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result(s) for
"Dykstra, Dennis"
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Mixed effectiveness of rTMS and retraining in the treatment of focal hand dystonia
by
Schmidt, Rebekah L. S.
,
Kimberley, Teresa J.
,
Buetefisch, Cathrin M.
in
Botulinum toxin
,
Brain research
,
Cortex (premotor)
2015
Though the pathophysiology of dystonia remains uncertain, two primary factors implicated in the development of dystonic symptoms are excessive cortical excitability and impaired sensorimotor processing. The aim of this study was to determine the functional efficacy of an intervention combining repetitive transcranial magnetic stimulation (rTMS) and sensorimotor retraining. A randomized, single-subject, multiple baseline design with crossover was used to examine participants with focal hand dystonia (FHD) (n = 9).
5 days rTMS + sensorimotor retraining (SMR) vs. Five days rTMS + control therapy (CTL) (which included stretching and massage). The rTMS was applied to the premotor cortex at 1 Hz at 80% resting motor threshold for 1200 pulses. For sensorimotor retraining, a subset of the Learning-based Sensorimotor Training program was followed. Each session in both groups consisted of rTMS followed immediately by 30 min of the therapy intervention (SMR or CTL). Contrary to our hypothesis, group analyses revealed no additional benefit from the SMR training vs. CTL. When analyzed across group however, there was significant improvement from the first baseline assessment in several measures, including tests of sensory ability and self-rated changes. The patient rated improvements were accompanied by a moderate effect size suggesting clinical meaningfulness. These results provide encouragement for further investigation of rTMS in FHD with a need to optimize a secondary intervention and determine likely responders vs. non-responders.
Journal Article
Linking acoustic velocity of standing Douglas-fir trees to veneer stiffness: a tree-log-product study across thinning treatments
by
Briggs, David G
,
Lowell, Eini C
,
Dykstra, Dennis P
in
Acoustic properties
,
Biomedical and Life Sciences
,
Density
2014
Background
To understand the effects of silvicultural treatments on tree and product modulus of elasticity (MOE), an intensive study along the stand-tree-product value chain was conducted. Acoustic tests were performed on 460 Douglas-fir (
Pseudotsuga menziesii
(Mirb.) Franco) trees from two sites in the US Pacific Northwest.
Methods
Trees on a site in Washington were 51 years old, while those situated in Oregon were 45 years old. Both sites comprised five plots: Plot A was the control, while Plots B, C, D, and E were prescribed with differing thinning treatments. Acoustic readings were stratified, and a sample of six trees per plot randomly selected from the stratified samples. Trees were harvested, cross-cut, and peeled into veneer. Veneer was acoustically tested, and density and MOE calculated for each sheet. Veneer sheets were grouped by parent bolt and tree, and MOE of the butt veneer bolt and the parent tree determined from the mean. Plot means were compared using one-way analysis of variance (ANOVA), and regression models developed with mean tree MOE as the response variable and non-destructive tree measures as explanatory variables. Further models were developed to demonstrate the relationship between tree diameter and the number of veneer sheets peeled, and between MOE of the parent tree and butt bolt.
Results
MOE was negatively correlated with diameter and taper, and positively correlated with acoustic velocity, V. The relationship with V
2
, following the wave equation (MOE = ρV
2
) under the assumption of constant density, ρ, was no better than that with V. While the correlations suggest that thinning regimes that cause rapid diameter growth and increased taper may be susceptible to a reduction in overall stiffness, there was no evidence, as determined by ANOVA, to suggest that thinning reduces stiffness. On the contrary, mean MOE at plot E (light thinning) was 12.6 GPa and the control was 10.2 GPa, with the difference significant at the 10% level (p-value = 0.074).
Conclusions
In general, trees with MOE exceeding the recommended tree breeding value of 11 GPa were of low taper and small diameter, suggesting that regimes with a lesser impact on taper and diameter, as demonstrated by Plot E, are worthy of further investigation.
Journal Article
Evaluating Effects of Thinning on Wood Quality in Southeast Alaska
2012
We examined the effect of thinning on wood quality of western hemlock (Tsuga heterophylla) and Sitka spruce (Picea sitchensis) located on Prince of Wales and Mitkof Islands in southeast Alaska. Sample trees came from paired plots (thinned versus unthinned) in eight naturally regenerated, mixed stands of young-growth western hemlock and Sitka spruce in an effort to examine a range of thinning densities, from 10 × 10 ft to 20 × 20 ft spacing. The stands, which had been thinned in the late 1970s and early 1980s, ranged in age from 36 to 73 years at the time they were selected for this study in 2003. The main focus of the stand selection in this retrospective study was to find individual stands that included a thinned plot and an adjacent unthinned plot from the same original stand. A random sample of trees from both thinned and unthinned plots was selected, stratified by tree dbh. About 12 trees per species per stand (461 trees in total) were selected for the study. Selected trees were harvested, and a lumber recovery study was conducted, enabling us to relate log volume to recovered lumber volume by product grade. Surfaced dry dimension lumber was produced, graded, and nondestructively tested using the transverse E-vibration standard test for stiffness. We did not evaluate the resource for appearance-grade products. For each species, the overall treatment effect (thinned versus unthinned) on lumber grade recovery and transverse E-vibration modulus of elasticity by vertical-log position (butt log, middle log, or top log) were analyzed using a mixed-effects procedure. Results suggest that there were no significant differences in product recovery or value between the thinned plots and the untreated control plots in the manufacture of structural lumber products.
Journal Article
Biomass Utilization for Bioenergy in the Western United States
by
Dykstra, D.P
,
Nicholls, D.L
,
Monserud, R.A
in
Alternative energy sources
,
Analysis
,
Applied sciences
2008
The increased risk of forest fires as a result of over-stocked stands has created strong incentives to use biomass material for energy or other purposes. Biomass may be used for energy at different scales, including large-scale electrical power generation at stand-alone facilities, cogeneration to produce process steam and electrical power, or smaller scale thermal heating projects at governmental, educational, or other institutions. However, barriers that tend to inhibit bioenergy applications in western states include accessibility, terrain, harvesting costs, and capital costs. The availability of government incentives has the potential to stimulate new technologies and new uses of biomass material when private investors may not be willing to provide investment capital. Although several classes of barriers to biopower development have been identified , all point to one central issue: rarely will the value of biomass products pay for the costs of harvesting, collecting, and transporting to markets in the western states.
Journal Article
Cost Analysis of Forest Biomass Supply Chain Logistics
by
Handler, Robert
,
Abbas, Dalia
,
Dykstra, Dennis
in
Clearcutting
,
Cost assessments
,
Forest biomass
2013
This study analyzes the cost of harvesting pulpwood from natural forests intended for the expansion of forest product opportunities in Michigan. Four sources of information were used to assess costs: (1) the USDA Forest Service Forest Inventory and Analysis database; (2) a Michigan-specific version of the USDA Forest Service Fuel Reduction Cost Simulator (FRCS); (3) primary logistics data collected from a questionnaire sent to logging firms in Michigan; and (4) primary transportation data collected from truck and rail firms. Three different harvest prescriptions were modeled: 30% selective cut, 70% shelterwood cut, and clearcut. The prescriptions were applied to fully stocked or overstocked stands analyzed from the Forest Inventory and Analysis database. Harvest systems analyzed were the following: mechanized whole-tree feller buncher with skidder and processor; mechanized cut-to-length equipment and forwarder; and chainsaws and skidder systems. Transportation analyses have been conducted for truck and bimodal (truck and rail) transportation options. Procedures and results describe the wide range of data required to analyze the cost of the logging supply chain, demonstrating the variability in the determination of a fixed cost for forest biomass removal operations.
Journal Article
Why poor logging practices persist in the tropics
by
Putz, Francis E.
,
Heinrich, Rudolf
,
Dykstra, Dennis P.
in
Animal, plant and microbial ecology
,
Applied ecology
,
Biological and medical sciences
2000
Despite abundant evidence that both the environmental damage and the financial costs of logging can be reduced substantially by training workers, pre-planning skid trails, practicing directional felling, and carrying out a variety of other well-known forestry practices, destructive logging is still common in the tropics. Based on our collective experience with loggers in tropical forests, we discuss seven possible reasons for this seemingly irrational behavior. The principal reason poor logging practices persist is apparently that the widely heralded cost savings associated with reduced-impact logging relative to unplanned logging by untrained crews may not be realized under some conditions. In particular, where compliance with logging guidelines restricts access to steep slopes or prohibits ground-based timber yarding on wet ground, reduced-impact logging may be synonymous with reduced-income logging. Given that under such conditions loggers may not adopt reduced-impact logging methods out of self-interest, fiscal mechanisms for promoting sustainable forest management may be needed.
Journal Article
Treatment of overactive bladder with botulinum toxin type B: a pilot study
by
Valley, Michael
,
Dykstra, Dennis
,
Enriquez, Al
in
Bladder
,
Drug therapy
,
Urinary incontinence
2003
The purpose of this study was to determine the efficacy and safety of botulinum toxin type B (BTX-B/Myobloc) in the treatment of patients with overactive bladder. This open-label dose-escalation study enrolled 15 female patients with urinary frequency with or without incontinence. The BTX-B doses used in this study were 2500, 3750, 5000, 10 000 and 15 000 units. Response was defined as a subjective improvement in frequency, urgency and incontinence symptoms. A paired t-test of the pre/post frequency difference indicates that these 15 patients experienced an average of 5.27 fewer frequency episodes per day after treatment with BTX-B. The p value for the paired t-test was <0.001. The longest duration effect was 3 months using 10 000-15 000 units of BTX-B. The correlation between dose and duration was very significant, with a correlation coefficient = 0.96, p<0.001. Based on these findings, we feel the use of botulinum toxin to treat patients with overactive bladder warrants further study.[PUBLICATION ABSTRACT]
Journal Article
Effects of Bear Damage on Douglas-Fir Lumber Recovery
2010
Bear activity resulting in injury to Douglas-fir (Pseudotsuga menziesii [Mirb.] Franco) trees has been documented as early as the mid-1850s in the Pacific Northwest. The study reported in this article was designed to help managers decide whether the common practice of removing the damaged but potentially valuable butt section of the bottom log and leaving it in the woods is warranted. Thirty-four damaged and 28 undamaged trees were selected from three sites in western Washington where bear damage has been a persistent problem. Trees were felled and bucked into 16-ft lengths. The damaged trees in the sample had been injured at ages between 10 and 15 years at two sites and between 10 and 65 years at the third site. The primary scaling deductions were for ring and scar defects. The 16-ft butt logs from the damaged and undamaged trees were sawn into dimension lumber. Bear-damaged logs were found to have lower cubic volume recovery than undamaged logs having the same small-end diameters. Lumber grade recovery was also influenced by bear damage; logs from damaged trees had a lower percentage of high-value lumber. The analysis suggests that the optimal harvesting policy is to haul the entire butt log to the mill rather than leaving the damaged portion in the woods. Although the value of the damaged portion is lower, most of the lumber recovered from that section can be used, with only a modest reduction in grade and value.
Journal Article
Effectiveness of rTMS and retraining in the treatment of focal hand dystonia
by
Dennis Dale Dykstra
,
Cathrin M Buetefisch
,
Teresa Jacobson Kimberley
in
human
,
Neuromodulation
,
Rehabilitation
2015
Though the pathophysiology of dystonia remains uncertain, two primary factors implicated in the development of dystonic symptoms are excessive cortical excitability and impaired sensorimotor processing. The aim of this study was to determine the functional efficacy of a sensorimotor intervention combining rTMS and sensorimotor retraining. A randomized, single-subject, multiple baseline design with crossover was used to examine participants with focal hand dystonia (FHD) (n=9). Intervention: 5 days rTMS + sensorimotor retraining (SMR) vs. 5 days rTMS + control therapy (CTL) (which included stretching and massage). The rTMS was applied to the premotor cortex at 1 Hz at 80% resting motor threshold for 1200 pulses. For sensorimotor retraining, a subset of the Learning-based Sensorimotor Training program was followed. Each session consisted of rTMS followed immediately by 30 minutes of the therapy intervention (SMR or CTL). Group analyses revealed no additional benefit from the SMR training vs CTL, which was contrary to our hypothesis. When analyzed across group however, there was significant improvement from first baseline in several measures, including tests of sensory ability and self-rated changes. The patient rated improvements were accompanied by a moderate effect size suggesting clinical meaningfulness. These results provide encouragement for further investigation of rTMS in FHD with a need to optimized a secondary intervention and determine likely responders vs. non-responders.
Journal Article