|
|
|
BRL Abstracts Database |
|
Your search for ultrasound produced 3296 results. Page 232 out of 330
| Title |
Sonochemistry and sonocatalysis of metal carbonyls. |
| Author |
Suslick KS,Goodale JW, Schubert PF, Wang HH. |
| Journal |
J Am Chem Soc |
| Volume |
|
| Year |
1983 |
| Abstract |
Ultrasonic irradiation of liquids produces acoustic cavitation: the rapid formation, growth, and implosive collapse of vapor filled vacuoles. This generates short-lived “hot spots” with peak temperatures - 3000 K and nanosecond lifetimes.We have studied the effects of high intensity ultrasound on a variety of metal carbonyls and have observed the general phenomenon of sonochemical ligand dissociation, which often produces multiple CO substitution. Fe(CO)5, for example, upon sonolysis,yields Fe3(CO),, in the absence of additional ligands and Fe(CO),L2 and Fe(CO),L (L = phosphine or phosphite) in their presence. Similar substitution patterns are observed for Fe,(CO),,, Mn,(CO)lo, Cr(CO),, Mo(CO),, and W(CO),. In all cases examined the rates of sonochemical ligand substitution are first order in metal carbonyl concentration and independent of L concentration. In addition, In Kobd correlates well with solvent system vapor pressure. These results are consistent with a dissociative mechanism in which coordinatively unsaturated species are produced by the cavitation process. Further use of these transient intermediates is made as alkene isomerization catalysts. Sonocatalysis by a wide range of metal carbonyls shows many similarities to photocatalysis, but different relative efficiencies and selectivities have also been observed. |
| Title |
Sonochemistry in non-aqueous liquids. |
| Author |
Suslicka KS, Gawienowskia JJ, Schuberta PF, Wang HH |
| Journal |
Ultrasonics |
| Volume |
|
| Year |
1984 |
| Abstract |
The chemical effects of high-intensity ultrasound on organic liquids are reported. In order to probe the factors which affect sonochemistry in non-aqueous solvents, two very different chemical dosimeters have been used: radical trapping by diphenylpicrylhydrazyl and decomposition of Fe(CO)5. In both cases, good correlation is found between the logarithm of the sonochemical rate and the solvent vapour pressure. This result is justifiable in terms of the cavitation ‘hot-spot’ mechanism of sonochemistry. Thus, decreasing solvent vapour pressure increases the intensity of cavitational collapse, the peak temperature reached during such collapse, and, consequently, the rates of sonochemical reactions. |
| Title |
Sonochemistry of Mn2(CO)lo and Re2(CO)lo |
| Author |
Suslick KS, Schibert PF. |
| Journal |
J Am Chem Soc |
| Volume |
|
| Year |
1983 |
| Abstract |
Irradiation of liquids with high-intensity ultrasound creates, via cavitation, localized hot spots with transient pressures of >300 atm and temperatures -3000 K. We report the first studies of the chemical effects of ultrasound on Mn2(CO),o,
MnRe(CO)lo, and Re,(CO),,. Ultrasonic irradiation of Mn2(CO)lo produces ligand substitution by phosphines or phosphites.The rate of this substitution is independent of the choice of ligand or of its concentration, and the mechanism of substitution does not involve metal-metal bond cleavages. MnRe(CO),, and Re2(CO),, do not undergo sonochemical ligand substitution at appreciable rates, presumably because their lower vapor pressures preclude their presence in the cavitation event. In addition,we have found that Mn2(CO)lo and Re2(CO)lo undergo rapid sonochemical halogenation with halocarbon solvents, with rate
enhancement of los. The primary sonochemial event in these halogenations is homolysis of the solvent, generating halogen atoms (which can be trapped by M2(CO),, or by alkane solvent) and carbon radicals (which dimerize and have been so characterized. |
| Title |
Sonochemistry of sonodynamic therapy. |
| Author |
Riesz P, Misik V. |
| Journal |
J Acoust Soc Am |
| Volume |
|
| Year |
1998 |
| Abstract |
Sonodynamic therapy is a promising modality for cancer treatment based on the synergistic effect of cell killing by a combination of drugs (sonosensitizers) and ultrasound. The effectiveness of sonodynamic therapy was demonstrated in cell studies and in tumor‐bearing animals. The mechanism of drug‐dependent sonosensitization is unknown, but it seems likely that various mechanisms operate for different classes of sonosensitizers. Ultrasound‐mediated sonodynamic activation of porphyrins is particularly poorly understood and hypotheses ranging from singlet oxygen production to peroxyl radical formation have been advanced. Evidence has been obtained against some of the arguments which were proposed in favor of the singlet oxygen hypothesis and the requirement of extracellular localization of gallium porphyrin ATX‐70 molecules for sonosensitization in HL‐525 cells has been established. Short‐lived toxic intermediates produced from sonosensitizers by ultrasound are implicated in the mechanism of sonodynamic activation of some sensitizers. EPR spectroscopy was used to identify proposed intermediates in the activation of certain sonosensitizers (e.g., N,N‐dimethylformamide, DMSO) by ultrasound. Certain water‐soluble azo compounds, which are stable at hyperthermia temperatures and can be decomposed by ultrasound to give peroxyl radicals capable of initiating peroxidation of lipids and damaging other cellular sites, appear to be promising sonosensitizers. |
| Title |
Sonochemistry. |
| Author |
Suslick KS. |
| Journal |
Science |
| Volume |
|
| Year |
1990 |
| Abstract |
Ultrasound causes high-energy chemistry. It does so through the process of acoustic cavitation: the formation, growth ad implosive collapse of bubbles in a liquid. During cavitational collapse, intense heating of the bubbles occurs. These localized hot spots have temperatures of roughly 5000?C, pressures of about 500 atmospheres, and lifetimes of a few microseconds. Shock waves from cavitation in liquid-solid slurries produce high-velocity interparticle collisions, the impact of which is sufficient to melt most metals. Applications to chemical reactions exist in both homogeneous liquids and in liquid-solid systems. Of special synthetic use is the ability of ultrasound to create clean, highly reactive surfaces on metals. Ultrasound has also found important uses for initiation or enhancement of catalytic reactions, in both homogeneous and heterogeneous cases. |
| Title |
Sonodynamic approach to tumor treatment. |
| Author |
Umemura S, Kawabata K, Yumita N, Nishigaki R, Umemura K. |
| Journal |
Proc Ultrason Symp IEEE |
| Volume |
|
| Year |
1992 |
| Abstract |
In order to make sonodynamic modality for tumor treatment really feasible, researches on several aspects have been performed. Recent advances in these researches are described in this paper. Localization of sonochemical reactions with focused ultrasound is investigated by developing a sonochemically active tissue mimicking phantom. It is demonstrated that the sonochemical effects can be localized within a region of size not larger than typical tumors to be treated. Sonochemically efficient methods of ultrasound irradiation, which may neither require standing wave situations nor extremely high ultrasound intensity in order to induce substantial sonochemical effects, are studied. The newly proposed focal acoustic fields, the switched spiral focal field and the second-harmonic superimposed focal field, both induce sonochemical reaction rates higher in the order of magnitude than conventional CW or pulsed insonation at the same focal acoustic power. The ultrasound intensity threshold for the sonochemical reaction is drastically decreased by the second harmonic superimposition. It is also demonstrated by in vitro experiments that a gallium-deuteroporphyrin complex, ATX-70, has three times higher sonochemical activity than hematoporphyrin (Hp) and induces cell damage at twice higher a rate than Hp in combination with ultrasound. |
| Title |
Sonodynamic therapy to experimental hepatic tumor. [Article in Japanese] |
| Author |
Aoyagi T, Iida K, Matsuo K, Nonaka H, Sasaki K, Kawabata K, Umemura S, Yumita N, Nishigaki R, Umemura K |
| Journal |
Jpn J Med Ultrason |
| Volume |
|
| Year |
1993 |
| Abstract |
The effect of sonodynamic therapy on MRMT-1 hepatic tumor implanted to rats was investigated. The rat tumor was treated with focused ultrasound at 750 kHz from a prototype phased array transducer 24 hr after an administration of hematoporphyrin derivative (HpD). The focal spot with a peak intensity of 280 W/cm2 was scanned laterally in the tumor region resulting in the averaged intensity of 3.5 W/cm2 in the region. The echo texture pattern and the size of the tumor were observed with a 7.5 MHz ultrasound imaging system. The tumor size in the groups treated with ultrasound and HpD showed noticeable decrease 24, 48, and 72 hr after the treatment. The size decreased by 11.3% and 16.5%, 48 and 72 hr after the treatment, respectively. The texture pattern changed from hypoechoic to hyperechoic after the treatment. Histopathological observation showed that the sonodynamic treatment with HpD caused necrosis of the tumor tissue and cell-ballooning. Slight adverse effects were observed on the skin intervening between the tumor and the transducer and on the normal hepatic tissue surrounding the tumor. These results suggest that the sonodynamic therapy has a potential usefulness for the treatment of hepatic tumor. |
| Title |
Sonodynamic therapy--a review of the synergistic effects of drugs and ultrasound. |
| Author |
Rosenthal I, Sostaric JZ, Riesz P. |
| Journal |
Ultrason Sonochem |
| Volume |
|
| Year |
2004 |
| Abstract |
Sonodynamic therapy, the ultrasound dependent enhancement of cytotoxic activities of certain compounds (sonosensitizers) in studies with cells in vitro and in tumor bearing animals, is reviewed. The attractive features of this modality for cancer treatment emerges from the ability to focus the ultrasound energy on malignancy sites buried deep in tissues and to locally activate a preloaded sonosensitizer. Possible mechanisms of sonodynamic therapy include generation of sonosensitizer derived radicals which initiate chain peroxidation of membrane lipids via peroxyl and/or alkoxyl radicals, the physical destabilization of the cell membrane by the sonosensitizer thereby rendering the cell more susceptible to shear forces or ultrasound enhanced drug transport across the cell membrane (sonoporation). Evidence against the role of singlet oxygen in sonodynamic therapy is discussed. The mechanism of sonodynamic therapy is probably not governed by a universal mechanism, but may be influenced by multiple factors including the nature of the biological model, the sonosensitizer and the ultrasound parameters. The current review emphasizes the effect of ultrasound induced free radicals in sonodynamic therapy. |
| Title |
Sonodynamically induced antitumor effect of a gallium-porphyrin complex, ATX-70. |
| Author |
Yumita N, Sasaki K, Umemura S, Nishigaki R. |
| Journal |
Jpn J Cancer Res |
| Volume |
|
| Year |
1996 |
| Abstract |
The sonodynamically induced antitumor effect of a gallium-porphyrin complex, ATX-70, was.evaluated in mice bearing colon 26. In order to find the optimum timing for the ultrasonic.exposure after the administration of ATX-70, the ATX-70 concentrations in the plasma, skin,.and tumor were measured and analyzed. Antitumor effect was estimated by measuring the tumor.size. When used alone, ultrasound showed a slight antitumor effect, which became increasingly.significant as the dose of ATX-70 was increased, while use of ATX-70 alone had no significant.effect. At an ATX-70 dose of 2.5 mg/kg or higher, the average tumor size decreased to smaller.than a half by three days after the ultrasonic exposure. This was smaller than a third of the size of the untreated tumors on the same day. From these results, it is concluded that ATX-70.significantly sensitizes tumors to ultrasound, demonstrating a synergistic antitumor effect. |
| Title |
Sonodynamically induced antitumor effect of pheophorbide a. |
| Author |
Umemura K, Yumita N, Nishigaki R, Umemura S. |
| Journal |
Cancer Lett |
| Volume |
|
| Year |
1996 |
| Abstract |
The sonodynamically induced antitumor effect of pheophorbide a (Ph-a) was investigated. Both.in vitro and in vivo effects on sarcoma 180 were tested in combination with ultrasound at 2 MHz..The rate of ultrasonically induced cell damage in air-saturated suspension was enhanced by twice.with 80 microM Ph-a. This enhancement was significantly inhibited by histidine, which may.suggest it was mediated by ultrasonically induced oxidation. For mice, 5 mg/kg Ph-a was.administered before the insonation, and ultrasound stopped the tumor growth at an intensity with.which ultrasound alone showed only a slight antitumor effect. |
Page 1
| 2
| 3
| 4
| 5
| 6
| 7
| 8
| 9
| 10
| 11
| 12
| 13
| 14
| 15
| 16
| 17
| 18
| 19
| 20
| 21
| 22
| 23
| 24
| 25
| 26
| 27
| 28
| 29
| 30
| 31
| 32
| 33
| 34
| 35
| 36
| 37
| 38
| 39
| 40
| 41
| 42
| 43
| 44
| 45
| 46
| 47
| 48
| 49
| 50
| 51
| 52
| 53
| 54
| 55
| 56
| 57
| 58
| 59
| 60
| 61
| 62
| 63
| 64
| 65
| 66
| 67
| 68
| 69
| 70
| 71
| 72
| 73
| 74
| 75
| 76
| 77
| 78
| 79
| 80
| 81
| 82
| 83
| 84
| 85
| 86
| 87
| 88
| 89
| 90
| 91
| 92
| 93
| 94
| 95
| 96
| 97
| 98
| 99
| 100
| 101
| 102
| 103
| 104
| 105
| 106
| 107
| 108
| 109
| 110
| 111
| 112
| 113
| 114
| 115
| 116
| 117
| 118
| 119
| 120
| 121
| 122
| 123
| 124
| 125
| 126
| 127
| 128
| 129
| 130
| 131
| 132
| 133
| 134
| 135
| 136
| 137
| 138
| 139
| 140
| 141
| 142
| 143
| 144
| 145
| 146
| 147
| 148
| 149
| 150
| 151
| 152
| 153
| 154
| 155
| 156
| 157
| 158
| 159
| 160
| 161
| 162
| 163
| 164
| 165
| 166
| 167
| 168
| 169
| 170
| 171
| 172
| 173
| 174
| 175
| 176
| 177
| 178
| 179
| 180
| 181
| 182
| 183
| 184
| 185
| 186
| 187
| 188
| 189
| 190
| 191
| 192
| 193
| 194
| 195
| 196
| 197
| 198
| 199
| 200
| 201
| 202
| 203
| 204
| 205
| 206
| 207
| 208
| 209
| 210
| 211
| 212
| 213
| 214
| 215
| 216
| 217
| 218
| 219
| 220
| 221
| 222
| 223
| 224
| 225
| 226
| 227
| 228
| 229
| 230
| 231
| 232
| 233
| 234
| 235
| 236
| 237
| 238
| 239
| 240
| 241
| 242
| 243
| 244
| 245
| 246
| 247
| 248
| 249
| 250
| 251
| 252
| 253
| 254
| 255
| 256
| 257
| 258
| 259
| 260
| 261
| 262
| 263
| 264
| 265
| 266
| 267
| 268
| 269
| 270
| 271
| 272
| 273
| 274
| 275
| 276
| 277
| 278
| 279
| 280
| 281
| 282
| 283
| 284
| 285
| 286
| 287
| 288
| 289
| 290
| 291
| 292
| 293
| 294
| 295
| 296
| 297
| 298
| 299
| 300
| 301
| 302
| 303
| 304
| 305
| 306
| 307
| 308
| 309
| 310
| 311
| 312
| 313
| 314
| 315
| 316
| 317
| 318
| 319
| 320
| 321
| 322
| 323
| 324
| 325
| 326
| 327
| 328
| 329
| 330
|
|
|
|
