Stereotactic transcranial magnetic stimulation: correlation with direct electrical cortical stimulation

OBJECTIVE: To evaluate stereotactic transcranial magnetic stimulation (TMS) as a tool for presurgical functional mapping of human motor cortex. METHODS: Transcranial magnetic stimulation using a frameless stereotactic system was performed in two patients with tumors near the central sulcus. TMS motor function maps were plotted on the patients' three-dimensional volumetric magnetic resonance imaging data and compared with direct electrical cortical stimulation at surgery with the patient under local anesthesia. RESULTS: Stereotactic TMS was well tolerated by both patients and was consistent with known somatotopic representation of human motor cortex. The results demonstrated a good correlation between the TMS and electrical cortical stimulation maps, with all TMS responses eliciting more than 75% of the maximum motor evoked potential falling within 1 cm of the electrical cortical stimulation site. CONCLUSIONS: Our findings indicate that stereotactic TMS is feasible and can provide accurate noninvasive localization of cortical motor function. It may prove to be a useful method for presurgical planning.     

An approach to optimising compressed air systems in production operations

A low-cost, non-intrusive method of quantifying the energy consumed by compressed air systems (CASs) and lost through system leaks is described, with various means of minimising energy consumption presented. Case studies across different industrial facility types are examined where the approach used in quantifying energy losses due to system leaks has been implemented. Monitoring across 5 sites identified circa 500,000?kWh of waste energy due to leaks of which 30–60% can be saved. The approach has reduced waste electrical consumption by 60% on one site. Non-energy-related benefits arising from awareness of CAS losses are described. The proposed approach effectively illustrates the benefits of CAS energy analysis in a manner which can be quickly and easily implemented using off-the-shelf energy monitoring and data-logging equipment. The methodology can be regularly applied to provide continual monitoring and management of the optimal state of an industrial facilities CAS.     

The thermal decomposition of 1,3,5 trinitro hexahydro 1,3,5 triazine (RDX)—part I: The products and physical parameters

The thermal decomposition of RDX has been investigated in a static system below its melting point at 195°C. The initial decomposition of RDX takes place in the vapor phase. Hydroxymethyl formanide and polymeric materials formed from hydroxymethyl formamide have been shown to be major products. These comparatively low molecular weight materials are highly hydrogen bonded liquids of low volatility which subsequently act as a solvent for RDX. Nitrogen, due to its effect on the rate of diffusion of RDX vapro away from the crystal surface, is shown to have an inhibiting effect.     

Self-diffusion in solutions of carboxylated acrylic polymers as studied by Pulsed Field Gradient NMR. 2. Diffusion of macromolecules

The diffusion constants of carboxylated acrylic copolymers in isopropanol (IPA) have been investigated using the PFG NMR technique. A range of compositions of butyl methacrylate and methacrylic acid random copolymers (BMA–MAA 100/0 through to 60/40 in 10 mol% steps) have been studied. The polymer diffusivity is two orders of magnitude slower than that for the solvent. A maximum value of G _max = 10 T/m for the gradient pulse was used to suppress solvent signal and to measure the low value of the self-diffusion coefficient for the polymers. Polymer diffusion studies at different diffusion times showed that the diffusion constant decreased with increasing diffusion time. The influence of the concentration on the polymer aggregation in solution and the influence of the BMA/MAA molar ratio on the diffusion constants of the polymer have been studied. The diffusion constant for the polymer at long diffusion times increased with mol% BMA which is similar to the short diffusion time studies. The data obtained have been discussed using published results and models for “anomalous diffusion” of macromolecules in polymer solutions.     

高强钢纤维碳纳米管混凝土双轴受压试验与破坏准则

高强钢纤维碳纳米管混凝土(HSSFCNRC)是一种新型高强复合混凝土,具有流动性好、强度高、韧性大、耐久性好等显著优点。为探讨其多轴应力状态下的强度特征和变形特性,该文利用大连理工大学的大型静、动三轴电液伺服试验机,分别对普通高强混凝土(HSPC)和HSSFCNRC进行了不同应力比条件下的二轴受压对比试验,观察其破坏形态、得到了极限应力和峰值应变等其他参数。通过对Kupfer-Gerstle破坏准则、宋玉普模型和杨健辉模型进行的比较分析发现,HSPC和HSSFCNRC都适合这几种模型,但曲线包络线要优于折线包络线,且强度高的包络线包住强度低的,HSSFCNRC包络住HSPC。通过对八面体应力空间和应变空间的破坏准则分析发现,宋玉普模型的子午线为椭圆曲线,精确度较高;而文中采用的破坏准则子午线为直线,应用简便,也可满足工程应用要求。     

Perinatal and infant nutrition. Nucleotides

Nucleotides (NT) are ubiquitous intracellular compounds of crucial importance to cellular function and metabolism. Much recent interest has focused on NT as components of the non-protein nitrogen fraction of human milk. NT supplementation of infant formula has now been introduced in several countries. Biological effects of NT have been reported in several fields. Dietary NT have been shown to have important effects on several components of the immune system: they may enhance intestinal absorption of iron; they affect lipoprotein and long-chain polyunsaturated fatty acid metabolism; they may alter intestinal flora; and they have been demonstrated to have trophic effects on the intestinal mucosa and liver in several experimental situations. Clinical studies have shown NT supplementation of infant formula reduces the incidence of diarrheal episodes among socioeconomically deprived infants, and enhances catch-up growth in infants born small for gestational age. Further work will continue to try to identify other clinical situations in which NT may have a beneficial role.     

Hydrodynamic studies of an advanced fluidized-bed bioreactor for direct interaction with coal

Fine coal particles fluidized by the upflow of a liquid medium containing a dissolved biocatalyst undergo size reduction as the reaction progresses. Three aspects of the design of such a reactor were examined:

1. (1)the use of force balances to describe pressure drop for the segregated bed;

2. (2) measurement of liquid-phase dispersion coefficients; and

3. (3) fluorescent tagging of particles to track size distribution.

Hydrodynamic data were obtained for a liquid-solid fluidized bed of coal particles in the size range 30–150 μm. Illinois No. 6 coal was ball-milled, sieved into four fractions, and suspended in a 0.1% aqueous solution of Tween 80. A sample with a bimodal particle size distribution centred on 49 and 63 μm was placed in a glass column and fluidization and pressure-drop data were compared with a new model developed to describe particle segregation. Measured liquid-phase dispersion coefficients varied from 0.034 to 0.283 cm² s⁻¹ as the flow varied from 0.005 to 0.0159 cm s⁻¹. A technique was also developed for coating coal particles with a fluorescent paint which may allow direct measurement of the change in the fraction of marked particles of known size along the axis of a fluidized bed.     

Subcutaneous implants of polypropylene filaments

Extruded filaments of unmodified polypropylene (PP) with and without antioxidant were implanted subcutaneously in hamsters in order to determine their rate of degradation. Specimens were removed periodically during a 5 month test period and analyzed by infrared spectroscopy and dynamic mechanical testing. The analyses show that degradation beigns to occur after only a few days. Although the reaction sequence is not known, several factors suggest that the in vivo degradation process is similar to autoxidation which occurs in air or oxygen. The infrared data indicate that the hydroxyl content of the implants increases at a rate of 0.061 mg/g polypropylene per day during the initiation phase of the reaction. An induction time of 108 days was extablished. Carbonyl bonds appear after an implantation time of 50--90 days and increase therafter. Mechanical tests indicate a decrease in the dynamic loss tangent, tan delta, during the first month of implantation for unmodified polypropylene. No change in the infrared spectra or tan delta was observed, however, for implants containing an antioxidant. Thus, it is apparent that polypropylene filaments implanted subcutaneously in hamsters degrade by an oxidation process which is retarded effectively by using an antioxidant. While the findings reported are specific to subcutaneous polypropylene implants, they suggest that degradation of other systems may involve similar processes. This notion suggests directions for further research on increasing the in vivo stability of synthetic polymers. Long-term effects of polymer implantation upon tissue were not studied in this work.     

Diffusion and nuclear magnetic relaxation in concentrated polystyrene solutions

Nuclear magnetic relaxation times (T₁ and T₂) and diffusion coefficients (D) of polystyrene solutions in d₈ toluene have been measured as a function of molecular weight. The polymer T₁, T₂ and D values decrease monotonically with increasing molecular weight. T₁ and D reach limiting values at high molecular weights. The results are interpreted in terms of chain entanglements and the time scale of the experimental method.