Do Teachers’ Race, Gender, and Ethnicity Matter? Evidence From the National Education Longitudinal Study of 1988

Using data from the National Educational Longitudinal Study of 1988 (NELS), the authors find that the match between teachers\u27 race, gender, and ethnicity and those of their students had little association with how much the students learned, but in several instances it seems to have been a significant determinant of teachers\u27 subjective evaluations of their students. For example, test scores of white female students in mathematics and science did not increase more rapidly when the teacher was a white woman than when the teacher was a white man, but white female teachers evaluated their white female students more highly than did white male teachers

Do Teachers' Race, Gender, and Ethnicity Matter?: Evidence from NELS88

Our study uses a unique national longitudinal survey, the National Educational Longitudinal Study of 1988 (NELS), which permits researchers to match individual students and teachers, to analyze issues relating to how a teacher's race, gender, and ethnicity, per se, influence students from both the same and different race, gender, and ethnic groups. In contrast to much of the previous literature, we focus both on how teachers subjectively relate to and evaluate their students and on objectively how much their students learn. On balance, we find that teachers' race, gender, and ethnicity, per se, are much more likely to influence teachers' subjective evaluations of their students than they are to influence how much the students objectively learn. For example, while white female teachers do not appear to be associated with larger increases in test scores for white female students in mathematics and science than white male teachers 'produce', white female teachers do have higher subjective evaluations than their white male counterparts of their white female students. We relate our findings to the more general literature on gender, race, and ethnic bias in subjective performance evaluations in the world of work and trace their implications for educational and labor markets.

Coulomb Blockade in an Open Quantum Dot

We report the observation of Coulomb blockade in a quantum dot contacted by two quantum point contacts each with a single fully-transmitting mode, a system previously thought to be well described without invoking Coulomb interactions. At temperatures below 50 mK we observe a periodic oscillation in the conductance of the dot with gate voltage that corresponds to a residual quantization of charge. From the temperature and magnetic field dependence, we infer the oscillations are Mesoscopic Coulomb Blockade, a type of Coulomb blockade caused by electron interference in an otherwise open system.Comment: Text and supplementary information. Text: 4 pages, 4 figures. Supplementary information: 4 pages, 4 figure

A Preliminary Indication of Evolution of Type Ia Supernovae from their Risetimes

We have compared the risetime for samples of nearby and high-redshift type Ia supernovae (SNe Ia). The fiducial risetime of the nearby SNe Ia is 2.5+/-0.4 days longer than the proemial risetime determined by Goldhaber (1998a,b) for high-redshift SNe Ia from the Supernova Cosmology Project. The statistical likelihood that the two samples have different fiducial risetimes is high (5.8 sigma) and indicates possible evolution between the samples of SNe Ia. We consider the likely effects of several sources of systematic error, but none of these resolves the difference in the risetimes. Currently, we cannot directly determine the impact of the apparent evolution on previous determinations of cosmological parameters.Comment: Accepted by the Astronomical Journal, 11 pages, 5 figure

Heavy Meson Physics: What have we learned in Twenty Years?

I give a personal account of the development of the field of heavy quarks. After reviewing the experimental discovery of charm and bottom quarks, I describe how the field's focus shifted towards determination of CKM elements and how this has matured into a precision science.Comment: This talk was presented during the ceremony awarding the Medalla 2003 of the Division of Particles and Fields of The Mexican Phsyical Society, at the IX Mexican Workshop on Particles and Fields; submitted for proceedings; 9 pages, 9 figures; replacement: fix multiple typo

Singlet-triplet transition in a single-electron transistor at zero magnetic field

We report sharp peaks in the differential conductance of a single-electron transistor (SET) at low temperature, for gate voltages at which charge fluctuations are suppressed. For odd numbers of electrons we observe the expected Kondo peak at zero bias. For even numbers of electrons we generally observe Kondo-like features corresponding to excited states. For the latter, the excitation energy often decreases with gate voltage until a new zero-bias Kondo peak results. We ascribe this behavior to a singlet-triplet transition in zero magnetic field driven by the change of shape of the potential that confines the electrons in the SET.Comment: 4 p., 4 fig., 5 new ref. Rewrote 1st paragr. on p. 4. Revised author list. More detailed fit results on page 3. A plotting error in the horizontal axis of Fig. 1b and 3 was corrected, and so were the numbers in the text read from those fig. Fig. 4 was modified with a better temperature calibration (changes are a few percent). The inset of this fig. was removed as it is unnecessary here. Added remarks in the conclusion. Typos are correcte

Conductance through an array of quantum dots

We propose a simple approach to study the conductance through an array of $N$ interacting quantum dots, weakly coupled to metallic leads. Using a mapping to an effective site which describes the low-lying excitations and a slave-boson representation in the saddle-point approximation, we calculated the conductance through the system. Explicit results are presented for N=1 and N=3: a linear array and an isosceles triangle. For N=1 in the Kondo limit, the results are in very good agreement with previous results obtained with numerical renormalization group (NRG). In the case of the linear trimer for odd $N$, when the parameters are such that electron-hole symmetry is induced, we obtain perfect conductance $G_0=2e^2/h$. The validity of the approach is discussed in detail.Comment: to appear in Phys. Rev.