Crossover Distance Research Articles

Electron Tunneling in Biology: When Does it Matter?

Electrons can tunnel between cofactor molecules positioned along biological electron transport chains up to a distance of ≃ 20 Å on the millisecond time scale of enzymatic turnover. This tunneling range determines the design of biological energy chains facilitating the cross-membrane transport of electrons. Tunneling distance and cofactors' redox potentials become the main physical parameters affecting the rate of electron transport. In addition, universal charge-transport properties are assigned to all proteins, making protein identity, flexibility, and dynamics insignificant. This paradigm is challenged by dynamical models of electron transfer, showing that the electron hopping rate is constant within the crossover distance R* ≃ 12 Å, followed with an exponential falloff at longer distances. If this hypothesis is fully confirmed, natural and man-made energy chains for electron transport should be best designed by placing redox cofactors near the crossover distance R*. Protein flexibility and dynamics affect the magnitude of the maximum hopping rate within the crossover distance. Changes in protein flexibility between forward and backward transitions contribute to vectorial charge transport. For biological energy chains, charge transport through proteins is not defined by universal parameters, and protein identity matters.

Theory of Protein Charge Transfer: Electron Transfer between Tryptophan Residue and Active Site of Azurin.

One reaction step in the conductivity relay of azurin, electron transfer between the Cu-based active site and the tryptophan residue, is studied theoretically and by classical molecular dynamics simulations. Oxidation of tryptophan results in electrowetting of this residue. This structural change makes the free energy surfaces of electron transfer nonparabolic as described by the Q-model of electron transfer. We analyze the medium dynamical effect on protein electron transfer produced by coupled Stokes-shift dynamics and the dynamics of the donor-acceptor distance modulating electron tunneling. The equilibrium donor-acceptor distance falls in the plateau region of the rate constant, where it is determined by the protein-water dynamics, and the probability of electron tunneling does not affect the rate. The crossover distance found here puts most intraprotein electron-transfer reactions under the umbrella of dynamical control. The crossover between the medium-controlled and tunneling-controlled kinetics is combined with the effect of the protein-water medium on the activation barrier to formulate principles of tunability of protein-based charge-transfer chains. The main principle in optimizing the activation barrier is the departure from the Gaussian-Gibbsian statistics of fluctuations promoting activated transitions. This is achieved either by incomplete (nonergodic) sampling, breaking the link between the Stokes-shift and variance reorganization energies, or through wetting-induced structural changes of the enzyme's active site.

When to Crossover From Earth to Space for Lower Latency Data Communications?

For data communications over long distances, optical wireless satellite networks (OWSNs) can offer lower latency than optical fiber terrestrial networks (OFTNs). However, when is it beneficial to switch or crossover from an OFTN to an OWSN for lower latency data communications? In this article, we introduce a crossover function that enables to find the crossover distance, i.e., a distance between two points on the surface of the Earth beyond which switching or crossing over from an OFTN to an OWSN for data communications between these points is useful in terms of latency. Numerical results reveal that a higher refractive index of optical fiber (or $i$) in an OFTN and a lower altitude of satellites (or $h$) in an OWSN result in a shorter crossover distance. To account for the variation in the end-to-end propagation distance that occurs over the OWSN, we examine the crossover function in four different scenarios. Numerical results indicate that the crossover distance varies with the end-to-end propagation distance over an OWSN and is different for different scenarios. We calculate the average crossover distance over all scenarios for different $h$ and $i$ and use it to evaluate the simulation results. Furthermore, for a comparative analysis of OFTNs and OWSNs in terms of latency, we study three different OFTNs having different refractive indexes and three different OWSNs having different satellite altitudes in three different scenarios for long-distance intercontinental data communications, including connections between New York and Dublin, Sao Paulo and London, and Toronto and Sydney. All three OWSNs offer better latency than OFTN2 (with $i_{2}$ = 1.3) and OFTN3 (with $i_{3}$ = 1.4675) in all scenarios. For example, for Toronto–Sydney connection, OWSN1 (with $h_{1}$ = 300 km), OWSN2 (with $h_{2}$ = 550 km), and OWSN3 (with $h_{3}$ = 1100 km) perform better than OFTN2 by 18.11%, 16.08%, and 10.30%, respectively, while they provide an improvement in latency of 27.46%, 25.67%, and 20.54%, respectively, compared to OFTN3. OWSN1 performs better than OFTN1 (with $i_{1}$ = 1.1) for Sao Paulo–London and Toronto–Sydney connections by 2.23% and 3.22%, respectively, while OWSN2 outperforms OFTN1 for Toronto–Sydney connection by 0.82%. For New York–Dublin connection, all OWSNs while for Sao Paulo–London connection, OWSN2 and OWSN3 exhibit higher latency than OFTN1 as the corresponding average crossover distances are greater than the shortest terrestrial distances between cities in these scenarios. Multiple satellites (or laser intersatellite links) on its shortest paths drive up the propagation distance to the extent that OWSN3 ends up with a higher latency than OFTN1 for the Toronto–Sydney intercontinental connection scenario although the related average crossover distance is less than the shortest terrestrial distance between Toronto and Sydney. The challenges related to OWSNs and OFTNs that may arise from this work in future are also highlighted.

Conformational dynamics modulating electron transfer.

Diffusional dynamics of the donor-acceptor distance are responsible for the appearance of a new time scale of diffusion over the distance of electronic tunneling in electron-transfer reactions. The distance dynamics compete with the medium polarization dynamics in the dynamics-controlled electron-transfer kinetics. The pre-exponential factor of the electron-transfer rate constant switches, at the crossover distance, between a distance-independent, dynamics-controlled plateau and exponential distance decay. The crossover between two regimes is controlled by an effective relaxation time slowed down by a factor exponentially depending on the variance of the donor-acceptor displacement. Flexible donor-acceptor complexes must show a greater tendency for dynamics-controlled electron transfer. Energy chains based on electron transport are best designed by placing the redox cofactors near the crossover distance.

Semantics in Multi-objective Genetic Programming

Semantics has become a key topic of research in Genetic Programming (GP). Semantics refers to the outputs (behaviour) of a GP individual when this is run on a dataset. The majority of works that focus on semantic diversity in single-objective GP indicates that it is highly beneficial in evolutionary search. Surprisingly, there is minuscule research conducted in semantics in Multi-objective GP (MOGP). In this work we make a leap beyond our understanding of semantics in MOGP and propose SDO: Semantic-based Distance as an additional criteriOn. This naturally encourages semantic diversity in MOGP. To do so, we find a pivot in the less dense region of the first Pareto front (most promising front). This is then used to compute a distance between the pivot and every individual in the population. The resulting distance is then used as an additional criterion to be optimised to favour semantic diversity. We also use two other semantic-based methods as baselines, called Semantic Similarity-based Crossover and Semantic-based Crowding Distance. Furthermore, we also use the Non-dominated Sorting Genetic Algorithm II and the Strength Pareto Evolutionary Algorithm 2 for comparison too. We use highly unbalanced binary classification problems and consistently show how our proposed SDO approach produces more non-dominated solutions and better diversity, leading to better statistically significant results, using the hypervolume results as evaluation measure, compared to the rest of the other four methods.

Gaussian process models of potential energy surfaces with boundary optimization.

A strategy is outlined to reduce the number of training points required to model intermolecular potentials using Gaussian processes, without reducing accuracy. An asymptotic function is used at a long range, and the crossover distance between this model and the Gaussian process is learnt from the training data. The results are presented for different implementations of this procedure, known as boundary optimization, across the following dimer systems: CO-Ne, HF-Ne, HF-Na+, CO2-Ne, and (CO2)2. The technique reduces the number of training points, at fixed accuracy, by up to ∼49%, compared to our previous work based on a sequential learning technique. The approach is readily transferable to other statistical methods of prediction or modeling problems.

Wireless Communication Technologies in Omnidirectional CubeSat Crosslink: Feasibility Study and Performance Analysis

An efficient omnidirectional CubeSat data crosslink is imperative to ensure the success of resource-intensive advanced CubeSat missions. In this article, we present a feasibility study of wireless technologies in high-speed CubeSat crosslink design. We study the power consumption, pointing requirement, and antenna requirement of each technology to implement an omnidirectional communicator. We also investigate the performance limit of the state-of-the-art wireless technologies considering the realizable link parameters. The achievable data rate and communication distance are studied thoroughly for different communication systems. The analyses show that an optical communication link is capable of delivering more than two orders of magnitude higher data throughput than that of microwave links in an omnidirectional platform. However, the study shows that due to the size and power restriction, a performance crossover region exists where the performance of a microwave channel exceeds the performance of the optical channel. The crossover distance and crossover data rate are studied thoroughly with different system configurations and modulation formats to assess the maximum reach of wireless technologies in a CubeSat crosslink.

Impairments-aware time slot allocation model for energy-constrained multi-hop clustered IoT nodes considering TDMA and DSSS MAC protocols

The possibility of Internet of Things (IoT) is that a large number of live items (e.g., apparatuses) in the network are available, detected, and interconnected. In any case, the performance of IoT networks may be limited due to several impairments, most importantly, the energy-constrained IoT nodes. In fact, this limitation opens the door to many researchers where using network clustering has proven to be efficient energy saving mechanism. To the best of our knowledge, there are no prior research, in the field of multi-hop clustered IoT networks, which addressed the energy-constrained IoT nodes problem along with the delay in receiving data messages from devices, located far away from the remote users (or control center), in timely basis. Practically, it is significantly challenging to contemplate and clarify this issue. Consequently, in this paper, we make major amendments on the prior work, Improved Energy and Distance Based CH Selection with Balanced Objective Function (IEDB-CHS-BOF), and particularly propose a multi-hop routing (MR) protocol in which the IoT network is divided into a number of virtual sections with lengths held below the cross-over communication distance, thereby ensuring minimal energy depletion. Over those virtual sections, efficient forwarder and cluster head selection algorithms are further proposed. Interestingly, we propose a novel delay-, power-, and interference-aware time slot allocation model in which Time Division Multiple Access (TDMA) and Direct Sequence Spread Spectrum (DSSS) MAC protocols are operated. Furthermore, it is a good representation of the above-mentioned proposals. As a result, our protocols are referred to as MR-IEDB-CHS-TDMA and MR-IEDB-CHS-DSSS, respectively. To this end, numerous simulations have been conducted for evaluating the performance of the proposed protocols in the perspective of IoT network lifetime. In addition, sufficient comparisons have been conducted with the existing state-of-the-art protocols. In overall, the MR-IEDB-CHS-TDMA protocol keeps the IoT network functioning the longest.

Spectral models for seismological source parameters, path attenuation and site-effects in Alborz region of northern Iran

SUMMARYWe analysed 478 three-component strong ground motion time-series from 65 events in the moment magnitude (Mw) 3–6.5 range recorded at 111 stations at distances up to 150 km from 1997 to 2019 in the Alborz region. Non-parametric spectral functions for seismological source, path and site-effects were derived from Fourier amplitude spectra of observed acceleration time-histories using the generalized inversion technique (GIT) for the Alborz region of Iran. To characterize the spectral models in terms of the anelastic attenuation (Q), geometrical spreading, magnitude and stress parameter (Δσ), we fitted non-parametric attenuation and source functions (resulted from inversion) with the standard parametric models. The frequency-dependent non-parametric attenuation function shows a rapid decay at close distances (<60 km) and decreases monotonically at larger distances. The frequency-independent geometrical spreading follows a bilinear hinged model with a crossover distance at 70 km. For hypocentral distances Rhypo < 70 km, the geometrical spreading is ${R^{ - 1.01}}$, and for Rhypo > 70 km it is ${R^{ - 1.37}}$. The corresponding quality factor is $Q\ ( f ) = \ 146{f^{0.91}}$. The non-parametric source spectra were found in a good agreement with Brune's ω-squared model. The stress-parameter (Δσ) values were found to exhibit large variability from 0.36 to 86.7 MPa with no significant magnitude-dependence. The average Δσ was found to be 8.6 MPa. The mean value of the estimated near-surface attenuation (κ0) from high-frequency part of non-parametric source function is 0.032 s (±0.01 s). In general, there is a good agreement between subsoil resonance frequencies and amplification levels estimated from GIT and HVSR (horizontal to vertical spectral ratio). The results of this study provide updated values of seismological source, attenuation and site properties in the Alborz region of northern Iran, which are expected to improve regional seismic hazard analysis studies in the region.

Comparison of AA Amyloid Fibril Morphology and Serum Amyloid A Gene Sequence in 5 Animal Species.

Amyloid fibrils are characterized by a linear morphology and a cross-β structure. Polymorphic and multiple fibril morphologies can be found when amyloid fibrils are extracted from amyloid-laden tissue. In this study, we report on the purification and transmission electron microscopic analysis of amyloid fibrils from 5 different animal species (mouse, cow, goat, dog, and camel) with AA amyloidosis. The results show that amyloid fibrils had a linear morphology with a cross-structure and irregular length in vivo. Although the fibrils from these different species showed highly similar conformations, there were significant differences in fibril width and crossover distance. We analyzed the sequences of homologous amyloid proteins and serum amyloid A, an evolutionarily conserved protein and a major amyloid precursor. We found 78.23% homology between the most distant amyloid proteins. The findings suggested similar fibril width and crossover distance in different animal species that displayed high homology of amyloid protein sequences. Dog and camel, as well as goat and cow, showed high genetic homology and similar fibril morphology. These data indicate that the fibrils from different animal species have similar genetic homology and morphology, which may provide a better understanding of the pathogenesis of amyloidosis.

Finite-key analysis for memory-assisted decoy-state quantum key distribution

Memory-assisted quantum key distribution (MA-QKD) systems are among novel promising solutions that can improve the key-rate scaling with channel loss. By using a middle node with quantum storage and measurement functionalities, they offer the same key-rate scaling with distance as a single-node quantum repeater. However, the distance at which they can surpass the nominal key rate of repeaterless systems, in terms of bits per second, is typically long, owing to the efficiency and/or interaction time issues when one deals with quantum memories. This crossover distance can be a few hundred kilometres, for instance, when one relies on the exchange of infinitely many key bits for the key-rate analysis. In a realistic setup, however, we should account for the finite-key effects in our analysis. Here, we show that accounting for such effects would actually favour MA-QKD setups, by reducing the crossover distance to the regime where realistic implementations can take place. We demonstrate this by rigorously analysing a decoy-state version of MA-QKD, in the finite-key regime, using memory parameters already achievable experimentally. This provides us with a better understanding of the advantages and challenges of working with memory-based systems.

Strong zero-field Förster resonances in K-Rb Rydberg systems

We study resonant dipole-dipole coupling and the associated van der Waals energy shifts in Rydberg excited atomic rubidium and potassium and investigate F\"orster resonances between interspecies pair states. A comprehensive survey over experimentally accessible pair state combinations reveals multiple candidates with small F\"orster defects. We crucially identify the existence of an ultrastrong, "low" electric field K-Rb F\"orster resonance with a extremely large zero-field crossover distance exceeding 100 $\mu$m between the van der Waals regime and the resonant regime. This resonance allows for a strong interaction over a wide range of distances and by investigating its dependence on the strength and orientation of external fields we show this to be largely isotropic. As a result, the resonance offers a highly favorable setting for studying long-range resonant excitation transfer and entanglement generation between atomic ensembles in a flexible geometry. The two-species K-Rb system establishes a unique way of realizing a Rydberg single-photon optical transistor with a high-input photon rate and we specifically investigate an experimental scheme with two separate ensembles.

Unexpected Cholesterol-Induced Destabilization of Lipid Membranes near Transmembrane Carbon Nanotubes

Cholesterol is a crucial component of mammalian cell membranes that takes part in many vital processes. It is generally accepted that cholesterol stabilizes the membrane and induces transitions into ordered states. In contrast to expectations, we demonstrate that cholesterol can destabilize the membrane by creating a nanodomain around a perpendicularly embedded ultrashort carbon nanotube (CNT), and we show that cholesterol triggers the translocation of an ultrashort CNT through the cell membrane. Using atomistic simulations, we report the existence of a nanoscale domain around an ultrashort carbon nanotube within a crossover distance of 0.9nm from the surface of the nanotube, where the properties of the bilayer are different from the bulk: the domain is characterized by increased fluctuations, increased thickness, and increased order of the lipids with respect to the bulk. Cholesterol decreases the thickness and order of lipids and increases the fluctuations with respect to a pure lipid bilayer. Experimentally, we confirm that cholesterol nanodomains provoke spontaneous translocation of nanotubes through a lipid bilayer even for low membrane tensions. A specially designed microfluidic device allows us to trace the kinetic pathway of the translocation process and establish the threshold cholesterol concentration of 20% for translocation. The reported nanoscale cholesterol-induced membrane restructuring near the ultrashort CNT in lipid membranes enables precise control and specific targeting of a membrane using cholesterol. As an example, it may allow for specific targeting between cholesterol-rich mammalian cells and cholesterol-poor bacterial cells.

Discovery of new microscopic structures in surface water on graphene using data science

We present the first-ever application of a statistical data analysis technique based on a persistent homology method combined with molecular dynamics simulations to determine the microscopic structure of water on graphene. This work assessed the rapid transition in the water structure on going from surface water to free water with increasing distance from the graphene surface, which is one of the most fundamental issues to be resolved in the field of water research. The crossover distance was unexpectedly short at approximately 1 nm, equivalent to three water layers. Within this 1 nm thick layer of surface water, the rotational freedom of tetrahedral water clusters was almost zero due to the presence of the graphene surface. Thus, water on hydrophobic surfaces such as graphene was found to contain a newly-discovered type of water cluster.

Design and Characterization of RNA Nanotubes.

RNA is a functionally rich and diverse biomaterial responsible for regulating several cellular processes. This functionality has been harnessed to build predominately small nanoscale structures for drug delivery and the treatment of disease. The understanding of design principles to build large RNA structures will allow for further control of stoichiometry and spatial arrangement drugs and ligands. We present the design and characterization of RNA nanotubes that self-assemble from programmable monomers, or tiles, formed by five distinct RNA strands. Tiles include double crossover junctions and assemble via single-stranded sticky-end domains. We find that nanotube formation is dependent on the intertile crossover distance. The average length observed for the annealed RNA nanotubes is ≈1.5 μm, with many nanotubes exceeding 10 μm, enabling the characterization of RNA nanotubes length distribution via fluorescence microscopy. Assembled tubes were observed to be stable for more than 24 h, however post-annealing growth under isothermal conditions does not occur. Nanotubes assemble also from RNA tiles modified to include a single-stranded overhang (toehold), suggesting that it may be possible to decorate these large RNA scaffolds with nanoparticles or other nucleic acid molecules.

Strong suppression of near-field radiative heat transfer by superconductivity in NbN

Near-field (NF) radiative heat transfer (RHT) over vacuum space between closely spaced bodies can exceed the Planck far-field (FF) values by orders of magnitude. Strong effect of superconductivity on NF RHT between plane-parallel thin-film surfaces of niobium (Nb) was recently discovered and discussed in a short paper [Kr\'al\'ik et al., Phys. Rev. B 95, 060503 (2017)]. We present here an extensive set of experimental results on NF as well as FF RHT for geometrically identical samples made of niobium nitride (NbN), including a detailed discussion of the experimental setup and errors. The results with NbN show more precise agreement with theory than the original experiments with Nb. We observed a steep decrease of the heat flux at the transition to superconductivity when the colder sample (absorber) passed from normal to superconducting (SC) state ($T_c \approx 15.2$ K), corresponding to up to an 8-fold contrast between the normal and SC states. This differs dramatically from the situation in the FF regime, where only a weak effect of superconductivity was observed. Surprisingly, the contrast remains sizeable even at high temperatures of the hot sample (radiator) with the characteristic energy of radiation far above the SC energy gap. We explain the maximum of contrast in heat flux between the normal and SC states, found at a distance about ten times shorter than the crossover distance between NF and FF heat flux, being $d \approx 1000/T$ [${\mu}$m]. We analyze in detail the roles of transversal electric (TE) and magnetic (TM) modes in the steep decrease of heat flux below the SC critical temperature and the subsequent flux saturation at low temperatures. Interestingly, we expose experimentally for the first time the effect of destructive interference of FF thermal radiation in the vacuum gap, which was observable at temperatures below the absorber superconducting transition.

A distance between populations for n-points crossover in genetic algorithms

Abstract The theoretical study of Genetic Algorithms and the dynamics induced by their genetic operators is a research field with a long history and many different approaches. In this paper we complete a recently presented approach to model one-point crossover using pretopologies (or Cechtopologies) in two ways. First, we extend it to the case of n-points crossover. We extend the definition of crossover distance between populations to work for n-points crossover, proving that computing it can be performed in polynomial time for any fixed number of crossover points. Secondly, we experimentally study how the distance distribution changes when the number of crossover points increases. In particular, the average distance between a population and the optimum decreases with the increase in the number of crossover points, showing that increasing the latter can reduce the number of crossover operations needed to evolve an optimal solution.

A Frequency-Dependent Regularization for Autocalibrating Parallel MRI Using the Generalized Discrepancy Principle

This paper quantitatively evaluates regularized GRAPPA SPIRiT reconstruction in autocalibrating parallel MRI and develops a frequency-dependent regularization (FDR) aimed at achieving higher SNR with reduced penalty on image resolution. The latter is achieved by imposing an upper limit on the extent of regularization for each k -space location. The procedure starts with selection of a suitable truncation parameter, followed by perturbation of the AutoCalibrating Signal (ACS) lines using addition of white Gaussian noise samples of a predetermined variance. The noise variance chosen is such that first-order perturbation rules apply. In each perturbation step, the regularized solutions are estimated using a first-order update of singular values, and conditions stipulated by the generalized discrepancy principle (GDP) with regards to the norms of calibration and perturbation errors. The procedure is stopped at the crossover limit, once the GDP conditions are violated. The crossover information yields an upper limit for perturbation, enabling computation of an error bound as the difference between k -spaces estimated with filter weights from calibrations performed on original and the perturbed ACS lines at cross-over. Imposition of an upper limit on the extent of regularization is achieved by matching this error bound to the difference in k -spaces reconstructed with varying offsets of regularization from that of a reference. Furthermore, the crossover distance defined in terms of difference between minimum singular values of the initial and crossover calibration matrices serves as a proxy indicator of the achievable reduction in reconstruction error using regularization.

Why Will Computing Power Need Particular Attention in Future Wireless Devices?

In this tutorial particular attention is given to the computing power in the physical layer of wireless devices, which are energy and power limited. Communication uses the power in the analog radio frequency parts and computation uses power in the signal processing and other tasks required during communication, both in the transmitter and in the receiver. Example applications include sensor networks and mobile devices in ultra-dense small cell networks where the link distances are below about 10 m, and the computing power is larger than the communication power. The computation-communication tradeoff means that if one of the powers is increased, the other one must be decreased, otherwise the total power increases. Energy efficiency is a challenging multidisciplinary topic, and the consequences of the interrelated fundamental limits are not well understood. According to Edholm?s prediction, the link bit rates are increasing exponentially each year, which implies that there must be a corresponding exponential trend in improving energy efficiency, defined as number of bits per energy unit, both in computation and communication. It is well known that for communications, due to noise, the Shannon limit forms the fundamental limit for the received energy per bit, but in computation there is a similar limit called Landauer limit for the switching energy of a transistor. Near the two fundamental limits the energy efficiency cannot be improved any more exponentially. Our main contribution is to elaborate the connections between the various technology predictions, different fundamental limits and possible design trade-offs. Specifically, we show that because of the aforementioned fundamental limits, the exponential trends in bit rates cannot continue without a compensating exponential trend in energy efficiency. We also revisit the concept of crossover distance and derive it from the fundamental limits to give some further system-level insight on the energy consumption bottlenecks.

Altered Crossover Distribution and Frequency in Spermatocytes of Infertile Men with Azoospermia.

During meiosis, homologous chromosomes pair to facilitate the exchange of DNA at crossover sites along the chromosomes. The frequency and distribution of crossover formation are tightly regulated to ensure the proper progression of meiosis. Using immunofluorescence techniques, our group and others have studied the meiotic proteins in spermatocytes of infertile men, showing that this population displays a reduced frequency of crossovers compared to fertile men. An insufficient number of crossovers is thought to promote chromosome missegregation, in which case the faulty cell may face meiotic arrest or contribute to the production of aneuploid sperm. Increasing evidence in model organisms has suggested that the distribution of crossovers may also be important for proper chromosome segregation. In normal males, crossovers are shown to be rare near centromeres and telomeres, while frequent in subtelomeric regions. Our study aims to characterize the crossover distribution in infertile men with non-obstructive (NOA) and obstructive azoospermia (OA) along chromosomes 13, 18 and 21. Eight of the 16 NOA men and five of the 21 OA men in our study displayed reduced crossover frequency compared to control fertile men. Seven NOA men and nine OA men showed altered crossover distributions on at least one of the chromosome arms studied compared to controls. We found that although both NOA and OA men displayed altered crossover distributions, NOA men may be at a higher risk of suffering both altered crossover frequencies and distributions compared to OA men. Our data also suggests that infertile men display an increase in crossover formation in regions where they are normally inhibited, specifically near centromeres and telomeres. Finally, we demonstrated a decrease in crossovers near subtelomeres, as well as increased average crossover distance to telomeres in infertile men. As telomere-guided mechanisms are speculated to play a role in crossover formation in subtelomeres, future studies linking crossover distribution with telomere integrity and sperm aneuploidy may provide new insight into the mechanisms underlying male infertility.