Standard Comb Research Articles

Comb Drive Designs With Minimized Levitation

This paper presents two capacitive comb drive designs for electrostatic actuation of MEMS with the aim to eliminate the levitation effect often observed in such systems. By placing a shield over the comb drive fingers, it is possible to balance the electric field and suppress vertical forces while maintaining the desired lateral motion. By optimizing the comb geometry, we demonstrate that our approach is able to reduce the levitation by an order of magnitude and unwanted coupling of motion from out-of-plane to in-plane by a factor of 7 compared with standard comb architectures fabricated using PolyMUMPs technology, without the need of alternating comb finger polarities or additional control electrodes. Levitation was reduced to 160 nm, for 3.6- $\mu \text{m}$ lateral displacement at a driving voltage of 80 $V$ . [2016-0156]

Impact of young (Y) age on efficacy and safety in advanced colorectal cancer (aCRC): A pooled analysis examining 6,286 patients (pts) from nine first-line phase III chemotherapy (CT) trials.

3520 Background: CRC is primarily a disease of the elderly; however, the SEER database shows ∼10% of pts are age ≤50. Previous data suggested Y pts have worse outcomes. We sought to determine whether Y age is prognostic or influences efficacy or toxicity for aCRC pts treated with CT. Methods: We analyzed individual pt data on 6,286 subjects from 9 randomized phase III aCRC trials of 5FU-based single- agent and combination (comb) CT. Endpoints included progression-free survival (PFS), overall survival (OS), tumor response (RR), and grade ≥3 adverse events. Cox models stratified by study, and logistic-regression models adjusting for study, were used to test for age (<40 vs. ≥40; <50 vs. ≥50) effects and age-treatment interactions. Efficacy endpoints were explored in the full set of 9 trials and the subset of 5 studies comparing mono- to comb CT. Results: 793/6,286 (13%) were age <50, of which 188 pts (3% total) were <40. Comparing pts <50 to those ≥50: grade ≥3 nausea (N) (10% vs. 7%, p=0.01) was more common. However, rates of severe diarrhea (D) (11% vs. 14%, p=0.001) and neutropenia (NP) (23% vs. 26%, p<0.0001) were significantly lower in Y pts. Age was prognostic for PFS, with poorer outcomes in those <50 (median 6.0 vs. 7.5 months, HR=0.91, p=0.02), but it did not affect RR or OS. In the subset of mono- vs. comb CT trials, the relative PFS, OS, and ORR benefits of multi-agent CT were similar for Y and older pts (see Table). Results were comparable with the age 40 cutpoint. Conclusions: Based on a comparison with SEER, Y aCRC pts are proportionally represented on phase III studies. Y age is modestly associated with poorer PFS but not OS or RR in treated aCRC pts, and Y pts have more N but less D and NP with CT in general. Y vs. older pts derive the same benefits from comb CT. Based on these data, in the absence of a clinical trial, standard comb CT approaches are appropriate for Y aCRC pts. Age <50 Age ≥50 p value** Mono Comb HR/OR* Mono Comb HR/OR* Median PFS (months) 4.7 7.2 0.64 6.3 8.4 0.74 0.11 Median OS (months) 13.6 16.3 0.82 14.8 16.6 0.89 0.57 RR (%) 28 54 3.29 29 51 2.63 0.43 * HR of PFS/OS, OR for RR. ** p value testing for age by CT interaction. Author Disclosure Employment or Leadership Position Consultant or Advisory Role Stock Ownership Honoraria Research Funding Expert Testimony Other Remuneration Amgen, AstraZeneca, Bristol-Myers Squibb, Genentech, ImClone Systems, Novartis, Pfizer, Roche, sanofi-aventis Roche, sanofi-aventis Amgen, Genentech

Characterization of the Conduction Mechanisms in Adsorbed Electrolyte Layers on Electronic Boards Using AC Impedance

The reliability impact of flux residues on electronic assemblies has been traditionally evaluated using surface insulation resistance (SIR) measurement with dc voltages. An ac impedance technique has been investigated to provide detailed information on the conduction mechanisms and electrode reactions in the presence of flux residues on electronic boards. By evaluating different fluxes using a standard comb pattern the relative applicability of the ac impedance and SIR techniques has been made in terms of assessing the reliability of electronic boards. Impedance values at low frequencies, , are close to the SIR results and hence produce similar predictions of reliability. More importantly, the ac impedance spectrum can be used to predict dendrite formation, although the technique itself does not actually promote dendrites. The ac impedance method can distinguish between ionic solution resistance of the thin water layer and impedance from interfacial electrochemical processes. At low contamination levels the solution resistance, between the copper-comb electrodes, dominates the overall impedance. At high contamination levels the impedance from interfacial electrochemical processes becomes significant and increases the potential of dendrite formation. This predictive capability could be developed into a nondestructive test method to provide a more detailed electrochemical characterization and indication of future reliability.

Results of 60-second timed hair counts in women between the ages of 20–60 years

The accurate documentation of hair loss is important when monitoring disease progression and treatment efficacy. In clinical trials of minoxidil topical solution, hair count data obtained via macrophotography and image analysis from a 1-cm2 target area of the scalp provides an accurate, objective, and reproducible means of measuring hair loss and regrowth. However, this method requires technical expertise and specialized photographic equipment and is not practical for clinicians or for patients to use at home. We conducted a study of an adaptation of the 60-second timed hair count performed by Kligman in 1961. We enrolled a larger sample size of 40 healthy women between the ages of 20 and 60 years, 20 women between 20–40 years and 20 women between 41–60 years. Female volunteers were instructed to shampoo their hair on each of 3 consecutive days. Using a standard comb, they combed their hair forward for 60 seconds each day allowing the shed hairs to fall onto a towel or pillowcase. They recorded the number of shed hairs in a diary and completed a questionnaire. Baseline 60-second hair counts were reported in an earlier poster. The same protocol was repeated 6 months later in order to account for seasonal effects on hair shedding, and the results are reported in this follow-up study. 38 women completed the study. Overall, patients shed an average of 10 to 19 hairs per 60-second interval (range, 1–115). At baseline, patients between the ages of 20–40 years shed an average of 11.6 hairs (SD 8.7), whereas patients between the ages of 41–60 years shed an average of 18.4 hairs (SD 16.9). The difference between these two groups was however not significant at the 5% significance level based on the student’s t-test. Hair counts by the patients and investigators were compatible. At follow-up 6 months later, patients between the ages of 20–40 years shed an average of 9.5 hairs (SD 6.2), whereas patients between the ages of 41-60 years shed an average of 18.5 hairs (SD 16.0). The difference between these two age groups was significant at the 5% significance level based on the student’s t-test. No noticeable seasonal effect on hair shedding was observed. Although there was increased inter-patient variability in hair counts, intra-patient variability was small (ie, individual hair counts were consistent over each of the 3 days.) This is the first study demonstrating the utility of a reproducible, practical, in-home method that will be of use in documenting hair shedding and response to treatment.

Birth weight responses to shearing ewes in early to mid gestation

AbstractThis study compared the effect on foetal growth of shearing ewes in very early pregnancy (day 50) with the effect of shearing later in pregnancy (day 70 or 100). One hundred and sixty ewes were allocated at day 49 of pregnancy to four ‘time of shearing’ treatments — pregnancy day 50 (P50), P70, P100 (no. = 45 ewes per treatment) and unshorn (shearing of this group occurred 43 days after weaning) (no. = 25); two methods of shearing (by standard comb and cover comb); and two levels (1 or 2) of pregnancy/rearing rank. All ewes had been mated over a 28-day period and grazed pasture throughout the trial. The mid point of lambing was 27 August 1996. Live weights of ewes (corrected for fleece weight) were not influenced by shearing time at any stage except at day 45 of lactation when ewes shorn at P50, P70 or P100 were about 3⋅0 kg lighter than unshorn ewes. Shearing method had no effect on ewe live weight. Time of shearing and shearing method had no effect on ewe greasy fleece production or wool tensile strength. Shearing significantly (P &lt; 0⋅05) influenced the birth weight of single- (by 0⋅7 to 0⋅8 kg) but not twin-born lambs. Maternal plasma triiodothyronine concentration increased proportionately by 0⋅47 to 0⋅85 (P &lt; 0⋅05) and lasted for at least 20 days in response to shearing irrespective of time of shearing. No difference in plasma insulin concentration was detected between shearing groups but plasma glucose concentration proportionately increased by 0⋅06 to 0⋅16 (P &lt; 0⋅05) for 10 to 20 days after shearing. These results indicate that shearing between day 50 and 100 of pregnancy can increase lamb birth weights and that the response is associated with an increase in thyroid hormone concentrations in the maternal circulation.

Optimal shape design of three-dimensional MEMS with applications to electrostatic comb drives

A comb drive is one of the most important microactuators in Microelectromechanical (MEM) systems. In a standard comb drive, the capacitance varies linearly with displacement, resulting in an electrostatic driving force which is independent of the position of the moving fingers (relative to the fixed ones) except at the ends of the range of travel. It is of interest in some applications to have force profiles such as linear, quadratic or cubic. Such shaped comb drives could be useful, for example, for electrostatic tuning or to get actuators with longer ranges of travel than those of standard comb drives. This paper presents a methodology for solving three-dimensional design (inverse) problems in MEM systems. Design of variable shape comb drives (shape motors) is presented as an application of the general methodology. It addresses issues of simulation, sensitivity analysis and then design of three-dimensional comb drives. Direct simulation is carried out by the exterior, indirect boundary element method and shape sensitivities are obtained by the direct differentiation approach. The inverse problem determines the height profile of the moving fingers of a comb drive such that the driving force is a desired function of its travel distance. An available optimization code (‘E04UCF’ from the NAG package) is used to solve the inverse problem. Numerical results are presented for shape motors that produce linear or cubic force profiles as functions of travel of the moving fingers. Copyright © 1999 John Wiley & Sons, Ltd.

Improved Operation of Micromechanical Comb-Drive Actuators through the Use of a New Angled Comb Finger Design

An original design for a new comb finger structure to be used in electrostatically driven actuator devices is presented and experimentally demonstrated. The new design is seen as one viable alternative to the already prevalent rectangular comb finger design and can be considered as a crossbreed between a conventional comb finger design (0 = 0 a parallel-plate design (0 = 900). The design topology is verified both analytically, to show the validity of fundamental effects, and experimentally. Experimental results show the fabricated device based on the new comb finger design achieves twice the displacement of a standard rectangular comb finger based device under equal operating conditions, hence demonstrating twice the force generation capability, while at the same time maintaining overall device stability.

Pasture management to minimise the detrimental effects of pre‐lamb shearing

The purpose of this study was to examine whether the performance of pre‐lamb shorn sheep is influenced by pasture allowance in the immediate post‐shearing period and whether the relationship between performance and pasture allowance differs according to whether the ewes are shorn by standard comb or cover comb. The trial was replicated across two years to allow for climatic variations between years. Fifty‐four ewes were used in each year in a 3 × 3 × 2 factorial design with three shearing treatments (standard comb, cover comb, and unshorn), three sward surface height (SSH) treatments (nominal 3, 5, and 7 cm), and two pregnancy status treatments (single and twin). Rectal temperatures of standard comb or cover comb ewes were significantly lower (P < 0.05) than those of unshorn ewes on day 2 following shearing (S2), and on S4, S8, and S20. Pasture allowance, however, did not affect rectal temperatures of shorn ewes. There was an interaction (P < 0.05) between shearing treatment and SSH. Thus, liveweight gains during the period from pregnancy day 115 (P115) to P135 were 275, 613, and 4518 g; 1557, 2314, and 3997 g; and 3623, 2894, and 3997 g for standard comb, cover comb, and unshorn (control) ewes set‐stocked on 3, 5, and 7 cm SSH, respectively. There was no interaction between shearing treatment and SSH for lamb birth weight, but the birth weights of lambs born to standard comb ewes (4.9 ± 0.1 kg) were significantly greater (P < 0.05) than those of lambs born to unshorn ewes (4.3 ±0.1 kg). There were no effects of shearing treatment or SSH on lamb weaning weight, ewe wool growth rate or mean fibre diameter. Likewise, there were no effects of shearing treatment or SSH on ewe organic matter intake (OMI), except on the second day following shearing when the OMIs of ewes set‐stocked on 3 cm (941 ± 147 g) were significantly (P < 0.05) lower than those of ewes grazing 5 cm (1628 ±101 g) or 7 cm (1349 ± 135 g) SSH pasture. The results suggest that hypothermia, as determined by rectal temperatures and induced by pre‐lamb shearing, cannot be avoided by pasture management, provided SSH exceeds 3 cm. This reflects the fact that, in the period immediately after shearing, ewes do not increase feed intake when provided with increased pasture allowances.

Selective enhancement of growth in twin foetuses by shearing ewes in early gestation

AbstractShearing ewes during pregnancy frequently increases the birth weight of lambs. In housed ewes, the birth weight responses are greatest when shearing occurs relatively early in pregnancy. This study examined the effects of the timing and method of shearing on foetal growth, as measured by birth weight, in ewes at pasture. Border Leicester × Romney ewes were allocated at day 50 of pregnancy to: four ‘time of shearing’ treatments — pregnancy day 70 (P70), P100, P130 (no. = 60 for each treatment) and unshorn (no. = 34); two methods of shearing (by standard comb or cover comb); and two levels of pregnancy/rearing rank All ewes had been mated over a 14-day period and grazed pasture together throughout the trial The mid-point of lambing was 17 August.At no time during pregnancy or lactation did ewe live weight differences between the groups exceed 4 kg. Ewes shorn by cover comb were heavier prior to lambing and during lactation than standard comb-shorn ewes. Time of shearing, method of shearing and ewe rearing rank had no effect on ewe annual greasy fleece production. There was a highly significant (P &lt; 0·001) interaction between the effects of birth rank and time of shearing on lamb birth weight. Time of shearing did not affect birth weight of single-born lambs but birth weight of twin lambs increased with earlier maternal shearing to a maximum of 0·7 kg (per lamb) in those born to ewes shorn on P70. These results imply that shearing reduced the greater extent of maternal constraint which applies to the growth of twin v. single foetuses in utero. This selective increase in birth weights of twins achieved by early pregnancy shearing may have advantages in reducing lamb mortality.

Resistance to cold stress in sheep shorn by cover comb or standard comb

AbstractThe cover comb has been developed in New Zealand as a means of increasing residual fleece depth after shearing and so increasing the resistance of shorn sheep to cold stress.The effects of shearing by cover comb and standard comb were studied over 2 days pre-shearing and 10 days post-shearing in eight pairs of non-pregnant, non-lactating 2-year-old ewes. Animals were housed and given a maintenance level of chaffed lucerne hay. One member of each pair was shorn with a cover comb, the other with a standard comb. Each pair was exposed to ‘cold plus wind’ (7°C ambient temperature, 7 km/h air movement) followed by ‘cold plus wind plus rain’ (10°C ambient temperature, 7km/h air movement, wetting at a rate equivalent to 25 mm/h rain from overhead sprinklers) in a calorimetry chamber on days S –3, S –2, SO (day of shearing), S2, S6 and S10. Heat production immediately after shearing (SO) was proportionately 0·22 greater in ewes shorn by the standard comb under conditions of ‘cold plus wind’ and 0·38 greater under conditions of ‘cold plus wind plus rain’ than in their cover comb-shorn cohorts. Circulating concentrations of non-esterifiedfatty acids were substantially elevated on the day of shearing and 2 days thereafter in ewes shorn by the standard comb, indicating increased rates of body fat mobilization to support heat production in these ewes compared with those shorn by the cover comb. This was reflected in a 1·4 kg weight loss in the standard comb-shorn ewes compared with a 0·4 kg live-weight gain in the cover comb-shorn group over the 10 days of the experiment. It was concluded that use of a cover comb will significantly reduce the risk of death from hypothermia in sheep shorn during winter and spring, and should facilitate an increase in the productivity of animals by allowing a greater proportion of food energy to be used for productive purposes.

Productivity and cold resistance in ewes pre-lamb shorn by standard or cover comb

The cover comb has been developed in New Zealand as a means of increasing residual fleece depth after shearing and so increasing the resistance of shorn sheep to cold-stress. The effects of pre-lamb shearing ewes with cover or standard comb, and of leaving ewes unshorn until after weaning, on their feed intake, productivity, and cold resistance were studied. Border Leicester x Romney ewes were divided into three groups balanced for pregnancy status, ewe age and liveweight. Two groups of ewes were shorn, by either cover comb or standard comb, on day 114 of pregnancy (P114) and one group left unshorn until weaning on day 84 of lactation (L84). Ewes were managed under the same conditions during pregnancy and lactation. Ewes shorn pre-lamb by cover comb had lower mortality from shearing to lambing, and lower organic matter intakes and biting rates at P123-126 than ewes shorn by standard comb. These parameters did not differ between ewes shorn pre-lamb by cover comb and unshorn ewes except biting rate which was greater in the cover comb-shorn group. Twenty days after shearing (P134), the liveweights of ewes were greater in the unshorn group than in the cover comb-shorn group (P &lt; 0.05), which was in turn heavier (P &lt; 0.05) than ewes shorn by standard comb. Midside clean wool growth rates were greater in standard comb- and cover comb-shorn ewes during the post-shearing period (to day 40 of lactation) than in unshorn ewes ( P &lt; 0.05). Similarly, the yield and brightness of wool were superior (P &lt; 0.05) in pre-lamb shorn groups. Lamb liveweights at birth, docking and weaning, and lamb survival, were similar between shearing policies. Rectal temperature (RT) was significantly (P &lt; 0.05) lower in both pre-lamb shorn groups than in the unshorn group on day 3 post-shearing (S3), but by S5 only the ewes shorn by standard comb had lower RT. These results suggest that the greater amount of residual wool in cover comb- vs standard comb-shorn ewes provides a low cost practical method for reducing the two important disadvantages of pre-lamb shearing, namely increased cold-stress and feed intakes post-shearing.