A Logistic Model of Periodic Chemotherapy

A logistic differential equation with a time-varying periodic parameter is used to model the growth of cells, in particular cancer cells, in the presences of chemotherapeutic drugs. The chemotherapeutic effects are modeled by a periodic parameter that modifies the growth rate of the cell tissue. A negative growth rate represents the detrimental effects of the drugs. A simple criterion is obtained for the behavior of the chemotherapy

A Mathematical Model of Cycle Chemotherapy

A mathematical model is used to discuss the effects of cycle-specific chemotherapy. The model includes a constraint equation which describes the effects of the drugs on sensitive normal tissue such as bone marrow. This model investigates both pulsed and piecewise-continuous chemotherapeutic effects and calculates the parameter regions of acceptable dose and period. It also identifies the optimal period needed for maximal tumor reduction. Examples are included concerning the use of growth factors and how they can enhance the cell kill of the chemotherapeutic drugs

Skeleton weed : how serious a threat in Western Australia?

Skeleton weed is probably the most serious weed ever to threaten the Australian wheat industry. It interferes with wheat cropping at two stages: through competition with the growing crop, particularly for nitrogen and water during the crop\u27s development: and later through the production of a tall, wiry flowering stem which tangles in harvesting machinery and can make harvesting difficult, if not impossible. The weed is a major problem in eastern Australia although a combination of cultural, chemical and biological control programmes is helping to reduce its impact. In Western Australia, skeleton weed is being contained mainly by eradication efforts. Weed Agronomy Research Officers, F.D. Panetta and J. Dodd, are studying the ecology of skeleton weed to determine why it hasn\u27t spread further and how current control methods can be more effectively applied

A Simple Mathematical-Model and Alternative Paradigm for Certain Chemotherapeutic Regimens

A simplified two-compartment model for cell-specific chemotherapy is analysed by reformulating the governing system of differential equations as a Schrodinger equation in time. With the choice of an exponentially decaying function representing the effects of chemotherapy on cycling tumor cells, the potential function V(t) is a Morse-type potential, well known in the quantum mechanical literature; and the solutions are obtainable in terms of confluent hypergeometric functions (or the related Whittaker functions). Because the chemotherapy is administered periodically, the potential V(t) is periodic also, and use is made of existing theory (Floquet theory) as applied to scattering by periodic potentials in the quantum theory of solids. Corresponding to the existence \u27\u27forbidden energy bands\u27\u27 in that context, it appears that there are \u27\u27forbidden\u27\u27 or inappropriate chemotherapeutic regimens also, in the sense that for some combinations of period, dosage, and cell parameters, no real solutions exist for the system of equations describing the time evolution of cancer cells in each compartment. A similar, but less complex phenomenon may occur for simpler mathematical representations of the regimen. The purpose of this paper is to identify the existence of this phenomenon, at least insofar as this model is concerned, and to examine the implications for clinical activities. This new paradigm, if structually stable (in the sense of the phenomenon occurring in more realistic models of chemotherapy) may be of considerable significance in identifying those regimens which are appropriate for effective chemotherapy, by providing a rational basis for such decisions, rather than by \u27\u27trial and error\u27\u27 (see the statement by Skipper [1] at the conclusion of this paper)

Measurement of the mass of the τ lepton

A data-driven energy scan in the immediate vicinity of the τ pair production threshold has been performed using the Beijing Spectrometer at the Beijing Electron-Positron Collider. Approximately 5 pb^(-1) of data, distributed over 12 scan points, have been collected. A previous mass value for the τ lepton, obtained using only the eμ final state, has been published. In this paper, the final BES result on the mass measurement is presented. The analysis is based on the combined data from the ee, eμ, eh, μμ, μh, and hh final states, where h denotes a charged π or K. A maximum likelihood fit to the τ pair production cross section data yields the value m_τ=1776.96_(-0.21)-0.17^(+0.18+0.25) MeV

Direct measurement of B(D_s^+ → φX^+)

The absolute inclusive branching fraction of D_s^+→φX^+ has been measured from data collected by the BES detector at a center-of-mass energy of 4.03 GeV, corresponding to an integrated luminosity of 22.3 pb^(-1). At this energy, direct pair production e^+e^-→D_s^+D_s^- has been observed. We have selected D_s candidate events by reconstructing five hadronic decay modes D_s^+→φπ^+, K^(0*)K^+, K^0K^+, f0^(π+) and K^0K^-π^+π^+ and have searched for inclusive φ’s in the recoiling D_s^-. We observed three recoiling φ’s in the 166.4 ± 31.8 D_s candidate events, which leads to the absolute branching fraction B(D_s^+→φX^+)=(17.8(-7.2 -6.3)^(+15.1+0.6)) % and B(D_s-6.3+→φπ-6.3+)=(3.6_(-1.6 -1.3)(^_3.1+0.4) %. [S0556-2821(97)02423-5

Measurement of the mass of the τ lepton

The mass of the τ lepton has been measured at the Beijing Electron-Positron Collider using the Beijing Spectrometer. A search near threshold for e^+e^-→τ^+τ^- was performed. Candidate events were identified by requiring that one τ decay via τ→eνν¯, and the other via τ→μνν¯. The mass value, obtained from a fit to the energy dependence of the τ^+τ^- cross section, is m_τ=1776.9_(-0.5)^(+0.4)±0.2 MeV

Percutaneous Management of a Long Saphenous Vein Graft Aneurysm: A Case Report and Review of Literature

Aneurysms of saphenous vein grafts are rare but can result in complications such as myocardial infarction or death. Percutaneous treatment has included a variety of approaches, including covered stents. Long aneurysms in saphenous vein grafts pose an additional challenge due to the lack of coronary covered stents with sufficient length. We present successful treatment of a long saphenous vein graft aneurysm with use of peripheral covered stents over two coronary guidewires, a 55-centimeter 8-French sheath and no guide catheter