Spin-based quantum gating with semiconductor quantum dots by bichromatic radiation method

A potential scheme is proposed for realizing a two-qubit quantum gate in semiconductor quantum dots. Information is encoded in the spin degrees of freedom of one excess conduction electron of each quantum dot. We propose to use two lasers, radiation two neighboring QDs, and tuned to blue detuning with respect to the resonant frequencies of individual excitons. The two-qubit phase gate can be achieved by means of both Pauli-blocking effect and dipole-dipole coupling between intermediate excitonic states.Comment: Europhysics Letters 66 (2004) 1

Oophorectomy and hysterectomy may increase dementia risk but only when performed prematurely

Oophorectomy and hysterectomy may increase dementia risk but only when performed prematurel

Time outdoors and the prevention of myopia

Recent epidemiological evidence suggests that children who spend more time outdoors are less likely to be, or to become myopic, irrespective of how much near work they do, or whether their parents are myopic. It is currently uncertain if time outdoors also blocks progression of myopia. It has been suggested that the mechanism of the protective effect of time outdoors involves light-stimulated release of dopamine from the retina, since increased dopamine release appears to inhibit increased axial elongation, which is the structural basis of myopia. This hypothesis has been supported by animal experiments which have replicated the protective effects of bright light against the development of myopia under laboratory conditions, and have shown that the effect is, at least in part, mediated by dopamine, since the D2-dopamine antagonist spiperone reduces the protective effect. There are some inconsistencies in the evidence, most notably the limited inhibition by bright light under laboratory conditions of lens-induced myopia in monkeys, but other proposed mechanisms possibly associated with time outdoors such as relaxed accommodation, more uniform dioptric space, increased pupil constriction, exposure to UV light, changes in the spectral composition of visible light, or increased physical activity have little epidemiological or experimental support. Irrespective of the mechanisms involved, clinical trials are now underway to reduce the development of myopia in children by increasing the amount of time they spend outdoors. These trials would benefit from more precise definition of thresholds for protection in terms of intensity and duration of light exposures. These can be investigated in animal experiments in appropriate models, and can also be determined in epidemiological studies, although more precise measurement of exposures than those currently provided by questionnaires is desirable

Reproductive hormones as psychotropic agents?

The female preponderance in unipolar mood and anxiety disorders is well documented, with a double to triple lifetime prevalence compared to males. Much of this increased vulnerability is in the childbearing years. Hormones are a tempting explanation, although other biochemical factors such as cytokines may also be important. Psychosocial factors are clearly involved, including role issues.South African Psychiatry Review - May 200

剪断流における遷移と渦の対称性について

平面クエット流れにおける不安定平衡解は, 相空間における層流乱流境界上に存在することがあり,高レイノルズ数において層流乱流遷移における指標となる. 本研究では, 主流に対してスパン方向に鏡像対称性を有した対称性の高い平衡解が, 他の平衡解に比べ相空間において層流状態に近い位置に 存在することを示し, 層流乱流遷移の指標として有意であることを, 高レイノルズ数における解の漸 近的挙動から導く

Chronic exposure to KATP channel openers results in attenuated glucose sensing in hypothalamic GT1-7 neurons

Individuals with Type 1 diabetes (T1D) are often exposed to recurrent episodes of hypoglycaemia. This reduces hormonal and behavioural responses that normally counteract low glucose in order to maintain glucose homeostasis, with altered responsiveness of glucose sensing hypothalamic neurons implicated. Although the molecular mechanisms are unknown, pharmacological studies implicate hypothalamic ATP-sensitive potassium channel (KATP) activity, with KATP openers (KCOs) amplifying, through cell hyperpolarization, the response to hypoglycaemia. Although initial findings, using acute hypothalamic KCO delivery, in rats were promising, chronic exposure to the KCO NN414 worsened the responses to subsequent hypoglycaemic challenge. To investigate this further we used GT1-7 cells to explore how NN414 affected glucose-sensing behaviour, the metabolic response of cells to hypoglycaemia and KATP activity. GT1-7 cells exposed to 3 or 24 h NN414 exhibited an attenuated hyperpolarization to subsequent hypoglycaemic challenge or NN414, which correlated with diminished KATP activity. The reduced sensitivity to hypoglycaemia was apparent 24 h after NN414 removal, even though intrinsic KATP activity recovered. The NN414-modified glucose responsiveness was not associated with adaptations in glucose uptake, metabolism or oxidation. KATP inactivation by NN414 was prevented by the concurrent presence of tolbutamide, which maintains KATP closure. Single channel recordings indicate that NN414 alters KATP intrinsic gating inducing a stable closed or inactivated state. These data indicate that exposure of hypothalamic glucose sensing cells to chronic NN414 drives a sustained conformational change to KATP, probably by binding to SUR1, that results in loss of channel sensitivity to intrinsic metabolic factors such as MgADP and small molecule agonists.We thank Novo Nordisk for providing NN414. This study was funded by grants from Diabetes UK (to MLJA, RJM) and the Juvenile Diabetes Research Foundation (postdoctoral fellowship 3-576-2010 to CB and 1-2008-728 to RJM)

Does oral contraceptive-induced reduction in free testosterone adversely affect the sexuality and mood of women?

The aim of this study was to examine whether changes in plasma androgen levels (total testosterone (T), free testosterone (FT), and dehydro-epiandrosterone-sulfate (DHEA-S)) induced by oral contraceptive (OC) use were related to changes in sexual interest or response or in mood. Sixty-one women provided blood samples and were assessed, using interviews and standardized questionnaires, prior to starting, and after 3 months on OCs (Ortho-Tricyclen®, Ortho-Tricyclen-Lo®, or Ortho-Cyclen®, all containing the same progestagen, norgestimate). Significant decreases in T, FT, and DHEA-S were found after 3 months, although the extent of reduction was variable across women. There was some support for a relationship between the degree of reduction in total T and FT and the frequency of sexual thoughts after 3 months on OCs. However, some women had no loss of sexual interest in spite of substantial reduction in FT, and there was overall no evidence that reduction in FT affected enjoyment of sexual activity with a partner. The findings are consistent with the idea that some women may be more sensitive to changes in T than others. No relationship was found between negative mood, as assessed by the Beck Depression Inventory, and changes in T, FT, or DHEA-S

Contraccezione ormonale e sessualità: il counseling prima e durante la contraccezione

Il ruolo della contraccezione orale viene analizzato alla luce dei molti fattori che ne influenzano la scelta, la accettabilità e la soddisfazione d'uso, non solo generale ma specificamente sul piano sessuale. Le più alte incidenze della perdita della libido sono state riportate da studi spesso di natura retrospettiva incapaci però, a differenza degli studi prospettici, di separare gli aspetti fisiologici, correlati alla soppressione delle ovulazioni, dagli effetti farmacologici, dovuti all'azione specifica dell'etinilestradiolo e dei diversi progestinici. Paradossalmente, le donne che assumono il contraccettivo orale riportano, a dispetto di un calo della libido, una più alta frequenza coitale rispetto alle utilizzatrici di altri metodi contraccettivi, nonché un aumento della frequenza e dell'intensità degli orgasmi. Tuttavia gli effetti positivi della contraccezione orale sulla sessualità si realizzano in un sottogruppo di donne, quelle che riescono a separare la sessualità procreativa dalla sessualità finalizzata al piacere. Pertanto la conoscenza della sessualità dell'utente antecedente la prescrizione può consentire di formulare non solo previsioni sulla risposta comportamentale e del livello di gratificazione sessuale, bensì di diversificare la condotta del counseling da adottare con la donna e/o la coppia

The development of a scale of the Guttman Type for the assessment of mobility disability in multiple sclerosis

Objective: The aim of the study was to develop a valid and reliable unidimensional scale of the Guttman type for the assessment of mobility disability in multiple sclerosis (MS). Subjects: Sixty-eight subjects with a definite diagnosis of MS participated.They were attending as outpatients at a MS unit at a District General Hospital. Thirty had the primary progressive pattern of disease, and 38 had the relapsing-remitting pattern. Methods: Formal assessments used for neurological disability were inspected, and 14 test items of gross motor function were extracted and ordered according to two criteria. These were that actions progressed from lying, to sitting, to standing and walking tasks, and that they progressed from broader to narrower bases of support. All subjects carried out all test items which were scored as ‘pass’ or ‘fail’. Analysis: Data were tested for internal consistency, reliability, inter item correlation, reproducibility and scalability. On the basis of the results, the items were re-ordered in rank, and reduced to eleven tests. The eleven item scale was re-analysed. Results: Results showed that the scale had an internal consistency of 0.88 (alpha coefficient) and a coefficient of reproducibility (CR) of 0.95 and above for both MS subject groups. The coefficient of scalability (CS) for items was 0.78 for primary progressive subjects and 0.74 for the relapsing-remitting group. Reliability ranged from good (kappa = 0.49) for one item, to perfect for six items. Conclusion: The scale was demonstrated to be a hierarchical scale of the Guttman type exhibiting homogeneous unidimensionality and good reliability. The high CR indicated that scores may be summed, and the very acceptable levels of CS indicated that the cumulative scores are meaningful within the defined concept of hierarchy used in this study