Effects Of Thermal Stimuli Research Articles

Thermal stimuli response diphenylmethane diisocyanate‐based polyurethane elastomer via adjustable silicon‐induced distinctive microstructure

AbstractThe segment character of polyurethanes (PUs) determines the micromorphology and properties. The effective segment regulation can customize the favorable performance of PUs. Herein, silicon covalent‐modified polyurethanes (MPUs) were prepared by incorporating diphenylmethane diisocyanate (MDI) and diphenyl silanediol (DPSD) into PU molecules as hard segments via a two‐step method. Distinctive microphase separation structures from sheet morphology to radial sheet or withered flower‐like microdomain were formed by adjusting hydrogen bonding of hard segments and post‐treatment techniques. Thus, with the addition of DPSD in hard segments, the thermo‐optic responses for MPUs occurred due to the different microphase evolution under thermal effect. And with the further addition of DPSD, the effect of thermal stimuli on the transmittance gradually weakened. It was very clear that with increasing the temperature, the transmittance of MPUs showed a gradual increase owing to melting the microcrystals or destroying the ordered accumulation of hard segments. Meanwhile, the high mechanical properties were obtained, higher 15 times tensile strength and more than 100 times elastic modulus than those of pure PU as well as the excellent thermal stability. In sum, this study was of great significance for developing new functionalized PU materials.Highlights Polyurethanes were prepared by inducing modified silicon functionality. The distinctive microphase separation evolution of MPUs was found. Thermal stimuli responses showed a gradual decrease due to different structure. High mechanical properties and thermal stability were also obtained.

Effect of Thermal Stimulus on Kinetic Rehydration of Thermoresponsive Poly(diethylene glycol monomethyl ether methacrylate)-block-poly(poly(ethylene glycol) methyl ether methacrylate) Thin Films Probed by In Situ Neutron Reflectivity.

The kinetic rehydration of thin di-block copolymer poly(diethylene glycol monomethyl ether methacrylate)-block-poly(poly(ethylene glycol) methyl ether methacrylate) (PO2-b-PO300) films containing two thermoresponsive components is probed by in situ neutron reflectivity (NR) with different thermal stimuli in the D2O vapor atmosphere. The transition temperatures (TTs) of PO2 and PO300 blocks are 25 and 60 °C, respectively. After the one-step stimulus (rapid decrease in temperature from 60 to 20 °C), the film directly switches from a collapsed to a fully swollen state. The rehydration process is divided into four steps: (a) D2O condensation, (b) D2O absorption, (c) D2O evaporation, and (d) film reswelling. However, the film presents a different rehydration behavior when the thermal stimulus is separated into two smaller steps (first decrease from 60 to 40 °C and then to 20 °C). The film first switches from a collapsed to a semiswollen state caused by the rehydrated PO300 blocks after the first step of thermal stimulus (60 to 40 °C) and then to a swollen state induced by the rehydrated PO2 blocks after the second step (40 to 20 °C). Thus, the kinetic responses are distinct from that after the one-step thermal stimulus. Both the time and extent of condensation as well as evaporation processes are significantly reduced in these two smaller steps. However, the final states of the rehydrated PO2-b-PO300 films are basically identical irrespective of the applied thermal stimulus. Thus, the final state of thermoresponsive di-block copolymer films is not affected by the external thermal stimuli, which is beneficial for the design and preparation of sensors or switches based on thermoresponsive polymer films.

A study on the differences of effect on mast cells and serum 5-HT in the acupoint area of “CV 4” of rats by acupuncture stimulus and thermal stimulus

ObjectiveTo observe the influence of acupuncture stimulus and thermal stimulus on the expression of mast cells (MCs) and 5-hydroxytryptamine (5-HT) in local acupoint area of Guānyuan (关元 CV 4) and serum 5-HT in rats. MethodsThirty-nine male C57BL/6 rats were randomly divided into blank control group, acupuncture stimulus group and thermal stimulus group, with 13 rats in each group. The rats were stimulated by manual acupuncture at CV 4 for 5 min in acupuncture stimulus group, while those in thermal stimulus group were stimulated by adopting a thermal moxibustion apparatus on CV 4 for 30 min. The expression of MC and 5-HT in the skin in the acupoint area of CV 4 before and after acupuncture stimulus and thermal stimulus was observed and analyzed via adopting toluidine blue staining method and immunofluorescence histochemical method (5 rats were selected from each group), and the 5-HT content in serum before and after stimulus was determined through enzyme-linked immunosorbent assay (ELISA) (8 rats were selected from each group). The influence of acupuncture stimulus and thermal stimulus on the contents of MC and 5-HT in the skin and serum 5-HT in rats was analyzed and compared. Results① After acupuncture stimulus or thermal stimulus on CV 4 of C57BL/6 rats, the number of MC in the acupoint area significantly increased when compared with that in blank group (the acupuncture stimulus group 12.40 ± 2.07 vs. the blank group 3.00 ± 5.96; thermal stimulus group 26.20 ± 10.85 vs. the blank group 12.40 ± 2.07, both P < 0.05), and MC aggregation and degranulation were observed (the acupuncture stimulus group 17.80 ± 4.55 vs. the blank group 8.00 ± 3.16; the thermal stimulus group 24.00 ± 9.05 vs. the blank group 8.00 ± 3.16, P < 0.05, P < 0.01). ② After acupuncture stimulus or thermal stimulus, 5-HT was released by MCs in the acupoint area, which aggregated around the blood vessels, and the number of 5-HT in the acupoint area significantly increased when compared with that in blank group (the blank group 3.00 ± 1.28 vs. the acupuncture stimulus group 10.02 ± 3.21; the blank group 3.00 ± 1.28 vs. the thermal stimulus group 14.00 ± 3.94, both P < 0.01). ③ Compared with blank group, both acupuncture stimulus and thermal stimulus could reduce the 5-HT content in serum (the blank group 0.72 ± 0.2372 vs. acupuncture stimulus group 0.43 ± 0.21; the blank group 0.72 ± 0.24 vs. thermal stimulus group 0.32 ± 0.18, both P < 0.01), and the effect in thermal stimulus group was slightly superior to that in acupuncture stimulus group (P < 0.05). ConclusionBoth acupuncture stimulus and thermal stimulus can cause the aggregation and degranulation of MCs and high expression of 5-HT in the acupoint area. The effect of thermal stimulus was superior to that of acupuncture stimulus in degranulation.

The effects of thermal stimuli on intracellular calcium change and histamine releases in rat basophilic leukemia mast cells

The effects of thermal stimuli on rat basophilic leukemia mast cells were studied. The cells in calcium-contained or calcium-free buffers were thermally stimulated in the temperature range of 25–60 °C. The corresponding calcium ion concentration in cells [Ca2+]i as well as the released histamine from cells was measured with fluorescence staining methods. The ruthenium red (RR), a block of membrane calcium channels (transient receptor potential family V (TRPV)), was used in experiments. Under the stimulus of 25–50 °C, no significant difference on [Ca2+]i was found between these three groups of the cells in calcium-contained buffer without or with RR and cells in calcium-free saline, indicating that the increased calcium in cytosol did not result from the extracellular buffer but came from the intracellular calcium stores. The [Ca2+]i continuously increased under the temperature of 50–60 °C, but the RR and calcium-free saline can obviously diminish the [Ca2+]i increase at these high temperatures, reflecting that the opening of the TRPV2 channels leads to a calcium influx resulting in the [Ca2+]i increment. The histamine release also became significant in these cases. Since the released histamine is a well-known mediator for the microcirculation promotion, the histamine release from mast cells could be one of the mechanisms of thermal therapy.

Effect of thermal stimuli on peripheral blood flow in homozygous sickle cell disease: A preliminary study

Forearm blood flow (FBF) was measured in 23 patients with homozygous sickle cell (SS) disease and 20 controls with normal hemoglobin genotype (AA) using venous occlusion air plethysmography to examine the pattern of peripheral blood flow in both groups at rest, and in response to thermal stimuli. The mean resting FBF in SS patients was more than twice that in AA controls (P<0.001). Indirect cooling (15°C) of the left forearm for 2 minutes evoked a significant increase (P<0.005) in FBF in the opposite arm in both SS patients and AA controls, with the response being greater in the controls. Indirect heating (40°C) for 2 minutes evoked a decrease in FBF of a similar magnitude in both groups. The increased FBF in response to moderate cooling in SS patients may be part of an important reflex mechanism which could support the concept of the ‘steal’ syndrome, as recently postulated, as a possible explanation for the cold-related initiation of the painful crisis of SS disease.

Direct Influence of Temperature on the Semicircular Canal Receptor

Effect of thermal stimulus on the vestibular receptor was studied using the isolated frog semicircular canal. The posterior (PSC) and lateral semicircular canals (LSC) were placed in the horizontal plane in frog Ringer's solution. The ampullary nerve was sucked into a glass suction electrode to record compound potentials. The steel thermal probe was positioned next to the ampullary surface to give thermal stimuli. When the PSC ampulla was cooled, the spontaneous discharge markedly increased. When the PSC ampulla was warmed, the discharge decreased. When the LSC ampulla was cooled, the discharge increased in the same manner as in the PSC. Also, warming of the LSC decreased the discharge in the same manner as in the PSC. The cupula was removed from the crista in order to eliminate the effect of volume change of the endolymph. The results were comparable to those with intact cupula in both the PSC and LSC. Cooling increased, while warming decreased the discharge. These responses are possibly due to a mechanism other than mechanical volume change, because the PSC and LSC yielded the same type of responses. Direct temperature reaction of the vestibular hair cell was suggested.

Effect of thermal stimuli on peripheral blood flow in homozygous sickle cell disease: A preliminary study

Effect of thermal stimuli on peripheral blood flow in homozygous sickle cell disease: A preliminary study

Effects of Thermal Stimuli by Total Body Water Immersion and Balneotherapy on Endocrine and Autonomic Nervous Functions

Effects of Thermal Stimuli by Total Body Water Immersion and Balneotherapy on Endocrine and Autonomic Nervous Functions