1,720,961 research outputs found
Low Latency Random Access for Sporadic MTC Devices in Internet of Things
No full textThis paper proposes a compressed sensing-based random access protocol (CS-RACH), which is suitable for servicing a large number of machine-type communication devices in Internet of Things (IoT) network. In CS-RACH, we utilize a larger number of unique preambles compared to conventional LTE-RACH, however, the compressed sensing technique makes it possible to simultaneously detect the users with high accuracy. Compared to the user detection in conventional LTE-RACH, the proposed user detection can get rid of preamble collisions and decrease the collision probability, thereby the overall access latency is significantly reduced. To prove the benefits of the proposed CS-RACH, we mathematically analyze and compare access latency performance of LTE-RACH and CS-RACH. In particular, based on the least absolute shrinkage and selection operator approach, we derive a normalized throughput, access success probability, and average access latency. Our simulation results also exhibit that the proposed CS-RACH considerably reduces the access latency under reasonable conditions in IoT environments.
An error detection aided GSC/MRC switching scheme in AF based cooperative communications
No full textPreparation of 99mTc-HYNIC-PEG-liposomes for imaging focal sites of infection
No full text임상병리학과/석사[영문]
[한글]
염증부위를 국소화 진단할 수 있는 ^(99m)Tc-HYNIC-PEG-liposome을 합성하고 이를 이용
하여 농양 형성 동물모델에서의 생체분포와 생체영상을 분석함으로써 염증진단 시약으로
서의 가능성 여부를 확인하고자 하였다. 6-Chloronicotinic acid를 출발물질로 하여 6-hy
drazinopyridine-3-carboxylic acid, 6-BOC-hydrazino pyridine-3-carboxylic acid, succ
inimidyl 6-BOC-hydrazinopyridine-3-carboxylic acid를 순차적으로 합성하였고, 합성수
율은 각각 88.5%, 93.7%, 93.2%였다. Succinimidyl 6-BOC-hydrazinopyridine-3-carboxyli
c acid의 최종합성수율은 77.3%였다. Triethylamine을 이용해 합성된 succinimidyl 6-BOC
-hydrazino pyridine-3-carboxylic acid와 DSPE(distearoyl phosphatidylethanolamine)를
접합하였다. HYNIC-DSPE를 제조한 후에 EPC:PEG-DSPE:HYNIC-DSPE:cholesterol을 1.85:0.
15:0.07:1의 몰 비로 혼합하여 HYNIC-PEG-liposome을 제조하였다. 제조된 HYNIC-PEG-lipo
some의 직경은 106 nm였고, PEG-liposome에 접합된 HYNIC의 농도는 1.08 mM이었다. HYNIC
-PEG-liposome의 개수는 1 ㎖에 5.2×10^(14)개가 존재하였고, PEG-liposome 한 개당 HYN
IC은 약 1250개가 접합되었다. 제조된 HYNIC-PEG-liposome에 SnCl₂·2H₂O와 tricine을
이용하여 ^(99m)Tc를 표지하였다. ^(99m)Tc-HYNIC-PEG-liposome과 혈청을 섞어서 실온과
37℃에서 24시간까지 안정성을 확인하였다. ^(99m)Tc-HYNIC-PEG-liposome에 DTPA, cystei
ne, glutathione을 각각 과량의 몰 비로 섞고 37℃에서 1시간 반응 후에 transchelation
을 통해 안정성을 확인하였다. 살아있는 S. aureus 1×10^(10) (CFU, colony forming uni
ts)를 Sprague Dawley 백서 좌측 대퇴부에 근육 내 주사하고, 대조군으로 죽은 S. aureus
를 동량 우측 대퇴부에 접종하여 농양이식백서를 제조하고, 이를 이용하여 ^(99m)Tc-HYNI
C-PEG-liposome의 생체분포와 생체영상을 얻었다. ^(99m)Tc의 표지 수율은 99%이상이었으
며, 혈청 내에서 24시간까지 93.5%이상의 안정성을 나타내었다. DTPA, cysteine, glutath
ione을 각각 1000배의 몰 비를 첨가한 경우 ^(99m)Tc-HYNIC-PEG-liposome의 방사화학적순
도가 각각 98%, 96%, 99%으로서 안정하였다. 농양대 혈액비, 농양대 근육비, 농양대 대조
군의 비는 각각 2시간 후에 0.53, 2.84, 1.23이었고, 6시간 후에 0.82, 3.79, 1.47이었고
, 24시간 후에서는 1.33, 5.57, 1.03이었다. ^(99m)Tc-HYNIC-PEG-liposome의 농양이식백
서에서 생체분포는 비장과 간에서 %ID/g이 6시간에서 가장 높았으며 24시간에서는 감소하
였다. 혈중 %ID/g은 2시간, 6시간, 24시간 후에 각각 0.124, 0.071, 0.041로 나타나 혈중
제거율이 빠름을 알 수 있었다. 영상실험에서는 6시간에서 S. aureus에 의한 농양부위에
^(99m)Tc-HYNIC-PEG-liposome의 집적이 가장 높은 것을 확인하였으며, 대조부위에서는 집
적량이 작았다. 따라서 ^(99m)Tc-HYNIC-PEG-liposome을 손쉽게 제조할 수 있었으며 세균
에 의한 염증부위에 ^(99m)Tc-HYNIC-PEG-liposome이 특이적으로 국소화되는 것을 관찰함
으로써 임상에서 염증진단시약으로서 이용가능성을 확인하였다.
--------------------
핵심되는 말 : ^(99m)Tc, HYNIC, liposome, 생체분포, 생체영상
Preparation of 99mTc-HYNIC-PEG-liposomes for imaging focal sites of infection
To evaluating the effectiveness of ^(99m)Tc labeled-liposomes as an agent to
diagnose abscess, ^(99m)Tc-HYNIC(hydrazino nicotinamide)-PEG(polyethylene
glycol)-liposomes were prepared and the biodistribution of the liposomes was
investigated in a rat model bearing abscess. In order to synthesize HYNIC- DSPE
(distearoyl phosphatidyl ethanolamine) which is a crucial component for ^(99m)Tc
chelation, first of all succinimidyl 6-BOC-hydrazinopyridine-3-carboxylic acid was
synthesized from 6-chloronicotinic acid by three sequential reactions with 77.3%
overall yield. The chemical structure of succinimidyl 6-BOC-
hydrazinopyridine-3-carboxylic acid was determined by 1H-NMR analysis. A DSPE
derivative of succinimidyl 6-BOC-hydrazinopyridine-3-carboxylic acid was
transformed into HYNIC-DSPE by HCl/dioxane. HYNIC-PEG-liposomes were prepared by
hydration of the dried lipid mixture of egg phosphatidyl choline
EPC:PEG-DSPE:HYNIC-DSPE:cholesterol (1.85:0.15:0.07:1, molar ratio). The HYNIC
concentration in the PEG-coated liposome dispersion was 1.08 mM. In condition of
considering the measured liposomal size of 106 nm, the phospholipid concentration
of 77.5 μ㏖/㎖ and the liposomal particle number of 5.2×10^(14) liposomes/ml, it
is corresponded to approximate 1,250 nicotinyl hydrazine group per liposome in
HYNIC-PEG-liposome. The HYNIC-PEG- liposomes were labeled with ^(99m)Tc in the
presence of SnCl₂·2H₂O (a reducing agent) and tricine (a coligand). The removal
of free ^(99m)Tc was not necessary because the labeling efficiency were over 99%.
To investigate the level of in vivo transchelation of ^(99m)Tc in the liposomes,
the ^(99m)Tc-HYNIC-PEG-liposomes were incubated with a molar excess of DTPA,
cysteine or glutathione solutions at 37℃ for 1 hour. The radiolabeled liposomes
maintained 98%, 96% and 99% of radioactivity after incubation with respective
compounds. The radiolabeled liposomes were also incubated in the presence of human
serum at 37℃ for 24 hours. The radiolabeled liposomes still possessed over 90% of
the radioactivity after incubation with serum. An abscess model was prepared in the
left calf muscle of rats by subcutaneous administration of 1×10^(10) colony
forming units of live S. aureus. The same dose of heat-killed S. aureus was
administered to right calf muscle for a control model. The
^(99m)Tc-HYNIC-PEG-liposomes were highly localized in the spleen and liver. Two,
six, and twenty four hours post injection, the abscess/blood ratios were 0.53, 0.82
and 1.33, and the abscess /muscle ratios were 2.84, 3.79, and 5.57, and the
abscess/control ratios were 1.23, 1.47, and 1.03, respectively. The uptake of
^(99m)Tc-HYNIC-PEG-liposomes by the abscess tissue was greater than the uptake by
the control tissue, according to analysis of images taken by a gamma camera after 6
hour post injection. This procedure of ^(99m)Tc-labeling to HYNIC-liposomes is
rapid, efficient and easy to perform. The ^(99m)Tc-HYNIC-PEG-liposomes exhibited
the enhanced stability in vitro, as well as in vivo. These results suggest that the
^(99m)Tc-HYNIC-PEG-liposomes can be applied in diagnosis of abscess as an imaging
agent.ope
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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