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Biomedical subjects

J T Shen

Publications and source records attributed to J T Shen.

At least 19 recordsLinked to original sources
PubMed2006

Shift-invariant real-time edge-enhanced VanderLugt correlator using video-rate compatible photorefractive polymer.

We demonstrated a real-time shift-invariant VanderLugt correlator (VLC). The VLC was implemented with a 37 microm thick bis-triarylamine side-chain polymer matrix photorefractive (PR) polymer composite operating at 532 nm wavelength. Correlation selectivity was enhanced by real-time edge enhancement. The advantage of the VLC is that its architecture allows overcoming the PR material response speed. A correlator of this type enables a fast shift-invariant search of a large optical image database. A high degree of shift invariance in our correlator was possible because of the material thickness. The angular bandwidth of this material was measured experimentally in a degenerate four-wave mixing setup, and it was found to be in a very good agreement with the theory.

Journal Article↗
PubMed2005

Demonstration of a multiwave coherent holographic beam combiner in a polymeric substrate.

We demonstrate an efficient coherent holographic beam combiner (CHBC) that uses angle multiplexing of gratings in a thick polymeric substrate. Our experimental results compare well with the theoretical model based on the coupled-wave theory of multiwave mixing in a passive medium. A CHBC of this type may prove useful in producing a high-power laser by combining amplified beams produced by splitting a master oscillator. Furthermore, the ability to angle multiplex a large number of beams enables a CHBC to be used in multiple-beam interferometry applications as a high-precision surface sensor.

Journal Article↗
PubMed2005

Coherent photon transport from spontaneous emission in one-dimensional waveguides.

A two-level system coupled to a one-dimensional continuum is investigated. By using a real-space model Hamiltonian, we show that spontaneous emission can coherently interfere with the continuum modes and gives interesting transport properties. The technique is applied to various related problems with different configurations, and analytical solutions are given.

Journal Article↗
PubMed2005

Mechanism for designing metallic metamaterials with a high index of refraction.

We introduce a mechanism for creating artificial high refractive index metamaterials by exploiting the existence of subwavelength propagating modes in metallic systems. As an example, we investigate analytically and numerically metal films with a periodic arrangement of cut-through slits. Because of the presence of TEM modes in the slits, for TM polarization such a system can be rigorously mapped into a high refractive index dielectric slab when the features are smaller than the wavelength of light. The effective refractive index is entirely controlled by the geometry of the metal films, is positive, frequency independent, and can be made arbitrarily large.

Journal Article↗
PubMed2004

Demonstration of a simple technique for determining the M/# of a holographic substrate by use of a single exposure.

We propose and demonstrate a simple technique for determining the M/# parameter of a holographic recording material. In this method, divergent object and reference beams are used to produce a spatially varying index modulation. One can analyze the resultant diffraction pattern to find M/# by using only a single grating; existing techniques require many gratings.

Journal Article↗
PubMed2004

Ultrafast holographic Stokesmeter for polarization imaging in real time.

We propose an ultrafast holographic Stokesmeter using a volume holographic substrate with two sets of two orthogonal gratings to identify all four Stokes parameters of the input beam. We derive the Mueller matrix of the proposed architecture and determine the constraints necessary for reconstructing the complete Stokes vector. The speed of this device is determined primarily by the channel spectral bandwidth (typically 100 GHz), corresponding to a few picoseconds.

Journal Article↗
PubMed2003

Superparallel holographic correlator for ultrafast database searches.

We describe a superparallel holographic optical correlator that performs two-dimensional spatial and angular multiplexing simultaneously. The key step in this architecture is the use of a holographic multiplexer to split a query image into many copies before it applies them to the holographic database. A holographic demultiplexer, in conjunction with an aperture, is used to identify the location and the angle of the brightest correlation peak. This architecture uses only O(square root of N) detector elements to search through N unsorted images in a single query. We demonstrate the basic features of this architecture, using three spatial locations with eight angle-multiplexed images in each location.

Journal Article↗
PubMed2001

Cystitis glandularis mimics bladder cancer--three case reports and literature review.

Cystitis glandularis is an uncommon proliferative disorder of the mucus-producing glands within the mucosa and submucosa of urinary bladder epithelium. We report three cases with gross hematuria on first presentation. Both sonography and computer tomography revealing bladder tumor and transurethral resection was performed in all three cases. Cystitis glandularis was confirmed by pathology. Short-term follow-up of sonography and cystoscopy showed good results.

Adult↗
PubMed2001

Comparison of hand-assisted laparoscopic nephroureterectomy with open surgery for upper urinary tract tumor.

Herein we report on our initial experience in performing nephroureterectomy by hand-assisted laparoscopic surgery, and compare the results with those performed by traditional open methods. From December 2000 to September 2001, 10 patients with upper urinary tract tumors underwent hand-assisted laparoscopic nephroureterectomy. Except for one patient who required elective conversion to open surgery due to renal vein injury, this cohort of 9 patients was compared to a group of 35 patients who had received traditional open nephroureterectomy over the last 2 years. Demographic, intraoperative and postoperative data were compared retrospectively. These two groups were similar in age, body mass index, operation time and time to postoperative oral intake. However, the hand-assisted laparoscopy group was found to have significantly less blood loss, less need for parenteral narcotic and a shorter length of time needed for postoperative hospitalization than the open group. Thus, in this report we have demonstrated hand-assisted laparoscopic nephroureterectomy to be a safe and efficacious treatment of malignant urinary collecting tumors. We believe the benefits of this minimally invasive surgery make it a viable alternative technique for management of upper urinary tract tumor.

Adult↗
PubMed1999

Transcriptional regulation of mouse delta-opioid receptor gene.

Three major types of opioid receptors, mu (MOR), delta (DOR), and kappa (KOR), have been cloned and characterized. Each opioid receptor exhibits a distinct pharmacological profile as well as a distinct pattern of temporal and spatial expression in the brain, suggesting the critical role of transcription regulatory elements and their associated factors. Here, we report the identification of a minimum core promoter, in the 5'-flanking region of the mouse DOR gene, containing an E box and a GC box that are crucial for DOR promoter activity in NS20Y cells, a DOR-expressing mouse neuronal cell line. In vitro protein-DNA binding assays and in vivo transient transfection assays indicated that members of both the upstream stimulatory factor and Sp families of transcription factors bound to and trans-activated the DOR promoter via the E box and GC box, respectively. Furthermore, functional and physical interactions between these factors were critical for the basal as well as maximum promoter activity of the DOR gene. Thus, the distinct developmental emergence and brain regional distribution of the delta opioid receptor appear to be controlled, at least in part, by these two regulatory elements and their associated factors.

Animals↗
PubMed1992

Different sensory blockade of interscalene versus axillary approach of brachial plexus block.

We examined results of brachial plexus block in 31 young male patients who underwent upper extremity surgical procedures. Interscalene block was performed using a paresthesia technique in 13 patients and axillary block, using the perivascular technique, in 18 patients. In both groups, 30 ml 1.5% lidocaine with 1:200,000 epinephrine was injected. Sensory blockade was evaluated at 5 min and 15 min after injection, determined by pinprick. Results showed that the interscalene technique preferentially blocked the cephalad nerves while the axillary technique produced similar block of both cephalad and caudal nerves of the brachial plexus. Difference between groups was statistically significant, suggesting that the extent of nerve block depends on the technique of approach per se. The difference in patterns of nerve blocked by either technique could be due to the access of local anesthetic to the different components of plexus in the sheath.

Adult↗
PubMed1990

[The causes of death of early endometrial cancer].

This is an analysis of 136 patients with clinical stage I and II endometrial carcinoma treated with primarily surgery at the Columbia Presbyterian Hospital between 1978 and 1985. There was a minimum three years follow up. Of 136 patients, 28 (21%) died with recurrent cancer. Tumor upstaging, histology, grade, depth of myometrial invasion, peritoneal cytology were of important factors in prognosis. Therefore, a clinically sophisticated study during initial operation and a deliberate planning of adjuvant treatment should further improve the survival rate of early endometrial cancer.

Aged↗
PubMed1989

A rapid DNA probe test for detecting human papilloma virus types 6/11 and 16 in biopsy specimens.

A simple, rapid and sensitive non-radioactive in situ hybridization assay for human papillomavirus (HPV) has been developed and used to detect HPV 6/11 and HPV16 DNA in ano-genital biopsy specimens. A comparative study to determine the sensitivity and the specificity of this assay relative to Southern blot hybridization assays was performed using one hundred biopsy specimens. The sensitivity of the in situ hybridization assay was 88% for HPV type 6/11 and 89% for HPV type 16. The specificity of the test was 99% for both virus types. In addition to its high sensitivity and specificity, this in situ hybridization assay for HPV uses a non-radioactive detection system. The assay is faster and easier to perform than the Southern blot method. Also, in situ hybridization assays permit the simultaneous evaluation of the histology, as well as the DNA content of biopsy tissues because they do not result in the destruction of tissue or cell morphology. This prototype HPV DNA assay was developed using DNA probes for HPV 6/11 and HPV 16 DNA in anogenital biopsy specimens. However, the protocol developed in these studies can easily be extended to include the use of probes for detecting other HPV types in a variety of tissues.

Anal Canal↗
PubMed1982

Adolescent sexual behavior.

Human sexuality is a lifelong process with biologic, psychosocial, and moral consequences. During adolescence, coping with sexual feelings and controlling sexual drive become urgent tasks that are made more difficult by today's society. Recent studies document a dramatic increase in the frequency of sexual activity among teenagers as well as a decrease in the age at which sexual activity begins. The pregnancy rate has increased dramatically in this age-group because of the general lack of willpower and moral strength of young people; lack of adult role models; sexual exploitation of the young, particularly by mass media and industries; and aversion of teenagers to contraception. Births to teenagers have actually decreased slightly, however, because of the accessibility of abortion.

Abortion, Legal↗
PubMed1982

Adolescent sexual counseling.

The physician provides a much-needed service to teenagers by counseling them regarding sexuality. A series of conferences during adolescence and use of questionnaires can facilitate discussion and point up potential problems. When the patient is confronted with a problem such as a need for contraception or an unwanted pregnancy, the physician should present all the options available and leave the final choice up to the patient. The physician is not obligated to participate in a solution that is counter to his or her moral values.

Abortion, Induced↗