However, the Californian, North African ( Atlas bear ), and Mexican subspecies were hunted to extinction in the 1870s, 1922, and more recently, respectively, and the not officially recognized Marsican brown bear in central Italy is believed to have a population of just 30 to 40 bears.

However, these populations are believed to be small, fragmented and vulnerable to extinction.

However, there is debate ongoing between groups that believe the evidence indicates substantial extinction of these species at the K – T boundary, and those who believe the evidence supports multiple extinctions and expansions through the boundary.

However, the use of data from coral fossils to support K – Pg extinction and subsequent Paleocene recovery must be weighed against the changes that occurred in coral ecosystems through the K – T boundary.

However, the marine and freshwater environments of fishes mitigated environmental effects of the extinction event.

However, during the early Paleocene, flora were relatively diverse with little predation from insects, even 1. 7 million years after the extinction event.

However research concludes that this change would have been insufficient to cause the observed level of ammonite extinction.

However, the current consensus among the scientific community is that the extinction was triggered by the Chicxulub impact event in Central America ( which would have produced a sunlight-blocking dust cloud that killed much of the plant life and reduced global temperature, called an impact winter ).

However, opponents of " late extinction " theories have interpreted such late dates based on indirect dating methods as artifacts resulting from redeposition of skeletal material into more recent strata, and recent direct dating results obtained with new technologies have tended to confirm this interpretation.

However, statistical analysis shows that this can only account for 50 % of the observed pattern, and other evidence ( such as fungal spikes ) provides reassurance that most widely accepted extinction events are indeed real.

However, the end of the period did not witness any major extinction event.

However, this hypothesis is not widely accepted due to lack of evidence for any other animal decline or extinction, even in environmentally sensitive species.

However, a study of uranium / lead ratios of zircons from rock sequences in multiple locations in southern China date the extinction to 252. 28 ± 0. 08 Ma ; an earlier study of rock sequences near Meishan in Changxing County of Zhejiang Province, China date the extinction to 251. 4 ± 0. 3 Ma, with an ongoing elevated extinction rate occurring for some time thereafter.

However, the quasispecies model does not predict the ultimate extinction of all but the fastest replicating sequence.

However, organisms and ecosystems, as far as it can be determined by the fossil record, do not appear to have undergone the significant change that would be expected by a mass extinction.

However, the Spanish Civil War brought a decline of the genre, and after the war, its extinction as a live genre was almost total.

However, in other locations such as Australia, humans are thought to have played a very significant role in the extinction of the Australian megafauna that was widespread prior to human occupation.

However, they were never used, as after a time, leaders on both sides of the Iron Curtain realized that global thermonuclear war would not be in either power's interest, as it would probably lead to the destruction of both sides, and possibly nuclear winter or other extinction level events.

However, simulation studies give a 70 percent probability that the crater was created by a fragment from the same break-up that created asteroid 298 Baptistina ; which was previously believed to be responsible for the formation of Chicxulub Crater and the extinction of the dinosaurs.

However, in 2010, Melott & Bambach found strong evidence in the fossil record confirming the extinction event periodicity originally claimed by Raup & Sepkoski in 1984, but at a higher confidence level and over a time period nearly twice as long.

However the contemporaneous introduction of the shotgun was thought to have resulted in the extinction of the species.

However, the increasing interest in the topic of mass extinction starting in the late 20th century has led to a resurgence of interest among historians of science and other scholars in this aspect of Cuvier's work.

However practical devices have a limit to the peak current they can pass, and the pulse must therefore be widened, to around 120 degrees, to obtain a reasonable amount of power, and the efficiency is then 60-70 %.

However, he uses his nuclear pulse, knocking her out.

However, the G-M tube produces a pulse output which is the same magnitude for all detected radiation, so a Geiger counter with an end window tube cannot distinguish between alpha and beta particles.

However, the popular description of light being " stopped " in these experiments refers only to light being stored in the excited states of atoms, then re-emitted at an arbitrary later time, as stimulated by a second laser pulse.

However, Natasha uses her uncle's hammer to trigger an electromagnetic pulse which shuts down the synthetic metagene long enough for Steel to knock Lex unconscious.

However, the intense pulse of high-energy neutrons that is generated is intended as the principal killing mechanism, not the fallout, heat or blast.

However optical pulse width and signal integration time are user adjustable, and require trade-offs which make them application specific.

However, those systems that use pulse code modulation generally induce more lag due to lesser frames sent per second as bandwidth is needed for error checking bits.

However, very few of these major works lack new technical ideas — simple examples being the introduction of communicable language in Meditations, the invention of a new percussion instrument ( the geophone ) for Des canyons aux etoiles ..., and the freedom from any synchronisation with the main pulse of individual parts in certain birdsong episodes of St. François d ' Assise.

However, Q-switched lasers can also be used for measurement purposes, such as for distance measurements ( range finding ) by measuring the time it takes for the pulse to get to some target and the reflected light to get back to the sender.

However, newer 4th-and 5th-generation nuclear weapons designs including pure fusion weapons and antimatter catalyzed nuclear pulse propulsion-like devices are being studied extensively by the 5 largest nuclear weapon states.

However, the minimum pulse duration is limited by the period of the carrier frequency ( which is about 2. 7 fs for Ti: S systems ), therefore shorter pulses require moving to shorter wavelengths.

However, the amount of overclocking is limited by the time for the CPU to settle after each pulse, and by the extra heat created.

However, within a fraction of a second the dense shock front obscures the fireball, causing the characteristic double pulse of light seen from a nuclear detonation.

However, it was the phase of the received signals within each pulse that was used to determine the transit time from transmitter to receiver.

However, flash is re-written using a large pulse of voltage ( about 10 V ) that is stored up over time in a charge pump, which is both power-hungry and time-consuming.

However, these and other studies do not provide any valid evidence that such a craniosacral ' rhythm ' or ' pulse ' can be reliably perceived by an examiner ".

However, for an aircraft flying through the never-uniform and never-quiescent atmosphere, the relating of pulse transmission and reception times to successive geometric positions of the antenna must be accompanied by constant adjusting of the return phases to account for sensed irregularities in the flight path.

However, in practice this particular feature of pulse oximeters may not be widely utilized by medical professionals because of the risk of too many audio stimuli in medical environments.

However, Electro, the Vulture and Mysterio were all taken out before Electro could trigger the pulse thanks to the efforts of Spider-Man and S. A. F. E., Doctor Octopus and the Chameleon both attempted to betray the Gentleman and take control of his plan, and Pity was convinced to help Spider-Man defeat her two former teammates when he informed her that the currently-missing Doctor Octopus had always hated not being in charge and had almost certainly left the fight to go after the Gentleman.

However, the former usually refers to measurement of a pulse on a limb, while the latter refers to measurement of the pulse of the carotid artery.

However, the use of a pulse oximeter to detect hypoventilation is impaired with the use of supplemental oxygen, as it is only when patients breathe room air that abnormalities in respiratory function can be detected reliably with its use.

However as the atom will not absorb a light pulse of any arbitrary frequency ν but only a frequency that corresponds to one of the allowed transitions, in this respect the atom is choosy, and therefore selective.