Eun-Seob Kim

The effects of moisture and temperature on the mechanical properties of additive manufacturing components: fused deposition modeling

Purpose This paper aims to investigate the water absorption behaviors and mechanical properties, according to water absorption and temperature, of components fabricated by fused deposition modeling (FDM) and injection molding. The mechanical properties of FDM and injection molded parts were studied under several environmental conditions. Design/methodology/approach FDM components can be used as load-carrying elements under a range of moisture and temperature conditions. FDM parts show anisotropic mechanical properties according to build orientation. Components were fabricated from acrylonitrile-butadiene-styrene in three different orientations. The mechanical properties of parts fabricated by FDM were compared to injection molded components made from the same material. Water absorption tests were conducted in distilled water between 20 and 60°C to identify the maximum water absorption rate. Both moisture and temperature were considered as environmental variables in the tensile tests, which were conducted under various conditions to measure the effects on mechanical properties. Findings The water absorption behavior of FDM components obeyed Fickian diffusion theory, irrespective of the temperature. High temperatures accelerated the diffusion rate, although the maximum water absorption rate was not affected. The tensile strength of FDM parts under dry, room temperature conditions, was approximately 26-56 per cent that of injection molded parts, depending on build orientation. Increased temperature and water absorption had a more significant effect on FDM parts than injection molded components. The tensile strength was decreased by 67-71 per cent in hot, wet environments compared with dry, room temperature conditions. Originality/value The water absorption behavior of FDM components was investigated. The quantitative effects of temperature and moisture on tensile strength, modulus and strain were also measured. These results will contribute to the design of FDM parts for use under various environmental conditions.

Demographic and clinical differences between unilateral and bilateral forms of naevoid telangiectasia: a retrospective study with review of the literature

DEAR EDITOR, Unilateral naevoid telangiectasia (UNT) is characterized by telangiectasia distributed in a unilateral, dermatomal pattern, especially on the upper trunk and extremities. Even though the diagnosis is ‘unilateral’ naevoid telangiectasia, cases with bilateral distribution (bilateral naevoid telangiectasia, BNT) have been reported. However, no comparison has previously been made between the unilateral and bilateral forms of naevoid telangiectasia. Herein, we analyse the differences between the two groups and suggest different pathogeneses for each. Cases of ‘unilateral’ naevoid telangiectasia diagnosed clinically between January 2004 and August 2014 at Seoul National University Hospital and Seoul National University Boramae Hospital were divided into two groups, unilateral (Fig. 1a, b) and bilateral (Fig. 1c, d), based on actual clinical presentation. Biopsy specimens of five cases (four UNT, one BNT) were consistent with ‘unilateral’ naevoid telangiectasia. Twelve patients with UNT were compared with 12 patients with BNT. Between the two groups, we compared through chart review the age at visit, age of onset, underlying diseases and laboratory findings, including complete blood count, electrolytes, liver panel, serum glucose and hepatitis serology. Additionally, we combined our series with 44 previously reported cases (File S1; see Supporting Information) (31 UNT and 13 BNT) and performed analyses in the same manner. Analyses with Student’s t-test, Fisher’s exact test and the v-test were conducted using SPSS software, version 19 (IBM, Armonk, NY, U.S.A.). Missing data were not counted, and all P-values < 0 05 were considered to be statistically significant. The patients in our series with BNT were older than those with UNT at the initial visit (P < 0 001), and the age of onset was also much higher in BNT (P < 0 001) (Table 1). A definite difference in sex preponderance was detected (P = 0 001) (Table 1). Furthermore, there were marked differences in the prevalence of laboratory abnormalities and underlying dis-

Adipochemokines induced by ultraviolet irradiation contribute to impaired fat metabolism in subcutaneous fat cells

Adipose tissue is now appreciated as the pivotal regulator of metabolic and endocrine functions. Subcutaneous (SC) fat, in contrast to visceral fat, may protect against metabolic syndrome and systemic inflammation. We demonstrated that chronic as well as acute ultraviolet (UV) irradiation to the skin induces loss of underlying SC fat. UV‐irradiated SC fat may produce chemokines or cytokines that modulate lipid homeostasis and secretion of adipokines.

A case of perforating dermatofibroma with floret-like giant cells

Dermatofibromas are slow‐growing solitary nodules, composed mostly of a dermal proliferation of spindle cells and epithelioid cells. Some dermatofibromas present with multinucleated giant cells, such as Touton, foreign body, and osteoclast‐like cells. We report a case of dermatofibroma containing both Touton giant cells and floret‐type cells. A 12‐year‐old boy presented with a 6‐mm, firm, nontender, dusky‐red to greyish dermal nodule on his left popliteal fossa. As suggested clinically by the central opening, perforation of the epidermis with partial extrusion of the dermal components, including macrophages and vertically oriented collagen bundles, via transepidermal elimination, were detected. In the upper dermis, collagen trapping and mostly epithelioid cells with many giant cells were seen, while the lower part contained mainly spindle cells in a storiform pattern. Multinucleated giant cells scattered in the upper dermis were mainly floret‐type multinucleated giant cells with star‐shaped cytoplasmic projections, associated with some Touton giant cells. To our knowledge, this is the first report of a perforating dermatofibroma with floret‐type multinucleated giant cells.