Temperature-controlled molecular dynamics study on velocity-dependent threshold behavior of dynamic nano-friction

Laws of dynamic nano-friction (i.e., continuous wearless friction) were searched for under steady spatial distributions of the local quasi-temperature, by molecular dynamics (MD) simulations. The temperature control of the non-conservative model was carried out by extending the isothermal MD method using the Nosé–Poincaré thermostat. The results suggested that the threshold phenomenon characterizes sliding-velocity dependence of the nano-frictional force between crystal lattices constituting a nano-electromechanical system (NEMS). This phenomenon was turned out to be a universal feature, whether heat transfer to the environment exists or not.     

Myelin phagocytosis by macrophages and nonmacrophages during Wallerian degeneration

The literature concerning Schwann cells (SCs) and macrophages in myelin phagocytosis during Wallerian degeneration is reviewed. SCs carry out the first step in the removal of myelin by segmenting myelin and then incorporating the degraded myelin. The recruited macrophages then join in the myelin-phagocytosis event, appearing to make full use of their original phagocyte abilities until the end of myelin clearance. The molecular mechanisms of the two cells underlying myelin phagocytosis are thought to be different; myelin phagocytosis by SCs being lectin-mediated, i.e., opsonin-independent, whereas that of macrophages is mainly opsonin-dependent. It is important to note that SCs and macrophages cooperatively accomplish myelin phagocytosis.     

A dispatching method for automated guided vehicles by using a bidding concept

A dispatching method is suggested for automated guided vehicles by using an auction algorithm. The dispatching method in this study is different from traditional dispatching rules in that it looks into the future for an efficient assignment of delivery tasks to vehicles and also in that multiple tasks are matched with multiple vehicles. The dispatching method in this study is distributed in the sense that the dispatching decisions are made through communication among related vehicles and machines. The theoretical rationale behind the distributed dispatching method is also discussed. Through a simulation study, the performance of the method is compared with that of a popular dispatching rule. RID="*" ID="*" The research was financially supported by the Sasakawa Scientific Research Grant from The Japan Science Society. The original version of the simulation program is provided by Professor Jae Yeon Kim at Dong Yang University, Korea. Correspondence to: J. K. Lim     

Three-dimensional simultaneous measurements of micro-fluorescent-particle position and temperature field via digital hologram

This paper reports on a new technology of simultaneous measurements of micro-fluorescent-particle position in 3D and of temperature field with high time-resolution. The technology to measure both velocity and temperature field is based on the simultaneity of micro digital holographic particle tracking velocimetry (micro-DHPTV) and laser-induced fluorescence (LIF).     

Formation of bromo-substituted triclosan during chlorination by chlorine in the presence of trace levels of bromide

The side reactions of triclosan (2,4,4'-trichloro-2'-hydroxydiphenyl ether, TC) and chlorine in the presence of sodium chloride were investigated. In the absence of sodium chloride, three chloro-derivatives of TC, 2',3,4,4'-tetrachloro-2-hydroxydiphenyl ether (3-Cl-TC), 2',4,4',5-tetrachloro-2-hydroxydiphenyl ether (5-Cl-TC), and 2',3,4,4',5-pentachloro-2-hydroxydiphenyl ether (3,5-Cl(2)-TC) were formed, whereas in the presence of sodium chloride, 3-bromo-2',4,4'-trichloro-2-hydroxydiphenyl ether (3-Br-TC), 5-bromo-2',4,4'-trichloro-2-hydroxydiphenyl ether (5-Br-TC), (3 or 5)-bromo-2',4,4',(5 or 3)-chloro-2-hydroxydiphenyl ether ((3,5)-(BrCl)-TC), and 3,5-dibromo-2',4,4'-trichloro-2-hydroxydiphenyl ether (3,5-Br(2)-TC) were additionally formed. Radiochemical neutron activation analysis indicated that 1g of commercially available sodium chloride contained 73 microg of bromide and the bromide ion was determined to be the source of the side reactions. The rate of decrease of TC due to reaction with chlorine was greatly accelerated by the presence of bromide ion in the system: the rate with only 1 x 10(-5) M bromide ion was three times the rate in the absence of bromide.     

Curing behavior and properties of epoxy resins cured with the diamine having the quinoxaline or triazine structure

2,3-Bis(4-aminophenyl)quinoxaline (1a), 2,3-bis(4-aminophenyl)-6-methylquinoxaline (1b), and 5,6-bis(4-aminophenyl)-3-(2-pyridyl)-1,2,4-triazine (2) were studied as curing agents of epoxy resins. The exotherms on differential scanning calorimetry thermograms of the mixtures of diglycidyl ether of bisphenol A (DGEBA) with 1a, 1b, and 2 were observed at higher temperatures than that of the mixture of DGEBA with a commercially used diamine, for example, 4,4′-diaminodiphenylsulfone (DDS). However, the epoxy resin cured with 1a (EP-1a) showed higher tensile strength to stainless steel at 20°C than that cured with DDS, and the high tensile strength of EP-1a was maintained even at 180°C. The epoxy resin cured with 1b or 2 also possessed higher tensile strength at 20°C than that cured with DDS, but the high tensile strength lowered somewhat at 120°C. Using diamines 1a, 1b, and 2 as a curing agent improved heat distortion temperatures of the cured epoxy resins. © 1998 John Wiley & Sons, Inc. J. Appl. Polym. Sci. 69: 1737–1741, 1998     

A construction algorithm for designing guide paths of automated guided vehicle systems

A construction algorithm is suggested to design guide path networks for automated guided vehicle systems (AGVSs). This study uses the total travel time, including waiting and interference time, of vehicles as the decision criteria for determining the direction of path segments on unidirectional guide path layouts. The Q-learning technique is applied to estimate the travel times of vehicles on path segments. Computational experiments were performed to evaluate the performance of the proposed algorithm. The simulation results showed that the proposed algorithm is superior to Kim & Tanchoco's (1993) algorithm in terms of the average travel time, the interference time and the number of deliveries.     

Special purpose computer system with highly parallel pipelines for flow visualization using holography technology

We have designed a PC cluster system with special purpose computer boards for visualization of fluid flow using digital holographic particle tracking velocimetry (DHPTV). In this board, there is a Field Programmable Gate Array (FPGA) chip in which is installed a pipeline for calculating the intensity of an object from a hologram by fast Fourier transform (FFT). This cluster system can create 1024 reconstructed images from a 1024×1024-grid hologram in 0.77 s. It is expected that this system will contribute to the analysis of fluid flow using DHPTV.     

Thymidylate synthase expression in patients with hypopharyngeal carcinoma

We analyzed the relationship between clinical response to neo-adjuvant chemotherapy including 5-fluorouracil (5-FU) in patients with hypopharyngeal carcinoma (HPC) and thymidylate synthase (TS) expression in their tumors. TS expression was evaluated with immunohistochemical staining techniques on biopsy specimens from HPC patients. TS immunostaining was divided into four levels (TS0-TS3) according to its level and pattern. The relationship between prognosis, tumor size, nodal status, differentiation of tumor cells and TS expression were also investigated. There was a statistically significant association between the level of TS expression and tumor size (p < 0.01). In terms of the effectiveness of chemotherapy, tumor differentiation, nodal status and prognosis, a statistical difference was not found in TS expression. These results suggest that the level of TS expression may show the degree of tumor proliferation, but may not necessarily be useful to obtain a response to chemotherapy including other drugs, e.g., cisplatin and other derivatives of platinum.