The Advantage of Standing Up to Fight and the Evolution of Habitual Bipedalism in Hominins

BACKGROUND: Many quadrupedal species stand bipedally on their hindlimbs to fight. This posture may provide a performance advantage by allowing the forelimbs to strike an opponent with the range of motion that is intrinsic to high-speed running, jumping, rapid braking and turning; the range of motion over which peak force and power can be produced. METHODOLOGY/PRINCIPAL FINDINGS: To test the hypothesis that bipedal (i.e., orthograde) posture provides a performance advantage when striking with the forelimbs, I measured the force and energy produced when human subjects struck from "quadrupedal" (i.e., pronograde) and bipedal postures. Downward and upward directed striking energy was measured with a custom designed pendulum transducer. Side and forward strikes were measured with a punching bag instrumented with an accelerometer. When subjects struck downward from a bipedal posture the work was 43.70±12.59% (mean ± S.E.) greater than when they struck from a quadrupedal posture. Similarly, 47.49±17.95% more work was produced when subjects struck upward from a bipedal stance compared to a quadrupedal stance. Importantly, subjects did 229.69±44.19% more work in downward than upward directed strikes. During side and forward strikes the force impulses were 30.12±3.68 and 43.04±9.00% greater from a bipedal posture than a quadrupedal posture, respectively. CONCLUSIONS/SIGNIFICANCE: These results indicate that bipedal posture does provide a performance advantage for striking with the forelimbs. The mating systems of great apes are characterized by intense male-male competition in which conflict is resolved through force or the threat of force. Great apes often fight from bipedal posture, striking with both the fore- and hindlimbs. These observations, plus the findings of this study, suggest that sexual selection contributed to the evolution of habitual bipedalism in hominins

Cancer Biomarker Discovery: The Entropic Hallmark

Background: It is a commonly accepted belief that cancer cells modify their transcriptional state during the progression of the disease. We propose that the progression of cancer cells towards malignant phenotypes can be efficiently tracked using high-throughput technologies that follow the gradual changes observed in the gene expression profiles by employing Shannon's mathematical theory of communication. Methods based on Information Theory can then quantify the divergence of cancer cells' transcriptional profiles from those of normally appearing cells of the originating tissues. The relevance of the proposed methods can be evaluated using microarray datasets available in the public domain but the method is in principle applicable to other high-throughput methods. Methodology/Principal Findings: Using melanoma and prostate cancer datasets we illustrate how it is possible to employ Shannon Entropy and the Jensen-Shannon divergence to trace the transcriptional changes progression of the disease. We establish how the variations of these two measures correlate with established biomarkers of cancer progression. The Information Theory measures allow us to identify novel biomarkers for both progressive and relatively more sudden transcriptional changes leading to malignant phenotypes. At the same time, the methodology was able to validate a large number of genes and processes that seem to be implicated in the progression of melanoma and prostate cancer. Conclusions/Significance: We thus present a quantitative guiding rule, a new unifying hallmark of cancer: the cancer cell's transcriptome changes lead to measurable observed transitions of Normalized Shannon Entropy values (as measured by high-throughput technologies). At the same time, tumor cells increment their divergence from the normal tissue profile increasing their disorder via creation of states that we might not directly measure. This unifying hallmark allows, via the the Jensen-Shannon divergence, to identify the arrow of time of the processes from the gene expression profiles, and helps to map the phenotypical and molecular hallmarks of specific cancer subtypes. The deep mathematical basis of the approach allows us to suggest that this principle is, hopefully, of general applicability for other diseases

Thigh-length compression stockings and DVT after stroke

Controversy exists as to whether neoadjuvant chemotherapy improves survival in patients with invasive bladder cancer, despite randomised controlled trials of more than 3000 patients. We undertook a systematic review and meta-analysis to assess the effect of such treatment on survival in patients with this disease

Hedge, redução de volatilidade dos lucros e o efeito sobre o imposto de renda das companhias abertas brasileiras

Neste artigo, procurou-se identificar se as companhias abertas brasileiras teriam conseguido benefícios fiscais ao fazer hedge, fato esse derivado de uma expectativa de queda da sua carga tributária (Imposto de Renda a pagar). Com esse objetivo, inicialmente pesquisou-se em que situações have-ria possibilidade de geração desse benefício. Após essa revisão, foram estudadas situações em que a companhia tivesse grande volatilidade de seus resultados e os efeitos que o hedge traria no valor do I.R. a ser pago. Assim, pôde-se mensurar o efeito do resultado do hedge na carga tributária dessas companhias nesse período, simulando uma situação teórica para melhor evidenciarem-se os efeitos resultantes dessa prática. Posteriormente, utilizouse uma regressão linear múltipla para relacionar o valor do imposto de renda pago por companhias abertas brasileiras no ano de 2003 com os valores de hedge em 2002 e 2003 e os prejuízos acumulados em 2002. Os resultados são fundamentados em vasta bibliografia referente ao assunto.<br>In this article we try to identify if Brazilian public companies hedge in response to tax incentives. With this goal, we first identify in which conditions the hedge causes reductions in tax obligations. Next, we study theoretical situations in which the companies' financial results change from great losses to great profits and we observe the impact in the companies' tax liabilities. Finally, we observe the results of a regression that tries to explain the tax obligations in 2003 in function of the hedge values in 2002, 2003 and the net operational losses in 2002. We conclude that it is possible to hedge in response to tax benefits in some special situations. Our results and conclusions are supported by other studies