc2q

A comperative study of different techniques for microstructural characterization of iol extended thermoplastic elastomer blends

This paper gives a relative comparison of different microscopic methods that are presently used to visualize polymer blend morphologies, versus the possibility to visualize the three-dimensional structure of the blends with electron tomography. Oil extended thermoplastic elastomer (TPE) blends based on a high amount of rubber phase and low amount of isotactic polypropylene (PP) were used as samples for this study. Low voltage scanning electron microscopy (LVSEM) and transmission electron microscopy (TEM) proved to be far superior to conventional scanning electron microscopy (SEM) and atomic force microscopy (AFM) for obtaining good quality images of the morphology of these blends. In an attempt to visualize the 3D morphology, electron tomography was carried out on these blends and models of the 3D morphologies were constructed. The usefulness of the different microscopic techniques in providing complementary morphological information and the potential of electron tomography as a new tool for constructing 3D-models of polymer blends are highlighted

Insecta, Ephemeroptera, Baetidae: Range extensions and new state records from Kansas, U.S.A.

Non

Design, synthesis, docking studies and monoamine oxidase inhibition of a small library of 1-acetyl- and 1-thiocarbamoyl-3,5-diphenyl-4,5-dihydro-(1h)-pyrazoles

New N-acetyl/N-thiocarbamoylpyrazoline derivatives were designed and synthesized in high yields to assess their inhibitory activity and selectivity against human monoamine oxidase A and B. The most important chiral compounds were separated into their single enantiomers and tested. The impact of the substituents at N1, C3 and C5 positions as well the influence of the configuration of the C5 on the biological activity were analyzed. Bulky aromatic groups at C5 were not tolerated. p-Prenyloxyaryl moiety at C3 oriented the selectivity toward the B isoform. The results were also corroborated by molecular modelling studies providing new suggestions for the synthesis of privileged structures to serve as lead compounds for the treatment of mood disorders and neurodegenerative diseases

Exploring financial literacy education strategies based on small- and micro-enterprise business practices

Purpose: This study explored the nature of business practices of small- and micro-enterprises within the South African context to propose recommendations for financial literacy education strategies. Design/methodology/approach: The data collection technique used for this qualitative study included semi-structured in-depth interviews with a case study of 10 small- and micro-enterprise owners who collectively trade within five of the nine South African provinces. Findings/results: Small- and micro-enterprises do not need to differ significantly because the respective business practice themes identified are relevant within both contexts. Both category enterprises make use of a cash basis system, generally have inventory management systems in place and do not have sophisticated financial planning practices. The micro-enterprises studied do not have business plans or accurate pricing strategies and cash management is a concern. The small-enterprise participants generally did not show interest in competitors and their enterprises had more sophisticated bookkeeping practices in place than micro-enterprises. Practical implications: Financial literacy education strategies for the owners should focus on providing guidance on tax matters, significance of business plans and how to prepare them, debtors management strategies, inventory management strategies, and a basic bookkeeping system that evolves from the cash basis of accounting to the accrual basis of accounting. It should also aim to educate owners on the importance of financial planning and risk management. Originality/value: This research provides an evidence-based description of the characteristics of South African small- and micro-enterprises, which could prove valuable in developing future owner financial literacy education programmes as well as other support strategies targeted at this audience.</p

A New Oriental Species of Behningia Lestage (Ephemeroptera: Behningiidae)

A new species of primitive tuskless burrowing mayflies (Ephemeroptera: Palpotarsa: Behningiidae), Behningia baei, new species, is described from larvae taken in Thailand. The new species is differentiated from congeners primarily by its labial palps, labrum, and base of the mid legs. It is the first species of the genus Behningia, and only the second species of the family Behningiidae, to be taken from the Oriental biogeographic region. Larvae previously regarded as B. tshernovae Edmunds and Traver are considered to be assignable to B. lestagei Motas and Bacesco

4-(3-Nitrophenyl)thiazol-2-ylhydrazone derivatives as antioxidants and selective hMAO-B inhibitors: synthesis, biological activity and computational analysis

A new series of 4-(3-nitrophenyl)thiazol-2-ylhydrazone derivatives were designed, synthesised, and evaluated to assess their inhibitory effect on the human monoamine oxidase (hMAO) A and B isoforms. Different (un)substituted (hetero)aromatic substituents were linked to N1 of the hydrazone in order to establish robust structure–activity relationships. The results of the biological testing demonstrated that the presence of the hydrazothiazole nucleus bearing at C4 a phenyl ring functionalised at the meta position with a nitro group represents an important pharmacophoric feature to obtain selective and reversible human MAO-B inhibition for the treatment of neurodegenerative disorders. In addition, the most potent and selective MAO-B inhibitors were evaluated in silico as potential cholinesterase (AChE/BuChE) inhibitors and in vitro for antioxidant activities. The results obtained from molecular modelling studies provided insight into the multiple interactions and structural requirements for the reported MAO inhibitory properties

Conservative management of breast cancer in the elderly in a developing country

<p>Abstract</p> <p>Background</p> <p>The cost effective treatment of cancer in developing countries remains challenging. In the elderly with possible limited life expectancy, the health expenditure associated with standard treatment regimes should be carefully considered. We present the results of conservative management of breast cancer in the aged in a resource-limited environment.</p> <p>Methods</p> <p>Patients aged 70 or older with early breast cancer were treated with tumour excision or simple mastectomy and adjuvant tamoxifen. The records of patients presenting to the Breast Unit between January 1990 and December 2004 were retrieved and demographic, clinical, pathological and oncological data were reviewed. Survival statistics were calculated using the life table method.</p> <p>Results</p> <p>A total of 483 patients above 70 years of age were identified. One hundred and eighty eight patients were managed according to the conservative protocol. Forty-one had a simple mastectomy and 147 tumour excision. Their mean age was 77.3 years. The mean follow-up is 62 months. Thirty-one patients (16.4%) were not compliant with tamoxifen use. TNM staging was 0 in 4 patients, I in 42 patients, II in 116 patients and III in 26 patients. There was no 30-day mortality. The cumulative incidence of local recurrence was 3.3% at 5 and 10 years. The cumulative incidence of regional recurrence was 3.3% at 5 years and 4.5% at 10 years. The cumulative incidence of distant recurrence was 6.2% at 5 years and 12.2% at 10 years. The cumulative overall, disease specific and disease free survival at 10 years was 59%, 88% and 81% respectively.</p> <p>Conclusion</p> <p>Limited surgery and tamoxifen provide excellent control of breast cancer in the elderly in a resource restricted environment. Radiotherapy and axillary dissection and can be safely omitted thereby reducing health care resource utilization.</p