Spin-polarized electric currents in diluted magnetic semiconductor heterostructures induced by terahertz and microwave radiation

We report on the study of spin-polarized electric currents in diluted magnetic semiconductor (DMS) quantum wells subjected to an in-plane external magnetic field and illuminated by microwave or terahertz radiation. The effect is studied in (Cd,Mn)Te/(Cd,Mg)Te quantum wells (QWs) and (In,Ga)As/InAlAs:Mn QWs belonging to the well known II-VI and III-V DMS material systems, as well as, in heterovalent AlSb/InAs/(Zn,Mn)Te QWs which represent a promising combination of II-VI and III-V semiconductors. Experimental data and developed theory demonstrate that the photocurrent originates from a spin-dependent scattering of free carriers by static defects or phonons in the Drude absorption of radiation and subsequent relaxation of carriers. We show that in DMS structures the efficiency of the current generation is drastically enhanced compared to non-magnetic semiconductors. The enhancement is caused by the exchange interaction of carrier spins with localized spins of magnetic ions resulting, on the one hand, in the giant Zeeman spin-splitting, and, on the other hand, in the spin-dependent carrier scattering by localized Mn2+ ions polarized by an external magnetic field.Comment: 14 pages, 13 figure

Challenges to the development of antigen-specific breast cancer vaccines

Continued progress in the development of antigen-specific breast cancer vaccines depends on the identification of appropriate target antigens, the establishment of effective immunization strategies, and the ability to circumvent immune escape mechanisms. Methods such as T cell epitope cloning and serological expression cloning (SEREX) have led to the identification of a number target antigens expressed in breast cancer. Improved immunization strategies, such as using dendritic cells to present tumor-associated antigens to T lymphocytes, have been shown to induce antigen-specific T cell responses in vivo and, in some cases, objective clinical responses. An outcome of successful tumor immunity is the evolution of antigen-loss tumor variants. The development of a polyvalent breast cancer vaccine, directed against a panel of tumor-associated antigens, may counteract this form of immune escape

Fundamental Curie temperature limit in ferromagnetic Ga1-xMnxAs

We provide unambiguous experimental evidence that the upper limit of {approx}110 K commonly observed for the Curie temperature TC of Ga{sub 1-x}Mn{sub x}As is caused by the Fermi-level-induced hole saturation. This conclusion is based on parallel studies of the location of Mn in the lattice, the effectiveness of acceptor center, and ferromagnetism on a series of Ga{sub 1-x-y}Mn{sub x}Be{sub y}As layers, in which the concentration of magnetic moments and of free holes can be independently controlled by the Mn and Be contents. Ion channeling and magnetization measurements show a dramatic increase of the concentration of Mn interstitials accompanied by a reduction of T{sub C} with increasing Be concentration. At the same time the free hole concentration remains relatively constant at {approx}5 x 10{sup 20}cm{sup -3}. These results indicate that the concentrations of free holes as well as of ferromagnetically active Mn spins are governed by the position of the Fermi level, which controls the formation energy of compensating interstitial Mn donors. Based on these results, we propose to use heavy n-type counter-doping of Ga{sub 1-x}Mn{sub x}As (by, e.g., Te) to suppress the formation of Mn interstitials at high x, and thus improve the T{sub C} of the alloy system

Fundamental Curie temperature limit in ferromagnetic GaMnAs

We provide experimental evidence that the upper limit of ~110 K commonly observed for the Curie temperature T_C of Ga(1-x)Mn(x)As is caused by the Fermi-level-induced hole saturation. Ion channeling, electrical and magnetization measurements on a series of Ga(1-x-y)Mn(x)Be(y)As layers show a dramatic increase of the concentration of Mn interstitials accompanied by a reduction of T_C with increasing Be concentration, while the free hole concentration remains relatively constant at ~5x10^20 cm^-3. These results indicate that the concentrations of free holes and ferromagnetically active Mn spins are governed by the position of the Fermi level, which controls the formation energy of compensating interstitial Mn donors.Comment: 14 pages, 3 figure

Hysteretic magnetoresistance and thermal bistability in a magnetic two-dimensional hole system

Colossal negative magnetoresistance and the associated field-induced insulator-to-metal transition, the most characteristic features of magnetic semiconductors, are observed in n-type rare earth oxides and chalcogenides, p-type manganites, n-type and p-type diluted magnetic semiconductors (DMS) as well as in quantum wells of n-type DMS. Here, we report on magnetostransport studies of Mn modulation-doped InAs quantum wells, which reveal a magnetic field driven and bias voltage dependent insulator-to-metal transition with abrupt and hysteretic changes of resistance over several orders of magnitude. These phenomena coexist with the quantised Hall effect in high magnetic fields. We show that the exchange coupling between a hole and the parent Mn acceptor produces a magnetic anisotropy barrier that shifts the spin relaxation time of the bound hole to a 100 s range in compressively strained quantum wells. This bistability of the individual Mn acceptors explains the hysteretic behaviour while opening prospects for information storing and processing. At high bias voltage another bistability, caused by the overheating of electrons10, gives rise to abrupt resistance jumps

Laryngeal embryonal rhabdomyosarcoma in an adult - A case presentation in the eyes of geneticists and clinicians

<p>1. Abstract</p> <p>Background</p> <p>Rhabdomyosarcoma is a solid tumor, resulting from dysregulation of the skeletal myogenesis program. For rhabdomyosarcomas (RMS) with a predilection for the head and neck, genitourinary tract, extremities, trunk, retroperitoneum, the larynx is still an unusual site. Till now only several cases of this laryngeal tumor have been described in world literature in the adult population. The entire spectrum of genetic factors underlying RMS development and progression is unclear until today. Multiple signaling pathways seem to be involved in ERMS development and progression.</p> <p>Case presentation</p> <p>In this paper we report an interesting RMS case in which the disease was located within the glottic region. We report an embryonal rhabdomyosarcoma of the larynx in 33 year-old man. After unsuccessful chemotherapy hemilaryngectomy was performed. In follow up CT no signs of recurrence were found. Recently patient is recurrence free for 62 months.</p> <p>Conclusions</p> <p>Considering the histological diagnosis and the highly aggressive nature of the lesion for optimal diagnosis positron electron tomography (PET) and computerized tomography (CT) of the neck and thorax should be performed. At this time surgical treatment with adjuvant radiotherapy seems to be the treatment of choice for this disease. Rhabdomyosarcoma of the larynx has a better prognosis than elsewhere in the body, probably because of its earlier recognition and accessibility to radical surgery.</p

Help-seeking behaviour for pelvic floor dysfunction in women over 55: drivers and barriers

Objective: Our aim was to identify drivers of and barriers to help-seeking behaviour of older women with pelvic floor dysfunction (PFD) living independently in Australia . Methods: Women aged =55 years were recruited to this cross-sectional study during July and August 2016. Bladder, bowel, pelvic organ prolapse (POP) and sexual dysfunction were assessed with the Australian Pelvic Floor Questionnaire (APFQ). Drivers and barriers were based on the Barriers to Incontinence Care Seeking Questionnaire. Univariate analyses were used to assess any significant relationships between PFD, age, education level, self-reported PFD, barriers and drivers. Results: Of the 376 study participants [mean, standard deviation (SD) age 68.6 (10.5) years], 67% reported symptoms of PFD and 98.7% scored &gt; 0 on the APFQ. Women were more likely to seek help if they scored higher on the APFQ (p &lt; 0.001). The main barrier to seeking help was the perception that PFD was a normal part of ageing (22.4%). Of those who did seek help (50%), the main factor was increased level of symptom bother (51.4%). There was no difference in age or education level between women who did and did not seek help. Conclusion: Women are more likely to seek help for PFD if scoring higher on the APFQ or symptoms are becoming more bothersome. They are less likely to seek help if they view their symptoms as normal. Future direction should be taken to raise awareness of normal pelvic floor function as well as the availability of help for PFD

Experimental probing of the interplay between ferromagnetism and localisation in (Ga,Mn)As

The question whether the Anderson-Mott localisation enhances or reduces magnetic correlations is central to the physics of magnetic alloys. Particularly intriguing is the case of (Ga,Mn)As and related magnetic semiconductors, for which diverging theoretical scenarios have been proposed. Here, by direct magnetisation measurements we demonstrate how magnetism evolves when the density of carriers mediating the spin-spin coupling is diminished by the gate electric field in metal/insulator/semiconductor structures of (Ga,Mn)As. Our findings show that the channel depletion results in a monotonic decrease of the Curie temperature, with no evidence for the maximum expected within the impurity-band models. We find that the transition from the ferromagnetic to the paramagnetic state proceeds via the emergence of a superparamagnetic-like spin arrangement. This implies that carrier localisation leads to a phase separation into ferromagnetic and nonmagnetic regions, which we attribute to critical fluctuations in the local density of states, specific to the Anderson-Mott quantum transition.Comment: 8 pages, 3 figure