IR Response Research Articles

Phase II multicenter trial of ipilimumab combined with fotemustine in patients with metastatic melanoma: The Italian Network for Tumor Biotherapy (NIBIT)-M1 trial.

8513 Background: Ipilimumab (ipi), an antibody against cytotoxic T-lymphocyte-associated antigen-4, improves survival in patients (pts) with metastatic melanoma (MM); however, objective tumor responses are limited. NIBIT-M1 aims to investigate the efficacy and safety of ipi plus fotemustine (FTM), a cytotoxic alkylating drug, in pts with MM. Methods: Eligible pts, with or without brain metastases, received induction therapy with ipi 10 mg/kg every 3 weeks (Q3W) for four doses and FTM 100 mg/m2 weekly for 3 weeks. Ipi and FTM maintenance therapy was provided Q12W from Week 24 and Q3W from Week 9, respectively. The primary objective was the immune-related (ir) disease control rate (irDCR: pts with complete response [CR], partial response [PR] or stable disease [SD] as determined using the ir response criteria). Secondary objectives included ir objective response rate (ORR), duration of response (DOR) and progression-free survival (PFS); overall survival (OS), and safety. Tumor assessments were performed Q8W from Week 12 to Week 36 and Q12W thereafter. Results: Among 86 pts with unresectable stage III (n=3) or stage IV (n=83) MM treated at 7 NIBIT centers, 42 were previously untreated, 44 had progressed following first-line treatment and 20 had asymptomatic brain metastases. As of December 2011, the irDCR was 46.5% (40/86; 95% CI, 35.7–57.6%); the irORR was 29.1% (95% CI, 19.8–39.8%; 5 CRs and 20 PRs) and with a median 8.3 months follow-up, median irPFS was 5.3 months (95% CI, 3.5–7.1). The 1-year OS rate was 51.8% (95% CI, 37.5–66.1%); median OS was not yet reached. Among all pts, 58.1% and 87% completed ipi or FTM induction, respectively. The most common grade 3/4 drug-related adverse events (AEs) (reported in 54.6% pts overall) were myelotoxicity (43.5%), increased ALT/AST (14.1/10.6%), gastrointestinal (4.7%) and skin-related (2.3%). AEs were generally manageable and reversible per protocol guidance. Conclusions: The study reached its primary objective with 46.5% of pts achieving disease control. The combination of ipi plus FTM is safe; the irDCR, 1-year OS rate and median irPFS warrant its further investigation in MM pts.

Glucokinase activation repairs defective bioenergetics of islets of Langerhans isolated from type 2 diabetics.

It was reported previously that isolated human islets from individuals with type 2 diabetes mellitus (T2DM) show reduced glucose-stimulated insulin release. To assess the possibility that impaired bioenergetics may contribute to this defect, glucose-stimulated respiration (Vo(2)), glucose usage and oxidation, intracellular Ca(2+), and insulin secretion (IS) were measured in pancreatic islets isolated from three healthy and three type 2 diabetic organ donors. Isolated mouse and rat islets were studied for comparison. Islets were exposed to a "staircase" glucose stimulus, whereas IR and Vo(2) were measured. Vo(2) of human islets from normals and diabetics increased sigmoidally from equal baselines of 0.25 nmol/100 islets/min as a function of glucose concentration. Maximal Vo(2) of normal islets at 24 mM glucose was 0.40 ± 0.02 nmol·min(-1)·100 islets(-1), and the glucose S(0.5) was 4.39 ± 0.10 mM. The glucose stimulation of respiration of islets from diabetics was lower, V(max) of 0.32 ± 0.01 nmol·min(-1)·100 islets(-1), and the S(0.5) shifted to 5.43 ± 0.13 mM. Glucose-stimulated IS and the rise of intracellular Ca(2+) were also reduced in diabetic islets. A clinically effective glucokinase activator normalized the defective Vo(2), IR, and free calcium responses during glucose stimulation in islets from type 2 diabetics. The body of data shows that there is a clear relationship between the pancreatic islet energy (ATP) production rate and IS. This relationship was similar for normal human, mouse, and rat islets and the data for all species fitted a single sigmoidal curve. The shared threshold rate for IS was ∼13 pmol·min(-1)·islet(-1). Exendin-4, a GLP-1 analog, shifted the ATP production-IS curve to the left and greatly potentiated IS with an ATP production rate threshold of ∼10 pmol·min(-1)·islet(-1). Our data suggest that impaired β-cell bioenergetics resulting in greatly reduced ATP production is critical in the molecular pathogenesis of type 2 diabetes mellitus.

El efecto de variar el programa de presentación de estímulo sobre la percepción de causalidad en palomas

It is known that pigeons can discritninate between events produced by their own behavior ami events produced by other sources. Tite typical preparation consists in pre¬sen ting a sti,nulus change in the central key according te two concurrent randotn-ratio schedules; ene is key-peck dependent and tite other ir response independent. After the stsmulus change has occurred, tite pigeons report en ene of tite two lateral keys whether tite change was self-produced or equipment-produced. If tite response ir “correct’ grain isprovided. If tite response ir “incorrect”, it ispunished by a time-out.Using this procedure, tite acquisition of tite discrimination was tested under two values of tite random-ratio scitedule: RAS and RR2O. Jn a second fase of tite study, tite value of tite RA scitedule was varied: 2, 5, 10, 20, 50, 100 amI 200 responses were requiredfor a stintulus change.It was found titat tite RR2O was more conducive te tite adquisition of tite dtscrtmtnatson titan tite RAS. It was also found titat once tite discrimination had been acquired, varying tite RA scitedule itad no sensible effect en tite perception of causality.

Abstract 573: Ionizing radiation activates IFN signaling in tumor cells

Abstract Ionizing radiation (IR) uses multiple pathways to mediate killing in tumor cells. We found that fractionated irradiation leads to the constitutive overexpression of Interferon Stimulated Genes (ISGs) which are controlled by Signal Transducer and Activator of Transcription 1 (Stat1). Stat1 mediated IFN signal transduction and at the same time was involved in the production of Type I and Type II IFNs. IR-induced ISGs represent the following groups: 1) mitochondrial-related genes with pro- and anti-apoptotic functions, 2) cell cycle control and regulators of transcription, 3) protein modification and degradation, 4) cytoplasmic sensors of nucleic acids, and 5) anti-viral defense. Fractionated or single-dose IR induced the IFN pathway mediated by activation of Stat1 in breast, colon, prostate and head and neck tumor xenografts. Depletion of tumor-derived IFNs led to the suppression of IR response indicating that IFN production/signaling is a component of anti-tumor IR action. Cell-autonomous experiments indicated that tumor cells up-regulate Stat1 and ISGs and produce IFNα in response to single dose IR (3Gy). Up-regulated Stat1 in irradiated tumor cells was not phosphorylated at Tyr701 position compared to Stat1 activation following interferon stimulation. In a syngeneic tumor model of B16F1, IR-induced activation of IFN signaling in tumors (assessed both by up-regulation of the Stat1-dependent pathway and induction of Type I and Type II IFNs) was dependent on TNFα signaling in the host and was impaired in TNFR1,2-/- mice. We therefore conclude that IR induces IFN signaling in tumor cells as a component of the cytotoxic response. This interferon induction depends on TNFα signaling in host cells. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 573. doi:10.1158/1538-7445.AM2011-573

Low-Cost ZnO-Based Ultraviolet–Infrared Dual-Band Detector Sensitized With PbS Quantum Dots

A low-cost photoconductive dual-band detector based on a ZnO film sensitized with lead sulfide quantum dots (PbS-QDs) is reported. The UV response arises from the interband absorption of UV radiation by ZnO, and the IR response is due to the absorption in the PbS-QDs. The detector exhibits UV response from 200 to 400 nm with a peak responsivity of 4.0 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sup> V/W and detectivity D* of 5.5 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sup> Jones at 370 nm at room temperature. The observed visible-near IR response is from 500 to 1400 nm with a responsivity of 5.4 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sup> V/W and D* of 7.3 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sup> Jones at 700 nm operating at room temperature. By increasing the PbS-QD size, the IR response can extend up to 2.9 μm.

Effects of Ischemic Preconditioning and Bevacizumab on Apoptosis and Vascular Permeability Following Retinal Ischemia–Reperfusion Injury

Using transient ischemia followed by reperfusion (IR) to model ischemic retinal disease, this study compares the effects of ischemic preconditioning (IPC) and therapies targeting vascular endothelial growth factor (VEGF) and tumor necrosis factor (TNF)-α on retinal apoptosis, vascular permeability, and mRNA expression. Rats were subjected to 30 or 45 minutes of retinal ischemia followed by reperfusion for up to 48 hours. Neurodegeneration was quantified by caspase-3 (DEVDase) activity and by measuring nucleosomal DNA content (cell death ELISA). Vascular leakage was quantified by the Evans Blue dye method. A set of IR-responsive mRNAs was identified by whole-genome microarray and confirmed by RT-PCR analyses. VEGF protein was measured by Western blot analysis. IPC was accomplished with 10 minutes of ischemia 24 hours before IR. VEGF and TNFα signaling was inhibited by intravitreal injection of bevacizumab or etanercept, respectively. IR caused significant retinal cell apoptosis and vascular permeability after 4 and 48 hours. Whereas IR decreased VegfA mRNA, VEGF protein was significantly increased. IPC effectively inhibited neurodegeneration, bevacizumab effectively inhibited vascular permeability, and etanercept failed to affect either outcome. IPC significantly altered the IR responses of 15 of 33 IR-responsive mRNAs, whereas bevacizumab had no significant effect on these mRNAs. IR provides an acute model of ischemic retinopathy that includes neurodegeneration and VEGF-dependent vascular permeability and is amenable to rapid drug therapy testing. The distinct effects of IPC and bevacizumab demonstrate that the apoptotic and vascular responses to IR may be separated and that therapeutics targeting each pathologic endpoint may be warranted in treating ischemic retinal diseases.

Low-Cost UV-IR Dual Band Detector Using Nonporous ZnO Film Sensitized by PbS Quantum Dots

A low-cost photoconductive dual-band detector was prepared using a nanoporous ZnO film sensitized by PbS quantum dots (QDs). At room temperature the device shows a UV response in the wavelength range of 200–400 nm with a 370 nm peak responsivity of 4.0 × 105 V/W and a vis-NIR response from 500 to 1400 nm with a 700 nm peak responsivity of 5.4 × 105 V/W. By increasing the size of the PbS QD, the response can be extended up to 2.9 μm. It is suggested that the UV response is a result of interband absorption of UV radiation by ZnO and the IR response comes from the absorption of PbS QDs.

Smart polymer surfaces: mapping chemical landscapes on the nanometre scale

We show that Scattering Infrared Near-field Microscopy (SNIM) allows chemical mapping of polymer monolayers that can serve as designed nanostructured surfaces with specific surface chemistry properties on a nm scale. Using s-SNIM a minimum volume of 100 nm × 100 nm × 15 nm is sufficient for a recording of a “chemical” IR signature which corresponds to an enhancement of at least four orders of magnitudes compared to conventional FT-IR microscopy. We could prove that even in cases where it is essentially difficult to distinguish between distinct polymer compositions based solely on topography, nanophase separated polymers can be clearly distinguished according to their characteristic near-field IR response.

Response analysis of free-membrane transition-edge detectors with thin substrates

In this work, we have investigated and presented the bolometric response of freestanding membrane type of superconductive transition-edge detectors at micro-scale and submicron-scale substrate thicknesses. The technique applied here is based on the finite-size scaling method which is now extensively used for the calculation of thermal parameters of materials at low dimensions when the significance of surface energy contribution is not negligible compared to that of the total bulk energy. This method is used to evaluate the variation of specific heat per unit volume and heat conductivity and hence its effect on the total heat capacitance and conductance of the substrate versus its thickness. By using the thermal parameters obtained from the applied method we calculated the IR response in these types of the devices. This response when inspected at low thicknesses of substrates showed anomalistic behavior with respect to previous response analyses. Discussed in this paper, we also obtained the optimized substrate thickness for maximum responsivity of the device. The obtained results are compared to previous response calculations and experimental measurements.

Analysis of Evolved Species and Estimation of the Combustion Emissions of PACB and AAC Preservatives Using TGA-IR and CEM Techniques

The results obtained from the TGA tests found that the decomposition temperature of AAC and PACB at the heating rate of 5 ˚C/min was lower than that at 40 ˚C/min. Regardless of the different heating rates, the decomposition temperatures of PACB were all higher than those for AAC, and the char (wt %) of the PACB (65.38 wt % for 5 ˚C/min and 66.92 wt % for 40 ˚C/min) was more than that of the AAC (0.042 wt % for 5 ˚C/ min and 0.046 wt % for 40 ˚C/min). The IR response of AAC and PACB in the TGA–IR tests showed that at a heating rate of 5 ˚C/min, the evolved species of AAC were less than those of PACB. However, at a heating rate of 40 ˚C/min the numbers of evolved species of AAC were much higher than those of PACB. Considering the decomposition step (thermal time or temperature) at different heating rates in the TGA tests and the IR response from the TGA–IR analysis, the results showed that at the slow–heating regime, the concentrations of CO2 and the evolved species of =CH2 groups produced by PACB were higher than those of AAC, but at 40 ˚C/min the results were reversed. The results of combustion emissions obtained by CEM techniques found that the emission gas temperature of AAC was higher than that of PACB. Both O2 and CO2 reached a plateau curve until the end of combustion, during which time they were closely related. The highest emission quantity of CO was about 94.0 ppm for AAC, but it was 120.0 ppm for PACB. The emission quantity of SO2 for each type of sample was zero. The maximum NOx for AAC was about 49.5 ppm, but it was insignificant for the amount of PACB during combustion. The above results of the TGA–IR and CEM analysis allowed us to determine the kinds of evolved species and the emission gas concentrations of O2 and CO2, the emission contents (CO, SO2, NOx), and the temperature of the emission gases for referencing the thermo–decomposition processes of AAC and PACB during combustion.

Femtosecond IR Pump-Probe Spectroscopy of Nonlinear Energy Localization in Protein Models and Model Proteins

This paper reviews our experimental and theoretical efforts toward understanding vibrational self-trapping of the amide I and N-H mode of crystalline acetanilide (ACN), other similar hydrogen-bonded crystals, as well as of model peptides. In contrast to previous works, we used nonlinear IR spectroscopy as the experimental tool, which is specifically sensitive to the anharmonic contributions of the intramolecular interactions (as the nonlinear IR response of set of harmonic oscillators vanishes exactly). Our work reconfirms the previous assignment of the two bands of the amide I mode of ACN as being a self-trapped and a free exciton state, but in addition also establishes the lifetimes of these states and identifies the relevant phonons. Furthermore, we provide evidence for vibrationally self-trapped states also in model alpha-helices. However, given the short lifetime, any biological relevance in the sense of Davydov's initial proposal can probably be ruled out.

Magnetic field dependence of the photoresponse time of GaAs/AlGaAs quantum Hall effect device

The characteristic time of far IR response of a quantum Hall effect (QHE) detector in a GaAs/AlGaAs heterostructure has been investigated versus the magnetic field around the even values of the Landau level filling factor ν = 2, 4. The response time is shown to have a dip minimum in the center of a QHE plateau and two sharp maxima at either side of the plateau. Outside the QHE plateau the response time drop seems to result from the rise of the equilibrium population of Landau level over/below the Fermi energy with electrons/holes which increases the probability of photoexcited carrier recombination. The minimum at the QHE plateau center is due to the vanishing of screening of the random potential. The length scale of the potential fluctuations has been estimated.

Optical radiation selective photodetectors based on III nitrides

Wide direct band gap III nitride materials have opened up many new optoelectronic applications because they allow access to a very wide spectral range, from 200nmto1.77μm, from a single material system. Both light emission sources and photodetectors with advanced properties can be achieved through tailoring layered III nitride structures with various layer orders, chemical compositions, conductivities, and thicknesses. In addition, substrate selection plays an important role in the fabrication of these devices as well as in achieving desired device properties. Along with the efficiency of detection, in most cases it is important to provide selectivity of the optical radiation sensed by the optical device. Such selectivity can be achieved by using spectral properties of optical radiation. In this article the authors present results on the modeling of dual-band photodiode structures based on III nitrides, grown on silicon substrates. UV/IR visible- and solar-blind UV/IR photodetectors have been demonstrated. The peak responsivities of the dual-band photodetectors are 3.8 and 55mA∕W at wavelengths of 349 and 1000nm, respectively. Results on the modeling of the dual-band photodiodes in order to optimize the IR response and realize the solar-blind capability are presented.

The role of 5-R-1,10-phenanthroline (R = CH 3, NO 2) on the emission properties and second-order NLO response of cationic Ir(III) organometallic chromophores

[Ir(cyclometallated 4,5-diphenyl-2-methyl-thiazole) 2(5-R-1,10-phenanthroline)][PF 6] (R = CH 3, NO 2) complexes were prepared and fully characterized, the structure of the complex with 5-CH 3-1,10-phenanthroline being also determined by X-ray diffraction. The emission properties of both complexes have been investigated and their second-order nonlinear optical (NLO) response has been determined experimentally by the EFISH technique and found to be similar but slightly lower than that of related [Ir(ppy) 2(5-R-1,10-phenanthroline)][PF 6] (ppy = cyclometallated 2-phenylpyridine), characterized by one of the highest second-order NLO response ever reported for a metal complex. In the complexes, SOS/TDDFT calculations show that the large and negative sign of the measured hyperpolarizability is mainly due to the significant contribution of rather intense MLCT transitions involving the phenanthroline as acceptor ligand.

Simultaneous Determination of SO3(g) and SO2(g) in a Flowing Gas

A method for assaying a flowing gas mixture for SO2(g) and SO3(g) is described. The proof-of-concept for this method presented here uses the quantitative reaction of SO3(g) with CaC2O4(s) at 325 °C to produce CO2(g). The gas mixture is passed first through a plug of CaC2O4 and then through a series of two optical cells. SO2(g) is measured directly at one cell by UV spectrometry, and SO3(g) is measured indirectly as CO2(g) at the second cell by IR spectrometry. Good correlation coefficients were found for both analytes. Potential interference by SO2 on the IR response of CO2 can be neglected within a 1% error marginexcept when the ratio CO2/SO2 is very small. A summary of key analytical methods for the analysis of sulfur oxides is given.

アミロペクチン単位鎖長分布による水稲糯品種の餅硬化性評価

Waxy rice is used for staple and processed foods, and for its effective breeding an evaluation/selection index has been required. Here, the chain-length distribution of amylopectin from japonica waxy rice varieties with different hardness of rice cake were analyzed by the fluorescent labeling/HPSEC method, and the relation of the unit chain-length distribution to the hardness was examined. The difference among varietals was found in the amylopectin structure. Waxy rice producing soft cake, such as Hakuchoumochi, has more short chains (A+B1), and fewer long chains (B2+B3), than that producing hard cake, such as Koganemochi. The molar ratio of short chains (A+B1)/long chains (B2+B3), which is considered to be the number of chains comprising a cluster of amylopectin, was 10.1-11.7, being different among the varieties tested. The molar ratio determined by fluorescent response was much more reliable than the weight ratio determined by IR response because of the stable base line during HPLC. A negative correlation was found between the molar ratio and the hardening of rice cake. Therefore, the molar ratio (A+B1)/(B2+B3) of amylopectin unit-chains seemed to be one of useful evaluation/selection indexes for breeding of waxy rice. An index, or molar ratio, lower than 11 appeared to be suitable for processing use, and one higher than 11.5 for principal food use.

Genetic and Phenotypic Modifications of Hematopoietic Stem Cells in Response to Ionizing Radiation Exposure

Hematopoietic stem cells (HSC) constitute a rare population within the bone marrow (BM) which actively maintains continuous production of all mature blood cell-lineages throughout life. They are finely regulated to respond rapidly and specifically to modifications of the number of circulating cells or to environmental modifications such as radiation exposure. Although a marked sensibility to radiation exposure of these cells has been reported, little is known about the underlying mechanisms. To understand at the molecular level the cell-dependent IR response, phenotypical and transcriptional changes occurring in stem cells were monitored following exposure to total body irradiation at 2Gy, 3Gy, 6Gy, in a kinetic study from 1 hour up to 60 days. Different stem cell populations were isolated using combinations of surface molecules such as Lin-/low Sca+ C-Kit+ (LSK) with or without CD150+ and CD135+. Our results show that cells with this phenotype were completely eradicated 48h after radiation exposure. Microarray analysis showed that as early as 1 hour after radiation exposure stem cells elicit a specific damage response mostly triggered by the modulation of apoptotic genes. Many genes identified were never described before as playing a role in the IR response. Moreover, QT clustering of expression profiles and subsequent promoter analysis of co-clustered genes reveal several novel P53 co-regulated genes. The induction of these genes after radiation exposure was impaired in mutant mice deficient for P53. Two months after 3 Gy or 6 Gy TBI, the BM cellularity was back to normal but the percentage of LSK cells was reduced and the proportion of LSK subsets expressing CD150 and/or CD135 was modified in a dose-dependant manner. Moreover, HSC presented a major defect in their long-term reconstitution potential that aroused from a blockage in their differentiation potential. This blockage can be partially abrogated by the administration of thrombopoietin. Novel actors in this signalling pathway were identified and will be presented. These results demonstrate that irradiation, on the one hand, kill a vast majority of cycling cells in the BM by the early onset of genetic network of apoptotic genes, and on the other hand affect quiescent HSC in a cell-autonomous but reversible manner. Altogether our approach help producing a more complete knowledge of the molecular mechanisms of the stem cell radiation response by unraveling molecular networks and finding novel and specific molecules involved in this process. This information might facilitate the derivation of clinically useful targets for patient benefit.

On the reactivity of NO/N 2 mixtures with aluminum surfaces: A combined PM-IRRAS and QCM investigation

The interaction of NO, and the further reactivity of oxygen, with water-passivated aluminum surfaces are investigated for the first time by in situ polarization modulation infrared reflexion absorption spectroscopy (PM-IRRAS) coupled with quartz crystal microbalance (QCM). Chemical and quantitative complementary information are thus obtained. Exposure of water-passivated plane aluminum samples to NO/N 2 mainly results in the formation of nitrites, as identified by PM-IRRAS. O 2 hardly reacts with adsorbed nitrites in the absence of NO in the gaseous atmosphere. In contrast, the introduction of O 2 to a NO/N 2 mixture leads to the rapid transformation of nitrites to nitrates, both water-solvated and oxide-coordinated species. The fact that the transformation of nitrites to nitrates occurs only in the presence of NO and O 2 may suggest that nitrites react with gas phase NO 2 to form nitrates and NO. The evolution of the PM-IRRAS spectra of the Al surface with the composition of the gaseous phase is fully correlated to the mass uptake changes measured by QCM. From the PM-IRRAS and QCM measurements obtained during the same experiments, the ratio of the IR response coefficient of nitrates to that of nitrites (3) is reported for the first time.

The 2D IR Responses of Amide and Carbonyl Modes in Water Cannot Be Described by Gaussian Frequency Fluctuations

The two-dimensional (2D) IR spectral shapes seen for aqueous amide-I' or carbonyls having apparently single bands are not those predicted by Gaussian frequency fluctuations. Their population evolution exposes discrete distributions undergoing picosecond time scale exchange. The energy transfer to other modes provides a clear view of this underlying structure, which is largely attributed to exchanging water configurations. The results suggest new approaches to examine protein-bound water at the residue level.

Slower processes of the ultrafast photo-isomerization of an azobenzene observed by IR spectroscopy

The photo-induced trans– cis isomerization of the azobenzene derivative 4-nitro-4′-(dimethylamino)azobenzene in polar solution was studied by femtosecond UV/Vis and IR spectroscopy. The UV/Vis experiment reveals two excited state processes; the slower one (1 ps) is the internal conversion to the ground state. The ensuing spectral changes point to vibrational cooling of the nascent cis product and the recovered trans isomer. Judging from the UV/Vis experiment this ∼5 ps process seems to terminate the isomerization. The internal conversion and the cooling also find their manifestation in the IR experiment. In addition slower spectral changes lasting until ∼50 ps are detected. These slow IR responses are compared with the behavior of a non-isomerizing analogue, para- N, N-dimethyl-nitroaniline. An origin for this discrepancy is suggested and potential molecular processes causing the slow IR response are discussed.