Ant-inspired density estimation via random walks.

Many ant species use distributed population density estimation in applications ranging from quorum sensing, to task allocation, to appraisal of enemy colony strength. It has been shown that ants estimate local population density by tracking encounter rates: The higher the density, the more often the ants bump into each other. We study distributed density estimation from a theoretical perspective. We prove that a group of anonymous agents randomly walking on a grid are able to estimate their density within a small multiplicative error in few steps by measuring their rates of encounter with other agents. Despite dependencies inherent in the fact that nearby agents may collide repeatedly (and, worse, cannot recognize when this happens), our bound nearly matches what would be required to estimate density by independently sampling grid locations. From a biological perspective, our work helps shed light on how ants and other social insects can obtain relatively accurate density estimates via encounter rates. From a technical perspective, our analysis provides tools for understanding complex dependencies in the collision probabilities of multiple random walks. We bound the strength of these dependencies using local mixing properties of the underlying graph. Our results extend beyond the grid to more general graphs, and we discuss applications to size estimation for social networks, density estimation for robot swarms, and random walk-based sampling for sensor networks.

Costs of task allocation with local feedback: Effects of colony size and extra workers in social insects and other multi-agent systems.

Adaptive collective systems are common in biology and beyond. Typically, such systems require a task allocation algorithm: a mechanism or rule-set by which individuals select particular roles. Here we study the performance of such task allocation mechanisms measured in terms of the time for individuals to allocate to tasks. We ask: (1) Is task allocation fundamentally difficult, and thus costly? (2) Does the performance of task allocation mechanisms depend on the number of individuals? And (3) what other parameters may affect their efficiency? We use techniques from distributed computing theory to develop a model of a social insect colony, where workers have to be allocated to a set of tasks; however, our model is generalizable to other systems. We show, first, that the ability of workers to quickly assess demand for work in tasks they are not currently engaged in crucially affects whether task allocation is quickly achieved or not. This indicates that in social insect tasks such as thermoregulation, where temperature may provide a global and near instantaneous stimulus to measure the need for cooling, for example, it should be easy to match the number of workers to the need for work. In other tasks, such as nest repair, it may be impossible for workers not directly at the work site to know that this task needs more workers. We argue that this affects whether task allocation mechanisms are under strong selection. Second, we show that colony size does not affect task allocation performance under our assumptions. This implies that when effects of colony size are found, they are not inherent in the process of task allocation itself, but due to processes not modeled here, such as higher variation in task demand for smaller colonies, benefits of specialized workers, or constant overhead costs. Third, we show that the ratio of the number of available workers to the workload crucially affects performance. Thus, workers in excess of those needed to complete all tasks improve task allocation performance. This provides a potential explanation for the phenomenon that social insect colonies commonly contain inactive workers: these may be a 'surplus' set of workers that improves colony function by speeding up optimal allocation of workers to tasks. Overall our study shows how limitations at the individual level can affect group level outcomes, and suggests new hypotheses that can be explored empirically.

Randomized and prospective trial comparing tract creation using plasma vaporization with balloon dilatation in percutaneous nephrolithotomy.

UNLABELLED: WHAT'S KNOWN ON THE SUBJECT? AND WHAT DOES THE STUDY ADD?: Use of balloon dilatation leads to less blood transfusion rates than metallic dilators. Plasma vaporization leads to less blood loss than balloon dilatation in this study. The study evaluates a novel technique for the creation of a nephrostomy tract for PCNL. Compared with other techniques, plasma vaporization is a safer procedure that causes lesser blood loss, requires a shorter hospital stay, causes less radiation exposure, and enables easier nephrostomy tract creation for PCNL. OBJECTIVE: To evaluate the efficacy and safety of plasma vaporization for tract creation in percutaneous nephrolithotomy (PCNL). PATIENTS AND METHODS: In this randomized prospective trial we enrolled 65 patients and assigned each to one of two groups: 33 patients were randomly scheduled to undergo plasma vaporization and 32 were scheduled to undergo balloon dilatation for tract creation. A bipolar resectoscope mounted with a plasma vaporization button electrode or a traditional balloon dilator were used to create the nephrostomy tract. RESULTS: The mean blood loss, mean length of hospital stay and mean operating time, stone-free rates and postoperative complications in the two groups were compared using the t-test or chi-squared test (Fisher's exact test). The plasma vaporization group had a significantly lower mean (SD) decrease in haematocrit level (3.5 [2.8]% vs 6.6 [3.3]%; P = 0.02) and a shorter mean (SD) hospital stay (2.6 [1.2] days vs 5.3 [3.4] days; P = 0.0). There were no significant differences in the operating time, stone-free rate or cases of postoperative fever between the two groups. CONCLUSION: The plasma vaporization technique is safe, leads to less blood loss than the other techniques, and is a simple solution for creating the nephrostomy tract for PCNL.

Adenosquamous carcinoma arising from a thyroglossal duct cyst: A case report.

The current study describes a case of adenosquamous carcinoma originating from a thyroglossal duct cyst (TGDC). A 77-year-old man presented with an asymptomatic mass in the left mid-neck, which was soft and mobile on palpation. Fine-needle aspiration was performed, but cytology did not detect any malignant cells. Computed tomography demonstrated a single cystic lesion in the left lobe of the thyroid gland; therefore, surgery was performed on the suspected thyroid cyst. However, it was identified intraoperatively that the lesion was separated from the thyroid gland and instead adhered to an additional hyoid bone; therefore, the Sistrunk procedure was performed. Histopathological examination of the resected tumor confirmed the diagnosis of adenosquamous carcinoma originating from a TGDC. Carcinoma arising from a TGDC is rare, and accounts for 1% of all TGDC cases. The most common subtype of carcinoma associated with TGDC is papillary carcinoma, whilst adenosquamous carcinoma developing from a TGDC is extremely rare, with only one case currently reported in the literature. Although a consensus for the management of this disease has not yet been established, adequate surgical excision with long-term follow-up is currently the preferred treatment.

The preliminary experiences of translocation renal cell carcinoma and literature review.

Xp11.2 translocation renal cell carcinoma (RCC) is rare and predominantly found in children and young adults. Because of the property of overexpressed transcription factor E3 (TFE3) fusion protein, immunohistochemical (IHC) staining with TFE3 antibody makes an excellent diagnostic tool. This study analyzed preliminary experiences of eight Xp11.2 translocation RCCs in our institution between 2007 and 2012. In four males and four females with a mean age of 28.4 years. Xp11.2 translocation RCCs were diagnosed. TFE3 IHC stain was positive in all tumor specimens. As the initial presentation, four patients suffered from abdominal pain, three cases had gross hematuria, and one case had hemoptysis caused by existing lung metastasis. The tumor was located in the right kidney (75%) with mean diameter of 5.85 ± 2.64 cm. Three cases (38%, 3/8) presented with lymph node metastasis at the time of diagnosis. In five cases (63%, 5/8), the initial diagnosis was Stage III and IV. Treatment included open surgery (one partial nephrectomy and five radical nephrectomies), cryoablation, immunotherapy, and target therapy. The mean follow-up time was 32 months. One patient died after 23.4 months of follow-up. The application of TFE3 IHC stain will improve the diagnostic accuracy for detecting XP11.2 translocation renal cell carcinoma. Surgery or cryoablation both had excellent prognosis in early stages. Although the disease is believed to be indolent, an increasingly aggressive clinical course should be kept in mind, especially for children and young adults.