Heavy Fragments Research Articles

A Computationally Guided Approach to Improve Expression of VHH Binders

The variable heavy chain fragments derived from camelid antibodies, called VHHs or nanobodies, have recently shown promise as high-affinity reagents. They offer higher stability compared to conventional antibodies and fragments thereof. Furthermore, their smaller size (~15–20 kDa) allows better targeting of molecules localized inside the cell and in crowded environments, like tissues and protein aggregates. Despite these advantages, nanobody clones screened using phage display can suffer from poor soluble expression, which we hypothesized is due to the presence of hydrophobic hotspots on their surface. In this work, we propose a novel, computationally guided workflow for screening and production of nanobody binders for optimized expression. After an initial round of phage display screens against our target (K-Ras), we modeled the lead candidates to generate spatial aggregation propensity (SAP) maps to highlight the hydrophobic hotspots with single amino acid resolution, which were subsequently used to guide mutagenesis of the binders for soluble expression. We followed two approaches to perform point hydrophilic mutations: (i) performing point hydrophilic mutations in the hydrophobic hotspots; (ii) combining point mutation resulting from a round of random mutagenesis that show favorable SAP scores. Both approaches led to a remarkable increase in soluble expression, which allowed production and characterization of their binding to their target (K-Ras) on soluble ELISA and biolayer interferometry. We observed that the latter approach resulted in clones with stronger binding affinity compared to the former approach. Our results emphasize the need to perform a round of random mutagenesis to identify point mutations, which can then be used in an in silico guided pipeline to identify the right combination of mutations for high soluble expression.

X-ray-Induced Molecular Catapult: Ultrafast Dynamics Driven by Lightweight Linkages.

In our work, we demonstrate that X-ray photons can initiate a "molecular catapult" effect, leading to the dissociation of chemical bonds and the formation of heavy fragments within just a few femtoseconds. We reconstruct the momenta of fragments from a three-body dissociation in bromochloromethane using the ion pair average (IPA) reference frame, demonstrating how light atomic groups, such as alkylene and alkanylene, can govern nuclear dynamics during the dissociation process, akin to projectiles released by a catapult. Supported by ab initio calculations, this work highlights the crucial role of low-reduced-mass vibrational modes in driving ultrafast chemical processes.

An anti-Shiga toxin VHH nanobody multimer protects mice against fatal toxicosis when administered intramuscularly as repRNA.

Hemolytic uremic syndrome (HUS) is a systemic sequelae from gastrointestinal infection with Shiga toxin (Stx) producing Escherichia coli (STEC) that can result in acute kidney injury, lasting renal disease, and death. Despite a window for intervention between hemorrhagic diarrhea and onset of HUS, no specific therapies exist to prevent or treat HUS following STEC infection. Furthermore, there is no way to predict which patients with STEC will develop HUS or any rapid way to determine which Stx variant is present. To address this, we have broadened the therpay to neutralize additional toxin variants. It contains a multimer of nanobodies derived from camelid heavy chain antibody fragments (VHHs). An improved VHH-based neutralizing agent (VNA2) is delivered intramuscularly as RNA combined with LION nanoparticles rather than mRNA, that replicates on administration (repRNA), resulting in a rapidly circulating VNA that can bind systemic toxin. The RNA/VNA2-Stx administered intramuscularly prevents toxicity and death in a mouse model of acute Stx toxicity.

Engineering and physicochemical characterization of a novel, stable, symmetric bispecific antibody with dual target-binding using a common light chain.

Bispecific antibodies (BsAbs) have emerged as a major class of antibody therapeutics owing to their substantial potential in disease treatment. While several BsAbs have been successfully approved in recent years, ongoing development efforts continue to focus on optimizing various BsAbs tailored to particular antigens and action mechanisms, aiming to achieve favorable physicochemical properties. BsAbs generally encounter challenges due to their unfavorable physicochemical characteristics and poor manufacturing efficiencies, highlighting the need for optimization to achieve reliable productivity and developability. Herein, we describe the development of a novel symmetric BsAb, REGULGENT™ (N-term/C-term), comprising two Fab domains, using a common light chain. The heavy chain fragment encoded two antigen-binding determinants in one chain. The design and production of REGULGENT™ (N-term/C-term) are simple owing to the use of the same light chain, which does not induce heavy and light chain mispairing, frequently observed with the asymmetric BsAb format. REGULGENT™ (N-term/C-term) exhibited high expression and low aggregation characteristics during cell culture and stress treatment under low pH conditions. Differential scanning calorimetric data indicated that REGULGENT™ molecules had high conformational stability, similar to that of stabilized monoclonal antibodies. Surface plasmon resonance data showed that REGULGENT™ (N-term/C-term) could bind to two antigens simultaneously and exhibited a high affinity for two antigens. In summary, the symmetric BsAb format of REGULGENT™ confers its desirable IgG-like physicochemical properties, thus making it an excellent candidate for commercial development. The findings demonstrate a novel BsAb with substantial development potential for clinical applications.

Total excitation energy distribution for neutron-induced fission and photo-fission of uranium isotopes

The fission fragment total excitation energy, TXE(A), is investigated for neutron-induced fission of uranium isotopes using three different methods. Different methods for calculations of the TXE(A) produced by the decay of low excited systems are analyzed and their results are compared with the available TXE values. The calculated TXE values have been compared with the results of other studies for the neutron induced fission of 233U, 235U as well as the photo-fission of 238U. The scission point method for evaluating TXE has been modified by comparing the available and calculated results. TXE(A) is evaluated for other uranium isotopes using three methods. It is found that TXE values in the neutron induced fission of 233U, 235U and the photo-fission of 238U are greater than the calculated TXE values of other uranium isotopes. The TXE values of light uranium isotopes decrease with increasing their mass numbers, while the TXE values of heavy uranium isotopes increase as their mass numbers increase. Also, the calculated TXE values for all isotopes increase sharply near the symmetric region, which is due to the formation of unstable fission fragment. On the other hand, a slight increase in neutron multiplicity and TXE values can be observed in heavy fission fragments (Ah>155), which could be due to the neutron excess. However, the sharp increase in neutron multiplicity and TXE values in some studies for the heavy fission fragments (Ah>155) is due to a missing correction in the data analysis.

Abstract PO4-06-08: ZP4 AS A NOVEL TARGET FOR CAR T CELL THERAPY IN TRIPLE NEGATIVE BREAST CANCER

Abstract Triple negative breast cancer (TNBC) has the worst prognosis of BC subtypes, largely due to lack of approved targeted therapies. Chimeric antigen receptor (CAR) T cells have demonstrated great success in certain hematological malignancies; however, in the treatment of solid cancers, CAR T cells are faced with a variety of obstacles that limit their efficacy, including on-target/off-tumor toxicity. To minimize these toxicities, the ideal CAR T cell target must be overexpressed by the tumor and absent from vital organs. Cancer/germline (CG) antigens satisfy this need, as their expression is restricted to male or female germ cells. Using a bioinformatic pipeline to identify novel CG antigens expressed in TNBC and other solid cancers, we have identified zona pellucida glycoprotein 4 (ZP4) as a candidate CG antigen target for CAR T cell therapy. This protein is a component of the human zona pellucida matrix, an extracellular structure that surrounds the oocyte and functions in folliculogenesis, species-specific fertilization, and early development. We have identified ZP4 expression in approximately 10% of TNBC cases from available RNAseq and proteomic databases and have confirmed ZP4 expression in several TNBC PDX models. The overall purpose of this study is to redirect T cells against ZP4 by engineering and validating a second generation ZP4-specific CAR. We have generated a library of monoclonal antibody (mAb) candidates against the extracellular portion of human ZP4. Antibody clones were screened, and their specificity validated via ELISA and flow cytometry, and the three strongest binders (z108, z128, and z164) were selected for further investigation. By IHC, we confirmed that the ZP4 mAb clones stained the area surrounding normal oocytes and did not show binding to any of the 23 normal tissues screened. The variable regions of the antibody heavy and light chains were sequenced using 5’RACE and used to assemble second generation CAR constructs composed of the variable heavy and light chain fragments separated by a linker, a CH2/CH3 hinge domain, a CD28 transmembrane domain, a CD28 co-stimulatory domain, and the CD3z signaling domain. Activated T cells transduced with retroviral supernatant express the ZP4 CAR constructs at high levels. While all ZP4 CAR T cells demonstrate antigen-specific cytotoxic killing of ZP4+ target tumor cells in short-term in vitro assays, z128 ZP4 CAR T cells demonstrate superior persistence and efficacy in long-term repeat tumor challenge in vitro assays and orthotopic in vivo mouse models. In summary, ZP4 is a promising target for TNBC and we have successfully engineered ZP4 specific CAR T cells. ZP4 CAR T cells effectively target and kill ZP4+ cells in in vitro cytotoxicity assays but perform differently in repeat tumor challenge assays and in vivo. Future studies will elucidate the precise differences between our three candidate CAR constructs and further test the effector function, trafficking, proliferation, and persistence of z128 ZP4 CAR T cells in vivo using ZP4+ PDX models. This work has exciting potential to bring a novel CAR T cell therapy to patients with TNBC, without concerns for on-target off-tumor toxicity. Citation Format: Lauren Somes, Jonathan Lei, Paul Shafer, Xinpei Yi, Diego Chamorro, Emily Madaras, Michael Lewis, Bing Zhang, Valentina Hoyos. ZP4 AS A NOVEL TARGET FOR CAR T CELL THERAPY IN TRIPLE NEGATIVE BREAST CANCER [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO4-06-08.

Heavy quark transverse momentum dependent fragmentation

In this paper, we investigate the heavy quark (HQ) mass effects on the transverse momentum dependent fragmentation function (TMDFF). We first calculate the one-loop TMDFF initiated by a heavy quark. We then investigate the HQ TMDFF in the limit where the transverse momentum, q⊥ is small compared to the heavy quark mass, q⊥ ≪ m and also in the opposite limit where q⊥ ≫ m. As applications of the HQ TMDFF, we study the HQ transverse momentum dependent jet fragmentation function, where the heavy quark fragments into a jet containing a heavy hadron, and we investigate a heavy hadron’s transverse momentum dependent distribution with respect to the thrust axis in e+e− collisions.

Abstract 2606: Targeting mesothelin on tumor cells with a novel, completely human fusion construct delivering the serine protease granzyme B

Abstract Mesothelin is a cell-surface antigen identified as an excellent cancer-associated target upregulated on numerous tumors, including pancreatic and ovarian cancers, as well as mesotheliomas and lung cancers. Granzyme B is a highly cytotoxic serine protease nominally delivered by immune effector cells to target cells, resulting in induction of cell death pathways that are both caspase-dependent and -independent. We developed a fusion protein (GrB-Fc-SD1) composed of GrB and containing SD1, a novel human single-domain antibody that uniquely targets Region III of the mesothelin glycoprotein. The SD1 and GrB domains are tethered by a human IgG heavy chain fragment which enables dimerization. The fusion protein was transiently expressed in HEK-293E cells in serum-free conditions with a final yield of 5 mg/L. Western blot analysis confirmed the expression of this construct as a homodimer. The GrB enzymatic activity in GrB-Fc-SD1 was similar to that of commercially available human granzyme B. ELISA studies confirmed the specific recognition of the SD1 antibody to mesothelin extra-cellular domain. Biacore analysis confirmed binding of GrB-Fc-SD1 with a dissociation constant between 10−7 and 10−8 M. In vitro cytotoxicity against a limited panel of lung, pancreatic and ovarian cancer cell lines expressing surface mesothelin indicate cytotoxicity in the nanomolar range, while cytotoxicity against mesothelin-negative cells was at micromolar levels. Ex vivo serum stability studies showed excellent stability of GrB-Fc-SD1 at both 4°C and -20°C over ninety days and a half-life of approximately three days at elevated temperatures (37°C). In vivo efficacy studies against Capan-2 xenografts in nude mice using both weekly x 5 and QOD x 5 doses of GrB-Fc-SD1 (130 mg/mg total dose, delivered IP) indicated highly significant efficacy in both dose regimens, with p < 0.001 compared to vehicle-treated mice. Mouse body weights were not impacted at the efficacy doses used in this study, indicating that this dose was non-toxic. Histopathology studies revealed a significant decrease in the percentage of Ki-67+ nuclei in treated tumors compared to controls. These data warrant continued investigation of the protein as a therapeutic candidate. Research supported by H2Biologics. Research conducted, in part, by the Clayton Foundation for Research. Citation Format: Khalid A. Mohamedali, Lawrence H. Cheung, Mihai G. Iurascu, Louis R. DePalatis, Claire Thuning-Roberson, Michael G. Rosenblum. Targeting mesothelin on tumor cells with a novel, completely human fusion construct delivering the serine protease granzyme B [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 2606.

Abstract 1860: The smallest antibody class: Cow ultralong CDR3 knobs as a new class of biomolecule for therapeutics and diagnostics

Abstract Engineered antibodies, including bispecifics and ADCs, are now a major drug class for oncology and other therapeutic areas. There are two fundamental antibody fragments: the Fv (heavy and light chain variable region fragments, derived from most species), and VHH (heavy chain ‘only’ V regions, derived from camelids and sharks). Cows produce antibodies with an unusually long VH CDR3 region, which can be up to seventy amino acids in length and is comprised of a β-ribbon “stalk” and disulfide-bonded “knob” minidomain which sits atop the stalk. The knob region is highly diverse and can bind cryptic epitopes with high affinity. We recently developed the technology to produce knob domains independently of the antibody, and at ~5 kDa are the smallest functional antibody fragment (https://doi.org/10.1073/pnas.2303455120). The high stability and small size could enable improved tissue penetration and development of novel therapeutics, including knob-drug conjugates or extremely small bispecific molecules. Citation Format: Vaughn Smider. The smallest antibody class: Cow ultralong CDR3 knobs as a new class of biomolecule for therapeutics and diagnostics [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 1860.

Abstract 5974: Targeting VEGFR on tumor cells and activated vasculature through delivery of granzyme B

Abstract Anti-VEGF therapy is a key therapeutic in several cancer treatment regimens. However, none of the current therapeutics are directly cytotoxic against tumor cells. VEGF121 is the smallest isoform in the VEGF-A family of cytokines that binds to VEGF receptors R-1 and R-2. Both receptors are over-expressed on several tumor cells and the endothelium of tumor vasculature but not normal vasculature. We hypothesized that delivery of a cytotoxic payload through VEGFR-2 into tumor cells and tumor neovasculature would significantly enhance cancer therapy. Granzyme B is a key effector in immune-mediated cell killing through both caspase-dependent and -independent mechanisms. We previously reported the development of a fusion protein composed of granzyme B (GrB) and VEGF121 (GrB/VEGF121). Here, we report on GrB-Fc-VEGF121, a fusion protein incorporating a human IgG heavy chain Fc fragment for dimerization to increase the molecular weight and improve in vivo circulation and targeting potential. We expressed and purified GrB-Fc-VEGF121 from HEK-293E cells under serum-free conditions with a final yield of approximately 40 mg/L. The enzymatic activity of GrB in GrB-Fc-VEGF121 was comparable to that of commercially available human GrB. We characterized this construct against both human and mouse VEGFR+ cell lines as this ligand cross-reacts to both species. GrB-Fc-VEGF121 showed in vitro cytotoxicity in the nanomolar range against tumor and endothelial cell lines expressing high levels of VEGFR-1 or VEGFR-2, while receptor-negative cells demonstrated IC50 levels in the high micromolar range. GrB-Fc-VEGF121 internalized into VEGFR-2+ tumor and endothelial cells within 2 hours of treatment while untargeted GrB did not internalize, suggesting internalization was receptor-mediated. Treatment of VEGFR2+ cells at the respective IC50 dose resulted in >50% cell death via apoptosis and/or necrosis within 48 h. Ex vivo serum stability studies indicated a gradual protein loss of GrB-Fc-VEGF121 with an overall stability of about 50% over 96 hours. No toxicity was observed in mice treated with a total dose of 475 mg/kg (IP, QOD x 5), indicating that the maximum tolerated dose of GrB-Fc-VEGF121 exceeds this dose level. In vivo efficacy studies in an OVCAR8 tumor xenograft model (20 mg/kg GrB-Fc-VEGF121 x 5) resulted in significant growth inhibition of established tumors compared to vehicle controls. The number of CD31+ blood vessels and Ki-67+ proliferating tumor cells decreased significantly in treated tumors compared to controls. Pharmacokinetic studies are underway and will be reported. Thus, GrB-Fc-VEGF121 significantly reduces tumor growth in vivo with no observed toxicity against normal tissues. This tumor- and vascular-targeting agent appears to have significant potential as a new class of targeted therapeutic agents with a unique mechanism of action. Research conducted, in part, by the Clayton Foundation for Research. Citation Format: Khalid A. Mohamedali, Lawrence H. Cheung, Ana Alvarez-Cienfuegos, Walter N. Hittelman, Michael G. Rosenblum. Targeting VEGFR on tumor cells and activated vasculature through delivery of granzyme B [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 5974.

Angular momentum in fission fragments

We suggest that the angular momentum in fission fragments is generated by statistical excitation at scission. The magnitude of the angular momentum is determined by excitation energy and shell structure in the level density. Treating the prescission shape evolution as a diffusive process, implemented as a Metropolis walk on a five-dimensional potential-energy surface, the average magnitudes of the fission fragment angular momenta are calculated for U235(nth,f), assuming that they are perpendicular to the fission axis. The sawtooth behavior of the average angular momentum magnitude as function of mass number is discussed in connection with the similar observed behavior of the average neutron multiplicity, and a good understanding is achieved. The magnitudes of the angular momenta of light and heavy fragments are found to have a weak negative correlation, in accordance with recent experimental results. This correlation arises from the microcanonical sharing of excitation energy by the fragments at scission, where each energy provides a distribution of angular momenta. Published by the American Physical Society 2024

Total kinetic, excitation energy and neutron multiplicity distribution of californium isotopes

The mean total kinetic energy as a function of fission fragments, <TKE>(A), is calculated for neutron-induced fission of 247,249,251,253,255Cf, as well as for spontaneous fission of 248,250,252,254Cf using the scission point model. A comparative analysis is performed between the calculated results and existing experimental data. Investigation into the behavior of <TKE>(A) is conducted, particularly focusing on intermediate and heavy actinides. While nuclear and Coulomb energy evaluations suffice for estimating <TKE> values in light actinides, this approximation proves inadequate for evaluating TKE values for intermediate and heavy actinides. Additionally, an evaluation is made of the total excitation energy as a function of fission fragments, <TXE>(A), concerning spontaneous fission in 247−254Cf. It is found that TXE values sharply increase near the symmetric region across all isotopes and exhibit a gradual increase in heavy fission fragments. Furthermore, an exploration of the total neutron multiplicity as a function of fission fragments, νT(A), is conducted for 252Cf fission using two methods. The νT(A) results obtained through these methods are compared with experimental data, and νT(A) is estimated for unmeasured californium isotopes. The average neutron emission per fission event, ν¯(Ai), is then calculated for spontaneous fission of 251Cf and 253Cf, yielding values of 3.46 and 3.59, respectively.

Sequential decay analysis of $^{235}$U(n$^{th}$,f) reaction using fragmentation approach

Abstract Numerous experimental and theoretical observations conclude that the probability of the three fragment emission (ternary fission) or the binary fission increases when one proceeds towards the heavy mass region of nuclear periodic table. The collinear cluster tripartition (CCT) channel of $^{235}$U(n$^{th}$,f) reaction is studied and it was observed that the CCT may be a sequential process or a simultaneous emission phenomena. Till now, different approaches are introduced to study the CCT process as a simultaneous process or sequential process, but the decay dynamics of these modes is not fully explored. It will be of interest to identify the three fragments of the sequential process and to explore their related dynamics using some excitation energy dependent approach. Hence, in present work, an attempt is made to study the sequential decay mechanism of $^{235}$U(n$^{th}$,f) reaction using quantum mechanical fragmentation theory (QMFT). The decay mechanism is considered in two steps, where initially the nucleus splits into an asymmetric channel. In the second step, the heavy fragment obtained in the first step divides into two fragments. Stage I analysis is done by calculating the fragmentation potential and the preformation probability for the spherical and deformed choice of the decaying fragments. The most probable fragment combination of stage I are identified in view the dips in the fragmentation structure, and the corresponding maxima's of the preformation probability ($P_0$). The excitation energy of the decay channel is calculated using an iteration process. The obtained excitation energy of the identified heavy fragments is further used for the fragmentation analysis, and the subsequent binary fragments of the sequential process are obtained. The identified three fragments of the sequential process are in agreement with the experimental observation and are found nearby the neutron or proton shell closure. Finally, the kinetic energy of the observed fragments is calculated and the middle fragment of the CCT mechanism is identified.

The contribution of high-LET track to DNA damage formation and cell death for Monoenergy and SOBP carbon ion irradiation

Carbon ion radiotherapy (CIRT) is a heavy ion charge particle therapy with 29 years of prominent use. Despite advantages like high relative biological effectiveness (RBE), improved quality of life, and reduced treatment time, challenges persist, especially regarding heavy nuclear fragments. Our research addresses these challenges in horizontal irradiation, aiming to comprehend Monoenergetic and Spread-Out Bragg peak (SOBP) carbon ion beam trajectories using cell survival analysis and visualizing biological effects through DNA damage (γ-H2AX). This reveals repair-related protein foci near the Bragg peak. CR-39, a plastic nuclear track detector, was explored to understand high-linear energy transfer (LET) tracks and radiation quality near the Bragg peak. Findings unveil high-LET DNA damage signatures through aligned γ-H2AX foci, correlating with LET values in SOBP. CR-39 visualized high-LET particle exposure, indicating comet-type etch-pits at the Bragg peak and suggesting carbon ion fragmentation. Unexpectedly, dot-type etch-pits in irradiated and post-Bragg peak regions indicated high-LET neutron production. This investigation highlights the intricate interplay of carbon ion beams, stressing the importance of understanding LET variations, DNA damage patterns, and undesired secondary exposure.

Characteristics of the fission fragments in the three-body model of binary fission

The evaluated nuclide yields, fragment mass and charge distributions, and averaged total kinetic energy of fission fragments for the neutroninduced fission of 30 actinide nuclei are well described in the new model, which considers the fissioning scission system consisting of two heavy fragments and an α-particle between them. The α-particle has its origin in the neck nucleons. The yield of fission fragments in the model is linked to the number of states over the barrier of the saddle point, which is between the contacting and well-separated fission fragments. The α-particle is fused with the nearest heavy fragment after passing the saddle point, therefore, two final fragments appear during fission. The quadrupole deformations of heavy fragments are taken into account in the model. The fragment yields depend on the heights of corresponding saddle points and the values of the equilibrium quadrupole deformation of fragments.

Sequential fission and the influence of 208Pb closed shells on the dynamics of superheavy element synthesis reactions

Measured binary quasifission mass spectra in reactions with actinide nuclides show a large peak in yield near the doubly-magic 208Pb, generally attributed to enhanced binding energy causing a valley in the potential energy surface, which attracts quasifission trajectories. Measurements of binary quasifission mass spectra and cross-sections have been made for reactions of 50Ti with actinide nuclides from 232Th to 249Cf. Cross-sections have also been deduced for sequential fission (a projectile-like nucleus and two fragments from fission of the complementary target-like nucleus). Binary cross-sections fall from 70% of calculated capture cross-sections for 232Th to only 40% for 249Cf, with a compensating increase in sequential fission cross-sections. The data are consistent with the peak in yield near 208Pb originating largely from sequential fission of heavier fragments produced in more mass-asymmetric primary quasifission events. These are increasingly suppressed as the heavy quasifission fragment mass increases above 208Pb. The important role of sequential fission calls for re-interpretation of quasifission observables and dynamics in superheavy element synthesis reactions.

Analysis of the kinetic energy from fission fragments using dynamical model

It is known that the kinetic energy of individual fragments for fission of actinides is constant at about 100 MeV for light fragments and that for heavy fragments decreases with mass number. The kinetic energy is, for example, important for evaluating the prompt-neutron spectrum in the laboratory system. However, its theoretical study has not been attempted in detail so far. We have calculated them in thermal-neutron induced fission of 235U using the dynamical model, considering the Coulomb energy at the scission point and the prescission kinetic energy. The calculated results reproduce the experimental data. It is found that the pre-scission kinetic energy has about 5% contribution in the kinetic energy.

ReaxFF Molecular Dynamics Study on the Microscopic Mechanism for Kerogen Pyrolysis.

Kerogen is mainly composed of carbon, hydrogen, and oxygen, which are the main components of crude oil and gas. The pyrolysis of kerogen is an efficient method to generate clean energy. In the present work, the pyrolysis reaction process of three types of kerogen is simulated using ReaxFF molecular dynamics (MD) methods to study the microscopic mechanism and the distribution of products. The results indicated that the pyrolysis products of the three types of kerogen significantly depend on the molecular structures, temperature, and reaction time. As the temperature increases, the gaseous hydrocarbon and the light and heavy oil fractions decreased, where small molecular fragments polymerized to form new molecular fragments. For an isothermal temperature, with the reaction proceeding, some component polymerization of the pyrolyzed fragments occurred, resulting in the generation of new light oils and heavy oils. Moreover, quantum chemical analysis was employed to reveal the kerogen pyrolysis mechanism. First, the weak bonds such as C-O, C-N, and C-S structures were decomposed to generate large carbon and some heavy shale oil fragments. Second, the cycloalkanes and long-chain alkanes were decomposed to generate a large amount of light shale oil and gaseous hydrocarbons. Finally, the decomposition of C═C in the aromatic ring, the secondary decomposition of light and heavy shale oils, and the further decomposition of short-chain alkanes occurred. In addition, the production of hydrogen (H2) occurred at the late stage of the pyrolysis reaction. Hydrogen radicals were formed by the decomposition of C-H bonds and subsequently collided with each other, resulting in the formation of H2 molecules. The pyrolysis and chemical analysis of kerogen can clearly determine the type and content of hydrocarbon substances, providing scientific data for exploration, development, and utilization of shale gas and shale oil.

A novel sensitive DDoS attacks against statistical test in network traffic fusion

AbstractDistributed denial of service (DDoS) attacks are common attacks that limit casual users from cracking critical network resources. A method to find the DDoS attack comes to light as an essential and hot research issue. Therefore, the increment in network usage scale demands more challenges to see the DDoS attack. Non‐real‐time collection of network traffic will make sincere complications inaccuracy; DDoS attack detection, and efficiency. Lately, sketch data structures play an excellent role in high‐speed networks to suppress and combine network traffic issues. However, the sketch data structure has issues rebuilding the reverse keys that behave abnormally due to the reversible hash function. To rectify the above difficulties, we include the Chinese Remainder Theorem‐based Reverse Sketching (CRTRS). However, Reverse Sketching is not good at suppressing and combining heavy network traffic, but it can easily detect abnormal keys. According to the network traffic records setup by CRTRS, we add the Modified Cumulative Sum Quality Control Scheme (MCSQCS) that encourages DDoS attack detection. The enforcement of the proposed work with DDoS attack detection has two kind of different data sets. The result of the experiments shows that it gives more accuracy and efficiency in detecting DDoS attacks. Therefore, comparing other DDoS detecting methods with the sketch data structure has fewer computational complications. Improving the anomalous keys is the most critical challenge in this proposed work. To illustrate the accuracy rate, we experiment with a new technique called CIC‐Friday Heavy network traffic fragment. We also explain the experimental results of the MAWI heavy network fragment with the various parameter setups. To compare our proposed method with other similar existing methods, we use a sketch data structure to manage the network traffic data. It also uses the MSPCA method to detect the DDoS attack. The information‐based analysis helps to see the DDoS attack. The result analysis of True Positive Value (TPV) and False Positive Value (FPV) with MSPCA techniques has 79% and .1% accuracy. Similarly, information‐based detection has an accuracy of about 90% and 5%. Hence, the proposed method gives more accuracy for the detection of DDoS attacks.

Single domain Camelid antibody fragments for molecular imaging and therapy of cancer.

Despite innovations in cancer therapeutics, cancer remains associated with high mortality and is one of biggest health challenges worldwide. Therefore, developing precise cancer imaging and effective treatments is an unmet clinical need. A relatively novel type of therapeutics are heavy chain variable domain antibody fragments (VHHs) derived from llamas. Here, we explored the suitability of VHHs for cancer imaging and therapy through reviewing the existing literature. We searched the MEDLINE, EMBASE and Cochrane databases and identified 32 papers on molecular imaging and 41 papers on therapy that were suitable for comprehensive reviewing. We found that VHHs harbor a higher specificity and affinity compared to mAbs, which contributes to high-quality imaging and less side-effects on healthy cells. The employment of VHHs in cancer imaging showed remarkably shorter times between administration and imaging. Studies showed that 18F and 99mTc are two optimal radionuclides for imaging with VHHs and that site-specific labelling is the optimal conjugation modality for VHHs with radionuclide or fluorescent molecules. We found different solutions for reducing kidney retention and immunogenicity of VHHs. VHHs as anticancer therapeutics have been tested in photodynamic therapy, targeted radionuclide therapy, immunotherapy and molecular targeted therapy. These studies showed that VHHs target unique antigen epitopes, which are distinct from the ones recognized by mAbs. This advantage means that VHHs may be more effective for targeted anticancer therapy and can be combined with mAbs. We found that high cellular internalization and specificity of VHHs contributes to the effectiveness and safety of VHHs as anticancer therapeutics. Two clinical trials have confirmed that VHHs are effective and safe for cancer imaging and therapy. Together, VHHs seem to harbor several advantages compared to mAbs and show potential for application in personalized treatment for cancer patients. VHH-based imaging and therapy are promising options for improving outcomes of cancer patients.