Joint Carrier Fequency Synchronization and Channel Estimation for OFDM Systems Via the EM Algorithm

A joint carrier frequency synchronization and channel estimation scheme is proposed for orthogonal frequencydivision multiplexing (OFDM) system. In the proposed scheme, carrier frequency synchronization and channel estimation are performed iteratively via the expectation–maximization (EM) algorithm using an OFDM preamble symbol. Moreover, we analytically investigate the effect of frequency offset error on the mean square error (MSE) performance of channel estimator. Simulation results present that the proposed scheme achieves almost ideal performance for both channel and frequency offset estimation.This work was supported by the University IT Research Center Project and the Brain Korea 21 Project

Regulation of Polar Peptidoglycan Biosynthesis by Wag31 Phosphorylation in Mycobacteria

<p>Abstract</p> <p>Background</p> <p>Sensing and responding to environmental changes is a central aspect of cell division regulation. <it>Mycobacterium tuberculosis </it>contains eleven Ser/Thr kinases, two of which, PknA and PknB, are key signaling molecules that regulate cell division/morphology. One substrate of these kinases is Wag31, and we previously showed that partial depletion of Wag31 caused morphological changes indicative of cell wall defects, and that the phosphorylation state of Wag31 affected cell growth in mycobacteria. In the present study, we further characterized the role of the Wag31 phosphorylation in polar peptidoglycan biosynthesis.</p> <p>Results</p> <p>We demonstrate that the differential growth among cells expressing different <it>wag31 </it>alleles (wild-type, phosphoablative, or phosphomimetic) is caused by, at least in part, dissimilar nascent peptidoglycan biosynthesis. The phosphorylation state of Wag31 is found to be important for protein-protein interactions between the Wag31 molecules, and thus, for its polar localization. Consistent with these results, cells expressing a phosphomimetic <it>wag31 </it>allele have a higher enzymatic activity in the peptidoglycan biosynthetic pathway.</p> <p>Conclusions</p> <p>The Wag31_Mtbphosphorylation is a novel molecular mechanism by which Wag31_Mtbregulates peptidoglycan synthesis and thus, optimal growth in mycobacteria.</p

The Relative Contributions of the Medial Sural and Peroneal Communicating Nerves to the Sural Nerve

The medial sural cutaneous nerve (MSCN) and peroneal communicating nerve (PCN) conjoin in the calf area to form the sural nerve (SN). In previous anatomic studies, there was unresolved debate as to the main contributor to the sural nerve, and the relative contributions of MSCN and PCN had not been studied. The purpose of this study is to determine their relative neurophysiologic contributions to the SN by nerve conduction study (NCS). A total of 47 healthy subjects (25 males and 22 females, mean age 29.6 ± 10.4 yrs, range 20-59 yrs) participated in the study. This study employed the orthodromic nerve conduction technique: stimulation at the ankle and recording at the mid calf (SN); specifically, we preformed stimulation at the mid calf (MSCN, PCN) and recording at 14 cm proximal to the middle of the popliteal fossa (MSCN) and fibular head (PCN). The onset and peak latencies (ms) were SN 2.3 ± 0.2 and 3.0 ± 0.2; MSCN 2.1 ± 0.2 and 2.8 ± 0.2; and PCN 2.1 ± 0.2 and 2.8 ± 0.2. The peak-to-peak amplitudes (µV) and areas (nVsec) of the SN, MSCN, and PCN were 9.7 ± 3.9, 7.0 ± 4.7, and 5.0 ± 3.2; and 7.2 ± 2.9, 5.7 ± 3.4, and 4.0 ± 2.4, respectively. The side-to-side difference was not statistically significant. The main contributor to the SN was found to be the MSCN. The relative contribution ratio of the MSCN to the PCN was 1.37:1 by amplitude and 1.42:1 by area. However, in 32.9% of the subjects, the contribution of the PCN was greater than that of the MSCN

Prevalence and risk factors of the metabolic syndrome in young adults with childhood-onset hypopituitary growth hormone deficiency

PurposeThis study evaluated the prevalence of the metabolic syndrome (MetS) and risk factors for metabolic derangement in young adults with childhood-onset hypopituitary growth hormone deficiency (ACOHGHD).MethodsThirty patients with ACOHGHD who were treated with hormone-replacement therapy, aged 18 to 29 years, who visited the Seoul National University Children's Hospital between September 2009 and February 2010 were enrolled. Height, weight, waist circumference, hip circumference, and blood pressure were measured, and the clinical and hormonal features were reviewed retrospectively. We evaluated measures of metabolic derangement in the enrolled patients and in the data of healthy adults aged 20 to 29 years taken from the 2005 Korean National Health and Nutrition Examination Survey (KNHANES) as part of the National Cholesterol Education Program-the Adult Treatment Panel III.ResultsCompared with the KNHANES participants, patients with ACOHGHD had significantly large waist circumference (men and women), high systolic blood pressure (BP) (women) and diastolic BP (men), and high serum triglyceride levels (women). The duration of illness correlated significantly with central obesity (r2=0.546, P=0.003). The prevalence of MetS was 10% in patients with ACOHGHD and 2.3% in KNHANES participants. The prevalence of central obesity and MetS was higher in patients with ACOHGHD than in KNHANES participants (P<0.001 and P=0.042, respectively).ConclusionAbdominal obesity correlated with the duration of illness in patients with ACOHGHD. Waist circumference should be measured in the clinic to prevent MetS, particularly in patients with a long history of ACOHGHD, regardless of age or sex

The Prevalence of Chronic Diseases among Migrants in Korea According to Their Length of Stay and Residential Status

Background: Migrant health is becoming public health issues, as the migrant populations are increasing and their length of stayis prolonged. This study aims to analyze the differences in prevalence of chronic diseases among migrants according to length ofstay and residential status.Methods: An initial population pool were 3,024 who were assessed with health screening programs by Migrant Health Association.2,459 migrants were selected for final analysis. Via Stata 10 we conducted univariate logistic regression analysis to examine theeffects of their length of stay and residential status on the prevalence of hypertension, diabetes, dyslipidemia, and obesity. In thefinal analysis, the result of each sex was adjusted for age, nationality, length of stay, and residential status via multiple logisticregression analysis.Results: Longer length of stay tends to increase the prevalence of hypertension in male; 4-6 year stay-duration groupdemonstrated statistically significant excess compared to 1 year or less stay-duration group (adjusted odds ratio [OR], 1.39;confidence interval [CI], 1.01 to 1.92). After adjustment, male migrants stayed more than 7 year showed considerably higherdyslipidemia than male migrants stayed less than 1 year (adjusted OR, 1.95; CI, 1.05 to 3.64). Compared to the group with 1 yearor less stay-duration, the prevalence of obesity in male was significantly higher among 4-6 year (adjusted OR, 1.65; CI, 1.17 to 2.32)and 7 year or more stay-duration group (adjusted OR, 1.65; CI, 1.11 to 2.45).Conclusion: Longer length of stay correlated to higher prevalence of hypertension, dyslipidemia, and obesity among somepopulation of migrants. So more researches and new developing policies are needed for this problem.OAIID:oai:osos.snu.ac.kr:snu2012-01/102/0000052039/7SEQ:7PERF_CD:SNU2012-01EVAL_ITEM_CD:102USER_ID:0000052039ADJUST_YN:YEMP_ID:A077862DEPT_CD:801CITE_RATE:0FILENAME:52 The Prevalence of Chronic Diseases among Migrants in Korea According.pdfDEPT_NM:의학과EMAIL:[email protected]_YN:NCONFIRM:

Salvage Treatment for Persistent Methicillin-Resistant Staphylococcus aureus Bacteremia: Efficacy of Linezolid With or Without Carbapenem

Background. Persistent methicillin-resistant Staphylococcus aureus (MRSA) bacteremia is associated with high mortality rates, but no treatment strategy has yet been established. We performed this study to evaluate the efficacy of linezolid with or without carbapenem in salvage treatment for persistent MRSA bacteremia. Methods. All adult patients with persistent MRSA bacteremia for >= 7 days from January 2006 through March 2008 who were treated at Seoul National University Hospital were studied. The results of linezolid salvage therapy with or without carbapenem were compared with those of salvage therapy with vancomycin plus aminoglycosides or rifampicin. Results. Thirty-five patients with persistent MRSA bacteremia were studied. The early microbiological response (ie, negative results for follow-up blood culture within 72 hours) was significantly higher in the linezolid-based salvage therapy group than the comparison group (75% vs 17%; P = .006). Adding aminoglycosides or rifampicin to vancomycin was not successful in treating any of the patients, whereas linezolid-based therapy gave an 88% salvage success rate (P < .001). The S. aureus-related mortality rate was lower for patients treated with a linezolid salvage regimen than for patients continually treated with a vancomycin-based regimen (13% vs 53%; P = .030). Conclusions. Linezolid-based salvage therapy effectively eradicated S. aureus from the blood for patients with persistent MRSA bacteremia. The salvage success rate was higher for linezolid therapy than for vancomycin-based combination therapy.Jenkins TC, 2008, CLIN INFECT DIS, V46, P1000, DOI 10.1086/529190Falagas ME, 2008, LANCET INFECT DIS, V8, P53, DOI 10.1016/S1473-3099(07)70312-2Hawkins C, 2007, ARCH INTERN MED, V167, P1861Kollef MH, 2007, CLIN INFECT DIS, V45, pS191, DOI 10.1086/519470Micek ST, 2007, CLIN INFECT DIS, V45, pS184, DOI 10.1086/519471*CLIN LAB STAND I, 2007, M100S17 CLIN LAB STAHidayat LK, 2006, ARCH INTERN MED, V166, P2138Howden BP, 2006, ANTIMICROB AGENTS CH, V50, P3039, DOI 10.1128/AAC.00422-06Hageman JC, 2006, CLIN INFECT DIS, V43, pE42Jacqueline C, 2006, ANTIMICROB AGENTS CH, V50, P2547, DOI 10.1128/AAC.01501-05Sakoulas G, 2006, CLIN INFECT DIS, V42, pS40Jones RN, 2006, CLIN INFECT DIS, V42, pS13Khatib R, 2006, SCAND J INFECT DIS, V38, P7, DOI 10.1080/00365540500372846Wu VC, 2006, CLIN INFECT DIS, V42, P66Jacqueline C, 2005, ANTIMICROB AGENTS CH, V49, P45, DOI 10.1128/AAC.49.1.45-51.2005*CDCP, 2005, CA MRSA CLIN FAQS CDFowler VG, 2004, J INFECT DIS, V190, P1140Wisplinghoff H, 2004, CLIN INFECT DIS, V39, P309, DOI 10.1086/421946Khosrovaneh A, 2004, CLIN INFECT DIS, V38, P1328Howden BP, 2004, CLIN INFECT DIS, V38, P521KIM SH, 2004, 42 ANN M INF DIS SOC, P142Fowler VG, 2003, ARCH INTERN MED, V163, P2066Kim SH, 2003, CLIN INFECT DIS, V37, P794Moise PA, 2002, J ANTIMICROB CHEMOTH, V50, P1017, DOI 10.1093/jac/dkf215Li JS, 2000, CLIN INFECT DIS, V30, P633You I, 2000, DIAGN MICR INFEC DIS, V36, P37Lowy FD, 1998, NEW ENGL J MED, V339, P520Hiramatsu K, 1997, LANCET, V350, P1670LIBMAN H, 1984, ARCH INTERN MED, V144, P5411

Maximum likelihood sequence estimation via the expectation maximization algorithm in the presence of random phase and amplitude fading

Vita.The expectation-maximization (EM) algorithm was first introduced in the statistics literature as an iterative procedure that under some conditions produces maximum likelihood (ML) parameter estimates. Here we investigate the use of the EM algorithm to the problem of estimating transmitted sequences corrupted with random phase and amplitude fading as well as additive white Gaussian noise. The EM-based algorithm is derived and is shown to have linearly growing complexity as a function of sequence length. The algorithm is applied to the random phase and fading channels and its performance is seen to approach that of the optimal ML sequence estimator, which however is too complicated to implement in practice

Optimum decoding of TCM in the presence of phase errors

Due to the character of the original source materials and the nature of batch digitization, quality control issues may be present in this document. Please report any quality issues you encounter to [email protected], referencing the URI of the item.Includes bibliographical references.Not availabl