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 Ardavan Rahimian Computer Science , 2014, Abstract: This research project undertakes a comprehensive analysis of RF beamforming techniques for design, simulation, fabrication, and measurement of Butler Matrix and Rotman Lens beamforming networks. It is aimed to develop novel and well-established designs for steerable antenna systems that can be used in vehicular telematics and automotive communication systems based on microwave and millimeter-wave techniques.
 Computer Science , 2014, Abstract: Cryo-electron microscopy nowadays often requires the analysis of hundreds of thousands of 2D images as large as a few hundred pixels in each direction. Here we introduce an algorithm that efficiently and accurately performs principal component analysis (PCA) for a large set of two-dimensional images, and, for each image, the set of its uniform rotations in the plane and their reflections. For a dataset consisting of $n$ images of size $L \times L$ pixels, the computational complexity of our algorithm is $O(nL^3 + L^4)$, while existing algorithms take $O(nL^4)$. The new algorithm computes the expansion coefficients of the images in a Fourier-Bessel basis efficiently using the non-uniform fast Fourier transform. We compare the accuracy and efficiency of the new algorithm with traditional PCA and existing algorithms for steerable PCA.
 Physics , 1999, DOI: 10.1086/308525 Abstract: Natural (such as lunar) occultations have long been used to study sources on small angular scales, while coronographs have been used to study high contrast sources. We propose launching the Big Occulting Steerable Satellite (BOSS), a large steerable occulting satellite to combine both of these techniques. BOSS will have several advantages over standard occulting bodies. BOSS would block all but about 4e-5 of the light at 1 micron in the region of interest around the star for planet detections. Because the occultation occurs outside the telescope, scattering inside the telescope does not degrade this performance. BOSS could be combined with a space telescope at the Earth-Sun L2 point to yield very long integration times, in excess of 3000 seconds. If placed in Earth orbit, integration times of 160--1600 seconds can be achieved from most major telescope sites for objects in over 90% of the sky. Applications for BOSS include direct imaging of planets around nearby stars. Planets separated by as little as 0.1--0.25 arcseconds from the star they orbit could be seen down to a relative intensity as little as 1e-9 around a magnitude 8 (or brighter) star. Other applications include ultra-high resolution imaging of compound sources, such as microlensed stars and quasars, down to a resolution as little as 0.1 milliarcseconds.
 PLOS ONE , 2012, DOI: 10.1371/journal.pone.0038342 Abstract: The SLIT2-ROBO1/2 pathways control diverse biological processes, including growth regulation. To understand the role of SLIT2 and ROBO1/2 in cervical carcinogenesis, firstly their RNA expression profiles were screened in 21 primary uterine cervical carcinoma (CACX) samples and two CACX cell lines. Highly reduced expressions of these genes were evident. Concomitant alterations [deletion/methylation] of the genes were then analyzed in 23 cervical intraepithelial neoplasia (CIN) and 110 CACX samples. In CIN, SLIT2 was deleted in 22% samples compared to 9% for ROBO1 and none for ROBO2, whereas comparable methylation was observed for both SLIT2 (30%) and ROBO1 (22%) followed by ROBO2 (9%). In CACX, alteration of the genes were in the following order: Deletion: ROBO1 (48%) > SLIT2 (35%) > ROBO2 (33%), Methylation: SLIT2 (34%) > ROBO1 (29%) > ROBO2 (26%). Overall alterations of SLIT2 and/or ROBO1 (44%) and SLIT2 and/or ROBO2 (39%) were high in CIN followed by significant increase in stage I/II tumors, suggesting deregulation of these interactions in premalignant lesions and early invasive tumors. Immunohistochemical analysis of SLIT2 and ROBO1/2 in CACX also showed reduced expression concordant with molecular alterations. Alteration of all these genes predicted poor patient outcome. Multiparous (≥5) women with altered SLIT2 and ROBO1 along with advanced tumor stage (III/IV) and early sexual debut (<19 years) had worst prognosis. Our data suggests the importance of abrogation of SLIT2-ROBO1 and SLIT2-ROBO2 interactions in the initiation and progression of CACX and also for early diagnosis and prognosis of the disease.
 Mathematics , 2013, DOI: 10.1137/120864143 Abstract: The Riesz transform is a natural multi-dimensional extension of the Hilbert transform, and it has been the object of study for many years due to its nice mathematical properties. More recently, the Riesz transform and its variants have been used to construct complex wavelets and steerable wavelet frames in higher dimensions. The flip side of this approach, however, is that the Riesz transform of a wavelet often has slow decay. One can nevertheless overcome this problem by requiring the original wavelet to have sufficient smoothness, decay, and vanishing moments. In this paper, we derive necessary conditions in terms of these three properties that guarantee the decay of the Riesz transform and its variants, and as an application, we show how the decay of the popular Simoncelli wavelets can be improved by appropriately modifying their Fourier transforms. By applying the Riesz transform to these new wavelets, we obtain steerable frames with rapid decay.
 European Journal of Medical Research , 2012, DOI: 10.1186/2047-783x-17-24 Abstract: Intracranial cavernous malformations (CMs) are not uncommon in the clinic and account for 10 to 20% of intracranial vascular diseases [1]. CMs are usually found in the brain parenchyma, and CMs of the optic chiasm are extremely rare, accounting for <1% of intracranial CMs [2]. The clinical symptoms of chiasmal CMs depend on the lesion size and amount of bleeding. If the CM is large or the volume of bleeding is high, then the chiasmal CM usually elicits stroke symptoms (that is, headache, vision loss and visual field defects) [3,4]. CMs involving the optic chiasm typically cause bilateral temporal visual field defects [5,6]. Here, we describe a case with a CM located on the right side of the optic chiasm, in which the patient presented with bilateral left homonymous hemianopsia in the visual field examination. After definitive diagnosis, the CM was removed surgically with a satisfactory outcome. We further review pertinent literature on the clinical and radiological features and surgical treatment of CMs.A 28-year-old male complained of blurred vision in his right eye, which started 2？months before presentation and had worsened about 10？days before. He was otherwise healthy and had no negative past medical history or history of ocular trauma or surgery. Two months before presentation, the patient visited the Department of Ophthalmology, First Hospital of Jilin University, due to a sudden onset of blurred vision. Eye examination showed no obvious abnormalities, and no exact diagnosis was made. The patient did not return to the clinic until the sudden worsening of blurred vision with forehead pain 10 days before presentation. His best-corrected visual acuity was 0.5 in the right eye and 0.4 in the left eye. Anterior segment slit-lamp examination showed no obvious abnormalities. Fundus examination revealed binocular mild primary optic atrophy. Visual field examination showed left homonymous hemianopsia. No other neurological abnormalities were found. No abnormalities we
 International braz j urol , 2007, DOI: 10.1590/S1677-55382007000300013 Abstract: introduction: whereas a retrograde attempt to insert an indwelling stent is performed in lithotomy position, usually renal access is gained in a prone position. to overcome the time loss of patient repositioning, a renal puncture can be performed in a modified lithotomy position with torqued truncus and slightly elevated flank. there is a two-fold advantage of this position: transurethral and transrenal access can be obtained using a combined approach. in the present study, this simple technique is used to position a floppy guide wire through a modified needle directly through the renal pelvis into the ureter. materials and methods: the kidney is punctured in the modified lithotomy position under sonographic control using an initial three-part puncture needle. a floppy tip guide-wire is inserted into the collecting system via the needle after retrieving the stylet. the retracted needle is bent at the tip while the guide-wire is secured in the needle and the collecting system. the use of the floppy tip guide-wire helps to insert the curved needle back into the kidney pelvis, which becomes the precise guidance for the now steerable wire. the desired steerable stent is positioned under radiographic control in a retrograde fashion over the endoscopically harbored tip of the guide-wire. two patient cohorts (newly described method and conventional method) were compared. results: the presented steering procedure saves 16.5 mean minutes compared to the conventional antegrade stenting and 79.5 euros compared to the control group. conclusion: the described combined antegrade-retrograde stent placement through a bent three-part puncture needle results in both clinical superiority (or time, success rate) and financial benefits.
 - , 2015, DOI: 10.3969/j.issn.1671-9638.2015.11.002 Abstract: 目的探讨慢性重型乙型肝炎患者血清中Slit2蛋白水平，以及其与患者肝脏损伤程度、预后的关系。 方法将某院感染病科2014年2—7月住院及门诊收治的病毒性肝炎慢性乙型（慢性肝炎组）患者、病毒性肝炎慢性重型乙型（慢性重型肝炎组）患者纳入研究,健康志愿者为正常对照组，慢性重型肝炎组患者根据病情恢复情况再细分为恢复组和未恢复组，比较血清中Slit2蛋白、凝血酶原活动度（PTA）、总胆红素（TBIL）、谷丙转氨酶（ALT）水平,并进行相关性分析。结果共纳入慢性乙型肝炎患者157例（其中慢性肝炎组93例、慢性重型肝炎组64例）和健康志愿者10例（健康对照组），3组之间Slit2蛋白水平比较，差异有统计学意义（F=5.596，P=0.004），慢性肝炎组和慢性重型肝炎组患者血清中Slit2蛋白分别为（4.90±1.07）ng/mL、(3.09±1.00) ng/mL，均高于健康对照组［(2.10±0.60)ng/mL］(均P＜0.05)；慢性重型肝炎组患者血清Slit2蛋白水平低于慢性肝炎组(P＜0.05)。慢性重型肝炎未恢复组患者血清Slit2蛋白水平为(1.88±0.67) ng/mL，低于慢性重型肝炎恢复组［(2.96±1.32)ng/mL］，差异有统计学意义(t=2.319，P=0.032)。慢性乙型肝炎患者血清Slit2蛋白水平与PTA呈正相关(r=0.33，P＜0.05)；与TBIL水平、ALT水平呈负相关(r值分别为-0.46、-0.32，均P＜0.05)。结论血清Slit2蛋白水平是反映慢性重型肝炎患者预后的重要指标，低水平Slit2预示着预后不佳
 PLOS ONE , 2012, DOI: 10.1371/journal.pone.0051895 Abstract: Slit molecules comprise one of the four canonical families of axon guidance cues that steer the growth cone in the developing nervous system. Apart from their role in axon pathfinding, emerging lines of evidence suggest that a wide range of cellular processes are regulated by Slit, ranging from branch formation and fasciculation during neurite outgrowth to tumor progression and to angiogenesis. However, the molecular and cellular mechanisms downstream of Slit remain largely unknown, in part, because of a lack of a readily manipulatable system that produces easily identifiable traits in response to Slit. The present study demonstrates the feasibility of using the cell line CAD as an assay system to dissect the signaling pathways triggered by Slit. Here, we show that CAD cells express receptors for Slit (Robo1 and Robo2) and that CAD cells respond to nanomolar concentrations of Slit2 by markedly decelerating the rate of process extension. Using this system, we reveal that Slit2 inactivates GSK3β and that inhibition of GSK3β is required for Slit2 to inhibit process outgrowth. Furthermore, we show that Slit2 induces GSK3β phosphorylation and inhibits neurite outgrowth in adult dorsal root ganglion neurons, validating Slit2 signaling in primary neurons. Given that CAD cells can be conveniently manipulated using standard molecular biological methods and that the process extension phenotype regulated by Slit2 can be readily traced and quantified, the use of a cell line CAD will facilitate the identification of downstream effectors and elucidation of signaling cascade triggered by Slit.
 BIO Web of Conferences , 2011, DOI: 10.1051/bioconf/20110100010 Abstract: This paper presents an adaptive approach for 2D path planning of steerable needles. It combines dutycycled rotation of the needle with the classic RapidlyExploring Random Tree (RRT) algorithm and it is used intraoperatively to compensate for system uncertainties and perturbations. Simulation results demonstrate the performance of the proposed motion planner on a workspace based in ultrasound images.
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