Bak-Sneppen backwards

We study the backwards Markov chain for the Bak–Sneppen model of biological evolution and derive its corresponding reversibility equations. We show that, in contrast to the forwards Markov chain, the dynamics of the backwards chain explicitly involve the stationary distribution of the model, and from this we derive a functional equation that the stationary distribution must satisfy. We use this functional equation to derive differential equations for the stationary distribution of Bak–Sneppen models in which all but one or all but two of the fitnesses are replaced at each step, subject to certain conditions on the relative locations of the replaced species. This gives a unified way of deriving Schlemm’s expressions for the stationary distributions of the isotropic four-species model, the isotropic five-species model, and the anisotropic three-species model

Bak-Sneppen backwards

We study the backwards Markov chain for the Bak–Sneppen model of biological evolution and derive its corresponding reversibility equations. We show that, in contrast to the forwards Markov chain, the dynamics of the backwards chain explicitly involve the stationary distribution of the model, and from this we derive a functional equation that the stationary distribution must satisfy. We use this functional equation to derive differential equations for the stationary distribution of Bak–Sneppen models in which all but one or all but two of the fitnesses are replaced at each step, subject to certain conditions on the relative locations of the replaced species. This gives a unified way of deriving Schlemm’s expressions for the stationary distributions of the isotropic four-species model, the isotropic five-species model, and the anisotropic three-species model

Multiple right-sided pulmonary nodules: metastatic cancer or resectable early stage tumor?

The aim of this paper is to focus attention on complex cases of lung disease that may benefit from being managed outside formal guidelines. A 52 year-old man who had previously undergone a laryngectomy for squamous cell carcinoma, presented with a 1.2 cm nodule in the right upper pulmonary lobe. Three months later a new CT scan found that the nodule had slightly increased in size and also detected two new smaller nodules in the middle lobe. A PET/CT scan showed metabolic hyperactivity of all nodules. Since needle aspiration of the upper one revealed malignant cells, the patient was considered to be suffering from metastatic cancer and started on chemotherapy. At follow-up both CT and PET scans found a significant reduction in volume and activity of the lower nodules but no change in the upper one. At diagnostic thoracoscopy, histology demonstrated that the upper nodule was an adenocarcinoma while the lower ones were inflammatory. An upper lobectomy and systematic nodal dissection were therefore performed. Histology established a diagnosis of upper pulmonary adenocarcinoma and sarcoidosis. Our report suggests that in complicated oncologic cases in which non-invasive diagnostic tools yield incongruous results surgery should be considered without delay

The role of the cytoskeleton in capacitaftive calcium entry in myenteric glia

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/73680/1/j.1365-2982.2003.00406.x.pd

Hyperthermia and Thermosensitive Liposomes for Improved Delivery of Chemotherapeutic Drugs to Solid Tumors

Lipid-based nanocarriers or liposomes have been proven successful in the delivery of chemotherapeutic agents and are currently applied clinically in the treatment of various types of cancer. Liposomes offer the advantage of a high drug payload, decreased drug toxicity and enhanced drug accumulation at tumor sites. Increased accumulation is due to the relatively leaky tumor vasculature that allows liposome extravasation. Between different types of tumors and even within one tumor, vascular permeability and thus liposome extravasation may differ greatly. Furthermore, upon accumulation of liposomes in the tumor area, drug bioavailability is not guaranteed. At present, these are the major issues for clinically used liposomal drugs

A meta-analysis of long-term effects of conservation agriculture on maize grain yield under rain-fed conditions

Conservation agriculture involves reduced tillage, permanent soil cover and crop rotations to enhance soil fertility and to supply food from a dwindling land resource. Recently, conservation agriculture has been promoted in Southern Africa, mainly for maize-based farming systems. However, maize yields under rain-fed conditions are often variable. There is therefore a need to identify factors that influence crop yield under conservation agriculture and rain-fed conditions. Here, we studied maize grain yield data from experiments lasting 5 years and more under rain-fed conditions. We assessed the effect of long-term tillage and residue retention on maize grain yield under contrasting soil textures, nitrogen input and climate. Yield variability was measured by stability analysis. Our results show an increase in maize yield over time with conservation agriculture practices that include rotation and high input use in low rainfall areas. But we observed no difference in system stability under those conditions. We observed a strong relationship between maize grain yield and annual rainfall. Our meta-analysis gave the following findings: (1) 92% of the data show that mulch cover in high rainfall areas leads to lower yields due to waterlogging; (2) 85% of data show that soil texture is important in the temporal development of conservation agriculture effects, improved yields are likely on well-drained soils; (3) 73% of the data show that conservation agriculture practices require high inputs especially N for improved yield; (4) 63% of data show that increased yields are obtained with rotation but calculations often do not include the variations in rainfall within and between seasons; (5) 56% of the data show that reduced tillage with no mulch cover leads to lower yields in semi-arid areas; and (6) when adequate fertiliser is available, rainfall is the most important determinant of yield in southern Africa. It is clear from our results that conservation agriculture needs to be targeted and adapted to specific biophysical conditions for improved impact

Ten Simple Rules for Organizing an Unconference

This is an open access article distributed under the terms of the Creative Commons Attribution License.Peer Reviewe

Combination therapy with irinotecan and cisplatin as neoadjuvant chemotherapy in locally advanced cervical cancer

To evaluate the response rate and toxicity of the combination of irinotecan (CPT-11) and cisplatin in a neoadjuvant setting, a phase II study was conducted regarding the regimen of this combination in patients with locally advanced cervical cancer. Eligibility included patients with previously untreated stage Ib2, IIb, or IIIb squamous cell carcinoma with good performance status. CPT-11 (60 mg m−2) was administered intravenously on days 1, 8 and 15, followed by cisplatin (60 mg m−2) given intravenously on day 1. Treatment was repeated every 4 weeks for a total of two or three cycles. Among 23 eligible patients (median age: 59 years), three showed complete response (13%), 15 showed partial response (65%), for an overall response rate of 78% (95% confidence interval 58–90%). Stable disease was observed in four cases (17%) and progressive disease in one (4%). The median time to failure and median survival time have not yet been reached. Of the 52 treatment cycles administered, diarrhoea and grade 3 or 4 neutropenia were observed in 10% and 75% respectively. There were no therapy-related deaths. The combination of CPT-11 with cisplatin is a promising regimen for neoadjuvant chemotherapy in locally advanced cervical cancer. The toxicities of this regimen are well tolerated. © 1999 Cancer Research Campaig