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Vertebrobasilar dolichoectasia: a case report
Khoshnevisan A,Ahmadi Abhari SS
Tehran University Medical Journal , 2011,
Abstract: "nBackground: Vertebrobasilar dolichoectasia is defined as a prominent elongation, dilatation and tortuosity of the vertebral and basilar arteries. Ectatic basilar arteries may cause different neurological symptoms by several mechanisms including compressive effects and embolic or ischemic events."n "nCase presentation: In this report we present a 58-year old female patient who was admitted in Dr. Shariati General Hospital in Tehran, Iran with complaints of dysarthria, vertigo, ataxia and nausea. Neuro-imaging procedures (brain CT scan, CT angiography, and an MRI study of the blood vessels or MRA) were performed. Dilation and elongation, as well as tortuosity of the vertebral and basilar arteries revealed the diagnosis of vertebrobasilar dolichoectasia. The patient was discharged from the hospital following the control of underlying diseases and neurological symptoms related to dolichoectasia without undergoing any invasive procedures."n "nConclusion: Paying attention to any minor or major neurological symptoms, as well as underlying medical conditions along with the conservative control of symptoms can be most helpful. Invasive interventions in a chronically ill patient can be very risky, therefore, medical management including control of associated or underlying diseases is recommended as the first line of treatment.
A Coupling, and the Darling-Erdos Conjectures
Davar Khoshnevisan,David A. Levin
Mathematics , 2005,
Abstract: We derive a new coupling of the running maximum of an Ornstein-Uhlenbeck process and the running maximum of an explicit i.i.d. sequence. We use this coupling to verify a conjecture of Darling and Erdos (1956).
Tectal Lipoma: A Case Report And Review Of Literature
A Khoshnevisan,M Mirkoohi,M Arjipour
Tehran University Medical Journal , 2012,
Abstract: Background:Intracranial lipomas are rare benign neoplasms that comprise 1% of all primary brain tumors. Generally, occur in midline structure and usually identified incidentally on CT scans or in autopsies. The incidence of intracranial lipomas is about 0.08 to 0.46% on autopsies. These benign lesions are slow-growing, usually asymptomatic and rarely require surgery. Case Presentation: We report a 20 years old male who complained of headache since two years ago. On CT examination, a quadrigeminal cistern lipoma without any pressure effect on neural structures demonstrated. His headache remitted with conservative measures. Here, we have a review on the literature and explain CT scan and MRI findings.Conclusion: According to the literature and present case,it seems that direct surgical excision of tumor is not justified in the majority of cases and symptoms of patients greatly respond to conservative measures and, at most,in cases of hydrocephalus,CSF shunting relieves their symptoms.
An Extreme-Value Analysis of the LIL for Brownian Motion
Davar Khoshnevisan,David A. Levin,Zhan Shi
Mathematics , 2004,
Abstract: We present an extreme-value analysis of the classical law of the iterated logarithm (LIL) for Brownian motion. Our result can be viewed as a new improvement to the LIL.
Neuronal spike sorting based on radial basis function neural networks
Taghavi Kani M,Homayoon Jafari A,Khoshnevisan A,Arabalibeyk H
Tehran University Medical Journal , 2011,
Abstract: "nBackground: Studying the behavior of a society of neurons, extracting the communication mechanisms of brain with other tissues, finding treatment for some nervous system diseases and designing neuroprosthetic devices, require an algorithm to sort neuralspikes automatically. However, sorting neural spikes is a challenging task because of the low signal to noise ratio (SNR) of the spikes. The main purpose of this study was to design an automatic algorithm for classifying neuronal spikes that are emitted from a specific region of the nervous system."n "nMethods: The spike sorting process usually consists of three stages: detection, feature extraction and sorting. We initially used signal statistics to detect neural spikes. Then, we chose a limited number of typical spikes as features and finally used them to train a radial basis function (RBF) neural network to sort the spikes. In most spike sorting devices, these signals are not linearly discriminative. In order to solve this problem, the aforesaid RBF neural network was used."n "nResults: After the learning process, our proposed algorithm classified any arbitrary spike. The obtained results showed that even though the proposed Radial Basis Spike Sorter (RBSS) reached to the same error as the previous methods, however, the computational costs were much lower compared to other algorithms. Moreover, the competitive points of the proposed algorithm were its good speed and low computational complexity."n "nConclusion: Regarding the results of this study, the proposed algorithm seems to serve the purpose of procedures that require real-time processing and spike sorting.
Comparative evaluation of the effect of silicone and teflon in prevention of epidural fibrosis after laminectomy in rat
Sheikh Rezaei A,Fakhr Tabatabaei SA,Khoshnevisan A,Marzban H
Tehran University Medical Journal , 2001,
Abstract: There are many studies about epidural fibrosis after surgical manipulation of the spine. We have studied formation of the post laminectomy epidural fibrosis after application of two materials (Silicone and Teflon) in this report. This expriment is on two groups of rats. Two separated laminectomies were done in each rat, one serving as control while in the other laminectomy spaces Silicone was used in group A and Teflon in group B. Laminectomy spaces were evaluated with gross dissection and histologic studies after 6 weeks. Silicone decreased intermuscular scar, deep scar, dural adhesion and collagen fiber density in epidural space. Teflon decreased dural adhesion and collagen fiber density but did not decrease intermuscular and deep scar formation in epidural space.
The effects of "Constraint-Induced Movement Therapy" on fine motor skills in children with hemiplegic cerebral palsy
Abootalebi Sh,Khoshnevisan A,Kohan AH,Pishyareh E
Tehran University Medical Journal , 2010,
Abstract: "n Normal 0 false false false EN-US X-NONE AR-SA MicrosoftInternetExplorer4 /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin:0cm; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-fareast-font-family:"Times New Roman"; mso-fareast-theme-font:minor-fareast; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-bidi-font-family:Arial; mso-bidi-theme-font:minor-bidi;} Background: Constraint-Induced movement therapy (CIMT) is a promising treatment for improving upper limb function in adults after stroke and traumatic brain injury. It involves constraint of the less affected limb and intensive practice with the more affected limb. The purpose of this study on children with hemiplegic cerebral palsy (CP) was to evaluate the effects of CIMT on upper extremity and to make a comparison with conventional treatment."n"nMethods: I a randomized clinical trial twelve children (seven females, five males; aged between 48 and 72 months with mean±standard deviation of 59.91±9.15mo) were randomly assigned in two groups. An intensive occupational therapy program including five hours per day for 21 consecutive days was performed for all of them, while less affected limbs were placed in sling for immobilization. Before and after intervention, upper extremity function, spasticity, and motor neuron excitation were evaluated by means of peabody developmental motor scales, modified Ashworth scale, and H reflex and H/M ratio, respectively."n"nResults: The children who received CIMT did not improved their ability to use their hemiplegic hand significantly more than the children in the control group (p>0.05). However, reports of caregivers and clinical observations showed increases in more affected limb frequency of use and quality of movement."n"nConclusion: Results suggest that the use of CIMT needs to more studies and should be considered experimental in children with hemiplegic CP
On dynamical bit sequences
Davar Khoshnevisan,David A. Levin,Pedro J. Mendez-Hernandez
Mathematics , 2007,
Abstract: Let X^{(k)}(t) = (X_1(t), ..., X_k(t)) denote a k-vector of i.i.d. random variables, each taking the values 1 or 0 with respective probabilities p and 1-p. As a process indexed by non-negative t, $X^{(k)}(t)$ is constructed--following Benjamini, Haggstrom, Peres, and Steif (2003)--so that it is strong Markov with invariant measure ((1-p)\delta_0+p\delta_1)^k. We derive sharp estimates for the probability that ``X_1(t)+...+X_k(t)=k-\ell for some t in F,'' where F \subset [0,1] is nonrandom and compact. We do this in two very different settings: (i) Where \ell is a constant; and (ii) Where \ell=k/2, k is even, and p=q=1/2. We prove that the probability is described by the Kolmogorov capacitance of F for case (i) and Howroyd's 1/2-dimensional box-dimension profiles for case (ii). We also present sample-path consequences, and a connection to capacities that answers a question of Benjamini et. al. (2003)
On Dynamical Gaussian Random Walks
D. Khoshnevisan,D. A. Levin,P. J. Mendez-Hernandez
Mathematics , 2003,
Abstract: Motivated by the recent work of Benjamini, Haggstrom, Peres, and Steif (2003) on dynamical random walks, we: Prove that, after a suitable normalization, the dynamical Gaussian walk converges weakly to the Ornstein-Uhlenbeck process in classical Wiener space; derive sharp tail-asymptotics for the probabilities of large deviations of the said dynamical walk; and characterize (by way of an integral test) the minimal envelop(es) for the growth-rate of the dynamical Gaussian walk. This development also implies the tail capacity-estimates of Mountford (1992) for large deviations in classical Wiener space. The results of this paper give a partial affirmative answer to the problem, raised in Benjamini et al (2003, Question 4), of whether there are precise connections between the OU process in classical Wiener space and dynamical random walks.
Capacities in Wiener Space, Quasi-Sure Lower Functions, and Kolmogorov's Epsilon-Entropy
Davar Khoshnevisan,David A. Levin,Pedro J. Mendez-Hernandez
Mathematics , 2004,
Abstract: We propose a set-indexed family of capacities $\{\cap_G \}_{G \subseteq \R_+}$ on the classical Wiener space $C(\R_+)$. This family interpolates between the Wiener measure ($\cap_{\{0\}}$) on $C(\R_+)$ and the standard capacity ($\cap_{\R_+}$) on Wiener space. We then apply our capacities to characterize all quasi-sure lower functions in $C(\R_+)$. In order to do this we derive the following capacity estimate which may be of independent interest: There exists a constant $a > 1$ such that for all $r > 0$, \[ \frac {1}{a} \K_G(r^6) e^{-\pi^2/(8r^2)} \le \cap_G \{f^* \le r\} \le a \K_G(r^6) e^{-\pi^2/(8r^2)}. \] Here, $\K_G$ denotes the Kolmogorov $\epsilon$-entropy of $G$, and $f^* := \sup_{[0,1]}|f|$.
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