Linear Cellular Arrays Research Articles

Reticular and microcystic schwannoma of the parotid gland

Background Microcystic/reticular variant of schwannoma is a rare, distinctive variant of schwannoma with predilection for visceral sites. Fewer than 20 cases are described in the literature and involvement of head and neck has not previously been reported. Microcystic/reticular variant of schwannoma demonstrates similar biological behaviour to usual schwannoma and should be distinguished from parotid gland tumours that may recur aggressively if incompletely excised. Aim To present a case of microcystic/reticular variant of schwannoma in the parotid gland with literature review and discuss pertinent differential diagnoses. Case report A 59-year-old female presented with a preauricular swelling. FNA showed cytologically bland spindle shaped cells amidst myxoid stroma. At operation, the tumour was found to be closely associated with facial nerve and was resected with nerve preservation. Histopathological examination showed a well circumscribed, unencapsulated lesion composed of slender, spindle shaped cells with intracytoplasmic vacuoles amidst myxoid stroma. Areas with accordion-like linear cellular arrays, reticular pattern and microcysts were present. Features of typical schwannoma, atypia, mitoses, or necrosis were absent. Diffuse immunor-eactivity with S100 was noted. Immunohistochemistry helped exclude differential diagnoses like myoepithelioma, pleomorphic adenoma, perineuroma, parachordoma, and epithelioid haemangio-endothelioma. Conclusion We present a case of microcystic/reticular variant of schwannoma in the head and neck, to our knowledge the first report of this entity in this location.

Reticular and microcystic schwannoma of the parotid gland

Background Microcystic/reticular variant of schwannoma is a rare, distinctive variant of schwannoma with predilection for visceral sites. Fewer than 20 cases are described in the literature and involvement of head and neck has not previously been reported. Microcystic/reticular variant of schwannoma demonstrates similar biological behaviour to usual schwannoma and should be distinguished from parotid gland tumours that may recur aggressively if incompletely excised. Aim To present a case of microcystic/reticular variant of schwannoma in the parotid gland with literature review and discuss pertinent differential diagnoses. Case report A 59-year-old female presented with a preauricular swelling. FNA showed cytologically bland spindle shaped cells amidst myxoid stroma. At operation, the tumour was found to be closely associated with facial nerve and was resected with nerve preservation. Histopathological examination showed a well circumscribed, unencapsulated lesion composed of slender, spindle shaped cells with intracytoplasmic vacuoles amidst myxoid stroma. Areas with accordion-like linear cellular arrays, reticular pattern and microcysts were present. Features of typical schwannoma, atypia, mitoses, or necrosis were absent. Diffuse immunor-eactivity with S100 was noted. Immunohistochemistry helped exclude differential diagnoses like myoepithelioma, pleomorphic adenoma, perineuroma, parachordoma, and epithelioid haemangio-endothelioma. Conclusion We present a case of microcystic/reticular variant of schwannoma in the head and neck, to our knowledge the first report of this entity in this location. Microcystic/reticular variant of schwannoma is a rare, distinctive variant of schwannoma with predilection for visceral sites. Fewer than 20 cases are described in the literature and involvement of head and neck has not previously been reported. Microcystic/reticular variant of schwannoma demonstrates similar biological behaviour to usual schwannoma and should be distinguished from parotid gland tumours that may recur aggressively if incompletely excised. To present a case of microcystic/reticular variant of schwannoma in the parotid gland with literature review and discuss pertinent differential diagnoses. A 59-year-old female presented with a preauricular swelling. FNA showed cytologically bland spindle shaped cells amidst myxoid stroma. At operation, the tumour was found to be closely associated with facial nerve and was resected with nerve preservation. Histopathological examination showed a well circumscribed, unencapsulated lesion composed of slender, spindle shaped cells with intracytoplasmic vacuoles amidst myxoid stroma. Areas with accordion-like linear cellular arrays, reticular pattern and microcysts were present. Features of typical schwannoma, atypia, mitoses, or necrosis were absent. Diffuse immunor-eactivity with S100 was noted. Immunohistochemistry helped exclude differential diagnoses like myoepithelioma, pleomorphic adenoma, perineuroma, parachordoma, and epithelioid haemangio-endothelioma. We present a case of microcystic/reticular variant of schwannoma in the head and neck, to our knowledge the first report of this entity in this location.

Massively parallel fault tolerant computations on syntactical patterns

The general capabilities of reliable computations in linear cellular arrays are investigated in terms of syntactical pattern recognition. We consider defects of the processing elements themselves and defects of their communication links. In particular, a processing element (cell) is assumed to behave as follows. Dependent on the result of a self-diagnosis it stores its working state locally such that it becomes visible to the neighbors. A defective cell cannot modify information but is able to transmit it unchanged with unit speed. Cells with link failures are not able to receive information via at most one of their both links to adjacent cells. Moreover, static and dynamic defects are distinguished. It is shown that fault tolerant real-time recognition capabilities of two-way arrays with static defects are characterizable by intact one-way arrays and that one-way arrays are fault tolerant per se. For arrays with dynamic defects it is proved that all failures can be compensated as long as the number of adjacent defective cells is bounded. In case of arrays with link failures it is shown that the sets of patterns that are reliably recognizable are strictly in between the sets of (intact) one-way and (intact) two-way arrays.

Handover and new call blocking performance with dynamic single-channel assignment in linear cellular arrays

We consider dynamic assignment of a single channel in a linear cellular array, and derive closedform expressions for the blocking probability of handover calls and new calls in terms of the array s...

Equivalent mobility traffic in circular and linear cellular arrays

Traffic behaviour in circular and linear cellular arrays is investigated. A model for fixed velocity mobiles is introduced. It is shown that the cellular network traffic is independent of the number of cells in the circular array case and that, compared with non-mobility in both linear and circular arrays, mobility factors such as cell size, call holding time and velocity of mobiles have considerable impact on probabilities of call blocking. As a result, the notion of ‘equivalent mobility traffic’ is introduced and its behaviour is investigated. A fixed point method for the analysis of probability of blocking is presented. Results are compared with simulations. © 1998 John Wiley & Sons, Ltd.

Call blocking probabilities for dynamic and fixed assignment of a single channel in a linear cellular array

We consider the problem of assigning a single channel in a linear cellular array, and compare the call blocking probabilities for dynamic and fixed channel assignment (DCA and FCA). Our principal concern is the derivation of closed-form expressions for these blocking probabilities as a function of the array size and traffic load, assuming a Markov traffic model. The limiting behavior of the blocking probabilities for DCA and FCA relative to increasing array size and extreme traffic loads is also discussed. Moreover, it is shown that there is a unique cross-over traffic load such that DCA has a lower blocking probability than FCA for traffic loads less than the cross-over load, and vice versa.

Shannon-theoretic approach to a Gaussian cellular multiple-access channel

We obtain Shannon-theoretic limits for a very simple cellular multiple-access system. In our model the received signal at a given cell site is the sum of the signals transmitted from within that cell plus a factor /spl alpha/ (0/spl les//spl alpha//spl les/1) times the sum of the signals transmitted from the adjacent cells plus ambient Gaussian noise. Although this simple model is scarcely realistic, it nevertheless has enough meat so that the results yield considerable insight into the workings of real systems. We consider both a one dimensional linear cellular array and the familiar two-dimensional hexagonal cellular pattern. The discrete-time channel is memoryless. We assume that N contiguous cells have active transmitters in the one-dimensional case, and that N/sup 2/ contiguous cells have active transmitters in the two-dimensional case. There are K transmitters per cell. Most of our results are obtained for the limiting case as N/spl rarr//spl infin/. The results include the following. (1) We define C/sub N/,C/spl circ//sub N/ as the largest achievable rate per transmitter in the usual Shannon-theoretic sense in the one- and two-dimensional cases, respectively (assuming that all signals are jointly decoded). We find expressions for limN/spl rarr//spl infin/C/sub N/ and limN/spl rarr//spl infin/C/spl circ//sub N/. (2) As the interference parameter /spl alpha/ increases from 0, C/sub N/ and C/spl circ//sub N/ increase or decrease according to whether the signal-to-noise ratio is less than or greater than unity. (3) Optimal performance is attainable using TDMA within the cell, but using TDMA for adjacent cells is distinctly suboptimal. (4) We suggest a scheme which does not require joint decoding of all the users, and is, in many cases, close to optimal.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Iterative algorithms for the planar convex hull problem on mesh-connected arrays

Algorithms are presented which solve the planar convex hull problem on a variety of mesh-connected arrays of processors without using recursion or divide-and-conquer techniques. The algorithms for one-way iterative arrays, one-way linear cellular arrays, and two-way linear cellular arrays all operate in time O( n). The algorithm for a two-way d-dimensional cellular array operates in time O(n 1 d ) . These algorithms are optimal for their arrays. The last algorithm can be used on an O( n) processor hypercube with a time complexity of O(log 2 n). We also show how these algorithms can be adapted to fully dynamic implementations with optimal throughput and turn-around. We believe that these algorithms may have performance advantages over existing parallel divide-and-conquer algorithms for planar convex hull.

Optimal simulation of tree arrays by linear arrays

We show that an n-node complete binary tree can be embedded into an n-node linear array such that the maximum edge length is n log n , and the distribution of the tree nodes is regular in the sense that if each node in the tree array is a finite-state machine and each edge is a communication channel, then the message exchanges (i.e., communication) among the tree nodes can be easily simulated by the linear array which has also finite-state machines for its nodes. The embedding is optimal with respect to the maximum edge length. The motivation for this is the proof of the following result: every cellular (or (log n)-depth iterative) tree array running in T( n) time can be simulated by a linear cellular (or iterative) array in nT(n) log n time.