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PubMed1995

Color stability of hybrid ionomers after accelerated aging.

PURPOSE: The color stability and surface roughness of three commercial hybrid ionomers were determined in vitro after accelerated aging. Three shades of each hybrid ionomer prepared in light-cured and dark-cured conditions were tested. MATERIALS AND METHODS: Samples were aged in an artificial aging chamber by subjecting them to total ultraviolet light irradiation of 150 kJ/m2 over a period of 77 hours. Color (CIE LAB system) was measured before and after aging on a reflection spectrophotometer. Surface roughness was measured with a profilometer. RESULTS: After accelerated aging, all samples became lighter. Photac-Fil Aplicap (ESPE-Premier, Norristown, PA) and Fuji II LC (GC America, Chicago, IL) also became less chromatic (less red and less yellow). Among the light-cured samples, Fuji II LC had the greatest change in color followed by Photac-Fil Aplicap and Vitremer (3M Dental Products, St Paul, MN). For the dark-cured samples, Fuji II LC had the greatest change in color followed by Vitremer and Photac-Fil Aplicap. There were no differences in delta E* between the two lightest shades, but the darker shades of each product showed the greatest changes in color. All samples became significantly rougher after aging. CONCLUSIONS: Hybrid ionomers changed color significantly and perceptibly after in vitro accelerated aging. Surfaces became significantly rougher and showed evidence of cracking and degradation.

Analysis of Variance↗

PubMed1997

Accelerated aging affects color stability of provisional restorative materials.

PURPOSE: The color stability of two shades each of five acrylic resin and seven resin composite provisional restorative materials was evaluated by reflection spectrophotometry following in vitro accelerated aging. MATERIALS AND METHODS: Specimens of provisional restorative materials were polymerized according to manufacturers' instructions and aged in an artificial aging chamber with exposure to a total ultraviolet irradiation of 60 kJ/m2. Color was measured by CIE L*a*b* on a reflection spectrophotometer before and after aging. Color change (delta E*) was calculated and analyzed statistically. RESULTS: Statistically significant changes in color were observed after accelerated aging. Nine of the 12 provisional materials tested showed perceptible color change of at least one of the shades tested. The most color-stable materials were the acrylic, Alike, and the resin composites, Luxatemp and Protemp Garant, which had no perceptible color changes under these conditions. CONCLUSIONS: Some acrylic resin and composite provisional materials change color significantly and perceptibly when exposed to in vitro accelerated aging conditions.

Acrylic Resins↗

PubMed2004

Distributed intraclot thrombolysis: mechanism of accelerated thrombolysis with encapsulated plasminogen activators.

BACKGROUND: The delivery of encapsulated plasminogen activators has demonstrated enhanced thrombolysis in vivo in several models. The mechanism of such improvement has not previously been established. OBJECTIVES: We explored in vitro the mechanism by which microencapsulation of streptokinase in polymeric microparticles accelerates clot digestion and reduces reperfusion times by as much as an order of magnitude in vivo. METHODS: The efficacy of microencapsulated streptokinase (MESK) was directly compared with identical dosages of unencapsulated streptokinase (FREE SK) at three initial pressure drops using clots formed of plasma or whole blood in 0.2-cm inner diameter glass capillary tubes. RESULTS: MESK demonstrated accelerated flow restoration compared with FREE SK for each condition in plasma (23.8 +/- 4.5% faster) and whole blood clots (17.2 +/- 9.2% faster). Images collected by light microscopy show sites of thrombolysis internal to the clot only with MESK while the spatial distribution of fluorescently labeled streptokinase by confocal microscopy confirms greater penetration of the encapsulated agent compared with unencapsulated streptokinase. Digestion thus proceeds in three dimensions rather than restricted to a two-dimensional lysis front. CONCLUSIONS: The improved clot penetration with MESK establishes enhanced transport with encapsulation and the concept of distributed intraclot thrombolysis as a basis for the accelerated dissolution observed with encapsulated plasminogen activators in vivo.

Drug Compounding↗

PubMedDate not supplied

Use of accelerating clinical improvement in reorganization of care: the Dartmouth-Hitchcock Medical Center experience.

Accelerating clinical improvement is a unique strategic method for accelerating the rate and effectiveness of improvements in strategically important clinical services. It promotes real reduction in the cost of service while preserving the quality and value within the system. Based on the components of process, value, benchmarking, change, and learning, the method can be used in any system or setting to produce value-driven change. Accelerating clinical improvement is being used within the Obstetrical Department of Dartmouth-Hitchcock Medical Center to decrease postpartum length of stay for families with spontaneous vaginal delivery. Familiarity with the method led to additional and ongoing improvements in the system. This method is important for nurses because it is continuous, multidisciplinary, addresses values of concern to families and providers, and is easily incorporated by nurse providers in any clinical setting.

Academic Medical Centers↗

PubMed2003

Emergency department presentations of naltrexone-accelerated detoxification.

OBJECTIVES: To analyze emergency department (ED) presentations after naltrexone-accelerated detoxification. METHODS: This was a retrospective cohort analysis of patient presentations to Sir Charles Gairdner Hospital Emergency Department over a six-month period (November 2000 to April 2001). RESULTS: During the six-month study period, 42 patients presented to the ED after naltrexone-accelerated detoxification. This represented 7% of patients treated at a single clinic over the same period. Presentation occurred within 24 hours in 40% of cases and within 48 hours in 74%. Clinical features on presentation included gastrointestinal (GI) symptoms (vomiting, 60%; abdominal pain, 55%; diarrhea, 45%), central nervous system [CNS] symptoms (excessive drowsiness, 55%; agitation requiring sedation, 50%), and respiratory symptoms (tachypnea, 33%; respiratory difficulties, 19%). Gastrointestinal symptoms were managed adequately with supportive therapy in most cases (intravenous fluids; antiemetics). Agitation sometimes required large doses of intravenous benzodiazepines (up to 730 mg in 44 hours), one-to-one nursing, and security staff. Two of 14 patients presenting with predominantly CNS disturbance required intubation (14%). Mean in-hospital stay for all patients was 18 hours (range 1 to 92 hours). CONCLUSIONS: A few patients undergoing outpatient naltrexone-accelerated detoxification during a six-month period subsequently required ED management. The clinical features encountered in this group of patients can be subdivided into GI or CNS predominance, with different management strategies. Most presentations can be managed in the ED or an associated observation ward, but departmental resources must be available for one-to-one nursing and security personnel. Patients presenting with agitation should be sedated with benzodiazepines; large doses may be required. Close monitoring of respiratory function is mandatory, and advanced airway management may be required.

Adolescent↗

PubMed2004

Accelerated regional bowel transit and overweight shown in idiopathic bile acid malabsorption.

OBJECTIVE: Overweight has recently been shown to accelerate small bowel transit. The role of gut transit and body weight in idiopathic bile acid malabsorption (IBAM) is unclear. We have prospectively studied gastrointestinal transit and body mass index (BMI) in patients with IBAM. METHODS: One hundred and ten patients with chronic diarrhea were prospectively included for transit measurements. All patients underwent a gastroscopy and colonoscopy, 75SeHCAT test for detection of bile acid malabsorption and calculation of BMI. Forty-three patients (15 men) had IBAM. A newly developed radiological procedure was used to measure gastrointestinal transit during one visit. The results were compared to results obtained in 83 healthy subjects. RESULTS: Colonic transit in women with IBAM was 0.8 (0.3-1.5) days versus 1.5 (1.0-3.7) days in healthy women (median and percentile 10 and 90; p < 0.0001). In men with IBAM it was 0.8 (0.1-1.0) days; in healthy men it was 1.3 (0.8-1.9) days, p < 0.0001. Segmental colonic transit was accelerated only in the distal colon in men and women with IBAM compared with healthy subjects. Small bowel transit time in women with IBAM was 1.9 (1.1-3.0) h versus 3.3 (1.5-6.3) h in healthy women, p= 0.0002. In men with IBAM it was 2.1 (1.2-3.2) h and 2.5 (1.4-4.3) h in healthy men (p= 0.04). BMI in patients with IBAM was 27.3 (20.4-33.8) kg/m2 and in healthy subjects it was 23.8 (20.5-26.2) kg/m2, p < 0.0001. CONCLUSION: Accelerated small bowel and distal colonic transit as well as overweight are probably involved in the pathophysiology of IBAM.

Adult↗

PubMed1996

Age-related changes of the cementogenesis in the senescence-accelerated mouse (SAM).

Cementogenesis of the molars with aging was studied using senescence accelerated mouse (SAM) which included SAMP2/Iw and SAMP8@Iw as prone strains, and SAMR1/Iw as a resistant strain. Morphometric analysis was done for the cementum thickness at 2, 6, 12 and 16 months of age on 4 parts of the mice, i.e. at the mesial (M), the distal (D), the apical (A) and the furcational (F) cementum of the maxillary first molar. SAMR1/Iw was also studied at 20 months of age. Mean cementum thickness was statistically analyzed for age and strain differences. Mean thicknesses of the M and the D cementum in SAMP2/Iw and in SAMP8@Iw were usually higher than those in SAMR1/Iw. Furthermore, there were significant differences between SAMP2/Iw and SAMR1/Iw, and between SAMP8/Iw and SAMR1/Iw, both at 12 and 16 months of age. There was no difference in mean thickness in the F cementum in either strain and at any age. In the A cementum, SAMP2/Iw displayed significantly thicker cementum than SAMR1/Iw at 6, 12 and 16 months of age. The degree of molar eruption was thought to be more accelerated in SAMP2/Iw than in SAMR1/Iw. However, the thickness of the A cementum was not different for SAMP8@Iw and SAMR1/Iw in any age group. In this study, 2 conclusions were drawn as follows: first, that SAMP2/Iw and SAMP8@Iw exhibited more accelerated cementogenesis than SAMR1/Iw in the M and the D cementum. Secondly, several factors such as intrinsic factors, occlusal forces and degree of attrition affected the cementogenesis of the M and the D, the F and the A cementum, respectively.

Aging↗

PubMed2004

Accelerated alveolar bone loss in mice lacking interleukin-10: late onset.

OBJECTIVE AND BACKGROUND: Interleukin-10 (IL-10) is an anti-inflammatory cytokine regulating immune responses. We have previously reported that IL-10(-/-) mice experience accelerated alveolar bone loss. The purpose of the present study was to examine the timing of the manifestation of accelerated alveolar bone loss in IL-10(-/-) mice. MATERIALS AND METHODS: Twenty-four IL-10(-/-) and 21 IL-10(+/+) age-matched male 129/SvEv mice were used. Sacrifice times occurred at 1, 3 and 9.5 months of age. Alveolar bone loss was determined morphometrically on defleshed jaws. Enzyme-linked immunosorbent assay (ELISA) was used for determination of serum concentration of type I collagen C-telopeptide, a systemic marker of bone resorption. RESULTS: Alveolar bone loss for the entire IL-10(-/-) group was significantly different than for the IL-10(+/+) group (p = 0.025). There was no significant difference in alveolar bone loss between IL-10(-/-) and IL-10(+/+) mice at 1 and 3 months of age. At 9.5 months of age, IL-10(-/-) mice exhibited 39% greater alveolar bone loss than IL-10(+/+) mice (p = 0.018). For IL-10(-/-) mice, alveolar bone loss significantly increased with age. Serum C-telopeptide levels significantly decreased with age in both groups. IL-10(-/-) mice had consistently higher C-telopeptide levels than IL-10(+/+) mice and the difference between the two groups reached statistical significance (p = 0.011) for the 9.5-month-old mice. CONCLUSIONS: These results suggest that the accelerated alveolar bone loss observed in IL-10(-/-) mice is a late-onset condition and that lack of IL-10 may have an effect on bone homeostasis.

Age Factors↗

PubMed2004

Accelerated aging effects on color and translucency of bleaching-shade composites.

PURPOSE: This study was performed to evaluate the influence of accelerated aging on the color and translucency parameter (TP) of bleaching-shade resin composites. MATERIALS AND METHODS: Thirty-three bleaching shades and two control conventional shades of microhybrid (MH) and microfill (MF) resin composite specimens (n = 5) were aged in an accelerated aging chamber set to standard CAM 180 cycles. One side of each specimen was evaluated for surface color and TP changes compared with baseline in increments of 150 kJ/m2 for intervals up to 450 kJ/m2 using a spectrophotometer. A deltaE* > or = 3.7 was considered to be a poor match, and the total TP range was divided into three equal parts representing low, medium, and high translucency. Data were analyzed with analysis of variance. RESULTS: Compared to the baseline, deltaL*, deltaa*, deltab*, and deltaE* ranges at 450 kJ/m2 were -0.8 to 5.0, -0.6 to 1.2, -8.3 to 0.0, and 0.7 to 8.6 for MH and 0.2 to 1.3, 0.1 to 1.3, -2.5 to 1.1, and 1.7 to 2.7 for MF composites. Scheffé's S intervals (p = .05) for comparisons of deltaL*, deltaa*, deltab*, and deltaE* values of MH composites between baseline and 450 kJ/m2 were 1.6, 0.6, 1.7, and 1.5, respectively. Corresponding Tukey-Kramer intervals for MF composites were 0.7, 0.3, 0.6, and 0.6, respectively. TP values at baseline ranged from 0.9 to 4.3 for MH and from 1.4 to 2.2 for MF composites, whereas deltaTP for baseline minus 450 kJ/m2 ranged from -1.1 to 1.7 for MH and from -0.1 to 0.3 for MF composites. Scheffé's S interval (p = .05) for comparisons of deltaTP values of MH composites for baseline minus 450 kJ/m2 was 1.0. Corresponding Tukey-Kramer interval for MF composites was 0.4. CONCLUSIONS: Aging-dependent color changes at 450 kJ/m2 were above the limit that indicated a poor match for 18/26 MH, while corresponding values for microfills were within acceptable range. Accelerated aging generally caused decreases in L* (specimens became darker) and a* values (specimens became redder), while b* values increased (specimens became more chromatic) for both MH and MF composites. TP was relatively stable during aging for both MH and MF composites.

Color↗

PubMedDate not supplied

In vivo delivery of heat shock protein 70 accelerates wound healing by up-regulating macrophage-mediated phagocytosis.

Injury causes tissue breakdown, which releases large quantities of intracellular contents into the extracellular space. Some of these materials are well-established activators of the immune system and include heat shock proteins (HSPs), uric acid, nucleotides, High Mobility Group Box-1 protein (HMGB-1), and DNA. Here, we show that in vivo delivery of HSPs into BALB/cJ mice with full-thickness wounds accelerates the rate of wound closure by 60% as compared with control-treated mice. The onset is rapid and the effect is sustained, dose dependent, and protein specific. Adoptive transfer of RAW264 macrophages pretreated with HSP70 into naïve recipients with a wound transfers the HSP-mediated effect on the rate of wound closure. Further, we demonstrate that part of the mechanism by which HSP70 accelerates wound closure is through the stimulation of macrophage-mediated phagocytosis of wound debris. Disabling the HSP70-mediated enhancement of phagocytosis abrogates the HSP-mediated acceleration of the healing process. These findings create two opportunities: one, therapeutic, wherein HSP70 could be used in the clinical management of wounds; and two, pathophysiologic, to decode signals by which the host defenses recognize and respond to injury.

Animals↗

PubMed2001

Vestibular discrimination of gravity and translational acceleration.

According to Einstein's equivalence principle, linear accelerations experienced during translational motion are physically indistinguishable from changes in orientation relative to gravity experienced during tilting movements. Nevertheless, despite these ambiguous sensory cues provided by the primary otolith afferents, perceptual and motor responses discriminate between gravity and translational acceleration. There is growing evidence to suggest that the brain resolves this ambiguity primarily by combining signals from multiple sensors, the semicircular canals being a main extra otolith contributor. Here, we summarize the experimental evidence in support of the canal influences on the neural processing of otolith cues, provide specific experimental results in rhesus monkeys, and discuss and compare previously proposed models that combine otolith and semicircular-canal signals in order to provide neural estimates of gravity and linear acceleration.

Animals↗

PubMed2001

Orientation of the eyes to gravitoinertial acceleration.

Orientation of the eyes to gravitoinertial acceleration, i.e., to the sum of gravity and the linear accelerations acting on the head and body, is a basic property of the linear vestibulo-ocular reflex to support vision. Present in a wide range of species from the lateral-eyed rabbit to frontal-eyed monkeys and humans, the eyes deviate in pitch, roll and yaw in response to pitch, roll and yaw head movements. The eyes also converge in response to naso-occipital linear acceleration. This paper provides examples of ocular orientation generated by static tilt and off-vertical axis rotation in three dimensions and demonstrates specifically how vergence would support vision in the rabbit.

Animals↗

PubMed1986

Acceleration of large intestine transit time in rats by sennosides and related compounds.

Sennosides A + B and their natural metabolites, sennidins A + B, rheinanthrone and rhein, as well as the synthetic laxative danthron, were investigated for their influence on small and large intestine transit time in rats. Carmine red, as a marker, was administered through a gastric tube for small intestine transit or intracaecally by a chronically implanted catheter for colon transit. High doses of sennosides (250-500 mg kg-1) given orally from 20 min or up to 6 h before marker administration had no effect on small intestine transit time. The metabolites and danthron (10-100 mg kg-1 p.o.) also did not accelerate upper gastrointestinal passage. Intracaecal administration at the same time as carmine red, however, reduced the time for the appearance of the first coloured faeces from more than 8 h in the controls to 46 +/- 9 min after sennosides, 34 +/- 11 min after sennidins, 53 +/- 83 min after rhein and 16 +/- 4 min after rheinanthrone (50 mg kg-1 of each). Danthron was ineffective. Thus, sennosides and their natural metabolites specifically influence large intestinal motility. Acceleration of colonic transport seems to be a major component of the laxative action whereas for danthron motility changes are not responsible for its laxative action. Indomethacin partly inhibited the acceleration of large intestine transit induced by sennosides. An involvement of endogenous prostaglandins may therefore be possible, although a local bolus administration of PGF2 alpha or PGE2 into the caecal lumen neither influenced transit time nor induced diarrhoea.

Animals↗

PubMed1972

The initiation of platelet thrombi in normal venules and its acceleration by histamine.

1. In cheek pouch preparations of anaesthetized hamsters, platelet thrombi or ;white bodies' were produced in venules by the micro-ionto-phoretic application of adenosine diphosphate (ADP). Currents of 10-400nA were passed through micropipettes containing 10 mM-ADP, the tips of which were less than 5 mu from the outer wall of the venule. The effect was quantitated by determining the time between starting the currents and the first appearance of platelets adhering inside the venule opposite the tip of the micropipette.2. Repeated applications of ADP to the same site on a venule caused the appearance of white bodies after intervals which were almost constant for up to 3 hr.3. The time to first appearance of a white body was inversely related to the iontophoretic current between about 10 and 200 nA. Currents smaller than 10 nA had no effect on the platelets. With currents of 200 nA or more the time remained at a minimum of less than 20 sec.4. With currents of about 300 nA the minimum time increased little as the pipette tip was withdrawn up to 20 mu from the venule; with greater distances the time increased progressively.5. Histamine caused gaps to appear between endothelial cells in cheek pouch venules. Histamine at a concentration of 10 mM in micropipettes was applied iontophoretically by currents of 300 nA to venules at the same sites as ADP. Histamine alone had no effect on circulating platelets. When applied before and together with ADP, histamine decreased the time to first appearance of white bodies by up to 40% below that determined with ADP alone. Iontophoretically applied histamine did not alter the mean blood flow velocity in the venules.6. After stopping the application of histamine, the time to first appearance of white bodies produced by ADP increased again in about 5 min to the control values.7. Bradykinin, which does not cause endothelial gaps in cheek pouch venules, did not accelerate the induction of white bodies like histamine.8. There were no microscopic abnormalities in venules in which white bodies had formed. Venules exposed to histamine accumulated circulating carbon particles in discrete wall areas.9. It is concluded that adhering white bodies can be induced repeatedly in normal venules by direct action of externally applied ADP on circulating platelets and that the accelerating effect of histamine on white body formation is due to the separation of endothelial cells which accelerates the inward diffusion of ADP.

Adenine Nucleotides↗

PubMed2001

In-phantom dosimetry for the 13C(d,n)14N reaction as a source for accelerator-based BNCT.

The use of the 13C(d,n) 14N reaction at Ed=1.5 MeV for accelerator-based boron neutron capture therapy (AB-BNCT) is investigated. Among the deuteron-induced reactions at low incident energy, the 3C(d,n)14N reaction turns out to be one of the best for AB-BNCT because of beneficial materials properties inherent to carbon and its relatively large neutron production cross section. The deuteron beam was produced by a tandem accelerator at MIT's Laboratory for Accelerator Beam Applications (LABA) and the neutron beam shaping assembly included a heavy water moderator and a lead reflector. The resulting neutron spectrum was dosimetrically evaluated at different depths inside a water-filled brain phantom using the dual ionization chamber technique for fast neutrons and photons and bare and cadmium-covered gold foils for the thermal neutron flux. The RBE doses in tumor and healthy tissue were calculated from experimental data assuming a tumor 10B concentration of 40 ppm and a healthy tissue 10B concentration of 11.4 ppm (corresponding to a reported ratio of 3.5:1). All results were simulated using the code MCNP, a general Monte Carlo radiation transport code capable of simulating electron, photon, and neutron transport. Experimental and simulated results are presented at 1, 2, 3, 4, 6, 8, and 10 cm depths along the brain phantom centerline. An advantage depth of 5.6 cm was obtained for a treatment time of 56 min assuming a 4 mA deuteron current and a maximum healthy tissue dose of 12.5 RBE Gy.

Boron↗

PubMed2002

Particle in cell simulation of laser-accelerated proton beams for radiation therapy.

In this article we present the results of particle in cell (PIC) simulations of laser plasma interaction for proton acceleration for radiation therapy treatments. We show that under optimal interaction conditions protons can be accelerated up to relativistic energies of 300 MeV by a petawatt laser field. The proton acceleration is due to the dragging Coulomb force arising from charge separation induced by the ponderomotive pressure (light pressure) of high-intensity laser. The proton energy and phase space distribution functions obtained from the PIC simulations are used in the calculations of dose distributions using the GEANT Monte Carlo simulation code. Because of the broad energy and angular spectra of the protons, a compact particle selection and beam collimation system will be needed to generate small beams of polyenergetic protons for intensity modulated proton therapy.

Computer Simulation↗

PubMed2002

Peripheral dose distributions for a linear accelerator equipped with a secondary multileaf collimator and universal wedge.

The American Association of Physicists in Medicine Task Group 36 (AAPM TG-36) data can be used to estimate peripheral dose (PD) distributions outside the primary radiation field. However, the report data does not apply to linear accelerators equipped with a multileaf collimator (MLC) and universal wedge (UW). Tertiary multileaf collimators have been shown to significantly affect PD distributions and TG-36 reported data. Measurements were performed to evaluate PD distributions for a linear accelerator equipped with a secondary MLC, backup diaphragms, and UW. This data can be used to compliment the TG-36 report for estimation of doses to critical structures outside primary radiation fields. For the evaluated linear accelerator, an MLC is incorporated in the upper secondary collimator jaws. Backup shielding diaphragms are located underneath the MLC. At the nominal collimator position, the MLC and the backup diaphragm provide collimation primarily in the transverse direction. Conventional, solid tungsten-alloy jaws, located underneath the backup diaphragms, provide secondary collimation in the longitudinal direction. The universal wedge provides dose modulation in the direction of the conventional jaws. Measurements were made with an ionization chamber inserted into a 20x40x120 cm(3) water-equivalent plastic phantom with the secondary collimator and MLC settings of 5x5, 10x10, 15x15, and 25x25 cm(2) with and without UW. Data was acquired along the machine's longitudinal axis for 6, 10, and 18 MV photons. Peripheral dose distributions were measured with the collimator rotated to 0 degrees and 270 degrees for open field measurements and to 0 degrees, 180 degrees, and 270 degrees for wedged fields (IEC 1217). This allowed evaluation of peripheral dose distributions as a function of collimator rotation. Wedged fields were normalized to deliver the same dose at the depth of maximum dose on the central axis as open fields. The measured PD distributions were generally comparable to data reported by TG-36. At distances close to the field edge (less than 30 or 40 cm), the measured PD distributions were lower when the measurement point was shielded by solid jaws than with MLC and backup diaphragm. At longer distances, this trend reversed for all energies and evaluated field sizes. However, the difference in PD distribution with collimator rotation was not large enough to warrant strategic positioning of the collimator to reduce dose to critical structures outside the primary radiation field. Because internal scatter dominates close to the field edge, wedged PD distributions were comparable to open field doses at distances closer than 30 cm. However, at distances larger than 30 cm from the field edge, wedged PD distributions were significantly grater than those for open fields due to increased contribution of leakage radiation. Increased leakage radiation is due to the increase in wedged field monitor units, which is related to a small wedge factor (0.27 to 0.29).

Humans↗

PubMed2002

Surface melt-induced acceleration of Greenland ice-sheet flow.

Ice flow at a location in the equilibrium zone of the west-central Greenland Ice Sheet accelerates above the midwinter average rate during periods of summer melting. The near coincidence of the ice acceleration with the duration of surface melting, followed by deceleration after the melting ceases, indicates that glacial sliding is enhanced by rapid migration of surface meltwater to the ice-bedrock interface. Interannual variations in the ice acceleration are correlated with variations in the intensity of the surface melting, with larger increases accompanying higher amounts of summer melting. The indicated coupling between surface melting and ice-sheet flow provides a mechanism for rapid, large-scale, dynamic responses of ice sheets to climate warming.

Journal Article↗