The nonlinear Fano effect.

The Fano effect is ubiquitous in the spectroscopy of, for instance, atoms, bulk solids and semiconductor heterostructures. It arises when quantum interference takes place between two competing optical pathways, one connecting the energy ground state and an excited discrete state, the other connecting the ground state with a continuum of energy states. The nature of the interference changes rapidly as a function of energy, giving rise to characteristically asymmetric lineshapes. The Fano effect is particularly important in the interpretation of electronic transport and optical spectra in semiconductors. Whereas Fano's original theory applies to the linear regime at low power, at higher power a laser field strongly admixes the states and the physics becomes rich, leading, for example, to a remarkable interplay of coherent nonlinear transitions. Despite the general importance of Fano physics, this nonlinear regime has received very little attention experimentally, presumably because the classic autoionization processes, the original test-bed of Fano's ideas, occur in an inconvenient spectral region, the deep ultraviolet. Here we report experiments that access the nonlinear Fano regime by using semiconductor quantum dots, which allow both the continuum states to be engineered and the energies to be rescaled to the near infrared. We measure the absorption cross-section of a single quantum dot and discover clear Fano resonances that we can tune with the device design or even in situ with a voltage bias. In parallel, we develop a nonlinear theory applicable to solid-state systems with fast relaxation of carriers. In the nonlinear regime, the visibility of the Fano quantum interferences increases dramatically, affording a sensitive probe of continuum coupling. This could be a unique method to detect weak couplings of a two-level quantum system (qubits), which should ideally be decoupled from all other states.

Sex differences in verbal fluency during adolescence: a functional magnetic resonance imaging study in gender dysphoric and control boys and girls.

INTRODUCTION: In the literature, verbal fluency (VF) is generally described as a female-favoring task. Although it is conceivable that this sex difference only evolves during adolescence or adulthood under influence of sex steroids, this has never been investigated in young adolescents. AIM: First, to assess sex differences in VF performance and regional brain activation in adolescents. Second, to determine if untreated transsexual adolescents differ from their sex of birth with regard to VF performance and regional brain activation. METHOD: Twenty-five boys, 26 girls, 8 Male-to-Female transsexual adolescents (MtFs), and 14 Female-to-Male transsexual adolescents (FtMs) were tested in a cross-sectional study, while performing a phonetic and semantic VF task within an MRI scanner. MAIN OUTCOME MEASURES: Functional MRI response during VF task. RESULTS: Boys and girls produced similar amounts of words, but the group MtFs produced significantly more words in the phonetic condition compared to control boys, girls, and FtMs. During the semantic condition, no differences were found. With regard to brain activity, control boys showed more activation in the right Rolandic operculum, a small area adjacent to Broca's area, compared to girls. No significant differences in brain activity were found comparing transsexual adolescents, although sub-threshold activation was found in the right Rolandic operculum indicating a trendwise increase in activation from control girls to FtMs to MtFs to control boys. CONCLUSIONS: The better performance of MtFs is consistent with our expectation that MtFs perform better on female-favoring tasks. Moreover, they produced more words than girls and FtMs. Even though a trendwise linear increase in brain activity between the four groups only approached significance, it may indicate differences in individuals with gender identity disorder compared to their birth sex. Although our findings should thus be interpreted with caution, they suggest a biological basis for both transgender groups performing in-between the two sexes.

Glycogen synthase kinase 3beta missplicing contributes to leukemia stem cell generation.

Recent evidence suggests that a rare population of self-renewing cancer stem cells (CSC) is responsible for cancer progression and therapeutic resistance. Chronic myeloid leukemia (CML) represents an important paradigm for understanding the genetic and epigenetic events involved in CSC production. CML progresses from a chronic phase (CP) in hematopoietic stem cells (HSC) that harbor the BCR-ABL translocation, to blast crisis (BC), characterized by aberrant activation of beta-catenin within granulocyte-macrophage progenitors (GMP). A major barrier to predicting and inhibiting blast crisis transformation has been the identification of mechanisms driving beta-catenin activation. Here we show that BC CML myeloid progenitors, in particular GMP, serially transplant leukemia in immunocompromised mice and thus are enriched for leukemia stem cells (LSC). Notably, cDNA sequencing of Wnt/beta-catenin pathway regulatory genes, including adenomatous polyposis coli, GSK3beta, axin 1, beta-catenin, lymphoid enhancer factor-1, cyclin D1, and c-myc, revealed a novel in-frame splice deletion of the GSK3beta kinase domain in the GMP of BC samples that was not detectable by sequencing in blasts or normal progenitors. Moreover, BC CML progenitors with misspliced GSK3beta have enhanced beta-catenin expression as well as serial engraftment potential while reintroduction of full-length GSK3beta reduces both in vitro replating and leukemic engraftment. We propose that CP CML is initiated by BCR-ABL expression in an HSC clone but that progression to BC may include missplicing of GSK3beta in GMP LSC, enabling unphosphorylated beta-catenin to participate in LSC self-renewal. Missplicing of GSK3beta represents a unique mechanism for the emergence of BC CML LSC and might provide a novel diagnostic and therapeutic target.

Is Women's Tendency to Negotiate Safer Sex Another Opportunity for Intimate Partner Violence in Nigeria?

Husband's controlling and domineering attitudes have been shown to contribute to women's intimate partner violence experience in Nigeria. Some scholars have suggested that women's safer sex negotiation may create additional opportunity for incurring partner violence. The purpose of the current study was to test the possibility that married women's tendency to negotiate safer sex would contribute significant additional proportions of the variance in their experience of physical, sexual, and emotional violence. Using nationally representative data from a sample of married women in Nigeria (N = 19,360), three separate hierarchical regression analyses were performed to examine the contributions of husband's controlling and domineering attitudes and tendency to negotiate safer sex to the three types of violence experience. Regression analyses revealed that women whose husbands endorsed more controlling and domineering attitudes experienced more physical, sexual, and emotional violence. Furthermore, women with higher tendency to negotiate safer sex experienced more of all the forms of violence. After accounting for the influence of husband's controlling and domineering attitudes, regression analyses revealed that women's tendency to negotiate safer sex accounted for significant additional contributions of the variance in physical, sexual, and emotional violence experience. The additional contributions suggest that specific interventions may be needed for improving women's negotiation skills to reduce husband perpetrated violence risk.

Brain sexual differentiation and effects of cross-sex hormone therapy in transpeople: A resting-state functional magnetic resonance study.

OBJECTIVES: It is hypothesized that transpeople show sex-atypical differentiation of the brain. Various structural neuroimaging studies provide support for this notion, but little is known about the sexual differentiation of functional resting-state networks in transpeople. In this study we therefore aimed to determine whether brain functional connectivity (FC) patterns in transpeople are sex-typical or sex-atypical, before and after the start of cross-sex hormone therapy (CHT). METHODS: We acquired resting-state functional magnetic resonance data in 36 transpeople (22 with female sex assigned at birth), first during gonadal suppression, and again four months after start of CHT, and in 37 cisgender people (20 females), both sessions without any hormonal intervention. We used independent component analysis to identify the default mode network (DMN), salience network (SN), and left and right working memory network (WMN). These spatial maps were used for group comparisons. RESULTS: Within the DMN, SN, and left WMN similar FC patterns were found across groups. However, within the right WMN, cisgender males showed significantly greater FC in the right caudate nucleus than cisgender females. There was no such sex difference in FC among the transgender groups and they did not differ significantly from either of the cisgender groups. CHT (in transgender participants) and circulating sex steroids (in cisgender participants) did not affect FC. CONCLUSION: Our findings may suggest that cisgender males and females experience a dissimilar (early) differentiation of the right WMN and that such differentiation is less pronounced in transpeople.

Does polycystic ovary syndrome affect cognition? A functional magnetic resonance imaging study exploring working memory.

OBJECTIVE: To study effects of overexposure to androgens and subsequent antiandrogenic treatment on brain activity during working memory processes in women with polycystic ovary syndrome (PCOS). DESIGN: In this longitudinal study, working memory function was evaluated with the use of functional magnetic resonance imaging (MRI) in women with PCOS before and after antiandrogenic treatment. SETTING: Department of reproductive medicine, university medical center. PATIENT(S): Fourteen women with PCOS and with hyperandrogenism and 20 healthy control women without any features of PCOS or other hormonal disorders. INTERVENTION(S): Antiandrogenic hormone treatment. MAIN OUTCOME MEASURE(S): Functional MRI response during a working memory task. RESULT(S): At baseline women with PCOS showed more activation than the control group within the right superior parietal lobe and the inferior parietal lobe during task (all memory conditions). Task performance (speed and accuracy) did not differ between the groups. After antiandrogenic treatment the difference in overall brain activity between the groups disappeared and accuracy in the high memory load condition of the working memory task increased in women with PCOS. CONCLUSION(S): Women with PCOS may need additional neural resources during a working memory task compared with women without PCOS, suggesting less efficient executive functioning. This inefficiency may have effects on daily life functioning of women with PCOS. Antiandrogenic treatment appears to have a beneficial effect on this area of cognitive functioning. CLINICAL TRIAL REGISTRATION NUMBER: NTR2493.

Antimüllerian hormone levels decrease in female-to-male transsexuals using testosterone as cross-sex therapy.

OBJECTIVE: To investigate the effect of hormonal androgenic treatment on antimüllerian hormone (AMH) serum levels in female-to-male (FtM) transsexuals. Polycystic ovary syndrome (PCOS) is associated with elevated AMH levels. Some hypothesize that the high AMH level is a consequence of androgen-induced excessive development of small antral follicles. However, this role of androgens is not yet clear. DESIGN: Observational, prospective, cohort study. SETTING: Tertiary academic medical center. PATIENT(S): Twenty-two FtM transsexuals, healthy native females receiving cross-sex hormone therapy/androgenic treatment. INTERVENTION(S): Androgenic treatment with testosterone (T) and an aromatase inhibitor while endogenous hormone secretion was suppressed with the use of a GnRH agonist. MAIN OUTCOME MEASURE(S): Hormone concentrations were measured before and after androgenic treatment (administration of T and aromatase inhibitor). Measured hormones: AMH, inhibin B, T, androstenedione, DHEAS, E2, SHBG, LH, and FSH. RESULT(S): AMH concentrations were significantly lower after androgenic treatment (4.4 ± 4.4 µg/L vs. 1.4 ± 2.1 µg/L). Androgenic treatment resulted in a strong suppression of AMH secretion over a relative short period of 16 weeks. CONCLUSION(S): Our data underscore the likely important role of androgens in the dynamics of folliculogenesis. It challenges the idea that androgens induce high AMH levels, which is gaining more interest nowadays as an important particular PCOS feature. This strong decline furthermore indicates that AMH must be interpreted in the context of other reproductive endocrine conditions. CLINICAL TRIAL REGISTRATION NUMBER: NTR2493.