Photorefractive keratectomy for astigmatism greater than -2.00 diopters in eyes with low, high, or extreme myopia

PURPOSE: To assess the efficacy of excimer laser photorefractive astigmatic keratectomy (PARK) in correcting astigmatism of more than -2.00 diopters (D) in eyes with low, high, and extreme myopia. SETTING: Pusan National University Hospital, Pusan, Korea. METHODS: Eighty-five patients (110 eyes) whose spherical error ranged from -3.00 to -13.00 D and cylinder ranged from -2.00 to -5.50 D had PARK with a VISX Twenty-Twenty excimer laser; follow-up was 6 months. All cases of myopic astigmatism were treated using the elliptical method and multizone ablation technique. Eyes were divided into 3 groups: low myopia, less than 6.00 D (n = 47); high myopia, from 6.25 to 10.00 D (n = 43); extreme myopia, over 10.25 D (n = 20). Alpins vector analysis was used to calculate the astigmatic change. RESULTS: By vector analysis, the success rate of astigmatic correction was more predictable in the low and high myopia groups than in the extreme myopia group (P < .05). There was little improvement in astigmatism in the extreme myopia group. CONCLUSION: Using PARK to correct astigmatism greater than -2.00 D in eyes with myopia less than -10.00 D tended to result in undercorrection; astigmatic correction in eyes with myopia over 10.25 D was minimal.     

Quantum-well infrared phototransistor with pHEMT structure

A quantum-well infrared phototransistor with a pseudomorphic high-electron mobility transistor (pHEMT) structure is presented. The proposed phototransistor uses four periods of a GaAs/Al/sub 0.3/Ga/sub 0.7/As (50 /spl Aring//120 /spl Aring/) quantum-well absorption region, as well as an In/sub 0.15/Ga/sub 0.85/As quantum well conducting channel under the absorption layer. The phototransistor shows a large responsivity of 140 A/W around 6 /spl mu/m at 23 K (for a cutoff wavelength of 7.5 /spl mu/m). The relation between the photoconductive gain and the transconductance of the pHEMT structure is also investigated.     

Non-contact heartbeat and respiration detector using capacitive sensor with Colpitts oscillator

A capacitive sensor for detecting the heartbeat rate of a human without direct contact with the skin is investigated. Precordial movement changes the capacitance between patch electrodes and modulates the frequency of a Colpitts oscillator. Heartbeat and respiration information can be obtained by demodulating the oscillating signal. Heartbeat signal obtained by bandpass filtering the harmonics of heartbeat frequency is separated from the demodulated signal.     

An empirical study of the determinants of the intention to participate in user-created contents (UCC) services

Up to now UCC services have been dominating the majority of the internet traffic, yet the answers to what motivates people to participate in the UCC services still remain vague and unclear. It is the motivation to find these answers that lead to this study. We adopted technology acceptance model (TAM) to our model and examined the effects of external variables—social identity, telepresence, altruism, perceived playfulness and social trust. Data was collected from undergraduate students in Jeonju University, South Korea, who had experience in UCC. The findings showed that social trust and perceived playfulness play a pivotal role in explaining the individual’s behavioral intention to participate in UCC services. Also, perceived encouragement was found to have significant influence on social trust instead of its direct effect on the intention to participate in UCC services. Additionally, social identity and telepresence were the most important factors of perceived encouragement. This implication can help both researchers and Web practitioners to better understand user behavior in UCC context.     

Molecular group system as one energy unit

In view of the various qualifications required of materials nowadays, efforts to change the characteristics of inherent materials have continued. However, most material conversion techniques that have been used in the past, such as alloy design and doping effect, cannot overcome the limitation that properties are only added to the original characteristics of pristine materials. Therefore, herein, we introduced a new material design technique, a so-called “Molecular Group System”, which is completely different from existing methods. Since whole-set-systems are considered one-energetic-unit-system, either only the merits of the constituent elements can be emphasized or new materials completely different from the raw ones can be synthesized. In this study, block-stacking bottom-up approach was employed to form a one group system from SnO₂, SnO_x, Sn, and graphene powders, and a binder, using high-energy irradiation. Then, we discussed theoretical verifications such as SnO₂-reduction and Sn-channeling.     

Experimental and theoretical studies of intergranular strain in an alpha titanium alloy during plastic deformation

Two complementary methods were used to analyse the deformation mechanisms involved in the plasticity of commercially pure titanium during compressive loading: neutron diffraction and the self-consistent model. The strain response of 15 crystallographic planes was tracked during the measurement, in directions both parallel and transverse to the straining direction, providing new insight into the mechanical behaviour of the polycrystal. The neutron diffraction results show evidence of tensile twins in the titanium alloy studied. The twin volume fraction was determined from the change in crystallographic texture. The influence and the role of plastic anisotropy were also studied and explained in this work. Good agreement was found between the experimental and predicted results.     

Approaches for obtaining sperm in patients with male factor infertility

OBJECTIVE: To describe methods of sperm retrieval for intracytoplasmic sperm injection (ICSI) in patients with male factor infertility and to review the clinical results using sperm from the different sources. DESIGN: The literature on sperm-obtaining methods and ICSI was reviewed. Studies related to this topic were identified through MEDLINE. RESULTS(S): This review describes the evolution of sperm retrieval methods. Sperm can be obtained by microepididymal sperm aspiration (MESA), percutaneous sperm aspiration (PESA), and testicular sperm extraction (TESE), from patients with congenital absence of the vas deferens or acquired vas obstruction. When ICSI is performed with ejaculated, epididymal, or testicular sperm, good fertilization and pregnancy rates are achieved without significant differences among the various sperm sources. The original percutaneous sperm aspiration method has been modified slightly and yields successful results. CONCLUSION(S): Viable pregnancies can be achieved with ICSI by using not only ejaculated sperm, but also epididymal and testicular sperm. Microepididymal sperm aspiration, percutaneous sperm aspiration, modified percutaneous sperm aspiration, and testicular sperm extraction can be considered standard procedures to treat male factor infertility.