Intermediate valence state in YbB4revealed by resonant x-ray emission spectroscopy

We report the temperature dependence of the Yb valence in the geometrically frustrated compoundYbB4from 12 to 300 K using resonant x-ray emission spectroscopy at the YbLα1transition. We find that the Yb valence,v, is hybridized between thev = 2 andv = 3 valence states, increasing fromv=2.61±0.01at 12 K tov=2.67±0.01at 300 K, confirming thatYbB4is a Kondo system in the intermediate valence regime. This result indicates that the Kondo interaction inYbB4is substantial, and is likely to be the reason whyYbB4does not order magnetically at low temperature, rather than this being an effect of geometric frustration. Furthermore, the zero-point valence of the system is extracted from our data and compared with other Kondo lattice systems. The zero-point valence seems to be weakly dependent on the Kondo temperature scale, but not on the valence change temperature scaleT_v.

POS0398 IDENTIFICATION OF THE HLA-B*51:01 IMMUNOPEPTIDOME IN BEHÇET’S DISEASE

Background

Immunopeptidomes are peptides, bound to human leukocyte antigens (HLA), that play a key role in immune responses. HLA-B*51:01 is an HLA allele associated with Behçet’s disease (BD)1. However, the characteristics and the role of HLA-B*51:01 immunopeptidome are not revealed in Behçet’s disease.

Objectives

To investigate the difference of HLA-B*51:01 immunopeptidome between Behçet’s disease and healthy controls (HCs) and to select candidate peptides which have a pathogenic role in Behçet’s disease.

Methods

HLA-bound peptide profiles were established through analysis of plasma samples from HLA-B*51:01–positive BD patients and HCs. HLA-class I molecules were immunoprecipitated, and liquid chromatography-tandem mass spectrometry (LC-MS/MS) was performed. Then, HLA-B*51:01–binding peptides were assessed in terms of binding affinity using NetMHCpan. Finally, the immunological characteristics of selected peptides were analyzed in BD patients and HCs, using ELISpot, flow cytometry, and dextramer staining.

Results

2,306 peptides were present only in BD patients, while 3,145 peptides were detected only in HCs. Immunopeptidome of BD patients preferentially showed hydrophobic amino acids at amino acid position 2 (Figure 1). Ten peptides were selected which were confirmed to be preferentially expressed in BD patients compared with HCs. When bound to HLA-B*51:01 in monocyte-derived dendritic cells (Mo-DCs) or peripheral blood mononuclear cells, these peptides activated T cells and induced surface expression of CD69 and CD107, as well as the secretion of inflammatory cytokines such as interferon (IFN)-γ and tumor necrosis factor (TNF)-α.

Figure 1.

Venn diagram of the identified 8–13-mer peptides and graphs showing the motif clusters. (A) Venn diagram showing the numbers of peptides detected by immunoprecipitation with BD patients or HCs. The number of peptides isolated with isotype antibodies were also depicted. (B) Motif clusters of human leukocyte antigen (HLA)-B*51:01-positive BD patients and HCs.

Conclusion

HLA-B*51:01 immunopeptidome can play a critical role in the development of BD by activating T cells and inducing the secretion of inflammatory cytokines.

References

[1]Takeuchi M, Mizuki N, Meguro A, Ombrello MJ, Kirino Y, Satorius C, et al. Dense genotyping of immune-related loci implicates host responses to microbial exposure in Behcet’s disease susceptibility. Nat Genet49, 438-443 (2017).

Disclosure of Interests

Ye Ji Lee: None declared, Kyung-Cho Cho: None declared, So Hyun Kim: None declared, Byung Kyu Cho: None declared, Eugene C Yi: None declared, Eun Bong Lee Consultant of: EBL has acted as a consultant for Pfizer., Grant/research support from: EBL has received a research grant from GC Pharma, Handok Inc., South Korea.

Tunable asymmetric spin wave excitation and propagation in a magnetic system with two rectangular blocks

Asymmetric spin wave excitation and propagation are key properties to develop spin-based electronics, such as magnetic memory, spin information and logic devices. To date, such nonreciprocal effects cannot be manipulated in a system because of the geometrical magnetic configuration, while large values of asymmetry ratio are achieved. In this study, we suggest a new magnetic system with two blocks, in which the asymmetric intensity ratio can be changed between 0.276 and 1.43 by adjusting the excitation frequency between 7.8 GHz and 9.4 GHz. Because the two blocks have different widths, they have their own spin wave excitation frequency ranges. Indeed, the spin wave intensities in the two blocks, detected by the Brillouin light scattering spectrum, were observed to be frequency-dependent, yielding tuneable asymmetry ratio. Thus, this study provides a new path to enhance the application of spin waves in spin-based electronics.

Robust Surface States and Coherence Phenomena in Magnetically Alloyed SmB_{6}

Samarium hexaboride is a candidate for the topological Kondo insulator state, in which Kondo coherence is predicted to give rise to an insulating gap spanned by topological surface states. Here we investigate the surface and bulk electronic properties of magnetically alloyed Sm_{1-x}M_{x}B_{6} (M=Ce, Eu), using angle-resolved photoemission spectroscopy and complementary characterization techniques. Remarkably, topologically nontrivial bulk and surface band structures are found to persist in highly modified samples with up to 30% Sm substitution and with an antiferromagnetic ground state in the case of Eu doping. The results are interpreted in terms of a hierarchy of energy scales, in which surface state emergence is linked to the formation of a direct Kondo gap, while low-temperature transport trends depend on the indirect gap.

Current-induced magnetic switching with spin-orbit torque in an interlayer-coupled junction with a Ta spacer layer

Spin-orbit torque has attracted considerable attention as a means to overcome limits of devices based on spin-transfer torque. However, a small magnetic field that is collinear to the current flow must be applied to break symmetry and induce deterministic current-induced magnetization switching. Recently, a junction utilizing interlayer coupling mediated by a Ru spacer layer between two CoFe layers was designed for symmetry breaking and exhibited current-induced magnetization switching without a magnetic field. Here, we demonstrate zero-field current-induced switching of the perpendicular magnetization of a Co layer that is indirectly coupled with a CoFe layer via a Ta spacer. The weak interlayer coupling exhibited by Ta allows the layer thickness to be relatively small (≈0.5 nm), enabling appropriate interlayer coupling to induce spin-orbit torque for current-induced magnetic switching. External magnetic field effects on switching characteristics show that the current switching process is quite stable against external environments.

Matching DMFT calculations with photoemission spectra of heavy fermion insulators: universal properties of the near-gap spectra of SmB6

Paramagnetic heavy fermion insulators consist of fully occupied quasiparticle bands inherent to Fermi liquid theory. The gap emergence below a characteristic temperature is the ultimate sign of coherence for a many-body system, which in addition can induce a non-trivial band topology. Here, we demonstrate a simple and efficient method to compare a model study and an experimental result for heavy fermion insulators. The temperature dependence of the gap formation in both local moment and mixed valence regimes is captured within the dynamical mean field (DMFT) approximation to the periodic Anderson model (PAM). Using the topological coherence temperature as the scaling factor and choosing the input parameter set within the mixed valence regime, we can unambiguously link the theoretical energy scales to the experimental ones. As a particularly important result, we find improved consistency between the scaled DMFT density of states and the photoemission near-gap spectra of samarium hexaboride (SmB₆).

Revision anatomical reconstruction of the lateral ligaments of the ankle augmented with suture tape for patients with a failed Broström procedure

AIMS

The aim of this prospective study was to evaluate the intermediate-term outcomes after revision anatomical ankle ligament reconstruction augmented with suture tape for a failed modified Broström procedure.

PATIENTS AND METHODS

A total of 30 patients with persistent instability of the ankle after a Broström procedure underwent revision augmented with suture tape. Of these, 24 patients who were followed up for more than two years were included in the study. There were 13 men and 11 women. Their mean age was 31.8 years (23 to 44). The mean follow-up was 38.5 months (24 to 56) The clinical outcome was assessed using the Foot and Ankle Outcome Score (FAOS) and the Foot and Ankle Ability Measure (FAAM) score. The stability of the ankle was assessed using stress radiographs.

RESULTS

The mean FAOS and FAAM scores improved significantly to 87.5 (73 to 94) and 85.1 (70 to 95) points at final follow-up, respectively (p < 0.001). The mean angle of talar tilt and anterior talar translation improved significantly to 2.8° (0° to 6°) and 4.1 mm (2 to 7) at final follow-up, respectively (p < 0.001). Side to side comparison in stress radiographs at final follow-up showed no significant difference. The revision failed in one patient who underwent a further revision using allograft tendon.

CONCLUSION

The revision modified Broström procedure augmented with suture tape is an effective form of treatment for recurrent instability of the ankle following a failed Broström procedure. This technique provides reliable stability and satisfactory clinical outcomes at intermediate-term follow-up. Cite this article: Bone Joint J 2017;99-B:1183-9.

Field-driven dynamics and time-resolved measurement of Dzyaloshinskii-Moriya torque in canted antiferromagnet YFeO3

Electrical spin switching in an antiferromagnet is one of the key issues for both academic interest and industrial demand in new-type spin devices because an antiferromagnetic system has a negligible stray field due to an alternating sign between sub-lattices, in contrast to a ferromagnetic system. Naturally, questions arise regarding how fast and, simultaneously, how robustly the magnetization can be switched by external stimuli, e.g., magnetic field and spin current. First, the exploitation of ultrafast precessional motion of magnetization in antiferromagnetic oxide has been studied intensively. Regarding robustness, the so-called inertia-driven switching scenario has been generally accepted as the switching mechanism in antiferromagnet system. However, in order to understand the switching dynamics in a canted antiferromagnet, excited by magnetic field, accurate equation of motion and corresponding interpretation are necessary. Here, we re-investigate the inertia-driven switching process, triggered by the strict phase matching between effective driving field, dh/dt, and antiferromagnetic order parameters, l. Such theoretical approaches make it possible to observe the static parameters of an antiferromagnet, hosting Dzyaloshinskii–Moriya (DM) interaction. Indeed, we estimate successfully static parameters, such as DM, exchange, and anisotropy energies, from dynamical behaviour in YFeO₃, studied using terahertz time-domain spectroscopy.

A review of laser and light therapy in melasma

Melasma is a dysregulation of the homeostatic mechanisms that control skin pigmentation and excess pigment is produced. Traditional treatment approaches with topical medications and chemical peels are commonly used but due to the refractory and recurrent nature of melasma, patients often seek alternative treatment strategies such as laser and light therapy. Several types of laser and light therapy have been studied in the treatment of melasma. Intense pulsed light, low fluence Q-switched lasers, and non-ablative fractionated lasers are the most common lasers and light treatments that are currently performed. They all appear effective but there is a high level of recurrence with time and some techniques are associated with an increased risk for postinflammatory hyper- or hypopigmentation. The number and frequency of treatments varies by device type but overall, Q-switched lasers require the greatest number of treatment applications to see a benefit. Vascular-specific lasers do not appear to be effective for the treatment of melasma. Ablative fractionated lasers should be used with caution because they have a very high risk for postinflammatory hypo- and hyperpigmentation. The use of nonablative fractionated laser treatments compared with other laser and light options may result in slightly longer remission intervals. Picosecond lasers, fractional radiofrequency, and laser-assisted drug delivery are promising future approaches to treat melasma. The goal of this review is to summarize the efficacy and safety of the most commonly used laser and light therapies to treat melasma, briefly present future laser-based treatment options for patients with melasma, and provide recommendations for treatment on the basis of the reviewed information.

Application of emitter-sample hybrid terahertz time-domain spectroscopy to investigate temperature-dependent optical constants of doped InAs

We investigate temperature-dependent carrier dynamics of InAs crystal by using reflection-type terahertz time-domain spectroscopy, particularly with a recently developed emitter-sample hybrid structure. We successfully obtain the optical conductivity in a terahertz frequency of bulk InAs whose dc conductivity is in the range of 100-150  Ω^-1 cm^-1. We find that both real and imaginary parts of the optical conductivity can be fit well with the simple Drude model, and the free-carrier density and the scattering rate obtained from the fit are in good agreement with corresponding values obtained by using other techniques, such as the Hall measurement and the dc-resistivity measurement. These results clearly demonstrate that the proposed technique of adopting the emitter-sample hybrid structure can be exploited to determine temperature-dependent optical constants in a reflection geometry and hence to investigate electrodynamics of bulk metallic systems.

Observation of Orbital Order in the Half-Filled 4f Gd Compound

Half-filled electron systems, even with the maximized spin angular moment, have been given little attention because of their zero-orbital angular moment according to Hund's rule. Nevertheless, there are several measurements that show evidence of a nonzero orbital moment as well as spin-orbit coupling. Here we report for the first time the orbital order in a half-filled 4f-electron system GdB_{4}, using the resonant soft x-ray scattering at Gd M_{4,5}-edges. Furthermore, we discovered that the development of this orbital order is strongly coupled with the antiferromagnetic spin order. These results clearly demonstrate that even in half-filled electron systems the orbital angular moment can be an important parameter to describe material properties, and may provide significant opportunities for tailoring new correlated electron systems.

Electronic Structure of YbB_{6}: Is it a Topological Insulator or Not?

To finally resolve the controversial issue of whether or not the electronic structure of YbB_{6} is nontrivially topological, we have made a combined study using angle-resolved photoemission spectroscopy (ARPES) of the nonpolar (110) surface and density functional theory (DFT). The flat-band conditions of the (110) ARPES avoid the strong band bending effects of the polar (001) surface and definitively show that YbB_{6} has a topologically trivial B 2p-Yb 5d semiconductor band gap of ∼0.3  eV. Accurate determination of the low energy band topology in DFT requires the use of a modified Becke-Johnson exchange potential incorporating spin-orbit coupling and an on-site Yb 4f Coulomb interaction U as large as 7 eV. The DFT result, confirmed by a more precise GW band calculation, is similar to that of a small gap non-Kondo nontopological semiconductor. Additionally, the pressure-dependent electronic structure of YbB_{6} is investigated theoretically and found to transform into a p-d overlap semimetal with small Yb mixed valency.

Importance of charge fluctuations for the topological phase in SmB(6)

Typical Kondo insulators (KIs) can have a nontrivial Z_{2} topology because the energy gap opens at the Fermi energy (E_{F}) by a hybridization between odd- and even-parity bands. SmB_{6} deviates from such KI behavior, and it has been unclear how the insulating phase occurs. Here, we demonstrate that charge fluctuations are the origin of the topological insulating phase in SmB_{6}. Our angle-resolved photoemission spectroscopy results reveal that with decreasing temperature the bottom of the d-f hybridized band at the X[over ¯] point, which is predicted to have odd parity and is required for a topological phase, gradually shifts from below to above E_{F}. We conclude that SmB_{6} is a charge-fluctuating topological insulator.

Increased immunoreactivity of membrane type-1 matrix metalloproteinase (MT1-MMP) and β-catenin in high-risk basal cell carcinoma

BACKGROUND

Although various immunohistological markers have been investigated to assess the aggressive characteristics of basal cell carcinoma (BCC), the role of membrane type-1 matrix metalloproteinase (MT1-MMP) has not been well established.

OBJECTIVES

To clarify the precise role of MT1-MMP in BCC, MT1-MMP expression was studied in various histological subtypes of BCC.

MATERIALS AND METHODS

High-risk subtypes of BCC were compared by assessing the expression of β-catenin and MT1-MMP. The tissue microarray technique was used for immunohistochemical staining. Fifty-eight samples were divided into six subtypes (10 nodular, 12 mixed, nine infiltrative, eight morphoeiform, 10 micro-nodular and nine basosquamous). Overall, the 10 nodular BCC samples were classified as low-risk BCC and the remaining 48 samples were classified as high-risk BCCs.

RESULTS

β-Catenin immunoreactivity was increased in the high-risk BCCs compared with the low-risk (nodular) BCC (P < 0·001). Nuclear β-catenin immunoreactivity was increased at the invading front of mixed BCC tumour islands compared with the upper portion of the lesion (P < 0·01). For the mixed BCC (P < 0·01), infiltrative BCC (P < 0·001), morphoeiform BCC (P < 0·001), micronodular BCC (P < 0·001) and basosquamous (P < 0·001) carcinoma, β-catenin immunoreactivity was increased at the invading front compared with nodular BCC. MT1-MMP immunoreactivity was increased in the high-risk BCCs compared with the low-risk (nodular) BCC (P < 0·01). The membranous MT1-MMP immunoreactivity was increased at the invading front of mixed BCC tumour islands compared with the upper portion of the lesions (P < 0·01). For the mixed (P < 0·01), infiltrative (P < 0·05), morphoeiform (P < 0·05), micronodular (P > 0·05) and basosquamous (P < 0·05) BCC, MT1-MMP immunoreactivity was also increased at the invading front compared with nodular BCC.

CONCLUSIONS

The results of this study suggest that MT1-MMP might be a novel marker for high-risk BCC. In addition, expression of both β-catenin and MT1-MMP was increased in high-risk BCC tumour cells, indicating that these two proteins may play an important role in locally invasive and highly destructive growth behaviour of high-risk BCCs.

Pinning characteristics of domain wall in giant magnetoresistance spin valve stripe, consisting of a nano-wire and a circular ring

We investigated a technique for proving the pinning behaviors of a domain wall (DW) in spin-valve stripes with artificial configurations, which consist of a nano-wire, a large pad and sharp tip at the ends of the wire, and a circular ring at the center. It was found from the GMR measurement at various positions that a DW was pinned at a ring during DW's propagation from the side of pad to the side of tip. Micromagnetic simulation revealed that the initial onion magnetic states of the ring changes continuously to final reverse onion state via counterclockwise vortex state when a counterclockwise tail-to-tail DW pass through the ring. In addition, the simulation results indicated that the magnetic states at a circular ring were determined by the type and chirality of DW. We also studied the characteristics of domain wall motion in the same configuration, when the nano-ring was replaced with square and diamond structures.

Current-induced domain wall nucleation and its pinning characteristics at a notch in a spin-valve nanowire

The characteristics of domain wall (DW) pinning at a notch in a spin-valve nanowire were investigated when a DW was created by a current, flowing into a spin-valve nanowire. It was found that DW pinning at a notch is quite sensitive to the magnitude of the current and its polarity. The current-polarity dependence of DW pinning is likely due to the spin structure in the core of the DW, which is determined by an Oersted field from the current in a Cu layer. This indicates that the control of DW pinning at a notch in a nanowire can be achieved by a current acting on its own, which is an important advantage of this method, compared with field-induced DW control.

Magnetic dipolar interaction in NiFe nanodot arrays formed on vertical carbon nanotubes

A new and simple method for the fabrication of densely packed magnetic nanodot arrays was developed using conventional sputtering deposition at room temperature. An anodized alumina template was employed for the formation of nanodot assemblies, consisting of carbon nanotubes (CNTs) and magnetic nanodot arrays. Each nanodot was formed exactly on top of a CNT and was arranged with a well-ordered structure in a wide range of area. It was also found that the size of dots and the distance between dots can be tailored by changing the length of CNTs, inducing a change of strength of dipolar interaction between nanodots.

Characteristics of domain wall pinning and depinning in a three-terminal magnetic Y-junction

The characteristics of domain wall (DW) pinning and propagation in a three-terminal magnetic Y-junction were investigated, where the junction consisted of two input and one output wires. The output switching depends strongly on the junction angle (α). Junctions with high angles of α>9.5° lead to DW pinning at the junction, whereas junctions with low angles of α<9.5° have no DW pinning effect. At the critical angle of α = 9.5°, the Y-junction showed a multimode DW propagation, which was ascribed to a moderate transverse field effect.

Resonant X-ray scattering study of quadrupole-strain coupling in DyB4

X-ray and neutron scattering studies were performed on DyB4 which exhibits both a quadrupolar ordering and a macroscopic lattice distortion. A forbidden reflection at 7.792 keV near the Dy L3 absorption edge is identified as a quadrupolar ordering peak, and the quadrupolar order and a monoclinic structural distortion develop concomitantly below 12.3 K as second-order-type phase transitions. Coupling between the quadrupolar order and the strain in DyB4 is directly demonstrated by observing that both order parameters are proportional to each other.

Investigation of the corticotropin-releasing hormone-proopiomelanocortin axis in various skin tumours

BACKGROUND

Various types of external stress cause the skin and central neuroendocrine system to express corticotropin-releasing hormone (CRH)-proopiomelanocortin (POMC) axis-related hormones. However, the precise role of the CRH-POMC axis-related hormones in various skin tumours is unclear.

OBJECTIVES

This study examined expression patterns of the CRH-POMC axis-related hormones in skin tumours.

METHODS

The production of CRH, adrenocorticotropic hormone (ACTH) and alpha-melanocyte-stimulating hormone (alpha-MSH) in various tumour cell lines including HaCaT and primary keratinocytes was examined using an enzyme-linked immunosorbent assay. Immunohistochemical analysis of the skin tumours was also performed.

RESULTS

CRH, ACTH and alpha-MSH were strongly expressed in malignant skin tumour cell lines such as G-361 and DX-3 (both malignant melanoma, MM). However, normal and haematological malignancy cell lines did not express the CRH-POMC axis-related hormones. Immunohistochemical analysis of the skin tumours showed that MM (80%), squamous cell carcinoma (SCC, 70%) and basal cell carcinoma (BCC, 10%) had strong immunoreactivity (++/+++) for CRH. Strong ACTH and alpha-MSH expression was observed in MM (70% and 50%, respectively), SCC (80% and 60%, respectively) and BCC (70% and 50%, respectively).

CONCLUSIONS

We report that an increase in the level of the CRH-POMC axis-related hormones is associated with malignant skin tumours such as MM. These results highlight the importance of the CRH-POMC axis-related hormones in the malignant tendency of skin tumours.

Insertion of a specular reflective and transmissive nano-oxide layer into giant magnetoresistance spin-valve structure

We have studied the influence of the insertion of a nano-oxide layer (NOL) into a magnetic GMR spin-valve. It was found that the spin-valve with NOL has a higher GMR ratio than that of the normal spin-valve without NOL. Naturally formed NOL without vacuum break shows a uniform layer, which effectively suppresses the current shunt, resulting in the reduction of the sheet resistance of GMR. The NOL spin-valve also shows a lower interlayer coupling (Hin) than that of the optimal normal spin-valve, which is consistent with AFM measurement showing lower roughness of NOL formed CoFe surface. Based on the advantage of NOL, we succeeded in lowering Hin while maintaining GMR ratio by insertion of NOL inside the CoFe free layer, where the free layer consists of CoFe/NOL/CoFe/NOL/Capping layer.

Interference of magnetic and anisotropic tensor susceptibility reflections in resonant X-ray scattering of GdB4

Resonant x-ray scattering experiments at the Gd L3 edge show interference between magnetic and anisotropic tensor susceptibility (ATS) reflections in GdB4. Energy profiles obtained from the magnetic and ATS resonances exhibited approximately 10 eV separation between the maximum resonance energies. The findings show that the Gd 5d band experienced hybridization giving rise to a significant split into isotropic lower energy band and distorted upper band states that account for the magnetic and ATS scattering, respectively.

Protective effects of green tea polyphenol against reactive oxygen species-induced oxidative stress in cultured rat calvarial osteoblast

The injurious effects of reactive oxygen species on osteoblasts and the potential protective role played by green tea polyphenols (GtPP) were investigated using primarily cultured rat calvarial osteoblasts. Oxidative stress was induced in cultured osteoblasts, either by adding 100 mmol/L H2O2 or by the action of 40 U/L xanthine oxidase (XO) in the presence of xanthine (250 micromol/L). After incubation, the cellular viability, function and morphology were evaluated. Both treatments produced a significant reduction in osteoblast viability, as assessed by a two-colored fluorescence staining method combined with flow cytometric analysis and MTT assay. A significant reduction in the alkaline phosphatase activity was observed after H2O2 addition, whereas XO did not have the same effect. On the microscopic observations, the morphological changes and intracellular ultrastructural damages were remarkably induced by both treatments. The H2O2-induced alterations were prevented by pre-incubating the osteoblasts with 200 microg/ml GtPP for 1 h. When the oxidative stress was induced by XO, the cellular viability and morphology was also maintained at the same polyphenol concentration. These results demonstrate that GtPP can act as a biological antioxidant in a cell culture experimental model and protect cells from oxidative stress-induced toxicity.

Intramedullary immature teratoma in a young infant involving a long segment of the spinal cord

Intramedullary teratoma is a rare lesion, located in the majority of cases in the lumbosacral area, and such lesions involving an extensive area of the spinal cord in young infants have seldom been reported. We present the case of a 3-month-old girl with an intramedullary spinal immature teratoma extending from C-5 to T-12, which was totally removed. The patient had suffered from paraplegia for 15 days, after which spinal MRI revealed a heterogeneously enhancing intramedullary lesion. Biopsy of the lesion demonstrated mature intestinal tissue. After total removal of the tumor, paraplegia and sphincter disturbances improved. Intramedullary teratoma should be included in the differential diagnosis of holocord tumors in young infants with rapidly progressing symptoms and if found should be radically excised. This case also emphasizes the importance of histological diagnosis and demonstrates the possibility of neurological recovery even in the case of paraplegia lasting for more than 1 month in a young infant.

Childhood meningioma: unusual location, atypical radiological findings, and favorable treatment outcome

OBJECTS

To investigate the characteristics of childhood meningioma, especially, locations, radiological findings, pathological features (including proliferative potential) and outcome, 11 children with meningiomas were retrospectively analyzed.

RESULTS

Unusual location, large size, frequent calcification, and cyst formation were characteristic radiological findings. Gross total resection was achieved in 8 patients, and there was recurrence in 2. Gamma knife radiosurgery was performed on residual and recurrent tumors. MIB-1 indices tended to be high in large tumors. Nine patients had a Karnofsky Performance Scale of more than 70 during the follow-up period of 10 months to 19.5 years. Surgical treatment rendered 4 of 5 epileptic patients seizure free. The childhood meningiomas examined had unusual locations, atypical radiological findings, and various proliferative potentials.

CONCLUSIONS

Complete resection is the treatment of choice. Gamma knife radiosurgery can be a good alternative for residual tumors and small recurrent tumors. The outcome of childhood meningiomas is good after surgery.

Epidemiologic and clinical survey of Behcet's disease in Korea: the first multicenter study

The prevalence of Behcet's disease is the highest in the East Asian and the Mediterranean countries. Behcet's disease is also distributed in the Asian countries, but the nationwide survey has not been performed in Korea yet. The Korean Study Group for Behcet's Disease, founded in 1999, conducted a multicenter, retrospective survey on epidemiologic and clinical features of the patients with Behcet's disease from 20 hospitals around the nation from 1997 to 1999. Of 3,497 patients, 1,527 were classified into complete or incomplete type of Behcet's disease according to the revised Shimizu's classification. The sex ratio was 1:1.75 with the female predominance. Geographical distribution showed the highest frequency in Seoul (38.5%). Clinically, 98.8% had oral ulcers, 83.2% had genital ulcers, 84.3% had skin lesions and 50.9% had ocular lesions. As for the minor clinical manifestations, articular symptoms were the most frequent. The pathergy test showed positive in 15.4% of patients and revealed a higher positive rate in males (20.2%) than in females (12.7%). In conclusion, we performed the first multicenter study on Behcet's disease in Korea and revealed the female predominance, higher frequency of ocular lesions, and lower positivity of pathergy test in the patients.

A two-year longitudinal study of dental caries in permanent first molars of Korean elementary schoolchildren

OBJECTIVE

This longitudinal study investigated dental caries increment in permanent first molars of Korean elementary schoolchildren.

METHODS

A convenience sample of 722 children aged 7-9 years attending one urban elementary school was examined at baseline, with follow-up examinations at one and two years. Coronal surfaces of permanent first molars were scored with regard to caries experience and sealant status.

RESULTS

Among sound occlusal surfaces at baseline, 21 percent of upper and 25 percent of lower surfaces developed caries during the two-year interval. In teeth that erupted between baseline and the first follow-up exam, over 10 percent of occlusal surfaces developed caries. Pit and fissure caries accounted for 93 percent of all new carious surfaces, while sealants had been placed on 16 percent of occlusal surfaces during the study.

CONCLUSIONS

Recognizing the limitations of this convenience sample, dental sealants should be used more widely in this Korean population, and should be applied soon after tooth eruption.

Radical excision of pediatric craniopharyngioma: recurrence pattern and prognostic factors

The purpose of our study was to investigate the pattern of recurrence and the prognostic factors for recurrence of pediatric craniopharyngiomas after radical excision. A series of 36 patients with craniopharyngiomas (21 boys and 15 girls; age range 1-15 years; mean 7.3 years) were reviewed. All patients had undergone radical excision without radiotherapy. The mean follow-up period was 52 months (range 1-149 months). Tumors recurred in 14 patients within 83 months (mean 31.4 months). The overall 5-year recurrence-free survival rate was 55%. Regular neuroimaging follow-up detected tumor recurrence while the lesions were still small before symptoms developed (P<0.05). At the first surgical procedure, the optic nerve/chiasm (n=23) was the most common adhesion site. The most frequent sites of recurrence were the optic nerve/chiasm (n=6) and the pituitary fossa (n=6). Tumor location was the single significant clinical predictor of recurrence. The 5-year recurrence-free survival rate was 39% for those who had an intrasellar tumor component and 81% for those who did not (P<0.05). The Ki-67 labeling indices (LIs) of primary tumors did not have prognostic value for recurrence. Recurrent tumors tended to have higher Ki-67 LIs than their primary counterparts. On the basis of this study, we concluded that craniopharyngiomas with intrasellar components should be followed cautiously and the necessity for regular follow-up should be emphasized, even when the tumor is "totally" resected.