Tuan Nguyen

The College of New Jersey | TCNJ · Department of Physics

The transynaptic and retrograde spread of rabies virus make it an efficient and robust transneuronal tracer, capable of revealing connectivity patterns of multisynaptic, neuronal circuits with great detail. Current techniques begin by infecting many neurons simultaneously, from which higher-order neurons are then labeled sequentially in time. Here...

The acoustic startle response (ASR) is a reflexive contraction of skeletal muscles in response to a loud, abrupt acoustic stimulus. ASR magnitude is reduced if the startle stimulus is preceded by a weaker acoustic or non-acoustic stimulus, a phenomenon known as prepulse inhibition (PPI). PPI has been used to test various aspects of sensory discrimi...

We describe an ultraviolet (uv) diode laser system for cooling trapped Yb(+) ions. Using four stages of thermoelectric cooling, 10 mW of light at 369.5 nm is obtained by cooling a 373.4-nm uv diode to approximately -20 degrees C. Frequency stabilization is provided by a diffraction grating mounted in the Littrow configuration which allows for a mod...

Over 8 months, we monitored transition frequencies between nearly degenerate, opposite-parity levels in two isotopes of atomic dysprosium (Dy). These frequencies are sensitive to variation of the fine-structure constant (alpha) due to relativistic corrections of opposite sign for the opposite-parity levels. In this unique system, in contrast to ato...

A technique combining fluorescence imaging with Ca²⁺ indicators and single-cell laser scanning photostimulation of caged glutamate (LSPS) allows identification of functional connections between individual neurons in mixed cultures of rat neocortical cells as well as observation of synchronous spontaneous activity among neurons. LSPS performed on la...

A technique combining fluorescence imaging with Ca ²⁺ indicators and single-cell laser scanning photostimulation of caged glutamate (LSPS) allows identification of functional connections between individual neurons in mixed cultures of rat neocortical cells as well as observation of synchronous spontaneous activity among neurons. LSPS performed on l...

Hearing loss leads to a host of cellular and synaptic changes in auditory brain areas that are thought to give rise to auditory perception deficits such as temporal processing impairments, hyperacusis, and tinnitus. However, little is known about possible changes in synaptic circuit connectivity that may underlie these hearing deficits. Here, we sh...

Using single-cell laser scanning photostimulation (LSPS) combined with broad-field calcium imaging, we measured the functional connectivity of neuronal cultures before and after the developmental appearance of network bursting. From these data, network properties were determined for these relatively large neuronal networks. Based on these propertie...

Photostimulation of neurons with caged glutamate is a viable tool for mapping the strength and spatial distribution of synaptic networks in living brain slices. In photostimulation experiments, synaptic connectivity is assessed by eliciting action potentials in putative presynaptic neurons via focal photolysis of caged glutamate, while measuring po...

The inferior colliculus (IC) in the mammalian midbrain is the major subcortical auditory integration center receiving ascending inputs from almost all auditory brainstem nuclei as well as descending inputs from the thalamus and cortex. In addition to these extrinsic inputs, the IC also contains a dense network of local, intracollicular connections,...

This article describes the assembly and performance of a simple and inexpensive ultraviolet-flash system suitable for rapid focal photolysis of caged compounds in cultured neurons and brain slices. Advantages and limitations of this system are discussed. Examples are provided illustrating how this system can be used for stimulating neurons and mapp...

Long-lived metastable states of Yb + ions are used for atomic frequency standards, precision measurements, and quantum information research. The effect of population trapping and transfer in these states must be well understood. We report here the transfer of Yb + ions into the long-lived 2 F 7/2 state by means of collisions between He buffer gas a...

Radio-frequency electric-dipole transitions between nearly degenerate, opposite parity levels of atomic dysprosium (Dy) were monitored over an eight-month period to search for a variation in the fine-structure constant, α. The data provide a rate of fractional temporal variation of α of (−2.4±2.3)×10 −15 yr −1 or a value of (−7.8 ± 5.9) × 10 −6 for...

Electric-dipole transitions between nearly degenerate, opposite parity levels of atomic dysprosium (Dy) were monitored overan eight-month period to search for a variation in thefine-structure constant, α. The frequencies of thesetransitions are sensitive to variation of α due to largerelativistic corrections of opposite sign for the opposite-parity...

Radio-frequency E1 transitions between nearly degenerate, opposite parity levels of atomic dysprosium were monitored over an eight month period to search for a variation in the fine-structure constant. During this time period, data were taken at different points in the gravitational potential of the Sun. The data are fitted to the variation in the...

We have studied collisional perturbations of radio-frequency (rf) electric-dipole (E1) transitions between the nearly degenerate opposite-parity levels in atomic dysprosium (Dy) in the presence of 10 to 80 $\mu$Torr of H$_\text{2}$, N$_\text{2}$, He, Ar, Ne, Kr, and Xe. Collisional broadening and shift of the resonance, as well as the attenuation o...

It has been proposed that the radio-frequency electric-dipole (E1) transition between two nearly degenerate opposite-parity states in atomic dysprosium should be highly sensitive to possible temporal variation of the fine structure constant ($\alpha$) [V. A. Dzuba, V. V. Flambaum, and J. K. Webb, Phys. Rev. A {\bf 59}, 230 (1999)]. We analyze here...

Magneto-optical (Faraday) rotation is a process in which the plane of light polarization rotates as light propagates through a medium along the direction of a magnetic field. In atomic vapors where ground state atomic polarization relaxes very slowly (relaxation rates < 1 Hz), there arise ultranarrow, light-power-dependent (nonlinear) features in t...

Recent and ongoing experiments testing various fundamental discrete symmetries are discussed, including search for parity nonconservation in dysprosium and ytterbium, investigation of possibilities of searches for parity and time-reversal invariance violation in samarium, and a test of permutation properties of photons in a two-photon transition in...

We investigate a three-step population scheme to efficiently transfer atoms to a particular metastable state of atomic dysprosium, and present evidence of adiabatic passage in the first step. This scheme will be employed in an ongoing search for parity nonconservation (PNC) in dysprosium. In order to excite a large fraction of the transverse veloci...

We are preparing a new experiment searching for parity nonconservation (PNC) using the nearly degenerate excited states in atomic dysprosium (Dy)(A. T. Nguyen, D. Budker, D. DeMille, and M. Zolotorev, Search for parity nonconservation in atomic dysprosium. Phys. Rev. A 56(5), 3453-63 (1997).). Like in the earlier experiment^1, a loosely collimated...

Results of a search for parity nonconservation (PNC) in a pair of nearly degenerate opposite-parity states in atomic dysprosium are reported. The sensitivity to PNC mixing is enhanced in this system by the small energy separation between these levels, which can be crossed by applying an external magnetic field. The metastable odd-parity sublevel of...

We are preparing a pulsed-laser atomic beam experiment in which we will measure radiative lifetimes and electric polarizabilities of low-lying energy levels in atomic samarium. For the polarizability measurements, the Stark quantum beat technique will be used. In addition, the experimental apparatus will be used to search for the 4f^66s^2 5D_0,4 st...

Lifetimes of 21 excited states in atomic Yb were measured using time-resolved fluorescence detection following pulsed laser excitation. The lifetime of the 4f{sup 14}5d6s {sup 3}D{sub 1} state, which is of particular importance for a proposed study of parity nonconservation in atoms, was measured to be 380(30) ns.

Lifetimes of 21 excited states in atomic Yb were measured using time-resolved fluorescence detection following pulsed laser excitation. The lifetime of the 4f 145d6s 3D1 state, which is of particular importance for a proposed study of parity nonconservation in atoms, was measured to be 380?30? ns.