Foot Tapping Test as a Simple Quantitative Index of Motor Function for Lumbosacral Radiculopathy.

STUDY DESIGN: We conducted a retrospective review of data from patients who underwent surgical treatment for lumbosacral radiculopathy. OBJECTIVE: To assess the effectiveness of the foot tapping test (FTT) in evaluating lower limb motor function in patients with lumbosacral radiculopathy pre- and post-surgery. SUMMARY OF BACKGROUND DATA: Lumbosacral radiculopathy is becoming increasingly common in aging populations. Despite standard treatments, paralysis often leads to incomplete postoperative recovery, necessitating early detection and interventions. METHODS: We enrolled individuals who underwent surgery for lumbosacral radiculopathy at our facility between 2009 and 2020. Patients with a history of lumbar surgeries, dialysis, rheumatoid arthritis, and transitional vertebrae were excluded. The FTT score was measured by having the sole of the foot tap as many times as possible for 10 s while keeping the heel in contact with the floor. The L4, L5, and S1 groups were assigned using the scores on the side of the radiculopathy, and the control group was assigned using the scores on the intact side. Data were analyzed using Dunnett's test for group comparisons and paired t-tests for pre-post-surgery comparisons. RESULTS: Of the 522 eligible patients, 80 (159 nerve roots, one patient with hemi-prosthetic leg) were analyzed. The preoperative FTT scores in the L4 and L5 groups were significantly lower than those in the control group, indicating functional impairment. One year post-surgery, all groups showed improvements in FTT scores, with the L5 group exhibiting significant improvements compared to the control; this was supported by the results of sensitivity analyses considering the effects of paralysis and pain. CONCLUSION: The FTT is a valuable tool for the early detection of lower limb motor dysfunction in lumbosacral radiculopathy, particularly for L5 nerve root impairment, where it aids in timely surgical intervention and may improve postoperative outcomes and quality of life.

A reduction method for anterior opening displacement in thoracolumbarvertebral fractures with diffuse idiopathic skeletal hyperostosis using the skull clamp-assisted position.

Diffuse idiopathic skeletal hyperostosis (DISH) frequently occurs in the spine, resulting in unstable fractures. Treating thoracolumbar fractures in patients with DISH is often difficult because the anterior opening of the vertebral body is exacerbated by dislocation in the prone position, making reduction difficult. In this study, we introduced a novel skull clamp-assisted positioning (SAP) technique. The patient is placed in a supine position with a skull clamp used in cervical spine surgery before surgery to prevent the progression of dislocation and to restore the patient's position. Using this method, the mean difference in local kyphosis angle improved from -2.9 (±8.4)° preoperatively to 10.9 (±7.7)° postoperatively. Furthermore, posterior displacement decreased from a preoperative mean of 5.5 (±4.3) mm to 0.3 (±0.7) mm postoperatively. Complications such as neurological sequelae, implant fracture, and surgical site infection were not observed through one year of postoperative follow-up. SAP may decrease invasiveness and complications. Longer-term studies and larger sample sizes are needed to establish long-term efficacy and benefits.

Assessment of Lumbar Spinal Stenosis as a Risk Factor for Development of Sleep Disorder: The Locomotive Syndrome and Health Outcome in Aizu Cohort Study (LOHAS).

Purpose: Insomnia has been reported to coexist with various musculoskeletal disorders. Although lumbar spinal stenosis (LSS) is the most frequently operated on spinal disease, the causal relationship between LSS and development of sleep disorders remains unclear due to lack of longitudinal studies. This study aimed to determine whether LSS was a risk factor for developing new sleep disorders, primarily insomnia, using a prospective cohort of community residents. Patients and Methods: This study was a prospective cohort study. Participants aged ≥65 years from the "Locomotive Syndrome and Health Outcomes in Aizu Cohort Study (LOHAS)" conducted in 2008 formed our study population. LSS was diagnosed using the self-administered, self-reported history questionnaire, a validated diagnostic support tool for LSS. Sleep disorder was investigated using a questionnaire during the 2-year follow-up. The impact of LSS on sleep disorder onset was analyzed after adjusting for potential confounders, such as age, sex, obesity, hypertension, diabetes, depression, and smoking habits, using propensity score matching. Results: Of the 489 participants who were followed up for two years, 38 (7.8%) had newly developed a sleep disorder in 2010. After adjusting for confounding factors, a comparison of 133 participants each in the control and LSS groups showed significantly higher frequency of new-onset sleep disorders (19 [14.3%] in the LSS group versus 6 [4.5%] in the control group). Conclusion: LSS was found to be an independent risk factor for sleep disorders.

Development of a Novel Diagnostic Support Tool for Degenerative Cervical Myelopathy Combining 10-s Grip and Release Test and Grip Strength: A Pilot Study.

Early diagnosis of degenerative cervical myelopathy (DCM) is desirable, as delayed treatment can cause irreversible spinal cord injury and subsequent activity of daily living (ADL) impairment. We attempted to develop a straightforward and accurate diagnostic tool for DCM by combining the grip and release test (GRT) and grip strength. As a pilot study, we measured the GRT and grip strength of patients with DCM (n = 247) and a control group (n = 721). Receiver operating characteristic analysis was performed using the lower left and right. The Youden index was used to set cutoff values by sex and age group. The diagnostic performance of each test varied by sex and age, and a diagnostic support tool was created to determine any abnormal results in a test. The calculated M/F cutoff values for GRT were as follows: 40-59 years, 21/18; 60-69 years, 17/17; 70-79 years, 15/15; and 80-89 years, 11/12. The calculated M/F cutoff values for grip strength 32/20, 29/13, 21/15, and 19/10. When either GRT or grip strength was judged as positive, the overall sensitivity was 88.2%, specificity was 78.1%, positive likelihood ratio was 4.03, and the negative likelihood ratio was 0.15. This novel diagnostic support tool was superior to using GRT and grip strength alone in the early DCM diagnosis. Future research to obtain age- and sex-specific data is necessary to validate and further improve the tool.

Growth of Single-Walled Carbon Nanotubes from Solid Carbon Nanoparticle Seeds via Cap Formation Engineering with a Two-Step Growth Process and Water Vapor Supply.

Solid carbon nanoparticles are promising growth seeds to prepare single-walled carbon nanotubes (SWCNTs) at high temperatures, at which the SWCNT crystallinity should be improved significantly but conventional metal catalyst nanoparticles are unstable and suffer from aggregation. The noncatalytic nature of solid carbon nanoparticles, however, makes SWCNT growth inefficient, resulting in a limited growth yield. In this study, we develop a two-step chemical vapor deposition process to efficiently synthesize high-crystallinity SWCNTs at high temperatures from solid carbon nanoparticles obtained from nanodiamond. Based on thermodynamic considerations, the growth conditions are separately adjusted to supply different growth driving forces which are suitable for the formation of the initial cap structures and for the stationary elongation of SWCNTs. This process, called cap formation engineering, improves the nucleation density of the cap structures. We examined the changes in crystallinity, amorphous carbon deposition, diameter, and yield of SWCNTs with respect to the synthesis conditions. By controlling the initial growth conditions, high-quality SWCNTs are grown with improved yield. With the addition of water vapor as the etchant, deposition of amorphous carbon at high temperatures was further prevented. The results provide a pathway for precise growth control of SWCNTs from unconventional solid growth seeds.

Scanning probe analysis of twisted graphene grown on a graphene/silicon carbide template.

Overlayer growth of graphene on an epitaxial graphene/silicon carbide (SiC) as a solid template by ethanol chemical vapor deposition is performed over a wide growth temperature range from 900 °C to 1450 °C. Structural analysis using atomic force and scanning tunneling microscopies reveal that graphene islands grown at 1300 °C form hexagonal twisted bilayer graphene as a single crystal. When the growth temperature exceeds 1400 °C, the grown graphene islands show a circular shape. Moreover, moiré patterns with different periods are observed in a single graphene island. This means that the graphene islands grown at high temperature are composed of several graphene domains with different twist angles. From these results, we conclude that graphene overlayer growth on the epitaxial graphene/SiC solid at 1300 °C effectively synthesizes the twisted few-layer graphene with a high crystallinity.

Crossover point of the field effect transistor and interconnect applications in turbostratic multilayer graphene nanoribbon channel.

The electrical transport properties of a turbostratic multilayer graphene nanoribbon (GNR) with various number of layers (1-8 layers) were investigated using a field effect transistor with a single GNR channel. In the turbostratic multilayer GNR with 5 layers or less, the carrier mobility and Ion/Ioff ratio in the FETs were improved by slightly increasing the conductance with increasing the number of layers, meaning that the excellent semiconducting characteristic. The improvement of the carrier transport properties promotes by the turbostratic stacking structure. In the turbostratic multilayer GNR with 6 layers or more, although the Ion/Ioff ratio degraded, the conductance extremely improved with increasing the number of layers. This indicates that the turbostratic multilayer GNR with thicker number of layers becomes the significantly lower resistivity wire as a metallic characteristic. We revealed that the crossover point of the physical properties between the semiconducting and metallic characteristics is determined by the strength to screen the surrounding environment effects such as charged impurity on the substrate. Our comprehensive investigation provides a design guidance for the various electrical device applications of GNR materials.

The Association of Oral Function with Oral Health-Related Quality of Life in University Students: A Cross-Sectional Pilot Study.

The aim of this cross-sectional study was to investigate the association between oral function and oral health-related quality of life (OHRQoL) in healthy university students. Oral functions and OHRQoL (General Oral Health Assessment Index; GOHAI) were investigated in 58 healthy university students. Oral functions, such as tongue pressure, tongue-lip motor function, occlusal force, and masticatory function, were examined. The participants were divided into two groups based on low and high GOHAI scores. Information about oral health, dental caries treatment history, insomnia, and personality and lifestyle was obtained using a self-reported questionnaire. Oral mucosal wetness scores and tongue-lip motor functions (oral diadochokinesis /ka/) were significantly decreased in the low GOHAI score group compared to the high GOHAI score group (p = 0.001 and p = 0.017, respectively). In the logistic regression model, the GOHAI score was independently associated with the oral mucosal wetness score (odds ratio (OR) = 0.622; 95% confidence interval (CI), 0.411-0.941; p = 0.025) and oral diadochokinesis /ka/ (OR = 0.376; 95% CI, 0.170-0.832; p = 0.016). Our study demonstrated the presence of low oral function in university students and suggested its association to low OHRQoL in this population.

Opportune Time of Tooth Extraction in Individuals Requiring Ventricular Assist Device Implantation: A Retrospective Cohort Study.

PURPOSE: Individuals with implantable ventricular assist devices (VADs) are at extremely high risk of bleeding, thromboembolism, and infection after undergoing invasive dental procedures. This study aimed to investigate the systemic and local complications of tooth extraction before and after VAD implantation. PATIENTS AND METHODS: This retrospective cohort study was conducted at a single center. Oral surgical procedures were performed in patients before and/or after left VAD implantation for bridge-to-heart transplantation between April 2013 and December 2017. In this study, the medical charts of the patients were retrospectively reviewed. Data about pre-extraction complete blood count, coagulation profile, biochemical profile, and incidence of local and systemic complications were compared in patients undergoing tooth extraction before VAD implantation (b-VAD group) versus after VAD implantation (a-VAD group). RESULTS: In total, 28 inpatients underwent 36 oral surgical procedures before and/or after VAD implantation. Moreover, 24 tooth extractions were performed in the b-VAD group, and 12 were performed in the a-VAD group. The incidence of post-extraction bleeding was higher in the a-VAD group (P = .001, Mann-Whitney U test), and a significant difference was observed in terms of activated partial thromboplastin time (P = .010, Mann-Whitney U test). Systemic complications associated with VADs included cerebral infarction (n = 2) and driveline infection (n = 1). Post-extraction bleeding was observed within 90 days after VAD implantation in all patients who underwent tooth extraction. CONCLUSIONS: The risk of bleeding after tooth extraction was higher in the a-VAD group (67%) than in the b-VAD group (13%). In 3 cases, VAD-related systemic complications developed within a short period after tooth extraction. The extraction management in the b-VAD group could be controlled without causing any problem. Hence, the opportune time of tooth extraction is before VAD implantation.

Temporal and Spatial Changes of µ-Opioid Receptors in the Brain, Spinal Cord and Dorsal Root Ganglion in a Rat Lumbar Disc Herniation Model.

STUDY DESIGN: Controlled, interventional, animal study. OBJECTIVE: To investigate the spatial and temporal changes of µ-opioid receptor (MOR) expression in a rat lumbar disc herniation (LDH) model. SUMMARY OF BACKGROUND DATA: MORs widely express in the peripheral and central nervous systems, and opioid drugs produce an analgesic effect through their activation. However, the efficacy of opioid drugs is sometimes inadequate in several pathological conditions of pain. MORs in the brain as well as the spinal cord (SC) and dorsal root ganglion (DRG) are thought to be associated with pain-related behavior, but the underlying mechanisms are not completely understood. METHODS: In all, 91 adult female Sprague-Dawley rats were used. Autologous nucleus pulposus (NP) was applied onto the left L5 DRG in the NP group rats. Rats were divided into two surgical groups, the NP and the sham group. The von Frey test of left hind paw was performed before surgery, and 2, 7, 14, 21 and 28 days after surgery. Immunohistochemistry and immunoblotting in the DRG, SC, Caudate putamen, nucleus accumbens (NAc) and periaqueductal grey matter were performed before surgery, and 2, 7, 14, 21 and 28 days after surgery. RESULTS: The thresholds in the NP group were significantly lower than those in the sham group from day 2 onwards. At days 7 and 14, MOR expression in the injured-side SC and DRG were significantly lower than those in the sham group. At day 21, MOR in the NAc was significantly decreased compared to that in the sham group. CONCLUSION: Changes of MOR expression in the NAc, SC and DRG were associated with pain-related behavior. This result might show the underling pathogenesis of the resistance to MOR agonists in the patient with LDH. LEVEL OF EVIDENCE: N/A.

Psychosocial Stress After a Disaster and Low Back Pain-Related Interference With Daily Living Among College Students: A Cohort Study in Fukushima.

STUDY DESIGN: A cohort study. OBJECTIVE: To investigate the association between psychosocial stress and low back pain (LBP)-related interference with daily living among college students. SUMMARY OF BACKGROUND DATA: Few longitudinal studies have examined the likelihood of developing LBP in the presence of a designated psychosocial stressor. All participants in the present study were suddenly affected by the Great East Japan disaster after enrolment in our cohort study. METHODS: The present study was initiated among 95 students at Fukushima Medical University in January 2011. We assessed psychosocial stress in students using the Japanese version of the Perceived Stress Scale (JPSS). Follow-up surveys were conducted in July 2011 and May 2013, analyzing 94 students. Students were then divided into three groups (improved, -19 to -4; Maintained, -3 to +4; Aggravated, +5 to +22) based on the tertile points of JPSS change from baseline to 4 months after the disaster. LBP-related interference with daily living was assessed using the Brief Pain Inventory (BPI) questionnaire. Linear regression modeling was performed with BPI at 4 months after the disaster as the outcome, and JPSS change, sex, history of LBP, baseline physical activity, and baseline BPI as explanatory variables. RESULTS: We found a significant increase in BPI score for the aggravated stress group (ß coefficient, +0.79; 95% confidence interval, +0.06-+1.53), compared with the improved stress group. History of LBP and higher physical activity were also significantly associated with BPI. CONCLUSION: The present study suggests that perceived psychosocial stress induced by the disaster may be associated with LBP-related interference with daily living among college students in Fukushima. LEVEL OF EVIDENCE: 3.

Effect of an Acid-sensing Ion Channels Inhibitor on Pain-related Behavior by Nucleus Pulposus Applied on the Nerve Root in Rats.

STUDY DESIGN: Controlled, interventional animal study. OBJECTIVE: To examine the effect of an inhibitor of acid-sensing ion channel 3 (ASIC3) on pain-related behavior induced by application of the nucleus pulposus (NP) onto the dorsal root ganglion (DRG) in rats. SUMMARY OF BACKGROUND DATA: ASIC3 is associated with acidosis pain in inflamed or ischemic tissues and is expressed in sensory neurons and NP cells. The ASIC3 inhibitor, APETx2, increases the mechanical threshold of pain in models of knee osteoarthritis or postoperative pain. However, the efficacy of APETx2 for pain relief in the NP application model remains unknown. METHODS: Autologous NP was applied to the left L5 nerve root of 183 adult female Sprague-Dawley rats. The DRGs were treated with NP plus one of the following four treatments: saline solution (SM), low (0.01 µg: LD), medium (0.1 µg: MD), or high dose (1.0 µg: HD) of APETx2. Behavioral testing was performed to investigate the mechanical withdrawal threshold using von Frey hairs. Expression of nerve growth factor, hypoxia-inducible factor-1α (HIF1α), activating transcription factor-3, and ionized calcium-binding adaptor molecule-1 was evaluated using immunohistochemistry. Statistical differences among multiple groups were assessed using the Steel test, the Tukey-Kramer test, and the Dunnett test. P < 0.05 were considered significant. RESULTS: The thresholds in the HD group were higher than those in the SM group at Days 14 and 21 (P < 0.05). In the MD group, the threshold was higher than in the SM group at Day 14 (P < 0.05). High doses of APETx2 reduced the expression of HIF1α after Day 14 compared with the SM group (P < 0.05). CONCLUSION: APETx2 significantly improved pain-related behavior in a dose-dependent manner. APETx2 may inhibit ASIC3 and partly inhibit Nav1.8 channels. This ASIC3 channel inhibitor may be a potential therapeutic agent in early-stage lumbar disc herniation. LEVEL OF EVIDENCE: N/A.

Method for Controlling Electrical Properties of Single-Layer Graphene Nanoribbons via Adsorbed Planar Molecular Nanoparticles.

A simple method for fabricating single-layer graphene nanoribbons (sGNRs) from double-walled carbon nanotubes (DWNTs) was developed. A sonication treatment was employed to unzip the DWNTs by inducing defects in them through annealing at 500 °C. The unzipped DWNTs yielded double-layered GNRs (dGNRs). Further sonication allowed each dGNR to be unpeeled into two sGNRs. Purification performed using a high-speed centrifuge ensured that more than 99% of the formed GNRs were sGNRs. The changes induced in the electrical properties of the obtained sGNR by the absorption of nanoparticles of planar molecule, naphthalenediimide (NDI), were investigated. The shape of the I-V curve of the sGNRs varied with the number of NDI nanoparticles adsorbed. This was suggestive of the existence of a band gap at the narrow-necked part near the NDI-adsorbing area of the sGNRs.

Immunohistochemical analysis of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) toxicity on the developmental dentate gyrus and hippocampal fimbria in fetal mice.

Dioxins are widespread persistent environmental contaminants with adverse impacts on humans and experimental animals. Behavioral and cognitive functions are impaired by 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) exposure. TCDD exerts its toxicity via the aryl hydrocarbon receptor (AhR), a ligand-activated transcription factor. The hippocampus, which plays important roles in episodic memory and spatial function, is considered vulnerable to TCDD-induced neurotoxicity, because it contains the AhR. We herein investigated the effects of TCDD toxicity on hippocampal development in embryonic mice. TCDD was administered to dams at 8.5 days postcoitum with a single dose of 20, 200, 2,000 and 5,000 ng/kg body weight (groups T20, T200, T2000 and T5000, respectively), and the brains were dissected from their pups at embryonic day 18.5. Immunohistochemical analysis demonstrated that the Glial Fibrillary Acidic Protein (GFAP) immunoreactivities in the dentate gyrus (DG) were reduced in the T5000 group. Granular GFAP immunoreactivity was observed in the hippocampal fimbria, and the number of immunoreactive fimbria was significantly decreased in the T5000 group. The number of Proliferating Cell Nuclear Antigen (PCNA)-positive cells was decreased in all TCDD-exposed groups and significantly reduced in the T20, T200 and T5000 groups. Together, these results demonstrate that maternal TCDD exposure has adverse impacts on neural stem cells (NSCs), neural precursor cells (NPCs) and granular cells in the DG and disrupts the NSC maintenance and timing of differentiation in the hippocampal fimbria, which in turn interrupt neuronal development in future generations of mice.

Unpredictable chronic stress-induced reproductive suppression associated with the decrease of kisspeptin immunoreactivity in male mice.

Environmental stress affects various parts of mammals typically through the circulation of stress hormones. It has been identified as one of the possible reasons for male reproductive difficulties, but the complex mechanisms responsible for stress-induced reproductive suppression are poorly understood. Here, we examined the relationship between chronic environmental stress and hypothalamic kisspeptin, a recently discovered upstream regulator of the reproductive endocrine feedback system. We studied male mice under an unpredictable chronic stress procedure to replicate the situation of animals under chronic stress. Histological and immunohistochemical analyses were performed focusing on kisspeptin neurons in the arcuate hypothalamic nucleus (ARC) and DNA fragmented cells in seminiferous tubules. Although the ARC was not morphologically altered in either the stressed or non-stressed group, granular kisspeptin immunoreactivities decreased slightly in the stress group. In the testes of the stress group, several signs of testicular degeneration were observed, including increased numbers of ssDNA-positive cells per seminiferous tubule, thinning, vacuoled seminiferous epithelia and multinucleated giant cells. The decreases in kisspeptin in the stress group might be due to other hypothalamic peptides, such as corticotropin-releasing hormone and leptin, whose receptors are known to coexpress in the ARC. In addition, environmental stress directly and indirectly affects testicular function through stress hormones and gonadotropins. In summary, our findings enhance the understanding of stress-induced reproductive suppression possibly mediated by kisspeptin in the ARC.

Selective regulation of the chitin-induced defense response by the Arabidopsis receptor-like cytoplasmic kinase PBL27.

Recognition of microbe-associated molecular patterns (MAMPs) initiates pattern-triggered immunity in host plants. Pattern recognition receptors (PRRs) and receptor-like cytoplasmic kinases (RLCKs) are the major components required for sensing and transduction of these molecular patterns. However, the regulation of RLCKs by PRRs and their specificity remain obscure. In this study we show that PBL27, an Arabidopsis ortholog of OsRLCK185, is an immediate downstream component of the chitin receptor CERK1 and contributes to the regulation of chitin-induced immunity in Arabidopsis. Knockout of PBL27 resulted in the suppression of several chitin-induced defense responses, including the activation of MPK3/6 and callose deposition as well as in disease resistance against fungal and bacterial infections. On the other hand, the contribution of PBL27 to flg22 signaling appears to be very limited, suggesting that PBL27 selectively regulates defense signaling downstream of specific PRR complexes. In vitro phosphorylation experiments showed that CERK1 preferentially phosphorylated PBL27 in comparison to BIK1, whereas phosphorylation of PBL27 by BAK1 was very low compared with that of BIK1. Thus, the substrate specificity of the signaling receptor-like kinases, CERK1 and BAK1, may determine the preference of downstream RLCKs.

Effects of exposure to clothianidin on the reproductive system of male quails.

Clothianidin (CTD) is a neonicotinoid developed in the 1990s as an insecticide having selective toxicity, but it was later found to cause reproductive abnormalities in rats through oxidative stress. There is an attempt to preserve endangered animals, including the Japanese crested ibis, in Japan. However, there is a concern that neonicotinoid affects the reproduction of this bird, since it is used in its habitat. CTD toxicity in the birds is poorly understood, so we investigated whether or not the daily oral administration of CTD has any deleterious effects on the reproductive functions of mature male quails as experimental animals. The animals were randomly divided into four groups of 6 or 7 quails each, treated orally with 0, 0.02, 1 or 50 mg CTD/kg body weight (Control, CTD0.02, CTD1 and CTD50). After that the males bred with untreated females to estimate the egg weights, and rates of fertilization and normal development, the testes, liver and spleen were examined histologically. Vacuolization and the number of germ cells having fragmented DNA in seminiferous tubules, and the number and size of vacuoles in hepatocytes increased dose-dependently. There were no significant differences in egg weights and fertilization rates between the groups, but some eggs of the CTD1 and CTD50 groups failed to develop, and embryonic length decreased dose-dependently. Thus, it was found that CTD affected the reproduction of the male quail through the fragmentation of germ cells and the inhibition or delay of embryonic development.

Influence of nanoparticle size to the electrical properties of naphthalenediimide on single-walled carbon nanotube wiring.

Nanoparticles of N,N'-bis(n-alkyl)tetracarbonatenaphthalenediimide (NDI) were adsorbed on single-walled carbon nanotube (SWNT) wires dispersed on a SiO(2) substrate. The electrical properties were measured along the long axis of the SWNTs, and in all cases through the nanoparticles showed rectification in semiconducting I-V curve. The plateau width of the I-V curve through the NDI nanoparticles on metallic SWNTs decreased as the particle size increased, while the rectification ratio increased. The conduction mechanism was changed from tunneling conduction to Schottky-like conduction and their boundary is at about 3 nm diameter.