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L M Wang

Publications and source records attributed to L M Wang.

At least 19 recordsLinked to original sources
PubMed2006

Anomalous Hall effect in La0.7Sr0.3MnO3/SrTiO3 superlattices: hopping transport and a probe of dimensionality.

The anomalous Hall effect (AHE) in La0.7Sr0.3MnO3/SrTiO3 (LSMO/STO) superlattices was analyzed using theories of the Berry phase effect. The temperature-dependent anomalous Hall coefficient Rs is found to be expressed by -Rs = Rs0 exp[(T/T0)1.5], where Rs0 is a prefactor and T0 is in units of kelvin, and is explained by the carrier-hopping mechanism. In addition, a scaling analysis for the Hall resistivity as a function of magnetization supports the scenario of the Berry phase effects. Furthermore, a shifting extremum of Hall resistivity in LSMO/STO superlattices is observed and regarded as a probe of dimensionality in quasi-two-dimensional systems.

Journal Article↗
PubMed2006

Effect of structure and thermodynamic stability on the response of lanthanide stannate pyrochlores to ion beam irradiation.

The lanthanide stannates, Ln2Sn2O7, Ln=La-Lu and Y, have the isometric pyrochlore structure, A2B2O7, and their structural properties have been refined by Rietveld analysis of powder neutron and synchrotron X-ray diffraction data. In this study, the enthalpies of formation of selected stannate pyrochlores, Ln=La, Nd, Sm, Eu, Dy, and Yb, were measured by high-temperature oxide melt solution calorimetry. Their radiation response was determined by 1 MeV Kr2+ ion irradiation combined with in situ TEM observation over the temperature range of 25 to 1000 K. The enthalpy of formation from binary oxides of stannate pyrochlores became more endothermic (from -145 to -40 kJ/mol) as the size of the lanthanide in the A-site decreases. A more exothermic trend of the enthalpy of formation was observed in stannate pyrochlores with larger lanthanide ions, particularly La, possibly as a result of increased covalency in the Sn-O bond. In contrast to lanthanide titanate pyrochlores, Ln2Ti2O7, that are generally susceptible to radiation-induced amorphization and zirconate pyrochlores, Ln2Zr2O7, that are generally resistant to radiation-induced amorphization, the lanthanide stannate pyrochlores show a much greater variation in their response to ion irradiation. La, Nd, and Gd stannates experience the radiation-induced transformation to the aperiodic state, and the critical amorphization temperatures are approximately 960, 700, and 350 K, respectively. Y and Er stannate pyrochlores cannot be amorphized by ion beam irradiation, even at 25 K, and instead disorder to a defect fluorite structure. Comparison of the calorimetric and ion irradiation data for titanate, zirconate, and stannate pyrochlores reveals a strong correlation among subtle changes in crystal structure with changing composition, the energetics of the disordering process, and the temperature above which the material can no longer be amorphized. In summary, as the structure approaches the ideal, ordered pyrochlore structure, radiation-induced amorphization is more easily attained. This is consistent with an increasingly exothermic trend in the enthalpies of formation of pyrochlores from the oxides, that is, the greater the thermochemical stability of the pyrochlore structure, the more likely it will be amorphized upon radiation damage rather than recover to a disordered fluorite structure.

Journal Article↗
PubMed2005

Body-centered-cubic Ni and its magnetic properties.

The body-centered-cubic (bcc) phase of Ni, which does not exist in nature, has been achieved as a thin film on GaAs(001) at 170 K via molecular beam epitaxy. The bcc Ni is ferromagnetic with a Curie temperature of 456 K and possesses a magnetic moment of 0.52+/-0.08 micro(B)/atom. The cubic magnetocrystalline anisotropy of bcc Ni is determined to be +4.0x10(5) ergs x cm(-3), as opposed to -5.7x10(4) ergs x cm(-3) for the naturally occurring face-centered-cubic (fcc) Ni. This sharp contrast in the magnetic anisotropy is attributed to the different electronic band structures between bcc Ni and fcc Ni, which are determined using angle-resolved photoemission with synchrotron radiation.

Journal Article↗
PubMed2002

X-ray photoelectron spectroscopy study of disordering in Gd2(Ti1-xZrx)2O7 pyrochlores.

The dramatic increases in ionic conductivity in Gd2(Ti1-xZrx)2O7 solid solution are related to disordering on the cation and anion lattices. Disordering in Gd2(Ti1-xZrx)2O7 was characterized using x-ray photoelectron spectroscopy (XPS). As Zr substitutes for Ti in Gd2Ti2O7 to form Gd2(Ti1-xZrx)2O7 (0.25 < x < or =0.75), the corresponding O 1s XPS spectrum merges into a single symmetric peak. This confirms that the cation antisite disorder occurs simultaneously with anion disorder. Furthermore, the O 1s XPS spectrum of Gd2Zr2O7 experimentally suggests the formation of a split vacancy.

Journal Article↗
PubMed2002

Paget's disease of bone: presentation, extent and response to bisphosphonates.

According to a radiograph survey in 1982, Paget's disease of bone is common in Ireland but, to date, there have been no clinical reports. In a survey of 24 patients with Paget's disease of bone, we found monostotic disease in 8 and polyostotic disease in 16. Complications were common including deformity (21%), fracture (17%) and deafness (8%). Bisphosphonate therapy induced a remission in 22 patients.

Aged↗
PubMed2001

Nanoscale manipulation of pyrochlore: new nanocomposite ionic conductors.

The ionic conductivity of isometric pyrochlore, ideally A2B2O (7), is extremely sensitive to disordering of A- and B-site cations and oxygen anion vacancies. We report the first use of ion beam irradiation-induced disordering in Gd 2Ti 2O (7) to produce a strain-free, buried, disordered defect-fluorite layer approximately 12 nm thick within an ordered pyrochlore matrix. This approach provides a new means of creating nanoscale, mixed ionic-electronic conductors in pyrochlore ceramics, such as those required for solid-state electrochemical cells.

Journal Article↗
PubMed2001

Neutralizing monoclonal antibodies to hepatocyte growth factor/scatter factor (HGF/SF) display antitumor activity in animal models.

The hepatocyte growth factor (HGF/SF) receptor, Met, regulates mitogenesis, motility, and morphogenesis in a cell type-dependent fashion. Activation of Met via autocrine, paracrine, or mutational mechanisms can lead to tumorigenesis and metastasis and numerous studies have linked inappropriate expression of this ligand-receptor pair to most types of human solid tumors. To prepare mAbs to human HGF/SF, mice were immunized with native and denatured preparations of the ligand. Recloned mAbs were tested in vitro for blocking activity against scattering and branching morphogenesis. Our results show that no single mAb was capable of neutralizing the in vitro activity of HGF/SF, and that the ligand possesses a minimum of three epitopes that must be blocked to prevent Met tyrosine kinase activation. In vivo, the neutralizing mAb combination inhibited s.c. growth in athymic nu/nu mice of tumors dependent on an autocrine Met-HGF/SF loop. Importantly, growth of human glioblastoma multiforme xenografts expressing Met and HGF/SF were markedly reduced in the presence of HGF/SF-neutralizing mAbs. These results suggest interrupting autocrine and/or paracrine Met-HGF/SF signaling in tumors dependent on this pathway is a possible intervention strategy.

Animals↗
PubMed2001

Diagnosis of appendicitis in the ED: comparison of surgical and nonsurgical residents.

The purpose of this study was to evaluate the impact of a surgery-based (SB) versus nonsurgery-based (NSB) training background of residents on the diagnosis of acute appendicitis in the emergency department (ED). The medical records of 641 adult patients who had undergone an appendectomy during a 3-year period (July 1996 to June 1999) were reviewed. All the patients were divided into NSB-in charge (n = 367) and SB-in charge (n = 274) groups, and demographic and clinical data recorded. Both groups' patients showed no differences in either negative appendectomy or perforation rates. However, NSB group patients had longer in-hospital delays in comparison with SB group patients (12.0 +/- 0.7 versus 9.6 +/- 0.4 hours, P <.05). This longer stay time mainly occurred in the patients with negative exploration and uncomplicated appendicitis P <.05). In both groups, patients with complicated appendicitis had longer prehospital delay of presentation than those with uncomplicated appendicitis. (2.0 +/- 0.2 versus 1.2 +/- 0.1 days in NSB group; 2.5 +/- 0.5 versus 1.3 +/- 0.2 days in SB group, P <.01). The NSB residents tended to order more computed tomography (CT) scans than SB residents (12% versus 5.1%, P <.05). With the application of a CT scan, the negative appendectomy rate was reduced significantly from 23% to 12%. We concluded that under the supervision of board-certified emergency physicians, the NSB residents had capabilities similar to SB residents in making correct diagnoses of acute appendicitis. In addition, close observation of equivocal cases in the ED did not necessarily increase the perforation rate.

Adult↗
PubMed2001

Spectral changes in systemic arterial pressure signals during acute mevinphos intoxication in the rat.

We investigated the cardiovascular consequences of acute intoxication by the organophosphate poison, mevinphos (Mev), and delineated the underlying mechanism. Based on on-line power spectral analysis of systemic arterial pressure (SAP) signals in rats anesthetized and maintained by propofol, we identified two distinct phases after intravenous administration of Mev (160 or 320 microg/kg). Phase I was characterized by transient hypertension and mild tachycardia, concurrent with an increase in the very high-frequency (BVHF; 5-9 Hz), high-frequency (BHF; 0.8-2.4 Hz), low-frequency (BLF; 0.25-0.8 Hz),and very low-frequency (BVLF; 0-0.25 Hz) components of SAP signals. Phase II exhibited significant hypotension, a reversal of the BVHF and BVLF power to control levels, and further reduction in the power density of both BHF and BLF components to below baseline. Microinjection of Mev (2 microg) into the bilateral nucleus reticularis ventrolateralis (NRVL), the medullary origin of sympathetic neurogenic vasomotor tone, essentially duplicated those phasic cardiovascular changes. Similarly, sympathoexcitatory NRVL neurons exhibited respectively an elevation and a decline in their spontaneous activities during Phase I and Phase II Mev intoxication. We conclude that the progressive accumulation of acetylcholine over time induced by a direct inhibition of Mev on cholinesterase in the NRVL may be responsible for the phasic changes in cardiovascular events over the course of acute Mev intoxication. Whereas the initial amount of acetylcholine is excitatory to NRVL neurons, overstimulation by the amassed acetylcholine results instead of an inhibitory action.

Animals↗
PubMed2001

Development of neurotrophic molecules for treatment of neurodegeneration.

Over the past several years, neurotrophic factors have made considerable progress from the laboratory into the clinic. Evidence from preclinical and clinical studies indicates that it may be possible to use neurotrophic factors to prevent, slow the progression of, or even reverse the effects of a number of neurodegenerative diseases and other types of insults in both the central and peripheral nervous system. Their potential importance in the development of therapeutic agents against neurodegenerative disorders and nerve injury has led to a flurry of activity towards understanding their structure, function and signalling mechanisms. Approaches to develop pharmacological agents that target neurotrophic factors, their receptors or neurotrophic factors signalling pathways have been attempted. This review focuses on some of the major themes and lines of mechanistic and therapeutic advances in this fast-moving field of neuroscience.

Animals↗
PubMed2001

[Effects of heat stress on DA mediated PI signal transduction system in rat striatum].

Objective. To study the effects of heat stress on dopamine (DA) and related phosphatidylinositol (PI) signal transduction system members: PLA2, PI, Ca2+ in rat striatum. Method. Male Wistar rats were randomly divided into control group and heat stressed group. Heat stressed rats were placed in small hot chambers and taken out as soon as their rectal temperatures (Tr) reached the preset temperature. Then the animals were killed and their striatums were taken out. Fluorospectrophotometry, HPLC, Fura-2/AM fluoresence labelled method and acidalkaline titration were used to measure the content of DA, PI, [Ca2+]i and the enzyme activity of PLA2. Result. During heat stress, when rats' Tr reached 41.0 degrees C or higher, with increase of Tr, DA content increased continuously. When Tr = 43.0 degrees C, DA content was significantly higher than control. When Tr = 41.0 degrees C PLA2 activity was higher than control significantly, PI content of heat stressed group decreased significantly than control. [Ca2+]i increased significantly when Tr = 42.0 degrees C as compared with control. But if DA receptor2 (D2R) antagonist was given an hour before heat stress, [Ca2+]i decreased and Tr took a longer time to get to 42.0 degrees C. Conclusion. During heat stress, DA mediated PI signal transduction system was activated. The increase of [Ca 2+]i might be mediated by D2R, and D2R antagonist may improve thermotolerance.

Animals↗
PubMed2001

Tele-emergency medicine: the evaluation of Taipei Veterans General Hospital and Kinmen-Granite Hospital in Taiwan.

BACKGROUND: The purpose of the project was to establish computer networks between selected hospitals through high-speed communication and high power computer processing to electronically exchange medical information and to conduct clinical examination and consultation. Quality medical services can thus be provided to patients in the remote rural areas such as villages and small towns in the mountains, on the coasts and islets away from Taiwan. It also intended to facilitate continuing education for doctors in those areas. This study evaluates telemedicine between Taipei-Veterans General Hospital and Kinmen-Granite Hospital. METHODS: Patients were chosen from 1996-7 to 1997-6. The evaluation criteria included consulting quality, satisfaction of the doctors, benefits for the patients, and the charge being rendered. RESULTS: The results of evaluation for telemedicine between Taipei-Veterans General Hospital (VGHTPE) and Kinmen-Granite hospital (GH) are as follows: 93.0% doctors used telemedicine to seek a second opinion. After teleconsultation, the ratio of the patients showing cooperation was over 80%. Over 98% doctors thought telemedicine system helpful. The doctors in VGHTPE are more satisfied with the facility than local doctors in Kinmen. CONCLUSIONS: The clinical evaluation of the telemedicine showed positive results. It can be a useful tool to facilitate on-job training and education Tele-emergency medicine.

Adolescent↗
PubMed2001

The involvement of bradykinin in adrenaline-induced pulmonary edema in rats.

We investigated the effect of endogenous bradykinin on adrenaline-induced pulmonary edema (PE) by blocking bradykinin receptors. In preliminary experiments, a bolus injection of adrenaline (ADR; 10 microg/kg) solution (10 microg/ml) was determined to be an edematogenic dose for inducing PE. The lung body weight index (LBI) and incidence of PE (IPE) were determined. The IPE and LBI of the group pretreated with Des-Arg9-[Leu8]-Bradykinin (DA-BK, 50 microg/kg, 50 microg/ml) increased significantly compared with those of the control group (p<0.05). On the other hand, there were no remarkable changes in IPE and LBI in the groups pretreated with Hoe140 (D-Arginyl-[Hyp3, Thi5, D-Tic7, Oic8]-Bradykinin (100 microg/kg, 100 microg/ml), captopril (20 mg/kg, 20 mg/ml) or L-NAME (1 mg/kg, 1 mg/ml). Moreover, the IPE and LBI of the group co-treated with L-NAME and DA-BK decreased compared with the DA-BK group (p<0.05). Thus, bradykinin aggravates adrenaline-induced PE through activation of the B2 receptor by the kallikreins as a result of the ADR administration, although the precise mechanism is not known.

Adrenergic alpha-Antagonists↗
PubMed2000

Huperzine A improves cognitive deficits caused by chronic cerebral hypoperfusion in rats.

The effects of (-)-huperzine A, a promising therapeutic agent for Alzheimer's disease, on learning behavior and on alterations of the cholinergic system, the oxygen free radicals and energy metabolites induced by permanent bilateral ligation of the common carotid arteries were investigated in rats. Daily oral administration of huperzine A produced a significant improvement of the deficit in the learning of the water maze task, beginning 28 days after ischemia, correlating to about 33-40% inhibition of acetylcholinesterase activity in cortex and hippocampus. Huperzine A significantly restored the decrease in choline acetyltransferase activity in hippocampus and significantly reduced the increases in superoxide dismutase, lipid peroxide, lactate and glucose to their normal levels. The present findings demonstrate that the improvement by huperzine A of the cognitive dysfunction in the late phase in chronically hypoperfused rats is due to its effects, not only on the cholinergic system, but also on the oxygen free radical system and energy metabolism. Our results strongly suggest that huperzine A has therapeutic potential for the treatment of dementia caused by cholinergic dysfunction and/or decrease of cerebral blood flow.

Acetylcholinesterase↗
PubMed2000

Cyclic nucleotide phosphodiesterase 3B is a downstream target of protein kinase B and may be involved in regulation of effects of protein kinase B on thymidine incorporation in FDCP2 cells.

Wild-type (F/B), constitutively active (F/B*), and three kinase-inactive (F/Ba-, F/Bb-, F/Bc-) forms of Akt/protein kinase B (PKB) were permanently overexpressed in FDCP2 cells. In the absence of insulin-like growth factor-1 (IGF-1), activities of PKB, cyclic nucleotide phosphodiesterase 3B (PDE3B), and PDE4 were similar in nontransfected FDCP2 cells, mock-transfected (F/V) cells, and F/B and F/B- cells. In F/V cells, IGF-1 increased PKB, PDE3B, and PDE4 activities approximately 2-fold. In F/B cells, IGF-1, in a wortmannin-sensitive manner, increased PKB activity approximately 10-fold and PDE3B phosphorylation and activity ( approximately 4-fold), but increased PDE4 to the same extent as in F/V cells. In F/B* cells, in the absence of IGF-1, PKB activity was markedly increased ( approximately 10-fold) and PDE3B was phosphorylated and activated (3- to 4-fold); wortmannin inhibited these effects. In F/B* cells, IGF-1 had little further effect on PKB and activation/phosphorylation of PDE3B. In F/B- cells, IGF-1 activated PDE4, not PDE3B, suggesting that kinase-inactive PKB behaved as a dominant negative with respect to PDE3B activation. Thymidine incorporation was greater in F/B* cells than in F/V cells and was inhibited to a greater extent by PDE3 inhibitors than by rolipram, a PDE4 inhibitor. In F/B cells, IGF-1-induced phosphorylation of the apoptotic protein BAD was inhibited by the PDE3 inhibitor cilostamide. Activated PKB phosphorylated and activated rPDE3B in vitro. These results suggest that PDE3B, not PDE4, is a target of PKB and that activated PDE3B may regulate cAMP pools that modulate effects of PKB on thymidine incorporation and BAD phosphorylation in FDCP2 cells.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed2000

Heat stroke in a subtropical country.

In Taiwan, a subtropical country without any history of heat waves, heat stroke has been considered a rare disease. However, after seeing several cases of the classic type of heat stroke at the end of the summer of 1998 (an unusual event) we began to review and collect cases of suspected heat stroke (hyperthermia (>40.6 degrees C) in the presence of altered mental status and anhidrosis) and tried to explore the possible cause of this unusual phenomenon. Through a emergency department (ED) chart review, case retraction from International Classification of Diseases (ICD) code, and ED conferences, six patients were found for the period from June to August (the hottest months in Taiwan) 1998. We found that the most common comorbid conditions were hypertension (4/6) and preexisting mental problems (3/6). All patients lived in the inner part of an urban area, were middle class, and were not socially isolated. Most of our patients felt unhealthy being exposed to the cold and avoided staying in air-conditioned rooms. Laboratory abnormalities and clinical presentations, except for a high fever and conscious change, seemed to be nonspecific. All cases occurred during two periods of sustained hotter-than-average weather and, to our surprise, we found that three episodes occurred around the day of the highest weather temperature (38.1 degrees C). However, the higher temperatures (around 30 degrees to 31 degrees C and 32 degrees to 33 degrees C) did not reach the criteria of a heat wave. Compared with the other study, our patients seemed to have initial worse outcomes. Because of special environment and social factors, classic heat stroke may occur occasionally in subtropic regions, without previous history of heat waves and where heat stroke rarely occurs, during periods of the persistently high temperatures. Prevention of heat stroke in an area with a low incidence includes early health organizations' issue of advisories or warnings through the media and reminding or teaching emergency physicians about heat stroke during sustained hot weather, especially when record temperatures are set.

Aged↗