An Electrostatic Lens for Focusing Charged Particles in a Mass Spectrometer

The ability to transmit particles into the ablation region of an aerosol mass spectrometer determines in part the lower size limit for particles that can be analyzed. A large fraction of small particles (< 100 nm) are lost due to processes such as Brownian diffusion that broaden the particle beam. In this work, electrostatic focusing is used to overcome the limits of aerodynamic focusing in the analysis of nanometer-sized particles by aerosol mass spectrometry. A simple tube lens is used to focus charged particles into the ablation laser beam path. The diameter of the focused beam is smaller than the fundamental aerodynamic limit imposed by Brownian motion. Measured enhancements of the hit rate for particles between 21 and 33 nm diameter are between 3 and 6. These values are lower limits for the true enhancements. The lens is also energy selective and can be used to select the mass (size) of the particles being analyzed.     

Nonsurgical treatment of platysmal bands with injection of botulinum toxin A

Botulinum toxin A has been used therapeutically in humans for over 20 years for a variety of medical indications. For the past 7 years, the author has injected it for cosmetic purposes in a variety of muscles of the head and neck. Fifty patient-injections of the platysma muscle were performed in an attempt to correct platysmal banding. An improvement was seen in all patients who presented to the office for follow-up in a timely manner (44 injections). Results were limited by redundant skin. No incidence of dysphagia or airway obstruction was encountered. The only complication noted was bruising. Although at least a small improvement in platysmal banding was seen in all patients, in no patient was there evidence of lifting of the lower face. All results were temporary.     

Analog and digital circuits using organic thin-film transistors onpolyester substrates

We have fabricated and characterized analog and digital circuits using organic thin-film transistors on polyester film substrates. These are the first reported dynamic results for organic circuits fabricated on polyester substrates. The high-performance pentacene transistors yield circuits with the highest reported clock frequencies for organic circuits     

槽式太阳能集热管热性能评估方法

真空集热管是槽式太阳能聚光集热系统的核心部件之一.集热管工作过程中通过辐射换热、对流换热和热传导的方式将热量传递给环境,这部分传递到环境中的热量称为集热管的热损失.真空集热管的热损失是聚光集热系统热损失或总能量损失的主要组成,在很大程度上决定着聚光集热器的光-热转换效率,因此对集热管热性能的正确评估对聚光集热系统的研究至关重要.本文对槽式太阳能集热管热性能的计算、评估分析方法等进行了分析.     

Evolution of road-surface skid-resistance and texture due to polishing

In this paper, works are conducted to have a better understanding of the evolution of the road-surface texture due to traffic polishing. Examples are shown for two aggregates having respectively low and high - polishing-resistances. Surface profiles measured at different polishing stages are analyzed. Roughness parameters characterizing asperity height and sharpness are calculated and their evolution is compared with the friction evolution.     

Crystal structures of a marginally active thymidylate synthase mutant, Arg 126-->Glu

Thymidylate synthase (TS) is a long-standing target for anticancer drugs and is of interest for its rich mechanistic features. The enzyme catalyzes the conversion of dUMP to dTMP using the co-enzyme methylenetetrahydrofolate, and is perhaps the best studied of enzymes that catalyze carbon-carbon bond formation. Arg 126 is found in all TSs but forms only 1 of 13 hydrogen bonds to dUMP during catalysis, and just one of seven to the phosphate group alone. Despite this, when Arg 126 of TS from Escherichia coli was changed to glutamate (R126E), the resulting protein had kcat reduced 2000-fold and Km reduced 600-fold. The crystal structure of R126E was determined under two conditions--in the absence of bound ligand (2.4 A resolution), and with dUMP and the antifolate CB3717 (2.2 A resolution). The first crystals, which did not contain dUMP despite its presence in the crystallization drop, displayed Glu 126 in a position to sterically and electrostatically interfere with binding of the dUMP phosphate. The second crystals contained both dUMP and CB3717 in the active site, but Glu 126 formed three hydrogen bonds to nearby residues (two through water) and was in a position that partially overlapped with the normal phosphate binding site, resulting in a approximately 1 A shift in the phosphate group. Interestingly, the protein displayed the typical ligand-induced conformational change, and the covalent bond to Cys 146 was present in one of the protein's two active sites.     

Colonic and anorectal function in constipated patients with anorexia nervosa

OBJECTIVES: Many patients with eating disorders complain of severe constipation. Previous studies have suggested that constipation in patients with anorexia nervosa may be associated with slow colonic transit. However, it is unclear whether a refeeding program will alter colonic transit in these patients. The aim of this study was to investigate colorectal function by measuring colonic transit and anorectal function in anorexic patients with constipation during treatment with a refeeding program. METHODS: We prospectively studied 13 female patients with anorexia nervosa who were admitted to an inpatient treatment unit and compared them to 20 previously studied, age-matched, healthy female control subjects. Patients underwent colonic transit studies using a radiopaque marker technique and anorectal manometry measuring anal sphincter function, rectal sensation, expulsion dynamics, and rectal compliance. Patients were studied both early (< 3 wk) and late (> 3 wk) in their admission. We restudied two patients who had slow colonic transit. All patients also underwent structured interviews. RESULTS: Four of six patients studied within the first 3 wk of their admission had slow colonic transit, defined as > 70 h (108.0 +/- 17.0 h, mean +/- SEM), on initial evaluation. In contrast, none of the seven patients studied later than 3 wk into their admission had slow colonic transit. Two of the four patients with slow transit were restudied later in their admission and were found to have normal transit times. Rectal sensation, internal anal sphincter relaxation threshold, rectal compliance, sphincter pressures, and expulsion pattern were normal in all subjects. CONCLUSIONS: Despite complaints of severe constipation, colonic transit is normal or returns to normal in the majority of patients with anorexia nervosa once they are consuming a balanced weight gain or weight maintenance diet for at least 3 wk.