• Maxillofacial Plastic and Reconstructive Surgery
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• v.27 no.5
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• pp.403-414
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• 2005

The purpose of this study was to identify the effectiveness of the modified distraction osteogenesis (DO) method with the concept of overdistraction and compression stimulation which have been previously suggested by the authors in 2002 and to explore the optimal distraction-compression ratio and appropriate latency period for the compression force application during consolidation. The experimental specimens were assessed with radiography, histologic findings, and dual energy x-ray absorptiometry (DEXA) after the conventional DO method and the modified DO technique had been applied on rat mandibles. Total 60 rats were used for the study. In experimental group of 54 adult rats, mandibular osteotomies between the first and second molar areas were performed and customized external distractors were applied. The surgeries on 6 rats of control group also were done with same osteotomy technique and DO device application. Final amount of distraction was set-up as 2 mm on both groups. But, in a experimental group of 54 rats, distraction osteogenesis with a compression force were performed with the different distraction-compression ratio and variant latency periods for compression. The three ratio-subgroups were made as distraction 4 mm group with compression 2 mm, distraction 3 mm group with compression 1 mm, and distraction 2.5 mm group with compression 0.5 mm. In addition, The three subgroups with 3, 7, 11 days latency period prior compression were allocated on each ratio-subgroups. Total 9 subgroups consisted of 6 rats on each subgroup. In control group of 6 rats, conventional distraction technique were routinely performed. The rats of control groups were sacrificed on postoperative 3, 6 weeks after 2 mm distraction. The rats in the experimental groups also were sacrificed on the same euthanasia days of control groups to compare the wound healing. Final available specimens were 55 rats except 5 due to osteomyelitis, device dislodgement. Distraction-compression combined group on 6 weeks generally had showed increased bone mineral density than the same period group of conventional distraction technique on the DEXA study. More matured lamellar bone state and extended trabecular pattern in the combined group than those of control group were also observed in the histologic findings on 6 weeks. In the distraction-compression combined groups, the bone density of 2.5 mm distraction subgroups with 0.5 mm compression showed the highest value on the DEXA study among various force ratio groups. In the distraction-compression combined groups, the bone density of 3 day latency period subgroups showed the highest value on the DEXA study among various latency period groups for the compression application. From this study, we could deduce that 1/5 force ratio for the compression versus distraction, 3 day latency period prior compression application would be the most effective condition if modified distraction osteogenesis technique might be applicable. The modified DO method with a compression force may improve the quality of bone regenerate and shorten total treatment period in comparison with conventional DO technique clinically.

• Journal of Periodontal and Implant Science
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• v.27 no.4
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• pp.867-882
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• 1997

Safflower(Carthamus tinctorius $Linn\acute{e}$ has been traditionally used for the treatment of blood stasis, and Dipsasi Radix has been used as a drug for fracture in Chinese medicine. The purpose of present study was to examine the biologic effects of safflower extract and Disasi radix extracts on the periodontal. ligament cells and osteoblastic cells and on the wound healing of rat calvarial defect. The ethanolic extract of safflower blossom, safflower seed and Dipsasi Radix(125, 250, and 500 ${\mu}g/ml$) were prepared as test group, and PDGF-BB(lOng/ml) and unsafonifiable fraction of Zea Mays L.(125, 250, and 500 ${\mu}g/ml$) were employed as positive control. The effects of each agents on the growth and survival, ALPase activity, expression of PDGF-BB receptor, chemotactic response of PDL cell and ATCC human osteosarcoma MG63 cells in vitro were examined. The tissue regenerative effect of each extracts was evaluated by histomorphometric measuring of newly formed bone on the 8mm defect in rat calvaria after oral administration of 3 different dosages groups : 0.02, 0.1 and 0.35g/kg, per day. It was also employed the same dosages of unsaponifiable fraction of Zea Mays L. as positive controls. Safflower blossom extract, safflower seed extract, and Dipsasi Radix extract stimulate the cellular activity of MG63 cells in concentration range of $125-500{\mu}g/ml$, and safflower bolssom extract and safflower seed extract stimulate also the cellular activity of periodontal ligament cells in concentration range of $250-500{\mu}g/ml$. In activity of ALPase, $250-500{\mu}g/ml$ of safflower blossom extracts showed significant stimulating effects on MG63 cells, and the same concentration range of safflower seed extracts showed significant effect on periodontal ligament cells. In the recovery on PDGF-BB receptor expression which was depressed by $IL-1{\beta}$, $125-250{\mu}g/ml$ of safflower blossom extracts and $250-500{\mu}g/ml$ of safflower seed extracts showed significant increasing effect on MG63 cells, and $500{\mu}g/ml$ of safflower blossom extract and $250-500{\mu}g/ml$ of safflower seed extracts showed significant effect on periodontal ligament cells. In chemotactic response, among all tested group, safflower seed extracts only were chemotactic to MG63 cells and periodontal ligament cells in concentration range of $125-500{\mu}g/ml$. Also in the view of bone regeneration in rat calvarial defect model, the only group that was orally administrated 0.35g/kg, day of safflower seed extract showed significant new bone formation. These results suggested that safflower extracts might have a potential possibilities as an useful drug for adjunct to treatment for regeneration of periodontal defect.

• Journal of Korean Neurosurgical Society
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• v.30 no.9
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• pp.1094-1102
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• 2001

Objective : During the trans-condylar or trans-jugular approach for the lesion of cranio-cervical junction(CCJ), its necessary to identify the accurate locations of vertebral artery(VA), internal jugular vein(IJV) and its related lower cranial nerves. These neurovascular structures can also be damaged during the operation for vascular tumor or traumatic aneurysm around extra-jugular foramen, because of their changed locations. To reduce the neurovascular injury at the operation for CCJ, morphometric relationship of its surrounding neurovascular structures based on the tip of the transverse process of atlas(C1 TP), were studied. Materials & Methods : Using 10 adult formalin fixed cadavers, tip of mastoid process(MT) and TPs of atlas and axis were exposed bilaterally after removal of occipital and posterior neck muscles. Using standard caliper, the distances were measured from the C1 TP to the following structures : 1) exit point of VA from C1 transverse foramen, 2) branching point of muscular artery from VA, 3) entry point of VA into posterior atlanto-occipital membrane(AOM), 4) branching point of C-1 nerve. In addition, the distances were measured from the mid-portion of the posterior arch of atlas to the entry point of the VA into AOM and to the exit point of the VA from C1 transverse foramen. After removal of the ventrolateral neck muscles, neurovascular structures were exposed in the extra-jugular foraminal region. Distances were then measured from the C1 TP to the following structures : 1) just extra-jugular foraminal IJV and lower cranial nerves, 2) MT and branching point of facial nerve in parotid gland. In addition, distance between MT and branching point of facial nerve was measured. Results : The VA was located at the mean distance of 12mm(range, 10.5-14mm) from the C1 transverse foramen and entered into the AOM at the mean distance of 24mm(range, 22.8-24.4mm) from the C1 TP. The mean distance from the mid portion of the C1 posterior arch was 20.6mm(range, 19.1-22.3mm) to the entry point of the VA into AOM and 38.4mm(range, 34-42.4mm) to the exit point of the VA from C1 transverse foramen. Muscular artery branched away from the posterior aspect of the transverse portion of VA below the occipital condyle at the mean distance of 22.3mm(range, 15.3-27.5mm) from the C1 TP. The C-1 nerve was identified in all specimens and ran downward through the ventroinferior surface of the transverse segment of VA and branched at the mean distance of 20mm(range, 17.7-20.3mm) from the C1 TP. The IJV was located at the mean distance of 6.7mm(range, 1-13.4mm) ventromedially from the lateral surface of the C1 TP. The XI cranial nerve ran downward on the lateral surface of the IJV at the mean distance of 5mm(range, 3-7.5mm) from the C1 TP. Both IX and X cranial nerves were located in the soft tissue between the medial aspect of the internal carotid artery(ICA) and the medial aspect of the IJV at the mean distance of 15.3mm(range, 13-24mm) and 13.7mm(range, 11-15.4mm) from the C1 TP, respectively. The IX cranial nerve ran downward ventroinferiorly crossing the lateral aspect of the ICA. The X cranial nerve ran downward posteroinferior to the IX cranial nerve and descended posterior to the ICA. The XII cranial nerve was located between the posteroinferior aspect of the IX cranial nerve and the posterior aspect of the ICA at the mean distance of 13.3mm(range, 9-15mm) ventromedially from the C1 TP. The distance between MT and C1 TP was 17.4mm(range, 12.5-23.9mm). The VII cranial nerve branched at the mean distance of 10.2mm(range, 6.8-15.3mm) ventromedially from the MT and at the mean distance of 17.3mm(range, 13-21mm) anterosuperiorly from the C1 TP. Conclusion : This study facilitates an understanding of the microsurgical anatomy of CCJ and may help to reduce the neurovascular injury at the surgery around CCJ.

• Journal of Korean Neurosurgical Society
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• v.46 no.4
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• pp.370-377
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• 2009

Objective : There is no definite adjustment protocol for patients shunted with programmable valves. Therefore, we attempted to find an appropriate method to adjust the valve, initial valve-opening pressure, adjustment scale, adjustment time interval, and final valve-opening pressure of a programmable valve. Methods : Seventy patients with hydrocephalus of various etiologies were shunted with programmable shunting devices (Micro Valve with $RICKHAM^{(R)}$ Reservoir). The most common initial diseases were subarachnoid hemorrhage (SAH) and head trauma. Sixty-six patients had a communicating type of hydrocephalus, and 4 had an obstructive type of hydrocephalus. Fifty-one patients had normal pressure-type hydrocephalus and 19 patients had high pressure-type hydrocephalus. We set the initial valve pressure to $10-30\;mmH_2O$, which is lower than the preoperative lumbar tapping pressure or the intraoperative ventricular tapping pressure, conducted brain computerized tomographic (CT) scans every 2 to 3 weeks, correlated results with clinical symptoms, and reset valve-opening pressures. Results : Initial valve-opening pressures varied from 30 to $180\;mmH_2O$ (mean, $102{\pm}27.5\;mmH_2O$). In high pressure-type hydrocephalus patients, we have set the initial valve-opening pressure from 100 to $180\;mmH_2O$. We decreased the valve-opening pressure $20-30\;mmH_2O$ at every 2- or 3-week interval, until hydrocephalus-related symptoms improved and the size of the ventricle was normalized. There were 154 adjustments in 81 operations (mean, 1.9 times). In 19 high pressure-type patients, final valve-opening pressures were $30-160\;mmH_2O$, and 16 (84%) patients' symptoms had nearly improved completely. However, in 51 normal pressure-type patients, only 31 (61%) had improved. Surprisingly, in 22 of the 31 normal pressure-type improved patients, final valve-opening pressures were $30\;mmH_2O$ (16 patients) and $40\;mmH_2O$ (6 patients). Furthermore, when final valve-opening pressures were adjusted to $30\;mmH_2O$, 14 patients symptom was improved just at the point. There were 18 (22%) major complications : 7 subdural hygroma, 6 shunt obstructions, and 5 shunt infections. Conclusion : In normal pressure-type hydrocephalus, most patients improved when the final valve-opening pressure was $30\;mmH_2O$. We suggest that all normal pressure-type hydrocephalus patients be shunted with programmable valves, and their initial valve-opening pressures set to $10-30\;mmH_2O$ below their preoperative cerebrospinal fluid (CSF) pressures. If final valve-opening pressures are lowered in 20 or $30\;mmH_2O$ scale at 2- or 3-week intervals, reaching a final pressure of $30\;mmH_2O$, we believe that there is a low risk of overdrainage syndromes.

• Journal of Nutrition and Health
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• v.47 no.1
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• pp.33-44
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• 2014

Purpose: Elevated serum phosphorus and potassium levels are a major problem for hemodialysis (HD) patients. Hyperphosphatemia and hyperkalemia are closely related to intake of dietary phosphorus and potassium. Methods: This study was conducted in order to investigate the effects of food consumed on serum phosphorus and potassium levels in 48 HD patients (20 males and 28 females). We collected anthropometric data, biochemical parameters, and dietary data of the subjects. Dietary data for usual intake were obtained by use of a food-frequency questionnaire (FFQ) consisting of 21 food items. Results: The mean body mass index (BMI) was $22.2{\pm}3.0kg/m^2$, mean serum phosphorus level was $4.50{\pm}1.52mg/dl$, and mean serum potassium level was $4.74{\pm}0.73mEq/l$. Hyperphosphatemia (> 4.5 mg/dl) was found in 45.8% of subjects, and hyperkalemia (> 5.0 mEq/l) in 35.4%. Subjects who took medication only were 56% of total, and those who took medication with dietary therapy were 27%. Patients with medication and dietary therapy showed significantly lower serum phosphorus levels compared to patients with medication only (p < 0.05). Mean duration of HD was $7.9{\pm}7.3$ years and it showed positive correlation with serum potassium levels (p < 0.05). Serum phosphorus levels showed positive correlation with intake of mixed grains and soybean milk (p < 0.05). Serum potassium levels showed positive correlation with intake of mixed grains (p < 0.01), potatoes, fish, and high-potassium vegetables (p < 0.05). On the other hand, intake of white rice showed negative correlation with serum potassium levels (p < 0.05). Conclusion: The results of our study suggest that intake of white rice rather than mixed grains is an important factor in sustaining normal serum phosphorus and potassium levels. In addition, limiting intake of soybean milk, potatoes, and fish to under three serving per week is recommended. Finally, conduct of a strict dietary therapy along with medical treatment is desirable because inappropriate food intake increases serum phosphorus and potassium levels to a higher than normal range.

• Clinical and Experimental Pediatrics
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• v.50 no.7
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• pp.672-677
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• 2007

Purpose : To assess the prevalence and characteristics of headache comorbidity with epilepsy in children and adolescents in a specialty epilepsy clinic. Methods : Two hundred twenty nine consecutive patients attending the Chosun University Hospital Pediatric Epilepsy Clinic (mean age $10.0{\pm}4.1\;years$, range 4-17, M:F ratio 1.1:1.0) were interviewed with a standardized headache questionnaire. Headache was classified according to the International Classification of Headache Disorders, 2nd Edition and epilepsy was classified according to the International League Against Epilepsy. Disability was assessed using pediatric migraine disability assessment (PedMIDAS). Results : Of the 229 epilepsy patients, 86 (37.6%) had co-morbid headache. Of the headache patients, 64 (74.4%) had migraine (65.6%- migraine without aura, 20.3% - migraine with aura, 14.1% - probable migraine). The mean headache frequency was $7.2{\pm}8.4$ per month, mean duration was $2.2{\pm}4.0$ hours, mean severity was $5.2{\pm}2.2$ out of 10, and mean PedMIDAS score was $13.0{\pm}35.4$. The proportion of females was not higher in epilepsy with headache patients (48.8%) compared to epilepsy patients alone (48.0%). In the patients with migraine, 48.4% had complex partial seizures, 17.2% had simple partial seizures, and 34.4% had generalized seizures (P=0.368). A postictal association of migraine was reported in 18.8% with 17.2% reporting a preictal headache, and 7.8% reporting an ictal headache. Conclusion : The prevalence of headache in pediatric epilepsy is higher than that in general pediatric population, suggesting a co-morbidity of headache in epilepsy patients with migraine being the most frequent headache disorder. Altered cerebral excitability resulting in an increased occurrence of spreading depression may explain the headache comorbidity with epilepsy. Further studies are needed to assess the etiology of this co-morbidity as well as assess the frequency, duration, severity and disability response to antiepileptic drugs.

• Proceedings of the Korean Society for Applied Microbiology Conference
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• 2005.06a
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• pp.154-164
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• 2005

Saccharomyces cerevisiae KNU5377 is a thermotolerant strain, which can ferment ethanol from wasted papers and starch at 40$^{\circ}C$ with the almost same rate as at 30$^{\circ}C$. This strain showed alcohol fermentation ability to convert wasted papers 200 g (w/v) to ethanol 8.4% (v/v) at 40$^{\circ}C$, meaning that 8.4% ethanol is acceptable enough to ferment in the industrial economy. As well, all kinds of starch that are using in the industry were converted into ethanol at 40$^{\circ}C$ with the almost same rate as at 30$^{\circ}C$. Hyperthermic cell killing kinetics and differential scanning calorimetry (DSC) revealed that exponentially growing cells of this yeast strain KNU5377 were more thermotolerant than those of S. cerevisiae ATCC24858 used as a control. This intrinsic thermotolernace did not result from the stability of entire cellular components but possibly from that of a particular target. Heat shock induced similar results in whole cell DSC profiles of both strains and the accumulation of trehalose in the cells of both strains, but the trehalose contents in the strain KNU5377 were 2.6 fold higher than that in the control strain. On the contrary to the trehalose level, the neutral trehalase activity in the KNU5377 cells was not changed after the heat shock. This result made a conclusion that though the trehalose may stabilize cellular components, the surplus of trehalose in KNU5377 strain was not essential for stabilization of whole cellular components. A constitutively thermotolerant yeast, S. cerevisiae KNU5377, was compared with a relatively thermosensitive control, S. cerevisiae ATCC24858, by assaying the fluidity and proton ATPase on the plasma membrane. Anisotropic values (r) of both strains were slightly increased by elevating the incubation temperatures from 25$^{\circ}C$ to 37$^{\circ}C$ when they were aerobically cultured for 12 hours in the YPD media, implying the membrane fluidity was decreased. While the temperature was elevated up to 40$^{\circ}C$, the fluidity was not changed in the KNU5377 cell, but rather increased in the control. This result implies that the plasma membrane of the KNU5377 cell can be characterized into the more stabilized state than control. Besides, heat shock decreased the fluidity in the control strain, but not in the KNU5377 strain. This means also there's a stabilization of the plasma membrane in the KNU5377 cell. Furthermore, the proton ATPase assay indicated the KNU5377 cell kept a relatively more stabilized glucose metabolism at high temperature than the control cell. Therefore, the results were concluded that the stabilization of plasma membrane and growth at high temperature for the KNU5377 cell. Genome wide transcription analysis showed that the heat shock responses were very complex and combinatory in the KNU5377 cell. Induced by the heat shock, a number of genes were related with the ubiquitin mediated proteolysis, metallothionein (prevent ROS production from copper), hsp27 (88-fold induced remarkably, preventing the protein aggregation and denaturation), oxidative stress response (to remove the hydrogen peroxide), and etc.

• Radiation Oncology Journal
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• v.25 no.4
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• pp.206-212
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• 2007

Purpose: Heterotopic ossification is a well-known postoperative and post-traumatic complication of the elbow. We reviewed the treatment outcome for the use of low-dose radiation after surgical intervention of the elbow to prevent recurrence of heterotopic ossification (HO). Materials and Methods: Forty-five patients with HO underwent surgical intervention and postoperative radiotherapy of the elbow. The median age of the patients was 29 years ($16{\sim}75$ years), and 27 of the patients were men and 18 were women. The occurrence of HO was mainly due to surgery after fracture (24/45) and traumatic injury (21/45). Limitation of the range of motion (ROM) was the most common symptom of the patients. Thirty-four patients received postoperative radiotherapy with a dose of 8 Gy in 2 fractions; 5 patients received a dose of 10 Gy in 5 fractions and 6 patients received a dose of 7 Gy in 1 fraction. Postoperative radiotherapy was given on the first two postoperative days for most of the patients. Sixteen patients were not given anti-inflammatory medication and 29 patients were given NSAIDs for $1{\sim}8$ months. Results: After a median follow-up period of 18 months (range $6{\sim}72$ months), 41 patients showed clinical improvement and two patients did not show improvement. Assessment of the ROM showed a mean improvement from $0{\sim}135^{\circ}$ to $60{\sim}145^{\circ}$ (p=0.028), and assessment of the functional outcome according to MEPI was from ($15{\sim}95$) to ($80{\sim}100$) (p<0.0001). Two of the 34 patients that were followed-up with radiography had mild radiological recurrence of heterotopic ossification. No complications were observed after the radiotherapy. Conclusion: These results suggested that low-dose radiation administered after surgical intervention is safe and effective to prevent the recurrence of HO in the elbow.

• Journal of radiological science and technology
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• v.27 no.3
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• pp.31-41
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• 2004

Attention deficit hyperactivity disorder(ADHD)is one of the most common psychiatric disorders in childhood, especially school age children and persisting into adult. ADHD is affected 7.6% in our children, Korea. and persisting into $15{\sim}20%$ in adult. And it is characterized by hyperactivity, inattention and impulsivity. Brain imaging is one of way to diagnosis for ADHD. Brain imaging studies may be provide information two types - structural and functional imaging. Structural and functional images of the brain play an important role in management of neurologic and psyciatric disorders. Brain SPECT, with perfusion imaging radiopharmaceuticals is one of the appropriate test to diagnosis of neurologic and psychiatric diseases. Ther are a few studies about separated analysis between boys and girls ADHD SPECT brain images. Selection of Probability level(P-value) is very important to determind the abnormalities when analysis a data by SPM. SPM is a statistical method used for image analysis and determine statistical different between two groups-normal and ADHD. Commonly used P-value is P<0.05 in statistical analysis. The purpose of this study is to evaluation of blood flow clusters distribution, between boys and girls ADHD. The number of normal boys are 8(6-7y, average : $9.6{\pm}3.9y$) and 51(4-11y, average : $9.0{\pm}2.4$) ADHD patients, and normal girls are 4(6-12y, average : $9{\pm}2.4y$) and 13(2-13y, average $10{\pm}3.5y$) ADHD patiens. Blood flow tracer $^{99m}Tc-ethylcysteinate$ dimer(ECD) injected as rCBF agent and take blood flow images after 30 min. during sleeping by SPECT camera. The anatomical region of hyperperfusion of rCBF in boys ADHD group is posterior cingulate gyrus and hyperperfusion rate is 15.39-15.77% according to p-value. And girls ADHD group appears at posterior cerebellum, Lt. cerbral limbic lobe and Lt. Rt. cerebral temporal lobe. These areas hyperperfusion rate are 24.68-31.25%. Hypoperfusion areas in boys ADHD,s brain are Lt. cerebral insular gyrus, Lt. Rt. frontal lobe and mid-prefrontal lobe, these areas decresed blood flow as 15.21-15.64%. Girls ADHD decreased blood flow regions are Lt. cerebral insular gyrus, Lt. cerebral frontal and temporal lobe, Lt. Rt. lentiform nucleus and Lt. parietal lobe. And hypoperfusion rate is 30.57-30.85% in girls ADHD. The girls ADHD group's perfusion rate is more variable than boys. The studies about rCBF in ADHD, should be separate with boys and girls.

• Asia pacific journal of information systems
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• v.21 no.4
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• pp.1-25
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• 2011

Internet-based commerce has undergone an explosive growth over the past decade as consumers today find it more economical as well as more convenient to shop online. Nevertheless, the shift in the common mode of shopping from offline to online commerce has caused consumers to have worries over such issues as private information leakage, online fraud, discrepancy in product quality and grade, unsuccessful delivery, and so forth, Numerous studies have been undertaken to examine the role of perceived risk as a chief barrier to online purchases and to understand the theoretical relationships among perceived risk, trust and purchase intentions, However, most studies focus on empirically investigating the effects of trust on perceived risk, with little attention devoted to the effects of perceived risk on trust, While the influence trust has on perceived risk is worth studying, the influence in the opposite direction is equally important, enabling insights into the potential of perceived risk as a prohibitor of trust, According to Pavlou (2003), the primary source of the perceived risk is either the technological uncertainty of the Internet environment or the behavioral uncertainty of the transaction partner. Due to such types of uncertainty, an increase in the worries over the perceived risk may negatively affect trust, For example, if a consumer who sends sensitive transaction data over Internet is concerned that his or her private information may leak out because of the lack of security, trust may decrease (Olivero and Lunt, 2004), By the same token, if the consumer feels that the online merchant has the potential to profit by behaving in an opportunistic manner taking advantage of the remote, impersonal nature of online commerce, then it is unlikely that the merchant will be trusted, That is, the more the probable danger is likely to occur, the less trust and the greater need to control the transaction (Olivero and Lunt, 2004), In summary, a review of the related studies indicates that while some researchers looked at the influence of overall perceived risk on trust level, not much attention has been given to the effects of different types of perceived risk, In this context the present research aims at addressing the need to study how trust is affected by different types of perceived risk, We classified perceived risk into six different types based on the literature, and empirically analyzed the impact of each type of perceived risk upon consumer trust in an online merchant and further its impact upon purchase intentions. To meet our research objectives, we developed a conceptual model depicting the nomological structure of the relationships among our research variables, and also formulated a total of seven hypotheses. The model and hypotheses were tested using an empirical analysis based on a questionnaire survey of 206 college students. The reliability was evaluated via Cronbach's alphas, the minimum of which was found to be 0.73, and therefore the questionnaire items are all deemed reliable. In addition, the results of confirmatory factor analysis (CFA) designed to check the validity of the measurement model indicate that the convergent, discriminate, and nomological validities of the model are all acceptable. The structural equation modeling analysis to test the hypotheses yielded the following results. Of the first six hypotheses (H1-1 through H1-6) designed to examine the relationships between each risk type and trust, three hypotheses including H1-1 (performance risk ${\rightarrow}$ trust), H1-2 (psychological risk ${\rightarrow}$ trust) and H1-5 (online payment risk ${\rightarrow}$ trust) were supported with path coefficients of -0.30, -0.27 and -0.16 respectively. Finally, H2 (trust ${\rightarrow}$ purchase intentions) was supported with relatively high path coefficients of 0.73. Results of the empirical study offer the following findings and implications. First. it was found that it was performance risk, psychological risk and online payment risk that have a statistically significant influence upon consumer trust in an online merchant. It implies that a consumer may find an online merchant untrustworthy if either the product quality or the product grade does not match his or her expectations. For that reason, online merchants including digital storefronts and e-marketplaces are suggested to pursue a strategy focusing on identifying the target customers and offering products that they feel best meet performance and psychological needs of those customers. Thus, they should do their best to make it widely known that their products are of as good quality and grade as those purchased from offline department stores. In addition, it may be inferred that today's online consumers remain concerned about the security of the online commerce environment due to the repeated occurrences of hacking or private information leakage. Online merchants should take steps to remove potential vulnerabilities and provide online notices to emphasize that their website is secure. Second, consumer's overall trust was found to have a statistically significant influence on purchase intentions. This finding, which is consistent with the results of numerous prior studies, suggests that increased sales will become a reality only with enhanced consumer trust.