Biomedical subjects

Y Shin

Publications and source records attributed to Y Shin.

At least 19 recordsLinked to original sources

PubMed2006

Low velocity quantum reflection of Bose-Einstein condensates.

We study how interactions affect the quantum reflection of Bose-Einstein condensates. A patterned silicon surface with a square array of pillars resulted in high reflection probabilities. For incident velocities greater than 2.5 mm/s, our observations agreed with single-particle theory. At velocities below 2.5 mm/s, the measured reflection probability saturated near 60% rather than increasing towards unity as predicted by the accepted theoretical model. We extend the theory of quantum reflection to account for the mean-field interactions of a condensate which suppresses quantum reflection at low velocity. The reflected condensates show collective excitations as recently predicted.

Journal Article↗

PubMed2006

Observation of phase separation in a strongly interacting imbalanced fermi gas.

We have observed phase separation between the superfluid and the normal component in a strongly interacting Fermi gas with imbalanced spin populations. The in situ distribution of the density difference between two trapped spin components is obtained using phase-contrast imaging and 3D image reconstruction. A shell structure is clearly identified where the superfluid region of equal densities is surrounded by a normal gas of unequal densities. The phase transition induces a dramatic change in the density profiles as excess fermions are expelled from the superfluid.

Journal Article↗

PubMed2006

Burden of disease attributable to obesity and overweight in Korea.

OBJECTIVE: To estimate the burden of disease attributable to overweight and obesity using disability-adjusted life-year (DALY) in Korea. RESEARCH METHODS: Firstly, overweight and obesity-related diseases and their relative risk (RR) were selected by the systematic review. Secondly, population-attributable fractions (PAFs) were computed by using the formula including RR and the prevalence of exposure (Pe) of overweight and obesity. Thirdly, DALYs of overweight and obesity-related diseases in Korea were estimated. Finally, the attributable burden (AB) of diseases due to overweight and obesity was calculated as the sum of the products from multiplying DALYs of overweight and obesity-related diseases by their PAFs. RESULTS: The disease burden attributable to overweight was 827.1 person years (PYs) overall, 732.6 for men, 922.9 for women per 100,000 persons. The disease burden attributable to obesity was 260.0 PYs overall, 144.2 for men, 377.3 for women. Diabetes attributable to overweight and obesity accounts for highest burden among other diseases in both genders. The disease burden attributable to overweight was 3.2 times higher than that attributable to obesity. CONCLUSION: Most proportion of disease burden attributable to high body mass index (BMI) occurred among those with only moderately raised levels such as overweight, not the extremes such as obesity. It suggests that population-based, public health intervention rather than high-risk group-focused strategies are more effective to reduce the burden of disease attributable to overweight and obesity in Korea.

Adult↗

PubMed2006

In-medium effects on phase space distributions of antikaons measured in proton-nucleus collisions.

Differential production cross sections of K+/- mesons have been measured in p + C and p + Au collisions at 1.6, 2.5, and 3.5 GeV proton beam energy. At beam energies close to the production threshold, the K- multiplicity is strongly enhanced with respect to proton-proton collisions. According to microscopic transport calculations, this enhancement is caused by two effects: the strangeness exchange reaction NY --> K- NN and an attractive in-medium K- N potential at saturation density.

Journal Article↗

PubMed2006

Clinical and biochemical correlates of insoluble alpha-synuclein in dementia with Lewy bodies.

Alpha-synuclein is a major constituent of Lewy bodies, the fibrillar aggregates that form within neurons in Parkinson's disease and dementia with Lewy bodies (DLB). Recent biochemical data show that alpha-synuclein accumulates in Parkinson's disease in a detergent insoluble form. We now examine the relationship between detergent insoluble alpha-synuclein and the presence of Lewy bodies, clinical measures of dementia and biochemical parameters in a series of individuals with DLB. We found that Triton X-100 insoluble alpha-synuclein enriched nearly twofold in the temporal cortex of patients with DLB compared to age-matched controls. By contrast the total amount of alpha-synuclein protein was unchanged. Surprisingly, the degree of Triton X-100 insoluble alpha-synuclein did not correlate with either the duration of illness or the number of Lewy bodies counted using stereological methods from an adjacent block of tissue. However, the Triton X-100 soluble fraction of alpha-synuclein did correlate strongly with the expression of several heat shock proteins (HSPs) in DLB but not control cases, suggesting a coordinated HSP response in DLB neocortex.

Aged↗

PubMed2005

The use of ultrasonic bone curettes in spinal surgery.

OBJECT: The author describes a clinical applications, procedure, and efficacy of ultrasonic bone curette (UBC) (bone-removal bar) in spinal surgery. METHODS: From July 2003 to March 2005, we operated on 98 consecutive spinal disorders by using UBC, Sonopet UST-2001; Chiari type-1 malformation (6 cases), cervical disorders (64 cases), thoracic disorders (5 cases), and lumbar disorders (23 cases). The instrument was devoid of any spinning parts, and the risk of grabbing cotton pledgets and damaging normal tissue was thereby avoided. Support from assistants for irrigation and suction was not required. FINDINGS: In this series, there were no iatrogenically induced injuries for example, direct or heat damage to surrounding soft tissues, including nerves, vessels, spinal cord, and dura matter. Considering potential complications of mechanical injuries by ultrasonic technique, intermittent usage and cotton protection during use under an operating microscope are recommended. We found that the ultrasonic device is easy to handle; however, it is time consuming for removing a large amount of bone and ossified lesions. Therefore, we recommend the combined use of this method with standard drilling. CONCLUSIONS: This system appears to be versatile, safe, and efficient in spinal surgery and could be improved by the development of a better handpiece.

Aged↗

PubMed2005

Optical weak link between two spatially separated Bose-Einstein condensates.

Two spatially separate Bose-Einstein condensates were prepared in an optical double-well potential. A bidirectional coupling between the two condensates was established by two pairs of Bragg beams which continuously outcoupled atoms in opposite directions. The atomic currents induced by the optical coupling depend on the relative phase of the two condensates and on an additional controllable coupling phase. This was observed through symmetric and antisymmetric correlations between the two outcoupled atom fluxes. A Josephson optical coupling of two condensates in a ring geometry is proposed. The continuous outcoupling method was used to monitor slow relative motions of two elongated condensates and characterize the trapping potential.

Journal Article↗

PubMed2005

Observation of different azimuthal emission patterns of K+ and of K- mesons in heavy-ion collisions at 1-2 A GeV.

Azimuthal distributions of pi+, K+, and K- mesons have been measured in Au+Au reactions at 1.5A GeV and Ni+Ni reactions at 1.93 A GeV. In semicentral collisions at midrapidity, pi+ and K+ mesons are emitted preferentially perpendicular to the reaction plane in both collision systems. In contrast for K- mesons in Ni+Ni reactions, an in-plane elliptic flow was observed for the first time at these incident energies.

Journal Article↗

PubMed2005

Light scattering to determine the relative phase of two Bose-Einstein condensates.

We demonstrated an experimental technique based on stimulated light scattering to continuously sample the relative phase of two spatially separated Bose-Einstein condensates of atoms. The phase measurement process created a relative phase between two condensates with no initial phase relation, read out the phase, and monitored the phase evolution. This technique was used to realize interferometry between two trapped Bose-Einstein condensates without need for splitting or recombining the atom cloud.

Journal Article↗

PubMed2005

Clinical features of postoperative cerebral venous infarction.

There is a potential risk of sacrificing the cortical vein during neurosurgical operations, particularly in the interhemispheric or subtemporal approach. An impaired cortical vein might cause cerebral venous circulatory disturbances (CVCDs) resulting in venous infarction. In this article, we have reviewed the management and results of eight cases with symptomatic postoperative venous infarction. We have encountered eight cases with symptomatic postoperative venous infarction (0.3%) during the past 5 years. The series is composed of 3 males and 5 females, with ages that ranged from 43 to 76 years (mean age of 58.1 years), and consisted of five brain tumors, one cavernoma, one dural AVF, and one trigeminal neuralgia. Initial symptoms occurred intra-operatively in two, on 0 day after the operation in one, 1 day in three, 3 days in one, and 4 days in one case. The symptoms were intra-operative brain edema in two cases, disorientation in one, cerebellar signs in one, hemiparesis in one, aphasia in two, and headache in one case. Two cases required surgical intervention. The results were a good outcome in 6 and a fair outcome in 2 cases. In conclusion, there are two types of postoperative venous infarction; severe onset (severe type) and gradual onset (mild type). The former needs immediate treatment from the intra-operative period onward, and the prevention of the ongoing venous thrombosis is essential in the latter.

Adult↗

PubMed2004

Quantum reflection from a solid surface at normal incidence.

We observed quantum reflection of ultracold atoms from the attractive potential of a solid surface. Extremely dilute Bose-Einstein condensates of 23Na, with peak density 10(11)-10(12) atoms/cm(3), confined in a weak gravitomagnetic trap were normally incident on a silicon surface. Reflection probabilities of up to 20% were observed for incident velocities of 1-8 mm/s. The velocity dependence agrees qualitatively with the prediction for quantum reflection from the attractive Casimir-Polder potential. Atoms confined in a harmonic trap divided in half by a solid surface exhibited extended lifetime due to quantum reflection from the surface, implying a reflection probability above 50%.

Journal Article↗

PubMed2004

Dynamical instability of a doubly quantized vortex in a Bose-Einstein condensate.

Doubly quantized vortices were topologically imprinted in /F=1> 23Na condensates, and their time evolution was observed using a tomographic imaging technique. The decay into two singly quantized vortices was characterized and attributed to dynamical instability. The time scale of the splitting process was found to be longer at higher atom density.

Journal Article↗

PubMed2004

Mutational analysis of OGG1, MYH, MTH1 in FAP, HNPCC and sporadic colorectal cancer patients: R154H OGG1 polymorphism is associated with sporadic colorectal cancer patients.

MYH, OGG1 and MTH1 are members of base excision repair (BER) families, and MYH germline mutations were recently identified in patients with multiple adenomas or familial adenomatous polyposis (FAP). A total of 20 APC-negative Korean FAP patients were analyzed for OGG1, MYH and MTH1 germline mutations. A total of 19 hereditary nonpolyposis colorectal cancer (HNPCC), 86 suspected HNPCC, and 246 sporadic colorectal cancer cases were investigated for OGG1 and MYH mutations. A total of 14 R154H OGG1 polymorphisms were identified in hereditary, sporadic colorectal cancers, and normal controls. For the case-control analysis of OGG1 R154H, a total of 625 hereditary or sporadic colorectal cancer patients and 527 normal controls were screened. R154H was a rare polymorphism associated with sporadic colorectal cancer patents (OR: 3.586, P= 0.053). R154H does not segregate with cancer phenotypes. Upon examining the possibility of recessive inheritance of R154H, we could not identify any complementary mutations in OGG1, MYH or MTH1. Samples with R154H were further screened for mutations of K-ras, beta-catenin, APC, p53, BRAF and the microsatellite instability (MSI) status. Eight somatic mutations were identified in these genes and G:C to T:A transversion mutations were not dominant in samples harboring R154H. This result raises the possibility that OGG1 R154H may function as a low/moderate-penetrance modifier for colorectal cancer development.

Adenomatous Polyposis Coli↗

PubMed2004

Distillation of bose-einstein condensates in a double-well potential.

Bose-Einstein condensates of sodium atoms, prepared in an optical dipole trap, were distilled into a second empty dipole trap adjacent to the first one. The distillation was driven by thermal atoms spilling over the potential barrier separating the two wells and then forming a new condensate. This process serves as a model system for metastability in condensates, provides a test for quantum kinetic theories of condensate formation, and also represents a novel technique for creating or replenishing condensates in new locations.

Journal Article↗

PubMed2004

Atom interferometry with Bose-Einstein condensates in a double-well potential.

A trapped-atom interferometer was demonstrated using gaseous Bose-Einstein condensates coherently split by deforming an optical single-well potential into a double-well potential. The relative phase between the two condensates was determined from the spatial phase of the matter wave interference pattern formed upon releasing the condensates from the separated potential wells. Coherent phase evolution was observed for condensates held separated by 13 microm for up to 5 ms and was controlled by applying ac Stark shift potentials to either of the two separated condensates.

Journal Article↗

PubMed2004

Diagnosis and management of galactosemia: an Egyptian experience.

OBJECTIVE: To screen normal and high risk Egyptian neonates for galactosemia. SUBJECTS AND METHODS: The study included 2238 neonates classified into two groups. Group I included screening of 1794 normal newborns. Group II included 374 high risk neonates (jaundice, hepatomegaly and failure to thrive). Group III 70 prematures. Total galactose was determined by enzymatic colourimetric method in dried blood spot (Quantase). The enzymes activities (uridyltransferase and epimerase) were measured using C14. RESULTS: One case of galactosemia was found in the first group and 26 cases in the second group. 19 patients suffered from uridyltransferase deficiency, the parents of 16 (88.8%) of this classic form were consanguineous and 5 (27.7%) parents had history of a previously affected child. Mean age of diagnosis was 3.8 month with a mean total gal value of 52.9 mg/dl. 10 (55.5%) of them have cataract. The other 8 affected neonates were epimerase deficiency patients. 5 (62.5%) of them born to consanguineous parents. Parents of the epimerase deficiency neonates have no previously affected children. Mean age of diagnosis was 7.2 month with a mean total gal of 17.5 mg/dl. All eight patients have cataract. CONCLUSION: Mass screening program is not available yet in Egypt. Screening of the high risk neonates is a priority. Diagnosis of different galactosemia forms is mandatory to structure the management strategy accordingly. (Fig. 4, Ref: 26.)

Egypt↗

PubMed2003

First evidence for different freeze-out conditions for kaons and antikaons observed in heavy-ion collisions.

Differential production cross sections of K- and K+ mesons have been measured in Ni+Ni and Au+Au collisions at a beam energy of 1.5 A GeV. The K(-)/K(+) ratio is found to be nearly constant as a function of the collision centrality and system size. The spectral slopes and the polar emission pattern differ for K- and K+ mesons. These observations indicate that K+ mesons decouple earlier from the fireball than K- mesons.

Journal Article↗

PubMed2003

Cooling Bose-Einstein condensates below 500 picokelvin.

Spin-polarized gaseous Bose-Einstein condensates were confined by a combination of gravitational and magnetic forces. The partially condensed atomic vapors were adiabatically decompressed by weakening the gravito-magnetic trap to a mean frequency of 1hertz, then evaporatively reduced in size to 2500 atoms. This lowered the peak condensate density to 5 x 10(10) atoms per cubic centimeter and cooled the entire cloud in all three dimensions to a kinetic temperature of 450 +/- 80 picokelvin. Such spin-polarized, dilute, and ultracold gases are important for spectroscopy, metrology, and atom optics.

Journal Article↗