Dominik Hoffmann - Academia.edu (original) (raw)

Papers by Dominik Hoffmann

(A and B) Larval reaction to a range of vibration frequencies and intensities. Bar chart... more (A and B) Larval reaction to a range of vibration frequencies and intensities. Bar charts show head cast probability in a 5 s time window following vibration onset compared to a 5 s time window in the absence of vibration (0 Hz and 0 V, white bar). (A) Larvae significantly increase head cast probability compared to the baseline prior stimulation, in response to a range of frequencies from 100 Hz to 1000 Hz. N equals 92, 76, 104, 100 and 111 for 0 Hz, 100 Hz, 200 Hz, 400 Hz and 1000 Hz. p<10−6, for 0 Hz, compared to 100 Hz, 200 Hz, 400 Hz and 1000 Hz, respectively. (B) Head cast probability increases as voltage applied to the speaker increases, at 100 Hz and at 1,000 Hz, reaching the peak reaction of about 90%. N equals 67, 63, 76, 84, 105, 112, 111 and 105, respectively. p<10−6, for 100 Hz, 2.5 V and 5 V compared to 0 V and for 1000 Hz, 1 V, 2.5 V and 5 V, compared to 0 V. (C and D) Larval lateral ch (lch1-5) neurons sense 1000 Hz vibration. (C) An image of Ca2+ signals visualized with GCaMP3 in the dendrites (inside white rectangle) of lch1-5 in one abdominal hemisegment (A4), before stimulation (top and middle) and during a 1000 Hz, 2 V tone (1 sec after stimulus onset) (bottom). B, cell body cluster of lch1-5. D, dendrites of lch1-5. Anterior is up. Dorsal midline is to the right. Color code (middle and bottom panels), pseudocolored fluorescence intensity levels using the Fiji 16 color code <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0071706#pone.0071706-Schindelin1" target="_blank">[34]</a>. White and black, highest and lowest intensity, respectively. (D) Quantification of GCaMP responses in the five individual members of the lch1-5 cluster in A4. Graphs show mean ΔF/F0 in the dendrite of each ch neuron. Error bar represent s.e.m. N = 4 larvae. Different members of the lch1-5 cluster have differential sensitivity to 1000 Hz, the most sensitive being lch5, lch2, lch3 and lch4, and least sensitive lch1.</p

In this dissertation I present a variety of experiments on collisions between ultra-cold rubidium... more In this dissertation I present a variety of experiments on collisions between ultra-cold rubidium atoms. These collisions take place in light-force atom traps, where temperatures below 1 mK are reached. At these low temperatures weak, long-range interactions between the atoms are important, and collision times are long. Consequently, the absorption and spontaneous

(A and B) Graphs show head angle, and crabspeed and norm. crawling speed, as a function ... more (A and B) Graphs show head angle, and crabspeed and norm. crawling speed, as a function of time averaged across many animals from experiments in which larvae were presented with 30 s of continuous 470 nm light, at 25°C. Gray shading indicates the period of stimulation. Dark lines, mean value. Light lines, ± s.e.m. R, roll. EC, escape crawl. AC, avoidance crawl. Larvae with activated class IV (R38A10>ChR2, orange, N = 806) or ch (iav>ChR2, red, N = 1213) neurons are compared to no-retinal (R38A10>ChR2 no-retinal, green, N = 305 and iav>ChR2 no-retinal, blue, N = 361) and no-GAL4 controls (pBDPGAL4U>ChR2, black, N = 23305). Activation of class IV neurons evokes a peak in the crabspeed function (corresponding to the roll, R), followed by an increase in norm. crawling speed (corresponding to escape crawl, EC) compared to controls. Activation of ch neurons evokes a clear increase in norm. crawling speed during stimulation, resembling the avoidance crawl (AC) observed during vibration stimulation. Note also an increase in norm. crawling speed in response to 470 nm light offset in all tested lines (the off-reaction to light). (C) Bar charts show head casting, rolling and crawling probability and the absolute larval crawling speed, the maximum stride speed and stride frequency in a 5 s time window before stimulation (−5 s to 0 s) and in two consecutive 5 s time windows after stimulation (0 s to 5 s and 5 s to 10 s). Error bars indicate s.e.m. * or *, p<0.001.+or +, p<0.01. green, blue and black, indicate comparison to R38A10>ChR2-no-retinal, iav>ChR2-no-retinal and pBDPGAL4U>ChR2 controls, respectively. Activation of class IV neurons evokes a mild, but significant increase in rolling probability (4.3%) relative to both controls (0.6%, N = 305, p = 0.004468 and 0.2%, N = 23305, p<10−6 for no-retinal and no-GAL4, respectively) and a significant increase in crawling probability, mean absolute crawling speed and mean stride speed and a mild but significant increase in stride frequency (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0071706#pone.0071706.s004" target="_blank">Table S4</a> for details). Activation of ch neurons evokes a significant increase in head cast probability immediately following stimulation (82.3%, N = 1213) compared to both controls (73.1%, N = 361, p = 0.001584 and 68.2%, N = 23305, p<10−6 for non-retinal and no-GAL4, respectively) and a significant increase in crawling probability and mean absolute crawling speed relative to both controls (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0071706#pone.0071706.s004" target="_blank">Table S4</a> for further details).</p

(A and B) Vibration evokes a characteristic dynamic sequence of behaviors. (A) Graphs of... more (A and B) Vibration evokes a characteristic dynamic sequence of behaviors. (A) Graphs of mean normalized crawling speed, head angle, and normalized spine length as a function of time averaged across many animals from experiments in which wild-type Canton S (CS) larvae were presented with 30 s of continuous vibration (1000 Hz, 2 V) at ambient temperature of 32°C (red, N = 342) or 25°C (black, N = 248). Normalized crawling speed was computed as in Fig. 2D. Gray shading indicates the period of stimulation. Dark lines, mean value. Light lines, ± s.e.m. AC, avoidance crawl. OR, avoidance crawl off-reaction by speeding up. T, head cast (turn). H, hunch. Graphs highlight the dynamics of the reaction to vibration. Following vibration onset, there is a sharp well in the norm. spine length function, corresponding to the hunch (H), then a sharp peak in the head angle function (T), corresponding to the increase in head casting and turning. As these two functions return to baseline there is a raise in the speed function as larvae start crawling again. At 32°C the mean speed during vibration raises significantly above the speed prior to stimulation – indicating larvae are trying to actively avoid vibration by crawling faster (avoidance crawl). Following vibration offset there is significant increase in crawling speed relative to the baseline prior to stimulation at both 32°C and 25°C (avoidance crawl off-reaction, OR). Interestingly, while avoidance crawling in response to vibration offset happens at both temperatures, avoidance crawl during vibration only happens at 32°C, but not at 25°C. The precise nature of the reaction to vibration, like the reaction to noxious stimulation, is highly context-dependent. (B) Bar charts show the mean absolute larval crawling speed, the mean maximum head angle during head casts and the head casting and hunching probability in a 5 s time window before stimulation (−5 s to 0 s) and in two consecutive 5 s time windows after stimulation (0 s to 5 s and 5 s to 10 s). Error bars indicate s.e.m. * and *, p<0.001.+and +, p<0.01. The mean absolute larval crawling speed is significantly higher at 32°C than at 25°C, in all three time windows. At 32°C, but not at 25°C, the absolute mean crawling speed is higher in the 5 s to 10 s, than in the 0 s to 5 s window indicating that avoidance crawl during stimulation only happens at the higher temperature (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0071706#pone.0071706.s002" target="_blank">Table S2</a> for further details). Head cast angle and probability are higher at 32°C than at 25°C, whereas hunch probability is higher at 25°C than at 32°C. Even though the reactions to vibration are significantly different at different temperatures, many aspects of the reaction are pronounced enough at 25°C to allow the use of the permissive temperature UAS-Shibirets1 control. (C and D) Ch neurons are implicated in most aspects of the larval reaction to vibration. (C) Graphs of mean normalized crawling speed, head angle, and normalized spine length as in A at 32°C. Gray shading indicates the period of stimulation. Dark lines, mean value. Light lines, ± s.e.m. Data from larvae with inactivated ch neurons (red, iav>shibirets1 at restrictive temperature of 32°C, N = 820) is compared to three different kinds of control larvae. Blue, iav>shibirets1 at permissive temperature of 25°C (N = 299). Green, iav>Canton S at 32°C (N = 457). Black, pBDPGAL4U>shibirets1 at 32°C (N = 24,865). Most aspects of the reaction to vibration are compromised in larvae with inactivated ch neurons, compared to controls. Avoidance crawl and off-reaction in the normalized speed function are not visible. The peak in the head angle function is drastically reduced. The well in the norm. spine length function is gone and instead a small peak is visible – indicating that the residual reaction to vibration that is left is actually opposite in sign and abnormal. (D) Bar charts show the mean absolute larval crawling speed, the mean maximum head angle during head casts and the head casting and hunching probability as in B. Error bars indicate s.e.m. * (blue star), * (green star) and * (black star) indicate p<0.001 when iav>shibirets1 at 32°C is compared to iav>shibirets1 at 25°C, iav>Canton S at 32°C and pBDPGAL4U>shibirets1 at 32°C, respectively. The magnitude of the head cast angle and the head cast and hunch probability following stimulation are significantly reduced in iav>shibirets1, compared to all three controls (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0071706#pone.0071706.s002" target="_blank">Table S2</a> for further details).</p

(A and B) Air current evokes a characteristic dynamic sequence of behaviors, distinct to... more (A and B) Air current evokes a characteristic dynamic sequence of behaviors, distinct to vibration. (A) Graphs of mean normalized crawling speed, head angle, and normalized spine length as a function of time averaged across many animals from experiments in which wild-type Canton S (CS) larvae were presented with 45 s of continuous air current (6.5 m/s) at 32°C (red, N = 318) or 25°C (black, N = 201). Normalized crawling speed was computed as in Fig. 2D. Gray shading indicates the period of stimulation. Dark lines, mean value. Light lines, ± s.e.m. OR, off-reaction by slowing down. T, head cast (turn) at stimulus onset and offset. H, hunch. Following air current onset, there is a well in the norm. spine length function, corresponding to the hunch (H), followed by a peak in the head angle function (T), corresponding to the increase in head casting and turning. The reaction to air current at different temperatures is quite similar. Thus the reactions to vibration and air current are drastically different at 32°C. During vibration at this temperature larvae exhibit avoidance crawling, whereas during air current they slow down and continue hunching and turning. Furthermore the off-reactions to vibration and air current are opposite in sign, at both temperatures. In response to air current offset larvae slow down and head cast more, whereas in response to vibration offset they speed up (avoidance crawl) and head cast less. (B) Bar charts show the absolute larval crawling speed, the maximum head angle during head casts and head casting and hunching probability as in Fig. 7B. Error bars indicate s.e.m. * and *, p<0.001.+and +, p<0.01. The mean absolute larval crawling speed is significantly higher at 32°C than at 25°C in all three time windows, but it is always lower during air current than prior to air current. Head cast probability during air current stimulation is higher at 32°C than at 25°C (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0071706#pone.0071706.s003" target="_blank">Table S3</a> for details). (C and D) Ch neurons are implicated in larval reaction to air current. (C) Graphs of mean normalized crawling speed, head angle, and normalized spine length as in A at ambient temperature of 32°C. Gray shading indicates the period of stimulation. Dark lines, mean value. Light lines, ± s.e.m. Data from larvae with inactivated ch neurons (red, iav>shibirets1 at restrictive temperature of 32°C, N = 362) is compared to three different kinds of control larvae. Blue, iav>shibirets1 at permissive temperature of 25°C (N = 242). Green, iav>Canton S at 32°C (N = 296). Black, pBDPGAL4U>shibirets1 at 32°C (N = 1616). Some aspects of the reaction to air current are more compromised than other in larvae with inactivated ch neurons. The peak in the head angle function is drastically reduced. The well in the norm. spine length function is gone and instead a small peak is visible. (D) Bar charts show the mean value of the absolute larval crawling speed, the mean maximum head angle during head casts and the head casting and hunching probability as in B. Error bars indicate s.e.m. * (blue star), * (green star) and * (black star) indicate p<0.001 when iav>shibirets1 at 32°C is compared to iav>shibirets1 at 25°C, iav>Canton S at 32°C and pBDPGAL4U>shibirets1 at 32°C, respectively. The magnitude of the head cast angle and the head cast and hunch probability following stimulation are significantly reduced in iav>shibirets1 at 32°C, compared to all three controls (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0071706#pone.0071706.s003" target="_blank">Table S3</a> for details).</p

(A) Expression patterns of R38A10 and R20C06. Conf... more (A) Expression patterns of R38A10 and R20C06. Confocal microscope images of the A3 hemisegment of third instar R38A10>GFP and R20C06>GFP larvae. Larvae are co-immunostained with antibodies against GFP (green, left; white, right) and 22C10, a marker of all peripheral sensory neurons (magenta, left). Anterior is up. Dorsal midline is to the right. Scale bar represents 100 µm. R38A10 drives expression in class IV neurons (arrowheads) and R20C06 in class I md neurons (arrows) (compare to the reference images in Grueber et al. 2002 <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0071706#pone.0071706-Grueber1" target="_blank">[54]</a>). (B and C) Graphs show head angle, crabspeed and normalized crawling speed as a function of time as in Fig. 2D. Dark lines, mean value. Light lines, ± s.e.m. Grey lines at 0 s mark the stimulus onset and duration. Data from control R38A10>Canton S and R20C06>Canton S at 32°C (green, N = 91 and 102, respectively) and 25°C (blue, N = 98 and 184, respectively) is compared. The increase in the mean crabspeed function following stimulation (corresponding to the roll) is present under both conditions, but it is both faster and larger at 32°C compared to 25°C. Escape crawl looks similar under both conditions (the increase in mean speed in response to noxious stimulation, relative to mean speed prior to stimulation), although the absolute crawling speed is drastically different (see below). (D) Bar charts show head casting and rolling probability and the mean value of the maximum stride frequency and stride speed as in Fig. 2E. Error bars indicate s.e.m. * (light blue star) and * (dark blue star), p<0.001 for R38A10>Canton S and R20C06>Canton S, respectively, when behavior at 32°C is compared to 25°C in the same time window. Rolling probability of R38A10>Canton S (light green) and R20C06>Canton S (dark green) is drastically increased at 32°C compared to 25°C (light blue and dark blue) (from 36% and 32% to 71% and 63.6%, N = 105, 171, 76, 55; p = 0.000063 and 0.000846). Likewise, stride frequency and stride speed are significantly increased at 32°C compared to 25°C, both prior to stimulation and following stimulation (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0071706#pone.0071706.s001" target="_blank">Table S1</a> for further details).</p

(A and C) Graphs show head angle, crabspeed and normalized crawling speed as a function ... more (A and C) Graphs show head angle, crabspeed and normalized crawling speed as a function of time as in Fig. 2D. Dark lines, mean value. Light lines, ± s.e.m. Grey lines at 0 s mark the stimulus onset and duration. Data from control pBDPUGAL4>shibirets1 (black, N = 8461) and R38A10>Canton S or R20C06>Canton S at 32°C (green, N = 76 and 55, respectively) and R38A10>shibirets1 or R20C06>shibirets1 (red, N = 915 and 1144, respectively) is compared. (B and D) Bar charts show head casting and rolling probability and the mean value of the maximum stride frequency and stride speed as in Fig. 2E. Error bars indicate s.e.m. * (black star), p<0.001 when compared to pBDPUGAL4>shibirets1 in the same time window. * (green star), p<0.001 when compared to R38A10>Canton S or R20C06>Canton S in the same time window. Rolling probability of R38A10>shibirets1 (B, red, 29.1%, N = 915) is drastically reduced compared to pBDPUGAL4>shibirets1 (B, black, 42.6%, N = 8461; p<10−6) and R38A10>Canton S (B, green, 71.1%, N = 76; p<10−6) in the time window following noxious heat stimulation. Likewise, stride frequency and stride speed are significantly decreased compared to controls, both prior to stimulation and following stimulation (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0071706#pone.0071706.s001" target="_blank">Table S1</a> for further details). Rolling probability of R20C06>shibirets1 (D, red, 32.7%, N = 1144) is drastically reduced compared to pBDPUGAL4>shibirets1 (D, black, 42.6%, N = 8461; p<10−6) and R20C06>Canton S (D, green, 63.6%, N = 55; p = 0.000045) in the time window following noxious heat stimulation. Likewise, stride frequency and stride speed are significantly decreased compared to both controls, both prior to stimulation and following stimulation (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0071706#pone.0071706.s001" target="_blank">Table S1</a> for further details), consistent with the role of these neurons in proprioception.</p

(A) Larvae roam a plastic dish filled with agar (1). A high-resolution camera (2) collec... more (A) Larvae roam a plastic dish filled with agar (1). A high-resolution camera (2) collects images to track their movement and body shapes. A ring light (3) provides illumination. Different hardware modules impart stimuli: air current through a 3D-printed flare nozzle (4) connected to plant-supplied compressed air, vibration and sound through a speaker (5a or 5b), blue light for ChR2 activation through an array of high-power blue LEDs (470 nm) underneath the arena (6), and noxious heat through high-power IR light (808 nm) delivered from solid-state lasers (7). (B and C) Snapshots of animals at the start of the experiment on the nociceptive stimulation rig, showing dots for absorption of the 808 nm laser light. Scale bar = 5 cm. Average dot size was 73.28 mm2±4.32 mm2 (s.e.m.). Dots can be placed on the top (B) or on the side (C) to study the directionality of the response. <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0071706#pone.0071706.s005" target="_blank">Movie S1</a> shows larvae with dots on the top rolling in response to 808 nm laser stimulation. Larvae roll in random directions. <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0071706#pone.0071706.s006" target="_blank">Movie S2</a> shows larvae with dots on the left hand side rolling to the left. (D and E) Characterization of the vibration frequency and g-force on agar surface in our rig. (D) Spectral power density plots (|X(f)|) obtained with Fast Fourier Transform (FFT) analysis of the acceleration of the agar surface of the arena when the speaker played 1,000 Hz tones (2 V) (X, Y, Z axis). The spectrum at 1000 Hz is normalized by the spectrum at 0 Hz which represents gravity ( = 1 g). (E) G-force at 1000 Hz increases linearly with increasing voltage applied to the speaker.</p

Physical Review Letters, 1998

We have observed violet photon emission resulting from energy-pooling collisions between ultracol... more We have observed violet photon emission resulting from energy-pooling collisions between ultracold Rb atoms illuminated by two colors of near-resonant infrared laser light. We have used this emission as a probe of doubly excited state ultracold collision dynamics. We have observed the lowest saturation intensity for light-induced ultracold collisions seen to date which we identify as due to depletion of incoming ground state flux. We have also varied the detuning of the lasers which allows us to clearly identify the effect of spontaneous emission and optical shielding. [S0031-9007(98)06710-6]

$Research paper thumbnail of Laser-induced ultracold Rb(5S_{1/2})+Rb(5P_{1/2}) collisions$

Physical Review A, 1994

Measurements of collisional loss of optically trapped Rb atoms are presented for excitation of th... more Measurements of collisional loss of optically trapped Rb atoms are presented for excitation of the colliding atoms by light tuned near the 5[ital S][sub 1/2][r arrow]5[ital P][sub 1/2] transitions of [sup 85]Rb and [sup 87]Rb. Using the [ital P][sub 1/2] state allows the effects of spontaneous emission on excited-state collisions to be studied with minimal complications arising from hyperfine structure. The shapes of the collision spectra are nearly identical for the two isotopes and are consistent with a simple model for the role of spontaneous emission during the collision.

Journal of Physics: Condensed Matter, 2002

We demonstrate a minimally invasive nuclear magnetic resonance (NMR) technique that enables deter... more We demonstrate a minimally invasive nuclear magnetic resonance (NMR) technique that enables determination of the surface-area-to-volume ratio (S/V) of soft porous materials from measurements of the diffusive exchange of laser-polarized 129 Xe between gas in the pore space and 129 Xe dissolved in the solid phase. We apply this NMR technique to porous polymer samples and find approximate agreement with destructive stereological measurements of S/V obtained with optical confocal microscopy. Potential applications of laser-polarized xenon interphase exchange NMR include measurements of in vivo lung function in humans and characterization of gas chromatography columns.

The use of spin-polarized noble gases for magnetic resonance imaging and spectroscopy has attract... more The use of spin-polarized noble gases for magnetic resonance imaging and spectroscopy has attracted a great deal of attention recently, especially in the biomedical community. However, experimentation has been limited by the availability of polarized gas. In our lab, we are investigating theoretically and experimentally the factors that determine the quantity of polarized gas (^129Xe, in particular) that can be

We have studied ultracold collisions between ground state rubidium atoms in the presence of light... more We have studied ultracold collisions between ground state rubidium atoms in the presence of light from two nearly resonant lasers. The first laser is detuned 90 MHz to the red of the 5S_1/2(F=3) arrow 5P_1/2(F'=2) transition and excites colliding atoms at a rather large separation to a singly excited (5S+5P) Rb2 molecular state. The second laser is detuned between 90 MHz and 2.4 GHz to the blue of the 5S_1/2(F=3) arrow 5P_1/2(F'=3) transition and further excites the atoms to a doubly excited (5P+5P) Rb2 molecular state. The two-photon absorption sequence has a profound effect on the dynamics of the collision. A signature of the doubly excited state collision is the emission of a violet photon at small interatomic separation. We have studied the emission rate of violet photons as a function of detuning of the second laser and find a broad dependence, ~1 GHz wide, centered at about 1 GHz and with a threshold detuning around 90 MHz. Atoms are initially prepared in a standard MOT, and the collision process has been studied both with and without the trapping light present.

Physical Review A, 1996

We report measurements of the intensity correlations of scattered light from atoms in optical mol... more We report measurements of the intensity correlations of scattered light from atoms in optical molasses. For small numbers of atoms, the observations are consistent with recent models of the Rayleigh and Raman contributions to the frequency spectrum. Magnetic fields on the order of 100 mG significantly broaden the spectrum. Radiation trapping results in reduction of the size of the correlations as well as broadening of the spectrum. ͓S1050-2947͑96͒03605-0͔

(A and C) Graphs show head angle, crabspeed and normalized crawling speed as a function ... more (A and C) Graphs show head angle, crabspeed and normalized crawling speed as a function of time, as in Fig. 2. Dark lines, mean value. Light lines, ± s.e.m. Grey lines at 0 s mark stimulus onset and duration. Data from the control painless1>w1118 (light green, N = 53), painless3>w1118 (dark green, N = 45) and piezoKO>w1118 (blue, N = 51) is compared to painless1 (orange, N = 126), painless3 (red, N = 181) and piezoKO (red, N = 130) mutants, respectively. In both painless1 and painless3 mutants the peaks in the mean crabpseed and the mean normalized speed functions are highly reduced compared to controls. They show virtually no escape crawl. (B and D) Bar charts show head casting and rolling probability and the mean value of the maximum stride frequency as in Fig. 2E. Error bars indicate s.e.m. * (light green star), * (dark green star) and * (blue star) indicate p<0.001 when painless1, painless3 and piezoKO is compared to painless1>w1118, painless3>w1118 and piezoKO>w1118, respectively. In response to noxious heat stimulus, the rolling probability of painless1 (11.9%, N = 126) and painless3 (6.1%, N = 181) larvae, defective in thermal nociception, is significantly reduced compared to the hemizygous controls (49.1%, N = 53, p<10−6 and 31.1%, N = 45, p = 0.000054). The mutants also have significantly reduced stride frequency and stride speed following stimulation and reduced stride frequency prior to stimulation (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0071706#pone.0071706.s001" target="_blank">Table S1</a> for further details). In contrast, piezoKO mutant larvae defective in mechanical nociception roll slightly, but not significantly more than the hemizygous controls. Interestingly they are significantly defective in escape crawl and in stride speed prior to stimulation.</p

Physical Review Letters, 1998

Physical Review A, 1993

We present measurements of excited-state trap-loss collisions of optically trapped ⁸⁵Rb and ⁸⁷Rb ... more We present measurements of excited-state trap-loss collisions of optically trapped ⁸⁵Rb and ⁸⁷Rb atoms as a function of the frequency of the light used to excite the colliding atom pairs. For detunings outside the excited-state hyperfine structure, the trap-loss rates are found to be the same for the two isotopes. For detunings inside the excited state hyperfine structure, ⁸⁷Rb collisions occur ·at a substantially lower rate than those of ⁸⁵Rb. The spectra make it clear that the long-range dynamics of the collisions are strongly modified by the excited-state hyperfine structure, and that the dynamics are different for the two isotopes.

Physical Review Letters, 1998

$Research paper thumbnail of Laser-induced ultracold Rb(5S_{1/2})+Rb(5P_{1/2}) collisions$

Physical Review A, 1994

Journal of Physics: Condensed Matter, 2002

Physical Review A, 1996

(A and C) Graphs show head angle, crabspeed and normalized crawling speed as a function ... more (A and C) Graphs show head angle, crabspeed and normalized crawling speed as a function of time, as in Fig. 2. Dark lines, mean value. Light lines, ± s.e.m. Grey lines at 0 s mark stimulus onset and duration. Data from the control painless1>w1118 (light green, N = 53), painless3>w1118 (dark green, N = 45) and piezoKO>w1118 (blue, N = 51) is compared to painless1 (orange, N = 126), painless3 (red, N = 181) and piezoKO (red, N = 130) mutants, respectively. In both painless1 and painless3 mutants the peaks in the mean crabpseed and the mean normalized speed functions are highly reduced compared to controls. They show virtually no escape crawl. (B and D) Bar charts show head casting and rolling probability and the mean value of the maximum stride frequency as in Fig. 2E. Error bars indicate s.e.m. * (light green star), * (dark green star) and * (blue star) indicate p<0.001 when painless1, painless3 and piezoKO is compared to painless1>w1118, painless3>w1118 and piezoKO>w1118, respectively. In response to noxious heat stimulus, the rolling probability of painless1 (11.9%, N = 126) and painless3 (6.1%, N = 181) larvae, defective in thermal nociception, is significantly reduced compared to the hemizygous controls (49.1%, N = 53, p<10−6 and 31.1%, N = 45, p = 0.000054). The mutants also have significantly reduced stride frequency and stride speed following stimulation and reduced stride frequency prior to stimulation (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0071706#pone.0071706.s001" target="_blank">Table S1</a> for further details). In contrast, piezoKO mutant larvae defective in mechanical nociception roll slightly, but not significantly more than the hemizygous controls. Interestingly they are significantly defective in escape crawl and in stride speed prior to stimulation.</p

Physical Review Letters, 1998

Physical Review A, 1993