Effects of C-H stretching excitation on the dynamics of the O(1D) + CHD3 → OH/OD + CD3/CHD2 reaction.

The vibrationally excited reaction O(1D) + CHD3(ν1 = 1) has been investigated by crossed-molecular-beam experiments with a time-sliced velocity map imaging technique. Detailed and quantitative information is extracted on the C-H stretching excitation effects on the reactivity and dynamics of the title reaction, with the help of preparation of C-H stretching excited CHD3 molecules by direct infrared excitation. Experimental results show that the vibrational stretching excitation of the C-H bond almost does not affect the relative contributions between different dynamical pathways for all product channels. For the OH + CD3 product channel, the vibrational energy of the C-H stretching excited CHD3 reagent is channeled exclusively into the vibrational energy of the OH products. The vibrational excitation of the CHD3 reactant changes the reactivities for the ground-state and umbrella-mode-excited CD3 channels very modestly, while it significantly suppresses the corresponding CHD2 channels. For the CHD2(ν1 = 1) channel, the stretching excited C-H bond of the CHD3 molecule acts almost as a pure spectator.

Detection of RAS gene mutation and its clinical significance in children with acute lymphoblastic leukemia. / å„¿ç«¥æ€¥æ€§æ·‹å·´ç»†èƒžç™½è¡€ç— ä¸­RASåŸºå› çªå˜çš„æ£€æµ‹åŠå ¶ä¸´åºŠæ„ä¹‰.

OBJECTIVES: To investigate the mutation rate of the RAS gene and its clinical significance in children with acute lymphoblastic leukemia. METHODS: A retrospective analysis was performed on the medical data of 120 children with newly diagnosed acute lymphoblastic leukemia, who were admitted to the Third Affiliated Hospital of Zhengzhou University from January 2015 to January 2020 and underwent next-generation sequencing. The clinical and molecular features were analyzed. The impact of RAS gene mutation on the overall survival rate was evaluated in these children. RESULTS: Among the 120 children, 35 (29.2%) had RAS gene mutation, 30 (25.0%) had KRAS gene mutation, and 5 (4.2%) had both NRAS and KRAS gene mutations. All NRAS mutations and 71% (25/35) of KRAS mutations were located at the 12th and 13th codons. RAS gene mutation was detected in 35 (33.3%) out of 105 children with B-lineage acute lymphoblastic leukemia, but it was not detected in those with acute T lymphocyte leukemia. Of all the children, 11 (9.2%) were lost to follow-up, and among the 109 children followed up, 16 (14.7%) died. The children with RAS gene mutation had a significantly lower 2-year overall survival rate than those without RAS gene mutation (P<0.05). The prognosis of children with RAS gene mutation combined with WT1 overexpression and WBC>50×109/L at diagnosis was worse (P<0.05). CONCLUSIONS: RAS gene mutation is commonly observed in children with B-lineage acute lymphoblastic leukemia and may have an adverse effect on prognosis.

Mapping partial wave dynamics in scattering resonances by rotational de-excitation collisions.

One of the most important parameters in a collision is the 'miss distance' or impact parameter, which in quantum mechanics is described by quantized partial waves. Usually, the collision outcome is the result of unavoidable averaging over many partial waves. Here we present a study of low-energy NO-He collisions that enables us to probe how individual partial waves evolve during the collision. By tuning the collision energies to scattering resonances between 0.4 and 6 cm-1, the initial conditions are characterized by a limited set of partial waves. By preparing NO in a rotationally excited state before the collision and by studying rotational de-excitation collisions, we were able to add one quantum of angular momentum to the system and trace how it evolves. Distinct fingerprints in the differential cross-sections yield a comprehensive picture of the partial wave dynamics during the scattering process. Exploiting the principle of detailed balance, we show that rotational de-excitation collisions probe time-reversed excitation processes with superior energy and angular resolution.

Experimental and theoretical investigation of resonances in low-energy NO-H2 collisions.

The experimental characterization of scattering resonances in low energy collisions has proven to be a stringent test for quantum chemistry calculations. Previous measurements on the NO-H2 system at energies down to 10 cm-1 challenged the most sophisticated calculations of potential energy surfaces available. In this report, we continue these investigations by measuring the scattering behavior of the NO-H2 system in the previously unexplored 0.4 cm-1-10 cm-1 region for the parity changing de-excitation channel of NO. We study state-specific inelastic collisions with both para- and ortho-H2 in a crossed molecular beam experiment involving Stark deceleration and velocity map imaging. We are able to resolve resonance features in the measured integral and differential cross sections. Results are compared to predictions from two previously available potential energy surfaces, and we are able to clearly discriminate between the two potentials. We furthermore identify the partial wave contributions to these resonances and investigate the nature of the differences between collisions with para- and ortho-H2. Additionally, we tune the energy spreads in the experiment to our advantage to probe scattering behavior at energies beyond our mean experimental limit.

Imaging the onset of the resonance regime in low-energy NO-He collisions.

At low energies, the quantum wave-like nature of molecular interactions results in distinctive scattering behavior, ranging from the universal Wigner laws near 0 kelvin to the occurrence of scattering resonances at higher energies. It has proven challenging to experimentally probe the individual waves underlying these phenomena. We report measurements of state-to-state integral and differential cross sections for inelastic NO-He collisions in the 0.2 to 8.5 centimeter-1 range with 0.02 centimeter-1 resolution. We studied the onset of the resonance regime by probing the lowest-lying resonance dominated by s and p waves only. The highly structured differential cross sections directly reflect the increasing number of contributing waves as the energy is increased. Only with CCSDT(Q) level of theory was it possible to reproduce our measurements.

Correlations in rotational energy transfer for NO-D2 inelastic collisions.

We present a combined experimental and theoretical study of state-to-state inelastic collisions between NO (X 2Π1/2, j = 1/2, f) radicals and D2 (j = 0, 1, 2, 3) molecules at collision energies of 100 cm-1 and 750 cm-1. Using the combination of Stark deceleration and velocity map imaging, we fully resolve pair-correlated excitations in the scattered molecules. Both spin-orbit conserving and spin-orbit changing transitions in the NO radical are measured, while the coincident rotational excitation (j = 0 → j = 2) and rotational de-excitation (j = 2 → j = 0 and j = 3 → j = 1) in D2 are observed. De-excitation of D2 shows a strong dependence on the spin-orbit excitation of NO. We observe translation-to-rotation energy transfer as well as direct rotation-to-rotation energy transfer at the lowest collision energy probed. The experimental results are in good agreement with cross sections obtained from quantum coupled-channels calculations based on recent NO-D2 potential energy surfaces. The observed trends in the correlated scattering cross sections are understood in terms of the NO-D2 quadrupole-quadrupole interaction.

Associative desorption of hydrogen isotopologues from copper surfaces: Characterization of two reaction mechanisms.

We report quantum-state resolved measurements of angular and velocity distributions of the associative desorption of H2, HD, and D2 from Cu(111) and Cu(211) surfaces. The desorbing molecules have bimodal velocity distributions comprising a "fast" channel and a "slow" channel on both facets. The "fast channel" is promoted by both hydrogen incidence translational and vibrational energy, while the "slow channel" is promoted by vibrational energy but inhibited by translational energy. Using detailed balance, we determine state-specific reaction probabilities for dissociative adsorption and compare these to theoretical calculations. The results for the activation barrier for the "fast channel" on Cu(111) are in agreement with theory within "chemical accuracy" (1 kcal/mole). Results on the Cu(211) facet provide direct information on the effect of increasing step density, which is commonly believed to increase reactivity. Differences in reactivity on the (111) and (211) facets are subtle - quantum state specific reactivity on the (211) surface is characterized by a broader distribution of barrier heights whose average values are higher than for reaction on (111). We fully characterize the "slow channel," which has not been found in theoretical calculations although it makes up a large fraction of the reactivity in these experiments.

[Expression of CC-chemokine Receptor 7 in Patiens with Multiple Myeloma and Its Relationship with Extramedullary Disease].

OBJECTIVE: To investigate the expression of CC-chemokine receptor 7(CCR7) in patients with multiple myeloma(MM) and its correlation with clinical features of MM. METHODS: The level of CCR7 expression in bone marrow samples from 53 newly diagnosed MM patients was detected by flow cytometry(FCM). Statistical methods were used to analyze the correlation between CCR7 expression and clinical features, such as sex, age, M protein, peripheral blood cell count, biochemical indicators, plasma cell ratio of bone marrow, immunophenotype, osteopathy and extramedullary disease. RESULTS: The plasma cells in 24 out of 53 cases(45.28%) expressed CCR7. The rate of extramedullary disease in CCR7 positive group was significantly higher than that in CCR7 negative group (29.17% vs 3.45%)(P<0.05). CONCLUSION: The expression of CCR7 in patients with MM is high, moreover this high expression correlates with extramedullary disease, thus CCR7 can be used as an effective indicator for prediction of extramedullary disease.

Evidence for Electron-Hole Pair Excitation in the Associative Desorption of H2 and D2 from Au(111).

The dissociative adsorption reaction of hydrogen on noble metals is believed to be well-described within the Born-Oppenheimer approximation. In this work, we have experimentally derived translational energy distributions for selected quantum states of H2 and D2 formed in associative desorption reactions at a Au(111) surface. Using the principle of detailed balance, we compare our results to theory carried out at the same level of sophistication as was done for the reaction on copper. The theory predicts translational excitation that is much higher than is seen in experiment and fails to reproduce the experimentally observed isotope effect. The large deviations between experiment and theory are surprising because, for the same reactions occurring on Cu(111), a similar theoretical strategy agreed with experiment, yielding "chemical accuracy". We argue that electron-hole pair excitation is more important for the reaction on gold, an effect that may be related to the reaction's later transition state.

[Expression and Clinical Significance of CC-chemokine Receptor 7 in Adult Acute Leukemia].

OBJECTIVE: To explore the expression of CC-chemokine Receptor 7 (CCR7) in adult acute leukemia patients, and to analyze the relationship of CCR7 expression with the clinical characteristics of patients. METHODS: The expression of CCR7 in bone marrow samples from adult acute leukemia patients were detected by flow cytometry (FCM), the relationship of CCR7 expression with the clinical characteristics of patients such as sex, age, WBC count, blast cell ratio, CD56 expression, molecular biology, cell genetics, risk stratification, extramedullary infiltration was analyzed. RESULTS: The expression rate of CCR7 in adult ALL and AML patients was 36.8% and 9.6%, respectively, and the expression level of CCR7 in ALL patients was higher than that in AML patients (P < 0.05). The extramedullary infiltration rate was 100% and 41.7 % for CCR7 positive and negative groups of ALL, respectively (P < 0.05). While the mean fluorescence intensity (MFI) in extramedullary infiltration group of ALL was higher than that in none-extramedullary infiltration group of ALL (50.00 ± 10.42 vs 18.14 ± 1.39), respectively (P < 0.05). CONCLUSION: CCR7 is higher expressed in adult acute leukemia cells, moreover its expression rate in ALL is higher than that in AML, and the expression of CCR7 is related with extramedullary infiltration in ALL.

Velocity map imaging study of the reaction dynamics of the H + CH4 → H2 + CH3 reaction: the isotope effects.

Following our previous study on the H + CD4 → HD + CD3 reaction [ Proc. Natl. Acad. Sci. U.S.A. 2010 , 107 , 12782 ], the reaction of H + CH4 → H2 + CH3 at collision energies ranging from 0.72 to 1.99 eV is studied using crossed-beam and time-sliced velocity map ion imaging techniques. The product angular and translational energy distributions at four different collision energies were derived from the measured images. The excitation function was also measured from these images together with a careful calibration of the H atom beam intensities at different collision energies. All of these results are compared with those of the H + CD4 reaction to investigate the isotope effects. The isotope effects are all observed in the product angular distributions, the translational energy distributions, and the excitation function and further confirm the reaction mechanism proposed in the previous study on the H + CD4 reaction.

Trapped Abstraction in the O((1)D) + CHD3 → OH + CD3 Reaction.

Despite significant progress made in past decades, it is still challenging to elucidate dynamics mechanisms for polyatomic reactions, in particular, involving complex formation. The reaction of O((1)D) with methane has long been regarded as a prototypical polyatomic system of direct insertion reaction in which the O((1)D) atom can insert into the C-H bond of methane to form a "hot" methanol intermediate before decomposition. Here, we report a combined theoretical and experimental study on the O((1)D) + CHD3 reaction, on which good agreement between theory and experiment is achieved. Our study revealed that this complex-forming reaction actually proceeds via a trapped abstraction mechanism, rather than an insertion mechanism as has long been thought. We anticipate that this reaction mechanism should also be responsible for the reaction of O((1)D) with ethane and propane, as well as many other chemical reactions with deep wells in the interaction region.

Imaging the O(1D) + CD4 → OD + CD3 reaction dynamics: probing vibrationally and rotationally excited CD3 products.

The dynamics of the O((1)D) + CD(4) → OD + CD(3) reaction has been studied using the crossed molecular beam technique with sliced velocity map imaging. Internally excited CD(3) products were detected using a (2+1) resonance-enhanced multiphoton ionization with state resolution. Dual reaction mechanisms, insertion and abstraction, were only observed for CD(3) products with its umbrella mode (v(2)) excited or in its ground state, while CD(3) products with other vibrational mode excited do not show any evidence of contributions from the abstraction pathway. Experimental results indicate that even though the insertion channel dominates the reaction, the abstraction channel contributes relatively more to vibrationally excited CD(3) products. The state-to-state correlation between the two reaction products, OD and CD(3), was determined for the abstraction channel at different collision energies. In addition, we measured rotationally hot CD(3) products and found that these products are only produced via the insertion channel.

Imaging the O((1)D) + CD4 → OD + CD3 Reaction Dynamics: The Threshold of Abstraction Pathway.

The O((1)D) + CD4 → OD + CD3 reaction was investigated using the crossed molecular beam technique with sliced velocity map imaging at four different collision energies: 1.6, 2.8, 4.6, and 6.8 kcal/mol. The vibrational ground state product CD3 was detected using a (2 + 1) resonance-enhanced multiphoton ionization (REMPI). Remarkably different features were found in the forward and backward scatterings, and gradually changed with the collision energy. These features were attributed to two distinctive reaction mechanisms-insertion and abstraction-that occur on the ground and excited state surfaces, respectively. Contributions from the two mechanisms were extracted from the experiment results, and a positive correlation was found between the abstraction proportion and the collision energy. The threshold for the abstraction pathway was determined and compared with results from calculations.

Imaging CH3SH photodissociation at 204 nm: the SH + CH3 channel.

The SH + CH(3) product channel for the photodissociation of CH(3)SH at 204 nm was investigated using the sliced velocity map ion imaging technique with the detection of CH(3) products using state selective (2+1) resonance enhanced multiphoton ionization (REMPI). Images were measured for CH(3) formed in the ground and excited vibrational states (v(2) = 0, 1, and 2) of the umbrella mode from which the correlated SH vibrational state distributions were determined. The vibrational distribution of the SH fragment in the SH + CH(3) channel at 204 nm is clearly inverted and peaks at v = 1. The highly negative anisotropy parameter of the CH(3) (v(2) = 0, 1, and 2) products is indicative of a fast dissociation process for C-S bond cleavage. Two kinds of slower CH(3) products were also observed (one of which was partly vibrationally resolved) that are assigned to a two-step photodissociation processes, in which the first step is the production of the CH(3)S (X(2)E) radical via cleavage of the S-H bond in CH(3)SH, followed by probe laser photodissociation of nascent CH(3)S radicals yielding CH(3)(X(2)A(1), v(2) = 0-2) + S((3)P(j)/(1)D) products.

Communication: Experimental and theoretical investigations of the effects of the reactant bending excitations in the F + CHD3 reaction.

The effects of the reactant bending excitations in the F+CHD(3) reaction are investigated by crossed molecular beam experiments and quasiclassical trajectory (QCT) calculations using a high-quality ab initio potential energy surface. The collision energy (E(c)) dependence of the cross sections of the F+CHD(3)(v(b)=0,1) reactions for the correlated product pairs HF(v('))+CD(3)(v(2)=0,1) and DF(v('))+CHD(2)(v(4)=0,1) is obtained. Both experiment and theory show that the bending excitation activates the reaction at low E(c) and begins to inactivate at higher E(c). The experimental F+CHD(3)(v(b)=1) excitation functions display surprising peak features, especially for the HF(v(')=3)+CD(3)(v(2)=0,1) channels, indicating reactive resonances (quantum effects), which cannot be captured by quasiclassical calculations. The reactant state-specific QCT calculations predict that the v(5)(e) bending mode excitation is the most efficient to drive the reaction and the v(6)(e) and v(5)(e) modes enhance the DF and HF channels, respectively.

Depression of reactivity by the collision energy in the single barrier H + CD4 -> HD + CD3 reaction.

Crossed molecular beam experiments and accurate quantum scattering calculations have been carried out for the polyatomic H + CD(4) --> HD + CD(3) reaction. Unprecedented agreement has been achieved between theory and experiments on the energy dependence of the integral cross section in a wide collision energy region that first rises and then falls considerably as the collision energy increases far over the reaction barrier for this simple hydrogen abstraction reaction. Detailed theoretical analysis shows that at collision energies far above the barrier the incoming H-atom moves so quickly that the heavier D-atom on CD(4) cannot concertedly follow it to form the HD product, resulting in the decline of reactivity with the increase of collision energy. We propose that this is also the very mechanism, operating in many abstraction reactions, which causes the differential cross section in the backward direction to decrease substantially or even vanish at collision energies far above the barrier height.

Crossed molecular beam ion-imaging study of the Cl + SiH4 --> HCl + SiH3 reaction: product vibrational state-to-state correlation.

The dynamics of the Cl + SiH(4) --> HCl + SiH(3) reaction has been studied using the crossed molecular beam technique with slice imaging. The ion images of the silyl radical (SiH(3)) product from the Cl + SiH(4) reaction were recorded at different collision energies, using the (2 + 1) resonance enhanced multi-photon ionization (REMPI) technique. The product velocity and angular distributions of this reaction were determined from the recorded images. The vibrational state-to-state correlation of the relative population between the two reaction products, SiH(3) and HCl, was also determined. Finally, the Cl + SiH(4) results are compared with that of the F + SiH(4) reaction.

Product vibrational state-to-state correlation in the F + SiH4 --> HF(v(HF)) + SiH3 (0v20) reaction: a crossed molecular beam ion-imaging study.

The dynamics of the F + SiH(4) --> HF + SiH(3) reaction has been studied using the crossed molecular beam technique with slice imaging at collision energies from 1.25 to 8.17 kcal/mol. The product silyl radical, SiH(3)(v(2) = 0-5), was detected using the (2 + 1) resonance enhanced multiphoton ionization technique. The product velocity distributions and angular distributions of this reaction were obtained from the recorded images. Experimental results show that the silyl radical product is mainly forward scattered relative to the silane beam direction, and the majority of the available energy was partitioned into the vibration of the HF product. The state-to-state correlation between the two reaction products, SiH(3) and HF, was also determined. In addition, we found that the reaction cross section goes down as the collision energy increases. From these results, we conclude that the F + SiH(4) --> HF + SiH(3) reaction proceeds through a direct abstraction mechanism with little or no reaction barrier.