Response to “Comment on ‘Electrically injected spin-polarized vertical-cavity surface-emitting laser’ ” [Appl. Phys. Lett. 88, 056101 (2006)]

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/87776/2/056102_1.pd

Electrically injected spin-polarized vertical-cavity surface-emitting lasers

We report the design, fabrication, and characterization of an electrically injected, spin-polarized, vertical-cavity surface-emitting laser. We have demonstrated spin injection from the ferromagnetic semiconductor (Ga,Mn)As into In0.2Ga0.8As/GaAsIn0.2Ga0.8As∕GaAs quantum wells, spin transport across a distance of ∼ 0.25 μm∼0.25μm for temperatures ranging from 80 to 105 K80to105K, and spin detection through optical polarization measurements with coherent light emission. Controlled switching between right- and left-elliptically polarized modes is achieved with a maximum degree of circular polarization of 4.6% measured at 80 K80K.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/87839/2/091108_1.pd

Parental/caregiver influence on sexual risk behaviors among HIV-positive young people in Kinshasa, the Democratic Republic of the Congo

Young people make up more than 60% of the population in the Democratic Republic of the Congo (DRC) and have an HIV prevalence of over 1%. Parents/caregivers of HIV-positive young people play an important role in helping their children understand how their decisions affect their health and the health of others. The first aim of this research was to examine the relationships between parental/caregiver monitoring, social support, and sexual risk behaviors for young people living with HIV (YPLWH) in Kinshasa, DRC. Quantitative data collected from 103 YPLWH, age 14-24 and who reported ever having sex, were analyzed. The second aim was to describe the norms and patterns of communication about sex between parents/caregivers and their HIV-positive child through 52 semi-structured interviews of caregivers. In the first aim, the majority of participants reported low parental/caregiver monitoring (68%) and low social support (68%). Among all young people, 55 (53.4%) reported no sex in the past 12 months, 29 (28.2%) reported protected sex at last intercourse, and 19 (18.4%) reported unprotected sex at last intercourse. Social support was an effect modifier in the relationship between monitoring and sexual behavior, with marginal significance (OR = 1.7, 95%CI: 0.98-2.79). This interaction effect weakened when adjusted for time-since-HIV-diagnosis (OR=1.6, 95%CI: 0.91-2.75). In the second aim, reasons for communication about sex, including HIV disclosure and child attributes and content of communication, including sexual risk, HIV status disclosure and other risk behaviors, were identified. Reasons for communication were similar for parents/caregivers with children who knew their HIV status compared to those with children who did not know; however, most parents/caregivers waited until after puberty or until the child already started having sex to talk about sex. Parents/caregivers focused their conversations on the risks associated with sex, though males were told to be more careful compared to females, who were told to avoid sexual contact. For children who did not know their status, some parents/caregivers used scare tactics to influence their child's sexual behavior, even mentioning that they could contract HIV. These findings can inform culturally sensitive strategies for transmission risk interventions among young people living with HIV

Natural history of Arabidopsis thaliana and oomycete symbioses

Molecular ecology of plant–microbe interactions has immediate significance for filling a gap in knowledge between the laboratory discipline of molecular biology and the largely theoretical discipline of evolutionary ecology. Somewhere in between lies conservation biology, aimed at protection of habitats and the diversity of species housed within them. A seemingly insignificant wildflower called Arabidopsis thaliana has an important contribution to make in this endeavour. It has already transformed botanical research with deepening understanding of molecular processes within the species and across the Plant Kingdom; and has begun to revolutionize plant breeding by providing an invaluable catalogue of gene sequences that can be used to design the most precise molecular markers attainable for marker-assisted selection of valued traits. This review describes how A. thaliana and two of its natural biotrophic parasites could be seminal as a model for exploring the biogeography and molecular ecology of plant–microbe interactions, and specifically, for testing hypotheses proposed from the geographic mosaic theory of co-evolution

Mn-doped InAs self-organized diluted magnetic quantum-dot layers with Curie temperatures above 300 K300 K

The magnetic and structural properties of InAs:Mn self-organized diluted magnetic quantum dots grown by low-temperature (∼270 °C)(∼270 °C), solid-source molecular-beam epitaxy using a very low InAs growth rate (<0.1 ML∕s)(<0.1 ML∕s) are investigated. A Curie temperature (TC)(TC) of ∼350 K∼350 K is measured in a sample grown with a Mn∕InMn∕In flux ratio of 0.15. Electron energy-loss spectroscopy confirms that most of the Mn remains within the InAs quantum dots. We propose as a possible explanation for this high TCTC the effects of magnetic and structural disorder introduced by a random incorporation and inhomogeneous distribution of Mn atoms amongst the InAs quantum dots.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/69680/2/APPLAB-85-6-973-1.pd

A characterization of Schauder frames which are near-Schauder bases

A basic problem of interest in connection with the study of Schauder frames in Banach spaces is that of characterizing those Schauder frames which can essentially be regarded as Schauder bases. In this paper, we give a solution to this problem using the notion of the minimal-associated sequence spaces and the minimal-associated reconstruction operators for Schauder frames. We prove that a Schauder frame is a near-Schauder basis if and only if the kernel of the minimal-associated reconstruction operator contains no copy of $c_0$. In particular, a Schauder frame of a Banach space with no copy of $c_0$ is a near-Schauder basis if and only if the minimal-associated sequence space contains no copy of $c_0$. In these cases, the minimal-associated reconstruction operator has a finite dimensional kernel and the dimension of the kernel is exactly the excess of the near-Schauder basis. Using these results, we make related applications on Besselian frames and near-Riesz bases.Comment: 12 page

A new proof for the decidability of D0L ultimate periodicity

We give a new proof for the decidability of the D0L ultimate periodicity problem based on the decidability of p-periodicity of morphic words adapted to the approach of Harju and Linna.Comment: In Proceedings WORDS 2011, arXiv:1108.341

Combinatorics on words in information security: Unavoidable regularities in the construction of multicollision attacks on iterated hash functions

Classically in combinatorics on words one studies unavoidable regularities that appear in sufficiently long strings of symbols over a fixed size alphabet. In this paper we take another viewpoint and focus on combinatorial properties of long words in which the number of occurrences of any symbol is restritced by a fixed constant. We then demonstrate the connection of these properties to constructing multicollision attacks on so called generalized iterated hash functions.Comment: In Proceedings WORDS 2011, arXiv:1108.341