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1.
Nano Lett ; 2024 Apr 01.
Article in English | MEDLINE | ID: mdl-38557080

ABSTRACT

Modern semiconductor fabrication is challenged by difficulties in overcoming physical and chemical constraints. A major challenge is the wet etching of dummy gate silicon, which involves the removal of materials inside confined spaces of a few nanometers. These chemical processes are significantly different in the nanoscale and bulk. Previously, electrical double-layer formation, bubble entrapment, poor wettability, and insoluble intermediate precipitation have been proposed. However, the exact suppression mechanisms remain unclear due to the lack of direct observation methods. Herein, we investigate limiting factors for the etching kinetics of silicon with tetramethylammonium hydroxide at the nanoscale by using liquid-phase transmission electron microscopy, three-dimensional electron tomography, and first-principles calculations. We reveal suppressed chemical reactions, unstripping phenomena, and stochastic etching behaviors that have never been observed on a macroscopic scale. We expect that solutions can be suggested from this comprehensive insight into the scale-dependent limiting factors of fabrication.

2.
Pediatr Neonatol ; 2024 Jan 04.
Article in English | MEDLINE | ID: mdl-38262814

ABSTRACT

BACKGROUND: Kawasaki disease (KD) is a systemic inflammatory disease characterized by vasculitis. In South Korea, some pediatric doctors empirically prescribe steroids to control febrile pediatric patients. This study aimed to evaluate the clinical characteristics of patients with KD after steroid exposure. METHODS: This was a single-center, retrospective, observational study. This study included patients (aged ≤15 years) between January 2020 and July 2022. We compared two groups, one group exposed to steroids and the other group who were not, using the Student's t-test or analysis of variance; otherwise, the Mann-Whitney U test or Kruskal-Wallis test was conducted. Statistical significance was set at p < 0.05. RESULTS: In total, 190 patients with KD were enrolled; of these, 64 (33.7 %) had a history of steroid exposure, and 126 (66.3 %) had no history of steroid exposure. In the steroid exposure group, prolonged fever duration (6.72 ± 1.72 versus 5.61 ± 1.19, p-value = <0.001), a lower proportion of complete KD (29.69 % vs. 88.10 %, p-value = <0.001), and a significantly lower level of C-reactive protein were observed. However, no significant correlations were observed between the Transthoracic Echocardiography (TTE) results (coronary artery aneurysm, existence of pericardial effusion) and prognostic factors (days of hospitalization, the number of intravenous immunoglobulin administrations, and Kobayashi score) between the two groups. CONCLUSIONS: Patients with KD and previous steroid exposure may exhibit an incomplete KD phenotype with prolonged fever. Although previous steroid exposure does not affect the prognosis of KD, including coronary artery aneurysms, it may mask the classic features of KD, resulting in a delayed diagnosis.

3.
Psychiatry Investig ; 19(9): 754-762, 2022 Sep.
Article in English | MEDLINE | ID: mdl-36202111

ABSTRACT

OBJECTIVE: Religious behaviors are considered as complex brain-based phenomena that may be associated with structural brain change. To identify the pattern of regional brain volume change in nuns, we investigated structural alterations in the brains of nuns using a fast processing automated segmentation method based on deep learning algorithms. METHODS: We retrospectively reviewed the medical records of the catholic sisters between the ages of 31 and 80 who are members of the charity of St. Vincent de Paul of Korea. A total of 193 asymptomatic subjects (86 nuns and 107 control subjects) received comprehensive health screening and underwent brain MRI scans. We compared cortical and sub-cortical volume between groups across multiple locations using our in-house U-Net++ deep learning-based automatic segmentation tool. RESULTS: Compared to the control group, the nun group displayed increased gray matter volume in the right lingual cortex, left isthmus-cingulate, posterior-cingulate, rostral-middle-frontal, superior-frontal, supramarginal, temporal-pole cortices, and bilateral pars-triangularis cortices after correction for multiple comparisons. On the other hand, the nun group showed reduced gray matter volume in the temporal and parietal regions relative to healthy controls. CONCLUSION: Our study suggests that spiritual practice may affect brain structure, especially in several frontal regions involved in a higher level of insight function.

5.
Brain Behav Immun ; 89: 641-655, 2020 10.
Article in English | MEDLINE | ID: mdl-32827699

ABSTRACT

Growing evidences show that gut microbiota is associated with the pathogenesis of Parkinson's disease (PD) and the gut-brain axis can be promising target for the development of the therapeutic strategies for PD. Acupuncture has been used to improve brain functions and inflammation in neurological disorders such as PD, and to recover the gastrointestinal dysfunctions in various gastrointestinal disorders. Thus, we investigated whether acupuncture could improve Parkinsonism and gut microbial dysbiosis induced by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine. First, we observed that acupuncture treatment at acupoints GB34 and ST36 could improve motor functions and comorbid anxiety in PD mice. Next, we found that acupuncture increased the levels of dopaminergic fibers and neurons in the striatum and the substantia nigra, respectively. Acupuncture also restored the overexpression of microglia and astrocyte as well as conversion of Bax and Bcl-2 expression in both the striatum and the substantia nigra, indicating that inflammatory responses and apoptosis were blocked by acupuncture. Additionally, via 16S rRNA sequence analysis, we observed that the relative abundance of 18 genera were changed in acupuncture-treated mice compared to the PD mice. Of them, Butyricimonas, Holdemania, Frisingicoccus, Gracilibacter, Phocea, and Aestuariispira showed significant correlations with anxiety as well as motor functions. Furthermore, the predicted functional analyses showed that acupuncture restored the physiology functions such as glutathione metabolism, methane metabolism, and PD pathway. In conclusion, we suggest that the effects of acupuncture on the enhanced motor function and the protection of the dopaminergic neurons may be associated with the regulation of the gut microbial dysbiosis and thus the inhibition of the neuroinflammation in the PD mice.


Subject(s)
Acupuncture Therapy , Gastrointestinal Microbiome , Parkinson Disease , Animals , Disease Models, Animal , Dopaminergic Neurons , Dysbiosis/complications , Mice , Mice, Inbred C57BL , Parkinson Disease/therapy , RNA, Ribosomal, 16S , Substantia Nigra
6.
Brain Stimul ; 12(6): 1556-1564, 2019.
Article in English | MEDLINE | ID: mdl-31378600

ABSTRACT

BACKGROUND: Although some studies have reported significant reductions in food cravings following the single-session of repetitive transcranial magnetic stimulation (rTMS), there is little research on the effects of multi-session of rTMS on food consumption and body weight in obese subjects. OBJECTIVE: We conducted 4-week randomized, sham-controlled, single-blind, parallel-group trial to examine the effect of rTMS on body weight in obese adults. METHODS: Forty-three obese patients (body mass index [BMI] ≥25 kg/m2) aged between 18 and 70 years were randomized to the sham or real treatment group (21 in the TMS group and 22 in the sham treatment group). A total of 8 sessions of rTMS targeting the left dorsolateral prefrontal cortex (DLPFC) was provided over a period of 4 weeks. The primary outcome measure was weight change in kilograms from baseline to 4 weeks. Secondary endpoints included changes in anthropometric measures, cardiovascular risk factors, food intake, and appetite. RESULTS: Participants in the rTMS group showed significantly greater weight loss from baseline following the 8 session of rTMS (-2.75 ±â€¯2.37 kg vs. 0.38 ±â€¯1.0 kg, p < 0.01). Consistent with weight loss, there was a significant reduction in fat mass and visceral adipose tissue at week 4 in the rTMS group compared with the control group (p < 0.01). After the 8 sessions of rTMS, the TMS group consumed fewer total kilocalories and carbohydrates per day than the control group (p < 0.05). CONCLUSIONS: 8 sessions of HF rTMS delivered to the left DLPFC were effective in inducing weight loss and decreasing food intake in obese patients. TRIAL REGISTRATION: Clinical trial registered with the Clinical Trials Registry at http://cris.cdc.go.kr (KCT0002548).


Subject(s)
Body Weight/physiology , Eating/physiology , Obesity/therapy , Transcranial Magnetic Stimulation/methods , Weight Loss/physiology , Adolescent , Adult , Aged , Craving/physiology , Eating/psychology , Female , Humans , Male , Middle Aged , Obesity/physiopathology , Obesity/psychology , Prefrontal Cortex/physiology , Single-Blind Method , Transcranial Magnetic Stimulation/trends , Treatment Outcome , Young Adult
7.
Dev Reprod ; 23(4): 355-365, 2019 Dec.
Article in English | MEDLINE | ID: mdl-31993541

ABSTRACT

The morphogenetically matured spermatozoa (sperm) are generated in the testes by the spermatogenesis. They travel male reproductive tract with many substances secreted from the accessory reproductive organs. One of the substances is the semenogelin (SEMG) released from the seminal vesicles that is involved in the post-testicular maturation. The expression of SEMG gene was investigated in seminal vesicle tissues of sexually matured and regressed male Syrian hamsters by reverse transcription polymerase chain reaction (RT-PCR). The SEMG gene was uniquely identified in the seminal vesicles of the matured Syrian hamsters and compared to the genes reported previously. But the expression of SEMG gene was not observed in reproductively and completely regressed testes of Syrian hamsters. These results indicate that the expressions of the SEMG gene are related to the reproductive capability in the male Syrian hamsters.

8.
Dev Reprod ; 22(3): 253-262, 2018 Sep.
Article in English | MEDLINE | ID: mdl-30324162

ABSTRACT

The spermatogenesis is the process by which spermatozoa are generated in the testes. The spermatozoa travel male reproductive tract during which they meet many substances secreted from reproductive organs. One of the substances is epididymal protease inhibitor (EPPIN) that is involved in the post-testicular maturation including capability of fertilizing the eggs. The expression of EPPIN gene was investigated in various tissues of sexually mature and regressed male Syrian hamsters by reverse transcription polymerase chain reaction (RT-PCR). The EPPIN gene was identified in the testis and epididymis of the male Syrian hamsters and compared to the genes reported previously. There was no expression of EPPIN gene in reproductively and completely regressed testes of Syrian hamster. These results suggest that the expressions of the EPPIN gene are associated with the reproductive capability in the Syrian hamsters.

9.
Brain Stimul ; 11(3): 528-535, 2018.
Article in English | MEDLINE | ID: mdl-29326022

ABSTRACT

BACKGROUND: Although some studies have reported significant reductions in food cravings following repetitive transcranial magnetic stimulation (rTMS), none have examined changes in body weight. OBJECTIVE: We conducted 2-week randomized, sham-controlled, single-blind, parallel-group trial to examine the effect of rTMS on body weight in obese patients. METHODS: Sixty obese patients (body mass index [BMI] ≥25 kg/m2) aged between 18 and 65 years were recruited. A total of 4 sessions of rTMS targeting the left dorsolateral prefrontal cortex (DLPFC) was provided over a period of 2 weeks, with a follow-up assessment conducted two weeks after treatment had finished. The primary outcome measure was weight change in kilograms from baseline to 4 weeks. Secondary endpoints included changes in anthropometric measures, cardiovascular risk factors, food intake, and appetite. RESULTS: Of the 60 volunteers, 57 completed the 4-week follow-up (29 in the TMS group and 28 in the sham treatment group). Participants in the rTMS group showed significantly greater weight loss from baseline following the 4 session of rTMS (p = 0.002). Consistent with weight loss, there was a significant reduction in BMI, fat mass and VAT at week 4 in the rTMS group compared with the control group (p < 0.05). After the 4 sessions of rTMS, the TMS group consumed fewer total kilocalories per day than the control group (p < 0.01). CONCLUSIONS: rTMS delivered to the left DLPFC was effective in decreasing food intake and facilitating weight loss in obese patients. The results of this study suggest that rTMS could be an effective treatment option for obesity. TRIAL REGISTRATION: Clinical trial registered with the Clinical Trials Tegistry at https://cris.nih.go.kr (KCT0001455).


Subject(s)
Body Weight/physiology , Feeding Behavior/physiology , Obesity/physiopathology , Obesity/therapy , Transcranial Magnetic Stimulation , Adolescent , Adult , Aged , Eating/physiology , Female , Humans , Male , Middle Aged , Prefrontal Cortex/physiology , Single-Blind Method , Treatment Outcome , Weight Loss/physiology , Young Adult
10.
Ultrason Sonochem ; 29: 563-7, 2016 Mar.
Article in English | MEDLINE | ID: mdl-26215790

ABSTRACT

We present the results of experimental investigation of ultrasonic washing of textiles. The results demonstrate that cavitation bubbles oscillating in acoustic fields are capable of removing soils from textiles. Since the washing performance is mitigated in a large washing bath when using an ultrasonic transducer, we propose a novel washing scheme by combining the ultrasonic vibration with a conventional washing method utilizing kinetic energy of textiles. It is shown that the hybrid washing scheme achieves a markedly enhanced performance up to 15% in comparison with the conventional washing machine. This work can contribute to developing a novel laundry machine with reduced washing time and waste water.

11.
Brain Tumor Res Treat ; 3(2): 151-5, 2015 Oct.
Article in English | MEDLINE | ID: mdl-26605275

ABSTRACT

Primary extradural meningioma is about 1-2% of all meningiomas. Primary intraosseous meningioma is a rare form of intra-bone tumors that account for approximately 67% of extradural meningiomas. We report a primary intraosseous meningioma of a 69-year-old man who had headaches and a mass on right parietal scalp for the past few months. Remarkably, the brain tissue within the osteolytic cavity of the skull was normal in computed tomography and magnetic resonance images. Resection, duraplasty, and cranioplasty were performed. The patient's symptoms disappeared after surgery, and the histological diagnosis was an osseous meningothelial meningioma (World Health Organization grade I).

12.
Langmuir ; 31(31): 8726-31, 2015 Aug 11.
Article in English | MEDLINE | ID: mdl-26185919

ABSTRACT

We investigate the flow patterns created when a liquid drop contacts a reservoir liquid, which has implications on various physicochemical and biochemical reactions including mixing in microfluidic systems. The localized vortical flow spontaneously triggered by the difference of surface tension between the two liquids is studied, which is thus termed the Marangoni vortex. To quantitatively investigate the strength of vortices, we performed particle image velocimetry (PIV) experiments by varying the surface tension difference, the gap of the flow cell, the density and viscosity of the reservoir liquid, and the size of the drop. A scaling law that balances the interfacial energy of the system with the kinetic energy of the vortical flows allows us to understand the functional dependence of the Marangoni vortex strength on various experimental parameters.

13.
J Korean Neurosurg Soc ; 56(2): 121-9, 2014 Aug.
Article in English | MEDLINE | ID: mdl-25328649

ABSTRACT

OBJECTIVES: Patients with cervical ossification of posterior longitudinal ligament (OPLL) are susceptible to cord injury, which often develops into myelopathic symptoms. However, little is known regarding the prognostic factors that are involved in minor trauma. We evaluated the relationship between minor trauma and neurological outcome of OPLL and investigated the prognostic factors with a focus on compressive factors and intramedullary signal intensity (SI). METHODS: A total of 74 patients with cervical myelopathy caused by OPLL at more than three-levels were treated with posterior decompression surgeries. We surveyed the space available for spinal cord (SAC), the severity of SI change on T2-weighted image, and diabetes mellitus (DM). The neurological outcome using Japanese Orthopedic Association (JOA) scale was assessed at admission and at 12-month follow-up. RESULTS: Among the variables tested, preoperative JOA score, severity of intramedullary SI, SAC, and DM were significantly related to neurological outcome. The mean preoperative JOA were 11.3±1.9 for the 41 patients who did not have histories of trauma and 8.0±3.1 for the 33 patients who had suffered minor traumas (p<0.05). However, there were no significant differences in the recovery ratios between those two groups. CONCLUSIONS: Initial neurological status and high intramedullary SI in the preoperative phase were related to poorer postoperative outcomes. Moreover, the patients with no histories of DM and larger SACs exhibited better improvement than did the patients with DM and smaller SACs. Although the initial JOA scores were worse for the minor trauma patients than did those who had no trauma prior to surgery, minor trauma exerted no direct effects on the surgical outcomes.

14.
J Cerebrovasc Endovasc Neurosurg ; 16(3): 303-8, 2014 Sep.
Article in English | MEDLINE | ID: mdl-25340036

ABSTRACT

Aneurysms arising from non-branching sites of the supraclinoid internal carotid artery (ICA) are considered rare, accounting for only 0.9-6.5% of all ICA aneurysms. They are thin-walled, broad-based, can easily rupture during surgery, and are referred to as dorsal, superior, anterior, or ventral wall ICA aneurysms, as well as blister-like aneurysms. Various treatment modalities are available for blister-like aneurysms, but with varying success. Here, we report on two cases of saccular shaped dorsal wall aneurysms. Both patients were transferred to the emergency department with subarachnoid hemorrhage because of an aneurysmal rupture. Computed tomography angiography and transfemoral cerebral angiography (TFCA) showed a dorsal wall aneurysm in the distal ICA. We performed clipping on the wrapping material (Lyodura®, temporal fascia). Follow-up TFCA showed rapid configuration changes of the right distal ICA. Coil embolization was also performed as a booster treatment to prevent aneurysm regrowth. Both patients were discharged without neurologic deficit. No evidence of aneurysm regrowth was observed on follow-up TFCA at two years. Dorsal wall ICA aneurysms can change in size over a short period; therefore, follow-up angiography should be performed within the short-term. In cases of regrowth, coil embolization should be considered as a booster treatment.

15.
J Korean Neurosurg Soc ; 54(4): 296-301, 2013 Oct.
Article in English | MEDLINE | ID: mdl-24294452

ABSTRACT

OBJECTIVE: We conducted a retrospective study examining the outcomes of intracerebral hemorrhage (ICH) in patients with chronic kidney disease (CKD) to identify parameters associated with prognosis. METHODS: From January 2001 to June 2008, we treated 32 ICH patients (21 men, 11 women; mean age, 62 years) with CKD. We surveyed patients age, sex, underlying disease, neurological status using Glasgow Coma Scale (GCS), ICH volume, hematoma location, accompanying intraventricular hemorrhage, anti-platelet agents, initial and 3rd day systolic blood pressure (SBP), clinical outcome using the modified Rankin Scale (mRS) and complications. The severity of renal functions was categorized using a modified glomerular filtration rate (mGFR). Multifactorial effects were identified by regression analysis. RESULTS: The mean GCS score on admission was 9.4±4.4 and the mean mRS was 4.3±1.8. The overall clinical outcomes showed a significant relationship on initial neurological status, hematoma volume, and mGFR. Also, the outcomes of patients with a severe renal dysfunction were significantly different from those with mild/moderate renal dysfunction (p<0.05). Particularly, initial hematoma volume and sBP on the 3rd day after ICH onset were related with mortality (p<0.05). However, the other factors showed no correlation with clinical outcome. CONCLUSION: Neurological outcome was based on initial neurological status, renal function and the volume of the hematoma. In addition, hematoma volume and uncontrolled blood pressure were significantly related to mortality. Hence, the severity of renal function, initial neurological status, hematoma volume, and uncontrolled blood pressure emerged as significant prognostic factors in ICH patients with CKD.

16.
Korean J Spine ; 10(3): 170-3, 2013 Sep.
Article in English | MEDLINE | ID: mdl-24757481

ABSTRACT

Spontaneous cervical epidural hematoma (SCEDH) is a rare disease, but can cause severe neurologic impairment. We report a case of a 68-year-old female who presented with sudden onset, posterior neck pain, right shoulder pain, and progressive right hemiparesis mimicking stroke with no trauma history. Initial brain CT and diffusion MRI performed to rule out brain lesion did not show any positive findings. Laboratory examination presented only severe thrombocytopenia (45,000/mm(3)). Subsequent cervical MRI revealed a cervical epidural mass lesion. We confirmed that it was pure hematoma through C5 unilateral total laminectomy and C6 partial hemilaminectomy. She achieved complete neurologic recovery with active rehabilitation. Early surgical decompression for SCEDH with neurologic impairment should be recommended for better outcome.

17.
J Korean Neurosurg Soc ; 52(4): 293-9, 2012 Oct.
Article in English | MEDLINE | ID: mdl-23133715

ABSTRACT

OBJECTIVE: To evaluate the surgical efficacy of and factors associated with decompressive craniectomy in patients with an internal carotid artery (ICA) territory infarction. METHODS: Seventeen patients (8 men and 9 women, average age 61.53 years, range 53-77 years) were treated by decompressive craniectomy for an ICA territory infarction at our institute. We retrospectively reviewed medical records, radiological findings, and National Institutes of Health Stroke Scale (NIHSS) at presentation and before surgery. Clinical outcomes were assessed using the Glasgow Outcome Scale (GOS). RESULTS: Of the 17 patients, 15 (88.24%) achieved a poor outcome (Group A, GOS 1-3) and 2 (11.76%) a good outcome (Group B, GOS 4-5). The mortality rate at one month after surgery was 52.9%. Average preoperative NIHSS was 27.6±10.88% in group A and 10±4.24% in group B. Mean cerebral infarction fraction at the septum pellucidum level before surgery in group A and B were 33.67% and 23.72%, respectively. Mean preoperative NIHSS (p=0.019) and cerebral infarction fraction at the septum pellucidum level (p=0.017) were found to be significantly associated with a better outcome. However, no preexisting prognostic factor was found to be of statistical significance. CONCLUSION: The rate of mortality after ICA territory infarction treatment is relatively high, despite positive evidence for surgical decompression, and most survivors experience severe disabilities. Our findings caution that careful consideration of prognostic factors is required when considering surgical treatment.

18.
J Korean Neurosurg Soc ; 51(1): 44-6, 2012 Jan.
Article in English | MEDLINE | ID: mdl-22396843

ABSTRACT

The sternocleidomastoid (SCM) artery supplying blood to the SCM muscle has different origins according to its anatomical segment. The authors performed cadaveric neck dissection to review the surgical anatomy of neurovascular structures surrounding the carotid artery in the neck. During the dissection, an unusual finding was cited in which the SCM artery supplying the middle part of the SCM muscle originated from the lingual artery (LA); it was also noted that it crossed over the hypoglossal nerve (HN). There have been extremely rare reports citing the SCM artery originated from the LA. Though the elevation of the HN over the internal carotid artery was relatively high, the vascular loop crossing over the HN was very close to the carotid bifurcation. Special anatomical consideration is required to avoid the injury of the HN during carotid artery surgery.

19.
Bioelectromagnetics ; 33(4): 356-64, 2012 May.
Article in English | MEDLINE | ID: mdl-22012556

ABSTRACT

Wireless mobile phones and other telecommunication devices are used extensively in daily life. We therefore examined the effects of combined exposure to radiofrequency electromagnetic fields (RF-EMF) on rat testicular function, specifically with respect to sensitive processes such as spermatogenesis. Male rats were exposed to single code division multiple access (CDMA) and wideband code division multiple access (WCDMA) RF signals for 12 weeks. The RF exposure schedule comprised 45 min/day, 5 days/week for a total of 12 weeks. The whole-body average specific absorption rate (SAR) of CDMA and WCDMA was 2.0 W/kg each or 4.0 W/kg in total. We then investigated the correlates of testicular function such as sperm count in the cauda epididymis, testosterone concentration in the blood serum, malondialdehyde concentrations in the testes and epididymis, frequency of spermatogenesis stages, and appearance of apoptotic cells in the testes. We also immunoblotted for p53, bcl2, GADD45, cyclin G, and HSP70 in the testes of sham- and combined RF-exposed animals. Based on the results, we concluded that simultaneous exposure to CDMA and WCDMA RF-EMFs at 4.0 W/kg SAR did not have any observable adverse effects on rat spermatogenesis.


Subject(s)
Electromagnetic Fields/adverse effects , Radio Waves/adverse effects , Testis/physiology , Testis/radiation effects , Animals , Apoptosis/radiation effects , Body Temperature/radiation effects , Cyclin G/metabolism , DNA Damage , Epididymis/metabolism , Epididymis/radiation effects , HSP70 Heat-Shock Proteins/metabolism , Male , Malondialdehyde/metabolism , Organ Size/radiation effects , Oxidative Stress/radiation effects , Rats , Rats, Sprague-Dawley , Sperm Count , Spermatogenesis/radiation effects , Testis/cytology , Testis/metabolism , Testosterone/blood , Time Factors
20.
J Nanosci Nanotechnol ; 11(8): 6946-52, 2011 Aug.
Article in English | MEDLINE | ID: mdl-22103103

ABSTRACT

Single crystalline silicon nanowires (SiNWs) were grown on Si(100) substrate using a gold (Au)-catalyzed vapor-liquid-solid (VLS) approach. The dependence of the growth time (i.e., the time of exposure to the Si source) on the density and surface evolution of the grown SiNWs is considered. It was observed that the density of grown SiNWs on Si substrate increased with increasing growth time. The highest density (approximately 1.1 x 10(6) mm(-2)) was reached at 4 hr. Upon further exposure to the Si source, we observed that the density was maintained for up to 9 hr. We suggest that the increased Si chemical potential in Au-Si droplets with increased growth time enhanced the SiNW growth rate at the interfaces between Au-Si droplets and SiNWs, and enhanced the transition of the NWs from the existing Au-Si droplets onto Si substrate. This allows the SiNW density to increase with increased growth time of up to 4 hr. Moreover, we examined the influence of the growth time on surface evolution including Au diffusion, facet and taper formation, and vapor-solid (VS) growth of the SiNWs. To explain the behavior of the grown SiNWs in the VLS process, we propose a combined model using the VLS and VS growth mechanisms.

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