Regular maps of high density

A regular map is a surface together with an embedded graph, having properties similar to those of the surface and graph of a platonic solid. We analyze regular maps with reflection symmetry and a graph of density strictly exceeding 1/2, and we conclude that all regular maps of this type belong to a family of maps naturally defined on the Fermat curves x^n+y^n+z^n=0, excepting the one corresponding to the tetrahedron.Comment: 13 pages, 4 figure

Staging of cutaneous melanoma

The American Joint Committee on Cancer (AJCC) staging of cutaneous melanoma is a continuously evolving system. The identification of increasingly more accurate prognostic factors has led to major changes in melanoma staging over the years, and the current system described in this review will likely be modified in the near future. Likewise, application of new imaging techniques has also changed the staging work-up of patients with cutaneous melanoma. Chest and abdominal computed tomography (CT) scanning is most commonly used for evaluation of potential metastatic sites in the lungs, lymph nodes and liver, and is indicated in patients with new symptoms, anaemia, elevated lactate dehydrogenase or a chest X-ray abnormality. CT scans should be restricted to patients with high-risk melanoma (stage IIC, IIIB, IIIC and stage IIIA with a macroscopic sentinel lymph node). Magnetic resonance imaging (MRI) of the brain is a mandatory test in patients with stage IV, optional in stage III and not used in patients with stage I and II disease. Positron emission tomography (PET)/CT is more accurate than CT or MRI alone in the diagnosis of metastases and should complement conventional CT/MRI imaging in the staging work-up of patients who have solitary or oligometastatic disease where surgical resection is most relevant

Isolated limb perfusion with actinomycin D and TNF-alpha results in improved tumour response in soft-tissue sarcoma-bearing rats but is accompanied by severe local toxicity

Previously we demonstrated that addition of Tumour Necrosis Factor-α to melphalan or doxorubicin in a so-called isolated limb perfusion results in synergistic antitumour responses of sarcomas in both animal models and patients. Yet, 20 to 30% of the treated tumours do not respond. Therefore agents that synergise with tumour necrosis factor alpha must be investigated. Actinomycin D is used in combination with melphalan in isolated limb perfusion in the treatment of patients with melanoma in-transit metastases and is well known to augment tumour cell sensitivity towards tumour necrosis factor alpha in vitro. Both agents are very toxic, which limits their systemic use. Their applicability may therefore be tested in the isolated limb perfusion setting, by which the tumours can be exposed to high concentrations in the absence of systemic exposure. To study the beneficial effect of the combination in vivo, BN-175 soft tissue sarcoma-bearing rats were perfused with various concentrations of actinomycin D and tumour necrosis factor alpha. When used alone the drugs had only little effect on the tumour. Only when actinomycin D and tumour necrosis factor alpha were combined a tumour response was achieved. However, these responses were accompanied by severe, dose limiting, local toxicity such as destruction of the muscle tissue and massive oedema. Our results show that isolated limb perfusion with actinomycin D in combination with tumour necrosis factor alpha leads to a synergistic anti-tumour response but also to idiosyncratic locoregional toxicity to the normal tissues. Actinomycin D, in combination with tumour necrosis factor alpha, should not be explored in the clinical setting because of this. The standard approach in the clinic remains isolated limb perfusion with tumour necrosis factor alpha in combination with melphalan

Comparison of LFP-Based and Spike-Based Spectro-Temporal Receptive Fields and Cross-Correlation in Cat Primary Auditory Cortex

Multi-electrode array recordings of spike and local field potential (LFP) activity were made from primary auditory cortex of 12 normal hearing, ketamine-anesthetized cats. We evaluated 259 spectro-temporal receptive fields (STRFs) and 492 frequency-tuning curves (FTCs) based on LFPs and spikes simultaneously recorded on the same electrode. We compared their characteristic frequency (CF) gradients and their cross-correlation distances. The CF gradient for spike-based FTCs was about twice that for 2–40 Hz-filtered LFP-based FTCs, indicating greatly reduced frequency selectivity for LFPs. We also present comparisons for LFPs band-pass filtered between 4–8 Hz, 8–16 Hz and 16–40 Hz, with spike-based STRFs, on the basis of their marginal frequency distributions. We find on average a significantly larger correlation between the spike based marginal frequency distributions and those based on the 16–40 Hz filtered LFP, compared to those based on the 4–8 Hz, 8–16 Hz and 2–40 Hz filtered LFP. This suggests greater frequency specificity for the 16–40 Hz LFPs compared to those of lower frequency content. For spontaneous LFP and spike activity we evaluated 1373 pair correlations for pairs with >200 spikes in 900 s per electrode. Peak correlation-coefficient space constants were similar for the 2–40 Hz filtered LFP (5.5 mm) and the 16–40 Hz LFP (7.4 mm), whereas for spike-pair correlations it was about half that, at 3.2 mm. Comparing spike-pairs with 2–40 Hz (and 16–40 Hz) LFP-pair correlations showed that about 16% (9%) of the variance in the spike-pair correlations could be explained from LFP-pair correlations recorded on the same electrodes within the same electrode array. This larger correlation distance combined with the reduced CF gradient and much broader frequency selectivity suggests that LFPs are not a substitute for spike activity in primary auditory cortex

Factors Influencing Prognosis After Initial Inadequate Excision (IIE) for Soft Tissue Sarcoma

Purpose. The influence of initial inadequate excision (IIE) of soft tissue sarcoma (STS) on local control and overall survival is not well established. It is generally believed that an IIE may have a negative impact on both, despite subsequent treatment by radical surgery and radiotherapy. However, data on local recurrence-free survival/overall survival are conflicting and there are no data on the effect of IIE on overall survival

Biomarkers in melanoma

Biomarkers are tumour- or host-related factors that correlate with tumour biological behaviour and patient prognosis. High-throughput analytical techniques--DNA and RNA microarrays--have identified numerous possible biomarkers, but their relevance to melanoma progression, clinical outcome and the selection of optimal treatment strategies still needs to be established. The review discusses a possible molecular basis for predictive tissue biomarkers such as melanoma thickness, ulceration and mitotic activity, and provides a list of promising new biomarkers identified from tissue microarrays that needs confirmation by independent, prospectively collected clinical data sets. In addition, common predictive serum biomarkers--lactate dehydrogenase, S100B and melanoma-inhibiting activity--as well as selected investigational serum biomarkers such as TA90IC and YKL-40 are also reviewed. A more accurate, therapeutically predictive classification of human melanomas and selection of patient populations that would profit from therapeutic interventions are among the major challenges expected to be addressed in the futur

Independent Set Reconfiguration in Cographs

We study the following independent set reconfiguration problem, called TAR-Reachability: given two independent sets $I$ and $J$ of a graph $G$, both of size at least $k$, is it possible to transform $I$ into $J$ by adding and removing vertices one-by-one, while maintaining an independent set of size at least $k$ throughout? This problem is known to be PSPACE-hard in general. For the case that $G$ is a cograph (i.e. $P_4$-free graph) on $n$ vertices, we show that it can be solved in time $O(n^2)$, and that the length of a shortest reconfiguration sequence from $I$ to $J$ is bounded by $4n-2k$, if such a sequence exists. More generally, we show that if $X$ is a graph class for which (i) TAR-Reachability can be solved efficiently, (ii) maximum independent sets can be computed efficiently, and which satisfies a certain additional property, then the problem can be solved efficiently for any graph that can be obtained from a collection of graphs in $X$ using disjoint union and complete join operations. Chordal graphs are given as an example of such a class $X$