Phononic switching of magnetization by the ultrafast Barnett effect.

The historic Barnett effect describes how an inertial body with otherwise zero net magnetic moment acquires spontaneous magnetization when mechanically spinning1,2. Breakthrough experiments have recently shown that an ultrashort laser pulse destroys the magnetization of an ordered ferromagnet within hundreds of femtoseconds3, with the spins losing angular momentum to circularly polarized optical phonons as part of the ultrafast Einstein-de Haas effect4,5. However, the prospect of using such high-frequency vibrations of the lattice to reciprocally switch magnetization in a nearby magnetic medium has not yet been experimentally explored. Here we show that the spontaneous magnetization gained temporarily by means of the ultrafast Barnett effect, through the resonant excitation of circularly polarized optical phonons in a paramagnetic substrate, can be used to permanently reverse the magnetic state of a heterostructure mounted atop the said substrate. With the handedness of the phonons steering the direction of magnetic switching, the ultrafast Barnett effect offers a selective and potentially universal method for exercising ultrafast non-local control over magnetic order.

Olsalazine inhibits cell proliferation and DNA methylation in canine lymphoid tumor cell lines.

Abnormal DNA methylation is involved in the initiation and progression of lymphoid tumors. Hence, DNA demethylating agents are promising candidate drugs for chemotherapy against these tumors. The salicylic acid derived anti-inflammatory agent, olsalazine, reportedly suppresses DNA methyltransferase in human cells and has the potential to be clinically applied as a DNA demethylating agent. In this study, we investigated the effects of olsalazine on cell proliferation and DNA methylation using canine lymphoid tumor cell lines (CLBL-1, GL-1, and UL-1). Treatment with olsalazine led to significant cell growth inhibition and increased the apoptotic rate in all three cell lines. Treatment with olsalazine reduced the total amount of 5-methylcytosine in genomic DNA, as assessed by enzyme-linked immunosorbent assay. Genome-wide analysis of DNA methylation revealed that 1,801 to 5,626 CpG sites showed decreased DNA methylation levels in three cell lines, including the promoter regions of ADAM23, FES, and CREB3L1 genes. The outcomes of the present study demonstrate that a DNA demethylating agent olsalazine, inhibits cell proliferation and DNA methylation in canine lymphoid tumor cells, suggesting that it can be a candidate drug for the treatment of lymphoid tumors in dogs.

Plasmonic layer-selective all-optical switching of magnetization with nanometer resolution.

All-optical magnetization reversal with femtosecond laser pulses facilitates the fastest and least dissipative magnetic recording, but writing magnetic bits with spatial resolution better than the wavelength of light has so far been seen as a major challenge. Here, we demonstrate that a single femtosecond laser pulse of wavelength 800 nm can be used to toggle the magnetization exclusively within one of two 10-nm thick magnetic nanolayers, separated by just 80 nm, without affecting the other one. The choice of the addressed layer is enabled by the excitation of a plasmon-polariton at a targeted interface of the nanostructure, and realized merely by rotating the polarization-axis of the linearly-polarized ultrashort optical pulse by 90°. Our results unveil a robust tool that can be deployed to reliably switch magnetization in targeted nanolayers of heterostructures, and paves the way to increasing the storage density of opto-magnetic recording by a factor of at least 2.

Spin-current-mediated rapid magnon localisation and coalescence after ultrafast optical pumping of ferrimagnetic alloys.

Sub-picosecond magnetisation manipulation via femtosecond optical pumping has attracted wide attention ever since its original discovery in 1996. However, the spatial evolution of the magnetisation is not yet well understood, in part due to the difficulty in experimentally probing such rapid dynamics. Here, we find evidence of a universal rapid magnetic order recovery in ferrimagnets with perpendicular magnetic anisotropy via nonlinear magnon processes. We identify magnon localisation and coalescence processes, whereby localised magnetic textures nucleate and subsequently interact and grow in accordance with a power law formalism. A hydrodynamic representation of the numerical simulations indicates that the appearance of noncollinear magnetisation via optical pumping establishes exchange-mediated spin currents with an equivalent 100% spin polarised charge current density of 107 A cm-2. Such large spin currents precipitate rapid recovery of magnetic order after optical pumping. The magnon processes discussed here provide new insights for the stabilization of desired meta-stable states.

Dynamic changes in DNA methylation patterns in canine lymphoma cell lines demonstrated by genome-wide quantitative DNA methylation analysis.

DNA methylation is the conversion of cytosine to 5-methylcytosine, leading to changes in the interactions between DNA and proteins. Methylation of cytosine-guanine (CpG) islands (CGIs) is associated with gene expression silencing of the involved promoter. Although studies focussing on global changes or a few single loci in DNA methylation have been performed in dogs with certain diseases, genome-wide analysis of DNA methylation is required to prospectively identify specific regions with DNA methylation change. The hypothesis of this study was that next-generation sequencing with methylation-specific signatures created by sequential digestion of genomic DNA with SmaI and XmaI enzymes can provide quantitative information on methylation levels. Using blood from healthy dogs and cells obtained from canine lymphoma cell lines, approximately 100,000CpG sites across the dog genome were analysed with the novel method established in this study. CpG sites in CGIs broadly were shown to be either methylated or unmethylated in normal blood, while CpG sites not within CpG islands (NCGIs) were largely methylated. Thousands of CpG sites in lymphoma cell lines were found to gain methylation at normally unmethylated CGI sites and lose methylation at normally methylated NCGI sites. These hypermethylated CpG sites are located at promoter regions of hundreds of genes, such as TWIST2 and TLX3. In addition, genes annotated with 'Homeobox' and 'DNA-binding' characteristics have hypermethylated CpG sites in their promoter CGIs. Genome-wide quantitative DNA methylation analysis is a sensitive method that is likely to be suitable for studies of DNA methylation changes in cancer, as well as other common diseases in dogs.

Ultrafast Magnetism of a Ferrimagnet across the Spin-Flop Transition in High Magnetic Fields.

We show that applying magnetic fields up to 30 T has a dramatic effect on the ultrafast spin dynamics in ferrimagnetic GdFeCo. Upon increasing the field beyond a critical value, the dynamics induced by a femtosecond laser excitation strongly increases in amplitude and slows down significantly. Such a change in spin response is explained by different dynamics of the Gd and FeCo magnetic sublattices following a spin-flop phase transition from a collinear to a noncollinear spin state.

Nanoscale sub-100 picosecond all-optical magnetization switching in GdFeCo microstructures.

Ultrafast magnetization reversal driven by femtosecond laser pulses has been shown to be a promising way to write information. Seeking to improve the recording density has raised intriguing fundamental questions about the feasibility of combining ultrafast temporal resolution with sub-wavelength spatial resolution for magnetic recording. Here we report on the experimental demonstration of nanoscale sub-100 ps all-optical magnetization switching, providing a path to sub-wavelength magnetic recording. Using computational methods, we reveal the feasibility of nanoscale magnetic switching even for an unfocused laser pulse. This effect is achieved by structuring the sample such that the laser pulse, via both refraction and interference, focuses onto a localized region of the structure, the position of which can be controlled by the structural design. Time-resolved photo-emission electron microscopy studies reveal that nanoscale magnetic switching employing such focusing can be pushed to the sub-100 ps regime.

Ultrafast time-resolved magneto-optical imaging of all-optical switching in GdFeCo with femtosecond time-resolution and a µm spatial-resolution.

We developed an ultrafast time-resolved magneto-optical (MO) imaging system with several millidegree resolution of light polarization angle, 100 fs time-resolution, and a micrometer spatial resolution. A CCD camera with about 10(6) pixels is used for detection and MO images with an absolute angle of the light polarization are acquired by the rotating analyzer method. By optimizing the analysis procedure with a least square method and the help of graphical processor units, this novel system significantly improves the speed for MO imaging, allowing to obtain a MO map of a sample within 15 s. To demonstrate the strength of the technique, we applied the method in a pump-and-probe experiment of all-optical switching in a GdFeCo sample in which we were able to detect temporal evolution of the MO images with sub-picosecond resolution.

Laser-induced magnetic nanostructures with tunable topological properties.

We report the creation and real-space observation of magnetic structures with well-defined topological properties and a lateral size as low as about 150 nm. They are generated in a thin ferrimagnetic film by ultrashort single optical laser pulses. Thanks to their topological properties, such structures can be classified as Skyrmions of a particular type that does not require an externally applied magnetic field for stabilization. Besides Skyrmions, we are able to generate magnetic features with topological characteristics that can be tuned by changing the laser fluence. The stability of such features is accounted for by an analytical model based on the interplay between the exchange and the magnetic dipole-dipole interactions.

Element-specific probing of ultrafast spin dynamics in multisublattice magnets with visible light.

We demonstrate the feasibility of element-specific probing of ultrafast spin dynamics in the multisublattice magnet TbFe in the visible spectral range. In particular, we show that one can selectively study the dynamics of Tb and Fe sublattices choosing the wavelength of light below and above 610 nm, respectively. We observe that, despite their antiferromagnetic coupling in the ground state, the Tb and Fe spins temporarily align ferromagnetically after excitation with an intense 55-fs laser pulse, after which they relax to their initial states due to the strong anisotropy in Tb.

Nanoscale spin reversal by non-local angular momentum transfer following ultrafast laser excitation in ferrimagnetic GdFeCo.

Ultrafast laser techniques have revealed extraordinary spin dynamics in magnetic materials that equilibrium descriptions of magnetism cannot explain. Particularly important for future applications is understanding non-equilibrium spin dynamics following laser excitation on the nanoscale, yet the limited spatial resolution of optical laser techniques has impeded such nanoscale studies. Here we present ultrafast diffraction experiments with an X-ray laser that probes the nanoscale spin dynamics following optical laser excitation in the ferrimagnetic alloy GdFeCo, which exhibits macroscopic all-optical switching. Our study reveals that GdFeCo displays nanoscale chemical and magnetic inhomogeneities that affect the spin dynamics. In particular, we observe Gd spin reversal in Gd-rich nanoregions within the first picosecond driven by the non-local transfer of angular momentum from larger adjacent Fe-rich nanoregions. These results suggest that a magnetic material's microstructure can be engineered to control transient laser-excited spins, potentially allowing faster (~ 1 ps) spin reversal than in present technologies.

Decreased immunoglobulin A concentrations in feces, duodenum, and peripheral blood mononuclear cells of dogs with inflammatory bowel disease.

BACKGROUND: Although immunoglobulin A (IgA) plays a key role in regulating gut homeostasis, its role in canine inflammatory bowel disease (IBD) is unknown. HYPOTHESIS: IgA expression may be altered in dogs with IBD, unlike that observed in healthy dogs and dogs with other gastrointestinal diseases. ANIMALS: Thirty-seven dogs with IBD, 10 dogs with intestinal lymphoma, and 20 healthy dogs. METHODS: Prospective study. IgA and IgG concentrations in serum, feces, and duodenal samples were measured by ELISA. IgA(+) cells in duodenal lamina propria and IgA(+) CD21(+) peripheral blood mononuclear cells (PBMCs) were examined by immunohistochemistry and flow cytometry, respectively. Duodenal expression of the IgA-inducing cytokine transforming growth factor ß (TGF-ß), B cell activating factor (BAFF), and a proliferation-inducing ligand (APRIL) was quantified by real-time RT-PCR. RESULTS: Compared to healthy dogs, dogs with IBD had significantly decreased concentrations of IgA in fecal and duodenal samples. The number of IgA(+) CD21(+) PBMCs and IgA(+) cells in duodenal lamina propria was significantly lower in dogs with IBD than in healthy dogs or dogs with intestinal lymphoma. Duodenal BAFF and APRIL mRNA expression was significantly higher in IBD dogs than in the healthy controls. Duodenal TGF-ß mRNA expression was significantly lower in dogs with IBD than in healthy dogs and dogs with intestinal lymphoma. CONCLUSIONS AND CLINICAL IMPORTANCE: IBD dogs have decreased IgA concentrations in feces and duodenum and fewer IgA(+) PBMCs, which might contribute to development of chronic enteritis in dogs with IBD.

Role of magnetic circular dichroism in all-optical magnetic recording.

Using magneto-optical microscopy in combination with ellipsometry measurements, we show that all-optical switching with polarized femtosecond laser pulses in ferrimagnetic GdFeCo is subjected to a threshold fluence absorbed in the magnetic layer, independent of either the excitation wavelength or the polarization of the laser pulse. Furthermore, we present a quantitative explanation of the intensity window in which all-optical helicity-dependent switching (AO-HDS) occurs, based on magnetic circular dichroism. This explanation is consistent with all the experimental findings on AO-HDS so far, varying from single- to multiple-shot experiments. The presented results give a solid understanding of the origin of AO-HDS, and give novel insights into the physics of ultrafast, laser controlled magnetism.

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.

Ultrasonographic evaluation of vincristine-induced gastric hypomotility and the prokinetic effect of mosapride in dogs.

BACKGROUND: Vincristine induces gastrointestinal motility disorders in humans. Adverse gastrointestinal events are commonly observed in dogs receiving vincristine. OBJECTIVES: To evaluate gastric motility after vincristine administration in dogs and the prophylactic effect of a prokinetic agent, mosapride. ANIMALS: Five healthy Beagle dogs. METHODS: Five dogs received vincristine i.v. at a dosage of 0.75 mg/m(2). The motility index (MI) of the antral contraction was ultrasonographically evaluated 30 minutes postfeeding before administration of vincristine and for 6 days after vincristine treatment. After a 6-week washout period, the dogs received vincristine with mosapride (2 mg/kg p.o., q24h for 6 days), and the MI was re-evaluated. Adverse gastrointestinal events were evaluated according to the Veterinary Co-operative Group Common Terminology Criteria for Adverse Events (VCOG-CTCAE). RESULTS: After vincristine administration, a significant decrease (P < .05) in MI was observed on days 3 (6.64 ± 0.30) and 4 (8.02 ± 0.94), compared with pretreatment levels (10.00 ± 0.62). Gastrointestinal adverse events were observed in 4 dogs (grade 2 decreased appetite: 3 dogs; grade 1 vomiting: 2 dogs; and grade 1 diarrhea and grade 2 hematochezia: 1 dog). When mosapride citrate was administered with vincristine and for the next 5 days, no decrease in MI was observed. Furthermore, adverse gastrointestinal events occurred less frequently (grade 1 vomiting and grade 2 hematochezia in 1 dog each). CONCLUSIONS AND CLINICAL IMPORTANCE: Vincristine (0.75 mg/m(2)) induces gastric hypomotility in dogs. Preventive administration of mosapride citrate (2.0 mg/kg p.o., q24h) improves hypomotility and may decrease the adverse gastrointestinal effects of vincristine.

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.

Gene expression of secretory carbonic anhydrase isozymes in striated ducts of canine salivary glands using laser microdissection system.

To clarify whether striated duct cells in canine salivary glands synthesize secretory carbonic anhydrase (CA-VI), as is the case with serous acinar cells, the present study utilized laser microdissection to harvest striated duct cells from canine parotid and submandibular glands, and total RNA extracted from these cells was then amplified by reverse transcription-polymerase chain reaction to assess CA-VI gene expression. The results confirmed the local expression of CA-VI mRNA in striated duct cells. This clarified that, in canine salivary glands, CA-VI is synthesized in not only serous acinar cells, but also striated duct cells.

Ultrafast interaction of the angular momentum of photons with spins in the metallic amorphous alloy GdFeCo.

Ultrashort laser pulses have been used to study the effect of circularly polarized light on spins in the ferrimagnetic metal GdFeCo. By turning the sample into a multidomain state and thereby suppressing the observation of the heating effect of light, we have been able to demonstrate an ultrafast nonthermal excitation of spin waves with a phase that depends on the angular momentum of the photons. These results demonstrate the possibility of ultrafast coherent control of the magnetization in this metallic system.