Ultrafast heating as a sufficient stimulus for magnetization reversal in a ferrimagnet

The question of how, and how fast, magnetization can be reversed is a topic of great practical interest for the manipulation and storage of magnetic information. It is generally accepted that magnetization reversal should be driven by a stimulus represented by time-non-invariant vectors such as a magnetic field, spin-polarized electric current, or cross-product of two oscillating electric fields. However, until now it has been generally assumed that heating alone, not represented as a vector at all, cannot result in a deterministic reversal of magnetization, although it may assist this process. Here we show numerically and demonstrate experimentally a novel mechanism of deterministic magnetization reversal in a ferrimagnet driven by an ultrafast heating of the medium resulting from the absorption of a sub-picosecond laser pulse without the presence of a magnetic field.

Mutations in the core and NS5A region of hepatitis C virus genotype 1b and correlation with response to pegylated-interferon-alpha 2b and ribavirin combination therapy

Mutations in two regions of hepatitis C virus (HCV) have been implicated in influencing response to interferon (IFN) therapy. Substitutions in the NS5A region of HCV have been associated with response to IFN therapy, and this region has been known as the IFN sensitivity-determining region (ISDR). The mutations in the core region of HCV have also been reported to predict IFN response. The aim of this study was to investigate whether amino acid substitutions in the core region and ISDR among patients with HCV genotype 1b affect the response to IFN therapy. A total of 213 patients who completed IFN treatment were randomly selected. All patients received pegylated-IFN-alpha 2b once each week, plus oral ribavirin daily for 48 weeks. Of the 213 patients, 117 (54.9%) showed early virologic response (EVR), with HCV-negativity, at 12 weeks. Factors related to EVR on multivariate analysis were non-Gln70 and Leu91 in the core region, and ISDR mutant-type. One hundred and two (47.9%) showed a sustained virologic response (SVR). SVR occurred more frequently in patients without Gln70 (55.4%) than in those with Gln70 (21.3%) (P < 0.0001). SVR was achieved in 43.6% of patients with wild-type ISDR and 62.5% of patients with mutant-type (P = 0.0227). Of the 34 patients who simultaneously had non-Gln70 and mutant-type ISDR, 26 (76.5%) achieved SVR. Factors related to SVR on multivariate analysis were non-Gln70 and ISDR mutant-type. In conclusion, amino acid substitutions in the core region and ISDR were useful for predicting the response to IFN in patients with HCV genotype 1b.

Transient ferromagnetic-like state mediating ultrafast reversal of antiferromagnetically coupled spins

Ferromagnetic or antiferromagnetic spin ordering is governed by the exchange interaction, the strongest force in magnetism. Understanding spin dynamics in magnetic materials is an issue of crucial importance for progress in information processing and recording technology. Usually the dynamics are studied by observing the collective response of exchange-coupled spins, that is, spin resonances, after an external perturbation by a pulse of magnetic field, current or light. The periods of the corresponding resonances range from one nanosecond for ferromagnets down to one picosecond for antiferromagnets. However, virtually nothing is known about the behaviour of spins in a magnetic material after being excited on a timescale faster than that corresponding to the exchange interaction (10-100 fs), that is, in a non-adiabatic way. Here we use the element-specific technique X-ray magnetic circular dichroism to study spin reversal in GdFeCo that is optically excited on a timescale pertinent to the characteristic time of the exchange interaction between Gd and Fe spins. We unexpectedly find that the ultrafast spin reversal in this material, where spins are coupled antiferromagnetically, occurs by way of a transient ferromagnetic-like state. Following the optical excitation, the net magnetizations of the Gd and Fe sublattices rapidly collapse, switch their direction and rebuild their net magnetic moments at substantially different timescales; the net magnetic moment of the Gd sublattice is found to reverse within 1.5 picoseconds, which is substantially slower than the Fe reversal time of 300 femtoseconds. Consequently, a transient state characterized by a temporary parallel alignment of the net Gd and Fe moments emerges, despite their ground-state antiferromagnetic coupling. These surprising observations, supported by atomistic simulations, provide a concept for the possibility of manipulating magnetic order on the timescale of the exchange interaction.

Ultrafast path for optical magnetization reversal via a strongly nonequilibrium state

Using time-resolved single-shot pump-probe microscopy we unveil the mechanism and the time scale of all-optical magnetization reversal by a single circularly polarized 100 fs laser pulse. We demonstrate that the reversal has a linear character, i.e., does not involve precession but occurs via a strongly nonequilibrium state. Calculations show that the reversal time which can be achieved via this mechanism is within 10 ps for a 30 nm domain. Using two single subpicosecond laser pulses we demonstrate that for a 5 microm domain the magnetic information can be recorded and readout within 30 ps, which is the fastest "write-read" event demonstrated for magnetic recording so far.

Amphotericin B-induced nephrotoxicity: characterization of blood and urinary biochemistry and renal morphology in mice

This study was conducted to characterize blood and urinary biochemistry, and renal morphology, after single or 1-week repeated dosing of mice with the polyene macrolide antibiotic, amphotericin B (AMB). AMB was intravenously administered to mice at 2 or 4 mg/kg for the single-dose experiment or once daily at 1 or 2 mg/kg for 1 week for the repeated-dose experiment. The most prominent histopathological findings included necrosis of the tubular epithelial cells in the thick ascending limb of Henle's loop in the renal outer medulla at a single dose of 2 or 4 mg/kg, and the severity of the lesion was dose-dependent. Blood chemistry and urinalysis revealed several changes suggestive of renal dysfunction such as reduction of plasma filtration ability (increases in plasma creatinine and blood urea nitrogen, a decrease in creatinine clearance) and polyuria accompanied with dehydration (decrease in renal water reabsorption, increases in plasma total protein and albumin) at a dose of 4 mg/kg in the single-dose experiment. Among the parameters analyzed, urinary lactate dehydrogenase was the most sensitive and reliable parameter for the prediction of AMB-induced nephrotoxicity in mice. These data provided comprehensive information on the nephrotoxicity of AMB and indicate useful markers for the sensitive detection of AMB-induced renal injury in mice.

Subpicosecond magnetization reversal across ferrimagnetic compensation points

Subpicosecond magnetization reversal is experimentally demonstrated by ultrafast heating of a ferrimagnet across its compensation points, under an applied magnetic field. While the reversal is initiated by crossing the magnetization compensation temperature, the short reversal time is related to the angular momentum compensation, where the dynamics of the system is highly accelerated owing to the divergence of the gyromagnetic ratio. These results demonstrate the feasibility of subpicosecond magnetization reversal previously believed impossible.

All-optical magnetic recording with circularly polarized light

We experimentally demonstrate that the magnetization can be reversed in a reproducible manner by a single 40 femtosecond circularly polarized laser pulse, without any applied magnetic field. This optically induced ultrafast magnetization reversal previously believed impossible is the combined result of femtosecond laser heating of the magnetic system to just below the Curie point and circularly polarized light simultaneously acting as a magnetic field. The direction of this opto-magnetic switching is determined only by the helicity of light. This finding reveals an ultrafast and efficient pathway for writing magnetic bits at record-breaking speeds.

Combined treatment with immunotherapy and chemotherapy using endoscopic ultrasonography guided injection for locally advanced pancreatic carcinoma

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Background: Dendritic cells (DCs) play a pivotal role in T cell-mediated immunity. Usually, mature DCs were cultured using resected tumor tissue, but for inoperable cases, this method is impractical. The injection of immature DCs into the tumor after appropriate chemotherapy is reasonable, if DCs come to maturity capturing the specific cancer antigen . The aim of this study is to assess the toxicity and efficacy of combined treatment with immunotherapy and chemotherapy for locally advanced pancreatic carcinoma. Methods: Five patients with pathologically confirmed pancreatic ductal carcinoma using EUS-FNA were enrolled, median age 56 years (range, 46–70 years). All cases without distant metastasis were diagnosed as surgically unresectable . Patients underwent leukapheresis, immature DCs were prepared from peripheral blood by a culture with granulocyte macrophage colony-stimulating factor and interleukin 4. Lymphokine-activated killer (LAK) were also prepared from peripheral blood. Immature DCs were injected biweekly in the mass by endoscopic ultrasound-guided fine needle injection (EUS-FNI), LAK were administered intravenously. Patients received the treatment of gemcitabine 1000 mg / m2 by intravenous injection 3 days before the immunotherapy. One course with 6 times combined therapy was continued until the judgment of progressive diseases (PD) was given. The toxicity and efficacy of this treatment were assessed. We also assessed whether tumor associated antigen (TAA)-specific IFN-?producing cells increase after treatment. Results: Hematological toxicity occurred in one case, leucopenia of grade 2. No severe toxicities of grade 3 to 4 occurred. One had a partial response (PR), stable disease (SD) was observed in 2 patients for more than 6 months (long-term SD). PR patient could undergo curative operation after this therapy. The number of TAA-specific IFN-?producing cells in PR patient increased 12-fold higher than that seen before treatments. Conclusions: These results support the safety and efficacy of combined treatment with immunotherapy and chemotherapy for locally advanced pancreatic ductal carcinoma. This treatment may be a useful for the treatment of pancreatic ductal carcinoma.

No significant financial relationships to disclose.

Neopterin is associated with plaque inflammation and destabilisation in human coronary atherosclerotic lesions

BACKGROUND

Previous studies have shown that recent activation of the inflammatory response in coronary atherosclerotic lesions contributes to rapid progressive plaque destabilisation. Neopterin, a by-product of the guanosine triphosphate pathway, is produced by activated macrophages and serves as an activation marker for monocytes/macrophages.

OBJECTIVE

To elucidate the role of neopterin in coronary plaque destabilisation by immunohistochemical study of the presence of neopterin in coronary atherectomy specimens obtained from patients with stable angina pectoris (SAP) and unstable angina pectoris (UAP).

PATIENTS AND METHODS

All patients underwent atherectomy of the primary atherosclerotic lesions responsible for SAP (n = 25) and UAP (n = 25). Frozen samples were studied with antibodies against smooth muscle cells, macrophages, T cells, neutrophils and neopterin.

RESULTS

In 22/25 patients with UAP, abundant neopterin-positive macrophages were found at the sites of coronary culprit lesions. However, in 25 lesions from patients with SAP, only 11 lesions showed neopterin positivity. Quantitatively, the neopterin-positive macrophage score was significantly higher (p<0.001) in patients with UAP than in patients with SAP. Moreover, the neopterin-positive macrophage score showed a significant positive correlation with the number of neutrophils or T cells, respectively (neutrophils, r = 0.55, p<0.001; T cells, r = 0.70, p<0.001).

CONCLUSIONS

Neopterin can be considered as one of the significant factors in the process of plaque inflammation and destabilisation in human coronary atherosclerotic lesions. Its exact role in the process needs to be investigated further.