Static and dynamic properties of Single-Chain Magnets with sharp and broad domain walls

We discuss time-quantified Monte-Carlo simulations on classical spin chains with uniaxial anisotropy in relation to static calculations. Depending on the thickness of domain walls, controlled by the relative strength of the exchange and magnetic anisotropy energy, we found two distinct regimes in which both the static and dynamic behavior are different. For broad domain walls, the interplay between localized excitations and spin waves turns out to be crucial at finite temperature. As a consequence, a different protocol should be followed in the experimental characterization of slow-relaxing spin chains with broad domain walls with respect to the usual Ising limit.Comment: 18 pages, 13 figures, to be published in Phys. Rev.

Topoisomerase II beta mediates the resistance of glioblastoma stem cells to replication stress-inducing drugs

Background: Glioblastoma stem cells (GSC) have been extensively recognized as a plausible cause of glioblastoma resistance to therapy and recurrence resulting in high glioblastoma mortality. Abnormalities in the DNA repair pathways might be responsible for the inability of the currently used chemotherapeutics to eliminate the (GSC) subpopulation. Methods: In this work, we compared the expression of sixty DNA repair related genes between primary glioblastoma cell cultures and the glioblastoma enriched stem cell primary cultures. MTT test was used to analyze the effect of selected drugs and immunofluorescence to evaluate the load of DNA damage. Results: We found several differentially expressed genes and we identified topoisomerase II beta (Top2 beta) as the gene with highest up-regulation in GSC. Also among the tested cell lines the expression of Top2 beta was the highest in NCH421k cells, a well-characterized glioblastoma cell line with all the stemness characteristics. On the other hand, Top2 beta expression markedly decreased upon the induction of differentiation by all trans-retinoic acid. Depletion of Top2 beta increased the sensitivity of NCH421k cells to replication stress inducing drugs, such as cisplatin, methyl-methanesulfonate, hydrogen peroxide, and temozolomide. Consistently, we found an increased load of DNA damage and increased Chk1 activation upon Top2 beta depletion in NCH421k cells. Conclusion: We suggest that Top2 beta may represent a new target for gene therapy in glioblastoma. In addition, the other genes that we found to be up-regulated in GSC versus glioblastoma primary cells should be further investigated as glioblastoma theranostics

One-dimensional Ising ferromagnet frustrated by long-range interactions at finite temperatures

We consider a one-dimensional lattice of Ising-type variables where the ferromagnetic exchange interaction J between neighboring sites is frustrated by a long-ranged anti-ferromagnetic interaction of strength g between the sites i and j, decaying as |i-j|^-alpha, with alpha>1. For alpha smaller than a certain threshold alpha_0, which is larger than 2 and depends on the ratio J/g, the ground state consists of an ordered sequence of segments with equal length and alternating magnetization. The width of the segments depends on both alpha and the ratio J/g. Our Monte Carlo study shows that the on-site magnetization vanishes at finite temperatures and finds no indication of any phase transition. Yet, the modulation present in the ground state is recovered at finite temperatures in the two-point correlation function, which oscillates in space with a characteristic spatial period: The latter depends on alpha and J/g and decreases smoothly from the ground-state value as the temperature is increased. Such an oscillation of the correlation function is exponentially damped over a characteristic spatial scale, the correlation length, which asymptotically diverges roughly as the inverse of the temperature as T=0 is approached. This suggests that the long-range interaction causes the Ising chain to fall into a universality class consistent with an underlying continuous symmetry. The e^(Delta/T)-temperature dependence of the correlation length and the uniform ferromagnetic ground state, characteristic of the g=0 discrete Ising symmetry, are recovered for alpha > alpha_0.Comment: 12 pages, 7 figure

Critical exponents and scaling invariance in the absence of a critical point

The paramagnetic-to-ferromagnetic phase transition is believed to proceed through a critical point, at which power laws and scaling invariance, associated with the existence of one diverging characteristic length scale -- the so called correlation length -- appear. We indeed observe power laws and scaling behavior over extraordinarily many decades of the suitable scaling variables at the paramagnetic-to-ferromagnetic phase transition in ultrathin Fe films. However, we find that, when the putative critical point is approached, the singular behavior of thermodynamic quantities transforms into an analytic one: the critical point does not exist, it is replaced by a more complex phase involving domains of opposite magnetization, below as well as $above$ the putative critical temperature. All essential experimental results are reproduced by Monte-Carlo simulations in which, alongside the familiar exchange coupling, the competing dipole-dipole interaction is taken into account. Our results imply that a scaling behavior of macroscopic thermodynamic quantities is not necessarily a signature for an underlying second-order phase transition and that the paramagnetic-to-ferromagnetic phase transition proceeds, very likely, in the presence of at least two long spatial scales: the correlation length and the size of magnetic domains.Comment: 10 pages, added figure 1, rearranged section

Chiropractic treatment of older adults with neck pain with or without headache or dizziness: Analysis of 288 Australian chiropractors' self-reported views

© 2019 The Author(s). Background: Neck pain is a leading cause of individual and societal burden worldwide, affecting an estimated 1 in 5 people aged 70 years and older. The nature and outcomes of chiropractic care for older adults with neck pain, particularly those with co-morbid headaches, remains poorly understood. Therefore, we sought to ascertain: What proportion of Australian chiropractors' caseload comprises older adults with neck pain (with or without headache); How are these conditions treated; What are the reported outcomes? Methods: An online survey examining practitioner and practice characteristics, clinical patient presentations, chiropractic treatment methods and outcomes, and other health service use, was distributed to a random nationally representative sample of 800 Australian chiropractors. Quantitative methods were used to analyze the data. Results: Two hundred eighty-eight chiropractors (response rate = 36%) completed the survey between August and November 2017. Approximately one-third (M 28.5%, SD 14.2) of the chiropractors' patients were older adults (i.e. aged ≥65 years), of which 45.5% (SD 20.6) presented with neck pain and 31.3% (SD 20.3) had co-morbid headache. Chiropractors reported to combine a range of physical and manual therapy treatments, exercises and self-management practices in their care of these patients particularly: manipulation of the thoracic spine (82.0%); activator adjustment of the neck (77.3%); and massage of the neck (76.5%). The average number of visits required to resolve headache symptoms was reported to be highest among those with migraine (M 11.2, SD 8.8). The majority of chiropractors (57.3%) reported a moderate response to treatment in reported dizziness amongst older adults with neck pain. Approximately 82% of older adult patients were estimated to use at least one other health service concurrently to chiropractic care to manage their neck pain. Conclusion: This is the first known study to investigate chiropractic care of older adults living with neck pain. Chiropractors report using well-established conservative techniques to manage neck pain in older adults. Our findings also indicate that this target group of patients may frequently integrate chiropractic care with other health services in order to manage their neck pain. Further research should provide in-depth investigation of older patients' experience and other patient-reported outcomes of chiropractic treatment

Glauber slow dynamics of the magnetization in a molecular Ising chain

The slow dynamics (10^-6 s - 10^4 s) of the magnetization in the paramagnetic phase, predicted by Glauber for 1d Ising ferromagnets, has been observed with ac susceptibility and SQUID magnetometry measurements in a molecular chain comprising alternating Co{2+} spins and organic radical spins strongly antiferromagnetically coupled. An Arrhenius behavior with activation energy Delta=152 K has been observed for ten decades of relaxation time and found to be consistent with the Glauber model. We have extended this model to take into account the ferrimagnetic nature of the chain as well as its helicoidal structure.Comment: 4 pages, 4 figures (low resolution), 16 references. Submitted to Physical Review Letter

Somatic mutations and deletions of the E-cadherin gene predict poor survival of patients with gastric cancer.

Purpose The prognosis of gastric cancer (GC) is poor, and the molecular pathogenesis players are vastly unknown. Surgery remains the primary option in GC treatment. The aim of this study was to investigate the impact of somatic CDH1 alterations in prognosis and survival of patients with GC. Patients and Methods A series of patients with sporadic and familial GC (diffuse and intestinal; n _ 246) were analyzed for somatic CDH1 mutations, promoter hypermethylation, and loss of heterozygosity (LOH) by polymerase chain reaction sequencing. E-cadherin protein expression was determined by immunohistochemistry. Associations between molecular, clinicopathologic, and survival data were analyzed. Results CDH1 somatic alterations were found in approximately 30% of all patients with GC. Both histologic types of sporadic GC displayed LOH in 7.5%, mutations in 1.7%, and hypermethylation in 18.4% of patients. Primary tumors from hereditary diffuse GC, lacking germline CDH1 alterations, showed exclusively CDH1 promoter hypermethylation in 50% of patients. Familial intestinal GC (FIGC) tumors showed LOH in 9.4% and hypermethylation in 17.0%. CDH1 alterations did not associate with a particular pattern of E-cadherin expression. Importantly, the worst patient survival rate among all GCs analyzed was seen in patients with tumors carrying CDH1 structural alterations, preferentially those belonging to FIGC families. Conclusion CDH1 somatic alterations exist in all clinical settings and histotypes of GC and associate with different survival rates. Their screening at GC diagnosis may predict patient prognosis and is likely to improve management of patients with this disease.Supported by the Portuguese Foundation for Science and Technology (Projects No. POCTI/SAUOBS/58111/2004, PIC/IC/82923/2007, PTDC/SAU-GMG/72168/2006, PTDC/SAUGMG/110785/2009, and PTDC/SAU-ONC/110294/2009; PhD Grants No. SFRH/BD/40090/2007-GC and SFRH/BD/44074/2008-JC); salary support to C.O. from POPHQREN/Type 4.2; European Social Fund and Portuguese Ministry of Science and Technology; European Molecular Biology Organization short-term fellowship (ASTF 338.00-2008-JC); Calouste Gulbenkian Foundation short-term fellowship (nr 92352-JC); and Istituto Toscano Tumori (Grant No. ITT-2007). IPATIMUP is an Associate Laboratory of the Portuguese Ministry of Science, Technology, and Higher Education and is partially supported by the Portuguese Foundation for Science and Technology