Testing a priority-based queue model with Linux command histories

We study human dynamics by analyzing Linux history files. The goodness-of-fit test shows that most of the collected datasets belong to the universality class suggested in the literature by a variable-length queueing process based on priority. In order to check the validity of this model, we design two tests based on mutual information between time intervals and a mathematical relationship known as the arcsine law. Since the previously suggested queueing process fails to pass these tests, the result suggests that the modelling of human dynamics should properly consider the statistical dependency in the temporal dimension.Comment: 17 pages, 17 figure

Effects of Microgrooves on the Success Rate and Soft Tissue Adaptation of Orthodontic Miniscrews.

Objective: To evaluate the effect of microgrooves on orthodontic miniscrews in terms of success rate and soft tissue adaptation in animal experiments. Materials and Methods: The sample consisted of a non-microgroove (NMG) group and a microgroove group (MG; 50 μm pitch and 10 μm depth microgroove on the upper surface of the miniscrew). Miniscrews of 1.6 mm diameter and 6.0 mm length were placed into beagle dogs. Histomorphometric analysis in each group focused on bone-to-implant contact (BIC) and the bone area (BA) of pressure and tension sides. Independent and paired t-tests were completed for statistical analysis. Results: The success rate was found to be higher in the MG group than in the NMG group. The MG group showed significantly higher BIC on the pressure side when compared with the NMG group (P < .01). Although the NMG group showed significantly lower BIC on the pressure side than on the tension side at the upper side of the miniscrew (P < .01), the MG group revealed no significant differences between BIC on pressure and tension sides. The MG group generally exhibited perpendicular or circular alignment of the gingival connective tissue fiber with the miniscrew; the NMG group showed parallel alignment. Conclusions: The orthodontic load may affect bone remodeling on the pressure side of the miniscrew and may affect stability. The microgroove could exert some positive effects on soft tissue adaptation and bone healing

Comparison of Stability between Cylindrical and Conical TypeMini-Implants Mechanical and Histologic Properties

Objective: To investigate the mechanical and histologic properties of conical compared with cylindrical shaped mini-implants in terms of the success rate. Materials and Methods: The samples consisted of cylindrical and conical groups, and commonly had 1.6 mm diameter and 6.0 mm length (Jeil Medical Corporation, Seoul, Korea) placed in beagle dogs. The mechanical study for analyzing maximum insertion torque (MIT), maximum removal torque (MRT), and torque ratio (TR; MRT/MIT) in Sawbones (Pacific Research Laboratories Inc, Vashon, Wash), and the animal study for resonance frequency analysis (RFA) and histomorphometric analysis (bone-to-implant contact and bone area) in two beagle dogs were done. All measurements were statistically evaluated using independent t-tests to determine any difference in MIT, MRT, TR, RFA, bone-to-implant contact (BIC), and bone area (BA) between the cylindrical group and conical group. A P value less than 0.05 was considered significant. Results: The conical group showed significantly higher MIT and MRT than the cylindrical group in the mechanical study. However, there was no significant difference in RFA, BIC, and BA between the two groups in the animal and histomorphometric studies. Conclusions: Although the conical shaped mini-implant could induce tight contact to the adjacent bone tissue and might produce good primary stability, the conical shape may need modification of the thread structure and insertion technique to reduce the excessive insertion torque while maintaining the high resistance to removal.This study was supported by grant #03-2006-007 from the SNUDH Research Fund

Immunization Dynamics on a 2-layer Network Model

We introduce a 2-layer network model for the study of the immunization dynamics in epidemics. Spreading of an epidemic is modeled as an excitatory process in a small-world network (body layer) while immunization by prevention for the disease as a dynamic process in a scale-free network (head layer). It is shown that prevention indeed turns periodic rages of an epidemic into small fluctuation. The study also reveals that, in a certain situation, prevention actually plays an adverse role and helps the disease survive. We argue that the presence of two different characteristic time scales contributes to the immunization dynamics observed.Comment: 5 pages, 7 figure

Root and bone response to the proximity of a mini-implant under orthodontic loading

Objective: To determine the histological reaction of the root and bone as a mini-implant approaches the root. Materials and Methods: Two kinds of mini-implants were inserted into the buccal alveolar bone of 4 beagles (2 males and 2 females). The specimens were classified as the near-root group, the PDL contact group, the root contact group, and the root perforation group. Cementum resorption, dentin resorption, cementum repair, cementum growth, ankylosis, root cracking, and root fracture were assessed as the implant neared the root. Results: The incidence of root resorption increased when the mini-implant was less than 0.6 mm from the root in the near-root group and PDL contact group. Root cracking and root fracture occurred in the root contact group and root perforation group. Bone resorption and ankylosis were observed in some specimens. However, some specimens of the PDL contact group and root contact group had cementum growth or little root resorption despite proximity to the root. In the root perforation group, root resorption and ankylosis occurred on the side opposite the insertion. Conclusions: There is a risk of root contact and severe tissue damage from a thick mini-implant and the drilling procedure, either of which can induce root resorption or ankylosis. Use of smaller mini-implants may reduce root contact and tissue damage. However, the small mini-implant may need enhancement of its stability.This study was supported by grant number 11-2009-013 from the SNUBH Research Fund

일측성 구순열 환자에서 3차원 수치사진측량 스캔과 직접계측 방법의 비교

Background: In cleft lip patients, the necessity of a thorough preoperative analysis of facial deformities before reconstruction is unquestioned. The surgical plan of cleft lip patient is based on the information gained from our preoperative anthropometric evaluation. A variety of commercially available three-dimensional (3D) surface imaging systems are currently introduced to us in plastic surgery for these use. However, few studies have been published on the soft tissue morphology of unrepaired cleft infants described by these 3D surface imaging systems.Methods: The purpose of this study is to determine the accuracy of facial anthropometric measurements obtained through digital 3D photogrammetry and to compare with direct anthropometry for measurement in unilateral cleft lip patients. We compared our patients with three measurements of dimension made on both sides: heminasal width, labial height, and transverse lip length.Results: The preoperative measurements were not significantly different in both side of labial height and left side of heminasal width. Statistically significant differences were found on both side of transverse lip length and right side of heminasal width. Although the half of preoperative measurements were significantly different, trends of results showed average results were comparable.Conclusion: This is the first study in Korea to simultaneously compare digital 3D photogrammetry with traditional direct anthropometry in unilateral cleft lip patients. We desire this study could contribute the methodological choice of the many researchers for proper surgical planning in cleft lip reconstruction field.OAIID:oai:osos.snu.ac.kr:snu2013-01/102/0000004298/10SEQ:10PERF_CD:SNU2013-01EVAL_ITEM_CD:102USER_ID:0000004298ADJUST_YN:YEMP_ID:A072100DEPT_CD:852FILENAME:김석화-3d-nose-2013.pdfDEPT_NM:치의과학과SCOPUS_YN:NCONFIRM:

Effects of insertion angle and implant thread type on the fracture properties of orthodontic mini-implants during insertion

Objective: To determine the effects of insertion angle (IA) and thread type on the fracture properties of orthodontic mini-implants (OMIs) during insertion. Materials and Methods: A total of 100 OMIs (self-drilling cylindrical; 11 mm in length) were allocated into 10 groups according to thread type (dual or single) and IA (0 degrees, 8 degrees, 13 degrees, 18 degrees, and 23 degrees) (n = 10 per group). The OMIs were placed into artificial materials simulating human tissues: two-layer bone blocks (Sawbones), root (polymethylmethacrylate stick), and periodontal ligament (Imprint-II Garant light-body). Maximum insertion torque (MIT), total insertion energy (TIE), and peak time (PT) were measured and analyzed statistically. Results: There were significant differences in MIT, TIE, and PT among the different IAs and threads (all P<.001). When IA increased, MIT increased in both thread groups. However, TIE and PT did not show significant differences among 0 degrees, 8 degrees, and 13 degrees IAs in the dual-thread group or 8 degrees, 13 degrees, and 18 degrees IAs in the single-thread group. The dual-thread groups showed higher MIT at all IAs, higher TIE at 0 degrees and 23 degrees IAs, and longer PT at a 23 degrees IA than the single-thread groups. In the 0 degrees, 8 degrees, and 13 degrees IA groups, none of the OMIs fractured or became deformed. However, in the 18 degrees IA group, all the OMIs were fractured or deformed. Dual-thread OMIs showed more fracturing than deformation compared to single-thread OMIs (P < .01). In the 23 degrees IA group, all OMIs penetrated the artificial root without fracturing and deformation. Conclusions: When OMIs contact artificial root at a critical contact angle, the deformation or fracture of OMIs can occur at lower MIT values than those of penetration.OAIID:oai:osos.snu.ac.kr:snu2013-01/102/0000004298/8SEQ:8PERF_CD:SNU2013-01EVAL_ITEM_CD:102USER_ID:0000004298ADJUST_YN:YEMP_ID:A072100DEPT_CD:852CITE_RATE:1.184FILENAME:조일식-백승학.pdfDEPT_NM:치의과학과SCOPUS_YN:YCONFIRM:

Combined effects of aerobic exercise and 40-Hz light flicker exposure on early cognitive impairments in Alzheimer’s disease of 3×Tg mice

Alzheimer’s disease (AD) is a progressive degenerative brain disease and the primary cause of dementia. At an early stage, AD is generally characterized by short-term memory impairment, owing to dysfunctions of the cortex and hippocampus. We previously reported that a combination of exercise and 40-Hz light flickering can protect against AD-related neuroinflammation, gamma oscillations, reduction in Aβ, and cognitive decline. Therefore, we sought to extend our previous findings to the 5-mo-old 3×Tg-AD mouse model to examine whether the same favorable effects occur in earlier stages of cognitive dysfunction. We investigated the effects of 12 wk of exercise combined with 40-Hz light flickering on cognitive function by analyzing neuroinflammation, mitochondrial function, and neuroplasticity in the hippocampus in a 3×Tg-AD mouse model. Five-month-old 3×Tg-AD mice performed 12 wk of exercise with 40-Hz light flickering administered independently and in combination. Spatial learning and memory, long-term memory, hippocampal Aβ, tau, neuroinflammation, proinflammatory cytokine expression, mitochondrial function, and neuroplasticity were analyzed. Aβ and tau proteins levels were significantly reduced in the early stage of AD, resulting in protection against cognitive decline by reducing neuroinflammation and proinflammatory cytokines. Furthermore, mitochondrial function improved, apoptosis was reduced, and synapse-related protein expression increased. Overall, exercise with 40-Hz light flickering was significantly more effective than exercise or 40-Hz light flickering alone, and the improvement was comparable to the levels in the nontransgenic aged-match control group. Our results indicate a synergistic effect of exercise and 40-Hz light flickering on pathological improvements in the hippocampus during early AD-associated cognitive impairment

Effect of frequent laser irradiation on orthodontic pain A single-blind randomized clinical trial

Objective: To analyze the effect of low-level laser therapy (LLLT) on perception of pain after separator placement and compare it with perceptions of control and placebo groups using a frequent irradiation protocol. Materials and Methods: Eighty-eight patients were randomly allocated to a laser group, a light-emitting diode (LED) placebo group, or a control group. Elastomeric separators were placed on the first molars. In the laser and LED groups, first molars were irradiated for 30 seconds every 12 hours for 1 week using a portable device. Pain was marked on a visual analog scale at predetermined intervals. Repeated measure analysis of variance was performed for statistical analysis. Results: The pain scores of the laser group were significantly lower than those of the control group up to 1 day. The pain scores in the LED group were not significantly different from those of the laser group during the first 6 hours. After that point, the pain scores of the LED group were not significantly different from those of the control. Conclusions: Frequent LLLT decreased the perception of pain to a nonsignificant level throughout the week after separator placement, compared with pain perception in the placebo and control groups. Therefore, LLLT might be an effective method of reducing orthodontic pain.OAIID:oai:osos.snu.ac.kr:snu2013-01/102/0000004298/6SEQ:6PERF_CD:SNU2013-01EVAL_ITEM_CD:102USER_ID:0000004298ADJUST_YN:YEMP_ID:A072100DEPT_CD:852CITE_RATE:1.184FILENAME:ao_july,_laser.pdfDEPT_NM:치의과학과SCOPUS_YN:YCONFIRM: